Konformně provázané prostoročasy

Hlavným cieľom tejto práce je skúmať možnosť generovania Robinsonových- Trautmanových priestoročasov z Kundtovej triedy geometrií. V prvej kapitole tejto práce zhŕňame poznatky o Robinsonových-Trautmanových a Kundtových geometriách v ľubovoľnej dimenzii. Názorne zavádzame súradnice adaptované na nulovú foliáciu priestoročasu generovanú netwistujúcou bezshearovou afinne pa- rametrizovanou nulovou geodetickou kongruenciou. Ďalej sumarizujeme poznatky o konformných transformáciách všeobecných geometrií a detailne ukazujeme kon- formný vzťah medzi Robinsonovou-Trautmanovou a Kundtovou triedou priesto- ročasov. V záverečnej kapitole sa s použitím tohto konformného vzťahu snažíme nájsť príklady riešenia rovníc gravitačného poľa v Einsteinovej všeobecnej relati- vite a štvorrozmernej kvadratickej gravitácii. 1The main objective of this thesis is to investigate the possibility of creating Robinson-Trautman spacetimes from Kundt class of geometries. In the first chap- ter, properties of the Robinson-Trautman and Kundt geometries in arbitrary dimension are summarised. Natural coordinates adapted to the null spacetime foliation generated by non-twisting shear-free affinely parametrized null geodesic congruence are introduced. In the following chapter, general conformal trans- formation and specific conformal relation between the Robinson-Trautman and Kundt classes of spacetimes is discussed. Finally, attempts to find solutions to the field equations by employing this conformal relation in Einstein's theory of gravity as well as in 4-dimensional quadratic gravity are shown in the last chapter. 1Institute of Theoretical PhysicsÚstav teoretické fyzikyMatematicko-fyzikální fakultaFaculty of Mathematics and Physic

North-South Distribution of Solar Flares during Cycle 23

In this paper, we investigate the spatial distribution of solar flares in the northern and southern hemisphere of the Sun that occurred during the period 1996 to 2003. This period of investigation includes the ascending phase, the maximum and part of descending phase of solar cycle 23. It is revealed that the flare activity during this cycle is low compared to previous solar cycle, indicating the violation of Gnevyshev-Ohl rule. The distribution of flares with respect to heliographic latitudes shows a significant asymmetry between northern and southern hemisphere which is maximum during the minimum phase of the solar cycle. The present study indicates that the activity dominates the northern hemisphere in general during the rising phase of the cycle (1997-2000). The dominance of northern hemisphere is shifted towards the southern hemisphere after the solar maximum in 2000 and remained there in the successive years. Although the annual variations in the asymmetry time series during cycle 23 are quite different from cycle 22, they are comparable to cycle 21.Comment: 6 pages, 2 figures, 1 table; Accepted for the publication in the proceedings of international solar workshop held at ARIES, Nainital, India on "Transient Phenomena on the Sun and Interplanetary Medium" in a special issue of "Journal of Astrophysics and Astronomy (JAA)

Study of Distribution and Asymmetry of Solar Active Prominences During Solar Cycle 23

In this paper we present the results of a study of the spatial distribution and asymmetry of solar active prominences (SAP) for the period 1996-2007 (solar cycle 23). For more meaningful statistical analysis we have analysed the distribution and asymmetry of SAP in two subdivisions viz. Group1 (ADF, APR, DSF, CRN, CAP) and Group2 (AFS, ASR, BSD, BSL, DSD, SPY, LPS). The north-south (N-S) latitudinal distribution shows that the SAP events are most prolific in the 21-30degree slice in the northern and southern hemispheres and east-west (E-W) longitudinal distribution study shows that the SAP events are most prolific (best visible) in the 81-90degree slice in the eastern and western hemispheres. It has been found that the SAP activity during this cycle is low compared to previous solar cycles. The present study indicates that during the rising phase of the cycle the number of SAP events were roughly equal on the north and south hemispheres. However, activity on the southern hemisphere has been dominant since 1999. Our statistical study shows that the N-S asymmetry is more significant then the E-W asymmetry.Comment: 21 pages 5 figures; Published online; 02 October, 2009; Solar Physics Journa

