53 research outputs found
Whistler mode waves upstream of Saturn
Whistler-mode waves are generated within and can propagate upstream of
collisionless shocks. They are known to play a role in electron
thermodynamics/acceleration and, under certain conditions, are markedly
observed as wave trains preceding the shock ramp. In this paper, we take
advantage of Cassini's presence at ~10 AU to explore the importance of
whistler-mode waves in a parameter regime typically characterized by higher
Mach number (median of ~14) shocks, as well as a significantly different IMF
structure, compared to near Earth. We identify electromagnetic precursors
preceding a small subset of bow shock crossings with properties which are
consistent with whistler-mode waves. We find these monochromatic,
low-frequency, circularly-polarized waves to have a typical frequency range of
0.2 - 0.4 Hz in the spacecraft frame. This is due to the lower ion and electron
cyclotron frequencies near Saturn, between which whistler waves can develop.
The waves are also observed as predominantly right-handed in the spacecraft
frame, the opposite sense to what is typically observed near Earth. This is
attributed to the weaker Doppler shift, owing to the large angle between the
solar wind velocity and magnetic field vectors at 10 AU. Our results on the low
occurrence of whistler waves upstream of Saturn also underpins the
predominantly supercritical bow shock of Saturn.Comment: Published in Journal of Geophysical Research: Space Physics (January
2017) 21 pages, 4 figure
Some Important Observations on the Populations of Hooded Vultures Necrosyrtes monachus
Despite major declines in the population of vultures around the world, noticeable increases were reported in the populations of Hooded Vultures Necrosyrtes monachus over the past decade in Accra—an important vulture habitat in Ghana. In recent times, however, there is a growing concern that the vulture numbers are decreasing even though scientific data to support this is nonexisting. As a vital zoogeographical and conservation tool, it is important to keep an up-to-date knowledge about urban bird populations amidst rapid urbanization and associated changes. Using a combination of field data, literature review, and stakeholder consultations, it was indicative that severe decline might have indeed occurred in the populations of Hooded Vultures in Accra. Evidence suggests the killing of vultures for consumption, traditional medicine, and black magic in an undercover trade with possible transboundary connections as important underlying factor. Additional factors suspected to underlie the declines include changes in management of urban facilities and destruction of roosting and nesting trees. The implications of interspecific competition with Pied Crows Corvus albus on Hooded Vultures however remain unclear. There is an urgent need for conservation campaign and education to save the Hooded Vulture in Ghana
Quinolone resistance in Escherichia coli from Accra, Ghana
We documented for the first time the molecular basis for quinolone resistance in Ghana and the presence of horizontally disseminated genes conferring resistance to these drugs. --author-supplied descriptio
Quinolone resistance in Escherichia coli from Accra, Ghana
<p>Abstract</p> <p>Background</p> <p>Antimicrobial resistance is under-documented and commensal <it>Escherichia coli </it>can be used as indicator organisms to study the resistance in the community. We sought to determine the prevalence of resistance to broad-spectrum antimicrobials with particular focus on the quinolones, which have recently been introduced in parts of Africa, including Ghana.</p> <p>Results</p> <p>Forty (13.7%) of 293 <it>E. coli </it>isolates evaluated were nalidixic acid-resistant. Thirteen (52%) of 2006 and 2007 isolates and 10 (66.7%) of 2008 isolates were also resistant to ciprofloxacin. All but one of the quinolone-resistant isolates were resistant to three or more other antimicrobial classes. Sequencing the quinolone-resistance determining regions of <it>gyrA </it>and <it>parC</it>, which encode quinolone targets, revealed that 28 quinolone-resistant <it>E. coli </it>harboured a substitution at position 83 of the <it>gyrA </it>gene product and 20 of these isolates had other <it>gyrA </it>and/or <it>parC </it>substitutions. Horizontally-acquired quinolone-resistance genes <it>qnrB1</it>, <it>qnrB2</it>, <it>qnrS1 </it>or <it>qepA </it>were detected in 12 of the isolates. In spite of considerable overall diversity among <it>E. coli </it>from Ghana, as evaluated by multilocus sequence typing, 15 quinolone-resistant <it>E. coli </it>belonged to sequence type complex 10. Five of these isolates carried <it>qnrS1 </it>alleles.</p> <p>Conclusions</p> <p>Quinolone-resistant <it>E. coli </it>are commonly present in the faecal flora of Accra residents. The isolates have evolved resistance through multiple mechanisms and belong to very few lineages, suggesting clonal expansion. Containment strategies to limit the spread of quinolone-resistant <it>E. coli </it>need to be deployed to conserve quinolone effectiveness and promote alternatives to their use.</p
Sino malaya?: Melodrama and the Integration of Contemporary Social Issues in Philippine Independent Films
Various film critics have written about the dominant themes found in independent films, such as gender and sexuality, culture, and sociopolitical issues. Independent filmmakers have distinctive ways of portraying these issues. Guided by Pathak (2017)’s framework on melodrama, the researchers chose to use melodramatic conventions and techniques to analyze further how these social issues are portrayed in independent films. Findings found that the independent films used melodramatic conventions in portraying social issues. Analyses showed that (1) the films made use of issues such as family relationships and understanding reality, (2) various cinematic elements were applied in the context of melodrama to deliver the film’s message, and (3) setting and physical characteristics were utilized in independent films to display social issues better. This study may be relevant to future research on independent film analysis, the development of national cinema, and the progress of local independent films as a whole
