Gas leak detector is simple and inexpensive

Pressure sensor monitors small gas leaks in piping and pressure vessels. A combination of a paper ribbon and adhesive plastic tape is used to cover the area to be monitored and the pressure sensor is placed over a hole in the tape and paper

Rotary-knife stripper facilitates removal of X-ray film from pack

Rotary-knife stripper facilitates removal of X ray film from the daylight pack paper sleeve. The new stripper is rectangular, approximately 4 inches wide, 5 inches high, and 7 inches long

A fluorometric method for the estimation of tryptophan

The various colorimetric methods now employed for the estimation of tryptophan are not specific for tryptophan but give colored products with many compounds containing the indole nucleus, including indole itself. In order to facilitate studies of the enzymatic synthesis of tryptophan from indole and serine by extracts of Neurospora (1), a search for a rapid, quantitative method for the estimation of tryptophan in the presence of indole was undertaken. Tauber (2) reported that tryptophan gives a green fluorescence when treated with 70 to 72 per cent perchloric acid at room temperature. Modification of this procedure has led to a method for the rapid estimation of tryptophan, without preliminary extraction of indole, in hydrolyzed or unhydrolyzed tryptophan-containing materials

The b iosynthesis of histidine: imidazoleglycerol phosphate, imidazoleacteol phosphate, and histidinol phosphate

This is a report on the isolation and characterization of D-erythro-imidazoleglycerol phosphate (IGP), imidazoleacetol phosphate (IAP), and L-histidinol phosphate, which are accumulated in the mycelia of several of these mutants

Extraction Methods and an Investigation of Drosophila Lipids

In earlier work (8) we extracted lipids from dried, macerated Drosophila melanogaster with ether, but later, working with larger quantities of undried flies, we found that most of the phospholipids were autolyzed. Kates' studies (2) led him to suggest n-propanol or isopropanol for lipid extraction (isopropanol was his later choice (6, 7)). Attempting to meet the requirements discussed above, we developed a new and relatively simple method of extraction employing n-propanol (9), or chloroformmethanol (2:1). The latter proved to be a more useful solvent. The method will be described in detail below, with results of an examination of Drosophila lipids

Is level of neighbourhood green space associated with physical activity in green space?

Background There is accumulating evidence that greater availability of green space in a neighbourhood is associated with health benefits for the local population. One mechanism proposed for this association is that green space provides a venue for, and therefore encourages, physical activity. It has also been suggested that socio-economic health inequalities may be narrower in greener areas because of the equalised opportunity for physical activity green spaces provide. However, research exploring associations between the availability of green space and physical activity has produced mixed results. Limits to the assessment of the type and amount of physical activity which occurs specifically in green space may account for these mixed findings. This observational study was therefore concerned with the extent to which green space is a venue for physical activity and whether this could account for narrower socio-economic health inequalities in greener neighbourhoods.<p></p> Method Secondary analysis of cross sectional data on 3679 adults (16+) living in urban areas across Scotland matched with a neighbourhood level measure of green space availability. Associations between green space availability and both total physical activity, and activity specifically within green space, were explored using logistic regression models. Interactions between socio-economic position and physical activity were assessed. All models adjusted for age, sex and household income.<p></p> Results The availability of green space in a neighbourhood was not associated with total physical activity or that specifically in green space. There was no evidence that income-related inequalities in physical activity within green space were narrower in greener areas of Scotland.<p></p> Conclusion Physical activity may not be the main mechanism explaining the association between green space and health in Scotland. The direct effect of perceiving a natural environment on physiological and psychological health may offer an alternative explanation.<p></p&gt

Kondo effect in three-dimensional Dirac and Weyl systems

Magnetic impurities in three-dimensional Dirac and Weyl systems are shown to exhibit a fascinatingly diverse range of Kondo physics, with distinctive experimental spectroscopic signatures. When the Fermi level is precisely at the Dirac point, Dirac semimetals are in fact unlikely candidates for a Kondo effect due to the pseudogapped density of states. However, the influence of a nearby quantum critical point leads to the unconventional evolution of Kondo physics for even tiny deviations in the chemical potential. Separating the degenerate Dirac nodes produces a Weyl phase: time-reversal symmetry-breaking precludes Kondo due to an effective impurity magnetic field, but different Kondo variants are accessible in time-reversal invariant Weyl systems.Comment: 4+ pages, 2 figure

Purine and pyrimidine bases as growth substances for lactic acid bacteria

In 1936 Richardson (1) showed that uracil was essential for the anaerobic growth of Staphylococcus aureus, but not for aerobic growth of the same organism. Of five strains tested three required uracil, while one required both guanine and uracil for growth. Thymine or cytosine did not replace uracil for this organism. These experiments suggested that hydrolytic products of nucleic acids might become factors limiting growth of various organisms under certain conditions. Bonner and Haagen-Smit (2) in 1939 showed that adenine greatly stimulated growth of leaves under defined conditions, while Möller (3) showed that adenine was required for growth of Streptobacterium plantarum. Pappenheimer and Hottle (4) recently showed that adenine was necessary for the growth of a strain of Group A hemolytic streptococci; it could be replaced by hypoxanthine, guanine, anthine, guanylic acid or adenylic acid. They made the very interesting observation that adenine was unnecessary for growth of this organism if the carbon dioxide tension was maintained at a sufficiently high level

Real-space renormalization group flow in quantum impurity systems: local moment formation and the Kondo screening cloud

The existence of a length-scale $\xi_K\sim 1/T_K$ (with $T_K$ the Kondo temperature) has long been predicted in quantum impurity systems. At low temperatures $T\ll T_K$, the standard interpretation is that a spin-$\tfrac{1}{2}$ impurity is screened by a surrounding `Kondo cloud' of spatial extent $\xi_K$. We argue that renormalization group (RG) flow between any two fixed points (FPs) results in a characteristic length-scale, observed in real-space as a crossover between physical behaviour typical of each FP. In the simplest example of the Anderson impurity model, three FPs arise; and we show that `free orbital', `local moment' and `strong coupling' regions of space can be identified at zero temperature. These regions are separated by two crossover length-scales $\xi_{\text{LM}}$ and $\xi_K$, with the latter diverging as the Kondo effect is destroyed on increasing temperature through $T_K$. One implication is that moment formation occurs inside the `Kondo cloud', while the screening process itself occurs on flowing to the strong coupling FP at distances $\sim \xi_K$. Generic aspects of the real-space physics are exemplified by the two-channel Kondo model, where $\xi_K$ now separates `local moment' and `overscreening' clouds.Comment: 6 pages; 5 figure