Asymptomatic embolization in subjects with atrial fibrillation not taking anticoagulants: a prospective study

BACKGROUND AND PURPOSE: Embolism is believed to be the major cause of stroke in patients with nonvalvular atrial fibrillation (NVAF). The detection of asymptomatic embolic signals (ES) in individuals with NVAF might allow identification of patients at high risk of stroke and monitoring of therapy in individual subjects. We determined the frequency of asymptomatic ES in patients with NVAF who were not taking warfarin. METHODS: Bilateral transcranial Doppler recordings were made for 1 hour from the middle cerebral arteries of 111 successive patients with NVAF taking aspirin alone or no antithrombotic or anticoagulant therapy. Adequate recordings could be made in 86 patients. In 79 subjects, recordings were performed on a second occasion to study temporal variability. Recordings for a single hour were also made in 30 age-matched control subjects. RESULTS: ES were detected in 13 (15.1%) of NVAF subjects but in no control subjects (P=0.02). ES were detected both in subjects with symptomatic NVAF (4 of 30 [13.1%], P=0.04 versus controls) and asymptomatic NVAF (9 of 56 [16.1%], P=0.02 versus controls). There was no correlation between the presence of ES and smoking status, diabetes, hypertension, aspirin use, aspirin dose, symptomatic status, left atrial size, left ventricular function, or the presence of left atrial thrombus detected on transthoracic echocardiography. Repeating the recording increased the number of patients with ES to 21 (26.6%). On considering the results of both recordings, again there was no association for either recording between the presence of ES and smoking status, diabetes, hypertension, aspirin use, aspirin dose, age, symptomatic status, left atrial size, or left ventricular function. On repeating the recording, in the symptomatic group only 2 patients (8%) changed status, in contrast to 15 (29%) in the asymptomatic group. CONCLUSIONS: ES can be detected in patients with NVAF at a low frequency. Particularly in asymptomatic patients, ES show marked temporal variability. We found no correlation between the presence of previously reported clinical and echocardiographic markers of increased stroke risk and the presence of ES. This association requires further investigation before the clinical utility of this technique in patients with NVAF is decided.     

Characterisation of thin film silicon films deposited by plasma enhanced chemical vapour deposition at 162 MHz, using a large area, scalable, multi-tile-electrode plasma source

Large area (600 × 720 mm) depositions of hydrogenated microcrystalline silicon (μc-Si:H) have been achieved at high deposition rates using a scalable, multi-tile electrode topology. Depositions have shown local results of μc-Si:H deposited with SiH₄ concentrations of up to 20% and at rates of up to 15 Å/s. Of particular interest for this electrode topology is the material across the inter-tile gap. Here we present measurements of the deposition uniformity across the inter-tile gap as well as the material characteristics of the layers. The behaviour of the crystalline fraction, χ_c is observed using Raman spectroscopy, x-ray diffractometry, and dark/light conductivity measurements. A qualitative interpretation of these results is presented, relating them to depletion of SiH₄ in the plasma.     

Short communication: Preliminary investigation into the effect of freezing and a cryopreservant on the recovery of mastitis pathogens from ewe milk

The objective of this study was to investigate the recovery of bacteria from ewe milk after freezing for 4 or 8 wk with and without the addition of glycerol as a cryopreservant. A total of 50 udder-half milk samples with a known range of bacterial species were selected, stored, and analyzed in 5 treatment groups: time zero; frozen for 4 wk with, and without, glycerol; and frozen for 8 wk with, and without, glycerol. A lower recovery was observed in all bacterial species studied after freezing. Samples containing fewer than 100 cfu/mL came from ewes with a lower somatic cell count and were more likely to be bacteriologically negative after freezing than those above this threshold. The addition of glycerol increased recovery of gram-negative bacteria after freezing, although this requires further study to draw strong conclusions. The effects on gram-positive species were inconsistent. We conclude that although the addition of glycerol had a small beneficial effect on the sensitivity of detection of bacteria from frozen sheep milk, sensitivity was highest in cultures from fresh milk.     

Effects of the electrical stress on the conduction characteristics of metal gate/MgO/InP stacks

The degradation dynamics and post-breakdown current–voltage (I–V) characteristics of magnesium oxide (MgO) layers grown on n and p-type indium phosphide (InP) substrates subjected to electrical stress were investigated. We show that the current–time (I–t) characteristics during degradation can be described by a power-law model I(t) = I₀t^−α, where I₀ and α are constants. It is reported that the leakage current associated with the soft breakdown (SBD) failure mode follows the typical voltage dependence I = aV^b, where a and b are constants, for both injection polarities but in a wider voltage range compared with the SiO₂/Si system. It is also shown that the hard breakdown (HBD) current is remarkably high, involving large ON–OFF fluctuations that resemble the phenomenon of resistive switching previously observed in a wide variety of metal oxides.     

