Accuracy and stability analysis of path loss exponent measurement for localization in wireless sensor network

In wireless sensor network localization, path loss model is often used to provide a conversion between distance and received signal strength (RSS). Path loss exponent is one of the main environmental parameters for path loss model to characterize the rate of conversion. Therefore, the accuracy of path loss exponent directly influences the results of RSS-to-distance conversion. When the conversion requires distance estimation from RSS value, small error of measured path loss exponent could lead to large error of the conversion output. To improve the localization results, the approaches of measuring accurate parameters from different environments have become important. Different approaches provide different measurement stabilities, depending on the performance and robustness of the approach. This paper presents four calibration approaches to provide measurements of path loss exponent based on measurement arrangement and transmitter/receiver node’s allocation. These include one-line measurement, online-update spread locations measurement, online-update small-to big rectangular measurement, and online-update big-to-small rectangular measurement. The first two are general approaches, and the last two are our newly proposed approaches. Based on our research experiments, a comparison is presented among the four approaches in terms of accuracy and stability. The results show that both online-update rectangular measurements have better stability of measurements. For accuracy of measurement, online-update big-to-small rectangular measurement provides the best result after convergence

Measurement arrangement for the estimation of path loss exponent in wireless sensor network

Path loss model is generally used to relate distance and signal strength in wireless applications. This has been widely implemented in ranging, localization, and location tracking systems. A range of extension models have been proposed to enhance the performance for various environments and applications. Nevertheless, path loss exponent remains its significance as the main factor in the model regardless of how the model is varied. Based on the nature as an exponent of the model, inaccurate path loss exponent amplifies the error if it is used to estimate distance from received signal strength. Therefore, measurement of accurate value for path loss exponent becomes very important as it directly influences the output of distance estimation. Researchers have been studying the methods of measuring accurate path loss exponent in various environments. Instead of emphasizing the calculation process, this paper focuses more on the allocation of transmitters and receivers, and the arrangement among them. From the results obtained from experiments, properly arranged transmitter and receiver nodes provides better estimation of the path loss exponent. Based on the results, this paper also proposes a suitable nodes arrangement scheme for path loss exponent estimation

Entomologic and molecular investigation into Plasmodium vivax transmission in Singapore, 2009

<p>Abstract</p> <p>Background</p> <p>Singapore has been certified malaria free since November 1982 by the World Health Organization and despite occasional local transmission, the country has maintained the standing. In 2009, three clusters of malaria cases were reported in Singapore.</p> <p>Methods</p> <p>Epidemiological, entomological and molecular studies were carried out to investigate the three clusters, namely Mandai-Sungei Kadut, Jurong Island and Sembawang.</p> <p>Results</p> <p>A total of 29 malaria patients, with no recent travel history, were reported in the three clusters. Molecular analysis based on the <it>msp3α </it>and <it>msp1 </it>genes showed two independent local transmissions: one in Mandai-Sungei Kadut and another in Sembawang. Almost all cases within each cluster were epidemiologically linked. In Jurong Island cluster, epidemiological link remains uncertain, as almost all cases had a unique genetic profile. Only two cases shared a common profile and were found to be linked to the Mandai-Sungei Kadut cluster. Entomological investigation found <it>Anopheles sinensis </it>to be the predominant Anopheline in the two areas where local transmission of <it>P. vivax </it>was confirmed. <it>Anopheles sinensis </it>was found to be attracted to human bait and bites as early as 19:45 hrs. However, all <it>Anopheles </it>mosquitoes caught were negative for sporozoites and oocysts by dissection.</p> <p>Conclusion</p> <p>Investigation of <it>P. vivax </it>cases from the three cluster areas confirmed the occurrence of local transmission in two areas. Although <it>An. sinensis </it>was the predominant Anopheline found in areas with confirmed transmission, the vector/s responsible for the outbreaks still remains cryptic.</p

Naturally Acquired Human Plasmodium knowlesi Infection, Singapore

Naturally Acquired Human Plasmodium knowlesi Infection, Singapor

Isolation and Genetic Characteristics of Human Genotype 1 Japanese Encephalitis Virus, China, 2009

