In-plane thermoelectric properties of graphene/xBN/graphene van der Waals heterostructures.

2D materials have attracted broad attention from researchers for their unique electronic properties, which may be been further enhanced by combining 2D layers into vertically stacked van der Waals heterostructures (vdWHs). Among the superlative properties of 2D systems, thermoelectric (TE) energy conversion promises to enable targeted energy conversion, localized thermal management, and thermal sensing. However, TE conversion efficiency remains limited by the inherent tradeoff between conductivity and thermopower. In this paper, we use first-principles calculation to study graphene-based vdWHs composed of graphene layers and hexagonal boron nitride (h-BN). We compute the electronic band structures of heterostructured systems using Quantum Espresso and their TE properties using BoltzTrap2. Our results have shown that stacking layers of these 2D materials opens a bandgap, increasing it with the number of h-BN interlayers, which significantly improves the power factor (PF). We predict a PF of ∼1.0 × 1011W K-2m s for the vdWHs, nearly double compared to 5 × 1010W K-2m s that we obtained for single-layer graphene. This study gives important information on the effect of stacking layers of 2D materials and points toward new avenues to optimize the TE properties of vdWHs.

Hydrochemical characteristics and quality assessment of groundwater from fractured Albian carbonaceous shale aquifers around Enyigba-Ameri, southeastern Nigeria.

Enyigba-Ameri area is known for its Pb-Zn mining activities and the mine water is usually discharged directly into nearby streams and surface runoff. In order to determine the impacts of mining activities on the quality of water in the area and the general hydrochemical characteristics, field measurements and laboratory tests were carried out on water samples collected from the area. Field measurements and laboratory analyses of physicochemical parameters were determined using standard methods. In addition to the multivariate analyses (principal component analysis and cluster analysis) and ANOVA analysis, ionic cross-plots were used to determine the groundwater physicochemical characteristics and geochemical evolution. From the results, it was observed that Pb4+, Zn2+, Fe2 + & 3+, Ca2+, Mg2+, and K+ had a concentration higher than the stipulated guideline values. Three principal components which explained 87.42% of the total dataset were extracted through the data reduction process. Cluster analysis of the hydrochemical data grouped the water samples into three distinct classes. It was observed that the water chemistry is mainly affected by silicate minerals weathering, carbonate weathering, and base ion exchange processes in descending order. ANOVA analysis showed that Zn2+, Fe2 + & 3+, and Mg2+ had mean values that significantly differed from each other based on the sources of the samples. The Wilcox diagram revealed 4 classes of irrigation water types and the irrigation water quality indices showed that the groundwater in the area is not generally suitable for irrigation purposes.

In vitro control of parasitic nematodes of small ruminants using some plant species containing flavonoids.

This study determined in vitro anthelmintic efficacy of three plant species: Trema orientalis, Urtica dioica and Zanthozylum capense on nematode larvae of small ruminants. Dried leaf samples (40 g) were extracted in 70% ethanol, in portions of 10 g and concentrated to 100 ml. Half and one quarter of the original crude extract were both made to 100 ml. Rectal faecal material from 10 Merino sheep and 25 Nguni goats was pooled within species and thoroughly hand-mixed. Dung samples, each of 5 g were cultured for 12 days at 27 °C. On day 13, 4 plates were watered and 4 others treated with ethanol to correct for solvent effect on mortality. The design was 2 (animal species) × 3 (plant species) × 3 (extract concentrations). In each of three runs, three plates were treated with each crude extract in three incremental concentrations. Surviving L3 larvae were isolated, counted and mortalities became indices of anthelmintic efficacy. Data from nematode larval mortality were analysed to determine the effect of animal species, plant species, concentration and their interactions. Efficacy was affected by concentration (P = 0.0001), animal species (P = 0.0046), plant species (P = 0.0572), the interactions of animal species and concentration (P = 0.0010), plant species and concentration (P = 0.0123) and concentration × animal × plant species (P = 0.0435).

The buffalo co-infection conundrum.

Parasitic worms modulate host immunity, affecting co-infection with Mycobacterium bovis (BTB). Ezenwa and Jolles suggested that anthelmintic treatment reduced BTB-induced mortality, but increased BTB spread. Reduced mortality should be weighed against the risk of increasing pathogen spread when adopting this strategy for human treatment of Mycobacterium tuberculosis, BTB, and HIV.

