We report experimental upper limits on WIMP-nucleon elastic scattering cross sections from the second science run of ZEPLIN-III at the Boulby Underground Laboratory. A raw fiducial exposure of 1344 ...kg⋅days was accrued over 319 days of continuous operation between June 2010 and May 2011. A total of eight events was observed in the signal acceptance region in the nuclear recoil energy range 7–29 keV, which is compatible with background expectations. This allows the exclusion of the scalar cross-section above 4.8×10−8 pb near 50 GeV/c2 WIMP mass with 90% confidence. Combined with data from the first run, this result improves to 3.9×10−8 pb. The corresponding WIMP-neutron spin-dependent cross-section limit is 8.0×10−3 pb. The ZEPLIN programme reaches thus its conclusion at Boulby, having deployed and exploited successfully three liquid xenon experiments of increasing reach.
Based on the analysis of the magnetic state of austenite, changes in thermodynamics and kinetics of the martensitic transformation in carbon steel have been determined. Depending on the strength of ...the external magnetic field, the dimensions of the magnetic inhomogeneity regions in austenite were calculated. It was shown that with an increase in the field strength, the size and the quantity of such regions increase. Changes in free energy of austenite, caused by the appearance of ferromagnetic order fluctuations, have been determined. The free energy of formation of one ferromagnetic cluster in austenite was estimated. Changes in the energy of formation and diameter of the critical martensite nucleus were analyzed depending on the strength of the external magnetic field. Data about an increase in the volumetric martensite transformation rate under the exposure to a magnetic field were obtained.
We studied the application of statistical reconstruction algorithms, namely maximum likelihood and least squares methods, to the problem of event reconstruction in a dual phase liquid xenon detector. ...An iterative method was developed for in-situ reconstruction of the PMT light response functions from calibration data taken with an uncollimated γ -ray source. Using the techniques described, the performance of the ZEPLIN-III dark matter detector was studied for 122 keV γ-rays. For the inner part of the detector ( R <; 100 mm) , spatial resolutions of 13 mm and 1.6 mm FWHM were measured in the horizontal plane for primary and secondary scintillation, respectively. An energy resolution of 8.1% FWHM was achieved at that energy. The possibility of using this technique for improving performance and reducing cost of scintillation cameras for medical applications is currently under study.
Scintillation and ionisation yields for nuclear recoils in liquid xenon above 10 keVnr (nuclear recoil energy) are deduced from data acquired using broadband Am–Be neutron sources. The nuclear recoil ...data from several exposures to two sources were compared to detailed simulations. Energy-dependent scintillation and ionisation yields giving acceptable fits to the data were derived. Efficiency and resolution effects are treated using a light collection Monte Carlo, measured photomultiplier response profiles and hardware trigger studies. A gradual fall in scintillation yield below ∼40 keVnr is found, together with a rising ionisation yield; both are in agreement with the latest independent measurements. The analysis method is applied to the most recent ZEPLIN-III data, acquired with a significantly upgraded detector and a precision-calibrated Am–Be source, as well as to the earlier data from the first run in 2008. A new method for deriving the recoil scintillation yield, which includes sub-threshold S1 events, is also presented which confirms the main analysis.
We present new experimental constraints on the WIMP-nucleon spin-dependent elastic cross sections using data from the first science run of ZEPLIN-III, a two-phase xenon experiment searching for ...galactic dark matter weakly interacting massive particles based at the Boulby mine. Analysis of approximately 450 kg x days fiducial exposure allow us to place a 90%-confidence upper limit on the pure WIMP-neutron cross section of sigma(n)=1.9x10(-2) pb at 55 GeV/c(2) WIMP mass. Recent calculations of the nuclear spin structure based on the Bonn charge-dependent nucleon-nucleon potential were used for the odd-neutron isotopes 129Xe and 131Xe. These indicate that the sensitivity of xenon targets to the spin-dependent WIMP-proton interaction could be much lower than implied by previous calculations, whereas the WIMP-neutron sensitivity is impaired only by a factor of approximately 2.
