About The Influence of Chromium on the Damping Capacity of Mn – 40 % Cu Alloy in the Field of Small Oscillation Amplitudes

В статье представлены результаты исследования действия хрома на демпфирующую способность марганцево-медных сплавов в области малых амплитуд колебаний. Сплавы высокого демпфирования на основе Mn – Cu можно эффективно применять для уменьшения вибрации и шума. Однако высокая демпфирующая способность этих сплавов со временем снижается. Исследований, определяющих влияние различных легирующих элементов на величину и стабильность демпфирующей способности двойных сплавов Mn – Cu в области малых амплитуд колебаний, недостаточно. В настоящей работе выяснили действие хрома в концентрациях (0,6 … 1,2) % на демпфирующую способность сплава Mn – 40 % Cu в области малых амплитуд колебаний. Марганцево-медные сплавы выплавляли в индукционной печи с последующим литьём в чугунные изложницы. Из полученных слитков механической обработкой резанием изготавливали образцы для исследований размерами (11 × 15 × 117) ± 1 мм. В ходе эксперимента исследуемые образцы подвергали старению при температуре 643 К в течение (0,5 … 40) часов. Анализировали изменение демпфирующей способности марганцево-медных сплавов (логарифмический декремент затухания колебаний) при продольных колебаниях образцов в диапазоне частот (14 … 17) кГц и амплитудах относительного сдвига (1 … 3) ∙ 10–6. Полученные данные свидетельствуют о том, что легирование сплава Mn – 40 % Cu хромом от 0,6 % до 1,2 % не повышает его демпфирующую способность в литом состоянии, а также в литом и состаренном при температуре 643 К в течение 40 часов состоянии. Установлено, что минимальные значения частот резонансных колебаний образцов марганцево-медных сплавов предшествуют максимальным уровням демпфирующей способности этих сплавов. Выявлено, что высокая демпфирующая способность литых и состаренных при 643 К в течение 40 часов сплавов Mn – 40 % Cu, Mn – (38,8 … 39,4) % Cu – (0,6 … 1,2) % Сr после естественного старения при 293 К в течение 7 месяцев снижается в (1,6 … 1,9) разаThe results of a study of the influence of chromium on the damping capacity of manganese-copper alloys in the field of small oscillation amplitudes are presented in the article. High damping alloys based on Mn – Cu can be effectively used to reduce vibration and noise. However, the high damping capacity of these alloys decreases over time. Studies that determine the influence of various alloying elements on the magnitude and stability of the damping capacity of Mn – Cu double alloys in the field of small oscillation amplitudes are not enough. In the work the effect of chromium in concentrations (0.6 … 1.2) % on the damping capacity of the Mn – 40 % Cu alloy in the field of small oscillation amplitudes was elucidated. Manganese-copper alloys were smelted in an induction furnace followed by casting into cast-iron molds. From the melted ingots samples for studies with dimensions (11 × 15 × 117) ± 1 mm were obtained by mechanical cutting. During the experiment, the studied samples were subjected to aging at a temperature of 643 K for (0,5 … 40) hours. The change in the damping capacity of manganese-copper alloys (the logarithmic decrement of attenuation of oscillations) was analyzed for longitudinal oscillations of the samples in the frequency range (14 … 17) kHz and the amplitudes of the relative shift (1 … 3) × 10–6. The data obtained indicate that alloying the Mn – 40 % Cu alloy with chromium from 0,6 % to 1,2 % does not increase its damping capacity in the cast state, as well as in the cast and aged at a temperature of 643 K for 40 hours. It was found that the minimum values of the frequencies of resonant vibrations of samples of manganese-copper alloys precede the maximum levels of the damping capacity of these alloys. It’s revealed that the high damping capacity of cast and aged at 643 K for 40 hours alloys Mn – 40 % Cu, Mn – (38,8 … 39,4) % Cu – (0,6 … 1,2) % Cr after natural aging at 293 K for 7 months decreases by (1,6 … 1,9) time

Refractive index tomography of turbid media by bifocal optical coherence refractometry

