高校改进的学分绩点制模型的探讨

介绍了目前高校学分绩点的计算方式,指出其存在的不足,以某班同学某门课程考试成绩为例说明一般学分绩点和标准学分绩点的缺陷,提出了学分制下较合理的学分绩点度量方法-改进的学分绩点制模型.     

Fabrication and observation of a standard sample for near-field optical microscopy

We fabricated a standard sample for a near-field optical microscope using scanning probe lithography. The sample contains a wedged pattern, which allows the measurement of various sizes within one image. The optical resolution of our near-field optical microscope has been evaluated as 40 nm, which was obtained by measuring the narrowest separable gap width of the wedged pattern. Thus a standard sample containing the wedged pattern enables clear evaluation of the resolution.     

Phase-matching properties of KNbO3 in the mid-infrared

KNbO(3) has been found to be phase matchable for type 1 second-harmonic generation up to 2.4 mum at 22 degrees C. The improved Sellmeier equations that correctly reproduce the nonlinear experiments thus far reported in the literature and our new experimental results for harmonic generation of CO(2) laser harmonics between 3.5303 and 5.2955 mum are presented.     

基于虚拟仪器的某型导弹制导装置地面监测系统设计

针对目前某型导弹制导装置监测方式的落后现状,采用虚拟仪器技术开发了一套地面监测系统;该系统符合某型导弹制导装置的试验标准,是以PXI总线的数据采集卡和控制器为硬件平台,以LabVIEW作为软件开发平台,将采集模拟信号、视频信号和串口通信集于一体,能够对制导装置的性能和参数指标进行检测,并利用图像处理技术对导弹的飞行轨迹进行定性的监测;应用结果,表明该监测系统运行稳定可靠,提高了监测的效率和精度,具有一定的推广价值。     

关于电子商务发展瓶颈问题的探讨

随着信息时代的到来,电子商务的发展已势不可挡,在其快速发展的背后暴露出许多问题,本文从电子商务发展过程中出现的问题入手,分析并探讨解决制约电子商务发展的瓶颈问题。     

Mutation induction in human cells after low dose X ray exposure

Mutations induced after low dose ionising radiation exposure have been intensively analysed not only for radiation risk estimation but also for basic understanding of cellular responses. Human lymphoblastoid TK6-20C cells were irradiated with 100 mGy of X rays and mutation at the heterozygous thymidine kinase (TK) locus was selected by trifluorothymidine (TFT) resistance. Although the mutation frequency at the TK locus increased from 5.6 x 10(-6) to 7.4 x 10(-6), this increase was not statistically significant. However, molecular analysis of TK mutants exhibiting loss of heterozygocity (LOH) demonstrated a clear effect of such low dose IR exposure. Exposure to 100 mGy X ray increased the fraction of hemizygous-LOH from 10% to 42%. In previous experiments, a similar tendency in the increase of hemizygous-LOH was also observed in TK6 cells after exposure to a 2 Gy dose of X rays. This type of LOH can be considered as a result of end-joining repair of DNA double strand breaks.     

Behavioral responses of the ciliated protozoan Paramecium caudatum to 2,4-dichlorophenoxyacetic acid and its analogues

We found that the ciliated protozoan Paramecium caudatum ON-1 was repelled by 2,4-dichlorophenoxyacetic acid (2,4-D). P. caudatum was also repelled by phenoxyacetic acid, while it was attracted to benzoic acid. No significant behavioral response was detected with 2,4-dichlorophenol (2,4-DP) and phenol. These results suggested that the substitution of-OH of phenol with -OCH2COOH, but not the chlorination of phenol, was important for eliciting the avoiding response to 2,4-D in P. caudatum. Electrophysiological analysis revealed that 2,4-D and phenoxyacetic acid were able to trigger the action potential in P. caudatum, whereas 2,4-DP and phenol failed to elicit electrical responses in this organism. Well test assays suggested that the avoiding reactions allowed P. caudatum to escape from the harm caused by this herbicide.     

Hidden Markov model-based prediction of antigenic peptides that interact with MHC class II molecules

Elucidating the interaction between major histocompatibility complex (MHC) molecules and antigenic peptides is fundamental to better understanding of the processes involved in immune responses and for the development of innovative immunotherapies. In the present study, hidden Markov models (HMM) were combined with the successive state splitting (SSS) algorithm for optimization of the HMM structure, to predict peptide binders to the human MHC class II molecule HLA-DRB1*0101. The predictive performance of our model (S-HMM) was compared with fully connected HMM and artificial neural network (ANN) methods using the relative operating characteristic (ROC) analysis. The S-HMM predictions had values of ROC > or = 0.85 which was at least as good, or better than the comparison methods. In addition, S-HMM is trained on positive data only and does not require exhaustive data preprocessing, such as peptide alignment. Our results demonstrated that S-HMM combines the high accuracy of predictions with the simplicity of implementation and is therefore useful for analyzing MHC class II binding peptides. In particular the S-HMM may be trained using only positive data and, the preprocessing of training data, such as peptide alignment and the selection of binding cores, is not required in this method.     

A protein-encapsulation technique by the sol-gel method for the preparation of monolithic columns for capillary electrochromatography

A novel protein-encapsulation technique using sol-gels was developed for the preparation of monolithic capillary columns for capillary electrochromatography. Two chiral compounds, bovine serum albumin (BSA) and ovomucoid (OVM) from chicken egg white, were encapsulated in tetramethoxysilane-based hydrogel and their chiral selectivity was evaluated for the separation of some selected enantiomers (tryptophan, benzoin, eperisone, chlorpheniramine). The protein encapsulation was carried out within a capillary in a single step under mild conditions. The resultant monolithic columns showed adequate chromatographic performance, including mechanical strength, penetration of pressurized flow, and chiral separation. Two different proteins, BSA and OVM, were successfully encapsulated into the gel matrixes by changing the alkoxysilane compositions of the gel. Run-to-run repeatability was quite satisfactory. The consecutive analysis of the neutral compound, benzoin, by the OVM-encapsulated column showed good repeatability in the retention time (RSD = 1.23% for the first peak, N = 10). Under optimized conditions, the theoretical plate number for the first peak of benzoin reached 72,000 plates/m.     

Influence of fabrication errors on wölter mirror imaging performance

The resolution of the W?lter mirror, which is utilized as an objective in soft-x-ray microscopes, is limited by fabrication errors. We studied the relation between fabrication errors and imaging performance of the W?lter mirror to determine how this performance could be improved. Figure errors, which are characterized by low spatial frequency, were analyzed by ray tracing, and surface roughness, characterized by high spatial frequency, was analyzed by modified ray tracing. Modified ray tracing was based on ray tracing but took scattering into account. The results of these analyses were compared with experimental data. As a result, we obtained a simple and practical fabricating tolerance criterion that may be employed to obtain higher W?lter mirror resolution. Additionally, we discuss problems in current W?lter mirror fabrication techniques and the changes that might be made in both the design and the fabrication process to improve imaging performance.