text:
Hazrat Mirza Masroor Ahmad
Governing Principle of the Fear of Allah
An address delivered by Hazrat Mirza Masroor Ahmad (may Allah be his Helper), on the occasion of Majlis-e-Shura UK 2019.
The 'Majlis-e-Shura' is a consultative body within the Ahmadiyya Muslim Community, where members discuss recommendations for moral and spiritual betterment. We present the official transcript of the address by the Worldwide Head of the Ahmadiyya Muslim Community at the concluding session of the 40th Majlis-e-Shura UK 2019.
After reciting Tashahhud, Ta'awwuz and Surah Al-Fatihah, Hazrat Khailfatul Masih V(aba) said:
"With the Grace of Allah, the National Majlis-e-Shura of the UK Jama'at is now reaching its conclusion. I am confident that all of you will, according to your individual capacities, have taken a full part in the proceedings of the Shura.
Initially the agenda is prepared for the Shura, then sub-committees are formed and these items of the agenda are then discussed in the sub-committee. Then, after having discussed those items in the subcommittee a report is prepared and presented before the full house. Further discussion has taken place and I hope some of you will have given your opinions and recommendations in light of the sub-committees findings.
I am confident that every one of you, according to your abilities, will have given your suggestions and cast your votes with integrity and, certainly, this is what is expected of a Momin (a true believer). Now, in this concluding session, I will elaborate upon the responsibilities and duties of a Shura member, in light of a speech given by Hazrat Musleh Maud(ra), on the occasion of one of his Majlis-e-Shura.
Above all else, Hazrat Musleh Maud[i](ra) instructed that Shura members must inculcate within themselves خَشِیَّۃُ اللّٰہ – the 'fear of Allah the Almighty'. Hazrat Musleh Maud(ra) said that a person's speech and oratory, no matter how eloquent or well-spoken they may be, would not prove to be their means of success in this life or the next. Rather the key to success and victory in this life and in the Hereafter is to proclaim رَبُّنَا اللہ– that 'Our Lord is Allah' – and to live one's life according to this paramount principle.
Certainly, we must develop within ourselves the spirit of:
رَبَّنَاۤ اِنَّنَا سَمِعۡنَا مُنَادِیًا یُّنَادِیۡ لِلۡاِیۡمَانِ اَنۡ اٰمِنُوۡا بِرَبِّکُمۡ فَاٰمَنَّا ٭ۖ رَبَّنَا فَاغۡفِرۡ لَنَا ذُنُوۡبَنَا وَ کَفِّرۡ عَنَّا سَیِّاٰتِنَا وَ تَوَفَّنَا مَعَ الۡاَبۡرَارِ
"Our Lord, we have heard a Crier calling us unto faith, 'Believe ye in your Lord,' and we have believed. Our Lord, forgive us, therefore, our errors and remove from us our evils, and in death number us with the righteous." (Chapter 3, Verse 194)
If we, Ahmadi Muslims, are not endeavouring to live our lives in this way and do not strive towards righteousness, then ask yourselves what is our worth and status in comparison to the major powers and nations of the world?
Even today, when our Jama'at has millions of members across the world, the truth remains that we represent a very small proportion of the world's Muslims and, compared to the overall population of the world, our Jama'at's numbers are a mere drop in the ocean. If our Jama'at is viewed through the lens of materialism, it must be said that we are entirely insignificant. Indeed, if you look at the numbers of our Jama'at in purely material terms it can be said that our status is not even that of an insect or a speck of dust.
However, there is one thing that sets us apart and in which we can take great pride and that is that we have heard the cry of the Caller of this era and upon hearing it we have proclaimed that 'we listen and we obey' and have entered his blessed fold.
This is our foundation.
This is our identity.
This is our true value.
And so this great blessing should remain at the forefront of our minds and embedded in our hearts at all times. As members of the Community of the Promised Messiah(as), the Fear of Allah should take priority and precedence over all of our thoughts and reflections. Our views, opinions and beliefs should all be rooted in the fear of Allah the Almighty. Hence, if we are given the opportunity to present our experiences or views we must ensure that the fear of Allah consumes every fibre of our beings as we speak.
The fear of Allah should control our tongues.
The fear of Allah should rule our hearts.
The fear of Allah should govern our every suggestion and statement.
As Shura members, you must keep in mind that you have been called to give your honest opinion for the sake of the religion of Allah the Almighty. Therefore, every recommendation you make, no matter how big or small, should be based on the fear of Allah. Every comment or view must be entirely truthful and devoid of all forms of self-interest.
Furthermore, all of us must continuously value, cherish and protect that unique element which enables us to stand with pride before the world and which compels even the worldly powers and materialistic people to recognise our strength and value. Certainly, if in the world today others respect us and perceive our true significance it is only due to the fact that they can see that we are a united community who stand together at all times, in all circumstances, at the hand of Khalifatul Masih[ii]. They appreciate the fact that we are the ones who are earnestly striving to spread the true teachings of Islam, which are of peace, love and humanity, across the world.
We are the ones who are propagating that Islam which was practiced and preached by the Holy Prophet of Islam(sa). This is the reason that scores of good natured and intelligent people, both Muslims and non-Muslims, are being drawn towards our Jama'at each year. Consequently, all Shura members bear a heavy burden of responsibility and must always keep in mind that their suggestions, their service to the Jama'at and their means of taking service from others, must be entirely devoid of personal interest, ego and self-regard.
A deeply profound and precious point made by Hazrat Musleh Maud(ra) was that even if a person makes a wrong decision, it will not ultimately prove an obstruction in the progress and success of the Jama'at, so long as it was made with the best of intentions and with the fear of Allah in his heart. Conversely, if a person makes a correct decision but does so without the fear of Allah and without seeking His nearness, then, despite being right, it will not prove a means of success and instead will lead to harm. Thus, if we make a decision without the fear of Allah embedded in our hearts, even if it is correct, eventually other factors will emerge which will negate the effectiveness of our decision and prove detrimental.
However, if we make an error of judgement, whilst retaining the fear of Allah in our hearts, then the rectification of that mistake will be made by Allah the Almighty Himself. Through His Grace and Mercy, He will protect us from any harm and enable us to walk upon a path that leads us towards success and security. Some people may query this logic and ask how a wrong decision can lead to prosperity, whilst a correct decision can lead to harm? This is a worldly way of thinking and, in answer to this question, Hazrat Musleh Maud(ra) cited an incident from the life of the Holy Prophet(sa) in which the Holy Prophet(sa) saw in a dream that he was performing the Tawaaf of Khaana Kaabah.
In order to fulfill the dream and to attain the blessings and pleasure of Allah the Almighty, the Holy Prophet(sa) set out towards Khana Kaabah[iii] so he could do Umra and perform the Tawaaf. He did not make this decision for any personal benefit or to increase his own status or influence in society. Nor did he make it in order to assert his authority over the Makkan people. Despite his noble intentions, this decision was wrong, as it was not the Decree of Allah that he should go for Umra that year.
It was an innocent mistake whereby the decision of the Messenger of Allah (sa) was rooted purely in the fear of Allah and his all-encompassing desire to fulfil what he believed to be Allah's Will. As a consequence, regarding this decision, in chapter 48, verse 2 of the Holy Quran, Allah Ta'aala states:
اِنَّا فَتَحۡنَا لَکَ فَتۡحًا مُّبِیۡنًا
"Verily, We have granted thee a clear victory."
Allah the Almighty makes it clear that the error in judgement was due to the Holy Prophet's(sa) unconditional love for Allah the Almighty and his absolute determination to be obedient to His Will. Thus, Allah the Almighty stated that instead of causing harm or damage, this mistake would prove the basis and an everlasting symbol for a great victory of Islam in the future. In fulfillment of this promise, the entire world came to see how gloriously that innocent mistake foreshadowed a monumental and historic victory for Islam!
On the other hand, another incident from the time of the Holy Prophet(sa) proves the point that a logical and well-reasoned decision will ultimately prove fateful if it is bereft of spirituality and the fear of Allah. At the Battle of Uhud, the Holy Prophet(sa) stationed a group of his followers at a certain place and instructed that no matter what, regardless of whether victory or defeat occurred, they were not to leave their assigned post under any circumstances. However, when the enemies of Islam were on the verge of defeat and in a state of retreat, the Muslims disregarded the instruction of the Holy Prophet(sa) and left their post, even though true obedience and the fear of Allah demanded that they remain in position.
The result was that the seemingly certain victory of the Muslims was transformed into a catastrophic and tragic defeat. Accordingly, I wish to remind every one of you that you must remain immersed in the fear of Allah and you must respect the dignity of one another and speak considerately and above all always speak the truth, if you want success in your efforts and plans. Your sole objective should be to attain the love and pleasure of Allah the Almighty in all circumstances.
At all times, be determined and ready to sacrifice your time, wealth and life for the cause of Islam and ensure that there is not even a trace of personal interest or ego clouding any of your decisions or intentions. You should never be motivated by a desire to attain the praise of others. For example, when you give Chanda or make other financial sacrifices you must ensure that they are given purely for the sake of Allah the Almighty and not to impress any individual. Always give precedence to your faith over all worldly matters and understand that the work of a spiritual community is far different from the work of an ordinary worldly company or group.
For example, in worldly organisations the projects and goals are limited and whatever is earned tends to be invested in the same limited area. However, if the Promised Messiah(as) or his Khulafa had followed such worldly principles, then our Tabligh[iv] efforts would have been stopped in their tracks. For example, if it was decided that funds received through Chanda would only be spent in the country or city from where they were donated then our Jama'at could not flourish or continue to spread worldwide.
Alternatively, if it was decided that the Jama'at's limited funds would only be spent on Tabligh, but not on Ishaat or elsewhere, then our Jama'at's continued progress would be at risk. Similarly, if it was decided that we should stop building mosques in order to save money, we would soon see that our Jama'at's spiritual development would grind to a halt and we would no longer witness the blessings of Allah the Almighty. Hence, we have an array of objectives and tasks and they must all be fulfilled.
The national budget should be drawn up in a way that enables the various spheres of work of the Jama'at to be fulfilled and to improve. Above all else, when preparing a budget or allocating resources, it is necessary that the fear of Allah remains at the front and centre of one's mind. If proposals are made in a God-fearing way and funding is allocated in accordance with the instructions of the Khalifatul Masih then our Jama'at's limited resources will surely be blessed manifold by Allah the Almighty. This is what our history has always shown and the same remains the case today. Our limited resources should be utilised for Tabligh, Tarbiyyat[v], the publishing of literature and building new mosques.
It should be used to help the poor and needy.
It should be used to provide education to those who have no access to it.
It should be used to fund the medical treatment of underprivileged and deprived people.
It should be used to help nourish and raise vulnerable children, such as orphans.
If we look objectively at our Jama'at's budget, it is rational to wonder how it will ever be possible to fulfil all of these objectives and tasks. The reality is that the funds we raise are nothing in comparison to the budgets of nations and of countless worldly organisations. However, due to the blessings of Allah the Almighty, where worldly communities spend millions upon millions, we can achieve far more at a fraction of the cost. Moving on, in terms of your conduct as members of Majlis-e-Shura, it is essential that you maintain the highest moral standards and treat others with love, respect and kindness.
You should set a personal example for others to learn from and follow. Only if you are observing the true principles of Islam can you sincerely encourage others to do the same. Only then can you inspire other Ahmadis to increase their financial sacrifices for the sake of Allah and to give their time for the service of the Jama'at. Furthermore, it is imperative that you do not forget whatever you have heard or learned at this Shura once the proceedings draw to a close.
Recognise the fact that your duties do not end today as you walk out of this hall, but continue throughout the year. In terms of the budget that has been debated and approved by the Shura, it is your obligation as Shura members to motivate the members of your respective Jama'ats about the importance of financial sacrifice, so that the budget can be achieved and so that the great tasks of our Jama'at – some of which I have just outlined – can be fulfilled.
Remember that believers have been created in order to awaken others and certainly not that he himself remains in a state of slumber. Our opponents are taking all possible measures in order to impede the progress of our Jama'at. In Muslim countries, on a daily basis, schemes are being hatched and immense efforts are being made to frustrate our Jama'at's growth.
Yet in spite of their cruel and unjust endeavours, Allah the Almighty is granting us continued success. Many of you migrated to the UK from abroad, whilst others have grown up here and taken benefit from the educational opportunities that exist. Most importantly, Allah the Almighty has enabled all of you to serve the Jama'at.
Indeed, here at this Shura, you have been given the opportunity to come as representatives of your respective Jama'ats. Now it is up to you to prove that you are not just representatives in name, but are genuine ambassadors of your Jama'ats through your conduct and standards of righteousness. Remember that a true Shura representative is he who is the one who speaks truthfully on behalf of those whom he represents and strives earnestly to implement whatever is decided in the better interests of the Jama'at. Consequently, if and when the decisions of this year's Shura are approved by me, you must spend the coming year striving to implement them regardless of whether they are related to Tabligh, Tarbiyyat or the budget.
If you fail to do so, how can you call yourself a representative of the Jama'at? In reality, you will only be a representative in name and will not have fulfilled the trust placed in you. Another element of fulfilling your duty as a representative of your Jama'at is to be an example for your local Jama'at members and to guide them with love and compassion. In terms of Tarbiyyat, you should motivate them to take part in all of our Jama'at events and programmes.
In terms of Tabligh, you should not only take personal responsibility for spreading the message of Islam but you should also activate those people who you represent. In terms of the financial budget, you can only fulfil your duties when you, with the fear of Allah in your heart, make appropriate financial sacrifices according to whatever you earn and fulfil your pledges. Thereafter, you must encourage the other members of the Jama'at about the importance and benefits of financial sacrifices.
At the end, I reiterate the fact that your duty as a representative of your Jama'at will continue throughout the year. So, if the decisions of this year's Majlis-e-Shura are approved by me you must ensure that you personally make every possible effort to fulfil them and strive to ensure that others are also making a concerted effort to implement them. With these words, it is my sincere hope and prayer that the fear of Allah remains firmly ingrained in your hearts and that you take all of your responsibilities very seriously and devotedly strive to fulfil your obligations as members of Majlis-e-Shura.
May Allah the Almighty grant you the ability to do so. Ameen."
'Musleh Maud' means Promised Reformer and refers to Hazrat Mirza Bashir-Ud-Din Mahmud Ahmad, the Second Worldwide Head of the Ahmadiyya Muslim Community. He formally established the Maljis-e-Shura as a body within the Ahmadiyya Muslim Community, although its roots can be traced to the founder of the Ahmadiyya Muslim Community, Hazrat Mirza Ghulam Ahmad(as).
Successor (Caliph) to the Promised Messiah
The Kaaba is the cube shaped building found in Makkah, modern day Saudi Arabia which Muslims refer to as the House of God. It is in the direction of the Kaaba that all Muslims perform their formal prayers to God five times a day.
Propagating the true message of Islam
Moral and spiritual training
Huzoor's address at UK Shura 2019
Listen on Podcast
Guidance Regarding Pandemic & Situation in America and the World
Special Message by Worldwide Head of the Ahmadiyya Muslim Community
Honesty, Dedication and Righteousness – Role of an Office Bearer
Ahmadi Muslim Researchers – Restoring Islam's Golden Age
Training of the Waqf-e-Nau – Duties of Waqf-e-Nau Secretaries


