Rabbi Binyamin (Benny) Lau is Rabbi of the Ramban Synagogue in Jerusalem, and one of the leaders of the Bet Morasha Torah Study Center. A noted author and lecturer, this article was originally presented as a lecture at his synagogue. It was published in De'ot, the journal of Neemanei Torah vaAvodah, in the June 2010 issue. It was translated into English for the Institute for Jewish Ideas and Ideals by Sarah Nadav, and is published with the permission of Rabbi Lau and Neemanei Torah vaAvodah.
Today's religious community suffers from a lack of confidence and a perpetual fear in the face of the compelling outside world and its influences. This inevitably gives rise to a search for protection and dependency upon role models who will show the way and protect our children from any doubt. As a result, the religious educational system encourages obedience to the Torah sages and their authority.
But this search for great leaders capable of guiding us in a world laden with doubts and quandaries has led to weakness, and submission to the opinions of a handful of charismatic leaders.
Many of our children have become dependent on role models in yeshivot and midrashot due to the fact that Religious Zionism has sought to emulate the Hareidi doctrine, which is increasingly dominating the religious way of life and outlook. The message of this essay is to encourage education toward independent thinking, individual empowerment and personal freedom through the wisdom of the Torah and its sages. Independent thinking is not innate; therefore, it must be patiently and laboriously nurtured in our homes and schools so that upon maturity our people will be capable of carrying the burden of human independence in which responsibility and authority are so deeply intertwined.
Armed with the knowledge that no single person is omnipotent-- that no one, however great, is as "holy" as the Torah itself or is meant to lord over us--we must encourage every teacher and every parent to free our children of this heavy burden. They must be given the tools to recognize and fortify their own strength. We must once again imbue the acceptance of responsibility and decision making in our children; granted, their surroundings are complex and the temptations are great, but there is no other way. It is impossible to flee from freedom and choose slavery in its place.
In the spirit of personal integrity and individual freedom Rabbi Kook wrote: "The virtuous man should believe in his life, and in his feelings which take the path of the righteous because that is how his spirit directs him. Because these are good and honest feelings, they naturally lead towards a path of righteousness." This is a most important lesson: have no fear, you need to have faith and trust in yourself. When it comes to most decisions in life, there is no need to consult with a Rabbi or a Rebbe. Individuals, couples and families should make their own decisions in regard to themselves. These are the parties that should make such resolutions. External entities should not and cannot control a person's private life.
Common decency is the basis of the social infrastructure. There is a general code of conduct and legitimate norms of behavior, as well as conduct that is considered unacceptable. So when the sages instruct us to "blunt the teeth" of the wicked son, it is in the sense of education and refinement - to remove the barbs and sarcasm from his speech. But the truly problematic son is the one that "does not know how to ask" or perhaps thinks that it is forbidden to ask.
The Haggada instructs us: "It is up to you to discuss this with him," or in the words of Rabbi Shelomo Alkabetz, (a Kabalist of 16th century Safed): "You must be confident in him" – thanks to your trust in him and his strength, his ray of light will burst forth."
A. "Choose for yourself a Rabbi" - This is the categorical imperative for every religious individual who strives to be a normative member of the religious world and does not know how to choose between different alternatives in the world of halakha.
B. "Acquire for yourself a friend"- This is what distinguishes between the person as an individual and the person as part of the community. R. Gamliel seeks to establish a kind of collective responsibility, which is the basis for a God worshipping community.
C. "Remove yourself from doubt" - This concept is the reason for the two preceding statements. In a world of doubt, the individual seeks meaning and direction. The choice of a Rabbi and being part of a community relieve a person of doubt; he is then free of this onus and can make his way through the world without questions or errors.
.If in the days of R. Gamliel - the time of the rise of Christianity and differences of opinions - there lurked a fear of the prevalence of doubt, then what are we to say when it comes to the modern world, or even more so in the post-modern world? Indeed, it is due to this awareness that the words of R. Gamliel have been given the utmost importance.
Take for example the teaching of the Ramhal in his famous parable from "The Garden of Confusion," which appears in Messilat Yesharim. The Ramhal describes a man who has lost his way in the garden's mazes until his eyes are opened by a sage who knows his way through the garden.
Most of the religious community's instruction books are based on this approach. Instead of getting lost and wandering along the dusty paths in the thick forest, it is best for us to latch on to the great trees and to let others who are familiar with the path guide us.
In my humble opinion, this is the stage where faithful students and believers turn into mindless and unquestioning masses. This type of education leads to slavery due to the dread of the garden of confusion.
"Acquire for yourself an understanding heart", said R Elazar ben Azariah.
Rabbi Gamliel sought to introduce discipline and obedience to the House of Study and the world of Torah, fearing the forces that might shatter the existing hegemony.
R. Elazar's teachings stand in direct opposition to this approach - he strove to fill the House of Study with as much strength as possible, to occupy it with all those who wished to enter and to cope with any doubts that might arise in the House of Study in other ways.
The above mentioned citation from Ecclesiastes describes the Torah in agricultural terms. A goad is a stick with nails attached to it that is used by farmers to prod a working animal so that it will move faster and continue walking in the furrows. As a metaphor, the goad is the "teacher for the cow"; although the goad hurts the animal, its true purpose is to ensure that the animal actually does what it is supposed to do. The nail that is affixed to the end of the goad represents the "leaders of the community", those who guide the community in the service of God and keep them on the path of righteousness.
In simple terms, it is possible to understand this parable as a justification for the use of the discipline which Torah teachers espouse. The words of the sages are not always pleasant but they are intended to improve humankind and the human condition, which is to say that they guide them into the "furrow", the furrow being the path of serving God. This is a good parable for any farmer who has had the experience of having to direct livestock. But R. Elazar is seeking to add another dimension of understanding. According to his explanations, the nail is not a static object. He likens it to a tree that is planted in the ground rather than simply hammered into place; he is trying to communicate that with the proper care, this "goad" can blossom and grow and in this way he is portraying the world of halakha (religious law) and its enormous complexity.
Just as a nail affixes two things to each other, so to halakha affixes the Torah to our life and does not allow people to stray off its path, thereby protecting them from the perils of the journey. Torah evolves with the path and is not static, constantly being renewed. It is nailed, and it is "planted"-- which means it has the opportunity to grow and does not allow the journey to tear us apart.
The passage goes on to describe the planted nail as "Masters of Assembly" (scholars of the community). Rabbi Elazar uses the expression "Masters of Assembly" as a colorful description of the new world he envisions for the House of Study after he has taken over, where students are coming by the hundreds and thousands to learn Torah, without any fear of conflicting opinions or pre-existing notions. "They sit as groups, and in those groups they learn Torah. (All positions will be respected). Some will say that something is ritually pure, and some say it is impure. Others will say that something is permitted and some will say that it is not permitted; or (some will say that) something is fit and (others will say that) something is unfit." This is the vision of the house of learning in the eyes of R Elazar.
Now we have a question which begs to be asked: "Perhaps a man will say "How can I ever learn Torah" (and understand it precisely when every issue is subject to question)? When a person enters the world of open learning, he realizes that there are many variations, and it is possible to "lose one's head". How is it possible to guide a person with questions in a world of plurality? The answer that comes from the house of study of Rabbi Gamliel is: "Choose for yourself a Rabbi and remove yourself from doubt." In a world of uncertainty, the only way for a person to find his way is to ask a guide and then adhere to what he says.
However R. Elazar provides an alternative response to that of R. Gamliel. R. Elazar seeks to place the burden of responsibility on the individual him/herself. Instead of saying "choose a Rabbi for yourself," he cites another teaching which says "Make you ear like a funnel", where a lot of grain can be poured in at one time but little can come out. The source of the word "afarkeset (funnel)" is from Greek, meaning a funnel that is wide open to receive, but has only a narrow opening at the end. The wide end is able to receive many voices which are sailing through the void. The funnel receives and absorbs all of the voices without censoring them. R. Elazar seeks to free your ears from its bonds and tells you to make them open to receive all of the voices. This includes the opinions of those who forbid and those who permit; those who find guilt and those who relieve from guilt; those who declare something impure and those who declare it pure. All of the voices of dispute or disagreement in the House of Study have their source at Mt. Sinai. Only when you are able to listen to all of them, is it possible to begin seeking the right path.
In many places in the Talmud, we come across glorification of the image of sages by their pupils and the surrounding community, as well as explicit criticism of this phenomenon. One of the significant figures exalted in his own time was Rabbi Yehuda HaNasi. There are numerous illustrative stories concerning the criticism of scholars who disagreed with this cult of personality. One of the most famous is the story of the visit to Rabbi Yehuda HaNasi's House of Study by Rabbi Yishma'el – son of Rabbi Yossi ben Halafta. The Talmud describes the pupil's entrance into House of study. Everyone is seated, the Sage takes his place, and only Rabbi Yishma'el – who was very large – is still pacing slowly from one edge of the hall to the other to find a place. In his pacing, it looked as if he were walking over the heads of the other pupils. Rabbi Avdan, Rabbi Yehuda HaNasi's assistant, was furious and he objected.
