Type I X-ray Bursts at Low Accretion Rates

Neutron stars, with their strong surface gravity, have interestingly short timescales for the sedimentation of heavy elements. Recent observations of unstable thermonuclear burning (observed as X-ray bursts) on the surfaces of slowly accreting neutron stars ($< 0.01$ of the Eddington rate) motivate us to examine how sedimentation of CNO isotopes affects the ignition of these bursts. We further estimate the burst development using a simple one-zone model with a full reaction network. We report a region of mass accretion rates for weak H flashes. Such flashes can lead to a large reservoir of He, the unstable burning of which may explain some observed long bursts (duration $\sim 1000$ s).Comment: 6 pages, 2 figures, submitted to the proceedings of the conference "The Multicoloured Landscape of Compact Objects and Their Explosive Origins'', 2006 June 11--24, Cefalu, Sicily (Italy), to be published by AI

A field and grenhouse study of the effects of two levels of nitrogen, phosphorus, and potassium on the growth and development of cantaloupes

In the continental United States the name cantaloupe is improperly applied to all varieties of muskmelons that are included in Cucumis melo var. reticulatus, the variety commonly grown in this country. Because such usage has resulted in the adoption of the name cantaloupe, this term will be used through this thesis. Probably no fruit offered to the American public is as appealing and tasty as the cantaloupe when the quality is good or as unappetizing when the quality is poor. The cantaloupe is offered to the public as a fruit to be purchased solely for the enjoyment of its flavor. A cantaloupe with poor flavor is worthless. Because of this assumption most of the research work in breeding and production of cantaloupes is done with one principal end in view: to produce high yielding varieties with improved flavor and qaulity (18).* The cantaloupe is difficult to grow in many areas. During its early stages of growth the plants need warm weather, ample soil moisture. and a dry atmosphere. Frequent rains or cloudy weather while cantaloupes are ripening may lower the quality of the fruit (4). These factors make successful cantaloupe culture in humid areas more difficult than the culture of many other vegetable crops. The mineral requirements of the cantaloupe have not been thoroughly investigated, This study was conducted in order to obtain a better under-standing of the mineral requirements of this crop when grown in unfavor-able, humid areas. Two experiments were designed to study the inter relationships of two levels each of nitrogen, phosphorus, and potassium on the growth and development of cantaloupe plants and fruit

Growth response and nitrate- nitrogen content of soil and spinach when fertilized with different sources and rates of nitrogen

The purpose of this investigation was to determine the effects of rates and sources of nitrogen on growth of Spinacia oleracea L. cultivar Chesapeake and on nitrate-nitrogen content of leaves and soil samples from 0-4 and 4-8-inch depths within the fertilized plots. One hundred and 200 lbs N/A from ammonium nitrate, calcium nitrate, ammonium sulfate, and sulfur-coated urea was applied in split applications to spring and fall spinach. Fresh weight of plants was determined at harvest stage and nitrate-nitrogen content of leaves and soil from 0-4 and 4-8-inch zones was determined periodically throughout the study. Fresh weight of plants was highest when 100 lbs N/A was applied from calcium or ammonium nitrate. Response to nitrogen fertilization as indicated by nitrate-nitrogen content of leaves was negligible in the fall experiment, but much greater in the spring test. Nitrate-nitrogen content of spinach leaves from the fall test was significantly increased at only two of seven sampling dates by application of 200 lbs N/A from ammonium nitrate, calcium nitrate, or sulfur-coated urea. In contrast, increases were found in nitrate-nitrogen content of leaves from spring spinach at almost all sampling dates regardless of the source of nitrogen when 200 lbs N/A was applied. In the fall study increased nitrate-nitrogen levels were found in soil at the 0-4 and 4-8-inch depths at two of six sampling dates when plots were fertilized with 200 lbs N/A from ammonium nitrate or calcium nitrate. Large increases in nitrate-nitrogen content were found in 0-4-inch soil profiles in the spring experiment when plots were fertilized with either 100 or 200 lbs N/A from either calcium or ammonium nitrate. Moderate increases in nitrate-nitrogen were also found in 0-4-inch soil profiles from plots fertilized with either 100 or 200 lbs N/A from ammonium sulfate. Levels of nitrate-nitrogen in the 4-8-inch profiles were increased slightly in the spring experiment when 200 lbs N/A was applied from ammonium nitrate or ammonium sulfate. Greatest increases were observed when 200 lbs N/A was applied from calcium nitrate. In conclusion these data indicate that applications of 100 lbs N/A from calcium or ammonium nitrate was near the optimum rate for spinach growth under conditions of these experiments and that 200 lbs N/A from ammonium nitrate, calcium nitrate, ammonium sulfate, or sulfur-coated urea may result in excessive levels of nitrate-nitrogen in plant tissue. The data also suggest that application of 200 lbs N/A from calcium nitrate, ammonium nitrate, or ammonium sulfate provide a potential for nitrate-nitrogen buildup in the soil and pollution of groundwater aquifers

V.—On a General Method of Substituting Iodine for Hydrogen in Organic Compounds, and on the Properties of Iodopyromeconic Acid

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A Career of Unyielding Exploration: In Memory of Ion C. Baianu (1947-2013)

We were deeply saddened to learn of the sudden death of our colleague, friend, and member of the Editorial Board of Quanta, Professor Ion C. Baianu, who unexpectedly passed away in Urbana, Illinois, USA, on February 10, 2013. Ion left behind his wife, Kimiko, his son, Stephen, and daughters, Antonia and Christina. He also left behind the achievements of a profound and illustrious career in his chosen fields of biophysics, spectroscopy, food science, and bioengineering.Quanta 2013; 2: 1–6