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

Health and economic impact of HIV/AIDS on South African households: a cohort study

BACKGROUND: South African households are severely affected by human immunodeficiency virus / acquired immunodeficiency syndrome (HIV/AIDS) but health and economic impacts have not been quantified in controlled cohort studies. METHODS: We compared households with an HIV-infected member, and unaffected neighbouring households, in one rural and one urban area in Free State province, South Africa. Interviews were conducted with one key informant in each household, at baseline and six months later. We studied 1913 members of 404 households, with 94% and 96% follow up, respectively. Household and individual level analyses were done. RESULTS: Members of affected households, compared to members of unaffected households, were independently more likely to be continuously ill (adjusted odds ratio (OR) 2.1, 95% CI 1.3–3.4 at follow up), and to die (adjusted OR 3.4, 95% CI 1.0–11), mainly due to infectious diseases. Government clinics and hospitals were the main sources of health care. Affected households were poorer than unaffected households at baseline (relative income per person 0.61, 95% CI 0.49–0.76). Over six months expenditure and income decreased more rapidly in affected than in unaffected households (baseline-adjusted relative expenditure 0.86, 95% CI 0.75–0.99 and income 0.89, 95% CI 0.75–1.05). Baseline morbidity was independently associated with lower income and expenditure at baseline but not with changes over six months. CONCLUSIONS: HIV/AIDS affects the health and wealth of households as well as infected individuals, aggravating pre-existing poverty

Identification of Termite Species and Subspecies of the Genus Zootermopsis Using Near-Infrared Reflectance Spectroscopy

Dampwood termites of the genus Zootermopsis (Isoptera: Termopsidae) are an abundant group of basal termites found in temperate forests of western North America. Three species are currently recognized in the genus and one of these species is subdivided into two subspecies. Although morphological and genetic characters are useful in differentiating among the three species and the two subspecies, respectively, only hydrocarbon analysis can enable differentiation both among the three species and the two subspecies. Due to the limitations of hydrocarbon analysis, such as the need for fresh specimens, alternative methods that could rapidly and accurately identify Zootermopsis would be useful. Using a partial least squares analysis of near-infrared spectra, each of the Zootermopsis species and subspecies were identified with greater than 95% and 80% accuracy, respectively. Neural network analysis of the near-infrared spectra successfully enabled the identification of the species and subspecies with greater than 99% accuracy. The inexpensive, reproducible, and rapid nature of near-infrared spectroscopy makes it a viable alternative to morphological, hydrocarbon, or genetic analysis for identifying Zootermopsis

Assessing the Validity of Sexual Behaviour Reports in a Whole Population Survey in Rural Malawi

Background: Sexual behaviour surveys are widely used, but under-reporting of particular risk behaviours is common, especially by women. Surveys in whole populations provide an unusual opportunity to understand the extent and nature of such under-reporting.Methods: All consenting individuals aged between 15 and 59 within a demographic surveillance site in northern Malawi were interviewed about their sexual behaviour. Validity of responses was assessed by analysis of probing questions; by comparison of results with in-depth interviews and with Herpes simplex type-2 (HSV-2) seropositivity; by comparing reports to same sex and opposite sex interviewers; and by quantifying the partnerships within the local community reported by men and by women, adjusted for response rates.Results: 6,796 women and 5,253 men (83% and 72% of those eligible) consented and took part in sexual behaviour interviews. Probing questions and HSV-2 antibody tests in those who denied sexual activity identified under-reporting for both men and women. Reports varied little by sex or age of the interviewer. The number of marital partnerships reported was comparable for men and women, but men reported about 4 times as many non-marital partnerships. The discrepancy in reporting of non-marital partnerships was most marked for married women (men reported about 7 times as many non-marital partnerships with married women as were reported by married women themselves), but was only apparent in younger married women.Conclusions: We have shown that the under-reporting of non-marital partnerships by women was strongly age-dependent. The extent of under-reporting of sexual activity by young men was surprisingly high. The results emphasise the importance of triangulation, including biomarkers, and the advantages of considering a whole population

