Determination of avrami-exponents of isotactic polypropylene by means of X-ray methods

Avrami-exponents of polypropylene have been measured using two methods: observing the spherulitic growth in the polarization microscope, and measuring the crystallinity as a function of crystallization time using X-ray wide angle scattering. Both methods yield the same values, showing that the determination of the Avrami-exponent with optical microscopy is of sufficient accuracy despite the limitations of this method imposed by the restricted crystallization volume between the glass slides. Using the X-ray method, the Avrami-exponent of the secondary crystallization volume between the glass slides. Using the X-ray method, the Avrami-exponent of the secondary crystallization occurring at longer crystallization times can be measured. It is shown that this type of crystallization takes place within the already existing spherulites, whose size distribution is not changed.     

Toxicity of sodium nitrilotriacetate (NTA) to the fathead minnow and an amphipod in soft water

Amphipods, Gammarus pseudolimnaeus Bousfield and fathead minnows, Pimephales promelas Rafinesque, were submitted to acute (96-h) and chronic (generation-cycle) bioassays with sodium nitrilotriacetic acid (NTA). All measurements are reported as Na₃NTA. The average 96-h TL50 values under flow-through conditions were 98 mg 1⁻¹NTA for the amphipod and 114 mg 1⁻¹ for the fathead minnow. The acute toxicity of NTA was caused in part by the high pH resulting from the addition of large amounts of NTA (> 100 mg 1⁻¹) to soft water. Controlling pH reduced the lethality of NTA by at least one-half to fathead minnow larvae. The chronic no-effect level of NTA to the amphipods was 19 mg 1⁻¹; in fathead minnows, it exceeded the highest exposure level (> 54 mg 1⁻¹).     

Single-molecule biophysics: at the interface of biology, physics and chemistry

Single-molecule methods have matured into powerful and popular tools to probe the complex behaviour of biological molecules, due to their unique abilities to probe molecular structure, dynamics and function, unhindered by the averaging inherent in ensemble experiments. This review presents an overview of the burgeoning field of single-molecule biophysics, discussing key highlights and selected examples from its genesis to our projections for its future. Following brief introductions to a few popular single-molecule fluorescence and manipulation methods, we discuss novel insights gained from single-molecule studies in key biological areas ranging from biological folding to experiments performed in vivo.     

Effect of Substitution of High Stearic Low Linolenic Acid Soybean Oil for Hydrogenated Soybean Oil on Fatty Acid Intake

High stearic, low α-linolenic acid soybean oil (HSLL) has been developed via traditional breeding to serve as a substitute for partially hydrogenated soybean oils used in food manufacturing. The purpose of this study was to estimate the impact on fatty acid intake in the United States if HSLL were substituted for partially hydrogenated soybean oils used in several food categories, including baked goods, shortenings, fried foods, and margarines. Using National Health and Nutrition Examination Survey (NHANES) data (1999–2002), baseline intakes of five fatty acids and trans fatty acids (TFA) were determined at the mean and 90th percentile of fat consumption. Then intakes of these fatty acids were determined after HSLL was substituted for 100% of the partially hydrogenated soybean oils used in these four food categories. The results show that baseline intake of stearic acid is 3.0% energy at the mean and 3.3% energy at the 90th percentile. Use of HSLL could increase stearic acid intake to about 4–5% energy. Mean intakes of TFA could decrease from 2.5 to 0.9% energy, and intake of palmitic acid would remain unchanged. Use of HSLL as a substitute for partially hydrogenated soybean oils would result in changes in the fatty acid composition of the US diet consistent with current dietary recommendations.     

High velocity flyer plate launch capability on the Sandia Z accelerator

A method has been developed for launching plates useful for equation of state (EOS) studies to high velocities using fast pulsed power on the Sandia National Laboratories Z Accelerator. The technique employs magnetic pressure developed in an insulating gap between the anode and cathode of the machine to provide smoothly increasing, quasi-isentropic loading to plates of 9 – 12 mm in diameter and hundreds of microns thickness. Successful launches of titanium to 12km/s, aluminum to 13km/s, and copper to 10km/s have been demonstrated. The plates were monitored through the entire launch process with both conventional and spatially resolved velocity interferometry to obtain acceleration histories and impact profiles. Impacts of the flyers into aluminum wedges were also performed to experimentally estimate final plate thickness. Initial indications are that the plates are intact, slightly bowed, and at essentially ambient state.