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text:
$100,000 reward offered in ambush shooting of two Los Angeles County deputies
Los Angeles County Sheriffs Department (LASD) deputies walk outside St. Francis Medical Center hospital following the ambush shooting of two deputies in Compton, in Lynwood, California, U.S., September 13, 2020. REUTERS/Patrick T. Fallon
(Reuters) – As the manhunt for the lone gunman who ambushed and shot two Los Angeles County sheriff's deputies enters its third day, authorities are offering a $100,000 reward for information that leads to an arrest and conviction.
Video footage of the shooting showed a man walk up to a parked patrol car on Saturday evening at a transit station in the Compton community and fire a pistol into the passenger side of the squad car. The man then ran away.
Both deputies received critical head wounds, but both are expected to survive, police said. The deputies are described as a 31-year-old female officer who is a mother and a 24-year-old man, police said.
"We'll see what the long-term impact is. We don't know that yet, but they survived the worst," Los Angeles County Sheriff Alex Villanueva told reporters on Sunday.
"We would like to offer our sincerest appreciation for the overwhelming support being offered from all over the Nation," he wrote on Twitter.
The reward was offered late Sunday by the Los Angeles County Board of Supervisors.
A few demonstrators gathered overnight Saturday outside St. Francis Medical Center in Lynwood where the deputies were being treated, according to social media video and the sheriff's department, blocking the entrance and chanting anti-police slogans.
Two people were later arrested, including a journalist who was later released.
The description of the shooter still remains vague.
"At this point we have a very, very generic description of a dark-skinned male and that came from one of the victims," Captain Kent Wegener told a news conference Sunday.
President Donald Trump retweeted the video early on Sunday and wrote: "Animals that must be hit hard!"
Later, referring to the deputies, Trump tweeted: "If they die, fast trial death penalty for the killer. Only way to stop this!"
Former Vice President Joe Biden, Trump's Democratic rival in for Nov. 3 presidential election, called for the gunman to face "the full brunt of the law."
(Reporting by Rich McKay in Atlanta)
Posted on September 14, 2020 By Reuters News Agency
This entry was tagged ambushed, anti-police slogans, Compton, demonstrators, lone gunman, Los Angeles County sheriff's deputies, Reward, Shooting. Bookmark the permalink.
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redpajama_set_name: RedPajamaCommonCrawl


If you have previously attended a higher education institution and are looking to return, you fall under our Adult Returning Student classification.
If you have previously attended higher education institution and are looking to return, you are considered an Adult Returning Student. Whether you have credits from a previous college or are returning to UofL, our office is here to assist you through the (re)application process to finish your degree.
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If you are unsure when you last attended classes, please contact our office at 502-852-0166 or transfer@louisville.edu. Depending on your classification, you may be working with the Registrar's Office or Transfer Services.
If you would like to speak our transfer admissions counselor who works specifically with our adult returning students, please schedule an appointment with Taylor U'Sellis. Appointments are available in person and over the phone.


help. HOW DO I FIX THIS?!?!?
Responses to "Pls answer huge problem"
Schedule the drive for CHKDSK on a reboot.
CCleaner - skipping the registry cleaner part..
completely different version of win?
> still a problem. HELP!
Fer Crisakes, please fill us in!!
> > > > > Fer Crisakes, please fill us in!


text:
What is Asynchronous Javascript?
Asynchronous JavaScript is best described as being able to multitask while running one program and working on another. In other words, if your program is running a particularly long task, asynchronous coding allows you to work on other tasks while that code is running.
Code Institute graduate Guillermo Brachetta explains Asynchronous JavaScript with some intriguing examples in this article.
Hugo's Office
It's 9 in the morning, and Hugo's day has just started.
Like any other day, the first thing Hugo does is get some coffee, so he approaches the machine, makes a choice (double espresso) and waits. Someone says 'good morning', but he doesn't hear them straight away. He only realizes once the coffee is ready (it takes a minute or two) and replays their words back. Hugo grabs his cup and goes to his desk to start his computer. Hugo stares at the screen: he is strangely fascinated by that black rectangle coming to life. He particularly enjoys the progress bar reaching the end.
There's a message from his boss: Hugo needs to print a long document and get it signed by the client by the end of the day. So he presses the button and waits for the documents to be all out of the printer.
Hugo writes an email to their client asking what would be a suitable time to sign the papers. He sends it and waits. Finally, after two hours, a reply comes in, and he eagerly reads the email: the signature can take place by the end of the day, so he sits back, relaxes, and waits.
Fabio's Office
Fabio works at Hugo's competitor company, and they have a similar routine. Fabio also likes coffee and goes every morning to the machine. While he waits for his coffee to be ready, he catches up with colleagues. Back to his desk, he turns his computer on, and while it starts, he gives his boss a call regarding the contract they need to finalize today. His boss gives him a couple of straightforward instructions and raises a point or two. His computer is finally on, and they can discuss details by looking at the email from the client. Fabio quickly adjusts the contract while on the phone. By the time the conversation is over, the document has already been sent to the printer to be signed.
Fabio then emails the client asking for a good moment to get the contract signed, and immediately after starts to fill in the gaps from another document that needs attention. There's a long day ahead, and he's counting on closing a few important deals, but it all looks good, and it's only 9:30.
Synchronous Code
As we've seen at Hugo's office, every action happens in succession, and Hugo needs to wait for each of them to be completed before he can do anything else. Or even worse: Hugo could be sending an empty envelope to his client if he doesn't let the contract be out of the printer first. This is synchronous code, and the problem is apparent: there's code running that is blocking the execution of the rest of it until the resources are free, or comes in an undesired order, or creates an error.
JavaScript is very fast, but some actions require time, no matter how little. Think, for example, of a request to a database that may take some time or even a complex mathematical calculation; synchronous code execution will at least block the rest of the code or break it.
This is an example of synchronous code

