bluuebunny/crossref_metadata_2025 huggingface dataset:
Monocyclic and cascade rearrangements of furoxans
Authors: Makhova N. N. , Ovchinnikov I. V. , Kulikov A. S. , Molotov S. I. , Baryshnikova E. L.
Published: October 2007

Monocyclic rearrangements of azoles are extensively studied as alternative methods for the preparation of new heterocyclic systems. The present work is devoted to investigation of monocyclic and cascade rearrangements of 1,2,5-oxadiazole 2-oxide (furoxan) derivatives. It was found during investigations that rearrangements of furoxan ring had some peculiarities in comparison with analogous rearrangements of other azoles. Therefore, three different kinds of rearrangements were found. The first of them occurred through a dinitroso-ethylene intermediate and resulted in the synthesis of 1,2,3-triazole 1-oxides [oximes of 5-acetyl-4-phenyl(methyl)-2-phenyl-2H -1,2,3-triazole 1-oxides and 2-(furoxan-4-yl)-4-nitro-5-R-2H -1,2,3-triazole 1-oxides ]by thermal recyclization accordingly of 3-methyl-4-acetyl(benzoyl)furoxans phenylhydrazones and 3,3'-(R)-disubstituted-4,4'-azofuroxans. The latter reaction was performed in an oxidizing medium. The second kind of rearrangement (classical variant) was the synthesis of new azoles containing the 1-nitroalkyl substituent. These rearrangements were performed using three examples: base-induced interconversion of furoxanyl ketone phenylhydrazones into 5-(1-nitroalkyl)-2H-1,2,3-triazole derivatives and of 1-alkyl(aryl)-3-(furoxan-4-yl)amidines into 1-substituted 3-(1-nitroalkyl)-1,2,4-triazoles as well as a thermally induced rearrangement of 4-thioureido-3-R-furoxans into derivatives of 5-amino-3-(1-nitroalkyl)-1,2,4-thiadiazole including (5-amino-1,2,4-thiadiazol-3-yl)nitro-formaldehyde arylhydrazones (where R =N=N –Ar). Rearrangements of the third kind were those of the cascade type. Three new cascade rearrangements of azofuroxan derivatives [3,3'-azo-4,4'-bis(acetylamino)furoxans, 3-arylazo-4-acetylaminofuroxans, and 3-arylazo-4-(3- ethoxycarbonylureido)furoxans] into 4-amino-5-nitro-2H-1,2,3-triazole derivatives were discovered. These three reactions were assumed to include two consecutive (cascade) rearrangements: a 1,2,4-oxadiazole ring was formed at the first step and then transformed into a 1,2,3-triazole ring with the participation of an azo group.
New schemes for the synthesis of glycolipid oligosaccharide chains
Authors: Nifantiev N. E. , Sherman A. A. , Yudina O. N. , Cheshev P. E. , Tsvetkov Y. E. , Khatuntseva E. A. , Kornilov A. V. , Shashkov A. S.
Published: October 2007

The driving force for the constant improvement and development of synthetic methodologies in carbohydrate chemistry is the importance of natural oligosaccharide chains in numerous biological phenomena such as cell growth, differentiation, adhesion, etc. Here, we report our syntheses of the spacer-armed oligosaccharides of sialylated lacto- and neo- lacto-, globo-, ganglio-, and sulfoglucuronylparagloboside-series, which include new rationally designed synthetic blocks, efficient solutions for the stereoselective construction of glycosidic bonds, and novel protection group strategies.
Superheavy elements
Authors: Oganessian Yu. Ts.
Published: October 2007

One of the fundamental outcomes of nuclear theory is the predicted existence of increased stability in the region of unknown superheavy elements. This hypothesis, proposed more than 35 years ago and intensively developed during all this time, significantly extends the limits of existence of chemical elements. “Magic ”nuclei with closed proton and neutron shells possess maximum binding energy. For the heaviest nuclides, a considerable stability is predicted close to the deformed shells with Z = 108, N = 162. Even higher stability is expected for the neutron-rich nuclei close to the spherical shells with Z = 114 (possibly also at Z = 120, 122) and N = 184, coming next to the well-known “doubly magic ”nucleus 208 Pb. The present paper describes the experiments aimed at the synthesis of nuclides with Z = 113–116, 118 and N = 170–177, produced in the fusion reactions of the heavy isotopes of Pu, Am, Cm, and Cf with 48Ca projectiles.The energies and half-lives of the new nuclides, as well as those of their daughter nuclei (Z < 113) qualitatively agree with the theoretical predictions. The question, which is the nucleus, among the superheavy ones, that has the longest half-life is also considered. It has been shown that, if the lifetime of the most stable isotopes, in particular, the isotopes of element 108 (Hs), is ≥ 5 ×107 years, they can be found in natu ral objects. The experiments were carried out during 2001–2003 in the Flerov Laboratory of Nuclear Reactions (JINR, Dubna) in collaboration with the Analytical and Nuclear Chemistry Division (LLNL, Livermore).
Ecologically benign motor fuels and petrochemicals from alternative raw materials
Authors: Rozovskii A. Y. , Slivinskii E. V. , Lin G. I. , Makhlin V. A. , Kolbanovsky Y. A. , Platé N. A.
Published: October 2007

