661 research outputs found

    Next to leading order eta production at hadron colliders

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    Inclusive eta production at hadron colliders is considered,based on evaluation of eta fragmentation functions at next to leading order. Absolute predictions at LHC and SSC are presented, including the ratio η/π0\eta/\pi^0, together with the estimate of the theoretical uncertainty, as a possible neutral background to the HγγH\to \gamma\gamma detection.Comment: 8 pages, latex, FNT/T-93/13,14 figures avilable upon reques

    DTUJET--93 Sampling inelastic proton--proton and antiproton--proton collisions according to the two--component Dual Parton Model

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    A new version of a Monte Carlo Program for hadronic multi-particle production is presented. It is based on the two-component Dual Parton Model which includes the dual topological unitarization of soft and hard cross sections. The model treats both soft (low pp_{\perp}) and hard (minijet, large pp_{\perp}) processes in a unified and consistent way. The unified description is important at TeV-energies of hadron colliders, where the hard perturbative cross sections of QCD become large and comparable to the total cross sections.Comment: 20 pages , PHYSZZX, SI-93-

    The Design and Application of Target-Focused Compound Libraries

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    Target-focused compound libraries are collections of compounds which are designed to interact with an individual protein target or, frequently, a family of related targets (such as kinases, voltage-gated ion channels, serine/cysteine proteases). They are used for screening against therapeutic targets in order to find hit compounds that might be further developed into drugs. The design of such libraries generally utilizes structural information about the target or family of interest. In the absence of such structural information, a chemogenomic model that incorporates sequence and mutagenesis data to predict the properties of the binding site can be employed. A third option, usually pursued when no structural data are available, utilizes knowledge of the ligands of the target from which focused libraries can be developed via scaffold hopping. Consequently, the methods used for the design of target-focused libraries vary according to the quantity and quality of structural or ligand data that is available for each target family. This article describes examples of each of these design approaches and illustrates them with case studies, which highlight some of the issues and successes observed when screening target-focused libraries

    Sitting too much: a hierarchy of socio-demographic correlates

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    Too much sitting (extended sedentary time) is recognized as a public health concern in Europe and beyond. Time spent sedentary is influenced and conditioned by clusters of individual-level and contextual (upstream) factors. Identifying population subgroups that sit too much could help to develop targeted interventions to reduce sedentary time. We explored the relative importance of socio-demographic correlates of sedentary time in adults across Europe. We used data from 26,617 adults who participated in the 2013 Special Eurobarometer 412 "Sport and physical activity". Participants from all 28 EU Member States were randomly selected and interviewed face-to-face. Self-reported sedentary time was dichotomized into sitting less or >7.5h/day. A Chi-squared Automatic Interaction Detection (CHAID) algorithm was used to create a tree that hierarchically partitions the data on the basis of the independent variables (i.e., socio-demographic factors) into homogeneous (sub)groups with regard to sedentary time. This allows for the tentative identification of population segments at risk for unhealthy sedentary behaviour. Overall, 18.5% of the respondents reported sitting >7.5h/day. Occupation was the primary discriminator. The subgroup most likely to engage in extensive sitting were higher educated, had white-collar jobs, reported no difficulties with paying bills, and used the internet frequently. Clear socio-demographic profiles were identified for adults across Europe who engage in extended sedentary time. Furthermore, physically active participants were consistently less likely to engage in longer daily sitting times. In general, those with more indicators of higher wealth were more likely to spend more time sitting

    Nab: Measurement Principles, Apparatus and Uncertainties

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    The Nab collaboration will perform a precise measurement of 'a', the electron-neutrino correlation parameter, and 'b', the Fierz interference term in neutron beta decay, in the Fundamental Neutron Physics Beamline at the SNS, using a novel electric/magnetic field spectrometer and detector design. The experiment is aiming at the 10^{-3} accuracy level in (Delta a)/a, and will provide an independent measurement of lambda = G_A/G_V, the ratio of axial-vector to vector coupling constants of the nucleon. Nab also plans to perform the first ever measurement of 'b' in neutron decay, which will provide an independent limit on the tensor weak coupling.Comment: 12 pages, 6 figures, 1 table, talk presented at the International Workshop on Particle Physics with Slow Neutrons, Grenoble, 29-31 May 2008; to appear in Nucl. Instrum. Meth. in Physics Research

    Parasternal versus apical view in cardiac natural mechanical wave speed measurements

