Constraining the Geometry of the Neutron Star RX J1856.5-3754

RX J1856.5-3754 is one of the brightest, nearby isolated neutron stars, and considerable observational resources have been devoted to its study. In previous work, we found that our latest models of a magnetic, hydrogen atmosphere matches well the entire spectrum, from X-rays to optical (with best-fitting neutron star radius R=14 km, gravitational redshift z_g~0.2, and magnetic field B~4x10^12 G). A remaining puzzle is the non-detection of rotational modulation of the X-ray emission, despite extensive searches. The situation changed recently with XMM-Newton observations that uncovered 7 s pulsations at the 1% level. By comparing the predictions of our model (which includes simple dipolar-like surface distributions of magnetic field and temperature) with the observed brightness variations, we are able to constrain the geometry of RX J1856.5-3754, with one angle < 6 deg and the other angle = 20-45 deg, though the solutions are not definitive given the observational and model uncertainties. These angles indicate a close alignment between the rotation and magnetic axes or between the rotation axis and the observer. We discuss our results in the context of RX J1856.5-3754 being a normal radio pulsar and a candidate for observation by future X-ray polarization missions such as Constellation-X or XEUS.Comment: 7 pages, 6 figures; MNRAS, accepte

A search for periodic modulations of the solar neutrino flux in Super-Kamiokande-I

A search for periodic modulations of the solar neutrino flux was performed using the Super-Kamiokande-I data taken from May 31st, 1996 to July 15th, 2001. The detector's capability of measuring the exact time of events, combined with a relatively high yield of solar neutrino events, allows a search for short-time variations in the observed flux. We employed the Lomb test to look for periodic modulations of the observed solar neutrino flux. The obtained periodogram is consistent with statistical fluctuation and no significant periodicity was found

Study of the factors affecting quality in varieties of potato Solanum tuberosum

In the studies reported here, certain small yet well defined differences have been found to exist between the starches of some six varieties of potato of different culinary quality. The different features of the starches have been reflected in the temperature of gelation, the length of the period of arrestment of temperature during the endothermic nature of the change of state, the amount of neat evolved during gelation, the optical density of gels, and the rate of retrogradation. Further differences were recorded for the values of absorption of light of complexes formed between the different starches and iodine, and for the mean size of granules and the proportions of granules of particular sizes. By obtaining starch from tubers lifted over the period early August to November, it was possible to carry out analyses to show the effect of advancing maturity on those features examined. With advance of season, the analyses showed certain distinctive trends. The size of granule increased in the starch of all varieties (except in "Golden Wonder" grown at Pentlandfield). while there was an appreciable drop in the temperature of ,elation. Optical density of the gels of starch declined, but the work of the second season showed in the varieties "Golden Wonder" and "Majestic" that this decline occurred over only part of the season, to be followed by an increase, the extent of which differed between the two varieties;. The values of the intensity of colour of complexes of starch- iodine, with the exception of "Golden Wonder" and "Crams Royal ", remained essentially unaltered with advance in the maturity of the tubers. In the varieties "Golden Wonder" and "Crtaigs Róyal" grown at Fentlandfield, and in the variety "Majestic" grown at the R.B.G. there was a decrease in the intensity of colour with advance in maturity. The seasonal changes in the features examined were more marked generally in the better culinary varieties. The temperatures:,of gelation were correlated with the values of optical density, in particular high temperatures of gelation were accompanied by high values of optical density. Further, the higher values of colour yielded by the complexes of starch -iodine were also features of starches gelating at high temperatures, and hence of starches whose gels were dense optically. The highest values of these features were found in the varieties of best culinary quality. Apart from a negative correlation, on the whole, between the change in the average size of granule and the drop in the temperature of gelation with advancing maturity, the size of granule did not appear to be related to the differences exhibited in gelation between varieties, or even within a variety. As previously mentioned the smallest granules in a sample of a starch have a tendency to gelate at higher temperatures than larger granules. However it would appear that this tendency was largely prevented in the method developed in this work for determining the temperature of gelation of a sample of Granules, by reason of the gelation of the main mass of granules at the same temperature (the temperature of the endothermic reaction). This was shown particularly by the insignificant variation within a variety of the temperature of gelation of starches obtained at a given occasion from separate tissues, in spite of quite large differences in the proportions of granules of different sizes in those separate tissues. Under certain other conditions of gelation the fact that the small granules gelate at higher temperature than larger granules is due, in part at least, to a physical effect resulting in the relation between mass of granule and surface area (which as mentioned before is explained by Alsberg 1936). In the method of gelation used here this physical effect has been largely overruled; differences in temperature of gelation that have been shown to exist between varieties, and at different times, must therefore be the result of differences in the actual constitution of the granules. Therein probably lies the most important advantage in this method of studying gelation. The inference that size of granule, as such, is not a criterion of the composition of the granule is borne out further by the results obtained from the shading of certain plants. While reduction of light to the parent plants altered significantly the temperature of gelation, value of optical density of gels, and absorption value of the complex of starch -iodine, of the starches of "Golden Wonder ", but only to a small degree the starches of "Majestic ", the average size of granule was least affected by shading in "Golden Wonder" and appreciably altered in "Majestic". It follows that the size of granule may be of little use as a guide to culinary quality of varieties. In connection with alteration of light to plants, it would be desirable to study the effect of increased intensity of light on the characteristics of the starch of the tuber i.e. to simulate to some degree the conditions of light obtaining in southerly potato growing areas. It was considered impractical in the present study to carry this out. The results showed however that decreasing the level of li ht available to the plants (although this level may never obtain in "nature ") could alter the properties of starch. Under the conditions obtaining in this work, it was, however, somewhat surprising that the alterations were more marked in "Golden Wonder" than in "Majestic". The results obtained by shading plants of "Majestic" in the field trial were different in some respects to those obtained in the pilot work, which illustrates the value of investigating the application of specific treatments on a large scale. In particular the reduction in yield of tubers under shade was less marked in the field trial than might have been expected (table 13), and the foliage was increased in stature in contrast to the notable reduction in heir -ht obtained in the pilot work. The increase however was only discerned by measurement (table 19). In view of the variation in quality that can occur in potatoes grown in different regions, it seems pertinent that more work should be directed to a study of the effect of factors of environment on culinary quality. The experimental evidence that has been obtained in this research, and the interpretations which have been made upon the evidence, can account in part at least for the differences in the culinary characteristics, particularly of texture, to be found in different varieties. There is scope for considerable further research; some of the lines along which investigation might proceed have been indicated

