bluuebunny/crossref_metadata_2025 huggingface dataset:
Wires, switches, and wiring. A route toward a chemically assembled electronic nanocomputer
Authors: Heath James R.
Published: October 2007

A Boolean logic, nonreversible computing machine should, in principle, be capable of 10 18 bit operations per second at a power consumption of 1 W. In order to build such a machine that can even approach this benchmark for efficiency, the development of a robust quantum-state switch capable of ambient operation, as well as a bottom–up manufacturing technology, will be necessary. My group, in collaboration with Hewlett Packard, has developed much of the architecture for such a machine, which we call a chemically assembled electronic nanocomputer (CAEN). More recently, in a collaborative effort with Fraser Stoddart's group at UCLA, we have begun to build it. The fundamental unit of the machine is a field-programmable molecular switch, and the fundamental architecture is a hierarchical organization of wire/switch lattices called crossbars. Electronically, singly configurable molecular-based switch devices based on rotaxane molecular compounds have been fabricated in high yield. These switches were used to construct simple molecular-based logic structures and read-only memory elements.
Purpose-built metal oxide nanomaterials. The emergence of a new generation of smart materials
Authors: Vayssieres Lionel , Hagfeldt Anders , Lindquist Sten Eric
Published: October 2007

A new concept has been developed in order to achieve a new generation of smart materials, namely purpose-built materials, modeled and designed to match the physical and structural requirements of their applications. A model based on the thermodynamic monitoring of the nucleation, growth, and aging process of metal oxide by minimization of the interfacial tension, yielding to the thermodynamic stabilization of the system, results in well-designed and well-ordered nanostructured materials with the required porosity, morphology, size, and orientation on various substrates.
Binary cooperative complementary nanoscale interfacial materials. Reduction of silver nanoparticles in DMF. Formation of monolayers and stable colloids
Authors: Pastoriza-Santos Isabel , Liz-Marzán Luis M.
Published: October 2007

We explore in this article the reduction of Ag + ions by N,N-dimethylformamide (DMF), both in the presence and in the absence of a stabilizing agent. The reduction can lead to the formation of either thin films of silver nanoparticles electrostatically attached onto glass surfaces, or stable dispersions of silver nanoparticles if the silane coupling agent 3-aminopropyltrimethoxysilane (APS) is present. The different parameters affecting the reduction process are discussed, and the reducing ability of DMF is compared with that of ethanol, which is often used for the production of catalytically active metal colloids.
Photophysics and spectroscopy of metal particles
Authors: Hodak José H. , Henglein Arnim , Hartland Gregory V.
Published: October 2007

This paper describes our recent work using ultrafast laser spectroscopy to examine the fundamental properties of metal particles. Two studies are presented. First, the characteristic time scale for electron-phonon coupling in Au particles with sizes between 2 and 120 nm has been examined by bleach recovery measurements. These experiments show that the coupling between the electrons and phonons is independent of particle size, to within the signal-to-noise of our experiments. We have also used transient absorption spectroscopy to examine the low-frequency "breathing" modes of the Au particles. These modes are impulsively excited by the rapid lattice heating that accompanies electron-phonon coupling. The breathing motion contributes to the transient absorption signal because the position of the plasmon band depends on the free electron density and, thus, the particle volume. The measured frequencies are inversely proportional to the radius, and almost exactly match the predictions of classical mechanics calculations for Au.
Nanomeasurements of individual carbon nanotubes by in situ TEM
Authors: Wang Z. L. , Poncharal P. , de Heer W. A.
Published: October 2007

Property characterization of nanomaterials is challenged by the small size of the structure because of the difficulties in manipulation. Here we demonstrate a novel approach that allows a direct measurement of the mechanical and electrical properties of individual nanotube-like structures by in situ transmission electron microscopy (TEM). The technique is powerful in a way that it can be directly correlated to the atomic-scale microstructure of the carbon nanotube with its physical properties, thus providing a complete characterization of the nanotube. Applications of the technique will be demonstrated in measurements of the mechanical properties, the electron field emission, and the ballistic quantum conductance of individual carbon nanotubes. A nanobalance technique is demonstrated that can be applied to measure the mass of a single tiny particle as light as 22 fg (1 f = 10-15 ).
Optical absorption property of oxidized free-standing porous silicon films
Authors: Xu Dongsheng , Guo Guolin , Gui Linlin , Tang Youqi , Qin G. G.
Published: October 2007

We have systematically studied the evolution of the optical absorption of free-standing PS films during thermal oxidation at 200°C in air. Our experiment results show the evolution of transmission curve is quite complicated, which red-shifts first and then blue-shifts during thermal oxidation. At the same time, the transmission at the low energy decreases first and then increases. We propose an explanation as follows: (1) the energy gap associated with each crystallite should increase during thermal oxidation process, due to the quantum confinement effect; (2) the energy gap should decrease with an increase in oxygen termination atoms. Both the increasing of the gap due to the quantum confinement effect and the decreasing of the gap due to the Si-O bond formation cause a complicated evolution of optical absorption.
Effect of atmospheric oxidation on the electronic and photoluminescence properties of silicon nanocrystal
Authors: Germanenko I. N. , Dongol M. , Pithawalla Y. B. , El-Shall M. Samy , Carlisle J. A.
Published: October 2007

