Reactions of 4-Chloromethyl-1,3-dioxolan-2-one with Phenols as A New Route to Polyols and Cyclic Carbonates

Reaction of 4-chloromethyl-1,3-dioxolan-2one ( 1 ) with phenol in the presence of potassium carbonate was studied and found to yield 4-phenoxymethyl-1,3-dioxolan-2one ( 2 ) and 3-phenoxypropan-1,2-diol ( 3 ). The latter compound 3 was also found to be formed as the main product in the reaction of 1 , phenol and sodium hydroxide at a temperature higher than 90°C. The effect of various factors on the reaction course and the yield of 2 and 3 was examined. It was found that the reaction studied can be extended to those of difunctional phenols such as 2,2-di(4-hydroxyphenyl)-propane producing the corresponding tetrahydroxyderivative – 2,2-bis-[4-(2,3-dihydroxypropoxy)phenyl]propane.     

Development,amino acid utilization and cell allocation in bovine embryos after in vitro production in contrasting culture systems

The effects of protein-supplemented and protein-free media on amino acid uptake, protein synthesis and cell differentiation in bovine blastocysts were investigated. Four formulations of synthetic oviduct fluid were used. Each formulation was identified by the principal supplement: bovine serum albumin (0.4%, w/v); polyvinyl alcohol (0.3%, w/v); or either of two steer sera (10%, v/v). After zygote culture, blastocyst yields (day 7.5) were lowest in protein-free medium and highest in albumin-supplemented medium. Subsequent 12 h incubation in the presence of both essential and non-essential amino acids was used for the measurement of amino acid flux. All blastocysts released alanine but consumed aspartate (P < 0.001) and the extent was influenced by prior culture conditions. Aspartate uptake was lower in blastocysts produced in protein-free conditions (P < 0.05) than in blastocysts produced in albumin-supplemented conditions. Consumption indices for 16 other amino acids were not influenced by blastocyst source. Cell counts and hatching incidences were highest for albumin-supplemented blastocysts, but were similar among blastocysts from the protein-free and serum-dependent treatments. Crucially, the use of protein-free medium for zygote culture did not compromise resultant blastocysts in terms of either de novo protein synthesis ([3H]phenylalanine incorporation) or trophectoderm function (phenotype based on interferon-tau detection). Thus, although blastocyst yields were compromised after zygote culture in a protein-free (vis-à-vis albumin-supplemented) medium, amino acid flux was qualitatively conserved, and only quantitatively modified in the case of alanine and aspartate. Moreover, vital properties of blastocysts that were produced, including de novo protein synthesis and trophectodermal cell function, apparently were not adversely affected by protein deprivation.     

优化功率在便携式应用中的挑战

便携式产品电源管理面临挑战 便携式应用产品的外形尺寸日趋小巧轻薄，但其糅合的功能却愈来愈多。这个趋势所衍生的需求是有效管理功率及减少板上的元件数目。为了应付这个挑战，半导体供应商在这个市场区间担当了不可或缺的角色。半导体供应商必须集成最好的低功率和高功率器件，并致力在低输出功率和待机状态下实现高效率。这种集成可以通过于一块基板或平台上整合所有器件，或者把所有器件集成在一个封装里作为混合电路来实现。由于便携式产品采用的外形尺寸越来越小，开关频率因此不断增加。随着开关频率提高，无源器件的尺寸则会减小。半导体供应商需要好好管理这个高频，正是它才实现了较小型的无源器件使用，从而实现尺寸更小的总体解决方案（其成本也可能更低）。最后，2．5G和3G的RF无线器件是“线性”（linear）的，故在低功率时很容易受低效率影响。由此可见，半导体供应商必需提供能在低功率时增加系统效率的功率管理芯片。     

Analysis of clinical and social features in a group of epileptics with frequent seizures

A multistep immunocytochemical method utilizing horseradish peroxidase as an immunologically bound marker was used to detect and localize IgA deposits in skin of patients with dermatitis herpetiformis at the ultrastructural level. IgA was found in the upper papillary dermis forming irregular aggregates in seemingly haphazard distribution. These aggregates were associated with microfibrillar bundles and with the microfibrillar component of the elastic tissue. IgA was also detected on anchoring fibrils, but showed no topical relationship to the basal lamina which was always spared. This finding indicates that basal lamina components do not serve as target sites for the immunologic reaction occurring in dermatitis herpetiformis. The selective affinity of IgA deposits to microbfibrillar bundles may be relevant to the hypothesis that the skin pathology in dermatitis herpetiformis is caused by circulating gluten-antigluten complexes, trapped in the skin by reticulin-bound antireticulin antibodies which cross-react with gluten.     