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    Shear wave speed measurements can potentially be used to noninvasively measure myocardial stiffness to assess the myocardial function. Several studies showed the feasibility of tracking naturalmechanical waves induced by aortic valve closure in the interventricular septum, but different echocardiographic views have been used. This article systematically studied the wave propagation speedsmeasured in a parasternal long-axis and in an apical four-chamber view in ten healthy volunteers. The apical and parasternal views are predominantly sensitive to longitudinal or transversal tissue motion, respectively, and could, therefore, theoreticallymeasure the speed of different wave modes. We found higher propagation speeds in apical than in the parasternal view (median of 5.1 m/s versus 3.8 m/s, p < 0.01, n = 9). The results in the different views were not correlated (r = 0.26, p = 0.49) and an unexpectedly large variability among healthy volunteers was found in apical view compared with the parasternal view (3.5-8.7 versus 3.2-4.3 m/s, respectively). Complementary finite element simulations of Lamb waves in an elastic plate showed that different propagation speeds can be measured for different particlemotion componentswhen differentwavemodes are induced simultaneously. The in vivo results cannot be fully explained with the theory of Lamb wave modes. Nonetheless, the results suggest that the parasternal long-axis view is amore suitable candidate for clinical diagnosis due to the lower variability in wave speeds

    Capacitance spectroscopy of InAs self-assembled quantum dots

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    Capacitance spectroscopy is used to study electronic properties of self-assembled InAs quantum dots. The capacitance-voltage, C(V), measurements in combination with the magneto-capacitance, C(B), results make it possible to investigate the electrostatic profile of a series of single-barrier n-i-n GaAs/AlAs/GaAs heterostructures incorporating a layer of self-assembled InAs quantum dots in the AlAs barrier. We find that the negative charge associated with electron filling of the dots is closely compensated by a positive charge in the AlAs barrier, which we ascribe to ionised defects or impurities, possibly in association with the quantum dots. It is shown the compensation degree considerably depends on the growth conditions.Ємнiсна спектроскопiя використується для дослiдження електронних властивостей само-органiзованих InAs квантових точок. Вимiрювання вольт-фарадних характеристик, C(V), одночасно з даними по магнето-емностi, C(B), дозволяють дослiджувати електростатичний профiль однобар.єрних p-i-n GaAs/AlAs/GaAs гетероструктур, якi мiстять в AlAs бар.єрі шар само-органiзованих InAs квантових точок. Ми визначили, що негативний заряд, пов.язаний з заповненням квантових точок електронами, майже повнiстю компенсується позитивним зарядом в AlAs бар.єрi, що, на нашу думку, пов.язано з iонiзованими дефектами чи домiшками, якi обумовлені квантовими точками. Показано, що мiра компенсацiї суттєво залежить вiд ростових умов.Емкостная спектроскопия используется для исследования электронных свойств само-организованных InAs квантовых точек. Измерение вольт-фарадных характеристик, C(V), совместно с данными по магнето-емкости, C(B), позволяют исследовать электростатический профиль однобарьерных p-i-n GaAs/AlAs/GaAs гетероструктур, содержащих в AlAs барьере слой само-организованных InAs квантовых точек. Мы установили, что отрицательный заряд, связанный с заполнением квантовых точек электронами, почти полностью компенсируется положительным зарядом в AlAs барьере, который, по нашему мнению, связан с ионизованными дефектами или примесями, обусловленными квантовыми точками. Показано, что степень компенсации существенно зависит от ростовых условий

    Chemical dissociation of human awareness: focus on non-competitive NMDA receptor antagonists

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    Since the mid-1950s the pharmaceutical industry has developed a number of chemicals, including phencyclidine, ketamine and related arylcyclohexylamines (PCE and TCP), dizocilpine (MK-801), N-allylnormetazocine [ NANM, (±)SKF-10,047], etoxadrol, dioxadrol and its enantiomers dexoxadrol and levoxadrol, which produce a constellation of unusual behavioral effects in animals and man. The compounds best studied in humans are phencyclidine and ketamine. They produce a remarkable dose-dependent dissociation of awareness. All of these substances are now known to be non-competitive antagonists of NMDA receptors of glutamic acid. They act in the NMDA receptor ion channel. One can conclude, on the basis of the effects observed with these agents, that glutamic acid and related excitatory amino acids are extremely important in the maintenance of human awareness.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68872/2/10.1177_026988119200600312.pd

    High-Frame-Rate Volumetric Porcine Renal Vasculature Imaging

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    Objective:The aim of this study was to assess the feasibility and imaging options of contrast-enhanced volumetric ultrasound kidney vasculature imaging in a porcine model using a prototype sparse spiral array. Methods: Transcutaneous freehand in vivo imaging of two healthy porcine kidneys was performed according to three protocols with different microbubble concentrations and transmission sequences. Combining high-frame-rate transmission sequences with our previously described spatial coherence beamformer, we determined the ability to produce detailed volumetric images of the vasculature. We also determined power, color and spectral Doppler, as well as super-resolved microvasculature in a volume. The results were compared against a clinical 2-D ultrasound machine. Results: Three-dimensional visualization of the kidney vasculature structure and blood flow was possible with our method. Good structural agreement was found between the visualized vasculature structure and the 2-D reference. Microvasculature patterns in the kidney cortex were visible with super-resolution processing. Blood flow velocity estimations were within a physiological range and pattern, also in agreement with the 2-D reference results. Conclusion:Volumetric imaging of the kidney vasculature was possible using a prototype sparse spiral array. Reliable structural and temporal information could be extracted from these imaging results.</p
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