const showGreeting = (content) => {
console.log(content);
const runMeFirst = () => {
showGreeting("Hello");
const runMeNext = () => {
showGreeting("World!");
runMeFirst();
runMeNext();
The code above will print in the console
World!
Because the functions are executed in the order specified, and they take very negligible time. But let's now imagine that the first function takes some longer time, say it is a request to fetch some data from a database. We will simulate an asynchronous request that needs time to yield a result by adding a setTimeout function with a duration of 1 second (1000 milliseconds).
const showGreeting = (content) => {
console.log(content);
const runMeFirst = () => {
setTimeout(() => {
showGreeting('Hello');
}, 1000);
const runMeNext = () => {
showGreeting('World!');
When we execute them, the result, in this case, will be
And that's certainly not what we want. Instead, we want our mock asynchronous function to run in the correct order.
How can we fix this?
There are three ways to run code asynchronously:
Callback functions
Promises (ES6)
Async/Await (ES8)
Callbacks are the original way JavaScript used to run code asynchronously. It basically is a function that is passed as a parameter to another function and is executed when the previous one has finished.
For our code above, this is an implementation of asynchronously running the code above:
const runMeFirst = (callback) => {
callback();
runMeFirst(runMeNext);
In it, the runMeFirst function is passed a callback function as a parameter. This callback function, runMeNext, is executed when the first function has finished.
While this works perfectly well, it's easy to realize that this is fine in the given example, but that it becomes a lot more difficult to read and maintain as soon as the code gets bigger, and we need to deal with more complex scenarios and multiple asynchronous functions. It is a very common pattern to see nested callbacks deepened into the call, with the last callback being the one that is executed when all the previous ones have finished. This can become what's commonly called callback hell, when a succession of callbacks functions end up being nested inside each other, making the code awkwardly confusing.
Luckily, there came a solution to this problem: the Promise object.
Promises were first introduced with ES6 in 2015, and they are a way to handle asynchronous code in a way that is more readable and easier to use.
A promise is an object that represents the eventual completion or failure of an asynchronous operation or, in other words, it is an object that represents an operation that hasn't been completed yet.
A promise is in one of the following states:
Pending: its initial state, neither fulfilled nor rejected.
Fulfilled: when the operation has completed successfully.
Rejected: when the operation failed.
A promise in a pending state is said to be unresolved, and we need to wait for it to be either resolved or rejected before we can do anything with it.
Let's assume that the timeout function returns a promise, for example, let's imagine that it's a request to fetch some data from a remote server. We will mock the time it takes for the promise to resolve by using that setTimeout() that takes 1 second, and we will use the Promise constructor with our setTimeout() in order to simulate that fetch request that needs some time to complete.
const runMeFirst = () => new Promise((resolve, reject) => {
// Error handling would be needed here.
// For the sake of our example let's assume that the fetch request was successful.
const error = false;
if (!error) {
// If there's no error we resolve the promise.
resolve();
// If there's an error we reject it and handle the error.
reject(new Error('Something went wrong'));
Now let's incorporate our new function into our code:
runMeFirst()
.then(runMeNext)
.catch((err) => console.log(err)
As we can see above, we deal with the promise using the .then and .catch methods, instructing our promise to run, and then execute the next function only after the first one has finished:
runMeFirst().then(runMeNext)
This handles the resolve scenario (that is, if the promise was successful). We then use the .catch method to handle the reject scenario (that is, if the promise failed).
Subsequent promises can be chained together, for example:
.then(oneMorePromise)
.then(yetAnotherPromise)
.catch((err) => console.log(err));
Another way to handle a series of chained promises is using the Promise.all method. This method takes an array of promises as a parameter and returns a new promise that is resolved when all the promises in the array have resolved, or it is rejected when any of the promises in the array have been rejected, and the error is passed to the catch method of the only .then() method of the returned promise:
Promise.all([runMeFirst, runMeNext, oneMorePromise, yetAnotherPromise]).then((values) => {
console.log(values) // Handle resolved values here.
}).catch((err) => console.log(err)); // Handle rejected values here.
A newer way to handle asynchronous code was made available with the introduction of the async and await keywords in ES8 (or ES2017).
These new keywords make it even easier to read, write and understand asynchronous code, turning the series of chained .then() and .catch() calls into a very natural, human-readable format.
In order to deal with a promise in this way, we need to use the async keyword in the function and await for the result of the promise.
Let's create a new function, which we'll call init for this example, that uses the async keyword:
const init = async () => {
await runMeFirst();
It reads very similar to the way we talk, and it's immediately clear what we are expecting to happen:
We know that our function is going to deal with asynchronous code by the use of the async keyword.
We can immediately see that it is going to deal with a promise, so we need to use the human-readable await keyword (in other words, when we see await before a function we can be sure we are expecting a promise to be returned).
The following function is synchronous, and thus it doesn't need to be preceded by any keyword.
Our previous example can then be rewritten as:
// The function returns a promise.
const runMeFirst = () =>
new Promise((resolve, reject) => {
// The synchronous function.
// The new asynchronous function using async/await.
// Call the new asynchronous function.
So, even though JavaScript is a single-threaded language, we can still make it work as if it was capable of 'multitasking' thanks to its asynchronous capabilities, made very accessible by the introduction of promises with ES6 and easy to read by the incorporation of the async and await keywords with ES8.
Asynchronous JavaScript unleashes the full power the language has to offer, and the relatively recent introduction of progressive ways to use it makes us be sure of the health and future of JavaScript.
Modern frameworks such as React, Next.js and Vue make extensive use of the power of asynchronous code. They are tremendously popular and powerful, and the steady growth and refinement of these and new libraries and frameworks is a clear indication of the exciting potential JavaScript has yet to offer for a long time ahead.
Guillermo Brachetta, Code Institute Graduate
Learn some coding basics for free
If you want to learn some of the basics of JavaScript for free, try this free 5 Day Coding Challenge. On it, you will learn the basics of HTML, CSS and JavaScript. It takes just one hour a day over five days. Register now through the form below. Alternatively, if you want to learn full-stack software development, you can read more about our programme here.
Coding JavaScript


The ABBRA Symposium is a conference focusing on the issues that affect boat builders, boat repair, boat service, service companies, and associated businesses. It is an opportunity to build relationships with other professionals that share common interests and challenges.
We are launching our Annual Meeting & Symposium with a Cocktail Reception and Annual Meeting on Tuesday January 24th, 2017 from 6:00 pm – 9:00 pm, during which we will present our Annual Awards and ABBRA's industry recognized Marine Service Manager's Certification credential.
Financial Management for the Non-Financial Manager.


Valente Development Corporation is moving forward with a new condo development in Riverside despite Windsor City council's refusal for a reduction in development charges.
They were looking for a reduction of $185,000 from the city. President Peter Valente says that would have meant he could have sold each unit for around $5,000 less.
Still he thinks there is an appetite in Windsor for this type of development. "The market is kind of taking a little bit of a turn in Windsor and houses seem to be selling very well. Coupled with the lack of inventory homes that are on the market right now then I felt that this could be the right time to have the project be a success," says Valente.
Sales for the units will begin in the spring with hopes of having it 60% sold by the fall to start construction.


text:
Digital Transformation Insights
We believe every great leader can create an exceptional organisation in the digital age
Digital Transformation InsightsMelissa McCafferty2020-07-23T13:31:06+00:00
The Difference Between Digitization and Digital Transformation
By Niall McKeown|2020-09-24T18:11:51+00:00July 6th, 2020|Categories: Blogs|
What is the difference between digitisation and digital transformation? Some
Digital Transformation Explained
By Melissa McCafferty|2020-09-16T20:24:49+00:00April 14th, 2017|Categories: Blogs, Questions & Answers, Videos|
Digital Transformation is how an organisation becomes built to
In The Age of Robots, Cobots and AI, What About Humans?
By John Briggs|2020-04-06T15:33:11+00:00October 24th, 2018|Categories: AI Case Studies, Blogs|
Robots, Cobots and AI Machines It is nearly impossible
Digital Transformation & AI Case Studies
Government Dept
Telecoms Provider
Enterprise Tech Sales
The Seven Principles of Digital Business Strategy
by Niall McKeown and Mark Durkin
If we are creating most of our competitive advantage at the strategic planning stage, why are we spending so little time on this and so much time on technology? This book is not about why you should digitally transform and become more strategic; it's about how. It lays out the steps that must be taken, the data that should be used, and the decision tree to be followed. Following the principles laid out in this book allows organizational leaders, marketers, and technologists to talk at a high strategic level without getting bogged down in the tactics and delivery that consumes most of the time, attention, and activity in the modern workplace.
Niall McKeown
Digital Transformation Strategist, Author, Lecturer, Keynote Speaker & Business Owner. Award-winning strategy consultant, thought leader and in-demand public speaker on digital transformation with a 20-year track record of delivering game-changing strategies for organisations across the globe.
Buy Book on Amazon
Digital Transformation & AI – Your Top Questions Answered
Q1: What Happens to...
Q2: Digital Transformation; Strategy...
Q3: Data First or...


Technology is an exciting and thriving competency within our Consulting Service Line. We have a diverse team with around 1700 people working on challenging engagements across a wide portfolio of clients, and operating from many offices around the UK. Our breadth and depth of expertise enables us to work with FTSE 100 clients to help define, shape and successfully deliver some of their most complex technology projects. The quality of our technical skills is enhanced through our practical knowledge of implementation and our ability to team with each other. Our tools and methodologies add to the quality, efficiency and effectiveness of our work.
Working with some of the leading technology vendors in the UK, our rapidly growing Tech Futures team is integral to the delivery of new solutions and propositions for clients and getting us closer to the innovative technologies in 'Tech City'. Working with other practitioners from within the Technology competency and across the Deloitte service lines as a whole, these teams build and maintain alliance relationships with leading technology providers and provide the bridge between business and technology innovation, to deliver great value to our clients on technology-enabled business transformation.
Experience in developing and delivering internal marketing campaigns for innovative technologies that can be utilized across the technology practice.


text:
BABY OVERDOSES ON FENTANYL FOR SECOND TIME, CELEBRATES FIRST BIRTHDAY IN HOSPITAL
Source: Columbia police
By:Aaron Rasmussen
A South Carolina baby boy recently overdosed on fentanyl for the second time and his parents are now under arrest, police said.
On the morning of March 17, Donald Ray Little, Jr., 39, and Mary Ashley Willis, 27, were sleeping at a hotel when the child ingested an unknown amount of an illegal controlled substance, the Columbia Police Department said in a news release obtained by FrontPageDetectives.
"A male and a female brought a child to the front of headquarters that was very unresponsive, shallow breathing," Lt. CB Williams said, according to the television station WACH.
7-month-old baby dies from head injuries, babysitter arrested for murder: report
TEXAS WOMAN ALLEGEDLY LEAVES NEWBORN TO DROWN IN TOILET WHILE OUT ON PAROLE FOR HER BABY SON'S 2011 DEATH
A TODDLER WAS BEATEN TO DEATH AND POLICE SAY A 31-YEAR-OLD MAN IS RESPONSIBLE
Emergency crews rushed the boy to the hospital, where he tested positive for fentanyl. He celebrated turning 1 year old the next day while still hospitalized.
"The child is doing great," Williams told WACH, noting that a group of construction workers who witnessed what happened gave officers and victim advocates birthday presents for the baby.
"He was nothing but smiles and giggling and happy," Williams said. "It was very heartwarming to see the child was alright."
Little and Willis are charged with unlawful neglect of a child. Little is also accused of possession of a controlled substance and possession of ammunition by a convicted violent felon, according to Alvin S. Glenn Detention Center online records.
The baby is now in the emergency protective custody of the South Carolina Department of Social Services.
"I mean, that's a dangerous situation. All medication, no matter what it is, should be kept secured, up on high shelves and should not be in the reach of any children, and, of course, you shouldn't be using illegal drugs," Williams said.


