Estimating material elasticity by spherical indentation load-relaxation tests on viscoelastic samples of finite thickness

A two-step viscoelastic spherical indentation method is proposed to compensate for 1) material relaxation and 2) sample thickness. In the first step, the indenter is moved at a constant speed and the reaction force is measured. In the second step, the indenter is held at a constant position and the relaxation response of the material is measured. Then the relaxation response is fit with a multi-exponential function which corresponds to a three-branch general Maxwell model. The relaxation modulus is derived by correcting the finite ramp time introduced in the first step. The proposed model takes into account the sample thickness, which is important for applications in which the sample thickness is less than ten times the indenter radius. The model is validated numerically by finite element simulations. Experiments are carried out on a 10% gelatin phantom and a chicken breast sample with the proposed method. The results for both the gelatin phantom and the chicken breast sample agree with the results obtained from a surface wave method. Both the finite element simulations and experimental results show improved elasticity estimations by incorporating the sample thickness into the model. The measured shear elasticities of the 10% gelatin sample are 6.79 and 6.93 kPa by the proposed finite indentation method at sample thickness of 40 and 20 mm, respectively. The elasticity of the same sample is estimated to be 6.53 kPa by the surface wave method. For the chicken breast sample, the shear elasticity is measured to be 4.51 and 5.17 kPa by the proposed indentation method at sample thickness of 40 and 20 mm, respectively. Its elasticity is measured by the surface wave method to be 4.14 kPa. © 2011 IEEE.

Effect of amino acids on cryopreservation of cynomolgus monkey (Macaca fascicularis) sperm

The effects of three amino acids (proline, glutamine, and glycine) added to the freezing medium Tes-Tris-egg yolk (TTE) for cryopreservation of cynomolgus monkey (Macaca fascicularis) spermatozoa were studied. This is the first report on the effects of amino acids on nonhuman primate sperm cryopreservation. The addition of 5 mM proline, 10 mM glutamine, and 10 or 20 mM glycine each significantly improved post-thaw sperm motility and membrane and acrosome integrity compared with the control (TTE alone). However, a significant decrease in motility and membrane/acrosome integrity was observed when amino acid concentrations increased to 60 mM for proline and glutamine, and 80 mM for glycine. The results suggest that adding a limited amount of amino acids to the freezing media is beneficial for freezing cynomolgus monkey sperm.

Study on the reproductive biology of Pinctada fucata (Gould) (Mollusca: Pteriidae)

Annual cycle of gonad development and spawning in pearl oyster, Pinctada ficata (Gould) in Nakhiloo, Northeast Persian Gulf, was investigated over two years from August 1994 to June 1996. Gonadal condition was assessed by staging criteria to describe gametogenic development from histological preparations of randomly collected individuals of all sizes. A bimodal gametogenic pattern with summer and autumn spawning periods was evident throughout the study. Gametogensis commenced in November-December which proceeded by major gonadal maturation during February-April. Summer spawning was observed from April to July with major spawning at the latter end. During spawning peak in July, low level of gametogensis was noticed. Gametogenic activity was picked up again in August-September which proceeded by autumn spawning from September to December. Towards the end of spawning season, incidence of gonadal inactivation increased. Minimum level of gonadal activity was observed in November. Temperature regime appears to have influential role in regulation of gametogenic and spawning processes. Gonadal development and spawning trends were similar in both sexes. P. radiaata was found to be protandrous hermaphrodite which matured as a male at shell height greater than 20 mm. Biseivality was uncommon and the sex ratio was about 1:1. Ultrastructure of gametes were investigated in the Pictada fucata (Gould). "Auxiliary cells" closely accociated with developing oocytes were observed. Each oocyte seems to be associated with only one secretory cell. which is characterized by an abundant rough endoplasmic reticulum at the onset of vitellogenesis. Contact between this cell and a developing oocytes is maintained by a desmosome-like junction which can be observed when the vitelline coat is formed. these "auxiliary or nursing cells" seem to play a tropic role in vitellogenesis, and may be involved in the formation of the vitelline coat of the oocytes. Oocytic degeneration is observed in this species, it is a continuous phenomenon of varing intensity throughout the year. The ultrastructural changes resulting in lysis of the oocyte are described. Mature spermatozoa consist of a broad, cap-shaped acrosomal vesicle, subacrosomal material, a round nucleus, two triplet substructure centrioles surrounded by four spherical mitochondria, and a flagellum anchored to the distal centriole and plasma membrane. Spermatozoa of Plucata closley resemble to those of other investigated Pteriidae. Changes in proximate composition of soft tissue and gonadal cycle of Pinctada fucata was studied. Mobilization and utilization of stored reserves are apparent during gametogenesis and gonadal maturation. Protein reserves are utilized during spermatogenesis while reserved carbohydrates form the main energy donor in oogenesis. The role of lipid as am.: energy reserve is second to that of carbohydrate.

