石墨炉原子吸收光谱法测定健康人和糖尿病人血清中微量铬

本文应用石墨炉原子吸收光谱法对各种石墨管测铬进行了比较。热解石墨管可提供较好的灵敏度(4.86pg/0.0044A)和检出限(0.418μg/L),可用于血清铬的测定。血清样品经HClO_4-H_2O_2-HCl消化处理后,以工作曲线法测定。结果是健康人血清铬为8.16±4.30μg/L(13例),糖尿病人3.10±1.92μg/L(13例)。令人满意。     

A strong limit theorem on gambling systems

A strong limit theorem on gambling system for Bernoulli sequences is extended to the sequences of arbitrary discrete random variables by using the conditional probabilities. Furthermore, by allowing the selection function to take values in an interval, the conception of random selection is generalized. In the proof an approach of applying the differentiation of measure on a net to the investigation of the strong limit theorem is proposed.     

A bayes procedure for selecting the population with the largestpth quantile

Summary The Bayes method is seldom applied to nonparametric statistical problems, for the reason that it is hard to find mathematically tractable prior distributions on a set of probability measures. However, it is found that the Dirichlet process generates randomly a family of probability distributions which can be taken as a family of prior distributions for an application of the Bayes method to such problems. This paper presents a Bayesian analysis of a nonparametric problem of selecting a distribution with the largestpth quantile value, fromk≧2 given distributions. It is assumed a priori that the given distributions have been generated from a Dirichlet process. This work was supported by the U.S. Office of Naval Research under Contract No. 00014-75-C-0451.     

Selection of phage antibodies with GPX activity by combination of phage displayed antibody library with chemical modification and their characterization using a surface plasmon resonance biosensor

Glutathione peroxidase (GPX) is an important antioxidant enzyme, which plays an important role in scavenging reactive oxygen species. To obtain humanized GPX catalytic antibodies, the phage displayed human antibody library on the surface of the filamentous bacteriophage was used to select novel antibodies by repetitive screening. Phage antibodies B8, H6 and C1 with the GSH-binding site were obtained from the library by enzyme-linked immunosorbent assay (ELISA) analysis with four rounds of selection against three haptens, S-2,4-dinitrophenyl t-butyl ester [GSH-S-DNP-Bu (B)], S-2,4-dinitrophenyl t-hexyl ester [GSH-S-DNP-He (H)] and S-2,4-dinitrophenyl cycle-hexyl ester [GSH-S-DNP-cHe (C)], and characterized using surface plasmon resonance (SPR) biosensor. The gold layer was modified by dithiodiglycolic acid (DDA) and three haptens were easily attached to DDA by self-assembling to form a biosensor membrane. The membrane bounds specifically corresponding antibodies. The kinetic process of the reaction between phage antibodies and their haptens was studied by SPR biosensor. In order to improve selectivity, chemical modification was used to incorporate directly catalytic group selenocysteine (Sec) into selected phage clone B8, H6 and C1 to form Se-B8, Se-H6 and Se-C1, respectively. The GPX activities of Se-B8, Se-H6 and Se-C1 were found to be 3000, 2000 and 700 units/μmol, respectively. Compared with conventional ELISA analysis, the proposed method based on SPR biosensor is much more rapid and simpler.     

Determination of volatile halogenated hydrocarbons in tap water,seawater and industrial effluents by glass capillary gas chromatography and electron capture detection

A rapid and sensitive method to determine volatile organohalides in different types of waters has been developed. The chromatographic system is based on the resolving power of the glass capillary column and the high sensitivity of the electron capture detector. The capillary columns were connected to the detector so that the eluate from the column is mixed with thermostatted purge gas to minimize band broadening due to dead volumes. The low column bleeding and decreased band spreading from capillary columns enhance the sensitivity to very low levels: 1 fg (10^?15g) for carbon tetrachloride, despite dilution of the column eluate by the purge gas. The water samples of 100 ml were extracted with 1 to 10 ml n-pentane which is the most practical alkane with respect to purity. When using high water to pentane ratios corrections had to be made, due to low extraction yield, to get accurate quantifications. A column with Carbowax 400 stationary phase permits direct tap water injection. The water peak concealed the substances eluated after CHCl₃ and CHBrCl₂. The gas chromatographic separation of haloforms in tap water could be shortened to 30 seconds using a 10 m SE–52 column with an increased film thickness. Besides tap water and seawater, industrial waste water from a pulp mill was analyzed. Ten different halogenated organic compounds, ranging from 1 ng/I to 760 μg/I, were quantified in the different waters. Bromoform, which had not previously been found in seawater, was detected. Chromatogram of a standard mixture containing 11 organohalides. Stationary phase, SE-52; 33 m × 0.3 mm i.d. inj. temp. 200°, column temp. 50°, interface 250°, detector temp. 250°. Helium carrier gas flow rate, 36 cm/s, scavenger'gas flow 30 ml/min. Split ratio 1:20, 1 = CH₂CI₂, 2 = CHC1₃, 3 = CH₃CC1₃, 4 = CC1₄, 5 = CHCICCI₂, 6 = CHBrCI₂, 7 = CBrC1₃, 8 = CHBr₂Cl, 9 = CCl₂CC1₂, 10 = CHCl₂l, 11 = CHBr₃.     

