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# Flip-Flop in Digital Electronics

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A flip-flop is the basic memory element for storing a bit of information. It is an edge-triggered device. That is, it reacts to the edge of a pulse. A simple flip-flop has two stable states (remember, for instance, that a capacitor has two states: charged and discharged). States are represented by 1 and 0.

Stable state implies that the device remains in one state (e.g., 0) until an input changes its condition to the alternative state. Because a flip-flop has two states only, it is called a bi-stable device.

A basic flip-flop has two inputs and two outputs, as shown in Figure 1. The two inputs are used to set or reset the device and are denoted by R and S. The outputs are denoted by Q and $\overline{Q}$; they reflect the state of the flip-flop either 1 or 0. If Q = 1, then $\overline{Q}$ = 0, and if Q = 0, then and $\overline{Q}$ = 1. Figure 1 illustrates also the truth table for the states of a flip-flop.

Figure 1 Basic flip-flop.

A flip-flop acts like a single-pole double throw (SPDT) switch. When activated, it’s output toggles. This property can be used for many operations performed in digital electronics. The toggle action is performed through the inputs to a flip-flop.

There are a few types of flip-flops, as will be described shortly, in terms of their operational properties. The one shown in Figure 1 is the basic flip-flop or the simplest type.

Bi-stable: Having two stable (controllable) states.

Set: (for a flip-flop) Putting a device to the desired state. Some devices have only two states on and off, or high and low. Set implies putting the device in a desired (usually non-default) state.

Reset: Action of putting or setting a device to its default state.

Active level: The (high or low) level in which a logic device functions.

Active low: Implying that the active level for a device is low, as opposed to active high.

Active high: Two-state logic device (e.g., true and false, on and off, high and low) that acts (executes its function) when it is in a high state, as opposed to being active when in the low state.

Before continuing further we need to categorize flip-flops based on their structure, which defines the active level for a flip-flop. Active level is the logic level (high or low) that activates a device. For flip-flops, it implies if a flip-flop is set, or its state toggles, with a logical high or a logical low applied to its set input. In this sense, there are two categories of flip-flops, those whose active level is 1 and those whose active level is 0, i.e., those that are active high and those that are active low.

## Basic Flip-Flop

The basic flip-flop is set by applying an active level signal to its set input and the inverse signal to its reset input. When the unit is set, the Q output is high and the $\overline{Q}$ output is low. If, instead, the active level signal is applied to the reset terminal and its complement is applied to the set terminal, then the $\overline{Q}$ output is high and the Q output is low.

Also, as shown in Figure 1, one cannot apply a logical high to both set and reset of a basic flip-flop at the same time. It is like simultaneously pressing the start and stop button of an electric motor.

Structurally, a flip-flop can be made of two NOR gates or two NAND gates. This is shown in Figure 2. The gates are interconnected to each other or, in other words, they have feedback. The output of each gate is one of the two inputs to the other gate.

Figure 2 Internal structure of flip-flops.

Note the output of the gate designated as S. For the NOR-NOR flip-flop this is $\overline{Q}$; whereas for the NAND-NAND flip-flop, it is Q. Also, the active level for the former is 1, and for the latter is 0. In both types, a set input sets the content of output Q to high. To change the value of the output to low, the reset must be used. In other words, when the flip-flop is set, if the value of the input set changes to its complement it does not have any effect on the output.

In a NOR-NOR flip-flop the active level is high, but for a NAND- NAND flip-flop it is low.

A flip-flop is either set or it is reset. If it is set, it implies that the set button is activated. In this case, it is meaningless to set it again. Also, it is meaningless to make reset active, too. Thus, to reset a flip-flop, first, the set must be deactivated, and then the reset must be activated. Deactivation takes place by removing (turning off) the input signal.

Likewise, to set a flip-flop after it has been reset, first, the reset must be deactivated (this by itself has no effect and does not change in the status of the output), and then, if set is activated, it sets the flip-flop (it is meaningless to activate set if the reset is still active).

A flip-flop is set by the set input when the reset is not activated. It is reset by reset input when the set is not activated.

Note: In a pushbutton, the activation is performed by pushing, but immediately a spring brings the button to the deactivated position after being released. A flip-flop does not have the spring action; thus, the deactivation has to be separately performed.

What was said above can be observed in Figure 3 for both a NOR-NOR gate and for a NAND-NAND gate. Each gate has two inputs. One of the inputs, being either $\overline{Q}$ or $Q$, reinforces the stability of the output.

Figure 3 also shows that when a flip-flop is set, if S changes, nothing happens, and when it is reset, if R changes, nothing happens.

Figure 3 Stability reinforcement in (a) active high and (b) active low flip-flops.

## Clock-Controlled Flip-Flops

Clock-controlled flip-flops are more appropriate for synchronized operations, which is the case in microprocessor-controlled systems. The action of a flip-flop takes place with the clock pulse; therefore, it is in synchronism with all other operations (by other flip-flops).

Setting, resetting, or toggling are the three actions of a flip-flop; depending on the inputs one is carried out at either the rising edge of the clock pulse or the falling edge of the clock pulse. This depends on whether a flip-flop is a positive edge sensitive or negative edge sensitive. The symbols for the two are depicted in Figure 4.

Figure 4 Symbols for positive and negative edge triggering flip-flops.

For the desired action the data for the flip-flop inputs (0 and 1 values) are applied to them before the clock pulse enables the action. The clock input, shown as clk in Figure 4, is sometimes referred to as enable because it enables an action to take place. With the clock pulse, if the set input is activated, the flip-flop sets, and if the reset input is activated, it resets.

Figure 5a indicates how a clock or an enable signal is added to a flip-flop. This is shown only for a NOR-NOR flip-flop, but a NAND- NAND flip-flop has a similar structure. Figure 5 also illustrates how a basic flip-flop can be used with two AND gates in forming a J-K flip-flop.

Figure 5 (a) Adding a clock input to a flip-flop and (b) structure of a J-K flip-flop.

## J-K Flip-Flop

A J-K flip-flop is clock controlled and has the advantage that unlike the basic flip-flop it can accept both inputs (now called J and K inputs) to have an active level signal. This combination is prohibited for a basic flip-flop. The effect of having both inputs activated is a toggle of the output state.

In a J-K flip-flop, J input is used as set and K input as reset. When both J and K inputs are active, the flip-flop toggles its output (each output switched to its complementary value, no matter what its current value is). The symbol and the truth table of a J-K flip-flop are shown in Figure 6.

J-K flip-flop: Flip-flop with two data entries, one for set and one for reset the output. It is also possible to toggle the output by activating both inputs.

Figure 6 J-K flip-flop.

## D Flip-Flop

A data or D flip-flop is a clocked J-K flip-flop that has only one input. The arrangement is as shown in Figure 7a, which indicates how the one output relates to the J and K terminals.

The property of a D flip-flop is that the output follows the input. That is, with the clock pulse, the output will be whatever (0 or 1) has been placed on the input. Figure 7b shows this; even if the input (data) changes at points D1, D2, and so on, the output values update does not occur until the rising edge of the clock pulse, at C1, C2, and C4 (assuming the device is rising edge sensitive).

D flip-flop:  A flip-flop with only one input whose output follows the input after the enable or clock signal.

Figure 7 (a) Structure and symbol for D flip-flop. (b) Example of a D flip-flop timing diagram.

## T Flip-Flop

Another product based on a J-K flip-flop is a T flip-flop. Similar to D flip-flop it has a clock input and only one data input. If the input is logic 1, then at the active clock pulse edge the output is toggled.

Figure 8 depicts the structure for a T flip-flop and the truth table indicating what happens after the clock signal enable the flip-flop action based on the input and the output state. Note that a T flip-flop is based on a D flip-flop in which Q follows D.

Figure 8 Structure of a T flip-flop.

As we have observed, a J-K flip-flop toggles its output when both J and K inputs are set high. The toggle action takes place with the active edge of the clock pulse. Also, the T flip-flop toggles its output when the T input is high. Again, the action is carried out at the clock pulse edge.

There is another arrangement where a flip-flop toggles with the clock pulse. This is with a D flip-flop as shown in Figure 9, in which the complementary output is fed back to the data input. Because the output must follow the input, as the clock enables the action Q takes the value of $\overline{Q}$, thus toggling. Notice that when a flip-flop toggles, the frequency of its output pulse train is 1/2 of the clock frequency.

Figure 9 Toggle action with D flip-flop.

## Initialization

Normally, when a logic circuit becomes active, for example, at power up, the initial condition of a flip-flop is not defined or not known. We may need to make sure in what state it is before proceeding with operations. For this reason, two other inputs are added to flip-flops, a preset and a clear.

If the preset is activated it forces the output to go high (Q = 1), and if the clear is activated it forces the output to low (Q = 0). Clear and preset override the clock action. Figure 10 shows the symbol for a D flip-flop with these two entries and a sample timing diagram indicating their effect.

Figure 10 Flip-flop with preset and clear.