Costs of a successful public-private partnership for TB control in an urban setting in Nepal

<p>Abstract</p> <p>Background</p> <p>In South Asia a large number of patients seek treatment for TB from private practitioners (PPs), and there is increasing international interest in involving PPs in TB control. To evaluate the feasibility, effectiveness and costs of public-private partnerships (PPPs) for TB control, a PPP was developed in Lalitpur municipality, Nepal, where it is estimated that 50% of patients with TB are managed in the private sector. From the clinical perspective the PPP was shown to be effective. The aim of this paper is to assess and report on the costs involved in the PPP scheme.</p> <p>Methods</p> <p>The approach to costing took a comprehensive view, with inclusion of costs not only incurred by health facilities but also social costs borne by patients and their escorts. Semi-structured questionnaires and guided interviews were used to collect start-up and recurrent costs for the scheme.</p> <p>Results</p> <p>Overall costs for treating a TB patient under the PPP scheme averaged US$89.60. Start-up costs per patient represented 12% of the total budget. Half of recurrent costs were incurred by patients and their escorts, with institutional costs representing most of the rest. Female patients tended to spend more and patients referred from the private sector had the highest reported costs.</p> <p>Conclusion</p> <p>Treating TB patients in the PPP scheme had a low additional cost, while doubling the case notification rate and maintaining a high success rate. Costs incurred by patients and their escorts were the largest contributors to the overall total. This suggests a focus for follow-up studies and for cost-minimisation strategies.</p

Adaptive access and rate control of CSMA for energy, rate and delay optimization

In this article, we present a cross-layer adaptive algorithm that dynamically maximizes the average utility function. A per stage utility function is defined for each link of a carrier sense multiple access-based wireless network as a weighted concave function of energy consumption, smoothed rate, and smoothed queue size. Hence, by selecting weights we can control the trade-off among them. Using dynamic programming, the utility function is maximized by dynamically adapting channel access, modulation, and coding according to the queue size and quality of the time-varying channel. We show that the optimal transmission policy has a threshold structure versus the channel state where the optimal decision is to transmit when the wireless channel state is better than a threshold. We also provide a queue management scheme where arrival rate is controlled based on the link state. Numerical results show characteristics of the proposed adaptation scheme and highlight the trade-off among energy consumption, smoothed data rate, and link delay.This study was supported in part by the Spanish Government, Ministerio de Ciencia e Innovación (MICINN), under projects COMONSENS (CSD2008-00010, CONSOLIDER-INGENIO 2010 program) and COSIMA (TEC2010-19545-C04-03), in part by Iran Telecommunication Research Center under contract 6947/500, and in part by Iran National Science Foundation under grant number 87041174. This study was completed while M. Khodaian was at CEIT and TECNUN (University of Navarra)

Bacterial Transmembrane Proteins that Lack N-Terminal Signal Sequences

Tail-anchored membrane proteins (TAMPs), a class of proteins characterized by their lack of N-terminal signal sequence and Sec-independent membrane targeting, play critical roles in apoptosis, vesicle trafficking and other vital processes in eukaryotic organisms. Until recently, this class of membrane proteins has been unknown in bacteria. Here we present the results of bioinformatic analysis revealing proteins that are superficially similar to eukaryotic TAMPs in the bacterium Streptomyces coelicolor. We demonstrate that at least four of these proteins are bona fide membrane-spanning proteins capable of targeting to the membrane in the absence of their N-terminus and the C-terminal membrane-spanning domain is sufficient for membrane targeting. Several of these proteins, including a serine/threonine kinase and the SecE component of the Sec translocon, are widely conserved in bacteria

Patient profiling for success after weight loss surgery (GO Bypass study): an interdisciplinary study protocol

