Experimental and numerical investigation of the reflection coefficient and the distributions of Wigner's reaction matrix for irregular graphs with absorption

We present the results of experimental and numerical study of the distribution of the reflection coefficient P(R) and the distributions of the imaginary P(v) and the real P(u) parts of the Wigner's reaction K matrix for irregular fully connected hexagon networks (graphs) in the presence of strong absorption. In the experiment we used microwave networks, which were built of coaxial cables and attenuators connected by joints. In the numerical calculations experimental networks were described by quantum fully connected hexagon graphs. The presence of absorption introduced by attenuators was modelled by optical potentials. The distribution of the reflection coefficient P(R) and the distributions of the reaction K matrix were obtained from the measurements and numerical calculations of the scattering matrix S of the networks and graphs, respectively. We show that the experimental and numerical results are in good agreement with the exact analytic ones obtained within the framework of random matrix theory (RMT).Comment: 15 pages, 8 figure

ТЕОРЕТИКО-МЕТОДИЧНІ ПІДХОДИ ДО УДОСКОНАЛЕННЯ СИСТЕМИ УПРАВЛІННЯ СПОРТИВНОЮ ДІЯЛЬНІСТЮ В УМОВАХ РИНКУ

The purpose of this work is to substantiate methodological approaches and principles for the formation of an effective system of sports activities management in Ukraine and to identify the ways to improve it. Research methods: theoretical analysis and generalization of literary sources; general scientific methods of research; systematic, structural-functional and process methods, comparative and situational approaches. The results. The prerequisites for improving the system of sport activity management in Ukraine were identified and substantiated as a result of the research. It found that today the most effective methods of improving the structure of management are methods based on structural, functional and process approaches. Organizational and economic approaches to the management, and the principles of managing sport and sports organizations were proposed and improved. Scientific novelty. The organizational and economic and scientific approaches to the differentiation of the concepts of sports management and management of sports organizations, principles of building and functioning of the management system, understanding of the functions of managing sports activities in Ukraine have been further developed and further developed. The practical significance. The results of the study can be used by government agencies and sports organizations.Мета статті полягає в обґрунтуванні методичних підходів, функцій і принципів для формування ефективної системи управління спортивною діяльністю в Україні та визначенні перспективних шляхів її удосконалення. Методи дослідження: теоретичний аналіз і узагальнення літературних джерел; загальнонаукові методи дослідження; системний, структурно-функціональний, процесний, порівняльний та ситуаційний підходи. Результати. В результаті дослідження виявлено та обґрунтовано передумови удосконалення системи управління спортивною діяльністю в Україні. Встановлено, що на сьогодні найбільш дієвими методами удосконалення структури управління є методи, що базуються на структурно-функціональному та процесному підходах. Запропоновано та удосконалено організаційно-економічні підходи до управління, та принципи управління спортом і спортивними організаціями. Наукова новизна. Удосконалено та набули подальшого розвитку організаційно-економічні та наукові підходи щодо розмежування понять управління спортом та управління спортивними організаціями, принципи побудови та функціонування системи управління, розуміння функцій управління спортивною діяльністю в Україні. Практичне значення. Результати дослідження можуть бути використані установами державного управління та спортивними організаціями

Вплив пандемії Covid-19 на показники робочого часу та доходів працівників

Розглянуто вплив пандемії COVID-19 на міжнародний ринок праці в аспекті аналізу показників робочого часу та доходів працівників

Chaotic scattering with direct processes: A generalization of Poisson's kernel for non-unitary scattering matrices

The problem of chaotic scattering in presence of direct processes or prompt responses is mapped via a transformation to the case of scattering in absence of such processes for non-unitary scattering matrices, \tilde S. In the absence of prompt responses, \tilde S is uniformly distributed according to its invariant measure in the space of \tilde S matrices with zero average, < \tilde S > =0. In the presence of direct processes, the distribution of \tilde S is non-uniform and it is characterized by the average (\neq 0). In contrast to the case of unitary matrices S, where the invariant measures of S for chaotic scattering with and without direct processes are related through the well known Poisson kernel, here we show that for non-unitary scattering matrices the invariant measures are related by the Poisson kernel squared. Our results are relevant to situations where flux conservation is not satisfied. For example, transport experiments in chaotic systems, where gains or losses are present, like microwave chaotic cavities or graphs, and acoustic or elastic resonators.Comment: Added two appendices and references. Corrected typo

Classical wave experiments on chaotic scattering

We review recent research on the transport properties of classical waves through chaotic systems with special emphasis on microwaves and sound waves. Inasmuch as these experiments use antennas or transducers to couple waves into or out of the systems, scattering theory has to be applied for a quantitative interpretation of the measurements. Most experiments concentrate on tests of predictions from random matrix theory and the random plane wave approximation. In all studied examples a quantitative agreement between experiment and theory is achieved. To this end it is necessary, however, to take absorption and imperfect coupling into account, concepts that were ignored in most previous theoretical investigations. Classical phase space signatures of scattering are being examined in a small number of experiments.Comment: 33 pages, 13 figures; invited review for the Special Issue of J. Phys. A: Math. Gen. on "Trends in Quantum Chaotic Scattering

Fibromuscular dysplasia presenting as a renal infarction: a case report

<p>Abstract</p> <p>Introduction</p> <p>Fibromuscular dysplasia is a non-atherosclerotic, non-inflammatory disease that most commonly affects the renal and internal carotid arteries.</p> <p>Case presentation</p> <p>We present the case of a 44-year-old Caucasian man who was admitted with complaints of loin pain and hypertension. A computed tomography scan of the abdomen revealed a right renal infarction with a nodular aspect of the right renal artery. Subsequent renal angiography revealed a typical 'string of beads' pattern of the right renal artery with thrombus formation. Oral anticoagulation was started and the secondary hypertension was easily controlled with anti-hypertensive drugs. At follow-up, our patient refused percutaneous transluminal renal angioplasty as a definitive treatment.</p> <p>Conclusions</p> <p>Fibromuscular dysplasia is the most common cause of renovascular hypertension in patients under 50 years of age. Presentation with renal infarction is rare.</p> <p>In fibromuscular dysplasia, angioplasty has been proven to have, at least for some indications, an advantage over anti-hypertensive drugs. Therefore, hypertension secondary to fibromuscular dysplasia is the most common cause of curable hypertension.</p