Physicochemical foundations of various processes which comprise the single stages of natural gas processing into motor fuels are considered. Among them are: novel process of syngas production by methane reforming using rocket technology, direct dimethyl ether synthesis from syngas and its conversion into the ecologically benign gasoline, an advanced technology of methanol synthesis, as well as methanol transformation into pure hydrogen, Fischer–Tropsch synthesis with increased selectivity. New developments made by the Topchiev Institute of Petrochemical Synthesis Russian Academy of Sciences (TIPS RAS) in this field are discussed. In this light, the achievement of a global goal, to make synthetic motor fuels cheaper than their oil counterparts, appears to be a solvable task for the nearest future.
Fundamental chemical features of complex manganites and cuprates for advanced functional materials engineering
Authors: Tretyakov Yu. D. , Goodilin E. A.
Published: October 2007

The existence of a tide relationship between fundamental chemical properties of either copper or manganese as 3d transition elements and advanced functional properties of related oxide materials is demonstrated using original experimental results. The complex role of ionic sizes, oxidation and spin states, and Jahn–Teller distortions is discussed in terms of the influence of these phenomena on the crystal structure, phase assemblage, microstructure, and physical properties of three key classes of modern copper- and manganese-containing materials (high-temperature superconductors, colossal magnetoresistive compounds, and 1d superionics), bringing up innovation technologies in electrical power engineering, micro- electronics, spintronics, magnetic field sensing, electrode materials, and fuel cells.
Stoichiometric and catalytic CO2 reductions involving TiFe-containing intermetallic hydrides
Authors: Tsodikov M. V. , Kugel V. Ya. , Yandieva F. A. , Mordovin V. P. , Gekhman A. E. , Moiseev I. I.
Published: October 2007

Thermoprogrammed desorption of H2 from [TiFe0.95Zr0.03Mo0.02]H2 showed two forms of absorbed hydrogen. The first one is evolved from the intermetallic hydride under heating up to 185 °C under Ar (loosely bound hydrogen, LBH). The second portion of H2 (strongly bound hydrogen, SBH) remains in the intermetallic hydride up to 700–920 °C. SBH reacts with CO2 to give CO rather selectively (80–99 %) at CO2 conversion of 50–70 % at 350 –430 °C and 10 –12 atm. Dehydrogenation of cyclohexane coupled with CO2 hydrogenation into CO predominantly proceeds efficiently in the presence of the intermetallic hydride [TiFe0.95Zr0.03Mo0.02]Hx (where x = 0.1) in a combination with industrial Pt/Al2O3 catalyst. Aliphatic primary alcohols undergo oxidation by CO2 forming aldehydes in the presence of [TiFe0.95Zr0.03Mo0.02]H0.36. Conversion of the alcohols into alkanes with carbon skeleton counting at least doubled carbon number in comparison with parent alcohol was found to be catalyzed by the mixture of the last intermetallic hydride and Pt/Al2O3 catalyst.
Postgenomic chemistry: New problems and challenges
Authors: Varfolomeyev S. D. , Aliev T. K. , Efremenko E. N.
Published: October 2007

New trends in chemistry induced by genetic engineering and genomic information are analyzed. Genomic information and bioinformatics make the identification of all molecular participants of biological processes possible. The methods of identification of enzyme-active sites from sequence data were demonstrated. The problems of "chemical proteomics" were formulated and analyzed. New biocatalytic processes based on a new generation of enzymes, including CO2 reduction and enzyme fuel cell construction, are demonstrated. It was shown that in many reactions the enzymes are substantially more efficient in comparison with classical chemical catalysts. The creation of recombinant proteins from unnatural amino acids is demonstrated, and organisms containing such proteins are described. The new trends of proteomics and bioanalytical chemistry in the postgenomic era are discussed.
Properties and units in the clinical laboratory sciences. Part XVIII. Properties and units in clinical molecular biology (IUPAC Technical Report)
Authors: de Araujo P. Soares , Zingales Bianca , Alía-Ramos Pedro , Blanco-Font Aurora , Fuentes-Arderiu X. , Mannhalter Christine , Varming K. , Bojesen Stig , Bruunshuus Ivan , Olesen H.
Published: October 2007

This document describes the introduction of the concept of property in the field of molecular biology for the presentation of results of clinical laboratory investigations of genes and mutations. It follows the IUPAC–IFCC systematic rules and attempts to create a common base for communication between the clinical laboratory sciences, the medical practitioner, and the molecular biology areas of knowledge.

Because of the plethora of possible structural variations in the outcome of analysis, the designation of components is restricted to the symbols of genes as identified by the Human Genome Nomenclature Database (HUGO). The listing of properties having DNA as system comprises all symbols in the HUGO database except for symbols related to mitochondrial genes, while properties having RNA as system are included only when known to be in actual use. The detailed and accurate presentation of results is made by the laboratory performing the study, and it is recommended that the explicit guidelines given by Antonarakis and den Dunnen be adhered to.