We demonstrate tomographic imaging of the refractive index of turbid media using bifocal optical coherence refractometry (BOCR). The technique, which is a variant of optical coherence tomography, is based on the measurement of the optical pathlength difference between two foci simultaneously present in a medium of interest. We describe a new method to axially shift the bifocal optical pathlength that avoids the need to physically relocate the objective lens or the sample during an axial scan, and present an experimental realization based on an adaptive liquid-crystal lens. We present experimental results, including video clips, which demonstrate refractive index tomography of a range of turbid liquid phantoms, as well as of human skin in vivo.<br /

Magnetic Studies of Iron-Doped Probable Weyl Semimetal WTe2

The non-trivial topology of electronic bands in Weyl semimetals originates from band inversion due to strong spin&ndash;orbit coupling. The Weyl semimetals have pairs of Weyl gap-less nodes in the bulk Brillouin zone. The tungsten ditelluride WTe2 likely belongs to type II Weyl semimetals. Doping WTe2 with magnetic ions could induce magnetic ordering in this crystal, which provides prospects for practical applications. We studied the magnetic properties of the iron-doped single crystals Fe0.03W0.97Te2, annealed and unannealed, in comparison with the undoped WTe2. Measurements of the dc magnetization were carried out from 1.8 to 400 K. We revealed pronounced ferromagnetic ordering that was affected by annealing. Anomalies associated with antiferromagnetism and paramagnetism were also found. The magnetic order was suppressed by a field of 60 kOe. The rise in susceptibility with increasing temperature was observed at high temperatures in all samples and was treated using a model developed for Weyl semimetals. The Curie&ndash;Weiss law fit at 60 kOe showed that the effective magnetic moment was close to that of Fe2+. Metamagnetism was demonstrated for the unannealed doped WTe2 crystal. The data for the heat capacity of the iron-doped sample agreed with results for the undoped WTe2

Statistical analysis of the dynamics of antibody loss to a disease-causing agent: plague in natural populations of great gerbils as an example

We propose a new stochastic framework for analysing the dynamics of the immunity response of wildlife hosts against a disease-causing agent. Our study is motivated by the need to analyse the monitoring time-series data covering the period from 1975 to 1995 on bacteriological and serological tests—samples from great gerbils being the main host of Yersinia pestis in Kazakhstan. Based on a four-state continuous-time Markov chain, we derive a generalized nonlinear mixed-effect model for analysing the serological test data. The immune response of a host involves the production of antibodies in response to an antigen. Our analysis shows that great gerbils recovered from a plague infection are more likely to keep their antibodies to plague and survive throughout the summer-to-winter season than throughout the winter-to-summer season. Provided the seasonal mortality rates are similar (which seems to be the case based on a mortality analysis with abundance data), our finding indicates that the immune function of the sampled great gerbils is seasonal

Multi-strange baryon production in pp collisions at √s=7 TeV with ALICE

A measurement of the multi-strange Ξ− and Ω− baryons and their antiparticles by the ALICE experiment at the CERN Large Hadron Collider (LHC) is presented for inelastic proton–proton collisions at a centre-of-mass energy of 7 TeV. The transverse momentum (pT) distributions were studied at mid-rapidity (|y|6.0 GeV/c. We also illustrate the difference between the experimental data and model by comparing the corresponding ratios of (Ω−+Ω¯+)/(Ξ−+Ξ¯+) as a function of transverse mass

Ds+ meson production at central rapidity in proton–proton collisions at √s=7 TeV

The pT-differential inclusive production cross section of the prompt charm-strange meson Ds+ in the rapidity range |y|<0.5 was measured in proton–proton collisions at s=7 TeV at the LHC using the ALICE detector. The analysis was performed on a data sample of 2.98×108 events collected with a minimum-bias trigger. The corresponding integrated luminosity is Lint=4.8 nb−1. Reconstructing the decay Ds+→ϕπ+, with ϕ→K−K+, and its charge conjugate, about 480 Ds± mesons were counted, after selection cuts, in the transverse momentum range 2<pT<12 GeV/c. The results are compared with predictions from models based on perturbative QCD. The ratios of the cross sections of four D meson species (namely D0, D+, D⁎+ and Ds+) were determined both as a function of pT and integrated over pT after extrapolating to full pT range, together with the strangeness suppression factor in charm fragmentation. The obtained values are found to be compatible within uncertainties with those measured by other experiments in e+e−, ep and pp interactions at various centre-of-mass energies