External electric field effect on electron transport in carbon nanotubes

Electronic transport properties of carbon nanotubes are studied theoretically in the presence of external electric field E(t) by using the Boltzmann's transport with constant relaxation time. An analytical expression for the current densities of the nanotubes are obtained. It is observed that the current density-electric field characteristics of the CNs exhibit total self-induced transparency and absolute negative conductivityComment: 5 pages, 2 figure

Evaluation of susceptibility of some elite cowpea cultivars to attack by Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)

Fifteen elite cowpea cultivars were evaluated for their susceptibility to attack and damage by the most destructive storage pest, Callosobruchus maculatus (F.), based on the number of eggs laid, total developmental time, percentage adult emergence, seed weight loss, and growth index. Significantly, more eggs were laid on the seeds of Bengpla, California and Clemson genotypes than on those of the other cultivars. The mean developmental time (days) of C. maculatus ranged from 21.4 days on California 20 to 25.7 days on Sul 518-2 (Marfo tuya), and was significantly different between the cowpea cultivars. Adult emergence was considerably high on Bengpla, California and Clemson genotypes, but low on IT94K-445-2, Melack, and Sul 518-2. Weight loss ranged from 7 to 35.6 per cent and was significantly different between cultivars. The IT94K-445-2, IT98K-279-3 and Valenga cultivars had the least damage whilst California 11, IT87KD-1951 and Bengpla had the highest loss in seed weight. Overall, the susceptibility indices which ranged from 4.8 to 9.4 indicated that IT94K-445-2, Melack, Sul 518-2 and IT98K-279-3 were the least susceptible, whereas Bengpla, California and Clemson were the most susceptible cultivars. Therefore, it is recommended that IT94K-445-2, Sul 518-2, Melack, and IT98K-279-3 that have some degree of resistance to C. maculatus in this study should either be promoted or incorporated into breeding programmes because this will help to considerably reduce storage losses that farmers incur. Quinze variétés de dolique élite étaient évaluées pour leurs prédispositions à l'attaque et au ravage par le ravageur de stockage le plus destructeur, Callosobruchus maculatus (F.) fondées sur les variables suivantes; la quantité d'oeufs pondus, la totalité de temps de croissance, le pourcentage d'émergence en adultes, la perte de poids de graine et l'indice de croissance. Considérablement, plus des oeufs étaient pondus sur les graines de génotypes de Bengpla, de Californie et de Clemson que sur les autres variétés. Le temps (jours) moyen de croissance de C. maculatus variait de 21.4 jours sur Californie 20 à 25.7 jours sur Sul 518-2 (Marfo tuya) et était considérablement différent entre les variétés de dolique. Emergence en adultes était considérablement élevée sur les génotypes de Bengpla, de Californie et de Clemson et faible sur 1T94K-445-2, Melack et Sul 518- 2. La perte de poids variait entre 7% et 35.6% et était considérablement différente entre les variétés. 1T94K- 445-2, IT98K-279-3 et Valenga ont subi le moindre ravage alors que Californie 11, IT87KD-1951 et Bengpla avaient les pertes de poids de graine les plus élevées. D'ensemble, les indices de prédisposition qui variaient de 4.8 à 9.4 indiquent que 1T94K-445-2, Melack, Sul 518, 1T98K- 279-3 étaient les moindres prédisposées alors que Bengpla, Californie et Clemson étaient les variétés les plus prédisposées. Il est donc recommandé que 1T94K-445- 2, Sul 518-2, Melack et 1T98K-279-3 qui avaient une certaine mesure de résistance à C. maculatus dans l'étude actuelle, devraient être soit encouragés soit incorporés dans les programmes de reproduction puisque cela va aider à réduire considérablement les pertes de stockage que les agriculteurs subissent. Ghana Journal of Agricultural Science Vol. 40 (1) 2007: pp. 73-8

Anti-inflammatory and antioxidant properties of the root extract of Carissa edulis (forsk.) Vahl (apocynaceae)

Root extracts of Carissa edulis (Forsk.) Vahl (Apocynaceae) are used for the treatment several pathological states including inflammatory disorders. The present study was undertaken to evaluate the effect of an alcoholic extract of C. edulis (CEE) on carrageenan-induced foot oedema in chicks. Also since free radicals and reactive oxygen species are implicated in inflammatory diseases, the anti-oxidant potential of extract was investigated in in vitro experimental models. Oral administration of CEE (30- 300 mg kg-1 p.o.) significantly inhibited carrageenan-induced foot oedemas with a maximal inhibition of 53.8±8.2%. Similarly, the NSAID diclofenac (10-100 mg kg-1, i.p.) and the steroidal anti-inflammatory agent dexamethasone (0.3-3 mg kg-1, i.p ) reduced the total oedema with a maximal inhibition of 62.7±9.1% and 66.4±7.8% respectively. The extract also scavenged DPPH and prevented lipid peroxidation in rat brain homogenates. These results suggest that alcoholic extract of C. edulis exerts in vivo antiinflammatory activity after oral administration and also has antioxidant properties which may contribute to its activity.Journal of Science & Technology (Ghana) Vol. 27 (2) 2007: pp. 6-1

Enhancement of the aerosol direct radiative effect by semi-volatile aerosol components: airborne measurements in North-Western Europe

