Modeling the early stages of thin film formation by energetic atom deposition

The early stages of thin film formation are described by a simple hybrid model that couples a set of discrete kinetic rate equations to a Fokker-Planck (FP)-type continuum. Unique features of the atomic processes in energetic particle deposition are outlined and discussed. A thermal atom deposition process is benchmarked with Zinsmeister’s analytical theory^[17] to demonstrate the simplicity and accuracy of the model. This simplicity allows extensions to the treatment of energetic particle effects and the growth of multilayers of atoms. It is shown that the model explains the major features of the early stages of atomic clustering. This paper is based on a presentation made in the symposium “Irradiation-Enhanced Materials Science and Engineering” presented as part of the ASM INTERNATIONAL 75th Anniversary celebration at the 1988 World Materials Congress in Chicago, IL, September 25-29, 1988, under the auspices of the Nuclear Materials Committee of TMS-AIME and ASM-MSD.     

导电银浆低温固化薄膜的制备与导电性能

用银粉作为导电填料,与F型环氧树脂、稀释剂、固化剂等配制成树脂基导电银浆,将导电银浆印刷在载玻片上,在一定温度下固化后得到导电银浆固化膜。通过对薄膜体积电阻率进行测定,以及SEM观察和傅里叶变换红外光谱分析,研究稀释剂种类、稀释剂含量、固化温度和固化时间等因素对导电银浆固化薄膜结构与电阻率的影响。结果表明:松油醇对导电银浆稀释效果好,得到附着力和硬度均较高的固化膜,松油醇含量(质量分数)为8%时,薄膜的体积电阻率达到3.9×10~(-5)?·cm;提高固化温度可降低薄膜的体积电阻率,但温度超过130℃时,电阻率降低不明显;延长固化时间可提高银浆薄膜的导电性能,但当时间达到40 min后,电阻率基本不再随时间延长而发生变化。     

Study and characterization of different developmental stages of Leishmania major

The complete developmental cycle of Leishmania major in axenic culture was achieved by simply changing the temperature whether sudden from 22 degrees C to 37 degrees C or stepwise 22 degrees C, 29 degrees C and then 37 degrees C. The morphology by light microscopy, GPI isoenzyme pattern and PCR amplification of minicircle of kinetoplast DNA of the different stages were studied. The amastigotes obtained from the foot pads of mice were compared to those obtained from axenic culture. The GPI isoenzyme pattern and the PCR amplification products showed distinct differences between the promastigotes and the amastigotes. The amastigotes of the two sources also showed differences after temperature changes.     

氧化钨物理特征的分析

对铵钨青铜((NH_4)_(0.5)WO_3,ATB)、氢钨青铜(H_(0.33)WO_3,HTB)、紫色氧化钨(W_(18)O_(49),TVO)和蓝色氧化钨(WO_3+WO_(2.9),TBO)4种氧化钨粉的氮气吸附/脱附等温线数据的分析,获得了其表面积、微孔体积、微孔分布、中孔体积、平均孔径和分数维维数等物理参数。结果表明:TVO粉末具有最大的中孔体积、最小的微孔体积、最窄的孔径分布、最小的分数维维数和最大的平均孔径,有利于氢还原制取超细钨粉,而不利于掺杂工艺。HTB粉末具有最大的微孔体积,最宽的孔径分布,最高的分数维维数和最小的平均孔径,对于掺杂工艺来说是有利的。ATB和TBO的上述参数介于TVO和HTB的参数之间。     

Viral characterization by direct analysis of capsid proteins

Matrix-assisted laser desorption/ionization mass spectrometry has enabled viral coat proteins to be characterized directly from the virus. This analysis, demonstrated here with tobacco mosaic virus U2, a bacteriophage MS2, and equine encephalitis TRD, is achieved with a combination of organic acid, UV-absorbing matrix, and high-energy desorption with a nitrogen laser. The molecular weights of these proteins are determined with sufficient accuracy to allow differentiation among viral species and strains. The abundant hydrophobic MS2 coat protein was analyzed in aliquots of culture medium and of the tobacco mosaic virus coat protein in infected leaves. This method provides rapid detection of coat protein in the low-femtomole range, as estimated by titering plaque-forming units of MS2.     