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# Principio de Huygens

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Series Geophysical References Series Digital Imaging and Deconvolution: The ABCs of Seismic Exploration and Processing Enders A. Robinson and Sven Treitel 1 http://dx.doi.org/10.1190/1.9781560801610 9781560801481 SEG Online Store

A wavefront is a surface over which a wave disturbance has a constant phase. As an illustration, consider a small portion of a spherical wavefront emanating from a monochromatic point source S in a homogeneous medium. Clearly, if the radius of the wavefront at a given time is r, then at some later time t, the radius will simply be ${\displaystyle r{\rm {+}}vt}$ where v is the phase velocity of the wave. But suppose instead that the wave passes through a nonuniform sheet of material so that the wavefront itself is distorted. How can we determine its new form? Or for that matter, what will the waveform look like at some later time if it is allowed thereafter to continue unobstructed? The major step toward the solution of this problem appeared in print in 1690 in Traité de la Lumière (Huygens, 1690[1]), which had been written 12 years earlier by the Dutch physicist, Christiaan Huygens (Figures 8 and 9). In that work, Huygens enunciated what has become known as Huygens’ principle (Robinson and Clark, 2006b[2]).

At about the same time that Newton was emphasizing the particle theory of light in England, Christiaan Huygens on the continent was greatly extending the wave theory. Unlike Descartes, Hooke, and Newton, Huygens correctly concluded that light effectively slows down on entering denser media. He derived the laws of reflection and refraction and even explained with his wave theory the double-refraction phenomenon observed in a specimen of the mineral calcite (Robinson and Clark, 1986[3]). While Huygens was working with calcite, he discovered the phenomenon called polarization. In his words, “as there are two different refractions, I conceived also that there are two different emanations of the waves of light” (Huygens, 1690[1], Chapter 5, Section 18).

Figure 8.  Christiaan Huygens, after a painting in the Haags Gemeentemuseum, the Hague.
Figure 9.  Pictures from Traité de la Lumière. From Huygens (1690[1]).

Huygens’ principle embodies a simple but powerful physical concept that serves to explain in a lucid manner how an arbitrary wavefront progresses from one point to another (Robinson and Clark, 2006b[2]). According to this hypothesis, each individual point on an advancing wavefront is disturbed. It therefore acts as a source of a distinct expanding disturbance of its own. Thus, each point of the wavefront at time t excites a secondary spherical wavelet that travels outward in all directions from this point. At a later instant ${\displaystyle t{\rm {+}}\Delta t}$, the new composite wavefront is the summation of the separate effects of all the wavelets originating in the earlier wavefront at the earlier time t. Graphically, the advanced wavefront is the envelope of all the individual wavelets. Figure 10 shows three examples of such summations.

The generality and flexibility of Huygens’ principle and the fact that it lends itself readily to a geometric construction are its chief merits. By its use, many problems that might otherwise be very difficult to understand can be visualized readily. When irregular discontinuities exist in a nonuniform medium, they give rise to complex reflection, refraction, and diffraction phenomena. Huygens’ principle is particularly useful for treating problems of this type. In the next section, we use it to derive the laws of reflection and refraction at an interface.

In summary, Huygens’ principle states that every point on a primary wavefront serves as the source of spherical secondary wavelets and that the primary wavefront at some later time is the envelope of these spherical wavelets. Moreover, the wavelets advance with a speed and frequency equal to that of the primary wavelet at each point in space. If the medium is homogeneous, the wavelets can be constructed with finite radii, whereas if the medium is inhomogeneous, the wavelets must have infinitesimal radii.

Thus far, we merely have stated Huygens’ principle without any justification or proof of its validity. Figure 11 shows a wavefront as well as several spherical secondary wavelets that after a time ${\displaystyle \Delta t}$ have propagated out to a radius of ${\displaystyle v\Delta t}$. The envelope of all of these wavelets then is claimed to be the advanced wavefront. This figure represents a graphic application of the essential ideas and as such is known as Huygens’ construction. However, as we see in the figure, there is also an envelope of the secondary wavelets to the rear of the wavefront.

The elementary statement of Huygens’ principle, as given above, is more intuitive than it is rigorous. Because we drew the wavelets as spheres, we might conclude that a backward-traveling waveform also exists, but that is not observed. It is not at all clear why the wavelets do not combine to produce a wavefront that proceeds backward as well as the wavefront that progresses forward. Nor is it obvious, without discussing phase relationships and concepts going beyond the geometric theory, just why the new wavefront coincides only with the geometric envelope of the wavelets. It is evident that we need a slight reformulation of the principle.

Figure 10.  (a) A plane wavefront at a certain instant in time. At a later instant, the advanced wavefront is the envelope of all the small wavelets excited by each point of disturbance on the original wavefront. (b) A similar construction for an advancing spherical wavferont. (c) It is evident that such a construction will be valid for a wavefront of any arbitrary shape, such as the one shown here.
Figure 11.  A wavefront, an advanced wavefront, and a nonexistent backward wavefront.

These difficulties were taken care of theoretically by Fresnel and Kirchhoff, who showed that only the forward-moving wave exists. Fresnel (1818)[4] further analyzed Huygens’ principle, and Kirchhoff (1883)[5] showed that Huygens’ principle results directly from the wave equation, thereby putting it on a firm mathematical basis. We are justified to use merely the forward wavefronts when we apply Huygens’ construction.

## Referencias

1. Huygens, C., 1690, Traité de la Lumière [Treatise on Light, in which are explained the causes of that which occurs in reflection and in refraction, and particularly in the strange refraction of Iceland Crystal]: The Hague. Republished by Macmillan and Company, London, 1912.
2. Robinson, E. A., and R. D. Clark, 2006b, Huygens’ principle: The Leading Edge, 25, no. 10, 1252–1255.
3. Robinson, E. A., and R. D. Clark, 1986, Sparring over light: The Leading Edge, 5, no. 4, 39–41.
4. Fresnel, A. J., 1818, Memoire Couronne sur la Diffraction. Reprinted in Fresnel, OEuvres complètes d’Augustin Fresnel, I: Paris 1865.
5. Kirchhoff, G. R., 1883, Vorlesungen über mathematischen Physik: Annalen der Physik, 18.

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# When are unions of isomorphic groups isomorphic?

I was thinking about how to prove $\operatorname{Br}(K)\cong H^2(\operatorname{Gal}(\bar{K}/K),\bar{K}^*)$ without having to introduce inductive limits and all the profinite stuff. So, I started wondering if the conditions of a direct system could be weakened for the cathegory of abelian groups in a way that isomorphisms would be still preserved. This brought me to the following general question:

Let $G$ and $H$ be two abelian groups, not necessarily finite, $I$ an index set and $(G_i) _{i\in I}$ and $(H_i)_{i\in I}$ families of subgroups respectevely of $G$ and $H$ such that

(1) $\forall i\in I: G_i \cong H_i$ and

(2) $\bigcup_{i\in I}G_i=G$ and $\bigcup_{i\in I}H_i=H$.

Question 1: Can we conclude that $G\cong H$?

Question 2: If yes, can we drop "abelian"?

EDIT: I forgot to mention that the $G_i$ (and $H_i$) are also assumed to be distinct subgroups.

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How about $G_i = G \cong \mathbb Z$ for all $i$, and $H = \mathbb Q$ and $H_i = \frac{1}{i!} \mathbb Z$? – j.p. Jan 26 '11 at 13:46
Consider $G_i=G=\mathbf{Z}/2\mathbf{Z}$ and $H=G \times G$ and $H_1=<(1,0)>, H_2=<(0,1)>$ and $H_3=<(1,1)>$, so you need some further assumptions. – Guntram Jan 26 '11 at 13:46
Even $I$ countable and $G_i$ finite abelian for all $i\in I$ doesn't help: take $G_0=H_0=0$, $G_{i+1} = G_i \times Z_{p^i}$ and $H_i$ to be the subgroup $p\cdot H_{i+1}$ ($H_{i+1} \cong G_{i+1}$). $G$ has then an element of order $p$ that is not a $p$-th power, whereas every element of $H$ has a $p$-th root. – Someone Jan 26 '11 at 14:20
Thank you for the insightful comments! – efq Jan 26 '11 at 14:30

For a counterexample, let $G_i=\mathbb{Z}$ be the integers and let $H_i=\frac1i\mathbb{Z}$, for positive natural numbers $i$. The union $\bigcup_i G_i=\mathbb{Z}$, but $\bigcup_i H_i=\mathbb{Q}$.
For the revised question, where you want $G_i$ and $H_i$ distinct, there are still counterexamples, such as $G_i=i\mathbb{Z}$ and $H_i=\frac1i\mathbb{Z}$.
On a positive note, if you have a bit more coherence in your isomorphisms, then you can make the affirmative conclusion. That is, if we can find particular isomorphisms $\pi_i:G_i\cong H_i$ which agree on their common domains, then they will build together into an isomorphism of $G$ and $H$. That is, what you want is not merely that $G_i\cong H_i$, but rather that the way that $G_i$ sits inside $G$ is the same as the way $H_i$ sits inside $H$. More generally, if $I$ is not just a naked index set, but is a directed set, such that when $i\lt j$ in this order then we have maps $G_i\to G_j$ and $H_i\to G_j$ and the isomorphisms $G_i\cong G_j$ make a commutative system, then the direct limit $G$ of the $G_i$'s will be isomorphic to the direct limit $H$ of the $H_i$'s by universal property arguments.
Just one question: In the less general case, where the isomorphisms $\pi_i$ agree on their common domains, how do they build into an isomorphism $G\cong H$ constructively? – efq Jan 26 '11 at 16:37
I meant that if we assume also that any two objects in the union appear together in some piece $G_i$, then the set-theoretic union of the piece-wise isomorphisms is literally an isomorphism of the unions. This is because being an isomorphism on the union sets is a local property, which will be preserved to unions, since $\pi(a+b)=\pi(a)+\pi(b)$ can be witnessed once you have $a$ and $b$ together, and similarly for injectivity and surjectivity. – Joel David Hamkins Jan 26 '11 at 17:05


