热成型工艺的解决方案

成功的塑料热成型工艺解决方案,要求对加工工艺、模具设计、材料性能等因素进行全面综合分析。众多的热成型加工厂商往往只着眼于调整和改进工艺,以此来解决生产过程中所遇到的各种制品缺陷问题。其中采取的措施包括:试图延长加工循环周期、二次加工工序、或者通过改良设备装置     

Span及Tween的组成、性能、表征与应用

本文综述了Span及Tween两类乳化剂的组成,性能,表征与应用进展及发展趋势。     

Fresh water,energy, and food from the sea and the sun

Surface waters of tropic and sub-tropic seas hold most of the solar energy retained by the earth; but the heat therein may be increased even more by heat which can be added by intensive solar heaters. The sea water so heated naturally or additionally by the sun, when flash evaporated, gives vapors which may be passed through a heat engine to give power, then condensed at a lower pressure to give fresh water, which may be much more valuable than the power produced. Heat of condensation is removed by circulating cold sea water from a depth of a few thousand feet. This water from the deep also has considerable nutrients for sea plants and animals coming from the degradation of former sea life; and these nutrients may be used in well studied mariculture systems to grow commercial food fish in ponds adjacent the land-based plant. Various arrangements of flows of the several liquid streams are presented to illustrate variations to the process which will produce fresh water and/or electric power, also food fish. These modifications may be optimized with various component systems, some of which are well known and evaluated in this usage, including the use of a second thermodynamic fluid, conventional multistage flash evaporation, also two of its variations: Controlled Flash Evaporation and Vapor Reheat. Calculations indicate that even without the use of intensive solar heaters, a profitable desalination and mariculture operation may be expected which would pay for its substantial cost in two or three years of profits; however, the incorporation of certain intensive solar heaters may increase the profitability significantly.     

Scent,sex, and the self-calibrating rat

We propose that one mechanism whereby male rats,Rattus norvegicus, might gauge the reproductive condition of a female is by calibrating a stable odor with an odor that fluctuates through her reproductive cycle. We provide behavioral and histological evidence in support of such a self-calibration model. Male rats sniffed frequently at various body zones of females, and the proportion of sniffs deployed to each zone varied with the females' reproductive condition and relatedness. The females' haunches received more sniffs than any other part of their bodies, irrespective of their relatedness or reproductive condition. Furthermore, males tended to sniff the haunch after sniffing the forequarters, as part of a sequence of sniffing along a female from forequarters to hindquarters. Histology of the skin sebaceous glands indicated that the secretory activity of glands in the haunch, but not those in the forequarters, changed during estrus. Therefore, male rats had the opportunity to judge a female's reproductive status by calibrating the odor of her haunch against that of her forequarters. Self-calibration could represent a means of accommodating differences in odor within individuals.     

Isolation,identification, synthesis,and bioassay of the pheromone of the comstock mealybug and some analogs

The sex pheromone of the Comstock mealybug,Pseudococcus comstocki (Kuwana) was isolated from volatiles trapped from air passing over virgin female insects. Combined gas chromatography, mass and infrared spectroscopy, and microreactions indicated that the structure was 2,6-dimethyl-1,5-heptadien-3-ol acetate. This was confirmed by synthesis; several analogs were also prepared. The natural and synthetic pheromone caused similar trap capture of male insects. Synthetic analogs were significantly less attractive in field tests and the addition of minor amounts of the corresponding alcohol to the pheromone appeared to enhance trap capture, but the results were not statistically conclusive.     

Span及Tween类物质的组成、性能、表征与应用

本文综述了Span及TWeen两类乳化剂的组成、性能、表征与应用进展及发展趋势     

Structural Chemistry,Fuzzy Logic,and the Law

Chemistry is generally considered to be one of the exact sciences, which implies that much of the thinking and reasoning can be governed by “always” and “never” laws and rules. However, in practice, much of chemistry involves concepts that invoke general rules with the exceptions to those rules arousing curiosity and generating new experiments and theories that facilitate the progress of chemical science. The lack of precision, in fact, requires a mode of thinking and operating that has been called “fuzzy logic”, not necessarily in a pejorative sense, but rather recognizing the fundamental nature of this experimental science and how it plays out in practice. We provide herein some examples of fuzzy logic in the practice of chemistry and demonstrate how these are manifested in the role and behavior of expert witnesses, particularly in pharmaceutical patent litigations that deal with the solid forms of active pharmaceutical ingredients.     

Determination of iron,cobalt, copper,and zinc in the suspended phase,slime, and sludge from natural and wastewaters by the atomic absorption method

A comparison of the recommendations in foreign national standards and domestic experience shows that atomic absorption methods in flame (iron, zinc) and flameless atomization (cobalt, copper) are most acceptable for monitoring the concentration of iron, cobalt, copper, and zinc in natural and wastewaters, including the suspended phase, slime, and sludge. The basic stages of environmental methods of measurement (sample collection, sample preparation, and method of analysis) are discussed in consideration of foreign and domestic experience. The basic analytical parameters of the atomic absorption method metrologically investigated at the Khimvolokno Scientific and Industrial Association (SIA) and approved in the established order are reported. The suspended phase and filtrate (after separation of the suspended phase by filtration) from wastewaters from several viscose plants was analyzed. It was found that the concentration of iron, cobalt, and copper in the suspended phase was comparable to their concentration in the filtrate as soluble forms. The concentration of zinc in the suspended phase was insignificant.All-Russian Scientific-Research Institute of Polymer Fibres, Mytishchi. Translated from Khimicheskie Volokna, No. 1, pp. 56–60, January–February, 1994.     