Isolation and physical characterization of random insertions in Staphylococcal nuclease

Using genetic engineering techniques we generated randomly located internal tandem duplications of random size within Staphylococcal nuclease. Those insertions, possessing greater than 0.1% of normal activity, were sequenced and characterized physically. Insertions were found to begin and end in regions possessing secondary structure as well as in regions without secondary structure. All proteins remained folded and monomeric, although one mutant appeared, by both circular dichroism and size exclusion chromatography, to be partially unfolded. The stability of the insertions as assayed by guanidine hydrochloride denaturation ranged from nearly normal to destabilized by almost 4 kcal per mol. The activities of the insertion mutants ranged from 1/30 to 1/2000 of the parental nuclease.     

Preparation and characterization of gelatin/cerium(III) film

A novel gelatin film with antibacterial activity was prepared by electrostatic crosslinking using cerium (III) nitrate hexahydrate as the crosslinking agent. The structure and properties of the films were investigated by Fourier transform infrared spectra, tensile tests, thermogravimetric analysis, static drop contact angle and disc diffusion method. The results showed that cross-linking could not only improve the thermal and mechanical properties and lower the hydrophilic property of the films, but also make them exhibit strong antibacterial activity against Escherichia coli.     

Preparation and characterization of gelatin/cerium(Ⅲ) film

A novel gelatin film with antibacterial activity was prepared by electrostatic crosslinking using cerium (Ⅲ) nitrate hexahydrate as the crosslinking agent. The structure and properties of the films were investigated by Fourier transform infrared spectra, tensile tests, thermogravimetric analysis, static drop contact angle and disc diffusion method. The results showed that cross-linking could not only improve the thermal and mechanical properties and lower the hydrophilic property of the films, but also make...     

理化检测数据的多元回归分析

结合韶钢实际情况,开发了理化检测数据多元回归分析计算机应用程序.此程序可定量分析钢材机械性能与化学成分之间的关系,为质量管理者提供了一种有力的质量分析工具.     

Investigation of the early stages of deformation of two phase copper-aluminum alloys

A study has been made of the early stages of deformation of a series of two phase (α + β′) Cu-Al alloys in terms of the behavior of the constituent phases. The two phase structures of constant martensite andα phase composition with varying amount of martensite phase are obtained by quenching from the two phase field. By being able to measure the strength of theα andβ′ phases individually in the two phase alloys by microhardness measurements, it is possible to study the individual constituent behavior in the presence of one another. It is found that the work hardening rate of two phase alloys is controlled mainly by the work hardening rate of the softerα phase in the two phase alloys. The significance of the observationsvis-a-vis the law of mixtures is considered.     

Brain tumor segmentation and characterization by pattern analysis of multispectral NMR images

A major problem in tumor treatment planning and evaluation is determination of the tumor extent. This paper presents a pattern analysis methodology for segmentation and characterization of brain tumors from multispectral NMR images. The proposed approach has been used in 15 clinical studies of cerebral tumor patients who have been scheduled for surgical biopsy and resection. The tissue biopsy results, obtained at specific spatial coordinates determined in the analysis, have been utilized to validate the methodology. It was found that in all cases the lesion had extended into normal tissue, at least to the location where the sample was taken. In most cases, the proposed method suggested that the lesion had extended several millimetres beyond the point from where the biopsy sample was taken. In some cases, the extent of the lesion into normal tissue was well beyond the boundary seen on T1- or T2-weighted images. It is concluded that the proposed approach indicates brain tumor infiltration more precisely than what is visualized in the original NMR images and therefore its utilization facilitates proper treatment planning for the cerebral tumor patients.     

