Secondary electron emission yield in the limit of low electron energy

Secondary electron emission (SEE) from solids plays an important role in many areas of science and technology.1 In recent years, there has been renewed interest in the experimental and theoretical studies of SEE. A recent study proposed that the reflectivity of very low energy electrons from solid surface approaches unity in the limit of zero electron energy2,3,4, If this was indeed the case, this effect would have profound implications on the formation of electron clouds in particle accelerators,2-4 plasma measurements with electrostatic Langmuir probes, and operation of Hall plasma thrusters for spacecraft propulsion5,6. It appears that, the proposed high electron reflectivity at low electron energies contradicts to numerous previous experimental studies of the secondary electron emission7. The goal of this note is to discuss possible causes of these contradictions.Comment: 3 pages, contribution to the Joint INFN-CERN-EuCARD-AccNet Workshop on Electron-Cloud Effects: ECLOUD'12; 5-9 Jun 2012, La Biodola, Isola d'Elba, Ital

Quantum Electronic Transport through a Precessing Spin

The conductance through a local nuclear spin precessing in a magnetic field is studied by using the equations-of-motion approach. The characteristics of the conductance is determined by the tunneling matrix and the position of equilibrium chemical potential. We find that the spin flip coupling between the electrons on the spin site and the leads produces the conductance oscillation. When the spin is precessing in the magnetic field at Larmor frequency ($\omega_{L}$), the conductance develops the oscillation with the frequency of both $\omega_{L}$ and 2$\omega_{L}$ components, the relative spectrum weight of which can be tuned by the chemical potential and the spin flip coupling.Comment: 5 pages, 3 figure

Dependence of nuclear magnetic moments on quark masses and limits on temporal variation of fundamental constants from atomic clock experiments

We calculate the dependence of the nuclear magnetic moments on the quark masses including the spin-spin interaction effects and obtain limits on the variation of the fine structure constant $\alpha$ and $(m_q/\Lambda_{QCD})$ using recent atomic clock experiments examining hyperfine transitions in H, Rb, Cs, Yb$^+$ and Hg$^+$ and the optical transition in H, Hg$^+$ and Yb$^+$

Magnetization and specific heat of TbFe3(BO3)4: Experiment and crystal field calculations

We have studied the thermodynamic properties of single-crystalline TbFe3(BO3)4. Magnetization measurements have been carried out as a function of magnetic field (up to 50 T) and temperature up to 350K with the magnetic field both parallel and perpendicular to the trigonal c-axis of the crystal. The specific heat has been measured in the temperature range 2-300K with a magnetic field up to 9 T applied parallel to the c-axis. The data indicate a structural phase transition at 192 K and antiferromagnetic spin ordering at 40 K. A Schottky anomaly is present in the specific heat data around 20 K, arising due to two low-lying energy levels of the Tb3+ ions being split by f-d coupling. Below TN magnetic fields parallel to the c-axis drive a spin-flop phase transition, which is associated with a large magnetization jump. The highly anisotropic character of the magnetic susceptibility is ascribed mainly to the Ising-like behavior of the Tb3+ ions in the trigonal crystal field. We describe our results in the framework of an unified approach which is based on mean-field approximation and crystal-field calculations.Comment: 10 pages, 10 figures, 20 references, accepted by Phys. Rev.

Results of a clinical trial of the efficacy and safety of vildagliptin and metformin fixed combination in real clinical practice in Russia (MASTER study)

BACKGRAUND: The widespread prevalence of type 2 diabetes mellitus (T2DM), high mortality and disability of such patients are the reason for the constant active search for effective approaches to hypoglycemic therapy. Recent years have been marked by a change in the strategy for treatment initiation of T2DM. In clinical studies, evidence has been obtained about the benefits of prescribing combination therapy from the time of diagnosis. It seems important to study this treatment option also in real clinical practice.AIMS: To evaluate the effectiveness and safety of the initiation with Galvus Met® as compared with any other combination therapy approaches used in everyday clinical practice.MATERIALS AND METHODS: multicenter prospective observational study in 15 regions of Russia lasting 6 months. Patients were included in the study after the endocrinologist made a decision on the appointment of therapy. Of the men and women over 18 years of age with first diagnosed or previously untreated type 2 diabetes and a level of glycated hemoglobin >7.5%, two groups were formed. The first group included patients who received vildagliptin + metformin (Galvus Met®) in a fixed dose of 50/1000 mg, n=729, the second — another double combination (with the exception of insulin and GLP-1), n=669. The primary endpoint was defined as the proportion of patients (%) who achieved the level of HbA1c <7.0% without proven hypoglycemia at the end of the observation. The NHPQ questionnaire was used to assess the frequency of hypoglycemia.RESULTS: 1385 patients completed the study. For the other combination therapy group, metformin and sulfonylurea derivatives were most often selected (66.5%). In the Galvus Met® group, 68.7% of patients achieved an HbA1c level of <7.0% without proven hypoglycemia, which is significantly better compared to the group of other combinations (40.7%, p <0.001). Galvus Met® therapy contributed to a significantly greater decrease in HbA1c levels by the end of the study compared to other combinations (delta HbA1c -1.6 ± 0.8% versus -1.4 ± 0.9%, p <0.001). In the same group, the average level of HbA1c reached 6.7 ± 0.6% by the end of the study versus 7.1 ± 0.8% in the comparison group, p <0.001. In the Galvus Met® group, body weight decreased by 3.2 ± 3.9 kg, and in the comparison group by 1.3 ± 4.8 kg, p <0.001. The frequency of hypoglycemia episodes in the Galvus Met® group by the end of the study was significantly lower than in the comparison group: 0.8 ± 0.7 episodes per person, versus 1.4 ± 0.8, p = 0.037. In the Galvus Met® group, there were significantly fewer adverse events (4.9% versus 17.7%, p <0.001).CONCLUSIONS: In real clinical practice, Galvus Met® starting therapy has shown better efficacy and safety in terms of achieving glycemic control, HbA1c dynamics, effects on body weight, the frequency of hypoglycemic conditions compared with other combined oral hypoglycemic therapy