Effect of concentration, temperature, moisture, liming and organic matter on the efficacy of the nitrification inhibitors benzotriazole, o-nitrophenol, m-nitroaniline and dicyandiamide

Laboratory experiments were carried out to study the effect of various factors that affect the efficacy of the nitrification inhibitors, benzotriazole, o-nitrophenol, m-nitroaniline and dicyandiamide. In a Paleustalf, increasing concentrations of the inhibitors from 0 to 15 mg/kg soil prolonged the nitrification up to 60 days. Increase in temperature from 10 to 30°C decreased the efficacy of all four nitrification inhibitors (by 6–62% at 30 days). Benzotriazole was equally effective in soil moisture conditions ranging from 40 to 80% of the maximum water holding capacity of the soil (WHC). o-Nitrophenol and m-nitroaniline were more effective at 60% WHC, while the efficacy of DCD was more at 40% WHC. Addition of 1000 mg/kg soil of fresh organic matter reduced the efficacies of o-nitrophenol, m-nitroaniline and benzotriazole by 55, 65 and 22%, respectively while the reduction in the efficacy of dicyandiamide was non-significant. Liming an acidic soil (Kandiustalf) to change the pH from 5.4 to 8.3 decreased the efficacies of the nitrification inhibitors and decreased the ammonium content in the soil at 30 days from 55 to 9 mg/kg in case of o-nitrophenol and m-nitroaniline and from 53 to 35 mg/kg in case of benzotriazole and dicyandiamide.     

PVC Stabilizers of the past,present, and future

When chemical additives were found that could minimize the loss of chemical and physical properties of a thermally-processable but heat-sensitive polymer called poly(vinyl chloride) (PVC), an industry was born. And with it grew the world of plastics additives. Stabilizers for PVC became and industry itself, feeding into and off of this versatile polymer industry, in an almost symbiotic relationship. There have been so many types of stabilizers in use throughout the past fifty years: inorganics, leads, organics, barium/cadmiums, calcium/zincs, organotins, and antimony. And so very many more have been conceived but not commercialized: organoleads, organoantimonys, bismuths, indiums, and a myriad of organic chemicals. What are the merits and deficiencies of these stabilizers? What of yesterday's products are still with us? What are the newer types? What might be tomorrow's products? This paper will attempt to review and discuss the past, present, and future of PVC stabilizers; the factors that are responsible for their variety, for influencing their research, development, and commercialization, and how these factors change with time.     

Transitions,relaxations, and thermodynamics in the glassy state

The PVT properties of polymer glasses are discussed from two points of view. First, as a low frequency tool in the study of sub-glass relaxations. Dilatometric results illustrate the sensitivity of the thermal expansivity and its temperature coefficient to dynamic processes occuring in the glass. The second point of view considers the quasi-thermodynamics of the non-equilibrium system, under conditions where the rates of relaxational processes are small in comparison with experimental rates, and time dependent processes are practically absent. The starting point is a theory of the equilibrium melt which describes the characteristic liquid disorder in terms of a temperature and pressure dependent hole or loosely, free volume fraction. This function is obtained by the minimization of a configurational free energy. Upon reaching the glass transition, this dependence is reduced, and further so in a sub-glass relaxation region. However, it is not eliminated until temperatures of the order of 50 to 70 K are reached. While this picture is qualitatively universal, significant quantitative differences are observed with different chemical structures and different thermal and pressure histories. A comparison of thermal expansivities of high and low T_g systems indicates that in the former the free volume retained upon reaching T_g is comparatively large and the departure from equilibrium or degree of freeze-in comparatively small. Similarly, it appears that the glassy densification generated by cooling the melt under pressure is more extensive in high T_g glasses. Such results imply structural differences. These should be investigated by comparative studies of (a) time dependent processes in terms of the free volume functions, (b) sorption and transport, and (c) the temperature dependent dynamics of density fluctuations.     

Cooperation,Conflict, and the Evolution of Queen Pheromones

While chemical communication regulates individual behavior in a wide variety of species, these communication systems are most elaborated in insect societies. In these complex systems, pheromones produced by the reproductive individuals (queens) are critical in establishing and maintaining dominant reproductive status over hundreds to thousands of workers. The proximate and ultimate mechanisms by which these intricate pheromone communication systems evolved are largely unknown, though there has been much debate over whether queen pheromones function as a control mechanism or as an honest signal facilitating cooperation. Here, we summarize results from recent studies in honey bees, bumble bees, wasps, ants and termites. We further discuss evolutionary mechanisms by which queen pheromone communication systems may have evolved. Overall, these studies suggest that queen-worker pheromone communication is a multi-component, labile dialog between the castes, rather than a simple, fixed signal-response system. We also discuss future approaches that can shed light on the proximate and ultimate mechanisms that underlie these complex systems by focusing on the development of increasingly sophisticated genomic tools and their potential applications to examine the molecular mechanisms that regulate pheromone production and perception.