Two-port InGaAsP/InP square resonator microlasers

Two-port InGaAsP/InP square resonator microlasers with a side length of 20 mm have been fabricated by the planar technology process, which have two 1 mu m-wide output ports connected to the vertices of the square resonator. Continuous-wave electrically injected microsquare lasers have been realised at room temperature with mode Q-factors of 1.75 x 10(4) at the threshold current.

H+ISFET-based biosensor for determination of penicillin G

A biosensor based on an H+ ion sensitive field effect transistor (H+-ISFET) and penicillin G acylase has been developed. The response time of the sensor to different concentrations of penicillin G was 30 s. In a 20 mM phosphate buffer at pH 7.0, the linear range of the calibration curve was from 0.5 to 8 mM. The coefficients of variation for three samples with 20 repeated measurements were below 5%. Stability of the sensor could reach about 6 months and more than 1000 runs were performed without a significant decrease of the output value. The sensor was tested for measurement of the penicillin G content in penicillin fermentation broth. Forty samples with low and high concentrations of penicillin G were chosen for the correlation test. The values assayed by the sensor method were compared with the values assayed by HPLC method, the correlation coefficient (r) was 0.9944 and the regression equation was y = 1.034X - 2083.7 respectively. The different measuring methods are discussed in the text. (C) 1998 Published by Elsevier Science S.A. All rights reserved.

Chaotic behavior of pulsating heat pipes

Chaotic behavior of closed loop pulsating heat pipes (PHPs) was studied. The PHPs were fabricated by capillary tubes with outer and inner diameters of 2.0 and 1.20 mm. FC-72 and deionized water were used as the working fluids. Experiments cover the following data ranges: number of turns of 4, 6, and 9, inclination angles from 5 degrees (near horizontal) to 90, (vertical), charge ratios from 50% to 80%, heating powers from 7.5 to 60.0 W. The nonlinear analysis is based on the recorded time series of temperatures on the evaporation, adiabatic, and condensation sections. The present study confirms that PHPs are deterministic chaotic systems. Autocorrelation functions (ACF) are decreased versus time, indicating prediction ability of the system is finite. Three typical attractor patterns are identified. Hurst exponents are very high, i.e., from 0.85 to 0.95, indicating very strong persistent properties of PHPs. Curves of correlation integral versus radius of hypersphere indicate two linear sections for water PHPs, corresponding to both high frequency, low amplitude, and low frequency, large amplitude oscillations. At small inclination angles near horizontal, correlation dimensions are not uniform at different turns of PHPs. The non-uniformity of correlation dimensions is significantly improved with increases in inclination angles. Effect of inclination angles on the chaotic parameters is complex for FC-72 PHPs, but it is certain that correlation dimensions and Kolmogorov entropies are increased with increases in inclination angles. The optimal charge ratios are about 60-70%, at which correlation dimensions and Kolmogorov entropies are high. The higher the heating power, the larger the correlation dimensions and Kolmogorov entropies are. For most runs, large correlation dimensions and Kolmogorov entropies correspond to small thermal resistances, i.e., better thermal performance, except for FC-72 PHPs at small inclination angles of theta < 15 degrees.

