Genetic risks to man from exposure to long-lived radionuclides

Ionizing radiation, irrespective of whether it is received from external sources or from internally-deposited radionuclides, is capable of causing genetic damage that will be transmitted from one generation to the next. Since strictly relevant human data is limited at present, there is no alternative to the use of data collected in experimental mammals for estimating genetic risks associated with the exposure of human populations to ionizing radiation.Animal studies reveal that plutonium reaching the testes and concentrates in the interstitial tissue but is later aggregated by macrophages, apparently leading to a reduction in effectiveness. For protracted alpha irradiation from testicular plutonium in the mouse, the RBE (relative biological effectiveness) for genetic effects of concern may be in a range of between 10 and 20, relative to chronic gamma irradiation. In female mice, plutonium appears to be much less effective although the data is very limited.Studies with beta emitters provide reasonable grounds for believing that in the case of chronic exposures to tritium, the RBE value may be about 2, whereas for others such as carbon-14, it may not be significantly different from unity.These and other results support the view that for plutonium alpha rays, the genetic risks following exposure of human males may be 10–20 times that estimated for chronic, low level, low LET irradiation, per unit absorbed testicular dose; for tritium exposures, the risks may be higher by a factor of 2, (again, relative to chronic gamma ray exposures) while for carbon-14, the risks are the same as that for chronic gamma irradiation. For estimating genetic risks following exposure of human females to radionuclides, in the absence of adequate data, it would be prudent to assume that the risks will be similar to those for irradiation of males.     

How to Persuade Undergraduates to Use Chemical Graph Theory

New techniques are presented that permit the use of chemical graph theory to obtain secular equations for small molecules. The new techniques significantly accelerate manual calculations. A previously unrecognized relationship between the characteristic polynomial for a Hückel annulene and the secular equation for the corresponding Mobius annulene is deduced. The power of the graph-theoretical approach to illuminate chemically useful generalizations at the Hückel level is exemplified.     

Hair analysis as a new tool to monitor adherence to long-term therapy to statins

Statins are cholesterol-lowering medications which are widely prescribed as first-line treatment for hyperlipidemia, against high blood cholesterol aimed at reducing the risk of atherosclerotic diseases. Notwithstanding their undoubted efficacy, the needed long-term treatment with these drugs is characterized by a high percentage of dropout. Consequently, an effective tool to verify the patients’ compliance to statin therapy is needed. In this context, the analysis for drugs and drug metabolites in the hair may represent an almost ideal tool because, according to a sound body of forensic toxicological literature, concentrations in the hair matrix reflect the chronic intake of drugs and pharmaceuticals. In this light, in the present study, a novel, specific and sensitive ultra-performance liquid chromatography–tandem mass spectrometry method has been developed to determine six statins and their metabolites (namely atorvastatin, (p)α-OH-atorvastatin-lactone, (o)α-OH-atorvastatin-lactone, rosuvastatin, N-desmethyl rosuvastatin and pravastatin) in human hair. After optimization, the method was successfully validated in terms of selectivity, linearity, sensitivity, precision, accuracy, stability and matrix effect. Moreover, the practical applicability of this method for verifying adherence to statin therapy was assessed by testing samples of hair collected from subjects under long-term therapy with statins.     

How to Use Visual Basic to Interface Scientific Instruments to a Personal Computer

Computer-controlled instruments are expensive and for this reason are not widely used in student laboratories. In this paper we describe how to interface a data-acquisition board using Microsoft Visual Basic. Visual Basic can be used to quickly develop an application in the Microsoft Windows environment. A single computer system can serve as several different measuring systems by simple adaptation of the software.     

Adhesion to mineralized tissue: Bonding to human dentin

We consider the conditions and demonstrable reactions which promote chemical bonding to human dentin. The desirability of developing durable adhesion to dentin is used as background for a discussion of feasible reactions to the dentin components, for possible use in new formulations. This is followed by a discussion of the demonstrable reactions found in the literature, as well as our own surface-sensitive IR work on the reaction between dentin protein and 2-hydroxyethyl methacrylate, an ingredient found in proprietary tissue replacement formulations.     

Electrochemical Reduction of Carbon Dioxide to Ethanol: An Approach to Transforming Greenhouse Gas to Fuel Source

Converting carbon dioxide (CO₂) into high-value fuels or chemicals is considered as a promising way to utilize CO₂ and alleviate the excessive greenhouse gas emission. Among multiple catalysis approaches, electrochemical reduction of CO₂ to ethanol has an important prospect due to the high energy density and widely applications of ethanol. In recent years, many electrocatalysts for CO₂ reduce reaction (CO₂RR) have shown promising catalytic activity for ethanol production. In this review, we will introduce the recent progress in this field. The basic principles and electrochemical performances of CO₂RR are reviewed at first. Then, several categories of active electrocatalysts for CO₂RR to ethanol are summarized, including the discussion of reaction mechanism and catalytic sites. Finally, several possible strategies are proposed, providing guidance for future design and preparation of high-performance catalysts.     

