Radiation dosimeter utilizing the thermoluminescence of lithium fluoride

A dosimeter, with little wavelength dependence and large useful energy range for electromagnetic radiation, which is simple to use and read, has been developed. It appears to have applications in personnel monitoring as well as radiation research.     

Microbiology of soils at opencast coal sites. I. Short-and long-term transformations in stockpiled soils

The microbiology of soils subjected to stripping and stockpiling at opencast mine sites was investigated using a combination of and biomass fumigation plate-count techniques. Mounds varied in age from a few weeks to 11 years, and soils included both mineral and organic variants. Results showed that after an initial stimulation of bacteria, microbial populations declined in stockpiles. Numbers of viable fungal propagules, and to a lesser extent actinomycetes, declined with depth in mounds, particularly below about 1 m, and this trend was accentuated with increased time of storage. However, stockpiled soils were highly variable in terms of microbiological status and displayed considerable lateral as well as vertical heterogeneity.     

Microbiology of soils at opencast coal sites. II. Population transformations occurring following land restoration and the influence of ryegrass/fertilizer amendments

Data from field work and pot experiments gave insight into transformations occurring in soil microbial populations at opencast coal sites during the first year of land restoration. Total bacterial biomass increased markedly immediately following restoration, while pot experiments revealed that this flush was confined to soil stored below 1 m depth in stockpiles, where anaerobic conditions develop. Fungal and actinomycete propagules declined at the outset of restoration, but rallied during the first year, while the bacterial flush subsided. Fungal hyphae, which accounted for 50% of microbial biomass in surface mound and freshly restored soils, accounted for > 99% one year after restoration. Experiments involving fertilizer and ryegrass amendments showed the biomass of restored soil to be limited by carbon, rather than nitrogen or phosphorus.     

The Demise of Distance? The Declining Role of Physical Proximity for Knowledge Transmission

ABSTRACT The transmission of knowledge diminishes with physical distance, one factor explaining the geographic clustering of scientific and industrial activity. The authors investigate how those distances have stretched over time—between collaborating inventors, and between inventors and the technology that inspires them. While physical distance is still a factor, it is clear that its constraining effects have weakened, especially for particular types of innovators, technologies, and regions of the United States.     

Seasonal habitat use by brook trout,Salvelinus fontinalis (Mitchill), in a second-order stream

Abstract Seasonal habitat use by over-yearling and under-yearling brook trout, Salvelinus fontinalis (Mitchill), was examined in a second-order stream in north-central Pennsylvania, USA. The habitat occupied by brook trout and available habitat were determined in a 0.5-km stream reach during the spring, summer and autumn of 1989 and the spring and summer of 1990. Cover, depth, substrate and velocity were quantified from over 2000 observations of individual brook trout. Habitat used by under-yearling brook trout was more uniform between seasons and years than that used by over-yearling brook trout. Over-yearling brook trout occupied areas with more cover and greater depth than did under-yearling brook trout, suggesting ontogenetic shifts in these variables. Differences for velocity and substrate were not as great as those for cover and depth. The selection of areas with low water velocities governed trout habitat use in spring, whereas cover and depth were the most important habitat variables in summer and autumn. Principal component analysis showed that available habitat and trout habitat centroids diverged most in spring, indicating that habitat selection by brook trout may be greatest at this time.     

A more sensitive technique for isolating infectious pancreatic necrosis virus from asymptomatic carrier rainbow trout, Salmo gairdneri Richardson

Abstract. An improved technique for isolating infectious pancreatic necrosis virus (IPNV) is described. It involves trypsinization of the suspect tissue, separation of the trypsinized cells and their co-cultivation with indicator RTG-2 cells. This co-cultivation method is compared with homogenization, followed by membrane filtration, a procedure routinely employed by most disease diagnostic laboratories. From the two IPN-infected farms studied, IPNV could be isolated by homogenization from only 50 and 66%, respectively, of the fish from which virus was detected by co-cultivation. This difference in sensitivity can be explained in two ways, viz: (a) some of the virus is being retained by the membrane filter during filtration to remove contaminants following homogenization; (b) the presence of neutralizing factors in the tissue homogenate are neutralizing the virus and thus no cytopathic effect ensues. No correlation between serum neutralizing antibody levels and the differences in sensitivity of the two methods was found. The co-cultivation method is as practical as, and certainly no more time-consuming than, the homogenization technique.     

64‐MULTIDETECTOR COMPUTED TOMOGRAPHIC ANGIOGRAPHY OF THE CANINE CORONARY ARTERIES

Canine coronary artery angiography (CTA) was performed in four anesthetized healthy dogs using 64‐multidetector computed tomography. Esmolol, a β‐1 adrenergic receptor antagonist, and sodium nitroprusside, an arteriolar and venous dilator, were administered to enhance visualization of the coronary arteries by reducing heart rate and creating vasodilation. The left main coronary artery with its three main branches and the right coronary artery were visualized and subdivided in 13 segments for evaluation. Optimal reconstruction interval, expressed as percentage of the R‐to‐R interval, was determined at 5% in 2.9%, 35% in 1%, 75% in 21.2%, 85% in 43.3%, and 95% in 31.7% of the segments. Overall image quality was good in 41.3% of the segments and excellent in 14.4%. There was blur in 98.1%, motion in 17.3%, and stair step in 6.7% of the evaluated segments, but these artifacts did not interfere with anatomic depiction of the arteries. Cross‐sectional anatomy of the coronary arteries as evaluated from the coronary CTA agreed well with gross anatomic evaluation and published information. The use of esmolol did not lead to the target heart rate of 60–65 beats/min. Nitroprusside had no significant effect on visualized length or diameter of the coronary artery branches. Coronary CTA is useful for the anatomic depiction of coronary artery branches in the dog.     

COMPUTED TOMOGRAPHY OF THE PHARYNX IN A CLOSED VS. OPEN MOUTH POSITION

The pharynx is anatomically complex and evaluation can be difficult even with cross‐sectional imaging. Eight animals had computed tomography (CT) studies of the head performed with the mouth open and closed. The studies were anonymized and evaluated by four radiologists for visibility of six anatomic regions (dorsal wall of nasopharynx, lumen of nasopharynx, dorsal margin of the soft palate, ventral margin of the soft palate, oropharynx, and laryngopharynx) and for certainty of a normal or abnormal diagnosis of four different anatomic regions (nasopharynx, soft palate, oropharynx, and laryngopharynx). Mean visual scores differed significantly between mouth positions and were improved when the mouth was open. The ability of radiologists to classify anatomic regions as normal or abnormal vs. unsure also varied between mouth positions, and there was greater uncertainty when the mouth was closed. In addition, estimated volume of the air‐filled nasopharynx differed significantly as a function of mouth position and was greater when the mouth was open (mean=1.187 cm³, SE=0.177) vs. closed (mean=0.584 cm³, SE=0.116). Computed tomographic evaluation of the pharynx can be improved with the mouth open.