Bayesian latent variable regression via Gibbs sampling: methodology and practical aspects

Bayesian latent variable regression (BLVR) aims to utilize all available information for empirical modeling via a Bayesian framework. Such information includes prior knowledge about the underlying variables, model parameters and measurement error distributions. This paper improves upon the existing optimization‐based BLVR (BLVR‐OPT) method [1] by developing a sampling‐based Bayesian latent variable regression (BLVR‐S) method that relies on Gibbs sampling. Use of the sampling‐based framework not only provides point estimates, but its ability to generate samples that represent the posterior distribution of the unknown variables, also readily provides error bounds. Features and advantages of this method are demonstrated via examples based on simulated data and real Near‐Infrared (NIR) spectroscopy data. Practical aspects of Bayesian modeling such as determining when the extra computation may be worth the effort are addressed by an empirical study of the effects of the amount of training data and signal to noise ratio (SNR). The benefits of BLVR seem to be most significant when the number of measurements is limited and when noise in output variables is relatively large. Copyright © 2007 John Wiley & Sons, Ltd.     

Special aspects of detection methodology in nonaqueous capillary electrophoresis

Over the recent years considerable efforts have been directed to the design of powerful detector arrangements for capillary electrophoresis (CE). The analytical characteristics of the detector have a great influence on the overall analytical performance of CE investigations. The major detection methods in CE, such as UV-Vis absorbance, fluorescence, mass spectrometry and electrochemical detection, have successfully been adapted also to nonaqueous capillary electrophoresis (NACE). However, the different properties of organic solvent systems require some modification of detector concepts and design compared to aqueous CE. The advances of detector development and application in NACE are reported and discussed with emphasis on methodical aspects.     

纳米材料用于放疗防护的研究进展

放射治疗是利用高能射线抑制癌细胞增殖的治疗方法,已广泛用于恶性肿瘤的治疗.但是,高能射线不可避免地会对机体的正常组织造成损害,产生放疗相关副作用.尽管目前有一些小分子放疗防护药物已应用于临床或处于临床前研究,但其较短的血液循环时间和较快的新陈代谢速度极大地削弱了其防护效果.近20年来,随着纳米技术在生物医学领域的飞速发展,纳米放疗防护剂的出现为提高防护效果提供了新的选择.通过合理地设计和开发纳米放疗防护剂,有望解决现有小分子放疗防护药物的缺陷.鉴于纳米放疗防护剂具有诸多优势,本综述概述了纳米放疗防护材料的常见设计策略,同时分析了放射诱导的常见疾病的致病机制和纳米放疗防护材料防治各种放射诱导疾病的研究现状.最后,还讨论了纳米材料用于放疗防护所面临的挑战和未来前景.     

Radioisotope sources for X-ray fluorescence analysis

Problems involved in developing radioisotope sources and the characteristics of potentially useful radioisotopes for X-ray fluorescence analysis are presented. Some of the isotopes, which are not in use but look very promising, are indicated.     

对提高放射性同位素测量精度的研究

为评价放射性同位素测量的精度 ,对美国BeckmanLS 65 0 0ScintillationSystem的单标DPM(SLDPM)和AUTODPM两种猝灭校正方法进行了比较。结果显示 ,SLDPM的猝灭校正范围宽(校正范围由校正曲线决定 ) ,猝灭校正精度高 ,并且可以用于测试双标或三标的样品。使用AU TODPM猝灭校正方法进行测试 ,对于低能β射线3H ,在 90 相似文献   

Radioisotope production at the Kazakhstan cyclotron

Cyclotrons play an important role for production of carrier-free radioisotopes for various applications in the nuclear medicine, industry, ecology and science. Kazakhstan variable energy isochronous cyclotron, K = 50 MeV, is a 150 cm compact-pole 3 sector positive ion machine. It generates different beams of light ions: protons 6-30 MeV, deuterons 12.5-25 MeV, ³He-ions 18.5-62 MeV, alpha-particles 25-50 MeV. In the last years the cyclotron is rather intensively used for radioisotopes production to meet the needs of the Republic of Kazakhstan. The main users of radioisotope products are the Institutions of Healthcare Ministry and enterprises of oil-chemistry, metallurgy, mining, scientific institutes etc. In this submission a survey on radionuclides production including ²⁰¹Tl, ⁶⁷Ga, ⁵⁷Co, ¹⁰⁹Cd, ⁸⁸Y, ⁸⁵Sr is presented. Practically at all production stages (target preparation, extraction, purification and concentration of a product) original approaches were realized: (1) at target production by means of electrolysis the modes of reverse plating of the material for irradiation and technological layers were finalized, and at ⁶⁷Ga production new extraction with better characteristics were used; that made the deeper purification from zinc, copper and iron possible. At the development of the technologies of the sealed sources production the following results were obtained: (1) ¹⁰⁹Cd production for X-ray fluorescence analysis, and production of experimental samples for Mössbauer sources ⁵⁷Co at rhodium and palladium backings. The tracers ²³⁷Pu, ⁸⁸Y and ⁸⁵Sr used for development of the set of methods for ²³⁹Pu, ²⁴⁰Pu, ⁹⁰Sr and ²⁴¹Am determination in the samples from Semipalatinsk Test Site were produced via nuclear reactions with alpha-particles on ²³⁵U and protons on ⁸⁸Sr, ⁸⁵Rb targets. Produced radiopharmaceutical preparations ²⁰¹Tl chloride and ⁶⁷Ga citrate are supplied to medical centers of Almaty.     