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## C++ Programming

Application: Pendulum Clocks
Pendulums used in clocks, such as grandfather clocks, keep fairly accurate time for the following reason: When the length of a pendulum is large compared with the maximum arc of its swing, the time to complete one swing is independent of both the pendulumâ€™s weight and the maximum displacement of the swing. When this condition is satisfied, the relationship between the time to complete one swing and the length of the pendulum is given by this formula:
length = 12.0 * g * [time/(2.0 * ?)]2
In this formula, ? accurate to four decimal places is equal to 3.1416, and g is the gravitational constant equal to 32.2 ft/sec2. When the time of a complete swing is given in seconds, the length of the pendulum is in feet. Using this formula, youâ€™re to write a C++ program that calculates and displays the length of a pendulum needed to produce a swing thatâ€™s completed in 1 second. The length is to be displayed in inches.
Next, you apply the software development procedure to this problem.


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Polynomial version of the conjecture about Power free-values of polynomials - MathOverflow most recent 30 from http://mathoverflow.net 2013-05-20T05:21:46Z http://mathoverflow.net/feeds/question/116089 http://www.creativecommons.org/licenses/by-nc/2.5/rdf http://mathoverflow.net/questions/116089/polynomial-version-of-the-conjecture-about-power-free-values-of-polynomials Polynomial version of the conjecture about Power free-values of polynomials joro 2012-12-11T15:02:18Z 2012-12-12T08:28:48Z
The conjecture about Power free-values of polynomials is: Let $F(X)$ be a polynomial with integer coefficients and no repeated roots. For any $\epsilon > 0$, there exists a constant $C_{\epsilon,F}$ such that for any integer $n$ $$|n|^{\deg{(F)}-1-\epsilon} \le C_{\epsilon,F} \operatorname{rad}(F(n))$$

The conjecture implies this polynomial version. For $f(x) , g(x) \in \mathbb{Z}[x]$ and $f(x)$ squarefree,

$$\deg (\operatorname{rad}(f(g(x)))) > \deg(g(x)) (\deg(f(x))-1) \qquad (1)$$

The bound is tight because for Chebyshev polynomials $T_n,U_n$, $T_n(x)^2 - 1 = (x^2-1) U_{n-1}^2(x)$ with $f(x)=x^2-1$.

Is (1) proved for polynomials?

 http://mathoverflow.net/questions/116089/polynomial-version-of-the-conjecture-about-power-free-values-of-polynomials/116097#116097 Answer by Peter Mueller for Polynomial version of the conjecture about Power free-values of polynomials Peter Mueller 2012-12-11T15:34:44Z 2012-12-12T08:28:48Z
Haven't seen that anywhere, but it's easy to prove: Write $f(g(X))=\prod(X-\beta_i)^{e_i}$ for distinct complex $\beta_i$, and $e_i\ge1$. Taking the derivative gives $f'(g(X))g'(X)=h(X)\prod(X-\beta_i)^{e_i-1}$ for some polynomial $h(X)$. Now $f(X)$ and $f'(X)$ are relatively prime, hence so are $f(g(X))$ and $f'(g(X))$. Thus $\prod(X-\beta_i)^{e_i-1}$ divides $g'(X)$, implying $$\text{deg}(f(g(X))-\text{deg(rad}(f(g(X)))\le\text{deg}(g'(X))=\text{deg}(g(X))-1,$$ and the claim follows.


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# Robust fixed model

I have a question when I apply fixed and random model, then hausman test, the results show that the appropriate one is fixed model based on hausman test, then I want to check the heterocedasticity for the fixed model using xttest3 (modified wald test ) I found that there is an heteroscedasticity to correct it I have added option robust with fixed. Is it sufficient or then I have apply once again hausman, because I already try it I get this message hausman cannot be used with vce(robust) ... Also I have another question is it sufficient to decide between re and fixed model using hausman, can we use for example R2


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# diamond hierarchical lattice

Spectral properties of submatrices of the $\Gamma$ projection operator


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# Question 26 (2 points) What is the energy called that is stored as tissue by a parasitic plant that derives

###### Question:

Question 26 (2 points) What is the energy called that is stored as tissue by a parasitic plant that derives all of its energy from the roots of its host plant? Assimilation Energy Net Primary Production Ingested Energy Secondary Production None of the above;

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# Calculation of the $K_a$ for Nitrous Acid from $pH$ of Solution

CHEM-C7TNFB

When a solution of $1.50 \textrm{ M}$ nitrous acid reaches equilibrium, the $pH$ is $1.61$. What is the $K_a$ for nitrous acid?

A

$4.06 \times 10^{-4}$

B

$1.66 \times 10^{-2}$

C

$2.45 \times 10^{-2}$

D

$3.39$

E

$2.46 \times 10^3$


text:
maths > fractions

Proper, Improper, and Mixed fractions

what you'll learn...

overview

In this, the following are explained.

•  proper fraction: smaller than a whole and properly a fraction of a whole

•  improper fraction: larger than a whole in fraction form

•  mixed fraction: larger than a whole given as mix of a whole number and a fraction

mixing proper and improper

Consider the given figure. The colored part is the representation of a fraction and the gray part is shown only as a representation of the whole.

The fraction is $\frac{1}{4}$$\frac{1}{4}$.

The fraction represented by the colored part in the given figure is $\frac{2}{4}$$\frac{2}{4}$

The fraction represented by the colored part in the given figure is $\frac{6}{4}$$\frac{6}{4}$

The picture represents the fraction $\frac{6}{4}$$\frac{6}{4}$. Number of parts in the given fraction: $6$$6$
Number of parts making a whole: $4$$4$
The number of parts in the given fraction is greater than the number of parts making a whole.

The picture represents the fraction $\frac{6}{4}$$\frac{6}{4}$. The $4$$4$ parts of the given fraction is rearranged to make a whole and remaining $2$$2$ parts are shown nearby. So, $\frac{6}{4}$$\frac{6}{4}$ can be given as $1\frac{2}{4}$$1 \frac{2}{4}$.

naming them

The picture represents three fractions

•  Fraction given by green part: $\frac{1}{4}$$\frac{1}{4}$

•  Fraction given by purple parts : $\frac{6}{4}$$\frac{6}{4}$

•  Fraction given by orange parts : $1\frac{2}{4}$$1 \frac{2}{4}$

The word "fraction" means "part of a whole".

•  In the three given fractions, only $\frac{1}{4}$$\frac{1}{4}$ is strictly part of whole. The value of the fraction is less than $1$$1$, which is properly part of whole. Such fractions are called proper fractions.

•  The fraction $\frac{6}{4}$$\frac{6}{4}$ is greater than $1$$1$, and is represented as numerator by denominator. Such fractions are called improper fractions.

•  The fraction $1\frac{2}{4}$$1 \frac{2}{4}$ is greater than $1$$1$, and is represented as a whole number along with a fraction. Such fractions are called mixed fractions.

The word "proper" means: required or correct type. Proper fractions are fractions that are smaller than a whole and properly a fraction of a whole.

The word "improper" means: not of correct type. Improper fractions are fractions that are larger than a whole.

The word "mixed" means: consisting of different quantities or elements. Mixed fractions are fraction that have an integer count of whole and a proper fraction.

Proper Fraction: number of parts in the fraction (numerator) is less than the number of parts making a whole(denominator) given as numerator divided by denominator. Proper fractions are less than 1.

Improper Fraction: number of parts in the fraction (numerator) is greater than the number of parts making a whole(denominator) given as numerator by denominator. Improper fractions are greater than 1 given as numerator by denominator.

Mixed Fraction: Specified as number of wholes with a fraction. Mixed fractions are greater than 1 and given as whole number followed by a numerator by denominator.

examples

What type of fraction is $\frac{3}{7}$$\frac{3}{7}$?
The answer is 'proper fraction'.

What type of fraction is $\frac{17}{7}$$\frac{17}{7}$?
The answer is 'improper fraction'.

What type of fraction is $2\frac{3}{7}$$2 \frac{3}{7}$?
The answer is 'mixed fraction'.