For electronic communication, a code (NPU) is allocated to each property identified. The complete list of properties, which is an integral part of this report, can be accessed at .
Building a molecular-level picture of the ultrafast dynamics of the charge-transfer-to-solvent (CTTS) reaction of sodide (Na¯)
Authors: Martini I. B. , Barthel E. R. , Schwartz B. J.
Published: October 2007

Charge-transfer-to-solvent (CTTS) reactions represent the simplest possible electron-transfer reaction. One of the reasons that such reactions have become the subject of recent interest is that transfer of a CTTS electron from an atomic anion to the solvent involves only electronic degrees of freedom, so that all the dynamics involved in the reaction are those of the solvent. Thus, CTTS reactions provide an outstanding spectroscopic window on the dynamics of the solvent during electron transfer. In this paper, we will review our recent work studying the CTTS reaction of the sodium anion, (Na− or sodide) in a series of ether solvents. By comparing the results of ultrafast spectroscopic pump/probe experiments and mixed quantum/classical molecular dynamics simulations, we work to build a molecular-level picture of how solvent motions control the dynamics of CTTS, including the distance to which the electron is ejected and the rates of both the forward and back electron-transfer reactions.
Past, present and futute of cyclodextrin research
Authors: Szejtli J.
Published: October 2007

The macrocyclic cyclodextrins (enzymic conversion products of starch) were discovered in 1891, and the structures were elucidated in the mid-1930s. Their industrial significance become obvious in the 1970s, and by now thousand of tons of the three cyclodextrins (alpha-, beta-, and gamma-CD) and of their chemical derivatives and inclusion complexes are produced industrially. The outer surface of these doughnut-shaped molecules is hydrophilic, but they possess an axial open cavity, which is of hydrophobic character and capable of including other apolar molecules (or their moiety) in case of geometric compatibility. This is the essence of molecular encapsulation by inclusion complex formation.
From molecular modules to modular materials
Authors: Kurth D. G. , Liu Shaoqin , Volkmer D.
Published: October 2007

The combination of metallosupramolecular modules (MEMOs) as functional and amphiphiles as structural components is presented in detail to illustrate our current understanding of encapsulation using surfactants, lipids, and dendrimers. The simplicity of fabrication and the availability of the starting components allow this technique as an attractive tool to create new nanoscale molecular materials. The interaction of amphiphiles and MEMOs occurs spontaneously and is driven by the release of counterions as well as electrostatic and hydrophobic interactions.
Acid-base properties of purine residues and the effect of metal ions: Quantification of rare nucleobase tautomers
Authors: Sigel H.
Published: October 2007

The macro acidity constants valid for aqueous solutions of several adenine, guanine,and hypoxanthine derivatives are summarized. It is shown how the application of the corresponding constants, e.g., for 7,9-dimethyladenine, allows a quantification of the intrinsic acidic properties of the (N1)H0/+ and (N7)H+ sites via micro acidity constants, and how to use this information for the calculation of the tautomeric ratios regarding the monoprotonated species, that is, N7-N1*H versus H*N7-N1, meaning that in one isomer H+ is at the N1 site and in the other at N7. It is further shown that different metal ions coordinated to a given site, e.g., N7, lead to a different extent of acidification, e.g., at (N1)H; the effect decreases in the series Cu2+>Ni2+>Pt2+ ~Pd2+. Moreover, the application of micro acidity constants proves that the acidifications are reciprocal and identical. This means, Pt2+ coordinated to (N1)–/0 sites in guanine, hypoxanthine, or adenine residues acidifies the (N7)H+ unit to the same extent as (N7)-coordinated Pt 2+ acidifies the (N1)H0/+ site. In other words, an apparently increased basicity of N7 upon Pt2+ coordination at (N1)–/0 sites disappears if the micro acidity constants of the appropriate isocharged tautomers of the ligand are properly taken into account. There is also evidence that proton–proton interactions are more pronounced than divalent metal ion–proton interactions, and that these in turn are possibly larger than divalent metal ion–metal ion interactions. The indicated quantifications of the acid-base properties are meaningful for nucleic acids including the formation of certain nucleobase tautomers in low concentrations, which could give rise to mutations.
Molecular devices
Authors: Balzani Vincenzo , Ceroni Paola , Ferrer Belén
Published: October 2007

The concept of a macroscopic device can be extended to the molecular level by designing and synthesizing (supra)molecular species capable of performing specific functions. Molecular devices need energy to operate and signals to communicate with the operator. The energy needed to make a device work can be supplied as chemical energy, electrical energy, or light. Luminescence is one of the most useful techniques to monitor the operation of molecular-level devices. The extension of the concept of a device to the molecular level is of interest, not only for basic research, but also for the growth of nanoscience and the development of nanotechnology. In this article, some of the most recent experiments performed in our laboratory will be reviewed.
Pyridinium N-phenolate betaine dyes as empirical indicators of solvent polarity: Some new findings
Authors: Reichardt C.
Published: October 2007

Solutions of the zwitterionic betaine dye 4-(2,4,6-triphenylpyridinium-1-yl)-2,6-di- phenylphenolate are solvatochromic, thermochromic, piezochromic, and halochromic. That means the position of its longest-wavelength intramolecular charge-transfer absorption band depends on solvent polarity, solution temperature, external pressure, and the nature and concentration of added salts. The extraordinarily large negative solvatochromism of this standard betaine dye has been used to establish UV/vis spectroscopically an empirical scale of solvent polarity, called ET(30), respectively ET
N scale, meanwhile known for many organic solvents and solvent mixtures. In this review, the solvatochromic properties of some new hydrophilic and lipophilic betaine dyes with better solubility in water (respectively, nonpolar solvents), as well as some recent applications of these betaine dyes in various fields of interest [e.g., microheterogeneous (micellar) and polymer solutions, chemical sensors, as well as surface polarity of silicas, aluminas, and cellulose derivatives] are described.
Compilation of k0 and related data for NAA in the form of electronic database (IUPAC Technical Report)
Authors: Kolotov V. P. , De Corte F.
Published: October 2007