Synthesis, structure, magnetism, and high temperature thermoelectric properties of Ge doped Yb_(14)MnSb_(11)
The Zintl phase Yb_(14)MnSb_(11) was successfully doped with Ge utilizing a tin flux technique. The stoichiometry was determined by microprobe analysis to be Yb_(13.99(14))Mn_(1.05(5))Sb_(10.89(16))Ge_(0.06(3)). This was the maximum amount of Ge that could be incorporated into the structure via flux synthesis regardless of the amount included in the reaction. Single crystal X-ray diffraction could not unambiguously determine the site occupancy for Ge. Bond lengths varied by about 1% or less, compared with the undoped structure, suggesting that the small amount of Ge dopant does not significantly perturb the structure. Differential scanning calorimetry/thermogravimetry (DSC/TG) show that the doped compound's melting point is greater than 1200 K. The electrical resistivity and magnetism are virtually unchanged from the parent material, suggesting that Yb is present as Yb^(2+) and that the Ge dopant has little effect on the magnetic structure. At 900 K the resistivity and Seebeck coefficient decrease resulting in a zT of 0.45 at 1100 K, significantly lower than the undoped compound
Regional Dissemination of a Trimethoprim-Resistance Gene Cassette via a Successful Transposable Element
Antimicrobial resistance is a growing international problem. We observed a 50% increase in the prevalence of trimethoprim resistance among fecal Escherichia coli from healthy Nigerian students between 1998 and 2005, a trend to increase that continued in 2009.A PCR-based screen revealed that 131 (43.1%) of isolates obtained in Nigeria in 2005 and 2009 carried integron-borne dfrA cassettes. In the case of 67 (51.1%) of these isolates, the cassette was a class 1-integron-borne dfrA7 gene, which has been reported at high prevalence from E. coli isolates from other parts of Africa. Complete sequencing of a 27 Kb dfrA7-bearing plasmid from one isolate located the dfrA7 gene within a Tn21-type transposon. The transposon also contained an IS26-derived bla/sul/str element, encoding resistance to β-lactams, sulphonamides and streptomycin, and mercury resistance genes. Although the plasmid backbone was only found in 12 (5.8%) of trimethoprim-resistant isolates, dfrA7 and other transposon-borne genes were detected in 14 (16.3%) and 32 (26.3%) of trimethoprim resistant isolates collected in Nigeria in 2005 and 2009, respectively. Additionally, 37 (19.3%) of trimethoprim-resistant E. coli isolates collected between 2006 and 2008 from Ghana were positive for the dfrA7 and a transposon marker, but only 4 (2.1%) harbored the plasmid backbone.Our data point to transposition as a principal mechanism for disseminating dfrA7 among E. coli from Nigeria and Ghana. On-going intensive use of the affordable broad-spectrum antibacterials is likely to promote selective success of a highly prevalent transposable element in West Africa
Optimisation of age at first calving in Karan Fries cattle
The study was conducted on the performance records of age at first calving (AFC) spread over a period of 15 years on Karan Fries crossbred cattle maintained at Livestock Research Centre. Data of 676 cows were collected and analysed by Least Squares Technique to examine the effect of non-genetic factors on age at first calving. Period of birth was classified into 5 periods (I-V) and season of calving into 4 seasons (winter, summer, rainy and autumn) to see the effect of non-genetic factors on age at first calving. Effect of period of birth was significant on age at first calving while season of calving showed non-significant effect on age at first calving. The overall least squares mean of age at first calving was 1043.40±6.64 days. For the optimisation of age at first calving with regard to milk productivity, analysis was carried out by class interval method. Age at first calving was classified into 7 classes and its average means of milk yield were obtained by using Least Squares Technique where optimum level of age at first calving was obtained at 885–1100 days based on higher milk yield and numbers of animal observed in different classes. From the study, it was concluded that optimum age at first calving could be achieved through proper nutrition and management practices. However, to determine the optimum level of age at first calving, much emphasis should be given to maximum profit rather than maximizing milk production
Polybrominated Diphenyl Ethers (PBDEs) as Emerging Environmental Pollutants: Advances in Sample Preparation and Detection Techniques
Environmental pollution has been a challenging phenomenon in most developing countries, due to the weak enforcement of environmental regulations. As a result, humans and animals are exposed to different environmental pollutants, which threaten their very existence. Some of the emerging pollutants of great concern are polybrominated diphenyl ethers (PBDEs) since they are categorized as probable human carcinogens and are also known to bioaccumulate in fatty tissues of animals and humans, reaching toxic levels upon continued exposure. Monitoring of these pollutants is therefore paramount as it contributes to addressing the problem of human exposure and environmental pollution. Their monitoring involves sample preparation methods followed by quantification with various detection techniques. Sample preparation methods that aim at reducing matrix interferences, enriching analytes and transfer of analytes to a desirable solvent, have evolved from conventional methods to advanced methods that facilitate the detection of these chemicals at very low concentrations. Likewise, detection techniques have advanced from chromatographic detection techniques to miniaturized systems that involve sensors. This chapter discusses PBDEs as emerging pollutants, their sources, and toxicological implications on humans, as well as advances in sample preparation methods and detection techniques in the determination of PBDEs
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