What type of fraction is $7\frac{30}{35}$$7 \frac{30}{35}$?
The answer is 'mixed fraction'.

summary

»  Proper Fraction
→  fraction is smaller than the whole
→  eg: $\frac{2}{4}$$\frac{2}{4}$
»  Improper Fraction
→  fraction is larger than the whole
→  eg: $\frac{6}{4}$$\frac{6}{4}$
»  Mixed Fraction
→  a whole number and a fraction given together
→  eg: $1\frac{2}{4}$$1 \frac{2}{4}$

Outline


text:
# European XFEL Users' Meeting 2021 | DESY Photon Science Users' Meeting 2021

25-29 January 2021
ONLINE
Europe/Berlin timezone

## Abstracts of Talks

FLASH Session

Tuesday, 26 January 2021

14.00 -17.00

New Instrumentation at FLASH

R.Treusch, DESY

In this presentation I will briefly review last year’s operation under COVID-19 boundary conditions and then mainly focus on the new instrumentation features in the FLASH experimental halls. Topics are the new pulse-train laser at the PG beamlines, the TRIXS end station for time-resolved RIXS studies at beamline PG1 as well as the new split-and-delay unit at the FLASH2 beamline FL24.

Short info on the speaker:

1995                    PhD, Univ. of Hamburg
1998-2016:        Staff scientist, FLASH [former VUV-FEL]
since 2016:        Group Leader FS-FLASH-O, FLASH Scientific User Operations
Research fields: Free-Electron-Lasers, Beamlines + Diagnostics, Cond. Matter physics, AMO + Cluster physics, Diffraction Imaging (Scopus author ID: 6603772448, Orcid-ID: 0000-0001-8479-8862)

Single-shot temporal characterization of XUV pulses @FLASH

S. Düsterer, DESY

Results of single-shot temporal characterization of ultra-short XUV pulses generated by the free-electron laser FLASH will be presented. Using a THz field-driven streaking setup, the limits of this technique were investigated by employing different pulse durations from sub 10 fs to 350fs and different XUV wavelengths. Limits and possible error sources of the diagnostic method are discussed. Furthermore, the single-shot XUV pulse duration measurement allows the detailed investigation of the interplay between different properties of the strongly fluctuating self-amplified spontaneous emission (SASE) radiation. Correlations between pulse duration, pulse energy, spectral distribution and arrival time are explored in the experimental data as well as in simulations. Finally, an outlook on how such a system can be implemented as online photon diagnostic will be presented.

Short info on the speaker:

Studied in Würzburg and Austin, TX

PhD in Jena on laser plasma physics

Since 2003 member of the FLASH photon diagnostics team

Interests: Ultrafast dynamics, ultrahigh intensity interactions and  AMO physics

Ultrafast probing of molecular dynamics at the sulfur L-edge

M. Gühr, Univ. Potsdam

We probe the UV induced relaxation of the thionucleobase 2-thiouracil. This class of molecules shows an efficient and ultrafast relaxation into long-lived triplet states, contrasting with the ultrafast relaxation to the ground states observed in canonical nucleobases. This gives rise to interesting applications as photoinduced-cross linkers as well as problems related to its current use of thionucleobases as medication.

We investigate the dynamics of 2-thiouracil via x-ray probing at the sulfur L-edge using the new URSA-PQ instrument for gas-phase spectroscopy at FLASH [1]. We have performed time-resolved Auger spectroscopy that exhibits features of the expanding C-S bond of the molecule after photoexcitation [1]. Besides, we have performed sulfur 2p photoelectron spectroscopy that contains rich information about the electronic relaxation path. We interpret these results by a UV induced change of the local charge at the sulfur atom, which changes as the molecule relaxes from its photoexcited electronic state to lower-lying product states.

[1] URSA-PQ: a mobile and flexible pump-probe instrument for gas phase samples at the FLASH free electron laser, J. Metje, F. Lever, D. Mayer, R. J. Squibb, M. S. Robinson, M. Niebuhr, R. Feifel, S. Düsterer, M Gühr, Applied Sciences 10, 7882 (2020)

[2] Ultrafast dynamics of 2-thiouracil investigated by time-resolved Auger spectroscopy
F. Lever, D. Mayer, D. Picconi, J. Metje, S. Alisauskas, F. Calegari,  S. Düsterer, C. Ehlert, R. Feifel, M. Niebuhr, B. Manschwetus, M. Kuhlmann, T. Mazza, M. S. Robinson, R. J. Squibb, A. Trabattoni, M. Wallner, P. Saalfrank,T. J. A. Wolf, M Gühr, J. Phys. B 54, 014002 (2020)

Short info on the speaker:

PhD physics, FU Berlin (2005)

Postdoctoral Scholar Stanford University (2006-2007)

Staff, Associate and Senior Staff Scientist, SLAC (2007-2015)

Lichtenberg Professor (2015-2020)

Research fields: ultrafast x-ray science, molecular photoinduced dynamics, ultrafast electron scattering

Markus Gühr, Experimental Quantum Physics Group, Physics and Astronomy Institute, Universität Potsdam

www.exp-quantum.org

mguehr@uni-potsdam.de

Ultrafast Real-Time Dynamics of an Oxide Photocatalyst

H. Noei, DESY

--

Joint session European XFEL & DESY Photon Science Users´ Meeting 2021

Soft X-ray FEL experiments

Wednesday 27 January 2021

11.00 - 12.40

Dissociation of dynamics of small molecules

T. Jahnke, European XFEL, Schenefeld, Germany

The SQS-REMI endstation located at SASE3 of the European XFEL is in operation since early 2019. After commissioning, first user runs were conducted. The talk will present several examples of the first results obtained with this COLTRIMS reaction microscope. The first part will focus on Coulomb explosion imaging of water molecules in order to investigate the ultrafast structural dynamics following inner-shell ionization. In the second part, photoelectron diffraction imaging of the dissociation of molecular oxygen will be presented. The results suggest, that, using high repetition rate X-ray free electron lasers in combination with advanced electron/ion-coincidence momentum imaging approaches, time-resolved photoelectron diffraction imaging of single molecules in the gas phase should be routinely possible in the near future.

Short info on the speaker

till.jahnke@xfel.eu

Till Jahnke received his Ph.D. in Physics from the Goethe University Frankfurt in 2005. He became a Professor for experimental atomic physics in Frankfurt in 2017. His research interests cover the investigation of quantum dynamics in atoms and molecules employing synchrotron radiation, intense laser fields and (X-ray) free-electron laser light.

Observation of an Excitonic Mott Transition Through Ultrafast Core-cum-Conduction Photoemission Spectroscopy

M. Dendzik, KTH Stockholm, Sweden

Optoelectronic properties of semiconductors are largely governed by two types of excitations— excitons, the bosonic quasiparticles comprised of an electron and a hole bound by Coulomb interaction, and quasi-free carriers (QFCs) of single-particle character. The process of breaking excitons into QFCs, i.e. an excitonic Mott transition, has been quite elusive to observe due to its ultrafast nature. This talk will present a novel approach of studying the interaction between core electrons and excited carriers using time-resolved photoelectron spectroscopy. This approach enables distinguishing excitons from QFCs and tracking the evolution of an excitonic Mott transition on a femtosecond timescale.

Short info on the speaker

dendzik@kth.se

Research fields: 2D materials, topological insulators, time-and angle-resolved photoemission spectroscopy

Maciej Dendzik obtained his PhD in physics at the Physics Department of Aarhus University in Denmark. After a postdoctoral stay at the Fritz Haber Institute of the Max Planck Society in Berlin, he became a researcher at the Applied Physics Department of the Royal Technical Institute in Stockholm. His fields of expertise include studies of electronic structure of 2D materials and topological properties of matter. He is currently building a time-and angle- resolved photoemission spectroscopy setup in Stockholm. He has co-authored 30+ peer-reviewed publications with 1100+ citations (h-index=16).

Direct visualization of spin-lattice coupling in FePt nanoparticles

H. Dürr, Univ. Uppsala, Sweden

The dynamics of spins in magnetic materials initiated by a sub-picosecond laser pulse is a rapidly developing field in fundamental magnetism. The goal of this research is to understand and ultimately control the energy and angular momentum transfer processes in the laser-excited non-equilibrium state. The exploration of the excited-state electronic and magnetic structure has received much attention ever since femtosecond optical lasers have become available. However, understanding the coupling of spin excitations to the lattice is a relatively new area of exploration based on the availability of XFEL radiation in the tender and hard x-ray range. Here we use FePt nanoparticles, promising candidates for future high-density magnetic data storage media, to demonstrate the coupling of a ferromagnetic resonance spin precession mode to longitudinal acoustic phonons on a lengthscale of the nanoparticle size (~16nm). We isolate the phonon response using scattering of x-rays at the SCS instrument of the European XFEL that allows us to probe the ultrafast lattice expansion of FePt nanoparticles via coherent phonon wavepackets. We detect new modes due to non-linear coupling with large-angle spin precessions.

