Preparation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) particles in O/W emulsion

In the present paper, we investigate the preparation of polymeric particles based on the biodegradable polyester poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). A new technique for PHBV particle preparation has been developed. This method utilizes the thermoreversible gelation of PHBV in toluene. Particles have been obtained by the secondary dispersion technique in a three-step procedure: (a) preparation of PHBV solution in toluene; (b) preparation of O/W emulsion by ultrasound followed by the gel formation in toluene/PHBV droplets; and (c) toluene extraction. In the present study we investigated the influence of the stabilizer type and its concentration in the aqueous phase, ultrasound power, and PHBV concentration in toluene on the size and stability of the formed droplets as well as the final PHBV particles. It has been found that PEO/PS block copolymers are the best stabilizers for the present system as compared to conventional tensides such as SDS or CTAB. It has been found that PEO/PS block copolymers allow obtaining PHBV particles with a regular shape and controlled dimensions after toluene extraction. The minimal size of the PHBV particles obtained by this technique was ca. 100 nm. The obtained particles exhibit a relatively broad particle size distribution and the particle shape is strongly affected by the block copolymer composition, ultrasound power and the way of toluene extraction.     

Atomistic basis for the plastic yield criterion of metallic glass

Because of their disordered atomic structure, amorphous metals (termed metallic glasses) have fundamentally different deformation mechanisms compared with polycrystalline metals. These different mechanisms give metallic glasses high strength, but the extent to which they affect other macroscopic deformation properties is uncertain. For example, the nature of the plastic-yield criterion is a point of contention, with some studies reporting yield behaviour roughly in line with that of polycrystalline metals, and others indicating strong fundamental differences. In particular, it is unclear whether pressure- or normal stress-dependence needs to be included in the plastic-yield criterion of metallic glasses, and how such a dependence could arise from their disordered structure. In this work we provide an atomic-level explanation for pressure-dependent yield in amorphous metals, based on an elementary unit of deformation. This simple model compares favourably with new atomistic simulations of metallic glasses, as well as existing experimental data.     

Bücherschau

Ohne Zusammenfassung VDI     

The monostatic/bistatic approximation

Many radar cross section (RCS) prediction codes are limited to one monostatic return per run. However, such codes can calculate multiple bistatic returns per incident angle for a relatively small amount of additional computer resources. This article describes a method of using bistatic returns to generate multiple monostatic predictions for each incident angle computed. Typical results are presented, and show that the accuracy is initially high, and then degrades as the separation angle between the incident and viewing angles becomes large     

On the inhibition of cholinesterases by pancuronium (author''s transl)

1. The inhibition by pancuronium of acetylcholinesterase (AChE) and of plasma cholinesterase (ChE) was investigated in vitro regarding a) the sensitivity of both enzymes; b) the mechanism and constants of inhibition; and c) the relationship between the neuromuscular blocking and the anticholinesterase activity of pancuronium. 2. Pancuronium is a reversible inhibitor of both AChE and ChE. The inhibitory potency regarding ChE ([I]50=2.7 X 10(-7) M; Ki=4.2 X 10(-8) M) is highly selective and about 1000-fold higher than compared to AChE ([I]50=2.4 X 10(-4) M; Ki=3.5 X 10(-5) M). 3. The kinetic analysis by means of an Lineweaver-Burk plot and an Arunlakshana-Schild plot displayed a pure competitive mechanism of inhibition. 4. The inhibition of AChE and ChE is thought to be induced by a reversible binding of pancuronium to the anionic subsite of the active center, thus decreasing the formation of the primary enzyme-substrate complex. 5. The clinical administration of pancuronium for muscular relaxation during anaesthesia (0.01-0.08 mg/kg) will result in a concentration of approximately 10(-7)=10(-6) M in the extracellular fluid. Thus, an inhibition of plasma ChE can be expected to occur under clinical conditions, however, probably without practical significance.     

Incremental Confined Types Analysis

Research related to alias protection and related concepts, such as, confined types and ownership types has a long tradition and is a promising concept for the design and implementation of more reliable and secure software. Unfortunately, the use of these concepts is not widespread as most implementations are proofs of concept and fall short with respect to the integration with standard software development tools and processes.In this paper, we discuss an implementation of confined types based on Java 5 annotations. The contribution of this paper is twofold: First, we discuss the incrementalization of the confined types analysis and second, we present the integration of the analysis into Eclipse using the static analysis platform Magellan.     

