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

N-transfer through aspen litter and feather moss layers after fertilization with ammonium nitrate and urea

When fertilizer is broadcast in boreal forest stands, the applied nutrients must pass through a thick layer of either feather moss or leaf litter which covers the forest floor. In a growth chamber experiment we tested the transfer of N through living feather moss or aspen litter when fertilized with urea ((NH2)2CO) or NH4NO3 at a rate of 100 kg ha−1 and under different watering regimes. When these organic substrates were frequently watered to excess they allowed the highest transfer of nutrients through, although 72% of the applied fertilizer was captured in the substrates. In a field experiment we also fertilized moss and aspen litter with urea ((NH2)2CO) or NH4NO3 at a more operationally relevant rate of 330 kg ha−1. We captured the NO3− or NH4+ by ion exchange resin at the substrate–mineral soil interface. In contrast to the growth chamber experiment, this fertilizer rate killed the moss and there was no detectable increase in nutrient levels in the aspen litter or feather moss layers. Instead, the urea was more likely transferred into the mineral soil; mineral soil of the urea treatment had 1.6 times as much extractable N compared to the NH4NO3 treatment. This difference between the growth chamber and field studies was attributed to observed fertilizer- damage to the living moss and possibly damage to the litter microflora due to the higher rate of fertilization in the field. In addition, the early and substantial rainfall after fertilization in the field experiment produced conditions for rapid leaching of N through the organic layers into the mineral soil. In the field, only 8% of the urea-N that was applied was captured by the ion exchange resin, while 34% was captured in for the NH4NO3 fertilization. Thus, the conditions for rapid leaching in the field moved much of the N in the form of urea through the organic layers and into the mineral soil before it was hydrolyzed

About of organization of student science and research works

На примере научной группы профессора Б. В. Шульгина, работающего на кафедре экспериментальной физики, показаны результаты организации НИРС и ВНР студентов в рамках инновационного подхода, осуществляемого путем подключения их к разработке новых объектов интеллектуальной собственности, отвечающих требованиям мировой новизны. В результате такого подхода за последние 40 лет 48 студентов из научной группы профессора Б. В. Шульгина стали соавторами 64 изобретений.The results of student science work organization (including organization of diploma work) on the invention level (creation of new objects of intellectual properties) on the example of science group of professor В. V. Shulgin (experimental physics department) in the frame of innovation way are presented. As a result вгкштп дфые 40 years 48 students from the science group of professor В. V. Shulgin were became co-authors of 64 inventions

Proton polarizability and the Lamb shift in muonic hydrogen

The proton structure and proton polarizability corrections to the Lamb shift of electronic hydrogen and muonic hydrogen were evaluated on the basis of modern experimental data on deep inelastic structure functions. Numerical value of proton polarizability contribution to (2P-2S) Lamb shift is equal to 4.4 GHz.Comment: 8 pages, LaTeX2.09, 2 figures, uses linedraw.st

Dislocation of the penis: a rare case of genital trauma

Traumatic dislocation of the penis is one of the rarest types of genital trauma. This type of injury is accompanied by a violation of the integrity of the skin and the penile ligamentous apparatus, with the dislocation of the penis into the scrotum under the skin of the thigh, or the area of the pubic joint. The low occurrence frequency of such injuries and the small number of observations described in the literature entails the absence of generally accepted treatment tactics for this category of patients. The article describes a clinical case of successfully treated traumatic dislocation of the penis with penile transposition into the pubic joint area and the formation of subcutaneous urinary leakage after late treatment of the patient for medical care

Comparison of quantum mechanical and classical trajectory calculations of cross sections for ion-atom impact ionization of negative - and positive -ions for heavy ion fusion applications

Stripping cross sections in nitrogen have been calculated using the classical trajectory approximation and the Born approximation of quantum mechanics for the outer shell electrons of 3.2GeV I$^{-}$ and Cs$^{+}$ ions. A large difference in cross section, up to a factor of six, calculated in quantum mechanics and classical mechanics, has been obtained. Because at such high velocities the Born approximation is well validated, the classical trajectory approach fails to correctly predict the stripping cross sections at high energies for electron orbitals with low ionization potential.Comment: submitted to Phys. Rev.

Scaling and Formulary cross sections for ion-atom impact ionization

The values of ion-atom ionization cross sections are frequently needed for many applications that utilize the propagation of fast ions through matter. When experimental data and theoretical calculations are not available, approximate formulas are frequently used. This paper briefly summarizes the most important theoretical results and approaches to cross section calculations in order to place the discussion in historical perspective and offer a concise introduction to the topic. Based on experimental data and theoretical predictions, a new fit for ionization cross sections is proposed. The range of validity and accuracy of several frequently used approximations (classical trajectory, the Born approximation, and so forth) are discussed using, as examples, the ionization cross sections of hydrogen and helium atoms by various fully stripped ions.Comment: 46 pages, 8 figure