All County Air Conditioning, Refrigeration & Heating Company provides excellent customer service. We diagnose any problems you have with your existing system, and if needed install new high efficiency system(s) in your home. We service and offer all brands of equipment that is best suited for your home and comfort as well as your wallet. We take into consideration your personal needs within your home and we address them, building a completely custom indoor comfort system for you and your family.
Our service techs are NATE-Certified (North American Technician Excellence) in air conditioning, heat pump, and air distribution, and they receive on going education from equipment manufacturers. They are some of the BEST and most highly-trained HVAC service technicians, ready to work with you to help resolve any equipment issues you may be having.
You'll always be quoted a price before the work is started, this way you know what to expect. We do not charge by the hour, we charge a FLAT RATE pricing only.


text:
ConVar asw_director_debug("asw_director_debug", "0", FCVAR_CHEAT, "Displays director status on screen");

extern ConVar asw_intensity_far_range;
extern ConVar asw_spawning_enabled;

extern ConVar asw_horde_override;
extern ConVar asw_wanderer_override;
ConVar asw_horde_interval_min("asw_horde_interval_min", "45", FCVAR_CHEAT, "Min time between hordes" );
ConVar asw_horde_interval_max("asw_horde_interval_max", "65", FCVAR_CHEAT, "Min time between hordes");
ConVar asw_horde_interval_scale("asw_horde_interval_scale", "10", FCVAR_CHEAT, "actual time between hordes = interval * scale / (offset + mission difficulty)");
ConVar asw_horde_interval_offset("asw_horde_interval_offset", "5", FCVAR_CHEAT, "actual time between hordes = interval * scale / (offset + mission difficulty)");

ConVar asw_director_relaxed_min_time("asw_director_relaxed_min_time", "25", FCVAR_CHEAT, "Min time that director stops spawning aliens");
ConVar asw_director_relaxed_max_time("asw_director_relaxed_max_time", "40", FCVAR_CHEAT, "Max time that director stops spawning aliens");
ConVar asw_director_peak_min_time("asw_director_peak_min_time", "1", FCVAR_CHEAT, "Min time that director keeps spawning aliens when marine intensity has peaked");
ConVar asw_director_peak_max_time("asw_director_peak_max_time", "3", FCVAR_CHEAT, "Max time that director keeps spawning aliens when marine intensity has peaked");
ConVar asw_interval_min("asw_interval_min", "1.0f", FCVAR_CHEAT, "Director: Alien spawn interval will never go lower than this");
ConVar asw_interval_initial_min("asw_interval_initial_min", "5", FCVAR_CHEAT, "Director: Min time between alien spawns when first entering spawning state");
ConVar asw_interval_initial_max("asw_interval_initial_max", "7", FCVAR_CHEAT, "Director: Max time between alien spawns when first entering spawning state");
ConVar asw_interval_initial_scale("asw_interval_initial_scale", "10", FCVAR_CHEAT, "actual time until first wanderer = interval * scale / (offset + mission difficulty)");
ConVar asw_interval_initial_offset("asw_interval_initial_offset", "5", FCVAR_CHEAT, "actual time until first wanderer = interval * scale / (offset + mission difficulty)");
ConVar asw_interval_change_min("asw_interval_change_min", "0.9", FCVAR_CHEAT, "Director: Min scale applied to alien spawn interval each spawn");
ConVar asw_interval_change_max("asw_interval_change_max", "0.95", FCVAR_CHEAT, "Director: Max scale applied to alien spawn interval each spawn");

CASW_Director g_ASWDirector;
CASW_Director* ASWDirector() { return &g_ASWDirector; }

CASW_Director::CASW_Director( void ) : CAutoGameSystemPerFrame( "CASW_Director" )
{

}

CASW_Director::~CASW_Director()
{

}

bool CASW_Director::Init()
{
	m_bSpawningAliens = false;
	m_bReachedIntensityPeak = false;
	m_fTimeBetweenAliens = 0;
	m_AlienSpawnTimer.Invalidate();
	m_SustainTimer.Invalidate();
	m_HordeTimer.Invalidate();
	m_IntensityUpdateTimer.Invalidate();
	m_bInitialWait = true;

	m_bFiredEscapeRoom = false;

	m_bHordeInProgress = false;
	m_bFinale = false;

	// take horde/wanderer settings from director control
	CASW_Director_Control* pControl = static_cast<CASW_Director_Control*>( gEntList.FindEntityByClassname( NULL, "asw_director_control" ) );
	if ( pControl )
	{
		m_bWanderersEnabled = pControl->m_bWanderersStartEnabled;
		m_bHordesEnabled = pControl->m_bHordesStartEnabled;
		m_bDirectorControlsSpawners = pControl->m_bDirectorControlsSpawners;
		m_flPreSpawnAliens = pControl->m_flPreSpawnAliens;
	}
	else
	{
		m_bWanderersEnabled = false;
		m_bHordesEnabled = false;
		m_bDirectorControlsSpawners = false;
		m_flPreSpawnAliens = 0;
	}

	return true;
}

void CASW_Director::Shutdown()
{

}

void CASW_Director::LevelInitPreEntity()
{
	if ( ASWSpawnManager() )
	{
		ASWSpawnManager()->LevelInitPreEntity();
	}
}

void CASW_Director::LevelInitPostEntity()
{
	Init();

	if ( ASWSpawnManager() )
	{
		ASWSpawnManager()->LevelInitPostEntity();
	}
}

void CASW_Director::LevelShutdownPostEntity()
{
	Shutdown();

	if ( ASWSpawnManager() )
	{
		ASWSpawnManager()->LevelShutdownPostEntity();
	}
}

void CASW_Director::FrameUpdatePreEntityThink()
{

}

void CASW_Director::FrameUpdatePostEntityThink()
{
	// only think when we're in-game
	if ( !ASWGameRules() || ASWGameRules()->GetGameState() != ASW_GS_INGAME )
		return;

	//PJ - Hook in mod_player_performance
	CMOD_Player_Performance::PlayerPerformance()->FrameUpdatePostEntityThink();

	UpdateIntensity();

	if ( ASWSpawnManager() )
	{
		ASWSpawnManager()->Update();
	}

	UpdateMarineRooms();

	if ( !asw_spawning_enabled.GetBool() )
		return;

	UpdateHorde();

	UpdateSpawningState();

	bool bWanderersEnabled = m_bWanderersEnabled || asw_wanderer_override.GetBool();
	if ( bWanderersEnabled )
	{
		UpdateWanderers();
	}
}

// randomly generated levels provide data about each room in the level
// we check that here to react to special rooms
void CASW_Director::UpdateMarineRooms()
{
	CASW_Game_Resource *pGameResource = ASWGameResource();
	if ( !pGameResource || !missionchooser || !missionchooser->RandomMissions())
		return;

	for ( int i=0;i<pGameResource->GetMaxMarineResources();i++ )
	{
		CASW_Marine_Resource *pMR = pGameResource->GetMarineResource(i);
		if ( !pMR || !pMR->GetMarineEntity() || pMR->GetMarineEntity()->GetHealth() <= 0 )
			continue;

		IASW_Room_Details* pRoom = missionchooser->RandomMissions()->GetRoomDetails( pMR->GetMarineEntity()->GetAbsOrigin() );
		if ( !pRoom )
			continue;

		if ( !m_bFinale && pRoom->HasTag( "Escape" ) )
		{
			UpdateMarineInsideEscapeRoom( pMR->GetMarineEntity() );
		}
	}
}

// increase intensity as aliens are killed (particularly if they're close to the marines)
void CASW_Director::Event_AlienKilled( CBaseEntity *pAlien, const CTakeDamageInfo &info )
{
	if ( !pAlien )
		return;

	CASW_Game_Resource *pGameResource = ASWGameResource();
	if ( !pGameResource )
		return;

	//Pass event to mod_player_performance
	CMOD_Player_Performance::PlayerPerformance()->Event_AlienKilled(pAlien, info);

	bool bDangerous = pAlien->Classify() == CLASS_ASW_SHIELDBUG;       // shieldbug
	bool bVeryDangerous = pAlien->Classify() == CLASS_ASW_QUEEN;		// queen

	for ( int i=0;i<pGameResource->GetMaxMarineResources();i++ )
	{
		CASW_Marine_Resource *pMR = pGameResource->GetMarineResource(i);
		if ( !pMR )
			continue;

		CASW_Marine *pMarine = pMR->GetMarineEntity();
		if ( !pMarine || pMarine->GetHealth() <= 0 )
			continue;

		CASW_Intensity::IntensityType stress = CASW_Intensity::MILD;

		if ( bVeryDangerous )
		{
			stress = CASW_Intensity::EXTREME;
		}
		else if ( bDangerous )
		{
			stress = CASW_Intensity::HIGH;
		}
		else
		{
			float distance = pMarine->GetAbsOrigin().DistTo( pAlien->GetAbsOrigin() );
			if ( distance > asw_intensity_far_range.GetFloat() )
			{
				stress = CASW_Intensity::MILD;
			}
			else
			{
				stress = CASW_Intensity::MODERATE;
			}
		}

		pMR->GetIntensity()->Increase( stress );
	}

	ASWArena()->Event_AlienKilled( pAlien, info );
}

// increase intensity as marines take damage
void CASW_Director::MarineTookDamage( CASW_Marine *pMarine, const CTakeDamageInfo &info, bool bFriendlyFire )
{
	if ( !pMarine )
		return;

	// friendly fire doesn't cause intensity increases
	if ( bFriendlyFire )
		return;

	float flDamageRatio = info.GetDamage() / pMarine->GetHealth();

	CASW_Intensity::IntensityType stress = CASW_Intensity::MILD;
	if ( flDamageRatio < 0.2f )
	{
		stress = CASW_Intensity::MODERATE;
	}
	else if ( flDamageRatio < 0.5f )
	{
		stress = CASW_Intensity::HIGH;
	}
	else
	{
		stress = CASW_Intensity::EXTREME;
	}

	if ( pMarine->GetMarineResource() )
	{
		pMarine->GetMarineResource()->GetIntensity()->Increase( stress );
	}
}

void CASW_Director::UpdateHorde()
{
	if ( asw_director_debug.GetInt() > 0 )
	{
		if ( m_bHordeInProgress )
		{
			engine->Con_NPrintf( 7 + ASW_MAX_MARINE_RESOURCES, "Horde in progress.  Left to spawn = %d", ASWSpawnManager()->GetHordeToSpawn() );
		}
		engine->Con_NPrintf( 8 + ASW_MAX_MARINE_RESOURCES, "Next Horde due: %f", m_HordeTimer.GetRemainingTime() );

		engine->Con_NPrintf( 11 + ASW_MAX_MARINE_RESOURCES, "Awake aliens: %d\n", ASWSpawnManager()->GetAwakeAliens() );
		engine->Con_NPrintf( 12 + ASW_MAX_MARINE_RESOURCES, "Awake drones: %d\n", ASWSpawnManager()->GetAwakeDrones() );
	}

	bool bHordesEnabled = m_bHordesEnabled || asw_horde_override.GetBool();
	if ( !bHordesEnabled || !ASWSpawnManager() )
		return;