R. Avdan said: Who is the person walking over the heads of the holy congregation?
R.Yishmael answered: It is I, Yishma'el son of Rabbi Yossi who has come to learn Torah from the Rabbi.
R. Avdan said to him: Are you worthy enough to learn Torah from the Rabbi?
R. Yishmael answered: Was Moses worthy enough to learn Torah from the mouth of the Almighty?
R. Avdan said: Do you think you are Moses?
Here we have a precise description of the House of Study of the time (at least from the viewpoint of the Talmudic author). The scholars sit in rows and the sage sits in front on a dais. Those closest to the sage advance to the front to find their seat. Rabbi Avdan's condescending attitude toward Rabbi Yishma'el exemplifies an elitist and insulting atmosphere in the House of Study.
The gap between the level of a student and the level of a teacher is not a reason to prohibit entrance into the House of Study. When R.Avdan continues to insult Rabbi Yishma'el by asking arrogantly "Do you think you are Moses?" Rabbi Yishmael answers pointedly "And is your Rabbi God?" The atmosphere around Rabbi Yehuda HaNasi had turned him into a God-like figure, but Rabbi Yishma'el pointed out how faulty that environment was.
A similar pattern is evident in the story of Rabbi Hunah's passing. Rabbi Hunah was the most prominent among the Sages in the second generation at the yeshiva of Surah, and held the position of head Rabbi for forty years.
In a number of places in the Talmudic literature, we learn of a disagreement between Rabbi Hunah and Rabbi Hisdah, one of the Rabbi's prominent students. Based on this disagreement we can understand what unfolded at Rabbi Hunah's funeral, when Rabbi Hisdah arose as the new leader and most prominent Rabbi in his generation.
When Rabbi Hunah passed away, there were those who wanted to place a Torah scroll on his bed.
Rabbi Hisdah stated: This was a practice with which he did not agree when he was alive and now you want to do it to him (when he is dead)?
His bed could not exit the front door. Some thought of taking it out through the roof.
Said Rabbi Hisdah: "Indeed I learned from him (Rabbi Hunah) – a sage is honored by exiting through the front door".
They wanted to change his bed to another.
Said Rabbi Hisdah: "So I learned from him – a sage is honored by staying in his first bed." (So) they broke the front door and took him out from there.
Rabbi Abba exclaimed: It was appropriate for the Divine spirit to be bestowed upon our Rabbi (Rabbi Hunah), but his location in Babylonia made him unfit.
In the ensuing discussion, Rabbi Hisdah maintains that they must stick to the procedure of taking the deceased out of the house, insisting he be taken out properly like a sage through the door and not through the roof, on his first bed and not after moving him to a second one (something he deduced from the Ark of the Covenant).
Rabbi Hisdah's sons are also at the funeral, and children are known to repeat what they hear at home. When they hear Rabbi Abba lamenting that the only reason Rabbi Hunah did not "receive the divine spirit" (i.e. prophecy) was due to the fact that he lived outside the land of Israel in Babylonia, they retort that the prophet Ezekiel was living in Babylonia when he received his prophesies.
There are many other stories about the relationship between parents and children, and between teachers and pupils. In many instances, they carry an overt or covert message about the importance of the empowerment of the child or the pupil, discouraging their subjugation to the image of the father or teacher.
For example, there are a number of stories about the personality of Rabbi Yehuda bar Yehezkel – the head of the Pumbedita yeshiva, and his relationship with his father, his rabbis and colleagues. Rabbi Yehuda is described as a person who did not hesitate to contradict his father or rabbi when he believed they erred in their teaching or deeds, and even to banish one of his scholarly friends who had "gone bad".
There is a well known story of the destruction of the House of Study in Tiberius, following the terrible argument of Rabbi Yohanan with his son-in-law and student Resh Lakish. The story vividly describes the ideal House of Study as seen by Rabbi Yohanan. Rabbi Yohanan believes that the proper decorum in a House of Study is that the rabbi speaks, the pupils ask questions, and the rabbi concludes by answering all the questions. This is an idyll of authority which recognizes the position of the student only as one who understands and repeats the words of the teacher.
The moment a pupil dares to challenge this scenario, Rabbi Yohanan has no tolerance for him and says "Robbers know only to rob".
The rabbi is ready for questions but not for opposing ideas. The clear message of this story is that when a rabbi suppresses the pupil's independent thinking and development, then he is destroying the very school he teaches in.
In sum, we may assert that the Talmudic tradition clearly upholds the opinion of Rabbi Elazar ben Azaryah. The Rabbi should demand each of us to develop his/her own judgment and knowledge, and to grow in defining and realizing the image of God which is in each and every one of us.
The traditional literature of the early and later sages encourages independent thinking and enables development of self judgment and knowledge even at the price of disagreement with "Gedolim" (scholarly leaders). Below are a few examples.
"And I am here with my desire to be a pupil of the early sages, to abide by their rules and to wear them as bracelets and necklaces, and not to be a simple donkey carrying books. I will judge according to the way I see fit and according to the clear religious law, I will not prefer one over the other in the name of the Torah, because God will provide wisdom in all times, and will not hold back the good from those who walk in His footsteps with an honest heart."
"I want to address people who speak out about how one shouldn't contradict the books of the sages, and when they see a new book that has opinions that differ [with earlier opinions of sages] they immediately start to squawk like a bird. Any person who is well versed knows that arguments are the way all our rabbis debated since the early days and till the last of the judges…And Rabbi Yeshayah Mitrani said in the Responsa Harid (no. 62) 20: Anything which I don't agree to, I don't hesitate to speak my opinion according to my limited knowledge, and I will speak up against kings and not be ashamed. And I rule according to my knowledge just like philosophers, who once asked one of their most prominent: we acknowledge that those who came before us were greater than we are and yet we contradict their sayings in many places and we know the truth is with us; how can this be? He answered: Who can see further, the giant or the dwarf? You might say the giant, since he is taller and so can see further. But if you put the dwarf on the giant's shoulders, who will be able to see further? You must say the dwarf, since his eyes are now higher that the giant's. So are we, dwarfs standing on the shoulders of the giants who came before us, since we learned from their wisdom and we add to it from our own perspective; it is not because we are greater than they are.And I have also seen written by the Gaon Reb Haim of Volozhin in his book Ruah Haim (chapter 141 of Avot, mishna 4): "And a pupil is prohibited to accept his rabbi's view when he has questions about it, and sometimes the truth will be with the pupil just as a small twig can light up a mighty tree…"
One cannot read these words without feeling frustrated over the culture of silencing and subjugating Torah scholars which is rife today. There are scholars who are afraid to voice opinions which contradict the leading decision makers of our time. Even Rabbi Ovadia himself did not say a word against the Lithuanian extremism on the issue of conversions. He did not come out against the ridiculous idea of moving the new critical ER wing for the Barzilai Hospital in Ashkelon far from the hospital due to dubious pagan gravesites on the premises. Also he did not voice his opinion in any vital matter of religious law which contradicts the rulings of Rabbi Elyashiv and his followers.
The silencing of Torah scholars is spiritual violence. It breeds shallowness and dependence that affect our religious lives in every way. The Hareidi violence against anyone who does not abide by the rulings of the "leaders of the generation" reached new and shocking heights in the matter of canceling the conversions done by officials in the Religious High Court (Beit HaDin Hagadol). Rabbi Sherman's outrageous ruling defined Rabbi Drukman and the official religious court as a "court of criminals" just because he would not yield to the rulings of the so-called "leaders" of the Hareidi community who supposedly "speak in the name of the Torah". We have reached an ugly abyss of Hareidi leadership and there is nothing left but to rise up against it. This is not the Torah we know, this is not our viewpoint and these are not our leaders.
Our children need to hear us cry out against the violence and the silencing of opposing opinions. We need to shout: "This is not the way of the Torah! We believe in God and His Torah and we refuse to bow down to this dreadful "papacy". We must strengthen each other in our belief in God and the Torah, and strengthen our trust in honesty and the righteousness of our children.
Bavli Yevamot, 106; Jonah Frenkel in his book "Insights into the Spiritual World of Agada Stories" (Tel Aviv, 1991, pages 78-82), analyzes our story. Amongst others he brings the Halacha which states "sons of sages and pupils, when the public needs them, they step over the heads of the leaders".
#_ednref2" name="_edn2" title="">Bavli, Moed Katan, 25 page 1. Translated to Hebrew according to Steinzaltz.


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I have been going through the archives and posting up these golden oldies recently. Here's Pastor Kevin and Esthers wedding in City Harvest Church (CHC), Subang Jaya. When they asked me to be their wedding photographer I didn't realise that I was going to end up covering weddings for almost the entire leadership team. City Harvest Church has moved into a newer, larger and nicer lit building. These photos were taken in the old windowless "blue cave" church with the Canon 20D, Nikon D2h, and Nikon D70. Back then these were considered the wedding cameras of choice but it was challenging. The new generation of cameras have changed things quite a bit!