This report describes the principles underlying a comprehensive electronic database that contains data essential for calculation of analytical results from neutron-activation analysis (NAA) and that is available through IUPAC. The method used is a comparator method called the k
0 method, where k
0 is a dimensionless factor which is experimentally measured with high accuracy for more than 130 isotopes and which makes use of the gamma spectroscopic line for an analyte isotope relative to a gold comparator. The database contains recommended values for k
0 and other relevant nuclear data.
Workshop 1.6 QSAR and related procedures for prescreening and predicting potential endocrine-active compounds
Authors: Fujita T.
Published: October 2007

This workshop has been organized to cover various quantitative structure-activity relationship (QSAR) and computer aided procedures currently carried out for the prediction of the endocrine activity of unknown compounds. Each of the procedures has own scope as well as limitations. It seems inappropriate to consider that a single quantitative prediction model derived from each of these procedures could solve the entire issue. Because the model building is highly dependent on the data/knowledge about endocrine activity of a large number of existing compounds accumulated to date and the data/knowledge are growing constantly, the model has a destiny to be amended “forever ”as the structure-activity data of newly synthesized compounds are accumulated. The skepticism about in silico and QSAR procedures put forward in the past is likely to be cleared at least to some extent if not entirely by participating in this workshop.
Tandem methodology for heterocyclic synthesis
Authors: Padwa A.
Published: October 2007

Tandem methodology for heterocyclic synthesis represents a powerful approach for the rapid buildup of molecular complexity from potentially simple starting materials. Work from our laboratory has shown that the rhodium(II)-catalyzed cyclization cascade of alpha-diazo imides represents an effective method for the synthesis of a variety of heterocyclic systems. As an extension of these studies, we became interested in using a linked Pummerer/N-acyliminium ion cyclization sequence since we felt that this combination offers unique opportunities for the assemblage of complex target molecules. A synthetic method that combines transformations of different reaction types significantly broadens the scope of such procedures in synthetic chemistry. Alpha-thiocarbocations generated from the Pummerer reaction of beta-phenylsulfinylmethyl-alpha, beta-unsaturated amides can be intercepted by the adjacent amido group to produce transient amino-substituted furans which undergo subsequent Diels–Alder cycloadditions. Using this domino amido Pummerer/Diels–Alder cascade, we were able to assemble novel polycyclic systems in a single operation. The key step in the process involves the generation of a reactiveN-acyliminium ion by fragmentation of an amino-substituted [4+2]-cycloadduct. The successful synthesis of a number of alkaloids by this sequence of reactions reveals the usefulness and importance of this unique domino cascade. Application of the process for the preparation of the stenoma alkaloid stenine was recently carried out in our laboratory.
Pyridylketenes. Structure reactivity effects in nucleophilic and radical addition
Authors: Allen A. D. , Fedorov A. V. , Najafian K. , Tidwell T. T. , Vukovic S.
Published: October 2007

2-, 3-, and 4-Pyridylketenes have been generated in CH3CN by photochemical Wolff rearrangements and identified by their ketenyl absorption in the infrared at 2127, 2125, and 2128 cm–1, respectively. Reaction of these pyridylketenes with n-BuNH2 results in the formation of intermediate amide enols from the 3- and 4-pyridylketenes, which are then converted to the corresponding pyridylacetamides. However , 2-pyridylketene forms a long-lived 1,2-dihydropyridine intermediate stabilized by an intramolecular hydrogen bond, and this is converted to the 2-pyridylacetamide with a rate constant 107 less than those for the conversion of the amide enols from the 3- and 4-pyridylketenes to amides. Hydration of the pyridylketenes results in the formation of an acid enol intermediate in the case of the 3-isomer, while the 2- and 4-isomers form longer-lived dihydropyridines. The pyridylketenes react with the stable free radical tetramethylpiperidinyloxyl (TEMPO,TO) forming 1,2-diaddition products ArCH(OT)CO2T.
Domino reactions in the synthesis of heterocyclic natural products and analogs
Authors: Tietze L. F. , Rackelmann N.
Published: October 2007

Domino reactions are defined as processes of two or more bond-forming reactions under identical conditions, in which the subsequent transformation takes place at the functionalities obtained in the former transformation. They allow the efficient synthesis of complex molecules from simple substrates in an ecologically and economically favorable way. A very powerful domino process is the domino Knoevenagel–hetero-Diels–Alder reaction, in which an aldehyde or an beta-ketoester is condensed with a 1,3-dicarbonyl compound or a heteroanalog to give a 1-oxa-1,3-butadiene, which can undergo an inter- or intramolecular hetero-Diels–Alder reaction with dienophiles such as enol ethers or alkenes. The products are dihydropyrans, which can be transformed in a variety of ways. Thus, an extension of the process is the synthesis of highly substituted pyrrolidines, piperidines, and azepanes using aminoaldehydes. The process has also been employed for the enantioselective total synthesis of a variety of alkaloids, such as indol- and ipecacuanha alkaloids. In another domino process, erythrina and homoerythrina alkaloids have been prepared from simple phenylethylamines and ketoesters.
Definition of terms related to polymer blends, composites, and multiphase polymeric materials (IUPAC Recommendations 2004)
Authors: Work W. J. , Horie K. , Hess M. , Stepto R. F. T.
Published: October 2007

The document defines the terms most commonly encountered in the field of polymer blends and composites. The scope has been limited to mixtures in which the components differ in chemical composition or molar mass and in which the continuous phase is polymeric. Incidental thermodynamic descriptions are mainly limited to binary mixtures although, in principle, they could be generalized to multicomponent mixtures.