Short info on the speaker

PhD Physics, University of Bayreuth (1989)

Postdoctoral Scholar at Manchester University and Oak Ridge National Laboratory (1990-1994)

Staff Scientist at Daresbury Laboratory (1995-1999)

Senior Staff Scientist at Bessy GmbH  (2000-2009)

Senior Staff Scientist at SLAC National Accelerator Laboratory (2010-2018)

Since 2018 Professor of Instrumentation and Accelerator Physics, Department of Physics and Astronomy, Uppsala University

Research fields:

Ultrafast solid state spectrsocopy and scattering with x-rays and electrons probing electronic, spin and lattice degrees of freedom

European XFEL Users’ Meeting 2021 - Plenary Sessions

Wednesday, 13:30 - 19:00

X-ray Ptychography of Charge-Order Domains in High Temperature

Superconductors

Ian Robinson, University College London and Brookhaven National Lab

Thermally driven critical fluctuations are expected near a classical second-order phase

transition, which should slow down as the transition is approached. Coherent imaging with

single pulses of X-rays should be able to freeze these fluctuations and make a movie of them.

It is expected that in place of diffuse scattering associated with the transition, there would be

“speckled” diffraction indicative of critical domains associated with the fluctuations.

Observing these fluctuations is one of the science goals of the MID station, however with only

limited temperature control, it was decided to investigate a transition near room

temperature. We chose to look at a sample of La2-xSrxCuO4 (LSCO) for which the phase

transition between the high temperature tetragonal (HTT) phase and the low-temperature

orthorhombic (LTO) phase can be adjusted with the composition variable, x. We measured a

high quality epitaxial thin film of LSCO, x=0.07, which has its HTT-LTO transition at around

70°C, at MID over two beamtimes in 2019 and 2020. LSCO is the original High Temperature

Superconductor material discovered by Bednorz and Muller in 1986.

We found the sample was undamaged by the full SASE2 monochromatic beam, even close to

the 200nm focus of the “nafo” CRL optics, provided 30% attenuation was retained. This

surprising radiation immunity may have arisen from the presence of a thin 200nm gold film

electrode covering the sample, which could redistribute photoelectrons and reduce charging

effects; previously ferroelectric thin films were found to damage easily in a focussed XFEL

beam. High-visibility speckled diffraction patterns were clearly recorded in single shots

showing that any fluctuations were sufficiently frozen during the pulse. But the patterns were

found to different on ever shot, suggesting that the beam/sample positioning was unstable.

At all temperatures, the patterns repeated at random intervals suggesting this is not due to

sample fluctuations. Patterns which showed high correlation were averaged together to

improve statistics and the resulting partially-correlated groups could be assigned an overlap

distance using modelling as phase domains. This could lead to a ptychographic reconstruction

of the domains, despite having no information about the probe positions. Ptychographic

images of related materials, measured with coherent soft X-rays, show that the method works

for charge-density wave domains.

At the end of this presentation, we will introduce the possiblity that the speckle inversion “phase problem” may be amenable to Machine Learning approaches in the future. A large team of researchers helped with the experiment and contributed to the progress towards this common goal of visualizing domain fluctuations in crystals [1].

[1] L. Wu, T. A. Assefa, M. P. M. Dean, E. S. Bozin, Y. Cao, H. You, D. Sheyfer, S. Rosenkranz, P. G.

Evans, S. Marks, J. Diao, L. Gelisio, S. Banerjee, D. A. Keen, J. Hallmann, U. Boesenberg, M. Scholz, J.

Moeller, A. Madsen, I. Bozovic and I. K. Robinson to be published

Short info on the speaker

Ian Robinson is a group leader in the Condensed Matter Physics and Materials Science Department at Brookhaven National Laboratory and professor at the London Centre for

Nanotechnology, University College. His research is currently focussed on the development of coherent X-ray diffraction methods for imagige the structure of nanoparticles. His

research makes extensive use of synchrotron radiation and Free- ELectron Lasers. He built a beamline at Brookhaven to develop Surface X-ray Diffraction and a second one at Argonne for

Coherent X-ray Diffraction. One outcome of the work was the discovery of Crystal Truncation Rods, for which he was awarded the Surface Structure Prize in 2011 and the Gregori Aminoff

Prize in 2015.

Microscopic insight into ultrafast electronic and lattice excitations in metals and correlated oxides

Andrea Eschenlohr, Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE), University Duisburg-Essen, Germany

X-ray absorption spectroscopy (XAS) is a mature technique for deriving element- and chemically sensitive information on solids, in particular complex materials and heterostructures. It is therefore highly desirable to bring this powerful technique to the femto- to picosecond timescales of the elementary microscopic processes involving charge, spin and lattice dynamics in solids via optical pump – x-ray probe experiments at ultrashort pulse x-ray sources such as free electron lasers.

In this talk, I will discuss recent progress on implementing fs time-resolved XAS at the SCS instrument of European XFEL by means of a transmission zone plate and grating scheme. This setup allows for a simultaneous acquisition of the ground state and optically excited x-ray spectra as well as a reference signal for normalization of the data to the incident x-ray intensity, and thus provides excellent data quality in combination with kHz repetition rates.

By means of fs time-resolved XAS, we characterize the interaction of excited charge carriers and the lattice in Ni and NiO, which represent prototypical metallic respectively correlated magnetically ordered materials that are highly relevant for future applications in e.g. ultrafast spintronics. In Ni, characteristic transient spectral signatures at the L edges are linked to charge carrier excitation, and allow for the quantification of the electronic temperature, whereas the L3 edge satellite feature shows slower dynamics linked to lattice excitations. In NiO, we directly probe the dynamics of the valence and conduction band resulting from optical excitation of charge carriers at both the Ni L and O K edges, i.e. Ni 3d respectively O 2p states. The transient spectral features derived from this comprehensive analysis of both constituents of the oxide will be discussed in the context of the evolution of the excited charge carrier populations and their relaxation, showing the potential to gain microscopic insight into these fundamental processes in complex materials.

The results discussed in this talk were achieved with the collaborators of European XFEL community proposal 2161 and proposal 2589.

Short info on the speaker

Research fields:

* Femtosecond laser-induced dynamics of magnetically ordered and correlated solids and heterostructures

* Non-equilibrium charge and spin transfer at interfaces

* Ultrafast magnetization dynamics and optically induced spin transport

* Femtosecond time-resolved x-ray spectroscopy as well as linear and non-linear magneto-optical spectroscopy methods

Short CV:

Since 2020 Staff Scientist University Duisburg-Essen, Faculty of Physics and Center for Nanointegration Duisburg-Essen (CENIDE)

2013 - 2019 Research Assistant University Duisburg-Essen, Faculty of Physics

2012 PhD in Experimental Physics University Potsdam and Helmholtz Center Berlin for Materials and Energy

Stimulated x-ray Raman scattering probed by photon-recoil imaging

Ulli Eichmann, Max Born Institute, Berlin

Addressing the ultrafast coherent evolution of electronic wave functions has long been a goal of nonlinear x-ray physics. The investigation of stimulated x-ray Raman scattering (SXRS) using intense pulses from an x-ray free-electron laser can be seen as a first step toward this aim.  SXRS experiments so far have relied a great deal on signal amplification during pulse propagation through dense resonant media. For dilute samples, direct measurement of SXRS is hampered by a background attributable to the primary photons, which almost coincide with the scattered photons in momentum space.

In this talk I will present the photon-recoil imaging (PRI) method1 as an alternative access to SXRS. It is based on detecting the scattered neutral atoms rather than the scattered photons. PRI monitors the momentum transfer from the photons to the atoms by the deflection of their path in a supersonic atomic beam. The low momentum transfer in SXRS is used to discriminate against spontaneous x-ray Raman scattering, in which the momentum transfer is much larger. PRI also discriminates against abundant charged particles, which is crucial because competing processes such as multiphoton ionization populate highly charged ions at these pulse energies.

I will discuss our successful PRI measurements at the neon K edge performed at the SQS instrument of the European XFEL, which demonstrate the feasibility to detect SXRS on an individual atom level. A quantitative theoretical modelling using simulated XFEL pulses supports the experimental observations. As an outlook I will discuss future experiments using the two-color pulse option newly available at the European XFEL and the applicability of PRI to demonstrate SXRS on molecules.

