Variation of Input Impedance with Feeding Position in Probe and inset-Fed Microstrip Patch Antenna

Proper impedance matching of a microstrip patch antenna to the feed line is paramount for efficient radiation. However, impedance matching in such a system is not easy and consequently most systems suffer from return losses. The variation of the input impedance of a probe-fed and inset-fed rectangular microstrip patch antennas along the longitudinal and transverse lengths is investigated on probe-fed and microstrip-fed antenna operating at 2.4GHz and 2.0GHz respectively. FEKO simulation software is used to evaluate and characterize the behaviour of the input resistance for varying values of feeding position. It is observed that the transverse variation in the input resistance is very minimal. The conclusion drawn here is that a cosine squared and shifted cosine squared function can be used to exactly locate the feed point in a probe and inset fed antennas respectively for an impedance matched antenna system.   Keywords: Longitudinal feeding position, FEKO, probe feeding, inset feeding, input impedance, return loss

Treatment of shigella infections: why sulfamethoxazole-trimethoprim, tetracyclines and ampicillin should no longer be used

Background: Bloody diarrhoea results in high morbidity and mortality especially in developing countries with shigellosis being the main cause of acute bloody diarrhoea. The use of appropriate antimicrobial agents in the treatment of acute diarrheal disease shortens the duration of illness and bacterial shedding leading to a reduction in morbidity and mortality. Treatment options for many infections are becoming limited due to globally emerging antibiotic resistance. Globally, resistance of shigella species to trimethoprim-sulfamethoxazole (TMP-SMX), tetracyclines and ampicillin has been reported with subsequent recommendations of not using these antimicrobial drugs for empirical therapy of acute bloody diarrhoea.Objective: To establish the antimicrobial susceptibility patterns and antimicrobial drug use for treatment of shigella species in patients with acute bloody diarrhoea.Design: A hospital based case control study.Setting: Six health facilities, three in Kilifi County and three in Nairobi County.Subject: A total of 284 stool specimens were collected from patients who fitted the standard cases definition for acute bloody diarrhoea.Results: Eighty (28.2%) bacterial isolates were recovered from 284 stool samples collected from cases presenting with acute bloody diarrhoea of which 67 (83.8%) were Shigella species, nine (11.3%) were Enteroinvassive Escherichia coli isolates, three (3.8%) were Salmonella Typhi and one (1.3%) were Yersinia enterocolitica. Shigella isolates had high resistance to sulfamethoxazole-trimethoprim (97%), tetracycline (83.6%) ampicillin (58.2%) and chloramphenicol (20.9%). The isolates showed low resistance to nalidixic (4.5%) and ciprofloxacin (3.0%) while there was no resistance to ceftriaxone. The most common multidrug resistance pattern detected in Shigella strains combined sulfamethoxazole-trimethoprim, amoxicillin/ampicillin and tetracyclines.Antibiotic prescriptions were given to 243(85.6%) of the patients presenting with acute bloody diarrhoea. Among these, 94 (38.7%) were given prescriptions for ciprofloxacin, 53 (21.8%) for sulfamethaxazole-trimethiprin and 36(14.8%) for Tetracyclines. Chloramphenicol, amoxicillin/ampicillin, nalidixic acid and ceftriaxone were prescribed to 10.7 %, 3.7%, 2.9% and 0.4% of the patients respectively. A total of 123 (51%) received antibiotics which were ranked to have high resistance (sulfamethoxazole-trimethoprim, tetracyclines ampicillin and chloramphenicol).Conclusion: The high rates of antimicrobial resistance among the commonly prescribed antimicrobials such as sulfamethoxazole-trimethoprim, tetracycline, ampicillin and chloramphenicol is of major concern. Despite recommendations discouraging the empirical use of sulfamethoxazole-trimethoprim, tetracycline, ampicillin and chloramphenicol for treatment of acute bloody diarrhoea, more than half of the patients with acute bloody diarrhoea were still treated with these antibiotics.There is need to train health care workers on the proper management of acute bloody diarrhoea and the importance of adhering to the clinical guidelines

Development of a botanical plant protection product from Larix by-products to protect grapevine from Plasmopara viticola

Extracts from European Larch (Larix decidua) were shown to be efficient to control grapevine downy mildew (Plasmopara viticola) under controlled and field conditions. Larixyl acetate and larixol were identified as the active compounds