An Alternative to the Sandmeyer Approach to Aryl Iodides

Iodoarenes are important synthons for a wide range of organic transformations. Here we report a general strategy to prepare singly iodinated electron‐rich aromatic compounds through the intermediacy of diaryliodonium salts. This process, which incorporates a phase separation that greatly simplifies product purification, is an attractive replacement for the Sandmeyer approach to iodoarenes that are otherwise difficult to access.     

Utilization of thermodesorption coupled to GC-MS to study stability of different wood species to thermodegradation

Thermodesorption coupled to gas chromatography coupled to mass spectroscopy (TD-GC-MS) has been investigated to identify volatile degradation products generated during wood heat treatment by mild pyrolysis. For this purpose, wood samples of different softwood and hardwood species have been heat treated under nitrogen for different temperatures comprised between 180 and 230 °C during 15 min in the glass thermal desorption tube of the thermodesorber and the volatile wood degradation products trapped. The trapped products were then thermodesorbed and analysed by GC-MS. Chromatograms of the different samples indicated the formation of different products resulting from degradation of lignin and hemicelluloses. Hardwoods were shown to be more sensitive to thermodegradation than softwoods, for which degradation products appear at slightly higher temperature. The important formation of acetic acid is concomitant with the formation of most of degradation products and at the origin of the difference of reactivity observed between softwoods and hardwoods.     

Access to Enantiopure Advanced Intermediates en Route to Madangamines

The synthesis of enantiopure ABCE and ABCD tetracyclic advanced intermediates en route to madangamine alkaloids and studies for the construction of the triunsaturated 15-membered D ring of madangamine B and the saturated 13-membered D ring of madangamine E are reported.     

Muonium atom addition to pyridine and to the pyridinium cation

Muonium atoms are found to add mainly to the N-atom and to the ortho and meta positions in pyridine in almost equal amounts, giving pyridinyl and 2-azacyclohexadienyl radicals and 3-azacyclohexadienyl radicals, respectively (no addition was observed at the para site); on protonation, as in a sample of PyH⁺ BF₄⁻, the reactivity follows the positive charge density, being enhanced for addition to the N(H⁺) position, reduced for the ortho/meta positions, and now conferring a significant yield of the para isomer. These results for genuine reactions of hydrogen atoms are discussed in view of studies of radical formation in these materials, made using EPR spectroscopy, when they are exposed to γ-rays in cryogenic matrices, for which mechanisms involving charge-neutralization of initial radical ions are proposed. Copyright © 2001 John Wiley & Sons, Ltd.     

Dielectric approach to polystyrene microcapsule analysis and the application to the capsule permeability to potassium chloride

A method of numerical analysis is proposed to determine the phase parameters from dielectric observations of polystyrene microcapsules by using the conductivity at intermediate frequencies between two dielectric relaxations observed. The method was more feasible for the analysis of the microcapsule observations than the method by which the calculation is performed by use of the permittivity at lower frequencies. The method was applied to the dielectric observations of the KCl-loaded microcapsules to obtain the permittivity and the conductivity of the capsule interior, the thickness of the capsule wall, the volume fraction of the suspended capsules and the conductivity of the surrounding aqueous phase. The conductivity of capsule interior was found to be unchanged with time for as long as 3 months. From the results it is concluded that the microcapsules are impermeable to KCl.     

Heat transfer to a single particle exposed to a thermal plasma

This paper is concerned with an analytical study of the heat and mass transfer process of a single particle exposed to a thermal plasma, with emphasis on the effects which evaporation imposes on heat transfer from the plasma to the particle. The results refer mainly to an atmospheric-pressure argon plasma and, for comparison purposes, an argon-hydrogen mixture and a nitrogen plasma are also considered in a temperature range from 3000 to 16,000 K. Interactions with water droplets, alumina, tungsten, and graphite particles are considered in a range of small Reynolds numbers typical for plasma processing of fine powders. Comparisons between exact solutions of the governing equations and approximate solutions indicate the parameter range for which approximate solutions are valid. The time required for complete evaporation of a given particle can be determined from calculated values of the vaporization constant. This constant is mainly determined by the boiling (or sublimation) temperature of the particles and the density of the condensed phase. Evaporation severely reduces heat transfer to a particle and, in general, this effect is more pronounced for materials with low latent heat of evaporation.     