	if ( !m_HordeTimer.HasStarted() )
	{
		float flDuration = RandomFloat( asw_horde_interval_min.GetFloat(), asw_horde_interval_max.GetFloat() ) * asw_horde_interval_scale.GetFloat() / ( asw_horde_interval_offset.GetFloat() + (float) ASWGameRules()->GetMissionDifficulty() );
		if ( m_bFinale || flDuration < 5.0f || !IsFinite( flDuration ) )
		{
			flDuration = RandomFloat( 5.0f, 10.0f );
		}
		if ( asw_director_debug.GetBool() )
		{
			Msg( "Will be spawning a horde in %f seconds\n", flDuration );
		}
		m_HordeTimer.Start( flDuration );
	}
	else if ( m_HordeTimer.IsElapsed() )
	{
		if (ASWSpawnManager()->GetAwakeAliens() >= 100 || ASWSpawnManager()->GetAwakeDrones() >= 30)
		{
			if (asw_director_debug.GetBool())
			{
				Msg("Too many awake aliens. Delaying horde.\n");
			}
			m_HordeTimer.Start( 10.0f );
			return;
		}

		if ( ASWSpawnManager()->AddRandomHorde() )
		{
			m_bHordeInProgress = true;

			if ( ASWGameRules() )
			{
				ASWGameRules()->BroadcastSound( "Spawner.Horde" );
			}
			m_HordeTimer.Invalidate();
		}
		else
		{
			// if we failed to find a horde position, try again shortly.
			m_HordeTimer.Start( RandomFloat( 10.0f, 16.0f ) );
		}
	}
}

void CASW_Director::OnHordeFinishedSpawning()
{
	if ( asw_director_debug.GetBool() )
	{
		Msg("Horde finishes spawning\n");
	}
	m_bHordeInProgress = false;
}

void CASW_Director::UpdateSpawningState()
{
	if ( m_bFinale )				// in finale, just keep spawning aliens forever
	{
		m_bSpawningAliens = true;

		if ( asw_director_debug.GetBool() )
		{
			engine->Con_NPrintf( 3 + ASW_MAX_MARINE_RESOURCES, "%s: %f %s", m_bSpawningAliens ? "Spawning aliens" : "Relaxing",
				m_SustainTimer.HasStarted() ? m_SustainTimer.GetRemainingTime() : -1,
				"Finale" );
		}
		return;
	}

	//=====================================================================================
	// Main director rollercoaster logic
	//   Spawns aliens until a peak intensity is reached, then gives the marines a breather
	//=====================================================================================

	if ( !m_bSpawningAliens )			// not spawning aliens, we're in a relaxed state
	{
		if ( !m_SustainTimer.HasStarted() )
		{
			if ( GetMaxIntensity() < 1.0f )	// don't start our relax timer until the marines have left the peak
			{
				if ( m_bInitialWait )		// just do a short delay before starting combat at the beginning of a mission
				{
					m_SustainTimer.Start( RandomFloat( 3.0f, 16.0f ) );
					m_bInitialWait = false;
				}
				else
				{
					m_SustainTimer.Start( RandomFloat( asw_director_relaxed_min_time.GetFloat(), asw_director_relaxed_max_time.GetFloat() ) );
				}
			}
		}
		else if ( m_SustainTimer.IsElapsed() )		// TODO: Should check their intensity meters are below a certain threshold?  Should probably also not wait if they run too far ahead
		{
			m_bSpawningAliens = true;
			m_bReachedIntensityPeak = false;
			m_SustainTimer.Invalidate();
			m_fTimeBetweenAliens = 0;
			m_AlienSpawnTimer.Invalidate();
		}
	}
	else								// we're spawning aliens
	{
		if ( m_bReachedIntensityPeak )
		{
			// hold the peak intensity for a while, then drop back to the relaxed state
			if ( !m_SustainTimer.HasStarted() )
			{
				m_SustainTimer.Start( RandomFloat( asw_director_peak_min_time.GetFloat(), asw_director_peak_max_time.GetFloat() ) );
			}
			else if ( m_SustainTimer.IsElapsed() )
			{
				m_bSpawningAliens = false;
				m_SustainTimer.Invalidate();
			}
		}
		else
		{
			if ( GetMaxIntensity() >= 1.0f )
			{
				m_bReachedIntensityPeak = true;
			}
		}
	}

	if ( asw_director_debug.GetInt() > 0 )
	{
		engine->Con_NPrintf( 3 + ASW_MAX_MARINE_RESOURCES, "%s: %f %f %s", m_bSpawningAliens ? "Spawning aliens" : "Relaxing",
			m_SustainTimer.HasStarted() ? m_SustainTimer.GetRemainingTime() : -1,
			m_AlienSpawnTimer.HasStarted() ? m_AlienSpawnTimer.GetRemainingTime() : -1,
			m_bReachedIntensityPeak ? "Peaked" : "Not peaked" );
	}
}

void CASW_Director::UpdateWanderers()
{
	if ( !m_bSpawningAliens )
	{
		if ( asw_director_debug.GetInt() > 0 )
		{
			engine->Con_NPrintf( 4 + ASW_MAX_MARINE_RESOURCES, "Not spawning regular aliens" );
		}
		return;
	}

	// spawn an alien every so often
	if ( !m_AlienSpawnTimer.HasStarted() || m_AlienSpawnTimer.IsElapsed() )
	{
		if ( m_fTimeBetweenAliens == 0 )
		{
			// initial time between alien spawns
			m_fTimeBetweenAliens = RandomFloat( asw_interval_initial_min.GetFloat(), asw_interval_initial_max.GetFloat() ) * asw_interval_initial_scale.GetFloat() / ( asw_interval_initial_offset.GetFloat() + (float) ASWGameRules()->GetMissionDifficulty() );;
		}
		else
		{
			// reduce the time by some random amount each interval
			m_fTimeBetweenAliens = m_fTimeBetweenAliens * RandomFloat( asw_interval_change_min.GetFloat(), asw_interval_change_max.GetFloat() );
		}
		if (!IsFinite(m_fTimeBetweenAliens))
		{
			m_fTimeBetweenAliens = asw_interval_min.GetFloat();
		}
		else
		{
			m_fTimeBetweenAliens = MAX(asw_interval_min.GetFloat(), m_fTimeBetweenAliens);
		}

		bool bSkipWanderers = ASWSpawnManager() && ASWSpawnManager()->GetAwakeAliens() >= 100;
		if ( asw_director_debug.GetInt() > 0 )
		{
			if ( bSkipWanderers )
			{
				engine->Con_NPrintf( 4 + ASW_MAX_MARINE_RESOURCES, "Too many awake aliens. Skipping wanderers." );
			}
			else
			{
				engine->Con_NPrintf( 4 + ASW_MAX_MARINE_RESOURCES, "Regular spawn interval = %f", m_fTimeBetweenAliens );
			}
		}

		m_AlienSpawnTimer.Start( m_fTimeBetweenAliens );

		if ( ASWSpawnManager() )
		{
			if ( bSkipWanderers )
			{
				if (asw_director_debug.GetBool())
				{
					Msg("Too many awake aliens. Skipping wanderer.\n");
				}
			}
			else
			{
				ASWSpawnManager()->AddAlien();
			}
		}
	}
}

// if director is controlling alien spawns, then mapper set spawners ask permission before spawning
bool CASW_Director::CanSpawnAlien( CASW_Spawner *pSpawner )
{
	if ( !m_bDirectorControlsSpawners )
		return true;

	return m_bSpawningAliens;
}

void CASW_Director::OnMarineStartedHack( CASW_Marine *pMarine, CBaseEntity *pComputer )
{
	CASW_Game_Resource *pGameResource = ASWGameResource();
	if ( !pGameResource )
		return;

	//Msg( " Marine started hack!\n" );

	// reset intensity so we can have a big fight without relaxing immediately
	for ( int i=0;i<pGameResource->GetMaxMarineResources();i++ )
	{
		CASW_Marine_Resource *pMR = pGameResource->GetMarineResource(i);
		if ( !pMR )
			continue;

		pMR->GetIntensity()->Reset();
	}

	float flQuickStart = RandomFloat( 2.0f, 5.0f );
	if ( m_HordeTimer.GetRemainingTime() > flQuickStart )
	{
		m_HordeTimer.Start( flQuickStart );
	}

	// TODO: Instead have some kind of 'is in a big fight' state?
}

void CASW_Director::OnMarineBurnedBiomass( CASW_Marine *pMarine, CBaseEntity *pBiomass )
{
	CASW_Game_Resource *pGameResource = ASWGameResource();
	if ( !pGameResource )
		return;

	//Msg( " Marine burned biomass!\n" );

	// reset intensity so we can have a big fight without relaxing immediately
	for ( int i=0;i<pGameResource->GetMaxMarineResources();i++ )
	{
		CASW_Marine_Resource *pMR = pGameResource->GetMarineResource(i);
		if ( !pMR )
			continue;

		pMR->GetIntensity()->Reset();
	}

	float flQuickStart = RandomFloat( 2.0f, 5.0f );
	if ( m_HordeTimer.GetRemainingTime() > flQuickStart )
	{
		m_HordeTimer.Start( flQuickStart );
	}

	// TODO: Instead have some kind of 'is in a big fight' state?
}

void CASW_Director::StartFinale()
{
	m_bFinale = true;
	m_bHordesEnabled = true;
	m_bWanderersEnabled = true;
	DevMsg("Starting finale\n");

	float flQuickStart = RandomFloat( 2.0f, 5.0f );
	if ( m_HordeTimer.GetRemainingTime() > flQuickStart )
	{
		m_HordeTimer.Start( flQuickStart );
	}
}

void CASW_Director::UpdateMarineInsideEscapeRoom( CASW_Marine *pMarine )
{
	if ( m_bFiredEscapeRoom )
		return;

	// Verify rules and mission manager are available.
	if ( !ASWGameRules() || !ASWGameRules()->GetMissionManager() )
		return;

	// Don't send the escape room output if there are objectives uncompleted.
	CASW_Objective_Escape *pEscape = ASWGameRules()->GetMissionManager()->GetEscapeObjective();
	if ( pEscape && !pEscape->OtherObjectivesComplete() )
		return;