BACKGROUND: Several studies have shown that the predominant genotype of Chinese Japanese encephalitis virus (JEV) is evolving from genotype 3 to genotype 1. However, in recent years, almost all genotype 1 isolates were from mosquitoes, and genotype 1 has been less associated with human disease than genotype 3. This study reports the isolation of human genotype 1 JEV and its genetic characteristics to provide additional insights into human JE pathogens that are currently circulating in China. METHODS AND RESULTS: In 2009, 31 cerebrospinal fluid samples were collected from patients living in Yunnan and Shanxi provinces and were used to inoculate Aedes albopictus C6/36 cells for virus isolation. The JEV strains were identified using immunofluorescent assays and the reverse transcription-polymerase chain reaction. Phylogenetic analyses based on the partial capsid/pre-membrane and full envelope (E) sequences were performed using Clustalx 1.8 software. Three JEV isolates were obtained from a 4-year-old girl and a 2-year-old boy living in Yunnan and an 82-year-old woman in Shanxi. The boy had been immunized with one dose of JE live attenuated vaccine. New isolates were grouped into genotype 1. Amino acid sequence for the viral E protein indicated 95% to 100% identity with each other and with other JEV strains. When compared with a consensus sequence of E protein, two amino acid substitutions were found: Ser(E-123)-Asn in the two Yunnan isolates and Lys(E-166)-Arg in the Shanxi isolate. CONCLUSIONS: Our findings indicate that the genotype 1 of JEV is causing human infections in China. Our observation of a previously vaccinated boy developing JE from genotype 1 virus infection also calls for more detailed studies, both in vitro and in vivo neutralization tests as well as active surveillance, to examine the possibility of a lack of complete protection conferred by the live attenuated JE vaccine against genotype 1 virus

A human PrM antibody that recognizes a novel cryptic epitope on dengue E glycoprotein

10.1371/journal.pone.0033451PLoS ONE74

Interplay between SIN3A and STAT3 Mediates Chromatin Conformational Changes and GFAP Expression during Cellular Differentiation

BACKGROUND: Neurons and astrocytes are generated from common neural precursors, yet neurogenesis precedes astrocyte formation during embryogenesis. The mechanisms of neural development underlying suppression and de-suppression of differentiation-related genes for cell fate specifications are not well understood. METHODOLOGY/PRINCIPAL FINDINGS: By using an in vitro system in which NTera-2 cells were induced to differentiate into an astrocyte-like lineage, we revealed a novel role for Sin3A in maintaining the suppression of GFAP in NTera-2 cells. Sin3A coupled with MeCP2 bound to the GFAP promoter and their occupancies were correlated with repression of GFAP transcription. The repression by Sin3A and MeCP2 may be an essential mechanism underlying the inhibition of cell differentiation. Upon commitment toward an astrocyte-like lineage, Sin3A- MeCP2 departed from the promoter and activated STAT3 simultaneously bound to the promoter and exon 1 of GFAP; meanwhile, olig2 was exported from nuclei to the cytoplasm. This suggested that a three-dimensional or higher-order structure was provoked by STAT3 binding between the promoter and proximal coding regions. STAT3 then recruited CBP/p300 to exon 1 and targeted the promoter for histone H3K9 and H3K14 acetylation. The CBP/p300-mediated histone modification further facilitates chromatin remodeling, thereby enhancing H3K4 trimethylation and recruitment of RNA polymerase II to activate GFAP gene transcription. CONCLUSIONS/SIGNIFICANCE: These results provide evidence that exchange of repressor and activator complexes and epigenetic modifications are critical strategies for cellular differentiation and lineage-specific gene expression

Global patient outcomes after elective surgery: prospective cohort study in 27 low-, middle- and high-income countries.

BACKGROUND: As global initiatives increase patient access to surgical treatments, there remains a need to understand the adverse effects of surgery and define appropriate levels of perioperative care. METHODS: We designed a prospective international 7-day cohort study of outcomes following elective adult inpatient surgery in 27 countries. The primary outcome was in-hospital complications. Secondary outcomes were death following a complication (failure to rescue) and death in hospital. Process measures were admission to critical care immediately after surgery or to treat a complication and duration of hospital stay. A single definition of critical care was used for all countries. RESULTS: A total of 474 hospitals in 19 high-, 7 middle- and 1 low-income country were included in the primary analysis. Data included 44 814 patients with a median hospital stay of 4 (range 2-7) days. A total of 7508 patients (16.8%) developed one or more postoperative complication and 207 died (0.5%). The overall mortality among patients who developed complications was 2.8%. Mortality following complications ranged from 2.4% for pulmonary embolism to 43.9% for cardiac arrest. A total of 4360 (9.7%) patients were admitted to a critical care unit as routine immediately after surgery, of whom 2198 (50.4%) developed a complication, with 105 (2.4%) deaths. A total of 1233 patients (16.4%) were admitted to a critical care unit to treat complications, with 119 (9.7%) deaths. Despite lower baseline risk, outcomes were similar in low- and middle-income compared with high-income countries. CONCLUSIONS: Poor patient outcomes are common after inpatient surgery. Global initiatives to increase access to surgical treatments should also address the need for safe perioperative care. STUDY REGISTRATION: ISRCTN5181700