相似性降水条件下北洛河水沙变化特征

降水是河流径流来源也是水土流失的主要动力,通过选择相似降水年组比较河流水沙变化,可以更好揭示土地利用变化对河流水沙变化的影响。采用1954年到1996年北洛河状头水文站实测资料,根据年份差大于5年,年雨量差小于20 mm和汛期雨量差小于10 mm等三个指标确定了8个相似降水年组。通过比较相似性降水年组径流量和输沙量变化,分析了不同时间河流水沙变化特点;并通过组间比较初步探讨了北洛河水沙变化趋势。分析表明,与1980年相比,1996年除汛期径流量增加外,年径流量,年与汛期的输沙量和含沙量均增加;在其他时段,输沙量在1970年代后期以前呈减少趋势,年径流量和汛期径流量有增加趋势,而年均和汛期含沙量均有减少趋势。

稀土催化剂合成窄分子量分布聚异戊二烯的研究

本论文利用传统的稀土催化剂组成，探讨了稀土催化剂的配制方式，配制出稳定的均相催化剂；深入探讨了影响聚异戊二烯分子结构的因素，合成了高顺式、高分子量、窄分子量分布且具有与天然橡胶相似的拉伸结晶特点的聚合物；讨论了催化剂活性中心的形成机理；均相催化剂用于丁二烯-异戊二烯共聚合可制备窄分子量分布的无规共聚物。 1. NdCl3•3iPrOH/MMAO催化体系：可在较低的MMAO (Al/Nd < 40)用量下，高收率地合成高的顺式-1,4含量(> 96%)、非常高的分子量(Mn > 100×104)、相当窄的分子量分布(Mw/Mn < 2.0)的聚异戊二烯。与烷基铝助催化剂如Al(i-Bu)3和Al(i-Bu)2H相比，在顺-1,4含量相同的情况下，MMAO体系所得聚合物的分子量最高，分子量分布最窄。催化剂形成配位阳离子性质的活性中心。 2. Nd(vers)3/Al(i-Bu)2H/Al(i-Bu)2Cl催化体系：可在适当的陈化条件下配制出稳定的均相催化剂，该均相催化剂可在较低的Al/Nd用量(Al/Nd = 10)和催化剂用量([Nd] = 0.20 mM)下，高收率(> 80%)地合成高顺式-1,4含量(> 96%)、高分子量(Mn > 50×104)、窄分子量分布(Mw/Mn < 3.0)的聚合物。均相催化剂的活性中心为配位阳离子性质的单活性中心。 3. Nd(vers)3/MMAO/Al(i-Bu)2H/Al(i-Bu)2Cl催化体系：在相当低的MMAO用量(Al/Nd = 10，总铝量Al/Nd = 20)下，仍具有高的催化活性，所得聚合物的分子量较高(Mn 52.4×104)，分子量分布较窄(Mw/Mn < 3.0)，顺-1,4结构含量可达96%。通过调节Al(i-Bu)2H和MMAO用量可以控制聚合物的分子量及分子量分布。 4. Nd(vers)3/Al(i-Bu)3/Al(i-Bu)2Cl催化体系：用Al(i-Bu)3代替Al(i-Bu)2H作助催化剂，可在各种加料方式下高收率地获得高顺-1,4含量(96%)、非常高分子量(Mn > 100×104)、窄分子量分布(Mw/Mn < 3.0)的聚异戊二烯，且所得异戊橡胶在高顺-1,4含量(96%)、高分子量(Mn ≥ 90×104)、窄分子量分布(Mw/Mn ≤ 2.1)时存在拉伸结晶现象，性能接近甚至超过天然橡胶。 5. Nd(vers)3/AlR3(Al(i-Bu)2H, Al(i-Bu)3)/Al(i-Bu)2Cl催化体系在一定条件下，可获得高顺式-1,4含量(丁二烯和异戊二烯的顺-1,4含量均可达99.9%)、高分子量(Mn > 50×104)、窄分子量分布(Mw/Mn < 3.0)的丁二烯-异戊二烯共聚物。只是用Al(i-Bu)3作助催化剂时，均相和非均相催化剂均可得到高顺式、更高分子量(Mn > 100×104)、更窄分子量分布(Mw/Mn < 1.8)的共聚物。两单体的竞聚率为：对于Al(i-Bu)2H体系，rBD = 0.923，rIP = 0.612；对于Al(i-Bu)3体系，rBD = 1.02，rIP = 0.919。表明聚合物为无规共聚物。