The document is organized into three sections. The first defines terms basic to the description of polymer mixtures. The second defines terms commonly encountered in descriptions of phase domain behavior of polymer mixtures. The third defines terms commonly encountered in the descriptions of the morphologies of phase-separated polymer mixtures.
Characterization of polyamides 6, 11, and 12. Determination of molecular weight by size exclusion chromatography (IUPAC Technical Report)
Authors: Robert E. C. , Bruessau Rudolf , Dubois J.-E. , Jacques Bernard , Meijerink Nico , Nguyen T. Q. , Niehaus D. E. , Tobisch W. A.
Published: October 2007

This report presents the results from IUPAC Working Party IV.2.2 of the global trial within the framework of IUPAC Commission IV.2, “Characterization of Commercial Polymers”. The results were compared on the basis of molecular weight obtained by size exclusion chromatography (SEC)using different techniques practiced in participating laboratories, the majority of which were materials suppliers. The practical methodologies used different solvents for the polymers, in particular, benzyl alcohol, 1,1,1,3,3,3 hexafluoropropan-2-ol and tetrahydrofuran; the latter solvent was used after chemical modification of the polyamides, in general with trifluoroacetic anhydride. Eight laboratories participated in the trial. The repeatability for molecular weight in each laboratory was good, whatever technique was used, the relative standard deviation averaged over all laboratories being around 3%. The deviations in distribution of molecular weights with different experimental methodologies were broader, but were reasonably good despite the diversity of methods. The differences in the distribution correspond to a confidence interval of about 30% in molecular weight.
Rheological properties and associated structural characteristics of some aromatic polycondensates including liquid-crystalline polyesters and cellulose derivatives (IUPAC Technical Report)
Authors: White J. L. , Dong L. , Han P. , Laun H. M.
Published: October 2007

A comparative experimental study of shear-flow rheological properties of thermotropic polymer liquid crystals by eight different laboratories is described. The materials involved four different liquid-crystalline polyesters (LCPs), a glass- fiber-filled liquid-crystalline polyester,hydroxypropyl cellulose (HPC), and two non-liquid-crystalline high-temperature polymers, a poly(etheretherketone) (PEEK), and a polyarylate (PAR). Studies were made in both steady shear-flow and dynamic oscillatory experiments. The data from the various laboratories involved were compared. The level of agreement in the data was much less for most liquid-crystalline polymers than for similar isotropic melts. The Cox –Merz rule is valid for PEEK and PAR, but not for the LCPs and HPC. The occurrence of low levels of extrudate swell and high levels of uniaxial orientation in extrudates of the LCPs and HPC is described.
Integrated nanoscale electronics and optoelectronics: Exploring nanoscale science and technology through semiconductor nanowires
Authors: Huang Yu , Lieber C. M.
Published: October 2007

Semiconductor nanowires (NWs)represent an ideal system for investigating low-dimensional physics and are expected to play an important role as both interconnects and functional device elements in nanoscale electronic and optoelectronic devices. Here we review a series of key advances defining a new paradigm of bottom-up assembling integrated nanosystems using semiconductor NW building blocks. We first introduce a general approach for the synthesis of a broad range of semiconductor NWs with precisely controlled chemical composition, physical dimension, and electronic, optical properties using a metal cluster-catalyzed vapor-liquid-solid growth mechanism. Subsequently, we describe rational strategies for the hierarchical assembly of NW building blocks into functional devices and complex architectures based on electric field or micro-fluidic flow. Next, we discuss a variety of new nanoscale electronic device concepts including crossed NW p-n diode and crossed NW field effect transistors (FETs). Reproducible assembly of these scalable crossed NW device elements enables a catalog of integrated structures, including logic gates and computational circuits. Lastly, we describe a wide range of photonic and optoelectronic devices, including nanoscale light-emitting diodes (nanoLEDs), multicolor LED arrays, integrated nanoLED-nanoFET arrays, single nanowire waveguide, and single nanowire nanolaser. The potential application of these nanoscale light sources for chemical and biological analyses is discussed.
Chemical reactions at surfaces and interfaces from first principles: Theory and application
Authors: Liu Z.-P.
Published: October 2007

The last decade has seen rapid expansion and development in the field of density functional theory (DFT) simulation on the complex chemical processes that occur at surfaces and interfaces. The understanding of the phenomena in surface science and heterogeneous catalysis has benefited tremendously from these quantum mechanic calculations. This article reviews current progress in the theory of reactions on surfaces, in particular, those relevant to the barrier and the active site of surface reactions. Two representative reactions, namely, NO dissociation and CO oxidation, are selected to illustrate how these theoretical concepts are applied to understand catalytic reactions. Here, the pathways and energetics of these reactions under various catalytic conditions are described in detail, and the understanding of the reactions is generalized. It is concluded that DFT-based methods can be well applied to catalysis to understand the electronic structure of chemical processes and to elucidate mechanisms of complex surface reactions.
Modeling prebiotic catalysis with nucleic acid-like polymers and its implications for the proposed RNA world
Authors: Srivatsan S. G.
Published: October 2007

