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Search Results: 1 - 10 of 190034 matches for " Demosthenes G. Katritsis "
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Arrhythmogenicity of the Coronary Sinus
Demosthenes G. Katritsis
Indian Pacing and Electrophysiology Journal , 2004,
Abstract: The coronary sinus (CS) is the cardiac venous system that begins at its ostium in the right atrium and ends at the origin of the great cardiac vein. The major tributaries of the CS include the great cardiac vein (anterior cardiac vein), the left obtuse marginal vein, the posterior (or inferior) left ventricular vein, the middle cardiac vein, and the right coronary vein. In addition, atrial veins and, notably, the vein of Marshall (or oblique left atrial vein) also enter the coronary sinus. From the perspective of electrophysiologists, the CS represents an anatomical structure of particular interest. First, it provides access to epicardial atrioventricular pathways and arrhythmogenic foci of both atrial6 and ventricular arrhythmia. Second, it represents by itself a potential source of atrial arrhythmia. The arrhythmogenic potential of the thoracic veins in general has been recognised since the 1970s. Atrial arrhythmias can originate in the pulmonary veins, the superior vena cava, and the CS. Indeed, biatrial flutter,left atrial tachycardia, and atrial fibrillation, involving the distal CS have been well described. There is now evidence that the CS apart from participating in arrhythmia circuits, such as in the slow-slow form of atrioventricular nodal reentrant tachycardia and atrioventricular reentrant tachycardia due to accessory pathways,may itself be a source of apparently atrial arrhythmia. In patients with paroxysmal atrial fibrillation apparently originating from the left superior or inferior pulmonary vein, detailed epicardial mapping through the distal coronary sinus might identify epicardial location of the arrhythmogenic focus. Therefore, the search for foci of abnormal automaticity within the CS should be part of the electrophysiologic evaluation of left atrial arrhythmias.
Specifying the Global Execution Context of Computer-Mediated Tasks: A Visual Notation and a Supporting Tool  [PDF]
Demosthenes Akoumianakis
Journal of Software Engineering and Applications (JSEA) , 2010, DOI: 10.4236/jsea.2010.34037
Abstract: This paper presents the notion of the global execution context of a task as a representational construct for analysing complexity in software evolution. Based on this notion a visual notation and a supporting tool are presented to support specification of a system’s global execution context. A system’s global execution context is conceived as an evolving network of use scenarios depicted by nodes and links designating semantic relationships between scenarios. A node represents either a base or a growth scenario. Directed links characterize the transition from one node to another by means of semantic scenario relationships. Each growth scenario is generated following a critique (or screening) of one or more base or reference scenarios. Subsequently, representative growth scenarios are compiled and consolidated in the global execution context graph. The paper describes the stages of this process, presents the tool designed to facilitate the construction of the global execution context graph and elaborates on recent practice and experience.
Genetic Implications in COPD. The Current Knowledge  [PDF]
Ioannis Sotiriou, Demosthenes Makris
Open Journal of Respiratory Diseases (OJRD) , 2013, DOI: 10.4236/ojrd.2013.32009
Abstract: Chronic Obstructive Pulmonary Disease (COPD) is a multifactorial disease in the pathogenesis of which contributes a variety of causative factors including genetic and environmental ones. They may also be interactions of genetic susceptibilities and environmental influences. Towards to that in the pathogenesis of the disease except smoking, it seems to have a great impact the genetic predisposition of the individuals suffering from that serious progressive disease. Regarding to these observations and findings very interesting studies have been conducted in order to elucidate the implications of different genes, and their polymorphisms in disease aetiology. This is a review which elucidates the impact of genetic susceptibility in COPD.
