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156
result(s) for
"Hock, K. M."
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Complementary split-ring resonator-based deflecting structure
2013
We describe full wave simulation results for a compact, novel deflecting structure operating around 2 GHz. The structure consists of a pair of elliptical complementary split-ring resonators (CSRRs) etched into a copper rectangular waveguide along with outer rectangular cavities to maintain the vacuum. Our design utilizes the strong electric fields created by the resonators to impart a transverse deflection to particle bunches traveling through the structure. Simulations suggest a total deflecting voltage of 0.132 MV and a transverse accelerating gradient of 1.55MV/m for only 4.42 kW of applied rf power. We also present, as a design aid, a simplified, approximate analysis of the operating frequency.
Journal Article
Complementary split-ring resonator-coupled traveling wave accelerating structure
2013
In this paper, we present theoretical and simulation-based analyses of a novel, normal-conducting, multiple-cell, traveling wave accelerating structure. Instead of the conventional circular apertures, we utilize asymmetric complementary split-ring resonators to couple pillbox cavities and bring the phase velocity below that of the speed of light in vacuo. We show that this architecture exhibits a low, negative, group velocity and that the 0 through π modes decrease in order of frequency—in contrast to conventional electrically coupled structures in which the 0 mode has the lowest frequency and the π mode the highest. We illustrate the efficacy of the proposed design via electromagnetic and particle simulation results for a four-cell structure operating around 1.9 GHz. Results are given for operation in the π , 2π/3 , and π/3 modes. Our design achieves accelerating gradients of around 3.3MV/m and a cavity voltage of 0.594 MV for an applied rf power of 82 kW (π mode). The accelerating gradients achieved are up to 3.3 times that of a conventional circular aperture-coupled design with the same phase velocity, rf excitation power, operating frequency, mode type, and number of cells.
Journal Article
Reconstruction of lattice parameters and beam momentum distribution from turn-by-turn beam position monitor readings in circular accelerators
2014
In high chromaticity circular accelerators, rapid decoherence of the betatron motion of a particle beam can make the measurement of lattice and bunch values, such as Courant-Snyder parameters and betatron amplitude, difficult. A method for reconstructing the momentum distribution of a beam from beam position measurements is presented. Further analysis of the same beam position monitor data allows estimates to be made of the Courant-Snyder parameters and the amplitude of coherent betatron oscillation of the beam. The methods are tested through application to data taken on the linear nonscaling fixed field alternating gradient accelerator, EMMA.
Journal Article
A review of beam tomography research at Daresbury Laboratory
2013
This is a review on beam tomography research at Daresbury. The research has focussed on development of normalised phase space techniques. It starts with the idea of sampling tomographic projections at equal phase advances and shows that this would give the optimal reconstruction results. This idea has influenced the design, construction and operation of the tomography sections at the Photo Injector Test Facility at Zeuthen (PITZ) and at the Accelerator and Laser in Combined Experiments (ALICE) at Daresbury. The theoretical justification of this idea is later developed through simulations and analysis of the measurements results at ALICE. The mathematical formalism is constructed around the normalised phase space and the idea of equal phase advances become the basis of this. This formalism is applied to a variety of experimental and simulated situations and shown to be useful in improving resolution, increasing reliability and providing diagnostic information. In this review, we also present the simplifying concepts, formalisms and simulation tools that we have developed.
Accelerator system for the PRISM based muon to electron conversion experiment
2013
The next generation of lepton flavor violation experiments need high intensity and high quality muon beams. Production of such beams requires sending a short, high intensity proton pulse to the pion production target, capturing pions and collecting the resulting muons in the large acceptance transport system. The substantial increase of beam quality can be obtained by applying the RF phase rotation on the muon beam in the dedicated FFAG ring, which was proposed for the PRISM project.This allows to reduce the momentum spread of the beam and to purify from the unwanted components like pions or secondary protons. A PRISM Task Force is addressing the accelerator and detector issues that need to be solved in order to realize the PRISM experiment. The parameters of the required proton beam, the principles of the PRISM experiment and the baseline FFAG design are introduced. The spectrum of alternative designs for the PRISM FFAG ring are shown. Progress on ring main systems like injection and RF are presented. The current status of the study and its future directions are discussed.
Design of an Isotropic Microwave Screen from Dipole Arrays using Genetic Algorithm
2005
In this paper, we discuss the design of a multilayered Frequency Selective Surface (FSS) with low transmission coefficient, for two principal polarisations, via application of a genetic algorithm (GA). A very simple two-step approach is considered by first studying the scattering of a single dipole array in dielectric layers, then optimising a multiple FSS screen comprising several such dipole arrays. Numerical results are compared to the experimental data.
Book Chapter
A Randomized Trial of Genotype-Guided Dosing of Warfarin
2013
This trial compared genotype-guided dosing with standard dosing in patients with atrial fibrillation or venous thromboembolism initiating warfarin anticoagulation. Genotype-guided dosing was associated with a higher percentage of time in the therapeutic INR range of 2.0 to 3.0.
Warfarin has proved to be effective in the management of thromboembolic disease
1
but has a narrow therapeutic index, with wide variation among patients in the daily doses required; this variation can lead to either excessive or insufficient anticoagulation.
2
An increase in the international normalized ratio (INR) above the therapeutic range confers a predisposition to bleeding,
3
which is a common cause of hospital admission.