A
bstract
We present an experimental study of single electron emission in ZEPLIN-III, a two-phase xenon experiment built to search for dark matter WIMPs, and discuss appli-cations enabled by the ...excellent signal-to-noise ratio achieved in detecting this signature. Firstly, we demonstrate a practical method for precise measurement of the free electron lifetime in liquid xenon during normal operation of these detectors. Then, using a realistic detector response model and backgrounds, we assess the feasibility of deploying such an instrument for measuring coherent neutrino-nucleus elastic scattering using the ionisation channel in the few-electron regime. We conclude that it should be possible to measure this elusive neutrino signature above an ionisation threshold of ~3 electrons both at a stopped pion source and at a nuclear reactor. Detectable signal rates are larger in the reactor case, but the triggered measurement and harder recoil energy spectrum afforded by the accelerator source enable lower overall background and fiducialisation of the active volume.
Biomarkers of anaphylaxis Esakova, N. V.; Lebedenko, A. A.; Pampura, A. N.
Medicinskij vestnik Ûga Rossii,
09/2022, Letnik:
13, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Anaphylaxis is a severe, life-threatening, systemic hypersensitivity reaction that develops rapidly and can lead to death. The diagnosis of anaphylaxis continues to be primarily clinical. Therefore, ...a large number of studies are initiated annually aimed at a deeper study of the mechanisms of the development of this disease and the search for its biomarkers, which could become an important tool to facilitate the verification of diagnosis, prevention and risk assessment of repeated episodes of anaphylaxis, stratification of the severity of its course, the risk of life-threatening episodes of systemic reactions, and be important in the development of new therapeutic strategies. This review provides information on the currently available data on potential biomarkers of anaphylaxis.
A measurement is presented of the neutron production rate in lead by high energy cosmic-ray muons at a depth of 2850m water equivalent (w.e.) and a mean muon energy of 260GeV. The measurement ...exploits the delayed coincidences between muons and the radiative capture of induced neutrons in a highly segmented tonne scale plastic scintillator detector. Detailed Monte Carlo simulations reproduce well the measured capture times and multiplicities and, within the dynamic range of the instrumentation, the spectrum of energy deposits. By comparing measurements with simulations of neutron capture rates a neutron yield in lead of (5.78-0.28+0.21) ×10-3neutrons/muon/(g/cm2) has been obtained. Absolute agreement between simulation and data is of order 25%. Consequences for deep underground rare event searches are discussed.
Purpose: Experimental results and numerical simulations are presented, concerning effects of microwave generation in coaxial transmission lines which are fed with unipolar, high voltage electric ...pulses. The work is aimed at clarifying the relative importance of several mechanisms that could be responsible for the appearance of microwave-frequency oscillations in the course of pulse propagation through the guiding structure. Design/methodology/approach: Dispersive and filtering properties of coaxial waveguides that involve three structural sections are discussed. These latter follow one another along the axis of symmetry. Two identical sections at the input and output are filled with an isotropic liquid dielectric, while the middle part may, in addition, be either partially or fully filled with a non-conductive gyrotropic material. The inserted core represents a set of ferrite rings showing a nonlinear response to the initial high voltage, pulsed excitation. Throughout the series of measurements, the diameters of the inner conductor and of the ferrite core were kept constant. The outer conductor’s diameter was varied to permit analysis of the effect of that size proper and of the degree to which the cross-section is fi lled with ferrite. The gyrotropic properties of the ferrimagnetic material were realized through application of a magnetic bias field from an external coil. The measurements were made for a variety of pulsed voltage magnitudes from the range of hundreds of kilovolts, and magnetic bias fields of tens kiloamperes per meter. Findings: As observed in our experiments, as well as in papers by other writers, a unipolar pulse coming from the radially uniform front-end section, further on gives rise to quasi-monochromatic voltage oscillations. These appear as soon as the pulse has advanced a sufficient distance into the radially nonuniform portion of the guide. The oscillations may consist of a small number of quasi-periods, which suggests a large spectral line width. However, by properly selecting geometric parameters of the wave guiding line and the characteristics of the initial pulsed waveform it proves possible to obtain output frequencies of about units of gigahertz and pulse powers at subgigawatt levels. Conclusions: The frequencies and amplitudes of the appearing oscillations, as well as their spectral widths, are governed by the complex of dispersive and non-linear properties of the guiding structure. The diameters of the inner and outer coaxial conductors in the line, diameter of the ferrimagnetic insert and its intrinsic linear dispersion determine the set of waveguide modes capable of propagating through the line. An oscillating part of the waveform may appear and get separated from the main body of the pulse if it has originated at a higher frequency than the cut-off value for a different mode than the initial TEM. Key words: unipolar pulse, coaxial transmission line, microwave frequency oscillations, dispersion laws, waveguide modes