Розрахунок магнітної сприятливості виродженого ідеального газу електронів у випадку анізотропної ефективної маси

Dependence of the diamagnetic susceptibility of a degenerate ideal gas of electrons on the orientation of the magnetic field strength vector relative to the crystal axes, which is due to the anisotropy of the effective mass of electrons is considered. The presence of a diamagnetic susceptibility of a degenerate ideal gas of electrons is one of the fundamental results of the application of quantum mechanics and statistical physics to the description of magnetic phenomena. For an ideal gas of electrons in vacuum, the magnetic susceptibility has diamagnetic and paramagnetic components, the origin of which is due to different mechanisms. At low values of the magnetic field strength and high temperatures, their values are proportional to each other. Since the total value of the susceptibility is measured, it is impossible to separate them. Moreover, when measuring the magnetic susceptibility of a crystal, the contribution of conduction electrons cannot be separated from the contributions of the electrons of atoms, unless some features of the behavior of the magnetic susceptibility of conduction electrons are known. In this article, the calculation of the angular dependence of the effective mass of electrons due to the anisotropy is carried out. The angular dependence of the diamagnetic susceptibility is calculated for the practically important case when the distances between the nearest magnetic levels are small compared to the temperature. It is shown that the angular dependence of the diamagnetic susceptibility coincides with the angular dependence of the cyclotron mass squared, which can be determined from independent cyclotron resonance experiments. It is proposed to use the results obtained to separate the diamagnetic susceptibility of conduction electrons from susceptibilities due to other mechanisms. Pages of the article in the issue: 108 - 111 Language of the article: UkrainianРозглянуто вплив анізотропії ефективної маси на компоненти тензора діамагнітної сприятливості виродженого ідеального газу електронів провідності у кристалах. Обраховано залежність цих компонент від орієнтації магнітного поля відносно кристалічних висей. Отримані результати можуть бути використані для відокремлення діамагнітної сприятливості електронів провідності від сприятливостей обумовлених іншими механізмами

Розрахунок кумулянтів і параметрів функції розподілу методом Монте-Карло та із рівняння для неї

Calculations results of the moments, central moments, cumulants and parameters of the distribution function of a beam of ions implanted in a solid body were analyzed. To analyze the differences between the results of modeling this process by the Monte Carlo method, which is widely used for practically important targets, and the results of the solution of the corresponding integrodifferential equations that describe ions distribution analytically, in the simple case of axial symmetry of the ion beam, when all moments of odd order along the transverse Cartesian coordinate is considered equal to zero due to the symmetry of the problem. It is shown that the same moments obtained by the Monte Carlo method is not exactly equal to zero, but slowly decrease with an increase in the number of ions, as predicted by statistics, and then remain approximately constant. Increasing the number of ions for Monte Carlo simulation reduces the statistical component of this error, but does not affect on the component arising from the application of a simplified model of ion-atom collisions. Pages of the article in the issue: 112 - 115 Language of the article: UkrainianПроаналізовано результати розрахунку моментів, центральних моментів, кумулянтів та параметрів функції розподілу пучка іонів імплантованих у тверде тіло. Для аналізу відмінностей між результатами моделювання цього процесу методом Монте-Карло, який широко використовується для практично важливих мішеней, та результатами розв’язку інтегродиференціальних рівнянь, які його описують аналітично, розглянуто випадок осьової симетрії пучка іонів, коли всі моменти непарного порядку по поперечній декартовій координаті рівні нулю в силу симетрії задачі. Показано, що ці ж самі моменти, отримані методом Монте-Карло повільно спадають до нуля із збільшенням кількості іонів, як і передбачається статистикою, і залишаються приблизно сталими

Abrupt changes in alpha decay systematics as a manifestation of collective nuclear modes

An abrupt change in $\alpha$ decay systematics around the N=126 neutron shell closure is discussed. It is explained as a sudden hindrance of the clustering of the nucleons that eventually form the $\alpha$ particle. This is because the clustering induced by the pairing mode acting upon the four nucleons is inhibited if the configuration space does not allow a proper manifestation of the pairing collectivity.Comment: 6 pages, 3 figures, submitted to Phys. Rev. C, a few new references adde