On the use of multilayer Laue lenses with X-ray Free Electron Lasers

Multilayer Laue lenses were used for the first time to focus x-rays from an X-ray Free Electron Laser (XFEL). In an experiment, which was performed at the European XFEL, we demonstrated focusing to a spot size of a few tens of nanometers. A series of runs in which the number of pulses per train was increased from 1 to 2, 3, 4, 5, 6, 7, 10, 20 and 30 pulses per train, all with a pulse separation of 3.55 us, was done using the same set of lenses. The increase in the number of pulses per train was accompanied with an increase of x-ray intensity (transmission) from 9% to 92% at 5 pulses per train, and then the transmission was reduced to 23.5 % when the pulses were increased further. The final working condition was 30 pulses per train and 23.5% transmission. Only at this condition we saw that the diffraction efficiency of the MLLs changed over the course of a pulse train, and this variation was reproducible from train to train. We present the procedure to align and characterize these lenses and discuss challenges working with the pulse trains from this unique x-ray source

Rapid sample delivery for megahertz serial crystallography at X-ray FELs

Liquid microjets are a common means of delivering protein crystals to the focus of X-ray free-electron lasers (FELs) for serial femtosecond crystallography measurements. The high X-ray intensity in the focus initiates an explosion of the microjet and sample. With the advent of X-ray FELs with megahertz rates, the typical velocities of these jets must be increased significantly in order to replenish the damaged material in time for the subsequent measurement with the next X-ray pulse. This work reports the results of a megahertz serial diffraction experiment at the FLASH FEL facility using 4.3 nm radiation. The operation of gas-dynamic nozzles that produce liquid microjets with velocities greater than 80 m s-1 was demonstrated. Furthermore, this article provides optical images of X-ray-induced explosions together with Bragg diffraction from protein microcrystals exposed to trains of X-ray pulses repeating at rates of up to 4.5 MHz. The results indicate the feasibility for megahertz serial crystallography measurements with hard X-rays and give guidance for the design of such experiments

Megahertz pulse trains enable multi-hit serial femtosecond crystallography experiments at X-ray free electron lasers

The European X-ray Free Electron Laser (XFEL) and Linac Coherent Light Source (LCLS) II are extremely intense sources of X-rays capable of generating Serial Femtosecond Crystallography (SFX) data at megahertz (MHz) repetition rates. Previous work has shown that it is possible to use consecutive X-ray pulses to collect diffraction patterns from individual crystals. Here, we exploit the MHz pulse structure of the European XFEL to obtain two complete datasets from the same lysozyme crystal, first hit and the second hit, before it exits the beam. The two datasets, separated by <1 µs, yield up to 2.1 Å resolution structures. Comparisons between the two structures reveal no indications of radiation damage or significant changes within the active site, consistent with the calculated dose estimates. This demonstrates MHz SFX can be used as a tool for tracking sub-microsecond structural changes in individual single crystals, a technique we refer to as multi-hit SFX

Segmented flow generator for serial crystallography at the European X-ray free electron laser

Serial femtosecond crystallography (SFX) with X-ray free electron lasers (XFELs) allows structure determination of membrane proteins and time-resolved crystallography. Common liquid sample delivery continuously jets the protein crystal suspension into the path of the XFEL, wasting a vast amount of sample due to the pulsed nature of all current XFEL sources. The European XFEL (EuXFEL) delivers femtosecond (fs) X-ray pulses in trains spaced 100 ms apart whereas pulses within trains are currently separated by 889 ns. Therefore, continuous sample delivery via fast jets wastes >99% of sample. Here, we introduce a microfluidic device delivering crystal laden droplets segmented with an immiscible oil reducing sample waste and demonstrate droplet injection at the EuXFEL compatible with high pressure liquid delivery of an SFX experiment. While achieving ~60% reduction in sample waste, we determine the structure of the enzyme 3-deoxy-D-manno-octulosonate-8-phosphate synthase from microcrystals delivered in droplets revealing distinct structural features not previously reported

Применение программного продукта «Яндекс.Сервер» для организации поиска в электронном каталоге библиотеки