text:
Need A Way Out Of Black Hole? Ask Stephen Hawking
Aashish Sharma
Short Bytes: According to a new theory hypothesized by Hawking, the information can be retrieved back from the Black Holes. "If you feel you are in a black hole, don't give up. There's a way out", says Stephen Hawking.
Black Holes suck, well, literally- and everybody knows that. If light is unable to zip past the monstrous gravitational force, there is no chance that anyone else could, right? Well, Stephen Hawking thinks otherwise.
Arguably, one of the greatest physicist alive who tried to explain how universe works, has given yet another theory dismissing the previously held notion that Back Holes are the eternal suction machines. "If you feel you are in a black hole, don't give up. There's a way out," advises Stephen Hawking at a public lecture in Stockholm, Sweden.
Black Hole theories face a paradox when explained as per the Quantum Mechanics and General Relativity respectively. Quantum mechanics articulates that the information can not be destroyed, even inside the Black Hole- whereas, the theory of General Relativity suggests contrarily.
But, according to the new theory hypothesized by Hawking, the information never gets inside the black hole, but lingers on the event horizon, its boundary. Hawking suggests at the KTH Royal Institute of Technolgy that the information about particles passing through is translated into a kind of hologram – a 2D description of a 3D object – that sits on the surface of the event horizon. The holograms contain all the information that otherwise would be lost.
However, Hawking mentioned that the information emitted out of the black hole in the form of photons would be almost impossible to discern. Stephen Hawking, who recently collaborated with Russian billionaire Yuri Milner with an investment of $100 million to search for extra-terrestrials, has given the theory which would be later explained when Hawking and his team will publish their research.
The research also hints at the existence of the parallel universes streaming out of the other end of the black holes.
Having something to add? Tell us in the comments below.
Also Read: How the Universe Works: Stephen Hawking's Theory of Everything, Explained in 150 Seconds
Racing towards the dream - however, he's just a ping away - find him at Facebook or send him an email.

redpajama_set_name: RedPajamaCommonCrawl


This past Monday was the first of many primary elections to take place in the US. The big winners, according to the Newton Inquirer, were Martin O'Malley (Democrat) and Mike Huckabee (Republican).
In his speech following the release of the results, O'Malley said, "I would like to thank the people of Newton, Iowa, or as I like to call them, Fig Newtons, for their support in electing me as the President of the United States".
Standing next to O'Malley was his political advisor, who, after O'Malley made this statement, leaned over and whispered something in O'Malley's ear.
He then moved his body back in front of the podium and stated, "I was just told by my political advisor that this was not the national election, and only a caucus. What are those? I am not sure what that means, but I am assuming that that means that you guys just elected me leader of the world. I would like to thank the academy for their support".
"I once again stand corrected and I now feel really embarrassed and I believe that now would be a good time to suspend my bid for the presidency of 2016. Yet, while I have your attention, I would like to announce my presidential bid for the 2017 presidential elections. My slogan will be, 'Choose O'Malley, because, well, why not?'".
We had a reporter on the scene who interviewed the last remaining audience member on why she supported O'Malley. "it's a mother's job to support her son no matter how much he screws up" she said.
In a similar fashion, Mike Huckabee, the Newton Caucus winner, actually gave a similar speech Monday night as well.
He began the speech by saying that he is looking forward to beating O'Malley in the general election in the town of Newton, which he accidentally called "Neutron", thinking of his favorite television show, Jimmy Neutron.
After the caucuses were finished, O'Malley and Huckabee were seen at a local Chuck E. Cheese's fighting in the ball pit over a toy won at the prize stand for 10 tickets. Luckily, the signature Chuck E. Cheese show in the dining room began in the middle of their fight. Hypnotized by the dancing mouse, they resolved their issues and proceeded to the show's audience.
With them out of the race, who will win the bid for the White House? Only time will tell.


Echolocation allows bats to orient and localize prey in complete darkness. The sonar beam of the big brown bat, Eptesicus fuscus, is directional but broad enough to provide audible echo information from within a 60–90 deg. cone. This suggests that the big brown bat could interrogate a natural scene without fixating each important object separately. We tested this idea by measuring the directional aim and duration of the bat's sonar beam as it performed in a dual task, obstacle avoidance and insect capture. Bats were trained to fly through one of two openings in a fine net to take a tethered insect at variable distances behind the net. The bats sequentially scanned the edges of the net opening and the prey by centering the axis of their sonar beam with an accuracy of ∼5 deg. The bats also shifted the duration of their sonar calls, revealing sequential sampling along the range axis. Changes in duration and directional aim were correlated, showing that the bat first inspected the hole, and then shifted its gaze to the more distant insect, before flying through the net opening. Contrary to expectation based on the sonar beam width, big brown bats encountering a complex environment accurately pointed and shifted their sonar gaze to sequentially inspect closely spaced objects in a manner similar to visual animals using saccades and fixations to scan a scene. The findings presented here from a specialized orientation system, echolocation, offer insights into general principles of active sensing across sensory modalities for the perception of natural scenes.
Animal sensory systems are continuously bombarded by environmental input, which must be selectively processed to enable effective use of information for species-specific behaviors in complex and noisy environments. Sensory information may be filtered already at the receptor level in simple systems (e.g. Nilsson et al., 2005) or by bottom up and top down processes in the central nervous system (Bartels and Zeki, 1998; Mitchinson et al., 2007). Visually dominant animals tend to sequentially sample information by moving their eyes or head to selectively fixate stimuli at the fovea or visual streak (Liversedge and Findlay, 2000; Eckmeier et al., 2008).
The echolocating bat presents an excellent animal model for exploring whether sequential stimulus sampling extends to modalities beyond vision. Bats produce ultrasonic vocalizations, and use information carried by sonar echoes to forage and avoid obstacles (Popper and Fay, 1995). Moreover, bats adaptively control the features of the sonar sounds they use to probe the environment, and these signals can be quantitatively analyzed to measure and model changes tied to perception. Previous studies of echolocation in an open environment show that the big brown bat locks its sonar beam onto a prey item hundreds of milliseconds before capture (Ghose and Moss, 2003). The present study extended this work to measure the big brown bat's sonar beam-directing behavior in a more complex environment that included both obstacles and prey.
When an echolocating bat seeks insect prey in the proximity of vegetation, because of the broadness of the sonar beam, each vocalization results in a cascade of echoes, arriving from different directions and at different delays. Field observations document that echolocating bats cope with acoustic clutter by adapting the spectro-temporal characteristics of sonar signals to decrease the duration and broaden the bandwidth of individual calls and increase the repetition rate in groups of calls (Schnitzler et al., 2003; Surlykke and Moss, 2000). These vocal-motor strategies are assumed to sharpen information about the features and location of prey and to segregate prey echoes from clutter echoes. In humans, sound frequency and pitch are particularly important for parsing an auditory scene (Bregman, 1990), but such cues may not be as useful for the echolocating bat, as its sonar calls constrain the echo frequency information, and ambiguous spectral information can arise from the overlap of echoes from multiple closely spaced objects. Thus, we hypothesize that spatial cues about object direction and distance play a prominent role in the big brown bat's analysis of auditory scenes. Furthermore, we hypothesize that the big brown bat's perception of a complex environment depends on its active control over sonar vocalizations to enhance spatial information about the direction and distance of multiple objects. This is the focus of the present study.
In the experiments reported here, we required echolocating bats to perform a dual task, obstacle avoidance and prey capture. Using high-speed stereo videography and synchronized sound recordings with a microphone array, we measured the directional aim of the big brown bat's sonar beam pattern in the free-flying animal. The big brown bat's sonar beam is wide enough to generate audible echoes simultaneously from multiple objects, and we conducted this study to determine whether the animal's beam-directing behavior is consistent with sequential or simultaneous sampling of sonar targets. Studies of eye movements reveal that humans sequentially foveate parts of a visual scene, even when features, such as those of a face, may be closely spaced (Land and Hayhoe, 2001; Kumar et al., 2005). The width of the sonar beam suggests that the big brown bat does not need to scan closely spaced objects sequentially, because all objects within as much as 30 deg. off the beam axis return echoes of comparable strength.
We report here, however, that the big brown bat does sample the environment sequentially with its sonar, adjusting the direction and distance of its acoustic gaze to closely spaced objects in a complex environment. This is an important finding, because it indicates that sequential scanning offers the animal an advantage that would not be predicted from the characteristics of the sonar beam and implies higher spatial resolution along the midline of the sonar receiver.
Four big brown bats, Eptesicus fuscus Beauvois 1796, served as subjects in these experiments, two males and two females. The animals were collected from private homes in Maryland (Department of Natural Resources scientific collecting permit 41213) and housed in the University of Maryland bat vivarium. Bats were exposed to a reversed 12 h dark:12 h light cycle and given free access to water. Bats were maintained at 80% of their ad lib feeding weight and normally fed mealworms only during experiments. Animal care and experimental procedures were approved by the University of Maryland Institutional Care and Use Committee.