化学镀铜表面烷基膦酸自组装单分子膜的制备及表征

通过脉冲恒电位强化技术,在新生的化学镀铜样品表面上制备了烷基膦酸自组装单分子膜,测试了自组装单分子膜的电化学和谱学特性,以及润湿性变化规律。结果表明在1%烷基膦酸溶液,脉冲恒电位强化制备的自组装膜腐蚀电流较空白样品下降了98.4%,反应阻抗值相应增加,其自组装膜抑制了铜电极腐蚀反应的阳极过程,使得控制步骤由氧的扩散转变为界面电荷转移;FT-IR检测证实了样品表面成功组装了烷基膦酸单分子膜,脉冲恒电位强化处理的对应吸收峰相对较大;接触角测试间接印证了烷基膦酸已组装成膜,样品表面的润湿性由亲水性转为疏水性,脉冲恒电位强化处理后自组装单分子膜的接触角θ增加了39°,说明脉冲恒电位强化使组装膜更为致密。      

Isolation and characterization of murine clonogenic osteoclast progenitors by cell surface phenotype analysis

MHC class I molecules bind short peptides for presentation to CD8+ T cells. The determination of the three-dimensional structure of various MHC class I complexes has revealed that both ends of the peptide binding site are composed of polar residues conserved among all human and murine MHC class I sequences, which act to lock the ends of the peptide into the groove. In the rat, however, differences in these important residues occur, suggesting the possibility that certain rat MHC class I molecules may be able to bind and present longer peptides. Here we have studied the peptide length preferences of two rat MHC class Ia molecules expressed in the TAP2-deficient mouse cell line RMA-S: RT1-A1c, which carries unusual key residues at both ends of the groove, and RT1.Aa which carries the canonical residues. Temperature-dependent peptide stabilization assays were performed using synthetic random peptide libraries of different lengths (7-15 amino acids) and successful stabilization was determined by FACS analysis. Results for two naturally expressed mouse MHC class I molecules revealed different length preferences (H2-Kb, 8-13-mer and H2-Db, 9-15-mer peptides). The rat MHC class Ia molecule, RT1-Aa, revealed a preference for 9-15-mer peptides, whereas RT1-A1c showed a more stringent preference for 9-12-mer peptides, thereby ruling out the hypothesis that unusual residues in rat MHC molecules allow binding of longer peptides.     

辉光放电光谱法分析掺杂纳米硅薄膜的研究

介绍了利用辉光放电光谱法分析掺杂纳米硅薄膜通过优化辉光光源激发参数、计算标准样品的溅射率,建立了掺杂纳米硅薄膜的定量表面分析方法.方法应用于实际掺杂纳米硅薄膜样品的分析,并将分析深度剖析结果与表面形貌仪的结果进行了对照.实验结果表明,本分析方法快速、准确,具有实际应用价值.     

Morphological and physical characterization of the capsular layer of Vibrio cholerae O139

Low-speed isokinetic exercise has been recommended to exert a maximal contraction and produce greater muscle torque than high-speed exercise in young adults. The purpose of this study was to compare the effectiveness of low- and high-speed isokinetic exercise programs for increasing muscle torque in young and elderly people. Twenty healthy elderly and 20 young subjects participated. The elderly subjects were divided into two groups. One group performed high-speed (300 degrees/s) isokinetic exercise training three times a week for the dominant-side knee extensor and low-speed (60 degrees/s) exercise for the non-dominant side for 6 weeks. The other group was trained using the reverse exercise regime. The training program for the young subjects was the same as that for the elderly groups. All subjects had their knee extensor torque evaluated with an isokinetic test before and at 2-week intervals during the training program. For young and elderly groups, both high- and low-speed isokinetic exercise training increased extensor torque in low- and high-speed tests. For the young group, low-speed exercise effectively improved muscle torque at low and high speeds. The improvement in slow muscle torque was significantly greater than that in fast muscle torque. For the elderly subjects, high-speed isokinetic exercise produced the greatest muscle torque at high speed in the first 2 weeks of training, and demonstrated a sharp increase in muscle torque in the final 2 weeks. Low-speed exercise frequently caused knee stress and the inability of some elder subjects to continue the exercises with maximal effort. Our findings indicate that high-speed exercise may be more appropriate for the elderly, and low-speed exercise may be more appropriate for younger people.