Фотонные и терагерцовые применения как следующий драйвер рынка арсенида галлия

Analysis of current GaAs and related device market initiated in a number of earlier works has been continued. Binary semiconductor GaAs compound is a conventional MW electronics material. Until recently GaAs based HF ICs for mobile phones were among the most rapidly growing segments of GaAs market. However the GaAs market development trend is changing. Photonics and TeraHertz engineering are becoming the new world GaAs market drivers. This means that the current emphasize of GaAs single crystal technologies will shift toward vertical directional crystallization of “optoelectronic quality” crystals. In the medium and longer terms the world GaAs wafer and epitaxial structure markets will continue growing. In the shorter term we all will have to take into account COVID epidemic consequences. Still the GaAs market is closely related to Smartphone market novelties. Quite probably after a long growth period the GaAs market will keep on shrinking for the second consecutive year: GaAs production may decline by 11–12 % in 2020. Assuming that the epidemic will be somehow taken under control in 2021 the overall Smartphone production can probably be expected to grow starting from 2021.Currently the Russian market of semiconductor compounds for photonics and electronic components (GaAs etc.) is but moderate and in predictable terms is not expected to achieve a level that is required for the emergence of a competitive domestic manufacturer, even though all importation replacement programs are accomplished. Meanwhile there is understanding that developing an advanced electronic components industry in Russia requires larger production of source materials.Продолжен предпринятый ранее в ряде работ анализ современного состояния рынка GaAs и приборов на его основе. Двойное полупроводниковое соединение арсенид галлия (GaAs) — традиционный материал СВЧ-электроники. До недавних пор одним из наиболее быстрорастущих сегментов рынка применений этого материала были высокочастотные интегральные схемы на GaAs для мобильной телефонии. Однако, парадигма развития рынка GaAs меняется. Новым двигателем развития мирового рынка арсенида галлия становится фотоника и терагерцовая техника. Это означает, что в технологиях выращивания монокристаллов GaAs произойдет смена акцентов в сторону кристаллов «оптоэлектронного качества», получаемых методом вертикальной направленной кристаллизации. В средне- и долгосрочной перспективе мировые рынки пластин и эпитаксиальных структур GaAs будут расти. В ближайшей перспективе необходимо учитывать последствия пандемии COVID. Пока рынок GaAs тесно связано с разработками на рынке смартфонов. Очень вероятно, что после длительного периода роста рынок GaAs будет второй год подряд сокращаться — производство GaAs в 2020 году может снизиться на 11—12 %. Если предположить, что пандемия будет как-то взята под контроль в 2021 году, общее производство смартфонов вероятно, вырастет начиная с 2021 г.На данный момент российский рынок полупроводниковых соединений для развития фотоники и электронно-компонентной базы (GaAs и др.) имеет незначительный объем и в ближайшей перспективе не достигнет уровня, необходимого для появления конкурентоспособного отечественного производителя, даже при условии выполнения программ импортозамещения. В то же время, существует понимание, что для создания современной электронной компонентной базы в России необходимо развивать производства исходных материалов

LIS-3 Acute Coronary Syndrome Registry: Changes in Clinical and Demographic Characteristics and Tactics of Prehospital and Hospital Treatment of Surviving Patients After Acute Coronary Syndrome Over a 4-Year Period

Aim. To study the changes in clinical and demographic characteristics, risk factors, treatment tactics, the dynamics of drug therapy at the prehospital stage and prescribed during discharge from the cardiology department over a 4-year period in patients after acute coronary syndrome (ACS) with ST segment elevation and ACS without ST segment elevation. Material and methods. Data from the LIS-3 prospective registry (Lyubertsy mortality study) was used. Patients admitted to the cardiology department of the Lyubertsy district hospital No. 2 for the first 9 months of 2014 (n=104) and for the first 9 months of 2018 (n=223) with a diagnosis of “ACS with ST segment elevation and ACS without ST segment elevation” and with a confirmed diagnosis at discharge “acute myocardial infarction” (AMI) or “unstable angina” (NSA) were included into the study. Comparison of clinical and demographic indicators, risk factors, the frequency of use of acetylsalicylic acid, clopidogrel, statins, beta-blockers, ACE inhibitors, angiotensin II receptor antagonists, anticoagulants at the prehospital stage and during discharge from the hospital were performed. Results. Significant differences in the gender and age composition of patients were not found. The number of working patients increased. Compared to 2014, in 2018 the number of patients with arterial hypertension increased (64.4% and 75.8%, respectively, p=0.047), and with coronary heart disease decreased significantly (39.4% and 22.4%, respectively, p=0.004), however, the incidence of atrial fibrillation, history of AMI, and cerebral stroke did not change over the period under consideration. The frequency of concomitant diseases did not practically change, except for kidney diseases, which have become more common. A significant decrease in the frequency of thrombolysis and a significant (more than 6-fold) increase in angioplasty with stenting were found. Patients before ACS in 2014 received less antiplatelet agents than in 2018, including dual antiplatelet therapy, ACE inhibitors were prescribed more often. The intake of nitrates decreased, and the use of statins increased (6.7% versus 13.9%, respectively, p>0.05). AMI as the outcome of ACS was almost the same in both men and women. A downward trend in myocardial Q-infarction (p>0.05) was found. Taking dual antiplatelet therapy and ACE inhibitors were more often recommended at discharge and taking nitrates and any diuretics was less common. Statins intake did not change. Conclusion. The “portrait” of a hospitalized ACS patient changed somewhat over 4 years: the frequency of the history of coronary heart disease significantly decreased, and the frequency of hypertension increased. The presence and significance of risk factors such as hypercholesterolemia and adverse heredity cannot be assessed as before. The frequency of use of antiplatelet agents and statins increased in prehospital therapy; however, in general, a smaller proportion of patients requiring statins took them. The proportion of AMI patients among ACS ones did not change over the study period