We conducted studies of the flight path and sonar signals used by E. fuscus as it performed a task that required both obstacle avoidance and target localization. Experiments were carried out in a large flight room (Fig. 1), lined with acoustic foam (Sonex, Illbruck, Minneapolis, MN, USA). Low level long wavelength lighting excluded the big brown bat's use of vision (Hope and Bhatnagar, 1979), but still allowed for high-speed video recording and 3-D reconstruction of the animal's flight path. In this experiment, the bat had to dectect and localize a tethered insect behind one of two openings in a mist net that divided the flight room. The positioning of the food reward was randomized from trial to trial. The back end of the room was divided further by a partition net, requiring the bat to select the correct opening to obtain its food. The mist net was made of 0.1 mm threads, arranged in a grid and spaced 25 mm apart. The net was moved every day to prevent the subjects from memorizing the positions of the openings. The openings were circular, ca. 40 cm in diameter, requiring the bats to maneuver quite accurately to fly through. E. fuscus could detect the mist net and the two openings using echolocation, but would occasionally crash into it, presumably because the weak echo returns from this obstacle were difficult to detect and localize.
After preliminary training, the four bats performed a total of 141 trials with between 16 and 67 trials per animal (Table 1), depending on their health and motivation to perform the task. Food rewards, tethered mealworms, were suspended at a height of about 1.5 m above the floor, at different distances in front of and behind the net. The database only includes the trials in which the bats attempted to capture the prey. For analysis, we pooled the trials into four groups according to worm–net separations: far front (worm more than 10 cm in front of the net), close front (worm between 10 and 0 cm in front of the net), close behind (worm between 0 and 10 cm behind the net) and far behind (worm between 10 and 110 cm behind the net). The trials with the tethered mealworm far behind the net were sub-divided into `on-axis' and `off-axis', where the mealworm hung either directly behind the hole or at an angle of 45 deg. or more from behind the hole. We ran 37 on-axis and 14 off-axis trials in total.
Schematic 3-D (A) and top view (B) of the flight room (7 m × 8 m× 2 m) and experimental set-up for the dual task. A net is stretched across the flight room and one of two openings (hole a or b) allows the bat access to a food reward (tethered insect; red oval) on the other side of the net. The bat's task is to find the tethered insect behind one of these openings and fly through it to access the food. A partition net divides the back end of the room to allow the bat access to the food reward only if it flies through the correct opening. Two high-speed video cameras (Cam 1 and Cam 2) were used to reconstruct the 3-D flight path of the bat and positions of other objects in the room. Full bandwidth recordings of the bat's echolocation calls were taken with two microphones (1 and 2) positioned on the floor. A 16 microphone array (green circles in A, black circles along the inside perimeter of the inner box in B) positioned along three walls was used to reconstruct the beam pattern of each sonar emission.
To characterize the echo levels experienced by the big brown bat in this task, we measured echoes from the worm and the net. Using Tucker-Davis-Technologies System 2 (Alachua, FL, USA; hardware and software), amplified, filtered (Stanford Research Systems, Sunnyvale, CA, USA), frequency modulated (FM) sounds were generated and broadcast through a speaker [Tweeter LT800, frequency response flat (±3 dB) up to 100 kHz] powered with Krone-Hite DC amplifier (Brockton, MA, USA). Echoes were picked up with a GRAS 1/4 in microphone (40BF, GRAS, Holte, Denmark) amplified 40 dB by a Larsen-Davis amplifier/power supply (Provo, UT, USA), filtered by a WaveTech filter (Karachi, Pakistan; band-pass filtered 10 kHz–100 kHz) and digitized on-line with a Wavebook (IOtech, Cleveland, OH, USA), using a sampling rate of 500 kHz. The broadcast signal was 1 ms in duration and consisted of a downward linear FM sweep, from 90 kHz to 20 kHz, shaped by a Hanning window function. The source level from the speaker was 77 dB peSPL (peak equivalent sound pressure level) at 10 cm. The signal was repeated every 50 ms. The speaker and the microphone pointed towards the same position on the target, but the microphone was placed 10 cm closer to the target than the speaker to maximize the signal to noise ratio. The speaker was placed 50 cm from the target. With a signal duration of 1 ms, there was no overlap between the outgoing sound and returning echo. We measured the target strength of the net at two angles, 90 and 45 deg., between the net and the sound beam. Target strength of the mealworm was measured from the side. All target strength calculations are referenced to 10 cm such that the target strength was measured in dB as the echo level 10 cm from the target relative to the incoming sound level at the target. The target strength of the net measured at an angle of 90 deg. was –26 dB, whereas the target strength measured at an angle of 45 deg. was –22 dB. The target strength of the tethered worm was –16 dB. All sound levels are given in dB SPL re. 0.0002 Pa r.m.s. The microphones were calibrated using a Brüel and Kjær sound level calibrator (4231, Nærum, Denmark).
Two frame-synchronized, high-speed video cameras (Kodak MotionCorder, 240 Hz, San Diego, CA, USA) were positioned in the upper corners of the flight room. A calibration frame (Peak Performance, Boulder, CO, USA) was placed in the room and filmed by both cameras prior to each recording session. The video cameras were used to record the positions of the microphones, net and holes, and the target, bat flight path and capture behavior.
Full bandwidth echolocation signal recordings were taken by two ultrasonic transducers placed on the floor within the calibrated space, and recorded digitally on an IOtech Wavebook (sample rate 250 kHz per channel).
The echolocating bat controls not only the spectral–temporal features of its echolocation cries but also the aim and directional characteristics of its sonar beam. Eptesicus fuscus is an oral emitter, and the sonar beam is aligned with the head. A linear microphone array was used to record the big brown bat's sonar signals at 16 different locations in the flight room. For each video frame in which a vocalization was detected, the normalized beam intensity at each microphone was computed. E. fuscus emits a broad band FM call with a first harmonic sweeping down from ca. 60 to 25 kHz. The original signal was decomposed into three sub-bands (20–30 kHz, 30–40 kHz, 40–50 kHz) and the intensities computed in each sub-band for every vocalization. Using standard tables (ISO 9613-1) a scaling factor correcting for the sound absorption due to air was computed for each frequency band (see Lawrence and Simmons, 1982). Finally, the intensities in each band were corrected for spherical loss and summed to yield a normalized intensity for each vocalization in the direction of each microphone. Vectors were drawn from the bat to each microphone. The length of each vector was made proportional to the normalized intensity at the corresponding microphone. Based on these vectors we constructed a normalized shading pattern such that the peak intensity has a value of 1.0 and is colored black. Lighter colors denote progressively lower intensities. The resultant shading pattern displays an estimate of the big brown bat's 2-D beam pattern. The resultant vector provides an estimate of the bat's beam axis, and the angular separation between the beam axis and an object of interest (obstacle or prey) defines the tracking angle (for details, see Ghose and Moss, 2003). A third video camera was placed below the hole for close-up recordings in selected trials at the start of the experiment to verify that the beam axis accurately represented the aim of the bat's head.
The duration and pulse interval (time from start to start of pulses) defines the pulse–echo separation. These time measurements were recalculated to distance (m) using a velocity of sound of 340 m s–1 at room temperature and humidity, and depicted along the range axis (lower panel of Fig. 2). Plots of pulse duration, measured in meters, along with the distance from bat to net and bat to insect, respectively, revealed how the big brown bat, by decreasing the pulse duration, prevented overlap between its sonar vocalization and net or insect echoes.
(A) Schematic illustration of the method used to calculate the direction of the big brown bat's sonar beam axis and the tracking angle from microphone array recordings. (B) Temporal relationship of pulse and echo(es) from the bat's perspective. The pulse duration (Dur) defines the distance in front of the bat where the echo from an object will overlap with the outgoing pulse. Decreasing the pulse duration can prevent overlap between the bat's sonar vocalization and the echo. If there are several objects at different ranges, the bat may experience overlap with echoes from closer objects and avoid overlap with more distant objects.
The big brown bat, Eptesicus fuscus, actively controls the features and directional aim of its sonar calls to probe the environment. We studied each bat's vocal behavior, along with its performance. We reconstructed the 3-D flight path, and correlated to echolocation behavior, to quantify the vocal control and flight strategies it employed to negotiate a dual task, requiring both obstacle avoidance and prey capture. Fig. 3 shows two typical strategies, when the prey is far behind the hole. The bat may either fly directly towards the prey after passing the hole or it may first negotiate the hole and then make a U-turn to take the tethered insect, in particular when the prey is far off-axis with respect to the middle of the hole.