Spin-flip processes and ultrafast magnetization dynamics in Co - unifying the microscopic and macroscopic view of femtosecond magnetism

The femtosecond magnetization dynamics of a thin cobalt film excited with ultrashort laser pulses has been studied using two complementary pump-probe techniques, namely spin-, energy- and time-resolved photoemission and time-resolved magneto-optical Kerr effect. Combining the two methods it is possible to identify the microscopic electron spin-flip mechanisms responsible for the ultrafast macroscopic magnetization dynamics of the cobalt film. In particular, we show that electron-magnon excitation does not affect the overall magnetization even though it is an efficient spin-flip channel on the sub-200 fs timescale. Instead we find experimental evidence for the relevance of Elliott-Yafet type spin-flip processes for the ultrafast demagnetization taking place on a time scale of 300 fs.Comment: 12 pages, 3 figures; accepted by Physical Review Letter

Energy-resolved electron-spin dynamics at surfaces of p-doped GaAs

Electron-spin relaxation at different surfaces of p-doped GaAs is investigated by means of spin, time and energy resolved 2-photon photoemission. These results are contrasted with bulk results obtained by time-resolved Faraday rotation measurements as well as calculations of the Bir-Aronov-Pikus spin-flip mechanism. Due to the reduced hole density in the band bending region at the (100) surface the spin-relaxation time increases over two orders of magnitude towards lower energies. At the flat-band (011) surface a constant spin relaxation time in agreement with our measurements and calculations for bulk GaAs is obtained.Comment: 6 pages, 4 figure

Beta-delayed deuteron emission from 11Li: decay of the halo

The deuteron-emission channel in the beta-decay of the halo-nucleus 11Li was measured at the ISAC facility at TRIUMF by implanting post-accelerated 11Li ions into a segmented silicon detector. The events of interest were identified by correlating the decays of 11Li with those of the daughter nuclei. This method allowed the energy spectrum of the emitted deuterons to be extracted, free from contributions from other channels, and a precise value for the branching ratio B_d = 1.30(13) x 10-4 to be deduced for E(c.m.) > 200 keV. The results provide the first unambiguous experimental evidence that the decay takes place essentially in the halo of 11Li, and that it proceeds mainly to the 9Li + d continuum, opening up a new means to study of the halo wave function of 11Li.Comment: 4 pages, 3 figure

Shapes of the 192,190^{192,190}Pb ground states from beta decay studies using the total absorption technique

The beta decay of $^{192,190}$Pb has been studied using the total absorption technique at the ISOLDE(CERN) facility. The beta-decay strength deduced from the measurements, combined with QRPA theoretical calculations, allow us to infer that the ground states of the $^{192,190}$Pb isotopes are spherical. These results represent the first application of the shape determination method using the total absorption technique for heavy nuclei and in a region where there is considerable interest in nuclear shapes and shape effects

IMMUNOLOGICAL MONITORING OF THE INFLUENZA VIRUS A SUBTYPE H5 AND H7 DISTRIBUTION IN SOUTH OF CENTRAL SIBERIA

For the first time in the south of the Central Siberia carried out large-scale study of wild and synanthropic birds for the presence of influenza A viruses. Along with the traditional methods of laboratory study of pathogens in Merskey's reaction and. PCR carried out ornithological research in areas of high concentrations of birds and. flyways. Also studied the long-term dynamics of isolation of positive samples containing specific antibody to influenza virus A subtypes H5 and. H7 and. genomic RNA of these subtypes. It was found that infection and. reinfection. of birds by avian influenza doesn't take place only during the wintering grounds, but also the breeding season in the water keepings of the south of the Central Siberia. Chicks are actively involved in the epizootic process in July, when transovarialy transmitted maternal antibodies disappear. Because of the peak interval of positive samples selection in Merskey's reaction and. PCR is 3 years, it is possible to organize an immunological monitoring followed by preventive programs development of birds deaths

Hyperbaric oxygen for patients with chronic bowel dysfunction after pelvic radiotherapy (HOT2): a randomised, double-blind, sham-controlled phase 3 trial.

