Determination of amorphous content of lactose samples by solution calorimetry

Earlies studies suggest that solution calorimetry can be used to determine the extent of amorphous content of drug and excipient, when the solubility and dissolution rate of the compound in the chosen solvent are reasonably high. In the present study, the use of solution calorimetry for assessment of amorphous content of a sample that is not completely dissolved in a solvent was evaluated. Physical mixtures of lactose and spray-dried lactose samples were analysed. The amorphous content of the physical mixtures and the spray-dried samples varied from 0% to 100% determined by isothermal microcalorimetry. The enthalpy of solution (Δ_solH) was determined in water. The lactose samples were dissolved quickly in water. In addition, the enthalpy accompanied with an addition of a lactose sample in an over saturated aqueous solution (Δ_satH) (prepared from the corresponding lactose sample) was determined. The lactose sample did not completely dissolve in the over saturated aqueous solution. An excellent correlation was observed between Δ_solH and the amorphous content of the samples. Interestingly, there was a linear correlation also between Δ_satH and the amorphous content of the samples. Further, a linear relationship was observed between the Δ_satH and the Δ_solH of the samples. Therefore, solution calorimetry may represent a rapid and simple method for determining the amorphous content also in samples that are not completely dissolved in the solvent.     

Certification of instruments and devices of the threshold type

A program is described for determining and simulating the probit function reliability Probistics. __________ Translated from Izmeritel’naya Tekhnika, No. 10, pp. 70–71, October, 2007.     

A modeling perspective on the culture of driving

Each driver is influenced by the collective behavior of other drivers. At the same time, each driver is also part of this collective, and thus influences others. Underlying many driver control and traffic safety programs are two implicit and related assumptions: that drivers are sensitive to the “culture of driving” around them and emulate it; and, that a small shift in the behavior of few might be amplified or snowball to a much larger effect resulting in a changed traffic environment or a modified culture of driving. The paper discusses possible mechanisms for the interactions between individuals, collectives, and culture, drawing on literature from social psychology, sociology, economics, communication, epidemiology, and other disciplines. Traffic behavior modeling could benefit from considering concepts developed in other social disciplines while providing challenging research issues and data sources for testing and developing those concepts.     

The use of road humps for moderating speeds on urban streets.

Road humps are devices placed in the path of traveling vehicles. They are used in many communities to keep a uniform and low speed on a residential street or to reduce speeds at specific locations, such as intersections or pedestrian crosswalks. While the effectiveness of road humps in moderating speeds at the site of installation is generally considered proven, the actual adoption of the device remains controversial at the level of the community and the practicing engineers. The present paper, based on literature review and an international survey, evaluates community acceptance of the device and the factors influencing it; describes the various approaches taken to solve problems such as accommodating public transport and emergency vehicles; and assesses the legal status of the device.     

Power efficient uplink scheduling in SC-FDMA: benchmarking by column generation

We study resource allocation in cellular systems and consider the problem of finding a power efficient scheduling in an uplink single carrier frequency division multiple access system. Due to the discrete nature of this problem and its computational difficulty, particularly in a real-time setting, the use of suboptimal algorithms is common practice. We aim at an effective way of gauging the performance of suboptimal algorithms by finding tight bounds on the global optimum. Toward this end, we first provide a basic integer linear programming formulation. Then we propose a significantly stronger column-oriented formulation and a corresponding column generation method, as well as an enhanced column generation scheme. The latter extends the first scheme through the inclusion of a stabilization technique, an approximate column generation principle, and a tailored heuristic that is embedded in the column generation scheme to find high-quality though not necessarily global optimal solutions. The computational evaluation demonstrates that compared with a poor performance by the integer linear programming formulation, the column generation method can produce near-optimal schedules that enable a sharp bounding interval. The enhanced column generation method significantly sharpens the bounding interval. Hence the column generation approach serves well for the purpose of benchmarking results for large-scale instances.     

Differential Disrupting Effects of Prolonged Low-Dose Exposure to Dichlorodiphenyltrichloroethane on Androgen and Estrogen Production in Males

Dichlorodiphenyltrichloroethane (DDT) is the most widespread, persistent pollutant and endocrine disruptor on the planet. Although DDT has been found to block androgen receptors, the effects of its low-dose exposure in different periods of ontogeny on the male reproductive system remain unclear. We evaluate sex steroid hormone production in the pubertal period and after maturation in male Wistar rats exposed to low doses of o,p’-DDT, either during prenatal and postnatal development or postnatal development alone. Prenatally and postnatally exposed rats exhibit lower testosterone production and increased estradiol and estriol serum levels after maturation, associated with the delayed growth of gonads. Postnatally exposed rats demonstrate accelerated growth of gonads and higher testosterone production in the pubertal period. In contrast to the previous group, they do not present raised estradiol production. All of the exposed animals exhibit a reduced conversion of progesterone to 17OH-progesterone after sexual maturation, which indicates putative attenuation of sex steroid production. Thus, the study reveals age-dependent outcomes of low-dose exposure to DDT. Prenatal onset of exposure results in the later onset of androgen production and the enhanced conversion of androgens to estrogens after puberty, while postnatal exposure induces the earlier onset of androgen secretion.     

Observations on the uniformity of immersion tin coatings on copper

The development of chemical tin coatings by a replacement reaction Cu+Sn²⁺Cu²⁺+Sn from hydrochloric acid based and methanesulphonic acid based baths on the inner surface of a copper tube was studied by transmission electron microscopy and scanning electron microscopy in order to explore the factors influencing the uniformity of tin coatings. Despite the fact that tin coatings develop in different ways in studied baths, uniform coatings are equally plated from both these baths when the substrate surface is clean and smooth. However, differences in the surface-sensitivity, i.e. the dependence of coating uniformity on the substrate surface condition, of plating baths materialise when plated on irregular or improperly cleaned substrate. A hydrochloric acid based bath may yield non-uniform coatings on irregular or improperly cleaned substrate, since large-sized grains develop immediately after coating initiation. These large grains are suggested to orientate to follow the contours of impurity particles or surface irregularities introducing misalignment in grain columns and, thus, non-uniformity into coatings. In contrast, a methanesulphonic acid based bath is still able to produce uniform tin coatings on contaminated or rough surfaces, as the coating is proposed to accommodate to substrate surface irregularities by the build-up of a nanocrystalline zone at the early stages of tin coating deposition. Sulfur-containing elements in this methanesulphonic acid based plating bath play the central role in the nanocrystalline layer formation.     

Expert system for analysis of quality in production of electronics

Quality issues have become increasingly important in the production of electronics, especially when dealing with electronic products not assimilated to the mainstream of consumer electronics, but rather to the group of industrial electronic devices and machinery designed to last for years or even decades. In this paper, an intelligent optimization and modeling system for electronics production is demonstrated. The system exploits real production data and can be used to diagnose and optimize the manufacturing processes. It contains three modules consisting of appropriate mathematical tools specifically tailored to each task: (1) preprocessing, (2) variable selection, and (3) optimization modules. Moreover, concrete examples are presented from the latter two modules, by using a wave soldering process as a case study. Currently, the system works on the Matlab platform, but can be programmed into standalone software and automated in the future. The results illustrate that the system can offer an efficient tool for diagnostics and process optimization in the electronics industry.