Study on conical columns for semi-preparative liquid chromatography

The dynamic flow profiles and column efficiencies in conically shaped semi-preparative liquid chromatographic columns (inlet ID larger than outlet ID) with two different conical angles (7degrees and 15degrees) were studied. The dynamic flow profiles were studied by an on-column visualization method. Conical columns were compared with cylindrical column of the same length and internal volume. The results showed that the flow profile of a sample band in the conical column of 7degrees (50 mm x 17 mm --> 11 mm ID) was parabolic in shape. The sample band migrated slower in the wall region than in the central region, as in the cylindrical column (50 mm x 14 mm ID). However, the sample band in the conical column of 15degrees (50 mm x 20 mm --> 7 mm ID) migrated slower in the central region than in the wall region, resulting in a reverse parabolic flow profile, in contrast to that in cylindrical column. This indicated that a flat flow profile might be realized in a conical column with a conical angle between 7degrees and 15degrees. The conical column of 15degrees had the highest column efficiency among the three columns under the same conditions. Compared with the cylindrical column packed with identical packing material, the conical column of 15degrees had 22%-45% higher column efficiency and 11%-27% higher peak height.

Determination of arsenic species by capillary zone electrophoresis with large-volume field-amplified stacking injection

Determination of arsenic species by large-volume field amplified stacking injection-capillary zone electrophoresis (LV-FASI-CZE) is reported in this paper. Whole column injection was employed. The optimum buffer pH for the separation of weak acids was discussed. It was found that the optimum buffer to analyze the stacked arsenate (As(V)), monomethylarsonate (MMA), and dimethylarsinate (DMA) was 25 mm phosphate at pH 6.5. However, the optimum buffer to analyze the concentrated arsenite (As(III)) was 20 mm phosphate - 10 mm borate at pH 9.28. The limits of detection of the method developed were 0.026 mg/L for As(III), 0.023 mg/L for As(V), 0.043 mg/L for MMA, and 0.018 mg/L for DMA. An enrichment factor of 34-100 for several arsenic species was obtained. In the end, this method was applied to determine the arsenic concentration in the environmental reference materials to show the usefulness of the method developed.

Microchip Micellar Electrokinetic Chromatography Based on One Functionalized Ionic Liquid and Its Excellent Performance on Proteins Separation

Herein, one water-soluble functionalized ionic liquid (IL), 1-butyl-3-methylimidazolium dodecanesulfonate (BAS), was designed, investigated and successfully applied to microchip micellar electrokinetic chromatography (MEKC) construction. It possessed the properties of both IL and surfactant. A fairly stable pH value similar to 7.4, which was fit to pH values of general biological buffers, was nicely placed at the optimum concentration of 20 mM BAS solution. While applying BAS solution as running buffer in poly(dimethylsiloxane) (PDMS) microfluidic systems, significantly enhanced electroosmotic flow (8-fold) and resolutions between analytes were obtained than that using other supporting electrolytes or surfactants.