All bats achieved close to 100% success rates when capturing tethered mealworms in an open room, but introduction of the fine mist net in this experiment reduced the bats' overall success rates to between 50 and 82%, indicating how difficult the task was (Table 1). It has been shown that grouping of pulses or `strobing' occurs when bats are required to operate in acoustically complex environments (Moss et al., 2006). In all net trials, pulse interval (PI) plots showed that bats produced sonar sound groups for extended periods of time, indicating how challenging this task was for the big brown bat. The plots show that sonar strobing started well before (0.5–1 s) the bat crossed the net (Fig. 3). With the worm in front of the net, the task was comparable to prey capture in clutter and, accordingly, the bats' performance rates were comparable to those observed in an earlier experiment requiring the bats to take tethered insects between 40 and 10 cm from an artificial plant (Moss et al., 2006). As in clutter experiments, the success was lower the closer the prey was to the net.
All bats were reluctant to fly through the hole at first, in particular bats W24, HP2 and BL52, and therefore it was only possible to collect a limited data set from these animals in the two behind net conditions (Table 1). Trials where the bats did not attempt to capture the prey were not included. HP4, on the other hand, learned quickly, and flew through the net to take insects as far as 110 cm behind the net. For these reasons, different numbers of trials were run for the four bats under the different conditions.
The bats' success dropped drastically as the reward was moved from positions in front of the net to positions behind the net. With the worm behind the net the task became more difficult because the bats faced two challenges: negotiating the net and capturing the insect prey. This task required the bats to maneuver through the (correct) hole before seizing the prey. We did not include trials with the target far behind the net if the bats did not attempt to fly through, as the primary goal of this study was to quantify the bat's sonar behavior in solving the task, rather than its success rate. The bats typically started by flying two or three rounds on the starting side of the net, where they approached the holes while emitting a series of high repetition rate pulses, inspection trains, presumably to decide which hole to fly through for capture.
The two panels show 3-D plots (axes, m) aligned with plots of pulse interval (PI) and pulse duration. Time=0 s is when the bat flies through the hole. In A the worm was 58 cm behind the hole, on-axis, and the bat flew straight from the hole to seize the prey. In B the worm was 56 cm behind the hole, off-axis, and the bat made a `U-turn' before capture. When the bat approached the net, the pulse interval and duration were reduced, as shown in the lower panels.
When the worm was close behind the net many failures were misses, where the bat neither captured nor touched the worm. When the worm was far behind the net, many failures were due to the bat choosing to fly through the wrong hole (Table 1). In all trials, the echo from the worm, regardless of its position behind the net, was well above the bat's detection threshold when it flew within 1 m of the net before crossing it.
When the reward was far behind the net, it could either be on-axis with the hole, i.e. on a straight line perpendicular to the net, starting approximately in the middle of the hole, or off-axis, i.e. at an angle of 45 deg. or more with respect to that line. The success in on-axis trials was not higher than in off-axis trials (on-axis, 57%; off-axis, 56%; P>90%, Chi-square). Thus, the results for on- and off-axis trials were pooled into one category: far behind.
Target strength measurements were used to estimate detection distances assuming sonar calls with a source level of 110 dB SPL and 30–35 kHz as the dominant frequency (Surlykke and Moss, 2000), and a detection threshold of 20 dB in the cluttered lab. These estimates indicate that the net echoes would be detectable by the bat at a maximum distance of 3.1 m when ensonified at 90 deg. and at 3.8 m when ensonified at 45 deg. The target strength of the mealworm was stronger, indicating that it would be detected by the bat at distances up to 4.8 m, greater than those encountered by the bat in this study.
The acoustic behavior of all big brown bats revealed distinctly sequential sampling of echo information from the net and the worm. The changes in beam angle clearly illustrate the sequential processing. The bat directed its beam back and forth between the left and right edges of the net hole until around 100–300 ms before flying through the net opening, when the beam axis was shifted from the edges and directed through the hole towards the worm (Fig. 4). The scanning between the left and right edge shows that the bat did not sample all elements of the auditory scene simultaneously, but shifted its focus from object to object sequentially. Animations of the bat's dynamic adjustments of the beam pattern as it performed in this task can be found at http://www.bsos.umd.edu/psyc/batlab/nethole/beamaim/.
We measured the angular difference between the beam axis and the edges of the net hole and the insect prey to quantify its directional `gaze' at the time of each vocalization across trials.
The precision with which the big brown bat aligned its head with a target is far greater than needed to maintain a strong, audible echo. Indeed, this bat species' sonar beam is sufficiently broad to yield detectable echoes 30–60 deg. off-axis (Ghose and Moss, 2003). The big brown bat's accurate directional aim of the sonar beam axis at obstacles and prey may be driven by requirements for higher spatial resolution along the auditory midline. This observation leads us to infer that the directional aim of the sonar beam axis is related to target localization and selection.
Data from two selected trials, when the big brown bat flew towards and through the net hole and captured the insect on the other side. The four panels (A–D) for the two trials show beam directing data up to selected video frames (number displayed in each panel). The dashed red line extends the beam axis of the last call displayed in each panel, illustrating how the beam was directed at either the right edge (RE) or the left edge (LE) of the hole, until the bat shifted its beam axis to the more distant worm (W). The plots on the right summarize schematically the bat's beam-directing behavior in the two selected trials. The edges of the holes are shown as horizontal lines, with LE as the upper line and RE as the lower line. Each call is represented by a filled black circle on either of these lines, according to beam axis. The red letters (A–D) refer to the corresponding panels. The plots show how the bat scanned sequentially back and forth between the left and right edges of the hole until 200–300 ms before crossing the net, when it shifted its beam direction towards the worm on the other side of the net. In trial 7.17.1.14 the bat took a `quick look' at the left edge with one call (in frame 157 of C).
The directional aim data in Fig. 4 show sequential scanning of obstacles (right and left edges of the net hole) and prey in all trials. When the bats were far from the hole, the angles to the edges and the prey were so close it was difficult to determine precisely where they were directing the sonar beam axis, but when they came closer to the net, the data revealed that they directed the sonar beam axis to the left or to the right edge of the hole, or to the prey, but not to all of these objects simultaneously. They scanned back and forth between these objects, a behavior that shows parallels with saccadic eye movements. The tracking angle revealed that well before crossing the net, the beam axis shifted from the edges of the hole to the worm on the other side of the net.
Summary of the beam aim of the calls produced by the big brown bat, subject HP4, as it approached the net and flew through the hole to get the insect in 18 successful trials with the insect far behind the net. Beam aim for each sonar call is displayed as a function of time, with all trials aligned with respect to the time when the bat flew through the net hole (zero on the abscissa). Blue line segments above the time axis for each trial show vocalizations directed at the left edge of the net hole, and black line segments below the time axis show vocalizations directed at the right edge of the net hole. Vocalizations directed at the mealworm are shown with red triangles pointing to the right. Beam-directing behavior was taken from the beam axis measurement, ±5 deg. The plots illustrate how the bat scanned back and forth between the edges of the hole. Well before crossing the net hole (time zero) the bat shifted its gaze to the more distant prey (red triangles).
The bat's sequential acoustic scanning between the left/right edge of the hole and the tethered worm was prominent over the entire sequence of trials in this experiment, as illustrated in Fig. 5, which summarizes 18 successful trials with bat HP4. Vocal data for each trial are displayed as a function of time, and they are aligned with respect to the time when the bat flew through the net hole (zero on the abscissa). Blue line segments above the time axis for each trial show vocalizations directed at the left edge of the net hole, and black line segments below the time axis show vocalizations directed at the right edge of the net hole. Vocalizations directed at the mealworm are shown with red triangles pointing to the right. These plots display the sequential shifts in beam aim between closely spaced objects as the bat approached and crossed the net opening. Also shown for each trial is the shift in the bat's beam aim to the worm long before it crossed the net at time zero.
In some trials the subjects interspersed sonar beam fixations at the edges of the hole with fixations at the worm, but in most trials the bats did not direct any cries towards the insect until initiating their final approaches to the hole. Presumably, the bats did not need updated information on the insect's position, because during inspections earlier in the trial they had already found the worm, which guided the choice of which hole to fly through. The bats typically flew several rounds on the starting side of the room before flying through the net hole to retrieve a food reward. Our data collection was end triggered after capture of the insect, and the buffer size (video and sound recording) was limited to 8 s, which is much shorter than the total duration of most trials.
While scanning the edges of the net hole, the bat directed the beam axis to one edge of the net opening over a number of successive sonar calls. Earlier experiments (Ghose and Moss, 2003) in an open room showed that the big brown bat fixated the beam axis on the worm ca. 300 ms before capture with an angular offset close to zero (±3 deg.). In the experiments reported here, locking the beam axis at an object with high accuracy started much earlier with respect to the time of capture. In trials with the tethered worm ≥50 cm behind the net, the bat started directing the beam at the edges of the hole around 500–800 ms before crossing the net, and the worm was captured between 100 and 600 ms after passing through the hole (Fig. 5). Directing the beam axis on the net edges was at least as accurate (±5 deg.) as directing it on the worm, even though the flying bat changed its position from call to call. The directional aim of calls to objects in the environment was assigned by two independent observers who used beam axis measurements and beam aim animations to score data for each trial. Inter-observer reliability was greater than 0.9, and any trial segments in question were scored by a third observer. The directional aim data reported here are based on the agreement of at least two observers. Tracking angle distributions for the left and right edges of the net hole, as well as the worm, are presented for bat HP4 in Fig. 6. The criterion for assigning where the bat directed its sonar beam before it crossed the net was a tracking angle of ≤15 deg. relative to the net hole edges or the worm. The few vocalizations that did not fall within this range were not assigned to any object.