1  U. Eichmann, H. Rottke, S. Meise, J.-E. Rubensson, J. Söderström, M. Agåker, C. Såthe, M. Meyer, T. M. Baumann, R. Boll, A. De Fanis, P. Grychtol, M. Ilchen, T. Mazza, J. Montano, V. Music, Y. Ovcharenko, D. E. Rivas, S. Serkez, R. Wagner, S. Eisebitt, Science 369,  1630 (2020)

Short info on the speaker

2012                   Adjunct Professor ( Ausserplanmäßiger Professor)

TU Berlin, Institute for Optics and Atomic Physics

2001                   Habilitation, Physics, TU Berlin

since 1993         Researcher, Max-Born Institute, Berlin

1992-1993         DFG research grant, NIST, Boulder, with Dr. D. J. Wineland

1991-1993         Scientific research assistant ( Hochschulassistent C1), Univ. of Freiburg

1986                    DAAD scholarship, Univ. of Virginia, Charlottesville, with Prof. T. F. Gallagher

1985-1990         Doctoral thesis:  Electron correlation in two-electron atoms, Univ. of Freiburg

Supervisor Prof.  W. Sandner

Current research interest: Atoms and molecules in strong laser fields

Nanoscale subsurface dynamics of solids upon high-intensity laser irradiation observed by femtosecond grazing-incidence x-ray scattering

M. Nakatsutsumi1,10, L. Randolph2, M. Banjafar1,3, J-P. Schwinkendorf1, T. R. Preston1, T. Yabuuchi4,5, M. Makita1, N. P. Dover6, C. Bähtz3, E. Brambrink1, Z. Chen7, B-I. Cho8, S. Göde1, H. Höppner3, Y. Inubushi4,5, G. Jakob9, J. Kaa1, A. Kon6, J. K. Koga6, D. Ksenzov2, T. Matsuoka10,11, M. Nishiuchi6, M. Paulus12, A. Pelka3, V. Recoules13, Ch. Rödel14, F. Schon2, K. Sueda5, Y. Sentoku11,15, T. Togashi4,5, T. Toncian3, L. Wollenweber1, M. Bussmann3, T. E. Cowan3, M. Kläui9, C. Fortmann-Grote1, A. P. Mancuso1,16, T. Kluge3 and C. Gutt2

1 European XFEL, Holzkoppel 4, 22869 Schenefeld, Germany

2 Universität Siegen, Walter-Flex-Str. 3, 57072 Siegen, Germany
3 Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, 01328, Dresden, Germany

4 Japan Synchrotron Radiation Research Institute (JASRI), Sayo, Hyogo 679-5198, Japan

5 RIKEN SPring-8 Center, Sayo, Hyogo 679-5148, Japan
6 QST-Kansai, KPSI,8-1-7 Umemi-dai, Kizugawa-city, Kyoto, 619-0215, Japan

7SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA

8 Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Republic of Korea

9 Universität Mainz, Staudinger Weg 7, 55128 Mainz, Germany

10 Open and Transdisciplinary Research Institute, Osaka University, Suita, Osaka 565-0087, Japan

11 Graduate School of Engineering, Osaka University, Suita, Osaka 565-0087, Japan

12Technische Universität Dortmund, August-Schmidt-Straße 1, 44227, Germany

13 CEA, DAM, DIF, 91297 Arpajon, France

14Helmholtz Institute Jena, Fröbelstieg 3, 07743 Jena, Germany

15 Institute of Laser Engineering, Osaka University, Suita, Osaka 565-0871, Japan

16Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086, Australia

The interaction of intense laser pulses with solid matter initiates ultrafast surface electron density modulations on the nanometre (nm) scale, which provides a basis for technological developments in areas from material processing, surface nano-structuring to relativistic plasma optics. Currently, a lack of appropriate surface and subsurface methodology to track density dynamics with sufficient spatial and temporal resolution restricts quantitative understanding, and eventual control, of the laser-solid interaction and the subsequent energy transport into the bulk. We recently proposed a novel method for in situ visualization of nanometer depth-resolved density dynamics by grazing-incidence x-ray diffuse scattering with an XFEL. Our first proof-of-principle experiment at SACLA facility showed how the surface ablation and density perturbation following the femtosecond laser pulse interaction with multilayer samples develop over time [1]. In addition, the first experiment using the PP laser at the HED instrument, where the laser-irradiated 50 nm thick gold sample was probed by the grazing-incidence x-ray small and wide scattering (GISAXS/GIWAXS), will be reported. This new methodology opens up new possibilities for accurate characterization of surface and subsurface dynamics in various applications including laser ablation, creation of warm-dense-matter, dynamic compression, and relativistic laser-plasmas.

[1] L. Randolph, M. Banjafar, T. R. Preston et al., arXiv preprint 2012.15076

Email of corresponding author: motoaki.nakatsutsumi@xfel.eu

Short information on the speaker

Dr. Nakatsutsumi earned a Ph.D. in Engineering at Osaka University in Japan in 2008 where his doctoral work was focused on laser-induced fast electron transport for the fast ignition scheme of inertial confinement fusion under the supervision of Prof. Ryosuke Kodama. He then worked on plasma optics, laser-induced proton acceleration and proton-heated warm dense matter at Laboratoire d'Utilisation des Lasers Intenses (LULI), Ecole Polytechnique, France (2008-2012) under the supervision of Dr. Julien Fuchs and Dr. Patrick Audebert. He joined the European XFEL, HED group in 2008 as the first instrument scientist under the supervision of Dr. Thomas Tschentscher, where he made a hutch design, concept of the x-ray and laser transport and wrote the Conceptual Design Report. He is currently working as a senior scientist at the HED instrument under the supervision of Dr. Ulf Zastrau with main responsibility on optical lasers. His current research interest is high-intensity laser-solid interaction, surface and subsurface dynamics and morphology, plasma optics and surface sensitive x-ray techniques.

Visualizing excited state structural and electronic dynamics in cobalamins

Roseanne J. Sension, Department of Chemistry, University of Michigan

The fate of a photoactive molecule is determined by the electronic and structural rearrangements that follow excitation.  Femtosecond (fs) X-ray free electron lasers (XFELs) have made it possible to use X-ray absorption and X-ray emission spectroscopies to probe changes in electronic configuration and atomic structure as a function of time, beginning from the initial excited state.  Both ‘movies’ of coherent or ballistic motion and ‘snaphots’ of local minima or kinetic intermediates are possible. Polarization anisotropy, long exploited in ultrafast optical measurements, permits decomposition of the X-ray transient difference signal into contributions along the direction parallel to the transition dipole initially pumped, and perpendicular to this transition dipole. This decomposition allows the analysis of asymmetric sequential structural changes of photoexcited molecules in isotropic solution.

We have used femtosecond X-ray absorption near edge structure (XANES) at the Co K-edge and transient X-ray Ka and Kb emission to characterize the excited state dynamics of two B12 vitamins, cyanocobalamin and aquocobalamin. The initial subpicosecond dynamics are found to be ballistic rather than kinetic, dominated by expansion of the axial bonds perpendicular to the ring. The transient XES measurement demonstrates that a change in electronic configuration involving the Co 3d orbitals accompanies the axial bond elongation as the molecule evolves from the initial ‘bright’ state to a ‘dark’ state within a hundred femtoseconds. The Finite Difference Method Near Edge Structure (FDMNES) program is used to calculate the XANES spectrum for both the ground and excited states. These simulations are used to extract more detailed static and dynamical information from the time- and polarization-resolved XANES difference spectra.

Short info on the speaker

Roseanne Sension has a PHD in Chemistry from The University of California, Berkeley (1986). She is currently a Professor of Chemistry and of Physics at the University of Michigan, Ann Arbor. Her research interests are in the fundamental photochemistry and photophysics of compounds capable of acting as optically driven devices. The primary emphasis of current research is on the development and use of ultrafast X-ray methods to visualize the atomic and electronic dynamics in these ultrafast chemical reactions.

3D diffractive imaging of nanoparticle ensembles using an x-ray laser

Kartik Ayyer,1,2,3,† P. Lourdu Xavier,1,3,4,† Johan Bielecki,5 Zhou Shen,6 Benedikt J. Daurer,6 Amit K. Samanta,4 Salah Awel,4 Richard Bean,5 Anton Barty,4 Martin Bergemann,5 Tomas Ekeberg,7 Armando D. Estillore,4 Hans Fangohr,5 Klaus Giewekemeyer,5 Mark S. Hunter,8 Mikhail Karnevskiy,5 Richard A. Kirian,9 Henry Kirkwood,5 Yoonhee Kim,5 Jayanath Koliyadu,5 Holger Lange,3,10 Romain Letrun,5 Jannik Lübke,3,4,11 Thomas Michelat,5 Andrew J. Morgan,12 Nils Roth,4,11 Tokushi Sato,5 Marcin Sikorski,5 Florian Schulz,10 John C. H. Spence,9 Patrik Vagovic,4,5 Tamme Wollweber,1,2,3 Lena Worbs,4,11 Oleksandr Yefanov,4 Yulong Zhuang,1,2 Filipe R. N. C. Maia,7,13 Daniel A. Horke,3,4,14 Jochen Küpper,3,4,11,15 N. Duane Loh,6,16 Adrian P. Mancuso,5,17 Henry N. Chapman3,4,11

1Max Planck Institute for the Structure and Dynamics of Matter, 22761 Hamburg, Germany

3The Hamburg Center for Ultrafast Imaging, Universität Hamburg, 22761 Hamburg, Germany

5European XFEL, 22869 Schenefeld, Germany

6Center for BioImaging Sciences, National University of Singapore, Singapore 117557, Singapore

7Department of Cell and Molecular Biology, Uppsala University, 75124 Uppsala, Sweden

8Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA

9Department of Physics, Arizona State University, Tempe, Arizona 85287, USA

10Institute of Physical Chemistry, Universität Hamburg, 20146 Hamburg, Germany

11Department of Physics, Universität Hamburg, 22761 Hamburg, Germany

12University of Melbourne, Physics, Melbourne, VIC 3010, Australia

13NERSC, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA

14Institute for Molecules and Materials, Radboud University, 6525 AJ Nijmegen, The Netherlands

15Department of Chemistry, Universität Hamburg, 20146 Hamburg, Germany

16Department of Physics, National University of Singapore, Singapore 117551, Singapore

17Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC 3086, Australia

†These authors contributed equally

X-ray single particle imaging (SPI) of biomolecules remains one of the outstanding goals of XFEL science. It can enable the determination of the structure and dynamics of individual particles at room temperature and near-atomic resolution without the need for crystallization. However, progress towards this goal has been slow due to the difficulty of collecting a sufficient number of low background diffraction patterns to achieve the requisite signal-to-noise ratio. Another hurdle on the analytical side remains the development of robust algorithms to classify heterogeneity in the sample.