4
Polymorphisms in two genes,
CYP2C9
(involved in the metabolism of the pharmacologically more potent
S
-enantiomer of warfarin) and
VKORC1
(involved in the vitamin K cycle),
5
,
6
together with age and body-surface area, account for about 50% . . .
Journal Article
Host-pathogen genetic interactions underlie tuberculosis susceptibility in genetically diverse mice
by
Baker, Richard E
,
Papavinasasundaram, Kadamba
,
Meade, Rachel K
in
Animal models
,
Animals
,
Chromosomes
2022
The outcome of an encounter with Mycobacterium tuberculosis ( Mtb ) depends on the pathogen’s ability to adapt to the variable immune pressures exerted by the host. Understanding this interplay has proven difficult, largely because experimentally tractable animal models do not recapitulate the heterogeneity of tuberculosis disease. We leveraged the genetically diverse Collaborative Cross (CC) mouse panel in conjunction with a library of Mtb mutants to create a resource for associating bacterial genetic requirements with host genetics and immunity. We report that CC strains vary dramatically in their susceptibility to infection and produce qualitatively distinct immune states. Global analysis of Mtb transposon mutant fitness (TnSeq) across the CC panel revealed that many virulence pathways are only required in specific host microenvironments, identifying a large fraction of the pathogen’s genome that has been maintained to ensure fitness in a diverse population. Both immunological and bacterial traits can be associated with genetic variants distributed across the mouse genome, making the CC a unique population for identifying specific host-pathogen genetic interactions that influence pathogenesis.
Journal Article
Effects of serotonin 2A/1A receptor stimulation on social exclusion processing
by
Seifritz, Erich
,
Scheidegger, Milan
,
Kraehenmann, Rainer
in
Administration, Oral
,
Adult
,
Biological Sciences
2016
Social ties are crucial for physical and mental health. However, psychiatric patients frequently encounter social rejection. Moreover, an increased reactivity to social exclusion influences the development, progression, and treatment of various psychiatric disorders. Nevertheless, the neuromodulatory substrates of rejection experiences are largely unknown. The preferential serotonin (5-HT) 2A/1A receptor agonist, psilocybin (Psi), reduces the processing of negative stimuli, but whether 5-HT2A/1A receptor stimulation modulates the processing of negative social interactions remains unclear. Therefore, this double-blind, randomized, counterbalanced, cross-over study assessed the neural response to social exclusion after the acute administration of Psi (0.215 mg/kg) or placebo (Pla) in 21 healthy volunteers by using functional magnetic resonance imaging (fMRI) and resting-state magnetic resonance spectroscopy (MRS). Participants reported a reduced feeling of social exclusion after Psi vs. Pla administration, and the neural response to social exclusion was decreased in the dorsal anterior cingulate cortex (dACC) and the middle frontal gyrus, key regions for social pain processing. The reduced neural response in the dACC was significantly correlated with Psi-induced changes in self-processing and decreased aspartate (Asp) content. In conclusion, 5-HT2A/1A receptor stimulation with psilocybin seems to reduce social pain processing in association with changes in self-experience. These findings may be relevant to the normalization of negative social interaction processing in psychiatric disorders characterized by increased rejection sensitivity. The current results also emphasize the importance of 5-HT2A/1A receptor subtypes and the Asp system in the control of social functioning, and as prospective targets in the treatment of sociocognitive impairments in psychiatric illnesses.
Journal Article
Bee venom and thymoquinone combination inhibits cancer cells by inducing cell cycle arrest and apoptosis
2025
Natural products have gained significant interest in cancer therapy. Thymoquinone (TQ), a bioactive compound mainly derived from
Nigella sativa
seeds, and bee venom (BV), a complex mixture of bioactive components secreted by honeybees (
Apis mellifera
), are notable examples. This study aimed to evaluate the synergistic anticancer effects of TQ-BV combination on selected cancer cell lines—HeLa, MCF-7, HCT—and normal human skin fibroblasts (HSF). BV was collected using a novel remote-controlled extraction device designed to maintain venom purity by isolating it from environmental contaminants and minimizing light exposure. HPLC was used to quantify the main components of the venom, thereby detecting the sample’s purity. MTT assays assessed cell viability. Apoptotic activity was analyzed through Annexin V-FITC/PI staining. Flow cytometry was used to evaluate the cell cycle distribution, focusing on the Sub-G1, G1, and S phases in HeLa cells. Results from the MTT assay showed that the TQ-BV combination showed markedly increased potency against HeLa cells with an IC
50
value of (1.495 ± 0.198 µg/mL). Combination Index (CI) analysis confirmed a synergistic effect in all cell lines. The apoptosis assay revealed an increase in both early and late apoptotic cells with the combination treatment in HeLa cells, which exhibited a notable rise in late-stage apoptosis, indicating enhanced apoptotic activity. Cell cycle analysis revealed that the combination appeared to induce arrest at the G1 and S phases, which may have contributed to reduced proliferation. Overall, the TQ-BV combination exhibited strong anticancer potential by inducing cell cycle arrest and promoting apoptosis. The high purity of BV, achieved through an optimized extraction method, may have enhanced its efficacy. Further in vivo studies are needed to confirm these findings and explore potential clinical applications.
Journal Article