The theory that RNA molecules played a pivotal role in the early evolution of life is now widely accepted. Studies related to this hypothetical “RNA world” include three major areas: the formation of precursors for the first RNA molecules, the polymerization process, and the potential of RNA to catalyze chemical and biochemical reactions. Several chemical and biochemical studies performed under simulated prebiotic conditions support the role of RNA as both genetic as well as catalytic material. However, owing to the lack of credible mechanism for de novo nucleic acid synthesis and the hydrolytic instability of RNA molecules, there has been some serious discussion of whether biopolymers that closely resembled nucleic acid preceded the “RNA world”. In this context, an overview of prebiotic chemistry, the role of mineral surface, and the significance of studies related to RNA-like polymers in the origin of life are presented here.
Name and symbol of the element with atomic number 111 (IUPAC Recommendations 2004)
Authors: Corish John , Rosenblatt G. M.
Published: October 2007

A joint IUPAC-IUPAP Working Party (JWP) confirmed the discovery of element number 111. In accord with IUPAC procedures, the discoverers proposed a name and symbol for the element. The Inorganic Chemistry Division recommended this proposal for acceptance, and it was adopted by IUPAC on 1 November 2004. The recommended name is roentgenium with symbol Rg.
Chemical actinometry (IUPAC Technical Report)
Authors: Kuhn H. J. , Braslavsky S. E. , Schmidt R.
Published: October 2007

This document updates the first version of the IUPAC technical report on “Chemical actinometers” published in Pure Appl. Chem. 61 ,187-210 (1989). Since then, some methods have been improved, procedures have been modified, and new substances have been proposed as chemical actinometers. An actinometer is a chemical system or a physical device by which the number of photons in a beam absorbed into the defined space of a chemical reactor can be determined integrally or per time. This compilation includes chemical actinometers for the gas, solid, microheterogeneous, and liquid phases, as well as for the use with pulsed lasers for the measurement of transient absorbances, including the quantum yield of phototransformation, as well as the literature for each of the actinometers. The actinometers listed are for the use in the wavelength range from the UV to the red region of the spectrum. A set of recommended standard procedures is also given. Advantages and disadvantages are discussed regarding the use of chemical actinometers vs. electronic devices for the measurement of the number of photons absorbed. Procedures for the absolute measurement of incident photon flux by means of photodiodes are also discussed.
Electrochemistry at the interface between two immiscible electrolyte solutions (IUPAC Technical Report)
Authors: Samec Z.
Published: October 2007

This document provides an inventory of theoretical and methodological concepts in electrochemistry at the interface between two immiscible electrolyte solutions (ITIES). Definitions of basic relationships are given, together with recommendations for the preferred symbols, terminology, and nomenclature. Methods of study of ITIES are briefly described, current experimental problems are indicated, and representative experimental data are shown. The practical applications of electrochemistry at ITIES are summarized.
Admixture Estimates for Caracas, Venezuela, Based on Autosomal, Y-Chromosome, and mtDNA Markers
Authors: Martínez Helios , Rodriguez-Larralde Alvaro , Izaguirre Mary Helen , De Guerra Dinorah Castro
Published: October 2007

The present Venezuelan population is the product of admixture of Amerindians, Europeans, and Africans, a process that was not homogeneous throughout the country. Blood groups, short tandem repeats (STRs), mtDNA, and Y-chromosome markers have been used successfully in admixture studies, but few such studies have been conducted in Venezuela. In this study we aim to estimate the admixture components of samples from two different socioeconomic levels from Caracas, Venezuela's capital city, compare their differences, and infer sexual asymmetry in the European Amerindian union patterns. Gene frequencies for blood groups ABO and Rh (CDE) and for the STRs VWA, F13A01, and FES/FPS and mtDNA and Y-chromosome haplogroups were studied in a sample of 60 individuals living in Caracas, taken from a private clinic (high socioeconomic level), and 50 individuals, also living in Caracas, drawn from a public maternity clinic (low socioeconomic level). The admixture analysis for the five autosomal markers gives a high European component (0.78) and an almost negligible African sub-Saharan component (0.06) for the high socioeconomic level, whereas for the low socioeconomic level the sub-Saharan, European, and Amerindian components were 0.21, 0.42, and 0.36, respectively. Estimates of admixture based on mtDNA and Y-chromosome markers reveal that the Amerindian contribution to these Caracas samples is almost entirely through females, because the Y-chromosome Amerindian and African sub-Saharan chromosomes found in this study were scarce. Our study reveals that the identification of the grandparents' geographic origin is an important methodological aspect to take into account in genetic studies related to the reconstruction of historical events.
Genetic Determinants of Risk Factors for Cardiovascular Disease in a Population from Rural Brazil
Authors: Velásquez-Meléndez Gustavo , Parra Flavia C , Gazzinelli Andrea , Williams-Blangero Sarah , Correa-Oliveira Rodrigo
Published: October 2007