	// Tell all director controls to send an output
	if ( g_pDirectorControl )
	{
		g_pDirectorControl->OnEscapeRoomStart( pMarine );
	}

	m_bFiredEscapeRoom = true;
}

void CASW_Director::OnMissionStarted()
{
	//PJ - Hook in mod_player_performance
	CMOD_Player_Performance::PlayerPerformance()->OnMissionStarted();

	if (ASWSpawnManager())
	{
		ASWSpawnManager()->SelectSpawnSet();
	}

	if (ASWSpawnManager() && m_flPreSpawnAliens > 0 && asw_spawning_enabled.GetBool())
	{
		ASWSpawnManager()->PreSpawnAliens(m_flPreSpawnAliens);
	}
}

redpajama_set_name: RedPajamaGithub


text:
Plasma (physics) (6190 views - Physics)
Plasma (from Ancient Greek πλάσμα, meaning 'moldable substance') is one of the four fundamental states of matter, and was first described by chemist Irving Langmuir in the 1920s. Plasma can be artificially generated by heating or subjecting a neutral gas to a strong electromagnetic field to the point where an ionized gaseous substance becomes increasingly electrically conductive, and long-range electromagnetic fields dominate the behaviour of the matter.Plasma and ionized gases have properties and display behaviours unlike those of the other states, and the transition between them is mostly a matter of nomenclature and subject to interpretation. Based on the surrounding environmental temperature and density, partially ionized or fully ionized forms of plasma may be produced. Neon signs and lightning are examples of partially ionized plasma. The Earth's ionosphere is a plasma and the magnetosphere contains plasma in the Earth's surrounding space environment. The interior of the Sun is an example of fully ionized plasma, along with the solar corona and stars.Positive charges in ions are achieved by stripping away electrons orbiting the atomic nuclei, where the total number of electrons removed is related to either increasing temperature or the local density of other ionized matter. This also can be accompanied by the dissociation of molecular bonds, though this process is distinctly different from chemical processes of ion interactions in liquids or the behaviour of shared ions in metals. The response of plasma to electromagnetic fields is used in many modern technological devices, such as plasma televisions or plasma etching.Plasma may be the most abundant form of ordinary matter in the universe, although this hypothesis is currently tentative based on the existence and unknown properties of dark matter. Plasma is mostly associated with stars, extending to the rarefied intracluster medium and possibly the intergalactic regions.
PARTcloud - plasma
For other uses, see Plasma.
Top: Lightning and neon lights are commonplace generators of plasma. Bottom left: A plasma globe, illustrating some of the more complex plasma phenomena, including filamentation. Bottom right: A plasma trail from the Space Shuttle Atlantis during re-entry into Earth's atmosphere, as seen from the International Space Station.
Plasma (from Ancient Greek πλάσμα, meaning 'moldable substance'[1]) is one of the four fundamental states of matter, and was first described by chemist Irving Langmuir[2] in the 1920s.[3] Plasma can be artificially generated by heating or subjecting a neutral gas to a strong electromagnetic field to the point where an ionized gaseous substance becomes increasingly electrically conductive, and long-range electromagnetic fields dominate the behaviour of the matter.[4]
Plasma and ionized gases have properties and display behaviours unlike those of the other states, and the transition between them is mostly a matter of nomenclature[2] and subject to interpretation.[5] Based on the surrounding environmental temperature and density, partially ionized or fully ionized forms of plasma may be produced. Neon signs and lightning are examples of partially ionized plasma.[6] The Earth's ionosphere is a plasma and the magnetosphere contains plasma in the Earth's surrounding space environment. The interior of the Sun is an example of fully ionized plasma,[7] along with the solar corona[8] and stars.[9]
Positive charges in ions are achieved by stripping away electrons orbiting the atomic nuclei, where the total number of electrons removed is related to either increasing temperature or the local density of other ionized matter. This also can be accompanied by the dissociation of molecular bonds,[10] though this process is distinctly different from chemical processes of ion interactions in liquids or the behaviour of shared ions in metals. The response of plasma to electromagnetic fields is used in many modern technological devices, such as plasma televisions or plasma etching.[11]
Plasma may be the most abundant form of ordinary matter in the universe,[12] although this hypothesis is currently tentative based on the existence and unknown properties of dark matter. Plasma is mostly associated with stars, extending to the rarefied intracluster medium and possibly the intergalactic regions.[13]
2 Properties and parameters
2.2.1 Fully vs. partially (weakly) ionized gases
2.2.2 Thermal vs. nonthermal (cold) plasmas
2.3 Plasma potential
2.4 Magnetization
2.5 Comparison of plasma and gas phases
3 Plasmas in space science and astronomy
4 Common plasmas
5 Complex plasma phenomena
5.1 Filamentation
5.2 Non-neutral plasma
5.3 Dusty plasma/grain plasma
5.4 Impermeable plasma
6 Mathematical descriptions
6.1 Fluid model
6.2 Kinetic model
7 Artificial plasmas
7.1 Generation of artificial plasma
7.1.1 Electric arc
7.2 Examples of industrial/commercial plasma
7.2.1 Low-pressure discharges
7.2.2 Atmospheric pressure
7.3 MHD converters
9 Psychological
10 Research examples
The word plasma comes from Ancient Greek πλάσμα, meaning 'moldable substance'[1] or 'jelly',[2] and describes the behaviour of the ionized atomic nuclei and the electrons within the surrounding region of the plasma. Very simply, each of these nuclei are suspended in a movable sea of electrons. Plasma was first identified in a Crookes tube, and so described by Sir William Crookes in 1879 (he called it "radiant matter").[14] The nature of this "cathode ray" matter was subsequently identified by British physicist Sir J.J. Thomson in 1897.[15]
The term "plasma" was coined by Irving Langmuir in 1928.[16] Lewi Tonks and Harold Mott-Smith, both of whom worked with Irving Langmuir in the 1920s, recall that Langmuir first used the word "plasma" in analogy with blood.[17][18] Mott-Smith recalls, in particular, that the transport of electrons from thermionic filaments reminded Langmuir of "the way blood plasma carries red and white corpuscles and germs."[19]
Langmuir described the plasma he observed as follows:
"Except near the electrodes, where there are sheaths containing very few electrons, the ionized gas contains ions and electrons in about equal numbers so that the resultant space charge is very small. We shall use the name plasma to describe this region containing balanced charges of ions and electrons."[16]
Clausius–Duhem (entropy)
Elasticity (linear)
Finite strain
Infinitesimal strain
Contact mechanics (frictional)
Material failure theory
Fracture mechanics
Statics · Dynamics
Archimedes' principle · Bernoulli's principle
Navier–Stokes equations
Poiseuille equation · Pascal's law
Viscosity (Newtonian · non-Newtonian)
Buoyancy · Mixing · Pressure
Capillary action
Charles's law
Viscoelasticity
Rheometry
Smart fluids
Electrorheological
Magnetorheological
Ferrofluids
Gay-Lussac
Navier
Properties and parameters
Plasma is a state of matter in which an ionized gaseous substance becomes highly electrically conductive to the point that long-range electric and magnetic fields dominate the behaviour of the matter.[21][22] The plasma state can be contrasted with the other states: solid, liquid, and gas.
Plasma is an electrically neutral medium of unbound positive and negative particles (i.e. the overall charge of a plasma is roughly zero). Although these particles are unbound, they are not "free" in the sense of not experiencing forces. Moving charged particles generate an electric current within a magnetic field, and any movement of a charged plasma particle affects and is affected by the fields created by the other charges. In turn this governs collective behaviour with many degrees of variation.[10][23] Three factors define a plasma:[24][25]
The plasma approximation: The plasma approximation applies when the plasma parameter, Λ,[26] representing the number of charge carriers within a sphere (called the Debye sphere whose radius is the Debye screening length) surrounding a given charged particle, is sufficiently high as to shield the electrostatic influence of the particle outside of the sphere.[21][22]
Bulk interactions: The Debye screening length (defined above) is short compared to the physical size of the plasma. This criterion means that interactions in the bulk of the plasma are more important than those at its edges, where boundary effects may take place. When this criterion is satisfied, the plasma is quasineutral.[27]
Plasma frequency: The electron plasma frequency (measuring plasma oscillations of the electrons) is large compared to the electron-neutral collision frequency (measuring frequency of collisions between electrons and neutral particles). When this condition is valid, electrostatic interactions dominate over the processes of ordinary gas kinetics.[28]
Plasma temperature is commonly measured in kelvin or electronvolts and is, informally, a measure of the thermal kinetic energy per particle. High temperatures are usually needed to sustain ionisation, which is a defining feature of a plasma. The degree of plasma ionisation is determined by the electron temperature relative to the ionization energy (and more weakly by the density), in a relationship called the Saha equation. At low temperatures, ions and electrons tend to recombine into bound states—atoms[29]—and the plasma will eventually become a gas.
In most cases the electrons are close enough to thermal equilibrium that their temperature is relatively well-defined; this is true even when there is a significant deviation from a Maxwellian energy distribution function, for example, due to UV radiation, energetic particles, or strong electric fields. Because of the large difference in mass, the electrons come to thermodynamic equilibrium amongst themselves much faster than they come into equilibrium with the ions or neutral atoms. For this reason, the ion temperature may be very different from (usually lower than) the electron temperature. This is especially common in weakly ionized technological plasmas, where the ions are often near the ambient temperature.
Fully vs. partially (weakly) ionized gases
Main article: Degree of ionization
See also: Spitzer resistivity
For plasma to exist, ionisation is necessary. The term "plasma density" by itself usually refers to the "electron density", that is, the number of free electrons per unit volume. The degree of ionisation of a plasma is the proportion of atoms that have lost or gained electrons, and is controlled by the electron and ion temperatures and electron-ion vs electron-neutral collision frequencies. The degree of ionisation, α {\displaystyle \alpha } , is defined as α = n i n i + n n {\displaystyle \alpha ={\frac {n_{i}}{n_{i}+n_{n}}}} , where n i {\displaystyle n_{i}} is the number density of ions and n n {\displaystyle n_{n}} is the number density of neutral atoms. The electron density is related to this by the average charge state[further explanation needed] ⟨ Z ⟩ {\displaystyle \langle Z\rangle } of the ions through n e = ⟨ Z ⟩ n i {\displaystyle n_{e}=\langle Z\rangle n_{i}} , where n e {\displaystyle n_{e}} is the number density of electrons.
In a plasma, the electron-ion collision frequency ν e i {\displaystyle \nu _{ei}} is much greater than the electron-neutral collision frequency ν e n {\displaystyle \nu _{en}} . Therefore, with a weak degree of ionization α {\displaystyle \alpha } , the electron-ion collision frequency can equal the electron-neutral collision frequency: ν e i = ν e n {\displaystyle \nu _{ei}=\nu _{en}} is the limit separating a plasma from being partially or fully ionized.
The term fully ionized gas introduced by Lyman Spitzer does not mean the degree of ionization is unity, but only that the plasma is in a Coulomb-collision dominated regime, i.e. when ν e i > ν e n {\displaystyle \nu _{ei}>\nu _{en}} , which can correspond to a degree of ionization as low as 0.01%.[30]
A partially or weakly ionized gas means the plasma is not dominated by Coulomb collisions, i.e. when ν e i < ν e n {\displaystyle \nu _{ei}<\nu _{en}} .
Most of "technological" (engineered) plasmas are weakly ionized gases.
Thermal vs. nonthermal (cold) plasmas
Main article: Nonthermal plasma
See also: Anisothermal plasma
Based on the relative temperatures of the electrons, ions and neutrals, plasmas are classified as "thermal" or "non-thermal" (also referred to as "cold plasmas").
Thermal plasmas have electrons and the heavy particles at the same temperature, i.e. they are in thermal equilibrium with each other.
