Performance improvement in geographic routing for vehicular Ad Hoc networks

Geographic routing is one of the most investigated themes by researchers for reliable and efficient dissemination of information in Vehicular Ad Hoc Networks (VANETs). Recently, different Geographic Distance Routing (GEDIR) protocols have been suggested in the literature. These protocols focus on reducing the forwarding region towards destination to select the Next Hop Vehicles (NHV). Most of these protocols suffer from the problem of elevated one-hop link disconnection, high end-to-end delay and low throughput even at normal vehicle speed in high vehicle density environment. This paper proposes a Geographic Distance Routing protocol based on Segment vehicle, Link quality and Degree of connectivity (SLD-GEDIR). The protocol selects a reliable NHV using the criteria segment vehicles, one-hop link quality and degree of connectivity. The proposed protocol has been simulated in NS-2 and its performance has been compared with the state-of-the-art protocols: P-GEDIR, J-GEDIR and V-GEDIR. The empirical results clearly reveal that SLD-GEDIR has lower link disconnection and end-to-end delay, and higher throughput as compared to the state-of-the-art protocols. It should be noted that the performance of the proposed protocol is preserved irrespective of vehicle density and spee

Altered Arterial Stiffness and Subendocardial Viability Ratio in Young Healthy Light Smokers after Acute Exercise

Studies showed that long-standing smokers have stiffer arteries at rest. However, the effect of smoking on the ability of the vascular system to respond to increased demands (physical stress) has not been studied. The purpose of this study was to estimate the effect of smoking on arterial stiffness and subendocardial viability ratio, at rest and after acute exercise in young healthy individuals.Healthy light smokers (n = 24, pack-years = 2.9) and non-smokers (n = 53) underwent pulse wave analysis and carotid-femoral pulse wave velocity measurements at rest, and 2, 5, 10, and 15 minutes following an exercise test to exhaustion. Smokers were tested, 1) after 12h abstinence from smoking (chronic condition) and 2) immediately after smoking one cigarette (acute condition). At rest, chronic smokers had higher augmentation index and lower aortic pulse pressure than non-smokers, while subendocardial viability ratio was not significantly different. Acute smoking increased resting augmentation index and decreased subendocardial viability ratio compared with non-smokers, and decreased subendocardial viability ratio compared with the chronic condition. After exercise, subendocardial viability ratio was lower, and augmentation index and aortic pulse pressure were higher in non-smokers than smokers in the chronic and acute conditions. cfPWV rate of recovery of was greater in non-smokers than chronic smokers after exercise. Non-smokers were also able to achieve higher workloads than smokers in both conditions.Chronic and acute smoking appears to diminish the vascular response to physical stress. This can be seen as an impaired 'vascular reserve' or a blunted ability of the blood vessels to accommodate the changes required to achieve higher workloads. These changes were noted before changes in arterial stiffness or subendocardial viability ratio occurred at rest. Even light smoking in young healthy individuals appears to have harmful effects on vascular function, affecting the ability of the vascular bed to respond to increased demands

Aortic stenosis in the elderly: Challenges in diagnosis and therapy

Severe aortic valve stenosis, remains the main cause of morbidity and mortality in the elderly, reaching a prevalence of 2-7% above the age of 65 years old. Despite its frequency and the development in invasive and noninvasive approach of the disease, several of its aspects remain controversial. This review is focused on the clinical aspects, the indices for assessment severity, newly markers related to prognosis and new therapeutic modalities for the elderly population. The term low flow, low gradient severe aortic stenosis with preserved LV systolic function has revealed a new modality in the field of diagnostic evaluation and therapeutic approach. Aortic valve replacement is the choice therapy for symptomatic severe aortic stenosis. Despite the recent advances in cardiac surgery, the overall operative mortality rate for isolated aortic valve replacement surgery ranges from 2.5% to 4.0% and is higher in octogenarians and can be up to 25% in patients with comorbid conditions. The fact that surgery is not being performed for 30% or more of patients requiring it, a great attention was attracted to the percutaneous transcatheter implantation of a stent-mounted aortic valve. The up to now experience of transcatheter valve implantation in more than 25,000 patients, has shown promising results in terms of mortality and quality of life. Echocardiography still plays the central role for the evaluation of the elderly patient, as it can illustrate the pathophysiological alterations during the course of aortic valve stenosis, and guide appropriate therapy. © 2011 Elsevier Ireland Ltd

Sensorineural hearing loss complicating severe rickettsial diseases: Report of two cases

Sub-acute focal neurological manifestations are reported rarely in systemic rickettsial diseases and are considered to be secondary to immune-mediated mechanisms. We present two cases of transient sensorineural hearing loss complicating the course of severe rickettsial diseases caused by Rickettsia typhi and Rickettsia conorii, respectively. The diagnosis was based on the presence of high IgM antibodies and the prompt response to doxycycline treatment. In both cases, hearing loss presented during convalescence and resolved automatically without administration of specific treatment. © 2007 The British Infection Society

Systemic vasculitis with gastrointestinal involvement in an HIV-infected adult

Several types of human immunodeficiency virus (HIV)-associated vasculitides, including polyarteritis nodosa-like syndromes have been reported in patients with HIV infection. The pathogenic mechanism is thought to be related to either circulating immune complexes or direct endothelial involvement by HIV per se. In HIV-related necrotizing systemic vasculitis, affected arteries are smaller than those seen in classic polyarteritis nodosa, and it rarely becomes a multisystem and life-threatening disease with the exception of cases with heart, kidney, central nervous system, or gut involvement. We describe a case of systemic necrotizing vasculitis in an HIV-infected individual presented with fever, purpuric rash, and polyarthritis who eventually had development of mesentery artery thrombosis and nephrotic syndrome. The patient, solely under triple antiretroviral therapy, remains symptom free, with no evidence of his multisystem disease and no progression of his HIV infection after 10 years of follow-up. All patients with a vasculitis of unidentified etiology should be evaluated for HIV infection. © Copyright 2008 Southern Society for Clinical Investigation