Interaction Between Climatic, Environmental, and Demographic Factors on Cholera Outbreaks in Kenya

Background: Cholera remains an important public health concern in developing countries including Kenya where 11,769 cases and 274 deaths were reported in 2009 according to the World Health Organization (WHO). This ecological study investigates the impact of various climatic, environmental, and demographic variables on the spatial distribution of cholera cases in Kenya. Methods: District-level data was gathered from Kenya’s Division of Disease Surveillance and Response, the Meteorological Department, and the National Bureau of Statistics. The data included the entire population of Kenya from 1999 to 2009. Results: Multivariate analyses showed that districts had an increased risk of cholera outbreaks when a greater proportion of the population lived more than five kilometers from a health facility (RR: 1.025 per 1% increase; 95% CI: 1.010, 1.039), bordered a body of water (RR: 5.5; 95% CI: 2.472, 12.404), experienced increased rainfall from October to December (RR: 1.003 per 1 mm increase; 95% CI: 1.001, 1.005), and experienced decreased rainfall from April to June (RR: 0.996 per 1 mm increase; 95% CI: 0.992, 0.999). There was no detectable association between cholera and population density, poverty, availability of piped water, waste disposal methods, rainfall from January to March, or rainfall from July to September. Conclusion: Bordering a large body of water, lack of health facilities nearby, and changes in rainfall were significantly associated with an increased risk of cholera in Kenya

Taking tissue seriously means taking communities seriously

<p>Abstract</p> <p>Background</p> <p>Health research is increasingly being conducted on a global scale, particularly in the developing world to address leading causes of morbidity and mortality. While research interest has increased, building scientific capacity in the developing world has not kept pace. This often leads to the export of human tissue (defined broadly) from the developing to the developed world for analysis. These practices raise a number of important ethical issues that require attention.</p> <p>Discussion</p> <p>In the developed world, there is great heterogeneity of regulatory practices regarding human tissues. In this paper, we outline the salient ethical issues raised by tissue exportation, review the current ethical guidelines and norms, review the literature on what is known empirically about perceptions and practices with respect to tissue exportation from the developing to the developed world, set out what needs to be known in terms of a research agenda, and outline what needs to be done immediately in terms of setting best practices. We argue that the current status of tissue exportation is ambiguous and requires clarification lest problems that have plagued the developed world occur in the context of global heath research with attendant worsening of inequities. Central to solutions to current ethical concerns entail moving beyond concern with individual level consent and embracing a robust interaction with communities engaged in research.</p> <p>Conclusion</p> <p>Greater attention to community engagement is required to understand the diverse issues associated with tissue exportation.</p

The antiangiogenic activity of naturally occurring and synthetic homoisoflavonoids from the Hyacinthaceae (sensu APGII)

Excessive blood vessel formation in the eye is implicated in wet age-related macular degeneration, proliferative diabetic retinopathy, neovascular glaucoma, and retinopathy of prematurity, which are major causes of blindness. Small molecule antiangiogenic drugs are strongly needed to supplement existing biologics. Homoisoflavonoids have been previously shown to have potent antiproliferative activities in endothelial cells over other cell types. Moreover, they demonstrated a strong antiangiogenic potential in vitro and in vivo in animal models of ocular neovascularization. Here, we tested the antiangiogenic activity of a group of naturally occurring homoisoflavonoids isolated from the family Hyacinthaceae and related synthetic compounds, chosen for synthesis based on structure–activity relationship observations. Several compounds showed interesting antiproliferative and antiangiogenic activities in vitro on retinal microvascular endothelial cells, a disease-relevant cell type, with the synthetic chromane, 46, showing the best activity (GI50 of 2.3 × 10–4 μM)

Melanin production inhibitors from the West African 'Cassipourea congoensis'

Cassipourea congoensis (syn. Cassipourea malosana) is used in African countries as a skin-lightening agent. Two previously unreported cycloartane triterpenoids, 26-hydroxy-3-keto-24-methy lenecycloartan-30-oic acid 1 and 24-methylene-cycloartan-3β,26,30-triol 2 along with the known mahuannin B 3, 7-methoxymahuannin B 4, 7-methoxygeranin A 5, methyl-3-(4-hydroxy-3-methoxyphenyl)-2E-propenoate, glycerol-1-alkanoate, (E)-3-(4-hydroxy-3-methoxyphenyl)prop-2-enal 6, (-)-syringaresinol 7, and stigmast-5-en-3-O-β-D-glucoside, were isolated from the roots of C. congoensis. The crude extract and compounds 1 and 5 were found to inhibit the production of melanin at 10 μM with low cytotoxicity validating the ethno-medicinal use of this plan

