"Coulomb Staircase" at Room Temperature in a Self-Assembled Molecular Nanostructure

Double-ended aryl dithiols [alpha,alpha'-xylyldithiol (XYL) and 4,4'-biphenyldithiol] formed self-assembled monolayers (SAMs) on gold(111) substrates and were used to tether nanometer-sized gold clusters deposited from a cluster beam. An ultrahigh-vacuum scanning tunneling microscope was used to image these nanostructures and to measure their current-voltage characteristics as a function of the separation between the probe tip and the metal cluster. At room temperature, when the tip was positioned over a cluster bonded to the XYL SAM, the current-voltage data showed "Coulomb staircase" behavior. These data are in good agreement with semiclassical predictions for correlated single-electron tunneling and permit estimation of the electrical resistance of a single XYL molecule (approximately18 ± 12 megohms).     

Retrospective study of neurological signs and management of seven English horses with temporohyoid osteoarthropathy

This retrospective study summarises the case details, presenting signs, management and outcome in cases of temporohyoid osteoarthropathy (THO) and describes the findings of diagnostic imaging modalities. The condition appears to be relatively rare in Europe and the objective of this study is to make clinicians aware that THO can have a range of various neurological and clinical presentations. The records of 2 referral equine practices in England were reviewed and 7 horses with THO diagnosed on guttural pouch endoscopy indentified. The clinical and neurological signs, diagnostic procedures, treatment and outcomes were reviewed. Although small, this group is the largest case series of THO from Europe. One horse was a yearling, whereas THO is generally considered usually to affect middle aged and older horses. Computed tomography was used to confirm the diagnosis and demonstrated stylohyoid bone fractures in 2 cases while there was mild increased radionuclide uptake in one of 2 cases undergoing nuclear scintigraphy. Treatment is still controversial, although ceratohyoidectomy led to complete resolution of signs in 2 of 5 cases thus treated and improvement in the other 3. One horse with mild signs treated with antimicrobials and nonsteroidal anti‐inflammatory drugs made a full recovery while another, presented with head shaking and managed with a phased exercise programme, improved but did not resolve completely.     

Longevity of Mycobacterium bovis in brushtail possum (Trichosurus vulpecula) carcasses,and contact rates between possums and carcasses

Abstract

AIM: To determine, for a variety of environmental conditions, how long Mycobacterium bovis might remain viable inside the carcass of a brushtail possum (Trichosurus vulpecula) that died of bovine tuberculosis (Tb), and to measure the rate of contact between free-ranging possums and possum carcasses.

METHODS: Lesions of M. bovis were simulated by inoculating excised spleens weighing 0.5–1 g with 0.2 mL liquid culture containing approximately 5 x 10⁷ cfu M. bovis/mL. Simulated lesions were inserted into possum carcasses (n=48) at the peripheral lymph nodes. Carcasses were placed in the field at two sites (a tussock grassland and a podocarp-broadleaved forest site) and in two seasons (summer and winter) for up to 62 days. Survival rates of M. bovis were estimated by sampling the simulated lesions over time, and culturing the recovered lesion to determine if any viable M. bovis bacteria were present.

The time taken for a free-ranging possum to first encounter a dead possum in its home range was estimated by live-trapping possums and fitting them with proximity loggers (n=13). A ‘contact’ was recorded if these possums came within 40–50 cm of proximity loggers fitted to possum carcasses.

RESULTS: There were strong seasonal and site effects in the survival rate of M. bovis in possum carcasses. In the grassland habitat, no viable bacilli were cultured from any carcass after 3 days in summer, whereas in winter all samples were culture-positive for the first 20 days, and some were still positive after 27 days. The survival rates for forest habitat were intermediate between the results for grassland, and there were no culture-positive carcasses after 9 days in summer or 27 days in winter.

In summer, infected carcasses (n=6) were first encountered by possums a mean 1.9 (range 0.4–6.7) days after placement.

CONCLUSIONS: Possum carcasses were contacted by free-ranging possums within the period that viable M. bovis were shown to survive in a carcass. The risk of such infection is likely to be most significant in winter or in areas with microhabitats where the survival of M. bovis is high. However, the generally low survival rate of M. bovis in possum carcasses and the low frequency of possum-to-carcass contacts indicate this route of transmission alone could not maintain Tb in a possum population.     