In this talk, we report a proof-of-principle experiment on gold nanoparticles, overcoming both these hurdles. Using the high repetition-rate EuXFEL, 10 million diffraction patterns were collected in a single beamtime, and the inherent heterogeneity in the sample sets was disentangled to obtain 3D structures to better than 3-nm resolution, both of which are comfortably record-breaking values for this technique. This experiment should set the template for a new generation of X-ray SPI experiments, which fully utilize the parameters of the EuXFEL beam and the fast detectors.

Additionally, we will also discuss the classification of the full ensemble of patterns to understand the variability of 3D structures in each sample ensemble.

*Email of corresponding author: kartik.ayyer@mpsd.mpg.de

PETRA III and PETRA IV Session

Thursday 28 January 2021

13.00 – 17.30 hrs

Challenges in the design and construction of diffraction-limited synchrotron light sources

R. Bartolini, DESY

Experiments at PETRA IV: the route to the new beamline portfolio

C. Schroer, DESY

Ptychographic X-ray Speckle Tracking

Andrew James Morgan

Recent developments in layer deposition techniques have enabled the fabrication of a series of highly focusing X-ray lenses, known as wedged multi-layer Laue lenses. Improvements to the lens design and fabrication technique demand an accurate, robust, in situ and at-wavelength characterization method. To this end, a modified form of the speckle tracking wavefront metrology method has been developed. The ptychographic X-ray speckle tracking method is capable of operating with highly divergent wavefields. A useful by-product of this method is that it also provides high-resolution and aberration-free projection images of extended specimens. In this talk will outline the method and present recent results.

Short information on the speaker

Affiliation:  School of Physics, University of Melbourne, Parkville, Victoria 3010, Australia

Research fields: x-ray imaging, phase retrieval, data science, software development

Short CV:

• 2013 - PhD on x-ray and electron holographic imaging at the University of Melbourne
• 2013 - Teaching Associate at Monash University
• 2013-2018 - Postdoctoral Researcher at the Centre for Free-Electron Laser Science (DESY)
• 2018-2020 - Research Fellow in Biomolecular Imaging at the University of Melbourne
• 2021 - ARC Discovery Early Career Researcher at the University of Melbourne

Core–Shell Nanoparticle Interface and Wetting Properties

E. Malmström, KTH Stockholm, Sweden

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Understanding electrochemical switchability of perovskite-type exsolution catalysts

A. Opitz,TU Wien, Austria

Precipitating metallic nanoparticles from perovskite-type oxides upon applying reducing conditions is a highly promising approach to obtain oxide-supported catalysts with exceptional properties. This process is often called exsolution. On mixed ionic/electronic conducting oxide electrodes the obtained catalyst particles can be electrochemically switched between different activity states, which is a particularly interesting property of these novel catalysts.

In this work, the exsolution and re-oxidation of iron particles on perovskite-type mixed conducting La0.6Sr0.4FeO3-δ (LSF) electrodes was studied by synchrotron-based in-situ X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) at 625 °C in H2/H2O atmosphere. Upon cathodically polarizing the LSF electrodes – i.e. applying strongly reducing conditions – the formation of metallic α-Fe particles could be observed on the LSF surface. This change of the electrode surface chemistry was accompanied by a strong improvement of its electro-catalytic activity. In contrast, application of sufficiently high anodic polarization – i.e. oxidizing conditions – the oxidation of α-Fe to Fe1xO and Fe3O4 could be observed, accompanied by a drastic drop of the catalytic activity. This shows that re-integration of iron into the perovskite lattice is thus not required for obtaining a switchable catalyst. Rather, it is possible to reversibly switch between high and low activity state even though the exsolution process itself is irreversible.

To understand the origin of the high and low electro-catalytic activity, a mechanism is suggested which considers the different adsorption behavior of hydrogen on metallic iron and oxides. A consequence of this is that the presence of metallic iron particles establishes a novel reaction pathway that bypasses the rate limiting step on the bare oxide electrode surface, thus enabling the observed increase in electro-catalytic activity.

Short information on the speaker

Alexander K. Opitz

TU Wien, Institute of Chemical Technologies and Analytics

Getreidemarkt 9/164-EC, 1060 Vienna, Austria

Short CV

Since Nov. 2018 Assistant Prof. at TU Wien, Institute of Chemical Technologies & Analytics, Division Electrochemistry

Feb. – Sept. 2017 Visiting Scientist at MIT, Department of Nuclear Science and Engineering, Research Group of Prof. Bilge Yildiz.

Since 2014 Head of Research Group “Electrochemical Energy Conversion”

Aug. 2011 – Oct. 2018 University Assistant at TU Wien, Institute of Chemical Technologies & Analytics, Division Electrochemistry.

Aug. 2008 – Jul. 2011 PhD study at TU Wien. Title of thesis: „Oxygen Exchange Pathways of Platinum Model Electrodes on Yttria-stabilized Zirconia“

Main Research Areas

• Electrochemistry & Solid State Ionics: Study of electrode kinetics, current pathways, and electrochemically active zones of solid state electrochemical systems, high temperature electrolysis of H2O and CO2.

• Heterogeneous Catalysis: In-situ spectroscopic and analytic studies on the surface chemistry and catalytic activity of electrodes.

• Materials Chemistry: Synthesis and characterization of novel, alternative materials for solid oxide cells.

Superlattices of nanocluster and quantum dots: a playing field for exploiting structure-transport correlations

M. Scheele, Univ. Tübingen

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Functional supramolecular structures in infectious diseases mechanisms and therapy

M. Landau, CSSB/EMBL, Technion Haifa

Meytal Landau1,2, Yizhaq Engelberg1, Nimrod Golan1, Sergei Perov1, Nir Salinas1, Einav Tayeb-Fligelman1, Eilon Barnea1, and Peleg Ragonis1

1 Department of Biology, Technion - Israel Institute of Technology, Haifa, Israel

2 The European Molecular Biology Laboratory (EMBL), Hamburg, Germany

Protein fibrils that perform physiological activities, such as functional amyloids, could provide new therapeutic venues, mostly due to their roles as key virulence determinants in microbes, antimicrobial activities, and possible involvement in systemic and neurodegenerative diseases. Moreover, they display unique stability and tunable self-assembly, which could be used to design therapeutics with enhanced endurance, bioavailability and shelf-life, as well controlled activity. Yet, these fibrous proteins present great challenges in structural and functional studies due to their aggregative and partially disordered nature, and structural polymorphisms observed in similar and even identical sequences. Using X-ray micro-crystallography, we determined the first high resolution structures of bacterial amyloids involved in cytotoxicity, antibacterial activity and biofilm structuring [1-4]. The similar structures of biofilm-associated and human pathological amyloidogenic regions led to repurposing of anti-Alzheimer’s compounds to act against Salmonella biofilm. Moreover, the structural similarity implies on possible inter-species interactions that could have bearing on amyloid diseases by the creation of transmissible agents. In addition, we offer atomic-resolution insight into three fibril-forming antimicrobial peptides from bacteria, an amphibian and human [5-6], which featured unique morphologies, including novel types of protein fibrils composed of densely packed helices (Fig. 1). The self-assembly is critical for the antibacterial activity. We expect that a detailed molecular understanding of functional fibrils will provide the foundation for antimicrobial translational research and for elucidation of the etiology of and interactions between microbial and human ‘amylomes’ in health and disease.

The crystal structures of fibrils of two antimicrobial peptides from human (left) [5] and an amphibian (right) [6] are shown. Transmission electron micrographs show the interactions of the fibrils with bacterial cells.