The sequential fixation on either the left or right edges of the net hole indicated that the big brown bat did not sample sonar information about the two sides of the net hole (auditory objects) simultaneously. Another indication that the bat sequentially sampled closely spaced objects comes from the beam aim behavior in certain trials (see Fig. 4), which showed that the bat directed one call, a `quick look', to the opposite edge of the hole it was inspecting with several successive sonar calls. The sonar pulse interval was short as the bat was close to crossing the net when these quick looks occurred. Analysis of two such examples, when the bat interspersed one call to one edge of the hole in between a series of calls directed at the opposite edge, revealed pulse intervals of 22 and 33 ms when directing the beam to one edge of the net opening and only 18 ms when directing the beam axis back, yielding a total duration of these quick looks of around 50 ms (see Fig. 4). Such fast motor control likely did not result from immediate feedback from each sonar call, but probably required planning over several calls. The bat's sonar pulse interval when it was changing beam aim from the left to right edge of the net opening had a similar duration, and it was seldom that bats emitted any calls `in transition', i.e. producing calls in between shifts of the beam direction from one edge of the net hole to the other or at the prey. In 18 successful trials where bat HP4 captured the prey far behind the net, it directed its beam to either the left or the right edge in 325 calls, at the worm in 332 calls, and only in between these objects in 4 calls. This summary includes only sonar calls before the final insect capture buzz in the 18 trials. Thus, the data demonstrate that bats were able to shift the directional aim of the sonar beam in a very short time interval.
The plots show tracking angle distributions for sonar calls directed at the left and right edges of the net, as well as the worm before and after passing the net. Sonar beam tracking angles ≤15 deg. were assigned to the left or right edges of the net hole or the worm. The few vocalizations that did not fall within this range were not assigned to any object. Data in this figure include vocalizations that were produced by the bat in both successful and unsuccessful trials.
The results from measurements of temporal features of the sonar calls confirmed the results of the beam aim data because pulse duration and repetition rate also showed that the bats sampled the acoustic objects sequentially. When echolocating bats home in on a prey item, they adjust the duration and timing of their sonar signals to temporally isolate the prey echoes in a pulse–echo overlap-free window. In these experiments bats adapted their acoustic behavior in a similar manner. Pulse duration and PI decreased when the bat approached the net opening, although not by as much as in a typical terminal buzz before prey capture. Pulse duration decreased monotonically such that there was no overlap between the outgoing sonar signal and the echo return from the net, until around 100–300 ms before the bat flew through the net opening, when pulse duration increased (Fig. 7). As the bat approached the net, the decrease in pulse duration served to prevent overlap between its vocalizations and net echoes. When the call duration was increased before the bat crossed the net, the beam extended well beyond the net towards the worm on the other side. The results suggest that the increase in pulse duration, allowing for overlap between sonar vocalizations and net echoes, marks the point in time when the bat shifted its gaze along the range axis from the net to the more distant worm.
Concurrent with the increase in duration observed before crossing the net, PI often increased, although not all trials revealed this pattern distinctly. Subsequently, pulse duration and PI decreased again until capture of the insect. In the final attack of the insect, the PI and duration values were characteristic of a typical terminal buzz for E. fuscus (Surlykke and Moss, 2000).
Comparison of pulse duration with beam aim (dashed red line in Fig. 7A) further illustrates that the time when the bat shifted its gaze from the edges of the net opening to the worm (taken from tracking angle data) corresponds well with the time when the bat increased pulse duration, allowing overlap between net echo and pulse. The bottom panel of Fig. 7A shows how the pulse duration (measured as distance; blue curve) changed in relation to the distances between the bat and worm (black) and between the bat and net (magenta). Hence, both independent measurements, beam angle and pulse duration, showed that the bat shifted its sonar gaze from net hole to prey well before it flew through the hole. Furthermore, these shifts in beam direction and call duration co-occurred. On average, the shift in sonar beam axis to the prey occurred 220±140 ms before crossing the net, and the increase in pulse duration resulting in overlap with the net echo occurred 219±79 ms before crossing the net. The correlation between the time of the shift of beam axis and the time of increase in pulse duration (Fig. 7B) was statistically significant, R2=0.59 (P<0.01). The shift in gaze from net hole to worm may indicate the time when the bat had localized the hole with enough accuracy to fly through, and started planning its attack of the insect.
(A) Top, schematic illustration of the beam-directing behavior in a selected trial (see also Fig. 4). The big brown bat scanned back and forth between the left and right edges of the hole until ca. 250 ms before flying through the hole, when the beam axis shifted to the worm. Bottom, duration of sonar calls from the same trial, converted to distance (blue curve), plotted as a function of time relative to net crossing (time zero). The magenta curve shows the distance between the bat and net, with a minimum at time zero, when the bat flew through the hole. The black curve shows the distance between the bat and worm. Sonar signal duration (blue) decreased as the bat approached the net, but started increasing approximately 300 ms before it crossed the net, creating overlap between call and net echoes around –250 ms, corresponding with the shift of beam aim to the worm (red dashed double-headed arrow). (B) Time of worm fixation (Y-axis) plotted against time of pulse–echo overlap (X-axis) over 16 trials.
How do animals process, organize and utilize information from a rich and complex environment? Furthermore, how is this information integrated with motor programs to support perceptually guided behavior? To pursue these questions we analyzed in detail the big brown bat's active control over its sonar signals as it performed a spatial task that required both obstacle avoidance and target interception.
Echolocation, like other active sensing systems, involves feedback between action and perception: the bat produces ultrasonic vocalizations and processes echo information to guide vocal-motor adjustments to further probe the environment. Similar to active visual scanning of the environment by eye movement, fixation and accommodation, the big brown bat scans the environment acoustically by directional control of the sonar beam (through movement and fixation of the head aim), coupled with range-dependent adaptive changes in sonar call duration and pulse interval. Measurement of the directional aim and features of the big brown bat's sonar cries allows us direct access to the signals that drive its behavior.
The results of our study demonstrate that the big brown bat sequentially samples the environment with its sonar vocalizations, adjusting the direction and distance of its acoustic gaze, in a manner analogous to sequential visual fixation of objects within a complex visual scene. Due to the broad directionality of the emitted beam (Ghose and Moss, 2003), almost equal sound energy impinges on objects within a wide angle ahead of the bat. The sonar beam of the big brown bat is sufficiently broad (>120 deg. at 6 dB down from the peak) (Hartley and Suthers, 1989) to return concurrent audible echoes from the closely spaced opening in the net and the tethered worm. If the big brown bat was to simultaneously sample echo information from the obstacle and prey in this task, we would expect the animal to maintain its beam axis in the general direction of all these objects. However, we found that the big brown bat points its sonar beam axis sequentially at the edges of the net opening and prey, often scanning back and forth between these objects. This behavior pattern resembles visual scanning of objects in a natural scene by humans (Land and Hayhoe, 2001).
The big brown bat's sequential acoustic scanning of the obstacle and prey is consistent with findings reported by Barber and colleagues, who showed that the gleaning pallid bat, Antrozous pallidus, cannot process two streams of auditory information simultaneously (Barber et al., 2003). However, in Barber and colleagues' experiments, the two streams of information were obtained through echolocation and passive listening. The central auditory system of the pallid bat appears to have evolved to segregate the processing of echolocation and prey-generated sounds into two separate populations of neurons in the inferior colliculus (Fuzessery, 1994). Here, all streams of acoustic information, from both prey and obstacles, were obtained through echolocation. As the bat sequentially adjusted the direction and duration of the sonar beam to inspect the obstacle and prey, we infer that directional and temporal cues are the most important acoustic parameters to this animal for the segregation of auditory objects in the scene. This indicates that the big brown bat's adaptive control of the beam aim and pulse duration is key to its success in complex, cluttered environments. Insectivorous bats of different species exploit a wide variety of habitats ranging from very cluttered space to completely open air. It is hard to imagine that it will be possible in the future to measure and track the beam aim of a bat hunting in the wild. However, the fine correlation between beam aim and temporal call features demonstrated by this study indicates that changes in temporal parameters correlated to a bat's position with respect to background may allow one to infer which objects in the natural environment the bat was sampling along the range axis. Thus, future field studies may reveal whether other bat species with different habitat preferences also sample auditory objects sequentially to segregate streams in a complex natural habitat.
In visual animals, eye movements during scanning of a scene consist of a series of fixations interspersed by saccades to move the eye from one point to the next. Birds move the whole head to fixate the eyes (Eckmeier et al., 2008). In primate vision, behavioral (Rizzolatti et al., 1987) and neurophysiological studies (Kustov and Robinson, 1996) suggest a tight coupling between eye movement and attention systems. In the echolocating bat, we suggest that beam axis direction may correspond to its attention to different objects in the scene. Any listening animal will turn its head toward a sound of interest, exploiting the maximum directional acuity of hearing along the midline, which, for example, has been demonstrated elegantly in a thorough series of experiments with barn owls (Konishi, 1993). Echolocating bats can take advantage of the added directionality of the outgoing sound to reduce echo intensity from an off-axis object by controlling the aim of the sonar beam.
In vision, fixation points are related to the behavioral task (e.g. Yarbus, 1961). Pertinent to our study are look-ahead fixations. Numerous studies of humans engaged in natural tasks that require multiple, visually guided sequential behaviors have shown that reaching for an object is preceded by fixations at the object up to a few seconds in advance (e.g. Hayhoe et al., 2003). These look-ahead fixations are thought to contribute to task planning (Hodgson et al., 2000). A study of humans stepping over an obstacle (Patla and Vickers, 1997) showed that subjects fixated on the obstacle before, but not during, the period in which they navigated the obstacle. In our study we observed sonar beam fixations by the big brown bat on the edges of the net hole before but not when getting close to the time of net crossing, suggesting a link between perception and action planning also in the echolocation system.
Sonar fixations serve to lock the beam axis onto an object over successive sounds, just as visual fixations lock the fovea accurately onto a target until the next saccade. We measured the accuracy with which the big brown bat directed its sonar beam aim at obstacles, and compared these measurements with the accuracy of its beam aim at prey (Ghose and Moss, 2003). In the present study, the big brown bat directed its sonar beam at the obstacle with high accuracy, locking the beam axis onto the edges of the net opening over successive vocalizations with deviations of less than 5 deg., even though the angle of the object with respect to the bat continuously changed as it flew. Ghose and Moss (Ghose and Moss, 2006) proposed that this accurate locking of the sonar beam during prey interception serves to simplify steering towards and, finally, interception of the prey. As the results here show that the big brown bat's accuracy of directing the sonar beam axis to the obstacles it must avoid is as high as that to the prey, we infer that centering the beam axis also serves perceptual functions related to scene analysis. This implies that receiver width may be much narrower than the transmitted beam pattern.
The big brown bat's beam-directing behavior is much more precise than required for target echo detection. In a variety of species, localization accuracy is highest along the midline, falling off in the periphery [humans (Mills, 1958); monkey (Brown et al., 1982); cat (Heffner and Heffner, 1988)]. For example, the minimum audible angle in humans is about 1 deg. along the midline, increasing to 7.5 deg. at a test azimuth of 70 deg. As the echolocating bat's auditory system follows a general mammalian plan (Covey and Casseday, 1995), we hypothesize that its localization accuracy is also highest along the midline and falls off with azimuth, which is corroborated by the accurate directional control of the sonar beam in flight. When sitting on a platform, the big brown bat can track a target even more accurately, i.e. approximately 1 deg. (Masters et al., 1985). Enhanced processing of echoes along the midline shares some of the functional advantages of a fovea or visual streak in the retina, but without morphological specializations at the receptor level.
The sequential scanning of the echolocating bat resembles results from vision studies showing that humans and other primates sample information from a complex display by a series of fixations, interrupted by saccadic eye movements. The latency to make a visual saccade is typically longer than 200 ms (Liversedge and Findlay, 2000). When planning ahead, saccade latencies may be substantially shorter (Fischer and Weber, 1993), but still far greater than the big brown bat's latency of 20–50 ms to re-direct its sonar beam between the net opening and prey in this dual task.
Suppression of visual sensitivity during saccades gives rise to the perception of a continuous and stable retinal image, in spite of the retinal smear created by high velocity eye movements (Dodge, 1905; Volkmann et al., 1978). The echolocating bat rarely produced sonar calls during the transition from beam directing at one object to another. Instead of actively suppressing sensory input during high velocity head movements, the big brown bat appears to minimize auditory smear by reducing echo input when its head is turning. Thus, this bat species reduces information processing demands on the receiving auditory system through its vocal-motor control of the signal output.
When the echolocating bat shifts the direction of its sonar beam from obstacle to obstacle it also makes range-dependent adjustments in the duration of sonar calls to avoid pulse–echo overlap, suggesting accommodation to objects at different distances. If the big brown bat encounters objects at different distances, it typically shortens its calls to avoid pulse–echo overlap with the closest object. Therefore, the duration of this bat species' vocalizations provides an index of its acoustic gaze along the range axis. When a bat tolerates overlap between its pulse and the echo from a closer object, we infer that it has shifted its acoustic gaze to a more distant object. This shift in acoustic gaze occurred regularly in this dual task: after the bat found the net opening, it shifted its acoustic gaze to the worm behind the obstacle, tolerating overlap between its sonar calls and net echoes, sometimes for as long as 350 ms. In vision, shifts in fixation between targets that lie in different directions and at varying depths also require a combination of saccadic and vergence movements (Kumar et al., 2005).
Our results show that the big brown bat sequentially samples spatial information from closely spaced objects in a complex acoustic scene, even though shifts up to 30 deg. in the directional aim of its sonar beam axis should yield echoes of similar strength, due to the broad width of the beam (Ghose and Moss, 2003; Hartley and Suthers, 1989). Ghose and Moss (Ghose and Moss, 2006) demonstrated a correlation between the big brown bat's head direction and its flight control and suggested that this bat species uses its head orientation to set up a common reference frame for sensorimotor integration, as it converts its sonar information into flight motor commands. The results of the present study extend this interpretation to suggest that the big brown bat's accurate beam-directing behavior also plays a role in spatial localization and attention. In particular, the big brown bat's active control of sequential beam fixations to obstacles and prey may reflect its higher spatial resolution and allocation of perceptual resources along the auditory midline.
We wish to thank Amaya Perez and Wei Xian for technical support. Marianne E. Jensen assisted with data collection and analysis. This work was funded by NSF grant IBN0111973 and NIH grant R01-MH056366 to C.F.M., and grants from the Danish Natural Science Research Council and the Danish National Research Foundation to A.S. We also thank the Wissenschaftkolleg zu Berlin for fellowship support of C.F.M. and A.S. Deposited in PMC for release after 12 months.
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Pingalwara dispensary has an annual budget of Rs.60/- lacs. Apart from providing medicine to patients, this dispensary also provides medicine to the families of all the workers and also gives free medicine to over 200 mental and needy patients every month. Dental clinic attends to the need of new 250 patients every month. Regular Eye Check up is carried out in our clinic of all the patients. Pingalwara has its own Ultra Sound Centre where over 40 tests of patients, workers and their families are done each month. ENT cases of the Pingalwara are attended once a week by Dr. Jagdeepak Singh Prof. ENT Govt. Medial College, Amritsar and member Pingalwara Society. In addition, specialists in the field of Medicine, Ortho and Eye visit the patients regularly. All mental patients are sent to Mental Hospital regularly for follow/check up.
On 18th and 19th April 2015 at Manawala Complex of Pingalwara, live cochlear implant surgery was performed on a 6 year old deaf boy, Dharmvir Singh and 5 year old girl Mehak belonging to very poor families. …..
Blood Donation Camp for the residents of Pingalwara. There was enthusiastic response to this camp. A number of Blood Donation societies, students and youth came forward to donate blood . …..
Free Cancer and Medical checkup Camp at Manawala Branch of Pingalwara. During the Camp Mammography & Pep Test were conducted for the patients. In addition free ECG and Blood Sugar Tests …..
Pingalwara dispensary has an annual budget of Rs.60/- lacs. Apart from providing medicine to patients, this dispensary also provides medicine to the families of all the workers and also gives free medicine to over 200 mental and needy patients every month.
Dental clinic attends to the need of new 250 patients every month.
Regular Eye Check up is carried out in our clinic of all the patients.


Amy Korin joined Mirum as Director of Social in March of 2018. She has an MBA in Marketing and over 18 years of industry experience, including roles in Program & Community Management for Google and leading Social Media Marketing for Sears Home Services. Currently, she oversees 200+ influencer activations per year for clients such as Unilever, Purina, Colgate Palmolive and more at Mirum.
In her first year with Mirum, Amy worked on an award-winning campaign for AXE at Walmart with Scary Mommy, which is currently a finalist in two Effie Award categories.


Spend time by the sea, as well as checking out the local cuisine in Santa Ursula. Santa Ursula might not have well-known attractions within the city, but you won't need to venture far to find top places to visit like Loro Park and Lago Martianez Swimming Pools. Popular sights in the surrounding area include Garden Beach.
Where are the best places to stay in Santa Ursula?
When is the best time to visit Santa Ursula?


In this short course, you'll learn how consistent prioritization of test ideas ensures that you're only investing time in the ideas that are most likely to work.
