Numerické optimalizace experimentů NMR pevné fáze

Numerical optimizations of solid-state nuclear magnetic resonance experiments are one of the possible solutions to its low sensitivity. Using the Average Hamiltonian Theory, the negative effects of the radiofrequency field inhomogeneity on magnetization transfer were investigated. To overcome these effects, the Average Hamiltonian Theory was employed in the optimization of commonly used techniques such as Ramp-CP and Adiabatic-CP, optimization of pulses with arbitrarily modulated amplitude and new periodic pulses with arbitrarily modulated amplitudes and phases. Both types of shaped pulses achieved significantly higher efficiencies than Ramp- CP and Adiabatic-CP. The highest efficiency enhancement was calculated at high spinning frequencies and low dipolar coupling constants where the effect of the inhomogeneity is the strongest.Numerické optimalizácie experimentov nukleárnej magnetickej rezonancie pevnej fázy sú jedným z možných riešení nízkej citlivosti tejto metódy. Využitím teórie priemerného Hamiltoniánu boli preskúmané negatívne vplyvy nehomogenity rádiofrekvenčných polí na prenos magnetizácie medzi jadrami. Následne, za účelom ich prekonania, bola táto teória využitá na optimalizáciu bežne používaných techník Ramp-CP a Adiabatic-CP, pulzov s ľubovoľne modulovanou amplitúdou, aj úplne nových, periodických pulzov s ľubovoľnou amplitúdou a fázou. Obidva typy tvarovaných pulzov dosahujú výrazne vyššie teoretické účinnosti, než zaužívané techniky. K najvýznamnejšiemu nárastu účinnosti došlo pri vysokých rýchlostiach rotácie vzorky a nízkych dipól-dipólových interakčných konštantách, kedy je vplyv nehomogenity rádiofrekvenčných polí najvýraznejší.Katedra fyzikální a makromol. chemieDepartment of Physical and Macromolecular ChemistryFaculty of SciencePřírodovědecká fakult

Performance of the cross-polarization experiment in conditions of radiofrequency field inhomogeneity and slow to ultrafast magic angle spinning (MAS)

In this paper, we provide an analytical description of the performance of the cross-polarization (CP) experiment, including linear ramps and adiabatic tangential sweeps, using effective Hamiltonians and simple rotations in 3D space. It is shown that radiofrequency field inhomogeneity induces a reduction in the transfer efficiency at increasing magic angle spinning (MAS) frequencies for both the ramp and the adiabatic CP experiments. The effect depends on the ratio of the dipolar coupling constant and the sample rotation frequency. In particular, our simulations show that for small dipolar couplings (1 kHz) and ultrafast MAS (above 100 kHz) the transfer efficiency is below 40 % when extended contact times up to 20 ms are used and relaxation losses are ignored. New recoupling and magnetization transfer techniques that are designed explicitly to account for inhomogeneous radiofrequency fields are needed.</p

CubeSats in Support of Astrophysics, GRBAlpha and Beyond

Space science, including the field of astrophysics, is continuously finding innovative use cases for small satellites and CubeSat platforms. These missions support efforts in the democratisation and improved accessibility of space technologies. GRBAlpha, as one of such missions, is a 1U CubeSat carrying an experimental payload for the detection of gamma-ray bursts (GRB)

GRBAlpha: the smallest astrophysical space observatory -- Part 1: Detector design, system description and satellite operations

Aims. Since launched on 2021 March 22, the 1U-sized CubeSat GRBAlpha operates and collects scientific data on high-energy transients, making it the smallest astrophysical space observatory to date. GRBAlpha is an in-obit demonstration of a gamma-ray burst (GRB) detector concept suitably small to fit into a standard 1U volume. As it was demonstrated in a companion paper, GRBAlpha adds significant value to the scientific community with accurate characterization of bright GRBs, including the recent outstanding event of GRB 221009A. Methods. The GRB detector is a 75x75x5 mm CsI(Tl) scintillator wrapped in a reflective foil (ESR) read out by an array of SiPM detectors, multi-pixel photon counters by Hamamatsu, driven by two separate, redundant units. To further protect the scintillator block from sunlight and protect the SiPM detectors from particle radiation, we apply a multi-layer structure of Tedlar wrapping, anodized aluminium casing and a lead-alloy shielding on one edge of the assembly. The setup allows observations of gamma radiation within the energy range of 70-890 keV with an energy resolution of ~30%. Results. Here, we summarize the system design of the GRBAlpha mission, including the electronics and software components of the detector, some aspects of the platform as well as the current way of semi-autonomous operations. In addition, details are given about the raw data products and telemetry in order to encourage the community for expansion of the receiver network for our initiatives with GRBAlpha and related experiments.Comment: Accepted for publication in Astronomy & Astrophysics, 9 pages, 10 figure

Použití paralelních výpočtů v datově-intenzivních úlohách

This thesis studies, develops, and investigates the optimization of data-intensive sci- entific algorithms using Graphics Processing Units (GPUs) to enhance performance and scalability. The first part of the thesis focuses on the design and implementation of optimized kernels for four key algorithms: hierarchical clustering with Mahalanobis link- age, neighborhood-based dimensionality reduction through EmbedSOM, optimization of cross-correlation algorithms for many small inputs, and stochastic simulation of Boolean networks. In the second part, the thesis builds upon the findings of the first part to propose a Noarr library, which enables the efficient development of high-performance computing (HPC) applications. It emphasizes the critical role of memory optimization in achieving significant performance improvements in HPC and aims to streamline the implementation of these optimizations by providing a novel memory layout and traversal optimization framework. The main contributions of this thesis comprise the implementa- tion of novel GPU optimization techniques, performance improvements of scientific tools of up to three orders of magnitude speedup, advancing data analysis and visualization in bioinformatics and material physics, and the design of new tools for efficient expression of data structure layout...Táto práca študuje, vyvíja a skúma optimalizáciu dátovo náročných vedeckých algo- ritmov pomocou grafických procesorových jednotiek (GPU) na zvýšenie výkonu a šká- lovateľnosti. Prvá časť práce je zameraná na návrh a implementáciu optimalizovaných programov pre štyri kľúčové algoritmy: hierarchické klastrovanie s Mahalanobisovou vz- dialenosťou, redukciu dimenzionality pomocou EmbedSOM, optimalizáciu algoritmu vzá- jomnej korelácie pre mnoho malých vstupov a stochastickú simuláciu booleovskej siete. V druhej časti práca nadväzuje na zistenia z prvej časti a navrhuje knižnicu Noarr, ktorá umožňuje efektívny vývoj vysoko-výkonneho softwéru. Zdôrazňuje kritickú úlohu opti- malizácie pamäte pri dosahovaní významných zlepšení výkonu a jej cieľom je zefektívniť implementáciu týchto optimalizácií poskytnutím nového nástroja na rozloženie pamäte a jej prechodu. Medzi hlavné prínosy tejto práce patrí implementácia nových techník optimalizácie GPU, vylepšenia výkonu vedeckých nástrojov až o tri rády, pokročilá ana- lýza a vizualizácia údajov v bioinformatike a fyzike materiálov a návrh nových nástrojov na efektívne vyjadrenie rozloženia a prechodu dátových štruktúr vo vysoko-výkonnom kóde. Výsledky tejto práce môžu byť použité na zlepšenie procesu vývoja udržiavateľných a efektívnych aplikácií a na usmernenie...Department of Software EngineeringKatedra softwarového inženýrstvíFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult