Search for sources of gamma radiation

Práce se zabývá aplikací metaheuristického algoritmu GLNS v praktické úloze - hledání zdrojů gama záření. Přesná pozice zdroje záření může být určena robotem nesoucím detektor, pokud projede v jeho blízkém okolí po trajektorii odpovídající kruhovému oblouku. V obecném případě je zdrojů radiace více a každý z nich může být detekován průjezdem mnoha různými oblouky, což umožňuje po vhodné diskretizaci formulaci úlohy jako zobecněného problému obchodního cestujícího. Je dáno m množin (zdrojů radiace) a n vrcholů (kruhových oblouků), rozdělených do m množin. Cílem je najít takovou sekvenci vrcholů, aby výsledná trajektorie byla co nejkratší. Za tímto účelem byl modifikován a implementován algoritmus GLNS, který je založen na heuristickém adaptivním prohledáváním širokého okolí aktuálního řešení problému. Plánovač je rozšířen o možnost plánování s kubickými křivkami jakožto hranami, které navíc dodržují definovanou maximální křivost. Zároveň je představen postup, jak pro účely plánování odhadovat jejich délku, namísto časově náročnější přesné kalkulace. Dále je do algoritmu přidána intenzifikační metoda zvaná DenseOpt, která lokálně optimalizuje výslednou trajektorii získanou diskrétním plánovačem, čehož je docíleno prohledáváním spojitého prostoru přípustných vrcholů v blízkém okolí vrcholů diskrétního řešení.This thesis documents the application of a metaheuristic algorithm GLNS on practical task - search for sources of gamma radiation. An individual source of radiation can be precisely located by a robot carrying a detector if it passes nearby through a trajectory segment, represented by a circular arc. As there can be more than one potential source of radiation and there are many valid arcs for each of them, the trajectory planning task can be after discretization formulated as Generalized Traveling Salesman Problem with m sets (sources) and n vertices (arcs), partitioned into these m sets. The goal is to find a tour, that visits each set exactly once and has a minimum length. For this purpose, an adaptive large neighborhood search algorithm GLNS is modified and implemented. Additionally, the planner is adapted to plan with cubic curves with predefined minimal curvature as edges, and a procedure for fast estimation of their weights is presented. Moreover, we propose a new intensification procedure called DenseOpt, which serves to improve the quality of the solution obtained from the discrete planner by performing a local search in the continuous space

The Hamiltonian Cycle and Travelling Salesperson problems with traversal-dependent edge deletion

Variants of the well-known Hamiltonian Cycle and Travelling Salesperson problems have been studied for decades. Existing formulations assume either a static graph or a temporal graph in which edges are available based on some function of time. In this paper, we introduce a new variant of these problems inspired by applications such as open-pit mining, harvesting and painting, in which some edges become deleted or untraversable depending on the vertices that are visited. We formally define these problems and provide both a theoretical and experimental analysis of them in comparison with the conventional versions. We also propose two solvers, based on an exact backward search and a meta-heuristic solver, and provide an extensive experimental evaluation

A systematic review of biomarkers among hospitalized patients with COVID-19 predictive of venous thromboembolism: A communication from the Predictive and Diagnostic Variables Scientific and Standardization Committee of the ISTH

Background Thrombosis is reported to occur more often among patients with COVID-19 than otherwise expected in the setting of viral pneumonia and sepsis. Systemic inflammatory biomarkers may be associated with venous thromboembolism (VTE) risk. The ISTH subcommittee on Predictive and Diagnostic Variables in Thrombotic Disease aimed to report the evidence on prognostic biomarkers for VTE in hospitalized patients with COVID-19. Methods Using a standardized Preferred Reporting Items for Systematic Reviews and Meta-analysis methodology, we conducted a systematic literature review to identify studies reporting prognostic biomarkers for VTE among hospitalized patients with COVID-19. Eligible studies included adults hospitalized with COVID-19 and reported the prognostic associations between any biomarker measured on admission, and the subsequent diagnosis of deep vein thrombosis or pulmonary embolism. Two authors reviewed titles and abstracts, and three authors extracted study data and performed review of bias. Results were displayed descriptively. Meta-analysis was not possible. Results From the initial 196 identified studies, full-text review was performed for 72 studies. Admission D-dimer levels were associated with VTE during hospitalization in five studies, and elevated platelet count was associated with VTE during hospitalization in one study. The risk of bias ranged from low to high for included studies. Overall, there was a paucity of high-quality prognostic studies. Studies on other biomarkers did not meet the systematic review inclusion criteria. Conclusions Admission D-dimer was associated with VTE diagnosis during hospitalization for COVID-19; however, prospective validation of this finding is needed to identify optimal D-dimer thresholds to guide VTE prophylaxis measures

Observation of a Coherence Length Effect in Exclusive Rho^0 Electroproduction

Exclusive incoherent electroproduction of the rho^0(770) meson from 1H, 2H, 3He, and 14N targets has been studied by the HERMES experiment at squared four-momentum transfer Q**2>0.4 GeV**2 and positron energy loss nu from 9 to 20 GeV. The ratio of the 14N to 1H cross sections per nucleon, known as the nuclear transparency, was found to decrease with increasing coherence length of quark-antiquark fluctuations of the virtual photon. The data provide clear evidence of the interaction of the quark- antiquark fluctuations with the nuclear medium.Comment: RevTeX, 5 pages, 3 figure

Determination of the Deep Inelastic Contribution to the Generalised Gerasimov-Drell-Hearn Integral for the Proton and Neutron

The virtual photon absorption cross section differences [sigma_1/2-sigma_3/2] for the proton and neutron have been determined from measurements of polarised cross section asymmetries in deep inelastic scattering of 27.5 GeV longitudinally polarised positrons from polarised 1H and 3He internal gas targets. The data were collected in the region above the nucleon resonances in the kinematic range nu < 23.5 GeV and 0.8 GeV**2 < Q**2 < 12 GeV**2. For the proton the contribution to the generalised Gerasimov-Drell-Hearn integral was found to be substantial and must be included for an accurate determination of the full integral. Furthermore the data are consistent with a QCD next-to-leading order fit based on previous deep inelastic scattering data. Therefore higher twist effects do not appear significant.Comment: 6 pages, 3 figures, 1 table, revte

ADP is the Dominant Controller of AMPactivated Protein Kinase Activity Dynamics in Skeletal Muscle during Exercise

Exercise training elicits profound metabolic adaptations in skeletal muscle cells. A key molecule in coordinating these adaptations is AMP-activated protein kinase (AMPK), whose activity increases in response to cellular energy demand. AMPK activity dynamics are primarily controlled by the adenine nucleotides ADP and AMP, but how each contributes to its control in skeletal muscle during exercise is unclear. We developed and validated a mathematical model of AMPK signaling dynamics, and then applied global parameter sensitivity analyses with data-informed constraints to predict that AMPK activity dynamics are determined principally by ADP and not AMP. We then used the model to predict the effects of two additional direct-binding activators of AMPK, ZMP and Compound 991, further validating the model and demonstrating its applicability to understanding AMPK pharmacology. The relative effects of direct-binding activators can be understood in terms of four properties, namely their concentrations, binding affinities for AMPK, abilities to enhance AMPK phosphorylation, and the magnitudes of their allosteric activation of AMPK. Despite AMP’s favorable values in three of these four properties, ADP is the dominant controller of AMPK activity dynamics in skeletal muscle during exercise by virtue of its higher concentration compared to that of AMP