Morphometry of corpus callosum: an anatomical study
Anagnostopoulou S,Mourgela S,Katritsis D
Neuroanatomy , 2006,
Abstract: The purpose of this study was to measure the longitudinal and vertical diameters of corpus callosum and itsparts as well as the brain; in order to define the position of corpus callosum within the brain. In this study, 42 formalin fixed brains, which were removed from cadavers (23 males, 19 females), aged 30-40years, were used. Brains were carefully cut in the mediosagittal plane and the medial surface of the brainhemispheres were printed on a transparent sheet of paper. On these papers, the longitudinal diameters ofevery anatomical part of corpus callosum and longitudinal and vertical diameters of brain hemispheres weremeasured. The diameters measured were: the longitudinal (frontal to occipital pole-AB) and the vertical diameter (upperto lower surface of brain hemisphere-CD) of brain hemispheres, the distance of genu to frontal pole (AE), thedistance of splenium to occipital pole (ZB), the longitudinal diameter of genu (EZ/3) and splenium (EZ/5), andthe longitudinal diameter of CC (EZ). Statistical analysis followed, which was performed by using the 2-tailedPearson correlation test. AB has a positive linear correlation with CD, AE, BZ and with EZ. EZ has a positivelinear correlation with AB and with CD. The ratios EZ/AB=0.46, EZ/CD=0.85, EZ/AE=2.29 and EZ/ZB=1.42represented stable analogies. By applying these ratios to radiological images of patients, the neurosurgeons would perform the targetedcallosal procedures in a more precise way.
Strategic Sourcing: A Comparative Study across Two Industries
Burhan F. Yavas,G Keong Leong,Demosthenes Vardiabasis,Natasa Christodoulidou
International Journal of Business and Management , 2011, DOI: 10.5539/ijbm.v6n4p3
Abstract: The purpose of the present investigation is to examine the perceptions of managerial practices regarding issues surrounding strategic sourcing (SS) across different industries. The two industries examined in this study are the manufacturing and the service industries. Although arguably these industries are different in terms of industry practices and culture there has been a trend toward convergence of managerial practices. Major items such as VMI, education, risk assessment, and social responsibility appear to have the same importance in both the manufacturing and service industry. The findings also indicate some support for the divergence view. Issues such as diversity, collaboration in reducing costs, and communication with upper management, exhibit some differences in opinion among manufacturing executives and service oriented executives. These differences may be attributed to the services industry still being in its infancy stage in the sourcing arena. This can have implications for both industries as they are becoming more hybrid in nature and at times becomes challenging to distinguish between a good or a service.
The Duration -- Photon Energy Relation of Gamma Ray Bursts and Its Interpretations
Demosthenes Kazanas,Lev G. Titarchuk,Xin-Min Hua
Physics , 1997, DOI: 10.1086/305131
Abstract: Fenimore et al. (1995) have recently presented a very tight correlation between the spectral and the temporal structure in Gamma Ray Bursts (hereafter GRBs). In particular, they discovered that the durations of the constituent subpulses which make up the time profile of a given GRB have a well defined power-law dependence, of index $\simeq 0.45$, on the energy $E$ of the observed photons. In this note we present two simple models which can account in a straightforward fashion for the observed correlation. These models involve: (a) The impulsive injection of a population of relativistic electrons and their subsequent cooling by synchrotron radiation. (b) The impulsive injection of monoenergetic high energy photons in a medium of Thompson depth $\tau_T \sim 5$ and their subsequent downgrading in energy due to electron scattering. We present arguments for distinguishing between these two models from the existing data.
Quantization of Soliton Cellular Automata
Demosthenes Ellinas,Elena P. Papadopoulou,Yiannis G. Saridakis
Physics , 2000, DOI: 10.2991/jnmp.2001.8.Supplement.17
Abstract: A method of quantization of classical soliton cellular automata (QSCA) is put forward that provides a description of their time evolution operator by means of quantum circuits that involve quantum gates from which the associated Hamiltonian describing a quantum chain model is constructed. The intrinsic parallelism of QSCA, a phenomenon first known from quantum computers, is also emphasized.
