Synthesis and self‐assembling behaviors of biotinylated pluronic/poly(lactic acid) biocompatible block copolymers in aqueous solutions

Four kinds of Biotinylated Pluronic/PLA block copolymers were synthesized by two‐step reactions. Pluronic were firstly modified by biotin to obtain B‐Pluronic‐OH. Biotin‐Pluronic‐PLA block copolymers were then produced by ring‐opening polymerization of the monomer L ‐lactide using Biotin‐Pluronic‐OH as the initiator and stannous octoate (Sn(Oct)₂) as the catalyst. The self‐assembling behaviors of Biotin‐Pluronic‐PLA block copolymers in aqueous solutions were examined by fluorescence measurement, dynamic light scattering (DLS), and transmission electron microscopic (TEM) techniques. The size of Biotin‐F127‐PLA‐61, Biotin‐F87‐PLA, and Biotin‐P85‐PLA nanoparticles were determined to be 198, 229, and 257 nm, respectively, and their morphologies were found to be spherical micelles. Biotin‐F127‐PLA‐87 produces both spherical micelles and large compound micelles with the size of 127 and 906 nm. The cytotoxicity studies using human ovarian cancer cells OVCAR‐3 indicate that Biotin‐Pluronic‐PLA block copolymers have good biocompatibility. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

提升磨削烧伤检测水平的方法和措施

文章指出,鉴于磨削烧伤传统测试方法存在的局限性,近年来,一种根据物理学Barkhansen原理研制的“磁弹法”检测仪已在一些企业获得了应用.文章阐述了基于线性回归方法,通过磨削烧伤特征值的定标提升仪器应用水平的过程,并从实际情况出发,提出了一个兼具准确可靠又合理可行的实施方案.     

Synthesis of poly(D,L‐lactic acid) modified by cholic acid via direct melt copolycondensation and its characterization

From D,L ‐lactic acid and the natural functional molecule cholic acid (CA), the biodegradable material poly(D,L ‐lactide–cholate) was synthesized via direct copolycondensation. For the CA/lactic acid (LA) molar feed ratio of 1/64, the optimal synthesis conditions were as follows: a prepolymerization time of 8 h, 0.3 wt % SnO catalyst, and melt copolycondensation for 8 h at 160°C, which gave a novel star‐shaped poly(D,L ‐lactic acid) (PDLLA) modified by CA with the maximum weight‐average molecular weight of 5600 Da at a yield of 51.9%. The copolymer poly(D,L ‐lactide–cholate) at different molar feed ratios was characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, gel permeation chromatography, differential scanning calorimetry, thermogravimetry, and X‐ray diffraction. Decreasing the molar feed ratio of CA/LA from 1/15 to 1/128 reduced the average number of CA units embedded in the copolymer from 4 to 1. With 1/15 CA/LA, the copolymer was not a star‐shaped polymer, and its weight‐average molecular weight was the biggest (weight‐average molecular weight = 12,700 Da, weight‐average molecular weight/number‐average molecular weight = 1.68). With 1/32 CA/LA, the copolymer with two CA units was not a star‐shaped polymer either. With 1/64, 1/100, and 1/128 CA/LA, the copolymer mainly had one CA unit core embedded as a normal star‐shaped PDLLA with four arms, and certain crystallinity could be detected. The novel direct copolycondensation method was simple and practical for the synthesis of the asymmetrical star‐shaped PDLLA material, and it was advantageous for this PDLLA material embedded in the special bioactive molecule CA to be applied in the field of drug delivery and tissue engineering. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Design,optimization and controllability of an alternative process based on extractive distillation for an ethane–carbon dioxide mixture

Alternative configurations based on cryogenic extractive distillation were proposed and simulated by using Aspen Plus 7.0^® coupled to a multi-objective stochastic optimization procedure (differential evolution, DE). The evaluation of the performances of the proposed configurations was focused on the ethane–carbon dioxide azeotrope separation considering different liquefied hydrocarbon fractions as entrainers. The design alternatives were compared to the conventional chemical absorption system.The proposed sequences were simultaneously Pareto optimized by minimizing the total annual cost (TAC) and maximizing the acid gas removal. Complementary studies regarding the theoretical control properties, the thermodynamic efficiency and the greenhouse gases generation were conducted for several representative operating conditions obtained from the Pareto optimized fronts. The proposed cryogenic extractive distillation sequences realized the higher carbon dioxide removal together with the lower TAC compared to the conventional chemical absorption system.     

Fish oil microencapsulation as influenced by spray dryer operational variables

The effects of spray‐drying air temperature, aspirator rate (drying air mass flow rate), peristaltic pump rate (feed mass flow rate) and spraying air mass flow rate on microencapsulation properties of fish oil including moisture content, particle size, bulk density, encapsulation efficiency and peroxide were investigated. The process was carried out on a mini spray dryer, and skim milk powder was used as the encapsulating wall material. Results indicated that increasing inlet air temperature increased the particle size, encapsulation efficiency and peroxide value but decreased the bulk density and moisture content of product. Increasing aspirator rate resulted in increased particle size and peroxide value but decreased the moisture content and bulk density. Increase in feed mass flow rate increased the moisture content, particle size, bulk density and peroxide value but decreased the encapsulation efficiency of microcapsules. The encapsulation efficiency and bulk density increased with the increasing aspirator rate but moisture content, particle size and peroxide value decreased.     