A Case of Successful Pregnancy in a Ewe with Uterus Didelphys

Uterus didelphys is a rare congenital abnormality of the reproductive tract. Although it occurs in various species, there are no published reports describing pregnancy outcome in association with this abnormality. Herein we describe a case of successful unilateral singleton pregnancy in a ewe incidentally found to have uterus didelphys during the course of a biomedical research study. The pregnancy was established using assisted reproductive techniques and interrupted in late gestation, at which point the abnormality was identified. Serial ultrasound assessment of foetal biometry revealed a normal foetal growth trajectory. Despite a 45% reduction in placentome number, total placentome weight was near normal secondary to compensatory placentome growth and development. To our knowledge, this is the first detailed report of normal foetal growth in an animal with uterus didelphys and illustrates the ability of the ovine placenta to adapt to a reduced number of placentomes and maintain foetal nutrient supply.     

Pleistocene collapse of the west antarctic ice sheet

Some glacial sediment samples recovered from beneath the West Antarctic ice sheet at ice stream B contain Quaternary diatoms and up to 10(8) atoms of beryllium-10 per gram. Other samples contain no Quaternary diatoms and only background levels of beryllium-10 (less than 10(6) atoms per gram). The occurrence of young diatoms and high concentrations of beryllium-10 beneath grounded ice indicates that the Ross Embayment was an open marine environment after a late Pleistocene collapse of the marine ice sheet.     

Effects of organic manure and chemical fertilizer on soil fertility and productivity of plant and ratoon crops of sugarcane

A long-term field experiment was initiated in November, 1967 at Research Area of Department of Soil Science to study the response of nitrogen to pearl millet-wheat cropping system at various doses and modes of farmyard manure application. The soil organic carbon increased with farmyard manure application and ranged from 0.68% in control to 1.82% in the plot receiving the highest annual dose (90 Mg ha^?1) of farmyard manure. To study the contribution of farmyard manure on the productivity of pearl millet and wheat crops, the constants (intercept and slope) were determined between the grain yield of pearl millet and wheat crops with increasing dose of fertilizer nitrogen. Another linear regression was fitted between the intercept of the linear model and the soil organic carbon content. It has been observed that with each unit increase in the soil organic carbon, the productivity of pearl millet increased by 273 kg ha^?1 and that of wheat by 1591 kg ha^?1. The regression between the slope and soil organic carbon was linear in case of pearl millet (R² 0.49) but in case of wheat there was no relationship.     

Kinetics of equine neutrophil elastase release and superoxide anion generation following secretagogue activation: a potential mechanism for antiproteinase inactivation

Man and horses both suffer from neutrophil mediated pulmonary diseases however there are striking species differences in the underlying pathology. In particular while pulmonary emphysema is a common pathological sequel to human respiratory disease it is not a major feature of the common equine neutrophil mediated condition, chronic obstructive pulmonary disease (COPD). The proposed reason for this difference is that equine neutrophils contain less elastase than equivalent human cells and therefore there is a reduced risk of excess and/or uninhibited elastase activity, which is considered the major cause of pulmonary emphysema in man, in the horse lung. In previous studies equine neutrophil elastase (ENE) has been assayed by measuring elastinolytic activity whereas human neutrophil elastase content has been determined using immunological techniques. Neutrophils contain several intracellular protease inhibitors therefore measurement of elastase activity may underestimate the total NE content. The aim of the current study was to develop immunological techniques to allow investigation of the cellular content, distribution and release of ENE from purified equine neutrophils. Equine neutrophil elastase 2A (ENE 2A), the most abundant elastase in equine neutrophils, and equine alpha-1-proteinase inhibitor (API), the main inhibitor of elastase were found to be present at 0.813 pg +/- 0.179 and 0.021 pg +/- 0.003 (mean +/- SEM, n = 11 individual horses) per neutrophil, respectively. This represents twice as much elastase as previously found in the equine neutrophil and a comparable amount to that reported in human neutrophils. Immunolocalisation demonstrated that ENE 2A has a granular distribution within the cytosol of neutrophils, whereas API exhibits a uniform non-granular cytoplasmic appearance. In addition the kinetics of simultaneous generation and release of superoxide anions (SOA) and release of ENE 2A from equine neutrophils, stimulated in vitro by zymosan-activated serum (ZAS) in the presence and absence of the cation chelator ethylene glycol-N,N,N',N'-tetraacetic acid (EGTA), showed a close relationship between total SOA generation and total ENE 2A release during the initial 90 min post-ZAS stimulation and the dependence of both events on extracellular cations. In conclusion these studies have shown that horse and human neutrophil elastase content and mediator release functions are more closely matched than was previously thought. This suggests that the species differences in pathology resulting from neutrophil-mediated respiratory disease are determined by other factors such as differences in the abundance and function of intra- and extra-cellular protease inhibitors.