The effect of isolates from 'Cassipourea flanaganii' (Schinz) alston, a plant used as a skin lightning agent, on melanin production and tyrosinase inhibition

Ethnopharmacological relevance The Zulu and Xhosa people of South Africa use the stem bark of Cassipourea flanaganii as a skin-lightning cosmetic. Aim of the study To isolate and identify compounds responsible for the skin lightning properties from the stem bark of Cassipourea flanaganii and to evaluate their cytotoxicity towards skin cells. Materials and methods Extracts from the stem bark of Cassipourea flanaganii were isolated using chromatographic methods and structures were determined using NMR, IR and MS analysis. The tyrosinase inhibitory activity and the ability to inhibit the production of melanin were determined using human primary epidermal melanocyte cells. Cytoxicity was established using the same melanocytes and a neutral red assay. Results One previously undescribed compound, ent-atis-16-en-19-al (1) along with the known ent-atis-16-en-19-oic acid (2), ent-atis-16-en-19-ol (3), ent-kaur-16-en-19-oic acid (4), ent-kaur-16-en-19-al (5), ent-manoyl oxide (6), guinesine A (7), guinesine B (8), guinesine C (9), lichenxanthone (10), 2,4-dihydroxy-3,6-dimethyl benzoic acid methyl ester (11), lynoside (12), lupeol (13), β-amyrin (14), docosyl ferulate (15), stigmasterol, sitosterol and sitosterol-O-glucoside were isolated in this investigation. An impure fraction containing compound 3 was acetylated to obtain 19-acetoxy-ent-atis-16-ene (3a). Compounds 10 and 11 are usually isolated from lichen, hence they are possible contaminants of lichen harvested with the bark. Compounds 1, 3a, 5–14 were not significantly cytotoxic to the primary epidermal melanocyte cells (P > 0.05) when compared to the negative and positive controls (DMSO, 0.1% and hydrogen peroxide, 30 wt% in water). Inhibition of tyrosinase was significantly greater with respect to the negative control (P < 0.001) for compounds 3a, 5–8 and 9–10 at 10 μM and for compounds 5–8 and 9–10 at 100 μM. Compared to hydroquinone (the positive control) at 10 μM, the level of inhibition was comparable or to that of compounds 3a, 5, 6, and 8–10 at 10 μM, with 9 and 10 showing a greater level of inhibition. Inhibition of melanin was both concentration and time dependent for all compounds tested with higher melanin content at 24 h compared to 48 h s and at 10 mM compared to100 mM at both time points; melanin content was significantly lower for hydroquinone at both time points and concentrations. Conclusions Compounds 1, 5–14, isolated from Cassipourea flanaganii and the derivative 3a showed low cytotoxicity. All compounds had a clear time and concentration dependent effect on melanin content which did not appear to be dependent on their inhibition of tyrosinase

Genome-wide evolutionary dynamics of influenza B viruses on a global scale

The global-scale epidemiology and genome-wide evolutionary dynamics of influenza B remain poorly understood compared with influenza A viruses. We compiled a spatio-temporally comprehensive dataset of influenza B viruses, comprising over 2,500 genomes sampled worldwide between 1987 and 2015, including 382 newly-sequenced genomes that fill substantial gaps in previous molecular surveillance studies. Our contributed data increase the number of available influenza B virus genomes in Europe, Africa and Central Asia, improving the global context to study influenza B viruses. We reveal Yamagata-lineage diversity results from co-circulation of two antigenically-distinct groups that also segregate genetically across the entire genome, without evidence of intra-lineage reassortment. In contrast, Victoria-lineage diversity stems from geographic segregation of different genetic clades, with variability in the degree of geographic spread among clades. Differences between the lineages are reflected in their antigenic dynamics, as Yamagata-lineage viruses show alternating dominance between antigenic groups, while Victoria-lineage viruses show antigenic drift of a single lineage. Structural mapping of amino acid substitutions on trunk branches of influenza B gene phylogenies further supports these antigenic differences and highlights two potential mechanisms of adaptation for polymerase activity. Our study provides new insights into the epidemiological and molecular processes shaping influenza B virus evolution globally