Despite substantial research efforts, the mechanisms proposed to explain weight loss after gastric bypass (RYGB) and sleeve gastrectomy (SL) do not explain the large individual variation seen after these treatments. A complex set of factors are involved in the onset and development of obesity and these may also be relevant for the understanding of why success with treatments vary considerably between individuals. This calls for explanatory models that take into account not only biological determinants but also behavioral, affective and contextual factors. In this prospective study, we recruited 47 women and 8 men, aged 25–56 years old, with a BMI of 45.8 ± 7.1 kg/m2 from the waiting list for RYGB and SL at Køge hospital, Denmark. Pre-surgery and 1.5, 6 and 18 months after surgery we assessed various endpoints spanning multiple domains. Endpoints were selected on basis of previous studies and include: physiological measures: anthropometrics, vital signs, biochemical measures and appetite hormones, genetics, gut microbiota, appetite sensation, food and taste preferences, neural sensitivity, sensory perception and movement behaviors; psychological measures: general psychiatric symptom-load, depression, eating disorders, ADHD, personality disorder, impulsivity, emotion regulation, attachment pattern, general self-efficacy, alexithymia, internalization of weight bias, addiction, quality of life and trauma; and sociological and anthropological measures: sociodemographic measures, eating behavior, weight control practices and psycho-social factors. Joining these many endpoints and methodologies from different scientific disciplines and creating a multi-dimensional predictive model has not previously been attempted. Data on the primary endpoint are expected to be published in 2018

Exposure of neonatal rats to maternal cafeteria feeding during suckling alters hepatic gene expression and DNA methylation in the insulin signalling pathway

Nutrition in early life is a determinant of lifelong physiological and metabolic function. Diseases that are associated with ageing may, therefore, have their antecedents in maternal nutrition during pregnancy and lactation. Rat mothers were fed either a standard laboratory chow diet (C) or a cafeteria diet (O) based upon a varied panel of highly palatable human foods, during lactation. Their offspring were then weaned onto chow or cafeteria diet giving four groups of animals (CC, CO, OC, OO n=9-10). Livers were harvested 10 weeks post-weaning for assessment of gene and protein expression, and DNA methylation. Cafeteria feeding post-weaning impaired glucose tolerance and was associated with sex-specific altered mRNA expression of peroxisome proliferator activated receptor gamma (PPARg) and components of the insulin-signalling pathway (Irs2, Akt1 and IrB). Exposure to the cafeteria diet during the suckling period modified the later response to the dietary challenge. Post-weaning cafeteria feeding only down-regulated IrB when associated with cafeteria feeding during suckling (group OO, interaction of diet in weaning and lactation P=0.041). Responses to cafeteria diet during both phases of the experiment varied between males and females. Global DNA methylation was altered in the liver following cafeteria feeding in the post-weaning period, in males but not females. Methylation of the IrB promoter was increased in group OC, but not OO (P=0.036). The findings of this study add to a growing evidence base that suggests tissue function across the lifespan a product of cumulative modifications to the epigenome and transcriptome, which may be both tissue and sex-specific

A single-player Monte Carlo tree search method combined with node importance for virtual network embedding

© 2020, Institut Mines-Télécom and Springer Nature Switzerland AG. As a critical technology in network virtualization, virtual network embedding (VNE) focuses on how to allocate physical resources to virtual network requests efficiently. Because the VNE problem is NP-hard, most of the existing approaches are heuristic-based algorithms that tend to converge to a local optimal solution and have a low performance. In this paper, we propose an algorithm that combines the basic Monte Carlo tree search (MCTS) method with node importance to apply domain-specific knowledge. For a virtual network request, we first model the embedding process as a finite Markov decision process (MDP), where each virtual node is embedded in one state in the order of node importance that we design. The shortest-path algorithm is then applied to embed links in the terminal state and return the cost as a part of the reward. Due to the reward delay mechanism of the MDP, the result of link mapping can affect the action selected in the previous node mapping stage, coordinating the two embedding stages. With node importance, domain-specific knowledge can be used in the Expansion and Simulation stages of MCTS to speed up the search and estimate the simulation value more accurately. The experimental results show that, compared with the existing classic algorithms, our proposed algorithm can improve the performance of VNE in terms of the average physical node utilization ratio, acceptance ratio, and long-term revenue to cost ratio