We investigate the heritability of and pleiotropic relationships among triglycerides and cholesterol lipoproteins that have long been considered traditional risk factors for cardiovascular disease. Quantitative lipid and lipoprotein phenotypes were determined for a cross-sectional sample of a community in Jequitinhonha valley in northern Minas Gerais state, Brazil. The sample consisted primarily of subsistence farmers. Two hundred sixty-nine individuals (128 males and 141 females), ages 18–88 years, were sampled. Eighty-eight percent (n = 252) of the individuals belonged to a single pedigree, which was highly informative for genetic analysis. Data on anthropometrics, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), total cholesterol, and triglycerides were available for each study participant. Extended pedigrees were constructed using the pedigree-based data management software PedSys. Univariate and bivariate variance-components analyses, adjusted by sex and age, were performed using the SOLAR software package. Heritability estimates of lipids and lipoproteins ranged from 29% to 45% (p < 0.008). The highest heritability estimated was for HDL-C (h2 = 44.8%, p < 0.0001), and this was the only trait that exhibited a significant household effect (c2 = 25%). Strong positive genetic correlations were found between triglycerides and very low density lipoprotein (VLDL) (ρg = 0.998) and between total cholesterol and LDL-C (ρg = 0.948). Significant genetic correlations were also found between triglycerides and LDL-C, between total cholesterol and VLDL, and between total cholesterol and LDL-C and VLDL, and finally between LDL and VLDL. There was a significant negative environmental correlation between triglycerides and HDL-C (ρe = –0.406).
Sex-Specific Association of the Glucocorticoid Receptor Gene With Extreme BMD
Authors: Peng Yu-Mei , Lei Shu-Feng , Guo Yan , Xiong Dong-Hai , Yan Han , Wang Liang , Guo Yan-Fang , Deng Hong-Wen
Published: October 2007

To study the role of the GR gene on BMD regulation in the Chinese, a sex-specific association study was performed. The results indicated that GR variation contributed to the extreme BMD variation in the Chinese.

Introduction: The glucocorticoid (GC) receptor (GR) gene is an important candidate gene for BMD regulation in GC-induced osteoporosis (GIO). However, no study has explored the genetic effects of the GR gene on BMD variation in the Chinese population.

Materials and Methods: Our sample consisted of 800 unrelated subjects (400 women and 400 men) with extreme age-adjusted hip BMD Z-scores selected from a population composed of 1988 normal adult Chinese Han. Four single nucleotide polymorphisms (SNPs) in the GR gene were genotyped. Both single SNP and haplotype association analyses were conducted.

Results: SNP rs1866388 (pc = 0.028) was found to be significantly associated with extreme BMD only in men. In both sexes, haplotypes involving rs1866388 and rs2918419 were found to have different frequency distributions in extremely low and high BMD groups (pp = 0.024, 0.001, and 0.002 in women and 0.002, 0.003, and 0.003 in men for window sizes of two, three, and four SNPs, respectively). Most shared haplotypes showed opposite effects between women and men.

Conclusions: For the first time, our study suggested the possible role of the GR gene on BMD regulation and sex specificity in the association of GR with extreme BMD in the Chinese.
Proximal Femur Mechanical Adaptation to Weight Gain in Late Adolescence: A Six-Year Longitudinal Study
Authors: Petit Moira A , Beck Thomas J , Hughes Julie M , Lin Hung-Mo , Bentley Christy , Lloyd Tom
Published: October 2007

The effect of weight gain in late adolescence on bone is not clear. Young women who consistently gained weight (n = 23) from 17 to 22 yr of age had increased BMD but a lack of subperiosteal expansion compared with stable weight peers (n = 48). Bone strength increased appropriately for lean mass in both groups but decreased relative to body weight in weight gainers, suggesting increased bone fragility in weight gainers.

Introduction: Weight gain leading to obesity often starts in adolescence, yet little is known about its effects on bone. We used longitudinal data to examine the effects of weight gain in late adolescence (from 17 to 22 yr of age) on proximal femur BMD, geometry, and estimates of bending strength.

Materials and Methods: Participants were classified as either weight gainers (WG, n = 23) or stable weight (SW, n = 48) using a random coefficients model. Weight gainers had positive increases in weight (p < 0.05) at each clinic visit from age 17 onward. Proximal femur DXA scans (Hologic QDR 2000) taken annually from 17 to 22 yr of age were analyzed for areal BMD (g/cm2), subperiosteal width (cm), and bone cross-sectional area (CSA) at the proximal femoral shaft. Cortical thickness was measured, and section modulus (Z, cm3) was calculated as a measure of bone bending strength. Total body lean (g) and fat (g) mass were measured from DXA total body scans.

Results: Over ages 17–22, height remained stable in both groups. Weight remained static in the SW group but increased 14% on average in the WG group (p < 0.05). After controlling for age 17 baseline values, WG had higher BMD (+2.6%), thicker cortices (+3.6%), and greater bone CSA (+2.3%). Increased BMD did not translate to greater increases in bone bending strength (Z). The SW group achieved similar gains in Z by greater subperiosteal expansion. Bone strength index (SI = Z/height) normalized for body weight remained constant in the SW group but decreased significantly in the WG group. In contrast, SI normalized to lean mass did not change over time in either group. Other variables including physical activity, nutrition, and hormone levels (estradiol, testosterone, cortisol) did not differ significantly between groups.

Conclusions: These data suggest that weight gain in late adolescence may inhibit the periosteal expansion known to normally occur throughout life in long bones, resulting in decreased bone strength relative to body weight.
Factors Affecting Short-Term Bone Density Precision Assessment and the Effect on Patient Monitoring
Authors: Leslie William D
Published: October 2007

The most widely used procedure for performing a BMD reproducibility assessment (same-technologist with simple repositioning on the same day) systematically underestimates precision error and will lead to over categorization of change in a large fraction of monitored patients.