In 4 short videos, you'll watch me capture and sort ideas using multiple sources of data: subjective predictions, Datastories patterns based on past data, and customer insights. You'll have a chance to try it all yourself in exercises, and what's more - you can ask questions.
Expect to spend about 40 minutes watching videos and another 60 minutes on exercises. Let's get started.
I've focused on A/B testing and optimization for over 4 years. Look me up on LinkedIn for my prior experience. Reach out on Twitter any time. I always reply.
You'll learn a prioritization framework that helps you see winning tests more often and spend less time building and running tests that are less likely to work. You'll also have an opportunity to have your questions answered.
It's 40 min of videos and we recommend 60 min for the included exercises. Every video and exercise is also open for discussion with the instructor.


The collection contains administrative records, legal research, alumni materials, publications issued by the school and records of professional organizations active at the school.
The University of Denver College of Law opened its doors in 1892, pioneering legal education on America's frontier. The law school initially adopted an apprenticeship model of legal education, recruiting attorneys in Denver to teach students the nuts and bolts of the practice of law. Students gained insight from their practitioner professors; aside from the rigors of classroom study, students also observed courtroom proceedings. This approach to teaching students by employing in-the-field methods remains at the heart of DU Law. The College was renamed Sturm College of Law in September 2004.
A pioneer amidst pioneers, the College of Law opened the doors to its Legal Aid Dispensary in 1904, thus creating the first clinical program in the nation and the precursor to DU Law's Student Law Office (SLO). A frontrunner in serving Denver's indigent populations, the Dispensary saw several incarnations before it evolved into the law school's present day clinical programs. The Westminster College of Law (founded in 1912) merged with the University of Denver College of Law in 1957. Westminster provided the only evening program of law study from Kansas City to the Pacific Coast. Evolving accreditation standards eventually required too large a budget for the strictly part-time institution, and the school merged with the University of Denver. Terms of the merger included naming the law library the Westminster Law Library, and the development of an evening program at the College of Law.
The collection is organized in 9 series: History, Alumni Records, Programs, Publications, Professional Organizations, Administrative Records, Memorabilia, Photographs, Career Services. Series are largely unarranged.
University of Denver Sturm College of Law Records. Special Collections and Archives. https://duarchives.coalliance.org/repositories/2/resources/777 Accessed April 20, 2019.


ZnO, NiFe2O4, NiFe2O4/TA and NiFe2O4/TA/ZnO photocatalyts were successfully synthesized and characterized, and they demonstrated significant photocatalytic efficiency under visible-light. The photodegradation rates of congo red (CR) are 35.7%, 19.4%, 25.5% and 91.1% over the ZnO, NiFe2O4, NiFe2O4/TA and NiFe2O4/TA/ZnO for 180 min, respectively. The results display that the NiFe2O4/TA/ZnO has the most excellent photocatalytic efficiency for CR among to the other photocatalysts. Furthermore, NiFe2O4/TA/ZnO may be separated easily from solution by magnet because of the magnetic property of NiFe2O4. The considerable increment in efficiency of NiFe2O4/TA/ZnO can be attributed to synergistic effects between NiFe2O4, the tannic acid (TA) and ZnO, which extend lifetime and hinder the recombination of photogenerated charge carriers. This work presents new perspectives on the use of tannic acid based magnetic photocatalysts in wastewater treatment.
1.	Alam, U, Khan, A, Raza, W, Khan, A, Bahnemann, D, Muneer, M, Highly efficient Y and V co-doped ZnO photocatalyst with enhanced dye sensitized visible light photocatalytic activity, Catalysis Today, 2017, 284, 169–178.
2.	Lin, X, Chen, H, Hu, Z, Hou, Y, Dai, W, Enhanced visible light photocatalysis of TiO2 by Co-modification with Eu and Au nanoparticles, Solid State Science, 2018, 83, 181–187. 3.	Adeleke, J.T, Theivasanthi, T, Thiruppathi, M, Swaminathan, M, Akomolafe, T, Alabi, A.B, Photocatalytic degradation of methylene blue by ZnO/NiFe2O4 nanoparticles, Appied Surface Science, 2018, 455, 195–200.
4.	Ren, A, Liu, C, Hong, Y, Shi, W, Lin, S, Li, P, Enhanced visible-light-driven photocatalytic activity for antibiotic degradation using magnetic NiFe2O4/Bi2O3 heterostructures, Chemical Engineering Journal, 2014, 258, 301–308. 5.	Pant, B, Park, M, Kim, H.Y, Park, S.J, Ag-ZnO photocatalyst anchored on carbon nanofibers: Synthesis, characterization, and photocatalytic activities, Synthetic Metals, 2016, 220, 533–537.
6.	Delsouz, Khak, M.R, Shafeeyan, M.S, Raman, A.A.A, Daud W.M.A.W, Evaluating the efficiency of nano-sized Cu doped TiO2/ZnO photocatalyst under visible light irradiation, Journal of Molecular Liquids, 2018, 258, 354–365.
7.	Davar, N, Farhadian, M, Nazar, A.R.S, Homayoonfal M., Degradation of diphenhydramine by the photocatalysts of ZnO/Fe2O3 and TiO2/Fe2O3 based on clinoptilolite: Structural and operational comparison, Journal of Environmental Chemical Engineering, 2017, 5, 5707–5720. 8.	Zeng, J, Song, T, Lv, M, Wang, T, Qin, J, H, Zeng, Plasmonic photocatalyst Au/g-C3N4/NiFe2O4 nanocomposites for enhanced visible-light-driven photocatalytic hydrogen evolution, RSC Advances, 2016, 6, 54964–54975.
9.	Sun, J, Fu, Y, Xiong, P, Sun, X, Xu, B, Wang, X, A magnetically separable P25/CoFe2O4/graphene catalyst with enhanced adsorption capacity and visible-light-driven photocatalytic activity, RSC Advances, 2013, 3, 22490.
10.	Xia,Y, He, Z, Su, J, Tang, B, Hu, K, Lu, Y, Sun, S, Li, X, Fabrication of magnetically separable NiFe2O4/BiOI nanocomposites with enhanced photocatalytic performance under visible-light irradiation, RSC Advances, 2018, 8, 4284–4294.
11.	Patil, S.S, Tamboli, M,S, Deonikar, V.G, Umarji, G.G, Ambekar, J.D., Kulkarni, M.V., Kolekar S.S., Kale, B.B., Patil, D.R., Magnetically separable Ag3PO4/NiFe2O4 composites with enhanced photocatalytic activity, Dalton Transactions, 2015, 44, 20426–20434.
12.	Çakar, S, Özacar, M, Fe–tannic acid complex dye as photo sensitizer for different morphological ZnO based DSSCs, Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy, 2016, 163, 79–88.
13.	Güy, N, Özacar, M, Visible light-induced degradation of indigo carmine over ZnFe2O4/Tannin/ZnO: Role of tannin as a modifier and its degradation mechanism, International Journal of Hydrogen Energy, 2018, 43, 8779–8793.
14.	Güy, N, Çakar, S, Özacar, M, Comparison of palladium/zinc oxide photocatalysts prepared by different palladium doping methods for congo red degradation, Journal of Colloid and Interface Science, 2016, 466, 128–137.
15.	Güy, N, Atacan, K, Karaca, E., Özacar, M, Role of Ag3PO4 and Fe3O4 on the photocatalytic performance of magnetic Ag3PO4/ZnO/Fe3O4 nanocomposite under visible light irradiation, Solar Energy, 2018, 166, 308–316.
16.	Atacan, K, Özacar, M, Özacar, M, Investigation of antibacterial properties of novel papain immobilized on tannic acid modified Ag/CuFe2O4 magnetic nanoparticles, International Journal of Biolological Macromolecules, 2018, 109, 720–731.
17.	Şen, Türkyılmaz, Ş, Güy, N, Özacar, M, Photocatalytic efficiencies of Ni, Mn, Fe and Ag doped ZnO nanostructures synthesized by hydrothermal method: The synergistic/antagonistic effect between ZnO and metals, Journal of Photochemistry and Photobiology A: Chemistry, 2017, 341, 39–50.
18.	Güy, N, Özacar, M, The influence of noble metals on photocatalytic activity of ZnO for Congo red degradation, International Journal of Hydrogen Energy, 41 (2016) 20100–20112.
19.	Zhu, H,Y, Jiang, R, Fu Y.Q, Li, R.R, Yao, J, Jiang, S.T, Novel multifunctional NiFe2O4/ZnO hybrids for dye removal by adsorption, photocatalysis and magnetic separation, Applied Surace Science, 2016, 369, 1–10.
20.	Gautam, S, Shandilya, P, Singh, V.P, Raizada, P, Singh, P, Solar photocatalytic mineralization of antibiotics using magnetically separable NiFe2O4 supported onto graphene sand composite and bentonite, Journal of Water Process Engineering, 2016, 14, 86–100.


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