Background Hyperbaric oxygen has been used as a therapy for patients experiencing chronic intestinal syndromes after pelvic radiotherapy for decades, yet the evidence to support the use of this therapy is based almost exclusively on non-randomised studies. We aimed to provide conclusive results for the clinical benefits of hyperbaric oxygen in patients with chronic bowel dysfunction after radiotherapy for pelvic malignancies.Methods HOT2 was a double-blind, sham-controlled, phase 3 randomised study of patients (≥18 years) with chronic gastrointestinal symptoms for 12 months or more after radiotherapy and which persisted despite at least 3 months of optimal medical therapy and no evidence of cancer recurrence. Participants were stratified by participating hyperbaric centre and randomly assigned (2:1) by a computer-generated list (block size nine or 12) to receive treatment with hyperbaric oxygen therapy or sham. Participants in the active treatment group breathed 100% oxygen at 2·4 atmospheres of absolute pressure (ATA) and the control group breathed 21% oxygen at 1·3 ATA; both treatment groups received 90-min air pressure exposures once daily for 5 days per week for a total of 8 weeks (total of 40 exposures). Staff at the participating hyperbaric medicine facilities knew the allocated treatment, but patients, clinicians, nurse practitioners, and other health-care professionals associated with patients' care were masked to treatment allocation. Primary endpoints were changes in the bowel component of the modified Inflammatory Bowel Disease Questionnaire (IBDQ) score and the IBDQ rectal bleeding score 12 months after start of treatment relative to baseline. The primary outcome was analysed in a modified intention-to-treat population, excluding patients who did not provide IBDQ scores within a predetermined time-frame. All patients have completed 12 months of follow-up and the final analysis is complete. The trial is registered with the ISRCTN registry, number ISRCTN86894066.Findings Between Aug 14, 2009, and Oct 23, 2012, 84 participants were randomly assigned: 55 to hyperbaric oxygen and 29 to sham control. 75 (89%) participants received 40 pressure exposures, all participants returned the IBDQ at baseline, 75 (89%) participants returned the IBDQ at 2 weeks post-treatment, and 79 (94%) participants returned the IBDQ at 12 months post-start of treatment. Patients were excluded from analyses of co-primary endpoints if they had missing IBDQ scores for intestinal function or rectal bleeding at baseline or at 12 months. In an analysis of 46 participants in the active treatment group and 23 participants in the control group, we found no significant differences in the change of IBDQ bowel component score (median change from baseline to 12 months of 4 (IQR -3 to 11) in the treatment group vs 4 (-6 to 9) in the sham group; Mann-Whitney U score 0·67, p=0·50). In an analysis of 29 participants in the active treatment group and 11 participants in the sham group with rectal bleeding at baseline, we also found no significant differences in the change of IBDQ rectal bleeding score (median change from baseline to 12 months of 3 [1 to 3] in the treatment group vs 1 [1 to 2] in the sham group; U score 1·69, p=0·092). Common adverse events in both groups were eye refractive changes (three [11%] of 28 patients in the control group vs 16 [30%] of 53 patients in the treatment group), increased fatigue (three [11%] vs two [4%]), and ear pain (six [21%] vs 15 [28%]). Eight serious adverse events were reported in eight patients: two were reported in two patients in the control group (tonsillitis requiring surgery [grade 3]; recurrent cancer of the vulva [grade 4]) and six serious adverse events were reported in six patients in the treatment group (malignant spinal cord compression requiring surgery [grade 3]; malignant paraortic lymph node involvement requiring surgery [grade 3]; recurrence of vomiting and dehydration [grade 3]; diarrhoea and fever associated with Campylobacter infection [grade 3]; recurrence of abdominal pain, bloating, diarrhoea, and urinary tract infection [grade 3]; aneurysm [grade 4]), none of which were deemed treatment-related.Interpretation We found no evidence that patients with radiation-induced chronic gastrointestinal symptoms, including those patients with rectal bleeding, benefit from hyperbaric oxygen therapy. These findings contrast with evidence used to justify current practices, and more level 1 evidence is urgently needed.Funding Cancer Research UK and National Health Service (NHS) funding to the National Institute of Health Research Biomedical Research Centre at The Royal Marsden and the Institute of Cancer Research