Applications of multiwire proportional chambers to time resolved X-ray studies on muscle

Multiwire proportional chambers have been used for making time resolved X-ray diffraction measurements from skeletal muscle. The most useful properties are low noise, high efficiency and fast readout. A number of applications from measurements on skeletal muscle are described.     

Comparison of the performance of the class modelling techniques UNEQ,SIMCA, and PRIMA

Derde, M.P. and Massart, D.L., 1988. Comparison of the performance of the class modelling techniques UNEQ, SIMCA, and PRIMA. Chemometrics and Intelligent Laboratory Systems, 4: 65-93By means of a Monte Carlo study a systematic comparison of the supervised pattern recognition techniques of the class modelling type, UNEQ, SIMCA and PRIMA is made. In particular, the success rate of the classification decisions and the influence of the sample size on it were investigated.It was concluded that better class models are obtained when a technique is used that takes the shape of the population distribution into account. If the actual distribution cannot be determined, then use should be made of techniques that make no or only weak assumptions about the shape of the distribution. However, even then it remains worthwhile to investigate whether the variables are correlated and to take this information into account.When using SIMCA and PRIMA, attention should also be paid to the way the class models are defined: an approach that makes use of certain sample parameters such as the range of the variables or the maximum distance between a training object and the class model might lead to overly broad models, especially for large training sets.     

Chemometrics and intelligent laboratory systems: Information for authors

Research papers and reviews begin with an abstract (50–250 words) which should compromise a brief factual account of the contents of the paper, with emphasis on new information. Abbreviations, jargon and reference numbers must not be used. The abstract should be suitable for use by abstracting services without rewriting.     

A helium-filled time projection chamber for a neutron lifetime measurement

The design and performance of a⁴He-filled TPC, constructed to measure the neutron half-life, are described. Preliminary results obtained with radioactive sources and with a chopped neutron beam are discussed.     

A scanning and data acquisition system for the Lund proton microprobe

A computer system for scanning control and the evaluation of data obtained using a scanning proton microprobe is described. The system consists of a μVax-II host computer and a VME bus data acquisition and beam scanning system. The VME bus computer controls the front-end electronics, such as ADCs, and sends data in blocks to the μVax-II which does the on-line sorting of data and elemental mapping. To facilitate fast and effective analyses, a software package has been developed which gives the user the possibility of manipulating data acquisition, beam scanning etc. during sample analysis.     

酶法破壁提取蜂花粉功能成分的工艺优化及抗氧化活性分析

目的 探索酶解结合超声和碱解从而高效破壁和提取蜂花粉中的活性成分。方法 采用扫描电镜对蜂花粉微观结构进行分析,并使用高效液相色谱法分析酚类物质的组成和含量变化。结果 经12.5%碱性蛋白酶酶解1 h后,蜂花粉可溶出部分的总酚、总黄酮和ABTS抗氧化值都达到最高值,分别为14.14±0.23 mg GAE/g dw, 2.34±0.04 mg RE/g dw和167.06±1.39 mg μM TE/g dw。将酶解辅以超声协同0.3 mol/L NaOH处理后,总酚、总黄酮、ABTS自由基清除能力及铁离子还原能力相比未处理花粉分别提高了191%、39%、69%和162%。扫描电镜结果显示,碱处理酶解后花粉细胞壁破碎程度显著增加,花粉内含物质从裂口处向外溢出,与理化指标趋势一致。最佳工艺条件为0.3 M NaOH超声-碱处理1 h,调节pH至7,12.5%的碱性蛋白酶于50℃下酶解1h。结论 超声碱处理可辅助酶解实现蜂花粉的高效破壁,同时小肽、多酚、黄酮等营养成分也进一步溶出,促进了蜂花粉的高值化利用。     

Intramolecular charge-transfer fluorescence as a mobility probe in poly(methylmethacrylate)

The (time-resolved) fluorescence spectra of 1-phenyl-4-(4-cyano-1-naphthylmethylene)piperidine (1) have been measured during the polymerization of methylmethacrylate (MMA). It was found that the fluorescence maximum of 1 shows a large hypsochromic shift as polymerization of the MMA medium progresses. While the emission maximum is located at 565 nm in the monomer, it is found at 450 ± 5 nm in the polymer (PMMA). The polarization of the fluorescence increases strongly during the polymerization, indicating that the rotational motion of 1 ceases on the timescale of the fluorescence lifetime (about 10 ns). Fluorescence measurements performed with a detection time delay with respect to the exciting laser pulse showed that within the time range 0–100 ns the molecule 1 undergoes reorientation and/or internal relaxation even in a PMMA matrix; a red shift of the emission with time occurs, together with a decrease of the degree of fluorescence polarization.     

The luminescence of magnesium tungstate dihydrate,MgWO4·2H2O

The luminescence of MgWO₄.2H₂O contains two emission bands, one due to the tungstate tetrahedron, and another one related to the hydrate group. The former is compared with the tungstate luminescence of anhydrous MGWO₄.     

Transportation interface facilities design using interactive high-level computer graphics

A prototype pedestrian facilities design system is described. The design system exploits the capabilities of an intelligent high-resolution vector graphics workstation which features a highly interactive computer graphics environment. A summary of historical developments in pedestrian facility design and graphics workstation architecture is presented, followed by a discussion of the stochastic model and interactive computer graphics features utilized by a prototype facilities design system. Potential applications of such a design system are discussed, and promising areas of future development are outlined.