石蜡微胶囊中脲醛树脂壁材渗透性的研究

利用差示扫描量热法研究了石蜡微胶囊中脲醛树脂壁材对水及甲苯的渗透性 ,结果表明 ,水不能透过脲醛树脂壁材 ,而甲苯则易透过脲醛树脂壁材。因此 ,该石蜡微胶囊不能用于芳香族溶剂存在的场合。     

A 0.25-/spl mu/m CMOS quad-band GSM RF transceiver using an efficient LO frequency plan

This paper describes a single-chip CMOS quad-band (850/900/1800/1900 MHz) RF transceiver for GSM/GPRS applications. It is the most important design issue to maximize resource sharing and reuse in designing the multiband transceivers. In particular, reducing the number of voltage-controlled oscillators (VCOs) required for local oscillator (LO) frequency generation is very important because the VCO and phase-locked loop (PLL) circuits occupy a relatively large area. We propose a quad-band GSM transceiver architecture that employs a direct conversion receiver and an offset PLL transmitter, which requires only one VCO/PLL to generate LO signals by using an efficient LO frequency plan. In the receive path, four separate LNAs are used for each band, and two down-conversion mixers are used, one for the low bands (850/900 MHz) and the other for the high bands (1800/1900 MHz). A receiver baseband circuit is shared for all four bands because all of their channel spaces are the same. In the transmit path, most of the building blocks of the offset PLL, including a TX VCO and IF filters, are integrated. The quad-band GSM transceiver that was implemented in 0.25-/spl mu/m CMOS technology has a size of 3.3/spl times/3.2 mm/sup 2/, including its pad area. From the experimental results, we found that the receiver provides a maximum noise figure of 2.9 dB and a minimum IIP3 of -13.2dBm for the EGSM 900 band. The transmitter shows an rms phase error of 1.4/spl deg/ and meets the GSM spectral mask specification. The prototype chip consumes 56 and 58 mA at 2.8 V in the RX and TX modes, respectively.     

低压16.5万m~3干式气柜采用城市煤气直接置换的方法

青岛市管道燃气公司在大尧罐站对低压16．5万m3干式气柜采用城市燃气直接置换，经合理确定置换范围，标准及过程，成功地进行了低压16．5万m3干式气相及其管道采用城市煤气直接置换的操作。     

Is electrogastrography a substitute for manometric studies in children with functional gastrointestinal disorders?

We performed simultaneous fasting and fed antroduodenal manometry and EGG in 25 children with functional bowel disorders. Three patients (12%) had an uninterpretable EGG. The manometric studies showed severe neuropathy in six patients; milder neuropathic changes in five patients; postprandial hypomotility in one patient; myopathy in four patients, and normal motility in the remaining six patients. The percentage of tachygastria time (frequency > 3.5 cycles/min) was higher in the patiens with mild (44.1 +/- 15.8%) and severe (48 +/- 19.1%) neuropathy than in the patients with myopathy (20 +/- 16.2%, P < 0.05) or with normal motility (23 +/- 13.3%, P < 0.05). There was a considerable overlap in the percentage of tachygastria and total arrhythmia time among the different study groups. The ratio of post- to preprandial power was significantly higher (2.5 +/- 0.07) in children with normal motility than in the other patients groups. Every child with total arrhythmia time < 35% and a ratio of post- to preprandial power > 2.4 had normal manometry. In summary, EGG differentiated groups of children with normal manometry from others with neuropathic or myopathic changes, but in a minority of patients the study was not interpretable and there was overlap in EGG results between children with normal and abnormal manometry.     

Changes in the orientation of the smooth-muscle cells of the tunica media from major arteries under constant lengthwise stretching in situ

It has been shown that changes in the orientation of arterial smooth muscle cells during a constant longitudinal stretching of the artery in vivo are not similar in different sections of the stretching zone. Cells in the proximal and distal sections keep their orientation but this orientation differs from that of smooth muscle cells in the control arteries. Cells in the central part of the stretching region lose their definite orientation to settle randomly.     

PET／PC共混物的辐射效应研究

研究了经溶液共混制备的聚对苯二甲酸乙二醇酯／聚碳酸酯（ＰＥＴ／ＰＣ）共混物的辐射效应。结果表明：ＰＥＴ／ＰＣ共混物在辐照过程中未发生酯交换反应和交联反应，但有降解反应发生。在研究的剂量范围内，辐照对ＰＥＴ／ＰＣ共混物中ＰＥＴ和ＰＣ的晶体形态影响不明显。     

Mutational analysis of the pea phytochrome A chromophore pocket: chromophore assembly with apophytochrome A and photoreversibility

Ten site-specific mutants of pea apophytochrome A were expressed in Saccharomyces cerevisiae and analyzed for chromophore assembly with apoprotein and photoreversible absorbance changes. The mutants constitute two specific changes for each of five conserved amino acid residues located in the microenvironment of the chromophore attachment residue, which is Cys-323 in pea phytochrome A. All mutant apophytochromes were autocatalytically able to covalently attach phycocyanobilin, indicating that there were no major structural perturbations in the apoproteins. However, the rate of chromophore ligation varied significantly among the mutants. Spectrally, the mutant holophytochromes are of three types: mutant phytochromes that are indistinguishable from the wild-type adduct, mutants with blue-shifted Pr and Pfr absorption maxima compared to the wild-type adduct, and mutants that are not photoreversible. From an analysis of the results, we concluded that the residues Asp-309, Arg-318, His-321, and Gln-326 are probably not catalytically involved in the chromophore ligation reaction, but some residues may play significant structural and stereochemical roles. Arg-318 might anchor the chromophore, as has been suggested [Partis, M. D., & Grimm, R. (1990) Z. Naturforsch, 45c, 987-998; Parker, W., et al. (1993) Bioconjugate Chem. (in press)]. The conserved Gln-326, three residues downstream from the chromophore attachment site, is not electrostatically critical for the spectral integrity and photoreversibility of phytochrome, but this residue is sterically important to the lyase activity. It appears that the role of the five amino acid residues in the N- and C-terminal vicinities of the chromophore binding Cys-323 is structural rather than catalytic for the ligation reaction.     

混酸PEG酯的合成及性能研究

用从大豆油脚水解制得的脂肪酸合成混酸聚乙二醇酯，通过测定酸值的方法确定了最佳反应时间为16h。与油酸聚乙二醇酯相比，混酸聚乙二醇酯具有更优良的乳化性、润湿性，可以替代油酸聚乙二醇酯用于纺织、农药和化妆品工业中。