Electron attachment to higher fullerenes and to Sc3N@C80

We report on attachment of free electrons to fullerenes C(n) (n = 60, 70, 76, 78, 80, 82, 84, 86) and to Sc(3)N@C(80). The attachment cross sections exhibit a strong resonance at 0 eV for all species. The overall shape of the anion yield versus electron energy is quite similar for the higher fullerenes, with a minimum around 1 eV and a maximum which gradually shifts from 6 eV for C(60) to approximately 4 eV for large n. The endohedral Sc(3)N@C(80) exhibits a particularly shallow minimum and a maximum below 4 eV. We model autoionization of the anions with due consideration of the internal energy distributions. The relatively low electron affinity of Sc(3)N@C(80) is reflected in its reduced ion yield at higher attachment energies.     

PNA to DNA to microarray decoding facilitates ligand discovery

The development of a method for the amplification of PNA tags (Svensen et al., in this issue of Chemistry & Biology) should expand the range of biological targets amenable to screening using PNA-encoded combinatorial libraries and thus facilitate the discovery of new biologically useful agents.     

Contribution to cyclotron targetry

Experimental methods for distribution and quantification of activity in a neon target bombarded by deuteron particles are presented and evaluated. Optimum target handling for medical radionuclide applications is important for achieving high yields, high specific activity, and a low rate of radiocontaminants with a minimum of cyclotron beam time. The mechanism of activity distribution and its importance are studied in relation to other considerations necessary for optimizing gas target performance in radiopharmaceutical applications.     

Long-chain branching in free-radical polymerization due to chain transfer to polymer

The Monte Carlo sampling technique is used to investigate the branched structure formation during free-radical polymerization that involves chain transfer to polymer. This method accounts for the history of the generated branched structure and can provide virtually any structural information, because one can observe each polymer molecule directly. In this paper, we investigate the whole molecular weight distribution (MWD) for both pre- and postgelation periods, the MWDs for polymer molecules containing 0, 1, 2, 3, … branch points, the branching density of polymer molecules as functions of both size and the number of branch points, the spatial distribution of the branched chains at the theta state, etc. Contrary to the term ‘long-chain’ branching, many branch chains are relatively small, and the branched structures formed are significantly different from those usually depicted to introduce ‘branched polymers’ in many introductory textbooks. The radii of gyration at the theta state can be approximated by the Zimm-Stockmayer equation for random branching, in spite of various violations against the assumptions used in deriving the equation © 1995 John Wiley & Sons, Inc.     

Correction to Microscopically Determined Particle Size According to Diffraction Correction Theory

The theory of diffraction correction for transparent (phase) spherical particles under partially coherent illumination has been applied to the optical photomicrographic determination of particle size distribution for four different nearly monodisperse polystyrene latex samples. The thus corrected particle size distribution for each sample has been compared with the corresponding electron microscopic determination. Copyright 1999 Academic Press.     

电化学发光分析法测定糖尿病相关二肽

将纳米金粒子负载于氧化铟锡导电玻璃(ITO)表面作为电化学发光(ECL)工作电极,建立了简单、快速测定二肽的方法.采用透射电镜、扫描电镜、电化学和光谱等技术方法表征材料和所制备电极的性能.在最优条件下,组氨酸-丙氨酸二肽分子(His-Ala)对鲁米诺在此电极上的ECL有显著的猝灭作用,从而可以对二肽进行检测.在2.44×10-11~1.22×10-7 mol/L浓度范围内,ECL响应和二肽浓度有良好的线性关系,检出限为2.42×10-12 mol/L(S/N=3).人体内胰高血糖素样肽-1(GLP-1)在二肽基肽酶IV(PDD-IV)作用下失去活性并释放出同量的His-Ala二肽,因此,本方法可通过测定血液中二肽浓度间接测定GLP-1,以及评估PDD-IV和其抑制剂的活性.上述DPP-IV抑制剂可调节2型糖尿病人血液GLP-1在正常水平,是糖尿病研究和治疗中具有潜在价值的药物设计靶点.     

Smooth relativistic Hartree-Fock pseudopotentials for H to Ba and Lu to Hg

We report smooth relativistic Hartree-Fock pseudopotentials (also known as averaged relativistic effective potentials) and spin-orbit operators for the atoms H to Ba and Lu to Hg. We remove the unphysical extremely nonlocal behavior resulting from the exchange interaction in a controlled manner, and represent the resulting pseudopotentials in an analytic form suitable for use within standard quantum chemistry codes. These pseudopotentials are suitable for use within Hartree-Fock and correlated wave function methods, including diffusion quantum Monte Carlo calculations.