On X-ray sources based on Cherenkov and quasi-Cherenkov emission mechanisms

A variety of possible schemes of X-ray sources based on Cherenkov like emission mechanisms is considered theoretically. The possibility to increase substantially an angular density of parametric X-ray source under conditions of grazing incidence of emitting relativistic electrons on the reflecting crystallographic plane of a crystalline target is shownye

X-ray Cherenkov radiation under conditions of grazing incidence of relativistic electrons onto a target surface

X-ray Cherenkov radiation in the vicinity of the photoabsorption edge of a target is considered in this workyesBelgorod State Universit

Effect of anomalous photoabsorption on parametric X-ray radiation from relativistic electrons

Parametric X-ray radiation from relativistic electrons moving in a crystal is theoretically investigated in Bragg geometry. It is shown that the effect of anomalous photoabsorption can manifest itself within this geometry of the scattering of the pseudophoton field of a fast particleye

X-ray generation from relativistic electrons passing through thin targets in cyclical accelerators

The characteristics of quasi-monochromatic tunable X-ray sources based on multipasses of electrons through thin targets installed in cyclical accelerators are discussed. An internal bremsstrahlung radiator coupled with a multilayer X-mirror placed outside the accelerator vacuum chamber is used to produce tunable, narrow spectrayesBelgorod State Universit

One-dimensional Model of a Gamma Klystron

A new scheme for amplification of coherent gamma rays is proposed. The key elements are crystalline undulators - single crystals with periodically bent crystallographic planes exposed to a high energy beam of charged particles undergoing channeling inside the crystals. The scheme consists of two such crystals separated by a vacuum gap. The beam passes the crystals successively. The particles perform undulator motion inside the crystals following the periodic shape of the crystallographic planes. Gamma rays passing the crystals parallel to the beam get amplified due to interaction with the particles inside the crystals. The term `gamma klystron' is proposed for the scheme because its operational principles are similar to those of the optical klystron. A more simple one-crystal scheme is considered as well for the sake of comparison. It is shown that the gamma ray amplification in the klystron scheme can be reached at considerably lower particle densities than in the one-crystal scheme, provided that the gap between the crystals is sufficiently large.Comment: RevTeX4, 22 pages, 4 figure

A Proposed Process for Managing the First Amendment Aspects of Campus Hate Speech

For public institutions, attempts to regulate hate speech raise substantial legal issues under the First Amendment of the U.S. Constitution. For private institutions, which may not be bound by the First Amendment, attempts to regulate hate speech raise sensitive policy questions concerning the role of free expression on campus. Numerous articles (many of which are listed in the references below) have undertaken substantive analysis of these constitutional issues and policy questions. In contrast, this article explores a preliminary and overarching concern: the process by which a college or university addresses the problem of hate speech, and in particular the process by which the institution manages the First Amendment aspects of the problem. In other words, this article focuses on the decision-making process rather than on the decisions themselves; it is the journey, not the destination, that is of primary concern

Local Observations of Climate Change and Adaptation Responses: A Case Study in the Mountain Region of Burundi-Rwanda

Mountain regions and their communities are particularly vulnerable to climate change impacts. However, little is known on the impacts observed and adaptation responses used in Burundi’s mountain region and if these are different to those reported in the contiguous mountain region of Rwanda. This paper aims to fill in these knowledge gaps. Semi-structured interviews were conducted with 300 smallholder farmers, 150 in northern Burundi and 150 in southern Rwanda. Farmers in both countries reported negative impacts on crops, animals, and human health, with small differences between countries driven by the main cultivated crops. More adaptation strategies were used in Burundi than in Rwanda, and more farmers in Burundi were using multiple strategies. In both countries, farmers’ wealth affected farmers’ adaptation responses and their food security. Notably, for all wealth groups (poor, average, rich), food security was lower in Rwanda than in Burundi. We relate our findings to current agricultural intensification policies in both countries and argue for the greater involvement of local farmers in adaptation planning using, for example, science-with-society approaches.We are deeply grateful to our study participants, who graciously shared their time, energy, and stories. We thank our field assistants and facilitators for making this research possible. We also acknowledge the Mountain Research Initiative for funding support

New aspects in the study of clinical and morphological features of uterine blood flow in type 1 diabetes mellitus in the mother

The aim of the study was to develop new approaches to the study of modern aspects of the clinical and morphological features of uterine blood flow in type I diabetes mellitus in the mothe