A review of phosphorus partition relations for use in basic oxygen steelmaking

Phosphorus removal in basic oxygen steelmaking is a significant problem for integrated steelmakers. Phosphorus removal is required due to its deleterious effect on the mechanical properties of steel. However, this is progressively becoming more difficult due to the increasing phosphorus content of many iron ores. Many studies have investigated dephosphorisation and published empirical phosphorus partition (L_P) equations for a range of conditions. The structure of these equations has been used to develop a new partition relation that allows the effect of minor slag constituents such as TiO₂, Al₂O₃ and V₂O₅ on steel dephosphorisation to be tested. Al₂O₃ was found to have a weak negative effect on the measured L_P, except at the lower oxygen potential range tested, where a positive correlation was observed. Increasing TiO₂ and V₂O₅ contents were found to decrease the measured L_P; however, these correlations became less prevalent at the higher oxygen potential ranges tested.     

Recent trends in Antarctic snow accumulation from Polar MM5 simulations

Polar MM5, a mesoscale atmospheric model optimized for use over polar ice sheets, is employed to simulate Antarctic accumulation in recent decades. Two sets of simulations, each with different initial and boundary conditions, are evaluated for the 17yr period spanning 1985-2001. The initial and boundary conditions for the two sets of runs are provided by the (i) European Centre for Medium-Range Weather Forecasts 40 year Reanalysis, and (ii) National Centres for Environmental Prediction-Department of Energy Atmospheric Model Intercomparison Project Reanalysis II. This approach is used so that uncertainty can be assessed by comparing the two resulting datasets.There is broad agreement between the two datasets for the annual precipitation trends for 1985-2001. These generally agree with ice core and snow stake accumulation records at various locations around the continent, indicating broad areas of both upward and downward trends. Averaged over the continent the annual trends are small and not statistically different from zero, suggesting that recent Antarctic snowfall changes do not mitigate current sea-level rise. However, this result does not suggest that Antarctica is isolated from the recent climate changes occurring elsewhere on Earth. Rather, these are expressed by strong seasonal and regional precipitation changes.     

A standardized conjugation protocol to asses antibiotic resistance transfer between lactococcal species

Optimal conditions and a standardized method for conjugation between two model lactococcal strains, Lactococcus lactis SH4174 (pAMbeta1-containing, erythromycin resistant donor) and L. lactis Bu2-60 (plasmid-free, erythromycin sensitive recipient), were developed and tested in a inter-laboratory experiments involving five laboratories from different countries. The ultimate goal of the study was to assess the microbial potential of antibiotic resistance transfer among Lactic Acid Bacteria (LAB). The influence of culture age (various OD values) and ratios of donor and recipient cultures as well as filter, solid and liquid mating techniques, were examined in order to optimize the conjugation protocol. In the result of these studies, we concluded that the donor-to-recipient ratio appear to be important; the most efficient technique for conjugation was filter mating and the optimal conditions for gene transfer were observed when late logarithmic cultures of both donor and recipient were used. Comparison of conjugal transfer frequencies between five partner laboratories showed that results are sufficiently intra-laboratory repeatable and inter-laboratory comparable. This is the first study of this kind, in which a standardized protocol of conjugal mating for testing antibiotic resistance dissemination among LAB was established and validated.     

Carbon Transfer in the Lower Zone of a Blast Furnace

In this paper results from an investigation focused on coke/iron reactions occurring in the hearth of a blast furnace, below the slag layer, are presented. In this region, as coke dissolves in the iron there is the potential for a mineral layer to form and persist at the coke/iron interface and inhibit the rate of coke dissolution. Key findings of the investigation include that the composition of the mineral layer was principally composed of oxides of aluminium and calcium, present as various calcium aluminates and that the morphology of the layer profoundly affected the rate of carbon transfer. Follow‐up up studies on the kinetics of carbon transfer focussed on how the wetting and interfacial characteristics of iron on the calcium aluminates would affect iron penetration of the mineral layer are also reported and discussed as was a new material, called coke analogue, that could be used in the study of real industrial coke. Analysis of the wetting behaviour of liquid iron on alumina and the calcium aluminates investigated indicated that iron wetting of the mineral layer was not a key parameter in coke dissolution in iron for the coke composition studied. The brief details given for the coke analogue indicated that it did replicate coke dissolution behaviour in iron, though more experimental work is required to fully understand and exploit the potential of this material.