Nonthermal plasmas on the other hand are non-equilibrium ionized gases, with two temperatures: ions and neutrals stay at a low temperature (sometimes room temperature), whereas electrons are much hotter. ( T e ≫ T n {\displaystyle T_{e}\gg T_{n}} ).[31] A kind of common nonthermal plasma is the mercury-vapor gas within a fluorescent lamp, where the "electrons gas" reaches a temperature of 10,000 kelvins while the rest of the gas stays barely above room temperature, so the bulb can even be touched with hands while operating.
A particular and unusual case of "inverse" nonthermal plasma is the very high temperature plasma produced by the Z machine, where ions are much hotter than electrons.[32][33]
Plasma potential
Since plasmas are very good electrical conductors, electric potentials play an important role.[clarification needed] The average potential in the space between charged particles, independent of how it can be measured, is called the "plasma potential", or the "space potential". If an electrode is inserted into a plasma, its potential will generally lie considerably below the plasma potential due to what is termed a Debye sheath. The good electrical conductivity of plasmas makes their electric fields very small. This results in the important concept of "quasineutrality", which says the density of negative charges is approximately equal to the density of positive charges over large volumes of the plasma ( n e = ⟨ Z ⟩ n i {\displaystyle n_{e}=\langle Z\rangle n_{i}} ), but on the scale of the Debye length there can be charge imbalance. In the special case that double layers are formed, the charge separation can extend some tens of Debye lengths.[citation needed]
The magnitude of the potentials and electric fields must be determined by means other than simply finding the net charge density. A common example is to assume that the electrons satisfy the Boltzmann relation:
n e ∝ e e Φ / k B T e . {\displaystyle n_{e}\propto e^{e\Phi /k_{B}T_{e}}.}
Differentiating this relation provides a means to calculate the electric field from the density:
E → = ( k B T e / e ) ( ∇ n e / n e ) . {\displaystyle {\vec {E}}=(k_{B}T_{e}/e)(\nabla n_{e}/n_{e}).}
It is possible to produce a plasma that is not quasineutral. An electron beam, for example, has only negative charges. The density of a non-neutral plasma must generally be very low, or it must be very small, otherwise, it will be dissipated by the repulsive electrostatic force.[35]
In astrophysical plasmas, Debye screening prevents electric fields from directly affecting the plasma over large distances, i.e., greater than the Debye length. However, the existence of charged particles causes the plasma to generate, and be affected by, magnetic fields. This can and does cause extremely complex behaviour, such as the generation of plasma double layers, an object that separates charge over a few tens of Debye lengths. The dynamics of plasmas interacting with external and self-generated magnetic fields are studied in the academic discipline of magnetohydrodynamics.[36]
Plasma with a magnetic field strong enough to influence the motion of the charged particles is said to be magnetized. A common quantitative criterion is that a particle on average completes at least one gyration around the magnetic field before making a collision, i.e., ω c e / v c o l l > 1 {\displaystyle \omega _{\mathrm {ce} }/v_{\mathrm {coll} }>1} , where ω c e {\displaystyle \omega _{\mathrm {ce} }} is the "electron gyrofrequency" and v c o l l {\displaystyle v_{\mathrm {coll} }} is the "electron collision rate". It is often the case that the electrons are magnetized while the ions are not. Magnetized plasmas are anisotropic, meaning that their properties in the direction parallel to the magnetic field are different from those perpendicular to it. While electric fields in plasmas are usually small due to the high conductivity, the electric field associated with a plasma moving in a magnetic field is given by E = − v × B {\displaystyle \mathbf {E} =-v\times \mathbf {B} } (where E {\displaystyle \mathbf {E} } is the electric field, v {\displaystyle \mathbf {v} } is the velocity, and B {\displaystyle \mathbf {B} } is the magnetic field), and is not affected by Debye shielding.[37]
Comparison of plasma and gas phases
Plasma is often called the fourth state of matter after solid, liquids and gases, despite plasma typically being an ionized gas.[38][39][40] It is distinct from these and other lower-energy states of matter. Although it is closely related to the gas phase in that it also has no definite form or volume, it differs in a number of ways, including the following:
Electrical conductivity
Very low: Air is an excellent insulator until it breaks down into plasma at electric field strengths above 30 kilovolts per centimeter.[41] Usually very high: For many purposes, the conductivity of a plasma may be treated as infinite.
Independently acting species
One: All gas particles behave in a similar way, influenced by gravity and by collisions with one another. Two or three: Electrons, ions, protons and neutrons can be distinguished by the sign and value of their charge so that they behave independently in many circumstances, with different bulk velocities and temperatures, allowing phenomena such as new types of waves and instabilities.
Velocity distribution
Maxwellian: Collisions usually lead to a Maxwellian velocity distribution of all gas particles, with very few relatively fast particles. Often non-Maxwellian: Collisional interactions are often weak in hot plasmas and external forcing can drive the plasma far from local equilibrium and lead to a significant population of unusually fast particles.
Binary: Two-particle collisions are the rule, three-body collisions extremely rare. Collective: Waves, or organized motion of plasma, are very important because the particles can interact at long ranges through the electric and magnetic forces.
Plasmas in space science and astronomy
Further information: Astrophysical plasma, Interstellar medium, and Intergalactic space
See also: Magnetohydrodynamics
Plasmas are by far the most common phase of ordinary matter in the universe, both by mass and by volume.[42]
Above the Earth's surface, the ionosphere is a plasma,[43] and the magnetosphere contains plasma.[44] Within our Solar System, interplanetary space is filled with the plasma expelled via the solar wind, extending from the Sun's surface out to the heliopause. Furthermore, all the distant stars, and much of interstellar space or intergalactic space is also likely filled with plasma, albeit at very low densities. Astrophysical plasmas are also observed in Accretion disks around stars or compact objects like white dwarfs, neutron stars, or black holes in close binary star systems.[45] Plasma is associated with ejection of material in astrophysical jets, which have been observed with accreting black holes[46] or in active galaxies like M87's jet that possibly extends out to 5,000 light-years.[47]
Common plasmas
Plasmas can appear in nature in various forms and locations, which can be usefully broadly summarised in the following Table:
Common forms of plasma
Artificially produced
Terrestrial plasmas
Space and astrophysical plasmas
Those found in plasma displays, including TV screens.
Inside fluorescent lamps (low energy lighting), neon signs[48]
Rocket exhaust and ion thrusters
The area in front of a spacecraft's heat shield during re-entry into the atmosphere
Inside a corona discharge ozone generator
Fusion energy research
The electric arc in an arc lamp, an arc welder or plasma torch
Plasma ball (sometimes called a plasma sphere or plasma globe)
Arcs produced by Tesla coils (resonant air core transformer or disruptor coil that produces arcs similar to lightning, but with alternating current rather than static electricity)
Plasmas used in semiconductor device fabrication including reactive-ion etching, sputtering, surface cleaning and plasma-enhanced chemical vapor deposition
Laser-produced plasmas (LPP), found when high power lasers interact with materials.
Inductively coupled plasmas (ICP), formed typically in argon gas for optical emission spectroscopy or mass spectrometry
Magnetically induced plasmas (MIP), typically produced using microwaves as a resonant coupling method
Static electric sparks
Capacitively coupled plasmas (CCP)
Dielectric Barrier Discharges (DBD)
The magnetosphere contains plasma in the Earth's surrounding space environment
The ionosphere
The plasmasphere
The polar aurorae
The polar wind, a plasma fountain
Upper-atmospheric lightning (e.g. Blue jets, Blue starters, Gigantic jets, ELVES)
St. Elmo's fire
(plasmas heated by nuclear fusion)
The solar wind
The interplanetary medium
(space between planets)
The interstellar medium
(space between star systems)
The Intergalactic medium
(space between galaxies)
The Io-Jupiter flux tube
Accretion discs
Interstellar nebulae
Complex plasma phenomena
Although the underlying equations governing plasmas are relatively simple, plasma behaviour is extraordinarily varied and subtle: the emergence of unexpected behaviour from a simple model is a typical feature of a complex system. Such systems lie in some sense on the boundary between ordered and disordered behaviour and cannot typically be described either by simple, smooth, mathematical functions, or by pure randomness. The spontaneous formation of interesting spatial features on a wide range of length scales is one manifestation of plasma complexity. The features are interesting, for example, because they are very sharp, spatially intermittent (the distance between features is much larger than the features themselves), or have a fractal form. Many of these features were first studied in the laboratory, and have subsequently been recognized throughout the universe. Examples of complexity and complex structures in plasmas include:
Filamentation
Striations or string-like structures,[49] also known as Birkeland currents, are seen in many plasmas, like the plasma ball, the aurora,[50] lightning,[51] electric arcs, solar flares,[52] and supernova remnants.[53] They are sometimes associated with larger current densities, and the interaction with the magnetic field can form a magnetic rope structure.[54] High power microwave breakdown at atmospheric pressure also leads to the formation of filamentary structures.[55] (See also Plasma pinch)
Filamentation also refers to the self-focusing of a high power laser pulse. At high powers, the nonlinear part of the index of refraction becomes important and causes a higher index of refraction in the center of the laser beam, where the laser is brighter than at the edges, causing a feedback that focuses the laser even more. The tighter focused laser has a higher peak brightness (irradiance) that forms a plasma. The plasma has an index of refraction lower than one, and causes a defocusing of the laser beam. The interplay of the focusing index of refraction, and the defocusing plasma makes the formation of a long filament of plasma that can be micrometers to kilometers in length.[56] One interesting aspect of the filamentation generated plasma is the relatively low ion density due to defocusing effects of the ionized electrons.[57] (See also Filament propagation)
Non-neutral plasma
The strength and range of the electric force and the good conductivity of plasmas usually ensure that the densities of positive and negative charges in any sizeable region are equal ("quasineutrality"). A plasma with a significant excess of charge density, or, in the extreme case, is composed of a single species, is called a non-neutral plasma. In such a plasma, electric fields play a dominant role. Examples are charged particle beams, an electron cloud in a Penning trap and positron plasmas.[58]
Dusty plasma/grain plasma
A dusty plasma contains tiny charged particles of dust (typically found in space). The dust particles acquire high charges and interact with each other. A plasma that contains larger particles is called grain plasma. Under laboratory conditions, dusty plasmas are also called complex plasmas.[59]
Impermeable plasma
Impermeable plasma is a type of thermal plasma which acts like an impermeable solid with respect to gas or cold plasma and can be physically pushed. Interaction of cold gas and thermal plasma was briefly studied by a group led by Hannes Alfvén in 1960s and 1970s for its possible applications in insulation of fusion plasma from the reactor walls.[60] However, later it was found that the external magnetic fields in this configuration could induce kink instabilities in the plasma and subsequently lead to an unexpectedly high heat loss to the walls.[61] In 2013, a group of materials scientists reported that they have successfully generated stable impermeable plasma with no magnetic confinement using only an ultrahigh-pressure blanket of cold gas. While spectroscopic data on the characteristics of plasma were claimed to be difficult to obtain due to the high pressure, the passive effect of plasma on synthesis of different nanostructures clearly suggested the effective confinement. They also showed that upon maintaining the impermeability for a few tens of seconds, screening of ions at the plasma-gas interface could give rise to a strong secondary mode of heating (known as viscous heating) leading to different kinetics of reactions and formation of complex nanomaterials.[62]
Mathematical descriptions