The huge amounts of information accumulated by libraries in recent years put before developers a problem of the organization of fast and qualitative search which decision is possible with the use of modern search tools of Web-technology. The author examines one of these tools the software product “Yandex. Server”, allowing to organize optimum search in the electronic library catalog. The software product “Yandex. Server” gives a chance to carry out optimum search taking into account morphology of Russian and English languages, as well as the various logical conditions that provides effective and flexible search in the electronic library catalog.Накопленные библиотеками за последние годы огромные массивы информации ставят перед разработчиками задачу организации быстрого и качественного поиска, решение которой возможно с использованием современных поисковых инструментов веб-технологии. Автор рассматривает один из таких инструментов - программный продукт «Яндекс. Сервер», позволяющий организовать оптимальный поиск в электронном каталоге библиотеки с учетом морфологии русского и английского языков, а также различных логических условий

Schwarzschild-Bach black holes

Šimon Knoška The spherically symmetric spacetimes represent one of the most important classes of solutions in general relativity. Therefore, it is very natural to study them also in the context of modified theories of gravity. We directly continue in the previous works in quadratic gravity, where the generalised solutions with the constant Ricci scalar were found in the form of power series expansion in the conformal coordinates. In this work, we have found an alternative expression of this solution in the Robinson-Trautman-like coordinates analogously in the form of power series expansion around the horizon. Al- though the prescribed recurrent power series solution is more complicated than that in the conformal-to-Kundt coordinates, it posses numerous advantages. Namely, the trans- formation to the Schwarzschild-like coordinates is considerable simple and the physical interpretation of the coordinates is more evident. These properties are demonstrated in the preliminary investigation of the geodesic motion of the test particles near the black hole with analysis of the effect of the so-called Bach parameter. In particular, we have observed that the Bach parameter together with the positive cosmological constant Λ > 0 has a significant impact on the global structure of the spacetime

Schwarzschildovy-Bachovy černé díry

Šimon Knoška Sféricky symetrické priestoročasy reprezentujú jednu z najvýznamnejších tried riešení vo všeobecnej teórii relativity. Preto je prirodzené skúmať ich aj v kontexte modifiko- vaných teórií gravitácie. Priamočiaro pokračujeme v predchádzajúcej práci na kvadrat- ickej gravitácii, v ktorej boli objavené zovšeobecnené riešenia s konštantným Ricciho skalárom vo forme mocninného rozvoja v konformných súradniciach. V tejto práci sme našli alternatívne vyjadrenie tohto riešenia v Robinsonových-Trautmanových súradnici- ach taktiež v podobne mocninného rozvoja, a to v okolí horizontu. Napriek tomu, že predpísané rekurentné riešenie je komplikovanejšie než to zapísané v súradniciach kon- formných ku kundtovským, oplývajú tieto súradnice mnohými výhodami. Menovite, transformácia do schwarzschildovských súradníc je pomerne jednoduchá a fyzikálna in- terpretácia súradníc je očividnejšia. Tieto vlastnosti sú demonštrované predbežným skú- maním geodetického pohybu testovacích častíc v blízkosti čiernej diery v závislosti od takzvaného Bachovho parametru. Ďalej sme pozorovali, že Bachov parameter spolu s kladnou kozmologickou konštantnou Λ > 0 má významný vplyv na globálnu štruktúru priestoročasu.Šimon Knoška The spherically symmetric spacetimes represent one of the most important classes of solutions in general relativity. Therefore, it is very natural to study them also in the context of modified theories of gravity. We directly continue in the previous works in quadratic gravity, where the generalised solutions with the constant Ricci scalar were found in the form of power series expansion in the conformal coordinates. In this work, we have found an alternative expression of this solution in the Robinson-Trautman-like coordinates analogously in the form of power series expansion around the horizon. Al- though the prescribed recurrent power series solution is more complicated than that in the conformal-to-Kundt coordinates, it posses numerous advantages. Namely, the trans- formation to the Schwarzschild-like coordinates is considerable simple and the physical interpretation of the coordinates is more evident. These properties are demonstrated in the preliminary investigation of the geodesic motion of the test particles near the black hole with analysis of the effect of the so-called Bach parameter. In particular, we have observed that the Bach parameter together with the positive cosmological constant Λ > 0 has a significant impact on the global structure of the spacetime.Institute of Theoretical PhysicsÚstav teoretické fyzikyMatematicko-fyzikální fakultaFaculty of Mathematics and Physic