Charge strippers for Radioisotope Beam Factory at RIKEN

The accelerator complex at the RIKEN Radioisotope Beam Factory accelerates heavy ions ranging from oxygen to uranium using triple stripping system to provide the beams at required charge. In many cases, the charge strippers cause problems during high-intensity beams accelerator operation. The charge stripper problem has been most significant during uranium beam acceleration because the lifetimes of the conventional carbon foils are extremely short. We conducted extensive R&D on the first stripper and found a solution using a low-Z gas stripper. We also plan to modify a second stripper operating recently with short-lifetime carbon foils. The stripper with better parameters will be needed when the beam intensity is increased by a new injector system for acceleration of uranium beam with higher charge.     

Waste minimization in the Los Alamos Medical Radioisotope Program

Since the mid-1970s the Los Alamos Medical Radioisotope Program has been irradiating target materials to produce and recover radioisotopes for applications in medicine, environmental science, biology, physics, materials research, and other disciplines where radiotracers find utility. By necessity, the chemical processing of targets and the isolation of radioisotopes generates radioactive waste materials. In recent years there have been federal mandates requiring us to discontinue the use of hazardous materials and to minimize radioactive waste volumes. As a result, substantial waste reduction measures have been introduced at the irradiation facility, in processing approaches, and even in the ways the product isotopes are supplied to users.     

Micellar enzymology: methodology and technique

The methodological procedures employed both for serving investigations in the field of micellar enzymology and developed directly in micellar enzymology and being of general significance, such as an estimation of molecular masses and sizes of biocatalysts, titration of active sites of enzymes, chemical modification of proteins (enzymes), conjugation and nanogranulation, are reviewed. Potentialities of using and informativity of various techniques are analyzed.     

Radioprotection by DMSO in nitrogen-saturated mammalian cells exposed to helium ion beams

The contribution of OH radical-mediated indirect action by particle beams under hypoxic irradiation condition was investigated by using a radical scavenger. V79 cells were irradiated with 150 MeV/nucleon helium ions at an LET of 2.2 keV/μm in the presence or absence of DMSO, and their colony survivals were determined. The contribution of indirect action to cell killing under hypoxic condition was estimated to be 52±9%. We conclude that OH radical-mediated indirect action still has a half in total contribution on cell killing under hypoxic condition.     

Radioisotope induced X-ray fluorescence analysis of cereal grains and flour

Radioisotope induced X-ray fluorescence analysis is a rather simple and convenient method for investigating ashed plant material. In order to reduce matrix effects, thin samples (2 mg/cm²) are analyzed to obtain a reasonable compromise between maximum sensitivity and the lowest possible absorption effects. Concentrations are determined by standard addition method. A precision of 6–8% can be achieved. As an application, analytical results are given for whole grains of several sorts of wheat.     

Radioisotope X-ray fluorescence analysis of vanadium in petroleum coke samples

Radioisotope X-ray fluorescence spectrometry, RIXRF, was used for the determination of vanadium in Venezuelan petroleum coke samples using a simple standardless method and fundamental parameter approach. The values obtained by this method were in agreement with values measured by graphite furnace atomic absorption spectrometry, GFAAS.     

Field-flow fractionation: Analytical and micropreparative methodology

Since the introduction of the general concept, field-flow fractionation (FFF) was developed to a complex of separation methods that differ by the fundamental processes underlying and accompanying the separation. In this review, the basic principles on which this separation methodology lies are presented, the most important methods and techniques applicable for analytical and preparative fractionations are described, the first approximation theoretical treatment of the separation processes is outlined, and typical applications for analytical and micropreparative purposes are demonstrated. The main goal is to show that FFF represents an interesting and competitive option of the separation methods applicable in analytical chemistry. The existence of some conflicting opinions concerning the theory as well as the experiments does not prohibit the analytical and preparative use of FFF. If not regarded only as a routine analytical tool, it should stimulate the research and development efforts. On the other hand, when used as an analytical tool, even if the approximate theoretical models are not fully supported by the experiments, the correct analytical result can be obtained from FFF (as well as from any other analytical separation method) by using a calibration procedure and an appropriate treatment and interpretation of the raw experimental data.     

放射性同位素源X射线荧光法测量碘盐中碘含量

介绍用放射性同位素源激发Ｘ射线荧光法测定碘盐中碘的含量。方法简便、无损、快速、准确，可用于碘盐生产的产品质量监控。     

A Radioisotope Flow-Circulation Tracer Method for Determination of Sulfur Uptake and Exchange

A combined radioactive flow-circulation tracer method has been developed and applied to a CoMo/Al₂O₃ catalyst for measurement of sulfur uptakes and of catalyst - gas phase sulfur exchange in the H₂S partial pressure range of 2–47 kPa and the temperature range of 373–673 K. Equilibrium between gas-phase and catalyst sulfur species was rapidly achieved. A substantial part of the sulfur uptake was retained as adsorbed (reversible) sulfur species. The exchange of sulfur increased with increase in temperature up to 573 K and in H₂S partial pressure up to 4 kPa.     

Marine natural products: synthetic aspects

An overview of marine natural products synthesis during 2005 is provided. In a similar vein to earlier installments in this series, the emphasis is on total syntheses of molecules of contemporary interest, new total syntheses, and syntheses that have resulted in structure confirmation or stereochemical assignments.