Individualized configuration selection in CI calculations with subsequent energy extrapolation

A configuration selection method for CI calculations is discussed and applied in which the energy lowering produced in a secular equation by the addition of a given test species to a series of dominant configurations is used as an ordering parameter. Configurations with energy lowerings below a given energy cut-off value are not included in the final secular equations but instead a method of estimating the combined effect of the neglected species on the corresponding non-selected CI results is developed. The influence of the choice of main configurations used in the selection process is given close examination as well as the importance of the MO basis employed in the treatment as a whole; in the latter case a non-iterative procedure for obtaining approximate natural orbitals for such calculations is suggested. The resulting configuration selection procedure is equally applicable to all types of electronic states in any nuclear geometry and the results of the associated CI calculations are seen to be essentially equivalent to a complete treatment in which all single- and double-excitation species with respect to aseries of dominant configurations in a given state are included. Senior U.S. Scientist Awardee of the Alexander von Humboldt Foundation, on leave from the Department of Chemistry, University of Nebraska.     

生物构型对耦合Hindmarsh-Rose神经元系统响应能力的影响

利用Hindmarsh-Rose神经元模型研究了真实的生物细胞连接构型对耦合神经元系统响应能力的影响. 外界刺激信号通过细胞耦合从受刺激的神经元传递到其他神经元,合适的生物构型可以提高系统对刺激信号的响应能力和敏感度;同时,生物构型还会影响神经元系统的同步能力以及选择效应. 模拟的结果可以帮助我们理解面对不同外界刺激,生物体会协调自身结构,选择最佳的构型予以响应.     

An RNA-Cleaving DNAzyme That Requires an Organic Solvent to Function

Engineering functional nucleic acids that are active under unusual conditions will not only reveal their hidden abilities but also lay the groundwork for pursuing them for unique applications. Although many DNAzymes have been derived to catalyze diverse chemical reactions in aqueous solutions, no prior study has been set up to purposely derive DNAzymes that require an organic solvent to function. Herein, we utilized in vitro selection to isolate RNA-cleaving DNAzymes from a random-sequence DNA pool that were “compelled” to accept 35 % dimethyl sulfoxide (DMSO) as a cosolvent, via counter selection in a purely aqueous solution followed by positive selection in the same solution containing 35 % DMSO. This experiment led to the discovery of a new DNAzyme that requires 35 % DMSO for its catalytic activity and exhibits drastically reduced activity without DMSO. This DNAzyme also requires divalent metal ions for catalysis, and its activity is enhanced by monovalent ions. A minimized, more efficient DNAzyme was also derived. This work demonstrates that highly functional, organic solvent-dependent DNAzymes can be isolated from random-sequence DNA libraries via forced in vitro selection, thus expanding the capability and potential utility of catalytic DNA.     

Applications of Michael's selection theorems to fixed point theory

Applying some of Ernest Michael's selection theorems, from recent fixed point theorems on u.s.c. multimaps, we deduce generalizations of the classical Bolzano theorem, several fixed point theorems on multimaps defined on almost convex sets, almost fixed point theorems, coincidence theorems, and collectively fixed point theorems. These results are related mainly to Michael maps, that is, l.s.c. multimaps having nonempty closed convex values.     

Stopping criteria for linesearch methods without derivatives

In this paper acceptability criteria for the linesearch stepsize are introduced which require only function values. Simple algorithm models based on these criteria are presented. Some modifications of criteria based on the knowledge of the directional derivative are also illustrated. This paper was written while this author was visiting CRAI.