Main article: Plasma modeling
To completely describe the state of a plasma, all of the particle locations and velocities that describe the electromagnetic field in the plasma region would need to be written down. However, it is generally not practical or necessary to keep track of all the particles in a plasma. Therefore, plasma physicists commonly use less detailed descriptions, of which there are two main types:
Fluid model
Fluid models describe plasmas in terms of smoothed quantities, like density and averaged velocity around each position (see Plasma parameters). One simple fluid model, magnetohydrodynamics, treats the plasma as a single fluid governed by a combination of Maxwell's equations and the Navier–Stokes equations. A more general description is the two-fluid plasma picture, where the ions and electrons are described separately. Fluid models are often accurate when collisionality is sufficiently high to keep the plasma velocity distribution close to a Maxwell–Boltzmann distribution. Because fluid models usually describe the plasma in terms of a single flow at a certain temperature at each spatial location, they can neither capture velocity space structures like beams or double layers, nor resolve wave-particle effects.
Kinetic model
Kinetic models describe the particle velocity distribution function at each point in the plasma and therefore do not need to assume a Maxwell–Boltzmann distribution. A kinetic description is often necessary for collisionless plasmas. There are two common approaches to kinetic description of a plasma. One is based on representing the smoothed distribution function on a grid in velocity and position. The other, known as the particle-in-cell (PIC) technique, includes kinetic information by following the trajectories of a large number of individual particles. Kinetic models are generally more computationally intensive than fluid models. The Vlasov equation may be used to describe the dynamics of a system of charged particles interacting with an electromagnetic field. In magnetized plasmas, a gyrokinetic approach can substantially reduce the computational expense of a fully kinetic simulation.
Artificial plasmas
Most artificial plasmas are generated by the application of electric and/or magnetic fields through a gas. Plasma generated in a laboratory setting and for industrial use can be generally categorized by:
The type of power source used to generate the plasma—DC, AC (typically with radio frequency (RF)) and microwave
The pressure they operate at—vacuum pressure (< 10 mTorr or 1 Pa), moderate pressure (≈1 Torr or 100 Pa), atmospheric pressure (760 Torr or 100 kPa)
The degree of ionisation within the plasma—fully, partially, or weakly ionized
The temperature relationships within the plasma—thermal plasma ( T e = T i = T g a s {\displaystyle T_{e}=T_{i}=T_{gas}} ), non-thermal or "cold" plasma ( T e ≫ T i = T g a s {\displaystyle T_{e}\gg T_{i}=T_{gas}} )
The electrode configuration used to generate the plasma
The magnetization of the particles within the plasma—magnetized (both ion and electrons are trapped in Larmor orbits by the magnetic field), partially magnetized (the electrons but not the ions are trapped by the magnetic field), non-magnetized (the magnetic field is too weak to trap the particles in orbits but may generate Lorentz forces)[citation needed]
Generation of artificial plasma
Just like the many uses of plasma, there are several means for its generation, however, one principle is common to all of them: there must be energy input to produce and sustain it.[64] For this case, plasma is generated when an electric current is applied across a dielectric gas or fluid (an electrically non-conducting material) as can be seen in the adjacent image, which shows a discharge tube as a simple example (DC used for simplicity).
The potential difference and subsequent electric field pull the bound electrons (negative) toward the anode (positive electrode) while the cathode (negative electrode) pulls the nucleus.[65] As the voltage increases, the current stresses the material (by electric polarization) beyond its dielectric limit (termed strength) into a stage of electrical breakdown, marked by an electric spark, where the material transforms from being an insulator into a conductor (as it becomes increasingly ionized). The underlying process is the Townsend avalanche, where collisions between electrons and neutral gas atoms create more ions and electrons (as can be seen in the figure on the right). The first impact of an electron on an atom results in one ion and two electrons. Therefore, the number of charged particles increases rapidly (in the millions) only "after about 20 successive sets of collisions",[66] mainly due to a small mean free path (average distance travelled between collisions).
Cascade process of ionisation. Electrons are "e−", neutral atoms "o", and cations "+".
With ample current density and ionisation, this forms a luminous electric arc (a continuous electric discharge similar to lightning) between the electrodes.[Note 1] Electrical resistance along the continuous electric arc creates heat, which dissociates more gas molecules and ionises the resulting atoms (where degree of ionisation is determined by temperature), and as per the sequence: solid-liquid-gas-plasma, the gas is gradually turned into a thermal plasma.[Note 2] A thermal plasma is in thermal equilibrium, which is to say that the temperature is relatively homogeneous throughout the heavy particles (i.e. atoms, molecules and ions) and electrons. This is so because when thermal plasmas are generated, electrical energy is given to electrons, which, due to their great mobility and large numbers, are able to disperse it rapidly and by elastic collision (without energy loss) to the heavy particles.[67][Note 3]
Examples of industrial/commercial plasma
Because of their sizable temperature and density ranges, plasmas find applications in many fields of research, technology and industry. For example, in: industrial and extractive metallurgy,[67][68] surface treatments such as plasma spraying (coating), etching in microelectronics,[69] metal cutting[70] and welding; as well as in everyday vehicle exhaust cleanup and fluorescent/luminescent lamps,[64] fuel ignition, while even playing a part in supersonic combustion engines for aerospace engineering.[71]
Low-pressure discharges
Glow discharge plasmas: non-thermal plasmas generated by the application of DC or low frequency RF (<100 kHz) electric field to the gap between two metal electrodes. Probably the most common plasma; this is the type of plasma generated within fluorescent light tubes.[72]
Capacitively coupled plasma (CCP): similar to glow discharge plasmas, but generated with high frequency RF electric fields, typically 13.56 MHz. These differ from glow discharges in that the sheaths are much less intense. These are widely used in the microfabrication and integrated circuit manufacturing industries for plasma etching and plasma enhanced chemical vapor deposition.[73]
Cascaded Arc Plasma Source: a device to produce low temperature (≈1eV) high density plasmas (HDP).
Inductively coupled plasma (ICP): similar to a CCP and with similar applications but the electrode consists of a coil wrapped around the chamber where plasma is formed.[74]
Wave heated plasma: similar to CCP and ICP in that it is typically RF (or microwave). Examples include helicon discharge and electron cyclotron resonance (ECR).[75]
Arc discharge: this is a high power thermal discharge of very high temperature (≈10,000 K). It can be generated using various power supplies. It is commonly used in metallurgical processes. For example, it is used to smelt minerals containing Al2O3 to produce aluminium.
Corona discharge: this is a non-thermal discharge generated by the application of high voltage to sharp electrode tips. It is commonly used in ozone generators and particle precipitators.
Dielectric barrier discharge (DBD): this is a non-thermal discharge generated by the application of high voltages across small gaps wherein a non-conducting coating prevents the transition of the plasma discharge into an arc. It is often mislabeled 'Corona' discharge in industry and has similar application to corona discharges. It is also widely used in the web treatment of fabrics.[76] The application of the discharge to synthetic fabrics and plastics functionalizes the surface and allows for paints, glues and similar materials to adhere.[77] The dielectric barrier discharge was used in the mid-1990s to show that low temperature atmospheric pressure plasma is effective in inactivating bacterial cells.[78] This work and later experiments using mammalian cells led to the establishment of a new field of research known as plasma medicine. The dielectric barrier discharge configuration was also used in the design of low temperature plasma jets. These plasma jets are produced by fast propagating guided ionisation waves known as plasma bullets.[79]
Capacitive discharge: this is a nonthermal plasma generated by the application of RF power (e.g., 13.56 MHz) to one powered electrode, with a grounded electrode held at a small separation distance on the order of 1 cm. Such discharges are commonly stabilized using a noble gas such as helium or argon.[80]
"Piezoelectric direct discharge plasma:" is a nonthermal plasma generated at the high-side of a piezoelectric transformer (PT). This generation variant is particularly suited for high efficient and compact devices where a separate high voltage power supply is not desired.
MHD converters
Main articles: magnetohydrodynamic converter, magnetohydrodynamic generator, and magnetohydrodynamic drive
See also: Electrothermal instability
A world effort was triggered in the 1960s to study magnetohydrodynamic converters in order to bring MHD power conversion to market with commercial power plants of a new kind, converting the kinetic energy of a high velocity plasma into electricity with no moving parts at a high efficiency. Research was also conducted in the field of supersonic and hypersonic aerodynamics to study plasma interaction with magnetic fields to eventually achieve passive and even active flow control around vehicles or projectiles, in order to soften and mitigate shock waves, lower thermal transfer and reduce drag.
Such ionized gases used in "plasma technology" ("technological" or "engineered" plasmas) are usually weakly ionized gases in the sense that only a tiny fraction of the gas molecules are ionized.[81] These kinds of weakly ionized gases are also nonthermal "cold" plasmas. In the presence of magnetics fields, the study of such magnetized nonthermal weakly ionized gases involves resistive magnetohydrodynamics with low magnetic Reynolds number, a challenging field of plasma physics where calculations require dyadic tensors in a 7-dimensional phase space. When used in combination with a high Hall parameter, a critical value triggers the problematic electrothermal instability which limited these technological developments.
Plasmas are the object of study of the academic field of plasma science or plasma physics,[82] including sub-disciplines such as space plasma physics. It currently involves the following fields of active research and features across many journals, whose interest includes:
Plasma theory
Plasma equilibria and stability
Plasma interactions with waves and beams
Guiding center
Adiabatic invariant
Debye sheath
Coulomb collision
Plasmas in nature
Astrophysical plasma
Northern and southern (polar) lights
The Earth's ionosphere
Interplanetary medium
Planetary magnetospheres
Space plasma
Industrial plasmas
Plasma chemistry
Plasma processing
Plasma spray
Dusty plasmas
Plasma diagnostics
Thomson scattering
Langmuir probe
Ball-pen probe
Faraday cup
Ionospheric heating
Incoherent scatter radar
Plasma applications
Fusion power
Magnetic fusion energy (MFE) —
Stellarator
Reversed field pinch
Magnetic mirror
Dense plasma focus
Inertial confinement fusion (ICF)
Plasma weapons
Ion implantation
Ion thruster
MAGPIE (Implosion experiments)
Plasma ashing
Nonthermal plasma or "cold plasma"
Plasma arc waste disposal, recycling.
Plasma acceleration
Plasma medicine (e. g. Dentistry[83])
Plasma window
Research indicates that magnetic fields created by plasma during a thunderstorm can induce hallucination in the human mind.[84] A declassified Ministry of Defense report states that it is "medically proven" that magnetic fields related to plasma cause hallucinations and that "the close proximity of plasma-related fields can adversely affect a vehicle or person".[85] The report also indicated that scientists in the former Soviet Union are pursuing related technology for military purposes.
Research examples
Hall effect thruster. The electric field in a plasma double layer is so effective at accelerating ions that electric fields are used in ion drives.
Solar plasma
Plasma spraying
Tokamak plasma in nuclear fusion research
Physics portal
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This article uses material from the Wikipedia article "Plasma (physics)", which is released under the Creative Commons Attribution-Share-Alike License 3.0. There is a list of all authors in Wikipedia
Physics, science