Genetic diversity and relatedness of uropathogenic Escherichia Coli with non-clinical isolates in Grenada

OBJECTIVE: To compare genetic profiles of uropathogenic E.coli (UPEC) to strains isolated from freshwater, seawater and iguanas in Grenada. DESIGN AND METHODS: Eighty-five E. coli strains were isolated using double streak-plating on eosin methylene blue (EMB) and MacConkey agar from human urine, iguanas, fresh and marine water. Species identification was confirmed using API20E. Genomic DNA was extracted from individual pure cultures of E. coli and amplified using the oligonucleotide (GTG5) and BOX primers. The DNA fingerprints were separated by electrophoresis, normalized using reference American Test Culture collection (ATCC) E.coli and compared using DendroUPGMA, the FigTree™, dominance and co-clustering analyses. RESULTS: Both DNA fingerprinting methods targeted extragenic DNA and demonstrated enormous intra-species diversity within the population of studied 85 E. coli isolated from four major eco-habitats. DNA fingerprinting based on BOX-PCR was less discriminating than the (GTG)5-PCR. The BOX analysis correlated better with the ecotype distribution. The combination of dominance and co-clustering analyses allowed us to trace the relatedness of strains among and between the four different ecotypes. CONCLUSIONS: The (GTG5) PCR based co-clustering analysis indicated that the clinical isolates had a closer relationship to iguana E. coli isolates than to fresh and marine water isolates. However, in accordance with the BOX analysis, clinical isolates were most similar to marine, followed by freshwater and iguanas.

Prevalence, serovars and antimicrobial susceptibility of Salmonella spp. from wild and domestic green iguanas (Iguana iguana) in Grenada, West Indies.

Cloacal swabs from 62 green iguanas (Iguana iguana), including 47 wild and 15 domestic ones from five parishes of Grenada, were sampled during a 4-month period of January to April 2013 and examined by enrichment and selective culture for the presence of Salmonella spp. Fifty-five per cent of the animals were positive, and eight serovars of Salmonella were isolated. The most common serovar was Rubislaw (58.8%), a serovar found recently in many cane toads in Grenada, followed by Oranienburg (14.7%), a serovar that has been causing serious human disease outbreaks in Japan. Serovar IV:48:g,z51 :- (formerly, S. Marina) highly invasive and known for serious infections in children in the United States, constituted 11.8% of the isolates, all of them being from domestic green iguanas. Salmonella Newport, a serovar recently found in a blue land crab in Grenada, comprised 11.8% of the isolates from the green iguanas. The remaining four less frequent serovars included S. Javiana and S. Glostrup. Antimicrobial susceptibility tests conducted by a disc diffusion method against amoxicillin-clavulanic acid, ampicillin, cefotaxime, ceftazidime, ciprofloxacin, enrofloxacin, gentamicin, nalidixic acid, streptomycin, tetracycline and trimethoprim-sulfamethoxazole showed that drug resistance is minimal, with intermediate susceptibility, mainly to streptomycin, tetracycline and cefotaxime. This is the first report of isolation and antimicrobial susceptibilities of various Salmonella serovars from wild and domestic green iguanas in Grenada, West Indies.

Striatal volume increases in active methamphetamine-dependent individuals and correlation with cognitive performance.

The effect of methamphetamine (MA) dependence on the structure of the human brain has not been extensively studied, especially in active users. Previous studies reported cortical deficits and striatal gains in grey matter (GM) volume of abstinent MA abusers compared with control participants. This study aimed to investigate structural GM changes in the brains of 17 active MA-dependent participants compared with 20 control participants aged 18-46 years using voxel-based morphometry and region of interest volumetric analysis of structural magnetic resonance imaging data, and whether these changes might be associated with cognitive performance. Significant volume increases were observed in the right and left putamen and left nucleus accumbens of MA-dependent compared to control participants. The volumetric gain in the right putamen remained significant after Bonferroni correction, and was inversely correlated with the number of errors (standardised z-scores) on the Go/No-go task. MA-dependent participants exhibited cortical GM deficits in the left superior frontal and precentral gyri in comparison to control participants, although these findings did not survive correction for multiple comparisons. In conclusion, consistent with findings from previous studies of abstinent users, active chronic MA-dependent participants showed significant striatal enlargement which was associated with improved performance on the Go/No-go, a cognitive task of response inhibition and impulsivity. Striatal enlargement may reflect the involvement of neurotrophic effects, inflammation or microgliosis. However, since it was associated with improved cognitive function, it is likely to reflect a compensatory response to MA-induced neurotoxicity in the striatum, in order to maintain cognitive function. Follow-up studies are recommended to ascertain whether this effect continues to be present following abstinence. Several factors may have contributed to the lack of more substantial cortical and subcortical GM changes amongst MA-dependent participants, including variability in MA exposure variables and difference in abstinence status from previous studies.

Medical management of premenstrual syndrome.

Premenstrual syndrome (PMS) is characterized by a wide variety of symptoms occurring over several days before menstruation. In the differential diagnosis, family physicians should consider other conditions such as chronic yeast infection, allergy, stress, hypoglycemia and primary dysmenorrhea. Each patient should complete a daily menstrual diary for two to three monthly cycles. This diary may help the physician to determine the cyclical nature of PMS and specific symptoms. For most PMS sufferers, initial treatment involves the physician's acknowledgement of the problem and advice about lifestyle, dietary modification and vitamin supplements (e.g., pyridoxine). Seven steps are recommended to assist the family physician in the practical office management of most women with PMS. The potential role of progesterone and other agents in the treatment of PMS is described. Referral to a psychiatrist or psychologist, or the use of drugs such as lithium, danazol or bromocriptine may be required for women suffering from severe PMS.