The Effect of Parameter Estimation on Upper‐sided Bernoulli Cumulative Sum Charts

The Bernoulli cumulative sum (CUSUM) chart has been shown to be effective for monitoring the rate of nonconforming items in high‐quality processes where the in‐control proportion of nonconforming items (p₀) is low. The implementation of the Bernoulli CUSUM chart is often based on the assumption that the in‐control value p₀ is known; therefore, when p₀ is unknown, accurate estimation is necessary. We recommend using a Bayes estimator to estimate the value of p₀ to incorporate practitioner knowledge and to avoid estimation issues when no nonconforming items are observed in phase I. We also investigate the effects of parameter estimation in phase I on the upper‐sided Bernoulli CUSUM chart by using the expected value of the average number of observations to signal (ANOS) and the standard deviation of the ANOS. It is found that the effects of parameter estimation on the Bernoulli CUSUM chart are more significant than those on the Shewhart‐type geometric chart. The low p₀ values inherent to high‐quality processes imply that a very large, and often unrealistic, sample size may be needed to accurately estimate p₀. A methodology to identify a continuous variable to monitor is highly recommended when the value of p₀ is low and the required phase I sample size is impractically large. Copyright © 2012 John Wiley & Sons, Ltd.     

Corrosion of nanocrystalline Ni–W alloys in alkaline and acidic 3.5 wt.% NaCl solutions

The corrosion behaviour of reverse-pulse electrodeposited nanocrystalline nickel tungsten alloys (nc Ni–W) in pH 3 and 10 3.5 wt.% NaCl solutions is investigated and analysed as a function of grain size. A potentiodynamic polarisation study reveals that the corrosion rate of nc Ni–W generally increases with the reduction of grain size in alkaline condition, but decreases with the reduction of grain size in acidic environment. Furthermore, for both environments, nc Ni–W alloys exhibit superior localised corrosion resistance than a microcrystalline Ni control specimen. Factors controlling the corrosion behaviour of these materials, including grain size, tungsten content, passivation and crystallographic texture are addressed.     

Effects of field-manure applications on stratified 17β-estradiol concentrations

The occurrence of the manure-borne estrogen, 17β-estradiol (E2), was investigated in laboratory and field soils. In the laboratory, E2 was applied to soil to simulate concentrations found in swine (Sus scrofa domestica) manure (5000 ng L⁻¹). The aqueous-extracted E2 dissipated in the soil by 98% within 1 h and was not significantly different from background concentrations (18 ng L⁻¹) for the duration of the experiment (64 h). In the field study, soil cores were taken before and several dates after swine manure application. Equivalent porewater concentrations of water-extractable E2 were determined in 0.15-m increments down to the water table (0.70-2.00 m deep). The average frequency of detection for 168 samples was 38% (average = 40 ng L⁻¹ porewater equivalents). Eleven days after manure application there was no significant effect on E2 detection frequency or concentration. However, E2 concentrations significantly increased by 6 months after manure application, and appeared to be related to precipitation. Concentrations then returned to original levels by 17 months after manure application. Manure did not have an immediate effect on E2 occurrence due to the capacity of the soil to rapidly sorb E2. However, it appears that soil may act as a long-term reservoir for E2 in the environment, which may be periodically released through desorption.     

Universal features of grain boundary networks in FCC materials

Grain boundary character distributions and triple junction distributions have been determined for 70 experimental microstructures, comprising aluminum-, copper-, austenitic iron- and nickel-based alloys in a wide variety of processed states. In these FCC metals, the fraction of coincidence site lattice (CSL) boundaries ranges from about 12% (as for a random Mackenzie distribution) to values as high as 75%. Despite wide variations in composition, processing, and grain size, we find that the grain boundary character distribution and triple junction distributions of these materials have striking similarities, and can be described by just a few parameters. This universality arises due to the highly non-random laws that govern the assembly of the grain boundary network, and due to the kinematic limitation that CSL boundaries arise primarily through twinning.