Synthesis,Characterisation, and Evaluation of a Cross-Linked Disulphide Amide-Anhydride-Containing Polymer Based on Cysteine for Colonic Drug Delivery

The use of disulphide polymers, a low redox potential responsive delivery, is one strategy for targeting drugs to the colon so that they are specifically released there. The objective of this study was to synthesise a new cross-linked disulphide-containing polymer based on the amino acid cysteine as a colon drug delivery system and to evaluate the efficiency of the polymers for colon targeted drug delivery under the condition of a low redox potential. The disulphide cross-linked polymers were synthesised via air oxidation of 1,2-ethanedithiol and 3-mercapto-N-2-(3-mercaptopropionamide)-3-mercapto propionic anhydride (trithiol monomers) using different ratio combinations. Four types of polymers were synthesised: P10, P11, P151, and P15. All compounds synthesised were characterised by NMR, IR, LC-MS, CHNS analysis, Raman spectrometry, SEM-EDX, and elemental mapping. The synthesised polymers were evaluated in chemical reduction studies that were performed in zinc/acetic acid solution. The suitability of each polymer for use in colon-targeted drug delivery was investigated in vitro using simulated conditions. Chemical reduction studies showed that all polymers were reduced after 0.5–1.0 h, but different polymers had different thiol concentrations. The bacterial degradation studies showed that the polymers were biodegraded in the anaerobic colonic bacterial medium. Degradation was most pronounced for polymer P15. This result complements the general consensus that biodegradability depends on the swellability of polymers in an aqueous environment. Overall, these results suggest that the cross-linked disulphide-containing polymers described herein could be used as coatings for drugs delivered to the colon.     

无油润滑压缩机设计中的pv值及其应用研究

对无油润滑压缩机设计中的Pv值进行了研究。对活塞环的磨损特性分析表明，pv值越大，活塞环磨损越大、寿命越低。通过pv值的计算推得由pv值和[pu]值来确定活塞环数的计算式。经分析认为一般资料所给活塞环材料的[pv]值过低，所得环数过多，给压缩机在结构尺寸、成本、加工和装配等方面带来问题。推荐了常用无油润滑材料的[pv]值。实际应用表明按推荐值设计的压缩机结构紧凑，活塞环运行寿命达4000h以上。     

Comparative study of the physicochemical and palynological characteristics of honey from Melipona subnitida and Apis mellifera

Twenty‐four samples of Apis mellifera honey and twenty‐four samples of Melipona subnitida (Jandaira) honey were collected in the northeast of Brazil. Moisture, hydroxymethylfurfural, free acidity, insoluble solids in water, diastase activity, ashes, electrical conductivity, proteins, lipids, total carbohydrates, energy and sugars were the parameters analysed. The efficiency of the qualitative tests (Fiehe's test, Lugol's reaction, Lund's reaction) was tested. Pollen types and the corresponding plant species were identified in all samples (3 in Apis and 1 in Melipona). Apis mellifera honey samples demonstrated parameters in accordance with the Brazilian Legislation, while the Melipona subnitida honey samples displayed moisture (24.80%) and diastase activity (null) in discordance with the established by the regulation for Apis mellifera honeys. Apis honey samples presented higher values of electric conductivity (284.00 μS cm^?1) than the obtained from the Jandaira honey samples (102.77 μS cm^?1) as well as a darker colour (26.67 mmPfund) when compared with Jandaira honey (7.00 mmPfund). The concentration of the glucose, fructose and sucrose was higher in the Apis honeys than in the Jandaira honey. The characteristics of the two types of honey were very different, highlighting the need of developing specific legislation for stingless bees' honey.     

Defining complementary tools to the IVI. The Infrastructure Degradation Index (IDI) and the Infrastructure Histogram (HI)

ABSTRACT

The Infrastructure Value Index (IVI) is quickly becoming a standard as a valuable tool to quickly assess the state of urban water infrastructure. However, its simple nature (as a single metric) can mask some valuable information and lead to erroneous conclusions. This paper introduces two complementary tools to IVI: The Infrastructure Degradation Index (IDI) and the Infrastructure Histogram (H_I). The IDI is focused on time (compared to the IVI, focused on value), represents an intuitive concept and behaves in a linear way. The joint analysis of IVI and IDI provides results in a more complete understanding of the state of the assets, while maintaining the simplicity of the tools. The Infrastructure Histogram allows for a full evaluation of the infrastructure state and provides a detailed picture of network age compared to its expected life, as well as an order of magnitude of the required investments in the following years.     

运用价值工程进行设计方案的优选

针对目前建筑工程项目设计中存在浪费大,造价高的现状,提出了运用价值工程进行设计方案优选的方法,从功能分析入手讨论了功能与成本的合理配置,以达到以最小的投入获得最大的功能,从而提高投资效益的目的。