Studies of the intermolecular DNA triplexes of C+center dot GC and T center dot AT triplets by electrospray ionization Fourier-transform ion cyclotron resonance mass spectrometry

Formation and stabilities of four 14-mer intermolecular DNA triplexes, consisting of third strands with repeating sequence CTCT, CCTT, CTT, or TTT, were studied by electrospray ionization Fourier-transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) in the gas phase. The gas-phase stabilities of the triplexes were compared with their CD spectra and melting behaviors in solution, and parallel correlation between two phases were obtained. In the presence of 20 mm NH4+ (pH 5.5), the formation of the TTT triplex was not detected in both solution and the gas phase.

Highly ordered mesoporous carbons-based glucose/O-2 biofuel cell

This study demonstrates a novel compartment-less glucose/O-2 biofuel cell (BFC) based on highly ordered mesoporous carbons (OMCs) with three-dimensionally (3D) interconnected and ordered pore structures. OMCs are used as supports for both stably confining the electrocatalyst (i.e., meldola's blue, MDB) for NADH oxidation and the anodic biocatalyst (i.e., NAD(+)-dependent glucose dehydrogenase, GDH) for glucose oxidation, and for facilitating direct electrochemistry of the cathodic biocatalyst (i.e., laccase, LAC) for O-2 electroreduction. In 0.10 M pH 6.0 PBS containing 20 mM NAD(+) and 60 mM glucose under the air-saturated atmosphere, the open circuit voltage (0.82 V) and the maximum power output (38.7 mu W cm(-2) (at 0.54V)) of the assembled compartment-less OMCs-based BFC are both higher than those of carbon nanotubes (CNTs)-based BFC (0.75 V and 2.1 mu W cm(-2) (at 0.46 V)).

Glutathione-capped CdTe quantum dots for the sensitive detection of glucose

A simple and sensitive assay system for glucose based on the glutathione (GSH)-capped CdTe quantum dots (QDs) was developed. GSH-capped CdTe QDs exhibit higher sensitivity to H2O2 produced from the glucose oxidase catalyzed oxidation Of glucose, and are also more biocompatible than other thiols-capped QDs. Based on the quenching of H2O2 on GSH-capped QDs, glucose can be detected. The detection conditions containing reaction time, the concentration of glucose oxidase and the sizes of QDs were optimized and the detection limits for glucose was determined to be 0.1 mu M; two detection ranges of glucose from 1.0 mu M to 0.5 mM and from 1.0 mM to 20 mM, respectively Were obtained. The detection limit was almost a 1000 times lower than other QDs-based optical glucose sensing systems. The developed glucose detection system was simple and facile with no need of complicated enzyme immobilization and modification of QDs.

CE with electrochemical detection for investigation of label-free recognition of amino acid amides by guanine-rich DNA aptamers

In this work, we report a simple and effective investigation into adaptive interactions between guanine-rich DNA aptamers and amino acid amides by CE with electrochemical (EC) detection. Argininamide (Arm) and tyrosinamide (Tym) were chosen as model molecules. On a copper electrode, Arm generated a good EC signal in 60 mM NaOH at 0.7 V (vs Ag/ AgCl), while Tym. was detected well on a platinum electrode at 1. 3 V in 20 mM phosphate of pH 7.0. Based on their EC properties, the ligands themselves were used as indicators for the adaptive interactions investigated by CE-EC, making any step of labeling and/or modification of aptamers with indicators exempted. Hydrophilic ionic liquid was used as an additive in running buffer of CE to improve the sensitivity of Arm detection, whereas the additive was not used for Tym. detection due to its negative effect. Two guanine-rich DNA aptamers were used for molecular recognition of Arm and Tym. When the aptamers were incubated with ligands, they bound the model molecules with high affinity and specificity, reflected by obvious decreases in the signals of ligands but no changes in those of the control molecules. However, the ligands were hardly affected by the control ssDNAs after incubation. The results revealed the specific recognition of Arm and Tym. by the aptamers.