A case study of atmospheric aerosol measurements exploring the impact of the vertical distribution of aerosol chemical composition upon the radiative budget in North-Western Europe is presented. Sub-micron aerosol chemical composition was measured by an Aerodyne Aerosol Mass Spectrometer (AMS) on both an airborne platform and a ground-based site at Cabauw in the Netherlands. The examined period in May 2008 was characterised by enhanced pollution loadings in North-Western Europe and was dominated by ammonium nitrate and Organic Matter (OM). Both ammonium nitrate and OM were observed to increase with altitude in the atmospheric boundary layer. This is primarily attributed to partitioning of semi-volatile gas phase species to the particle phase at reduced temperature and enhanced relative humidity. Increased ammonium nitrate concentrations in particular were found to strongly increase the ambient scattering potential of the aerosol burden, which was a consequence of the large amount of associated water as well as the enhanced mass. During particularly polluted conditions, increases in aerosol optical depth of 50–100% were estimated to occur due to the observed increase in secondary aerosol mass and associated water uptake. Furthermore, the single scattering albedo was also shown to increase with height in the boundary layer. These enhancements combined to increase the negative direct aerosol radiative forcing by close to a factor of two at the median percentile level. Such increases have major ramifications for regional climate predictions as semi-volatile components are often not included in aerosol models. The results presented here provide an ideal opportunity to test regional and global representations of both the aerosol vertical distribution and subsequent impacts in North-Western Europe. North-Western Europe can be viewed as an analogue for the possible future air quality over other polluted regions of the Northern Hemisphere, where substantial reductions in sulphur dioxide emissions have yet to occur. Anticipated reductions in sulphur dioxide in polluted regions will result in an increase in the availability of ammonia to form ammonium nitrate as opposed to ammonium sulphate. This will be most important where intensive agricultural practises occur. Our observations over North-Western Europe, a region where sulphur dioxide emissions have already been reduced, indicate that failure to include the semi-volatile behaviour of ammonium nitrate will result in significant errors in predicted aerosol direct radiative forcing. Such errors will be particularly significant on regional scales

Human Adipose Tissue-Derived Mesenchymal Stem Cells Abrogate Plasmablast Formation and Induce Regulatory B Cells Independently of T Helper Cells

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Secondary bacterial infections of buruli ulcer lesions before and after chemotherapy with streptomycin and rifampicin

Buruli ulcer (BU), caused by Mycobacterium ulcerans is a chronic necrotizing skin disease. It usually starts with a subcutaneous nodule or plaque containing large clusters of extracellular acid-fast bacilli. Surrounding tissue is destroyed by the cytotoxic macrolide toxin mycolactone produced by microcolonies of M. ulcerans. Skin covering the destroyed subcutaneous fat and soft tissue may eventually break down leading to the formation of large ulcers that progress, if untreated, over months and years. Here we have analyzed the bacterial flora of BU lesions of three different groups of patients before, during and after daily treatment with streptomycin and rifampicin for eight weeks (SR8) and determined drug resistance of the bacteria isolated from the lesions. Before SR8 treatment, more than 60% of the examined BU lesions were infected with other bacteria, with Staphylococcus aureus and Pseudomonas aeruginosa being the most prominent ones. During treatment, 65% of all lesions were still infected, mainly with P. aeruginosa. After completion of SR8 treatment, still more than 75% of lesions clinically suspected to be infected were microbiologically confirmed as infected, mainly with P. aeruginosa or Proteus miriabilis. Drug susceptibility tests revealed especially for S. aureus a high frequency of resistance to the first line drugs used in Ghana. Our results show that secondary infection of BU lesions is common. This could lead to delayed healing and should therefore be further investigated

National trends in total cholesterol obscure heterogeneous changes in HDL and non-HDL cholesterol and total-to-HDL cholesterol ratio: a pooled analysis of 458 population-based studies in Asian and Western countries

Background Although high-density lipoprotein (HDL) and non-HDL cholesterol have opposite associations with coronary heart disease, multi-country reports of lipid trends only use total cholesterol (TC). Our aim was to compare trends in total, HDL and non-HDL cholesterol and the total-to-HDL cholesterol ratio in Asian and Western countries. Methods We pooled 458 population-based studies with 82.1 million participants in 23 Asian and Western countries. We estimated changes in mean total, HDL and non-HDL cholesterol and mean total-to-HDL cholesterol ratio by country, sex and age group. Results Since ∼1980, mean TC increased in Asian countries. In Japan and South Korea, the TC rise was due to rising HDL cholesterol, which increased by up to 0.17 mmol/L per decade in Japanese women; in China, it was due to rising non-HDL cholesterol. TC declined in Western countries, except in Polish men. The decline was largest in Finland and Norway, at ∼0.4 mmol/L per decade. The decline in TC in most Western countries was the net effect of an increase in HDL cholesterol and a decline in non-HDL cholesterol, with the HDL cholesterol increase largest in New Zealand and Switzerland. Mean total-to-HDL cholesterol ratio declined in Japan, South Korea and most Western countries, by as much as ∼0.7 per decade in Swiss men (equivalent to ∼26% decline in coronary heart disease risk per decade). The ratio increased in China. Conclusions HDL cholesterol has risen and the total-to-HDL cholesterol ratio has declined in many Western countries, Japan and South Korea, with only a weak correlation with changes in TC or non-HDL cholesterol