[1]             Tayeb-Fligelman, E.; Tabachnikov, O.; Moshe, A.; Goldshmidt-Tran, O.; Sawaya, M.R.; Coquelle, N.; Colletier, J.P., and Landau, M., The cytotoxic Staphylococcus aureus PSMalpha3 reveals a cross-alpha amyloid-like fibril. Science 355, 831-833;2017

[2]             Salinas, N.; Colletier, J.P.; Moshe, A., and Landau, M., Extreme amyloid polymorphism in Staphylococcus aureus virulent PSMalpha peptides. Nat Commun, 9, 3512; 2018

[3]             Perov, S.; Lidor, O.; Salinas, N.; Golan, N.; Tayeb-Fligelman, E.; Deshmukh, M.; Willbold, D., and Landau, M., Structural Insights into Curli CsgA Cross-beta Fibril Architecture Inspire Repurposing of Anti-amyloid Compounds as Anti-biofilm Agents. PLoS Pathog, 15, e1007978; 2019

[4]             Tayeb-Fligelman, E.; Salinas, N.; Tabachnikov, O., and Landau, M., Staphylococcus aureus PSMalpha3 Cross-alpha Fibril Polymorphism and Determinants of Cytotoxicity. Structure 3;28(3):301-313; 2020.

[5]             Engelberg Y. and Landau M.. The Human LL-37(17-29) Antimicrobial Peptide Reveals a Functional Supramolecular Structure. Nat Commun 11, 3894; 2020

[6]             Salinas N., Tayeb-Fligelman E., Sammito M., Bloch D., Jelinek R., Noy D., Uson I., and Landau M. The Amphibian Antimicrobial Peptide Uperin 3.5 is a Cross-α/Cross-β Chameleon Functional Amyloid. PNAS 118 (3) e2014442118; 2021

Short info on the speaker

The European Molecular Biology Laboratory (EMBL), Hamburg, Germany

2019-present    Associate Professor

The Faculty of Biology at the Technion – Israel Institute of Technology

2012-2018 Assistant Professor

The Faculty of Biology at the Technion – Israel Institute of Technology

2013-2015         David and Inez Mayers Career Advancement Chair in Life Sciences Fellow

The Faculty of Biology at the Technion – Israel Institute of Technology

Professional Positions

2019-present    Visiting Scientist on one-year Sabbatical

Centre for Structural System Biology (CSSB) at the DESY campus, Hamburg, Germany

Affiliation: The European Molecular Biology Laboratory (EMBL)

Hosts: Profs. Kay Grünewald and Matthias Wilmanns

2007-2012         Post-doctoral scholar, University of California, Los Angeles, USA.

Subject: Structural investigation of amyloid proteins

2002-2007         Research assistant (support research with computational aspects)

The laboratory of Prof. Uri Seligsohn at the Amalia Biron Research Institute of Thrombosis and Hemostasis, Chaim Sheba Medical Center, Tel-Hashomer and Sackler Faculty of Medicine, Tel-Aviv University, Tel Aviv, Israel

Research Field: Functional fibrils, microbial amyloids, antimicrobials, X-ray crystallography, cryogenic electron microscopy

Extreme conditions crystallography: the status and the challenges

K. Glazyrin, DESY

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DESY Photon Science Users’ Meeting 2021 – Future DESY

Friday, 29 January 2021

09.00 – 12.30 hrs

Overview DESY Photon Science

E. Weckert, DESY

PETRA III and future outlook - PETRA IV

C. Schroer, DESY

The PETRA IV Machine Project

R. Bartolini, DESY

FLASH and future outlook – FLASH2020+

M. Beye, DESY

3D virtual histology of lung and heart tissue affected by severe causes of Covid-19

T. Salditt, Univ. Göttingen

Severe progression of Covid‐19 is frequently accompanied by lethal respiratory failure. The underlying lung injury can already be detected by radiographic chest imaging and clinical computed tomography (CT). However, in order to study disease mechanisms at the cellular level, a much higher resolution is required. For this purpose, the tissue obtained by surgical intervention or from a post mortem autopsy is cut into thin sections, stained and observed in an optical microscope. However, conventional histology suffers from some important limitations. Images are obtained only of two‐dimensional sections but not of the entire three‐dimensional (3D) volume. In order to accurately track the tree of blood vessels, to visualise alveolar morphology and to perform precise measurements of alveolar wall thickness which is important for gas exchange in the lung, the cyto‐architecture of the lung has to be visualised in 3D and at high resolution, after locating regions of interest such as inflammation sites. For this purpose, we have adapted phase‐contrast (PC) X‐ray computerised tomography (CT) such that three‐dimensional imaging tasks can be performed non‐destructively on lung autopsies or biopsies. We have used this new technique to investigate tissue samples from Covid‐19 patients, as well healthy control samples [1].
Using multi‐scale phase contrast X‐ray tomography we can augment the pathological
assessment and understanding of Covid‐10 pathophysiology based on detailed 3D
visualizations of diffuse alveolar damage (DAD) with its prominent hyaline membrane
formation, mapping out the distribution of immune cells infiltrating the tissue, and by
providing histograms of characteristic distances from tissue interior to the closest air
compartment. Most recently, we have extended this to investigations of heart tissue, which can also show severe damage of vasculature.

In this talk, I present the current status of the project, the pathological relevance, and the
technical challenges concerning data acquisition, reconstruction and analysis. I will finish
with an outlook on how 3D virtual histology and patho‐histology can be further developed and be applied to biomedical research.

[1] Marina Eckermann, Jasper Frohn, Marius Reichardt, Markus Osterhoff, Michael Sprung, Fabian
Westermeier, Alexandar Tzankov, Christopher Werlein, Mark Kühnel, Danny Jonigk, Tim Saldittt, 3D
virtual pathohistology of lung tissue from Covid‐19 patients based on phase contrast X‐ray
tomography. eLife 2020;9:e60408 doi: 10.7554/eLife.60408

Drug screening at PETRA III

A. Meents, DESY

Report of the ‘DESY Photon Science User Committee’ (DPS-UC)

P. Müller- Buschbaum, DPS-UC Chair

Report of the ‚Committee Research with Synchrotron Radiation’ (KFSor why is the KFS important?

J.-D. Grunwaldt, KFS, Chair, KIT Karlsruhe

The Committee Research with Synchrotron Radiation (“Komitee Forschung mit Synchrotronstrahlung" (KFS), Link see [1]) is an elected body which represents the interest of more than 4000 synchrotron radiation users (including FEL) in Germany.

Our aim is to act as a link between users and the facilities, between the users and the funding agencies, between Germany and Europe and international sources. In particular, we help to coordinate and to develop strategies for synchrotron radiation applications at national and international sources such as outlined in the recently published strategy paper (“Light for the future” [2]). We want to promote synchrotron research, networking and support especially young enthusiastic researchers and initiatives like NFDI, ErUM-Data and “BMBF-Verbundforschung“ (ErUM-Pro).

The new KFS has been set up very recently in December 2020 after the election in autumn 2020. The following scientists were elected as members for the next three years:

Jan-Dierk Grunwaldt (chair, Karlsruhe Institute of Technology)

Sarah Köster (vice chair, University of Göttingen)

Bridget Murphy (University of Kiel)

Birgit Kanngießer (Technical University of Berlin)

Andrea Thorn (University of Hamburg)

Christian Gutt (University of Siegen)

Taisia Gorkhover (University of Hamburg)

Dirk Lützenkirchen-Hecht (University of Wuppertal)

In addition, guests representing the German photon facilities BESSY II, DELTA, KIT-Synchrotron, PETRA III, FLASH and the European facilities ESRF and the European XFEL, representatives from funding agencies, PT-DESY and further experts are members.

Do you have topics to be discussed? We are open for opinions, suggestions and questions. Do not hesitate to contact us (Karin Griewatsch, kfsadmin@sni-portal.de).

References:

[2] Strategy-Brochure: https://www.sni-portal.de/en/news/new-strategy-brochure-of-the-kfs

Short info on the speaker:

Chair of the 12. KFS, Full professor at Karlsruhe Institute of Technology since 2010, www.itcp.kit.edu/grunwaldt

Report of the ‘European synchrotron and FEL user organisation’ (ESUO)

U. Pietsch, ESUO Chair, Uni. Siegen


text:
## 7.7 RenewLock Method

The lock timer is automatically renewed whenever the initiator of the lock issues a request for the locked element or while Nodes of the locked element are subscribed to. RenewLock is used to reset the lock timer to the value of the MaxInactiveLockTime Property and prevent the Server from automatically removing the lock. This Method may only be called from the same Application which initiated the lock.

The signature of this Method is specified below. Table 61 and Table 62 specify the arguments and AddressSpace representation, respectively.

Signature

RenewLock(
[out] Int32      RenewLockStatus);

Table 61 – RenewLock Method Arguments

Argument Description
RenewLockStatus 0 – OK
-1 – E_NotLocked – the Object is not locked

Table 62 – RenewLock Method AddressSpace definition

Attribute Value
BrowseName RenewLock
References NodeClass BrowseName DataType TypeDefinition ModellingRule
HasProperty Variable OutputArguments Argument[] PropertyType Mandatory


text:
## Calculus 10th Edition

$$V=\frac{15}{2}\pi$$
r=$\sqrt x$ $V=\pi\int\limits_1^4(\sqrt x)^2 dx$ $V=\pi\int\limits_1^4(x)dx$ $V=\pi\frac{x^2}{2}│_1^4$ $V=\pi (\frac{4^2}{2}-\frac{1^2}{2})$ $V=\pi(\frac{16}{2}-\frac{1}{2})$ $V=\frac{15}{2}\pi$