The Magnetic Field of the Ultraluminous X-ray Pulsar M82 X-2
Dimitris M. Christodoulou,Silas G. T. Laycock,Demosthenes Kazanas
Physics , 2014,
Abstract: Pulsations were recently detected from the ultraluminous X-ray source X-2 in M82. The newly discovered pulsar has been described as a common neutron star with a 1 TG magnetic field that accretes above the Eddington rate and as a magnetar-like pulsar with a 100 TG magnetic field that is above the quantum limit. We show here that this X-ray source is not exotic in any sense. The standard equations of accretion along field lines predict that, for the measured spin period $P_S$ and spinup rate $\dot{P_S}$, the isotropic X-ray luminosity $L_X$ must be near the Eddington limit (i.e., $L_{X}\approx 3.5\times 10^{38}$~erg~s$^{-1}$); and that the surface magnetic field $B$, that does not depend on $P_S$, must be modest (i.e., $B_*\approx 1-10$ TG). The observed higher luminosity can be explained by a moderate amount of geometric beaming that occurs in our direction. Other ultraluminous X-ray sources may also turn out to be common pulsars with similar physical characteristics, but since the emission must occur at a favorable angle to the observer, we expect that very few such pulsars will be discovered in the future.
COPD exacerbation: Lost in translation
Demosthenes Makris, Demosthenes Bouros
BMC Pulmonary Medicine , 2009, DOI: 10.1186/1471-2466-9-6
Abstract: Chronic Obstructive Pulmonary Disease (COPD) is characterized by exacerbations which are caused mainly by infections of the tracheobronchial tree or by inhalation of toxic gases [1]. During an exacerbation airway inflammation augments and a sustained worsening of patient's condition from the stable state and beyond normal day-to-day variations is observed. COPD exacerbations are a major cause of hospital admissions and frequent exacerbations are associated with increased mortality and impaired health-related quality of life [2]. Previous studies reported also that patients who experience frequently exacerbations may present an accelerating rate of lung function decline [3,4]. In this respect, the management of exacerbations by prompt diagnosis and effective treatment that reduces exacerbation frequency [5,6], should be a major goal in COPD.However, despite the considerable progress in the understanding of the pathobiology of exacerbations and in the evaluation of their consequences, yet, there is no standardised definition of an exacerbation. The landmark study of Fletcher and Peto[7] published in seventies used the definition of "bronchial infections" (chest cold or illnesses during which phlegm production had increased). Later, the Lung Health Study[8] used the definition of "physician visits for lower respiratory illness", while in recent studies such as in the East London Study[3] and in a study performed in Greece[4], the definition of an exacerbation was based on criteria described previously by Anthonisen [9]. These criteria require either, increase of at least two major respiratory symptoms (dyspnea, sputum amount, and sputum purulence) or, increase of one major symptom in addition to at least one minor symptom (wheeze, cough, fever, nasal discharge, sore throat), for at least two consecutive days. Thus, in those previous studies, definitions were based either on patient reported symptom changes [3,4] or, on "healthcare utilisation" due to the worsening of p
The Case against Dark Matter and Modified Gravity: Flat Rotation Curves Are a Rigorous Requirement in Rotating Self-Gravitating Newtonian Gaseous Discs  [PDF]
Dimitris M. Christodoulou, Demosthenes Kazanas
Journal of Modern Physics (JMP) , 2016, DOI: 10.4236/jmp.2016.77067
Abstract: By solving analytically the various types of Lane-Emden equations with rotation, we have discovered two new coupled fundamental properties of rotating, self-gravitating, gaseous discs in equilibrium: isothermal discs must, on average, exhibit strict power-law density profiles in radius x on their equatorial planes of the form \"\" , where A and k-1 are the integration constants; and “flat” rotation curves precisely such as those observed in spiral galaxy discs. Polytropic discs must, on average, exhibit strict density profiles of the form \"\" , where n is the polytropic index; and “flat” rotation curves described by square roots of upper incomplete gamma functions. By “on average”, we mean that, irrespective of the chosen boundary conditions, the actual profiles must oscillate around and remain close to the strict mean profiles of the analytic singular equilibrium solutions. We call such singular solutions the “intrinsic” solutions of the differential equations because they are demanded by the second-order equations themselves with no regard to the Cauchy problem. The results are directly applicable to gaseous galaxy discs that have long been known to be isothermal and to protoplanetary discs during the extended isothermal and adiabatic phases of their evolution. In galactic gas dynamics, they have the potential to resolve the dark matter—modified gravity controversy in a sweeping manner, as they render both of these hypotheses unnecessary. In protoplanetary disc research, they provide observers with a powerful new probing tool, as they predict a clear and simple connection between the radial density profiles and the rotation curves of self-gravitating discs in their very early (pre-Class 0) phases of evolution.
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