Diagnostic accuracy and cost-effectiveness of alternative methods for detection of soil-transmitted helminths in a post-treatment setting in western Kenya.

OBJECTIVES: This study evaluates the diagnostic accuracy and cost-effectiveness of the Kato-Katz and Mini-FLOTAC methods for detection of soil-transmitted helminths (STH) in a post-treatment setting in western Kenya. A cost analysis also explores the cost implications of collecting samples during school surveys when compared to household surveys. METHODS: Stool samples were collected from children (n = 652) attending 18 schools in Bungoma County and diagnosed by the Kato-Katz and Mini-FLOTAC coprological methods. Sensitivity and additional diagnostic performance measures were analyzed using Bayesian latent class modeling. Financial and economic costs were calculated for all survey and diagnostic activities, and cost per child tested, cost per case detected and cost per STH infection correctly classified were estimated. A sensitivity analysis was conducted to assess the impact of various survey parameters on cost estimates. RESULTS: Both diagnostic methods exhibited comparable sensitivity for detection of any STH species over single and consecutive day sampling: 52.0% for single day Kato-Katz; 49.1% for single-day Mini-FLOTAC; 76.9% for consecutive day Kato-Katz; and 74.1% for consecutive day Mini-FLOTAC. Diagnostic performance did not differ significantly between methods for the different STH species. Use of Kato-Katz with school-based sampling was the lowest cost scenario for cost per child tested ($10.14) and cost per case correctly classified ($12.84). Cost per case detected was lowest for Kato-Katz used in community-based sampling ($128.24). Sensitivity analysis revealed the cost of case detection for any STH decreased non-linearly as prevalence rates increased and was influenced by the number of samples collected. CONCLUSIONS: The Kato-Katz method was comparable in diagnostic sensitivity to the Mini-FLOTAC method, but afforded greater cost-effectiveness. Future work is required to evaluate the cost-effectiveness of STH surveillance in different settings

Thermal effect on the life-cycle parameters of the medically important freshwater snail species lymnaea (radix) luteola (lamarck)

The snails Lymnaea (Radix) luteola exhibited marked variations in growth, longevity, and attaining sexual maturity at different temperatures and diets. At 10 C, irrespective of foods, pH and salinity of water, the snails had minimum life span, maximum death rate and lowest growth rate. At 15 C, the growth rate was comparatively higher and the snails survived for a few more days. But at these temperatures they failed to attain sexual maturity. Snails exposed to pH 5 and 9 at 20 , 25 , 30 , 35 C and room temperatures (19.6 -29.6 C); to 0.5, 1.5 and 2.5 NaCl at 20 and 35 C; to 2.5 NaCl at 25 C and room temperatures failed to attain sexual maturity. The snails exposed to pH 7 and different salinity grades at 20 , 25 , 30 , 35 C and room temperatures became sexually mature between 25-93 days depending upon the type of foods used in the culture