Organic Glasses: A New Class of Photorefractive Materials

The performance of amorphous organic photorefractive (PR) materials in applications such as optical data storage is generally limited by the concentration of active molecules (chromophores) that can be incorporated into the host without forming a crystalline material with poor optical quality. In polymeric PR systems described previously, performance has been limited by the necessity of devoting a large fraction of the material to inert polymer and plasticizing components in order to ensure compositional stability. A new class of organic PR materials composed of multifunctional glass-forming organic chromophores is described that have long-term stability and greatly improved PR properties.     

The Origin of the Great Bend of the Nile from SIR-C/X-SAR Imagery

The course of the Nile in northern Sudan follows a contorted path through Precambrian bedrock. Radar imagery shows that basement structures control the river's course in this region. Northward-flowing segments follow Precambrian fabrics, whereas east-west segments follow faults of much younger age. These faults may reflect recent uplift of the Nubian Swell and deflection of the river to the southwest to form the great bend of the Nile.     

Convergent domestication of cereal crops by independent mutations at corresponding genetic Loci

Independent domestication of sorghum, rice, and maize involved convergent selection for large seeds, reduced disarticulation of the mature inflorescence, and daylength-insensitive flowering. These similar phenotypes are largely determined by a small number of quantitative trait loci (QTLs) that correspond closely in the three taxa. The correspondence of these QTLs transcends 65 million years of reproductive isolation. This finding supports models of quantitative inheritance that invoke relatively few genes, obviates difficulties in map-based cloning of QTLs, and impels the comparative mapping of complex pheno-types across large evolutionary distances, such as those that separate humans from rodents and domesticated mammals.     

Significance for exercise capacity of some electrocardiographic findings in racehorses

Summary Various cardiorespiratory and metabolic indices were assessed during treadmill exercise in Thoroughbred and Standardbred racehorses with T wave changes in 4 or more leads on the electrocardiogram or second-degree atrio-ventricular (AV) block, and in horses that had no abnormalities on clinical examination, resting electrocardiography or upper respiratory tract endoscopy. No significant differences in heart rate, plasma lactate concentration, arterial blood gases, oxygen uptake, run time, peak velocity, or blood and red cell volumes were found between normal horses and horses with T wave changes or second-degree AV block. These results indicate that some electrocardiographic findings that are considered by some clinicians to indicate cardiac dysfunction, may have little effect on exercise capacity.     

Use of a hospital database for the evaluation of clinical biochemistry results

A database of the clinical chemistry results from unwell animals referred to Glasgow University Veterinary School, by general practitioners, was studied. This database contains over 60,000 records, from more than 25,000 animals, obtained over a period of 18 years. A four-year period was selected during which the instruments and methods used for these analyses were unchanged. The biochemical analyses made on plasma from those dogs when first presented to the veterinary school were scrutinised in detail. These data have been summarised in a tabular form using the first, fifth, 10th, 25th, 50th, 75th, 90th, 95th and 99th percentiles. The distributions of these values differ for different analytes and in particular do not conform to a normal curve. These data can be used to provide estimates of rarity to indicate the frequency with which extreme values associated with disease can be expected. Thus an individual datum can be flagged as high*, high**, high***, or high**** depending on whether it lies in the top 25 per cent, top 10 per cent, top 5 per cent or top 1 per cent, respectively, of cases in the hospital database. Low values can be flagged in the same way. This approach can complement the use of reference ranges from healthy animals to aid the interpretation of clinical biochemistry results from a new patient.