A survey of performance enhancement of transmission control protocol (TCP) in wireless ad hoc networks

This Article is provided by the Brunel Open Access Publishing Fund - Copyright @ 2011 Springer OpenTransmission control protocol (TCP), which provides reliable end-to-end data delivery, performs well in traditional wired network environments, while in wireless ad hoc networks, it does not perform well. Compared to wired networks, wireless ad hoc networks have some specific characteristics such as node mobility and a shared medium. Owing to these specific characteristics of wireless ad hoc networks, TCP faces particular problems with, for example, route failure, channel contention and high bit error rates. These factors are responsible for the performance degradation of TCP in wireless ad hoc networks. The research community has produced a wide range of proposals to improve the performance of TCP in wireless ad hoc networks. This article presents a survey of these proposals (approaches). A classification of TCP improvement proposals for wireless ad hoc networks is presented, which makes it easy to compare the proposals falling under the same category. Tables which summarize the approaches for quick overview are provided. Possible directions for further improvements in this area are suggested in the conclusions. The aim of the article is to enable the reader to quickly acquire an overview of the state of TCP in wireless ad hoc networks.This study is partly funded by Kohat University of Science & Technology (KUST), Pakistan, and the Higher Education Commission, Pakistan

Regulation of immunity during visceral Leishmania infection

Unicellular eukaryotes of the genus Leishmania are collectively responsible for a heterogeneous group of diseases known as leishmaniasis. The visceral form of leishmaniasis, caused by L. donovani or L. infantum, is a devastating condition, claiming 20,000 to 40,000 lives annually, with particular incidence in some of the poorest regions of the world. Immunity to Leishmania depends on the development of protective type I immune responses capable of activating infected phagocytes to kill intracellular amastigotes. However, despite the induction of protective responses, disease progresses due to a multitude of factors that impede an optimal response. These include the action of suppressive cytokines, exhaustion of specific T cells, loss of lymphoid tissue architecture and a defective humoral response. We will review how these responses are orchestrated during the course of infection, including both early and chronic stages, focusing on the spleen and the liver, which are the main target organs of visceral Leishmania in the host. A comprehensive understanding of the immune events that occur during visceral Leishmania infection is crucial for the implementation of immunotherapeutic approaches that complement the current anti-Leishmania chemotherapy and the development of effective vaccines to prevent disease.The research leading to these results has received funding from the European Community’s Seventh Framework Programme under grant agreement No.602773 (Project KINDRED). VR is supported by a post-doctoral fellowship granted by the KINDReD consortium. RS thanks the Foundation for Science and Technology (FCT) for an Investigator Grant (IF/00021/2014). This work was supported by grants to JE from ANR (LEISH-APO, France), Partenariat Hubert Curien (PHC) (program Volubilis, MA/11/262). JE acknowledges the support of the Canada Research Chair Program

Depression and migraine Depressão e migrânea

The objective of this study was to evaluate both the presence and intensity of depressive symptoms in patients with episodic migraine (EM) and transformed migraine (TM) or chronic migraine, comparing them with a control group. Beck Depression Inventory (BDI) was used for this purpose. The median of BDI score of the control group was significantly lower than the EM and TM groups (p<0.0005). Either the EM or the TM did not show any significant difference in relation to the median of BDI scores (p=0.12). The TM group showed a higher frequency of severe depression when analyzed qualitatively by dependence analysis. Symptoms of severe depression by means of qualitative analysis may strengthen a co-morbidity between depression and transformed migraine. This association might be considered rather a factor of TM perpetuation than a risk factor for the transformation of EM into TM.<br>O objetivo deste estudo foi avaliar a presença e a intensidade de sintomas depressivos entre pacientes com migrânea episódica (ME) e migrânea transformada (MT) ou migrânea crônica, comparando-os com um grupo controle. O Inventário de Depressão de Beck (IDB) foi aplicado para esta finalidade. A mediana das pontuações do IDB do grupo controle foi significantemente menor que a dos grupos ME e MT (p< 0,0005). Os grupos ME e MT não apresentaram diferenças significantes em suas medianas das pontuações (p=0,12). Quando avaliados de forma qualitativa, pela análise de dependência, o grupo MT apresentou freqüência maior de depressão severa. Sintomatologia depressiva mais severa do ponto de vista qualitativo poderia reforçar possível co-morbidade entre depressão e migrânea transformada. Esta associação poderia ser considerada mais como um fator de perpetuação da MT do que um fator de risco de transformação da ME para a MT