Introduction: The most common procedure for establishing the least significant change (LSC) to monitor bone mineral density (BMD) with DXA is for the same technologist to perform repeat subject scans on the same day with simple repositioning. The objective of the current report is to determine how the reproducibility scanning procedure impacts on the precision assessment and categorization of change in routine clinical practice.

Materials and Methods: The study population was drawn from the database of the Manitoba Bone Density Program which includes all clinical DXA test results for the Province of Manitoba, Canada. All patients who had baseline and follow up total spine (L1–4) and the total hip BMD measurements on the same instrument up to March 31, 2007 were included as the ‘clinical monitoring population’ (N = 5048 scan-pairs). BMD precision was assessed in a convenience sample of patients who were agreeable to undergoing a repeat assessment (50% performed on the same day with repositioning, 68% by different technologists) (N = 331 spine and 328 hip scan-pairs).

Results: Precision error was greater when the scan-pairs were acquired on different days than on the same day for both the total spine (p < .001) and total hip (p < .01). No other factor was consistently associated with precision error. The reference LSC (different days and different technologists) categorized the smallest fraction of the monitored population with change, whereas other combinations gave a significant rate of over categorization (up to 19.3% for the lumbar spine and up to 18.3% for the total hip).

Conclusions: The most widely procedure for performing a BMD reproducibility assessment (same-technologist with simple repositioning on the same day) systematically underestimates precision error and will lead to over categorization of change in a large fraction of monitored patients.
A Population-Based Assessment of Rates of Bone Loss at Multiple Skeletal Sites: Evidence for Substantial Trabecular Bone Loss in Young Adult Women and Men
Authors: Riggs B Lawrence , Melton L Joseph , Robb Richard A , Camp Jon J , Atkinson Elizabeth J , McDaniel Lisa , Amin Shreyasee , Rouleau Peggy A , Khosla Sundeep
Published: October 2007

Using QCT, we made a longitudinal, population-based assessment of rates of bone loss over life at the distal radius, distal tibia, and lumbar spine. Cortical bone loss began in perimenopause in women and later in life in men. In contrast, trabecular bone loss began in young adulthood in both sexes.

Introduction: Although conventional wisdom holds that bone loss begins at menopause in women and later in life in men, this has not been examined longitudinally in population-based studies using precise technology capable of distinguishing cortical and trabecular bone.

Materials and Methods: In an age- and sex-stratified population sample (n = 553), we measured volumetric BMD (vBMD) of trabecular and cortical bone by QCT annually for up to 3 yr at the distal radius (DR) and distal tibia (DT) (n = 552) and trabecular vBMD at baseline and 3 yr at the lumbar spine (LS) (n = 474).

Results: Substantial cortical bone loss began in middle life in women but began mainly after age 75 in men. In contrast, substantial trabecular bone loss began in young adult women and men at all three skeletal sites and continued throughout life with acceleration during perimenopause in women. Women experienced 37% and men experienced 42% of their total lifetime trabecular bone loss before age 50 compared with 6% and 15%, respectively, for cortical bone. Median rates of change in trabecular bone (%/yr) were −0.40, −0.24, and −1.61 in young adult women and −0.38, −0.40, and −0.84 in young adult men at the DR, DT, and LS, respectively (all p < 0.001). The early trabecular bone loss did not consistently correlate with putative causal factors, except for a trend with IGF-related variables at DT in women. However, in postmenopausal women and, to a lesser extent, in older men, higher rates of cortical and trabecular bone loss were associated with lower levels of biologically-active sex steroids and with higher levels of follicle-stimulating hormone and bone turnover markers.

Conclusions: The late onset of cortical bone loss is temporally associated with sex steroid deficiency. However, the early-onset, substantial trabecular bone loss in both sexes during sex steroid sufficiency is unexplained and indicates that current paradigms on the pathogenesis of osteoporosis are incomplete.
Intensity Ratios of H Lines: Departures from the Ideal Conditions in the Range of Laser-Induced Breakdown Spectroscopy Experiments
Authors: Cruzado A. , Rocco H. O. DI
Published: October 2007

In the present paper we analyze the behavior of H line intensity ratios with electron density and electron temperature in intermediate-density plasmas. We analyze the influence on the line intensity ratios of (1) the departures from local thermodynamic equilibrium (LTE) of the level population ratios, (2) the plasma opacity, and (3) the lowering of the ionization potential. We look, particularly, at the lines Hα, Hβ, Hγ, and Hδ and the energy levels involved in the corresponding atomic transitions for their use as diagnostics in laser-induced breakdown spectroscopy (LIBS) experiments. One important conclusion is that, for typical values of the plasma dimension and the electron temperature taking place in LIBS, i.e., L = 1 mm and Te = 10 000 K, respectively, the intensity ratios Hβ /Hα, Hγ/ Hα, and Hδ/ Hα depart from the ideal values by less than 10% in the interval 0.65 × 1014 part/cm3 ≤ NHI ≤ 3.6 × 1017 part/cm3, which means 1 × 1014 part/cm3 ≤ Ne ≤ 1 × 1016 part/cm3 for a gas of pure hydrogen. For higher densities, the departures from ideal conditions increase very quickly due to opacity effects.