Startup transient simulation for natural circulation boiling water reactors in PUMA facility

In view of the importance of instabilities that may occur at low-pressure and -flow conditions during the startup of natural circulation boiling water reactors, startup simulation experiments were performed in the Purdue University Multi-Dimensional Integral Test Assembly (PUMA) facility. The simulations used pressure scaling and followed the startup procedure of a typical natural circulation boiling water reactor. Two simulation experiments were performed for the reactor dome pressures ranging from 55 kPa to 1 MPa, where the instabilities may occur. The experimental results show the signature of condensation-induced oscillations during the single-phase-to-two-phase natural circulation transition. The results also suggest that a rational startup procedure is needed to overcome the startup instabilities in natural circulation boiling water reactor designs.     

Investigation of the elementary reactions in the synthesis of poly(hydroxethers) in dipolar,aprotic solvents

The effect of the hydroxyl groups of various phenols on the course of the reaction of their alkali metal salts with epichlorohydrin in dipolar, aprotic solvents has been studied. It was found that the presence of phenols in the system leads to the formation of a complex salt of the type (ArO … H … OAr)^?Mt⁺, and to a considerable decrease in the reaction rate. The mechanism of the reaction of chlorohydrin ethers of phenols with alkali metal phenolates was also studied. The effect of various factors on the course of the reaction of glycidyl ethers with phenols was determined by kinetic measurements.     

Properties of CO2 copolymers with heterocyclic monomers

Basic properties of poly(propylene carbonate) and poly(propylene urethane) were estimated by means of additive methods. The properties estimated for the former polymer—an alternating CO²/propylene oxide copolymer—were compared with those determined experimentally. Properties of poly(styrene carbonate)—an alternating CO²/styrene oxide copolymer—were estimated and confronted with those of poly(4,4′-isopropylidene diphenylene carbonate) produced commercially.     

Cerium dioxide as a new reactive sorbent for fast degradation of parathion methyl and some other organophosphates

Cerium dioxide was used for the first time as reactive sorbent for the degradation of the organophosphate pesticides parathion methyl,chlorpyrifos,dichlofenthion,fenchlorphos,and prothiofos,as well as of some chemical warfare agents—nerve gases soman and O-ethyl S-[2-(diisopropylamino) ethyl] methylphosphonothioate(VX).CeO2 specimens were prepared by calcination of basic cerous carbonate obtained by precipitation from an aqueous solution.The CeO2 samples containing certain amounts(1 wt.%–5 wt.%) of the neighboring lanthanides(La,Pr,Nd) were prepared in a similar way from pure lanthanide salts.It was shown that ceria accelerated markedly the decomposition of parathion methyl causing the cleavage of the P-O-aryl bond in the pesticide molecule.A similar reaction mechanism was proposed for the degradation of other organophosphate pesticides and nerve agents.The degradation times(reaction half-times) were in an order of minutes in the presence of CeO2,compared to hours or days under common environmental conditions.The reaction in suitable organic solvents allowed conversions of about 90% for parathion methyl loading of 20 mg pesticide/g CeO2 within 2 h with a reactant half-life in the order of 0.1 min.The key parameter governing the degradation efficiency of CeO2 was the temperature during calcination.At optimum calcination temperature(about 773.15 K),the produced ceria retained a sufficiently high surface area,and attained an optimum degree of crystallinity(related to a number of crystal defects,and thus potential reactive sites).The presence of other lanthanides somewhat decreased the reaction rate,but this effect was not detrimental and permitted the possible use of chemically impure ceria as a reactive sorbent.A fast organophosphate degradation was demonstrated not only in non-polar solvents(such as heptane),but also in polar aprotic solvents(acetonitrile,acetone) that are miscible with water.This opens new possibilities for designing more versatile decontamination strategies.The cleavage of phosphate ester bonds is of a great importance not only for the degradation of dangerous chemicals(chemical weapons,pesticides),but also for interactions of ceria(especially the nano-sized one) in biologically relevant systems.     

Application of a solid‐state postpolycondensation method for synthesis of high molecular weight polycarbonates

Studies on the possibility of the application of the solid‐state postpolycondensation (SSP) process to increase the average molecular weight of bisphenol A‐based polycarbonate (PBC) were carried out. The thermally stable PBC with a very high molecular weight reaching about 50,000 g/mol was obtained by the applied SSP technique. Some factors influencing the effectiveness of the SSP process were initially examined: the mode of preparation (crystallization) of the PBC prepolymer, condensation temperature and time, and the vacuum applied in the reaction vessel. It was found that the superior yield of the high molecular weight PBC was obtained by the employing as high as possible values of the parameters taken into consideration. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2165–2171, 2000     

Investigations on organic catalysts for the maleic anhydride-propylene oxide copolymerization

Summary The influence of Lewis acidity of homogeneous organozinc catalyst RZnEt (R=C₂H₅-, CH₃O-, CH₃COO-, 2-CH₃OC₆H₄O-,3-CH₃ OC₆H₄O- and CH₃COCH=C(CH₃)O-) on monomer distribution in maleic anhydride-propylene oxide copolymers produced by this catalyst has been investigated. It was found that increasing the acidity (electron-accepting properties) of the Zn atom in the catalyst molecule caused an increase in the number of propylene oxide units in the obtained copolymers and a decrease of their average molecular weight.