Web-like aggregates of coalesced Si nanocrystals produced by a laser vaporization-controlled condensation technique show luminescence properties that are similar to those of porous Si. The results are consistent with a quantum confinement mechanism as the source of the red photoluminescence (PL) in this system. The oxidized Si nanoparticles do not exhibit the red PL that is characteristic of the surface-oxidized Si nanocrystals. The nanoparticles are allowed to oxidize slowly, and the PL is measured as a function of the exposure time in air. A significant blue shift in the red PL peak is observed as a result of the slow oxidation process. The dependence of quantum size effects on the bonding structure is established by correlating the PL data with the photon-yield electronic structure measurements made at the Advanced Light Source. The results indicate that as the nanoparticles oxidize, the radius of the crystalline core decreases in size, which gives rise to a larger bandgap and consequently to the observed blue-shift in the PL band. The correlation between the PL, SXF, and NEXAFS results provides further support for the quantum confinement mechanism as the origin of the visible PL in Si nanocrystals.
Silica-coated metals and semiconductors. Stabilization and nanostructuring
Authors: Alejandro-Arellano Marta , Ung Thearith , Blanco Álvaro , Mulvaney Paul , Liz-Marzán Luis M.
Published: October 2007

We present in this paper the use of silica-coating for nanostructuring metal and semiconductor nanoparticles. The basic concept is the strict tailoring of the interparticle spacing through the thickness of the silica shell. Three different experiments are presented that exemplify this concept. The first example consists of the preparation of thin films using the layer-by-layer self-assembly of gold nanoparticles, either uncoated or coated with thin silica shells. The observed optical effects are interpreted using effective medium theory. The second and third experiments are related to the preparation of three-dimensional nanostructures, either as concentrated dispersions of thickly coated Au or CdS nanoparticles, or as opals prepared from such core-shell nanoparticles. Within these crystalline solids, intercore distance is again dictated by the thickness of the silica shells.
Interfacial chemistry in self-assembled nanoscale materials with structural orderin
Authors: Liu Jun , Fryxell Glen E. , Qian Maoxu , Wang Li-Qiong , Wang Yong
Published: October 2007

This paper discusses the interfacial chemistry encountered in the self-assembly of ordered nanoscale materials based on surfactant liquid crystalline structures. The paper contains three sections. The first section gives a brief introduction to the interfacial chemistry in the co-assembly of surfactants and inorganic materials. The second section discusses the formation of inorganic–inorganic nanocomposites, the properties of such materials, and the interfacial atomic structures. The last section discusses hybrid nanoscale materials with functional monolayers, their interfacial chemistry, and their potential applications.
Localized-density-matrix method and its application to nanomaterials
Authors: Chen GuanHua , Yokojima Satoshi , Liang WanZhen , Wang XiuJun
Published: October 2007

The localized-density-matrix (LDM) method has been developed to calculate the excited state properties of very large systems containing thousands of atoms. It is particularly suitable for simulating the dynamic electronic processes in nanoscale materials, and has been applied to poly(p-phenylenevynelene) (PPV) aggregates and carbon nanotubes. Absorption spectra of PPVs and carbon nanotubes have been calculated and compared to the experiments.
Core/shell-structured bimetallic nanocluster catalysts for visible-light-induced electron transfer
Authors: Toshima Naoki
Published: October 2007

It has been found that the bimetallic nanoclusters often have so-called core/shell structure if they are prepared by alcohol-reduction of two kinds of noble metal ions in the presence of a water-soluble polymer like poly(N-vinyl-2-pyrolidone)(PVP), and that the core/ shell structured bimetallic nanoclusters have much higher catalytic activity than the corresponding monometallic nanoclusters. Here, several kinds of monometallic and bimetallic nanoclusters are synthesized by the similar method, and the catalyses are measured. Thus, the colloidal dispersions of Au, Pt, Pd, Rh, and Ru monometallic, and Au/Pt, Au/Pd, Au/Rh, and Pt/Ru bimetallic nanoclusters were synthesized and applied as the catalysts for visible-light- induced hydrogen generation. The core/shell structures are analyzed mainly by UV–vis spectra. The rate of electron transfer from the methyl viologen cation radical to the metal nanoclusters is proportional to the hydrogen generation rate at the steady state. All the electrons accepted by the metal nanoclusters are used for the hydrogen generation. Both electron transfer and hydrogen generation rates increase when the bimetallic nanoclusters are used in place of the corresponding monometallic nanoclusters. The most active catalysts were Au/Rh and Pt/Ru bimetallic nanoclusters.
Names for inorganic radicals (IUPAC Recommendations 2000)
Authors: Koppenol W. H.
Published: October 2007

Introduction: Knowledge of the properties and reactivities of stable inorganic radicals was obtained decades ago through gas-phase studies of various oxides of halogens, sulfur, and nitrogen. More recently, pulse radiolysis and flash photolysis techniques developed in the 1960s made it possible to study short-lived radicals, such as hydrated electrons, hydrogen atoms, and hydroxyl radicals. Because of the high time-resolution of these techniques, absorption spectra and redox properties of these inorganic radicals could be determined. The interest in radicals increased when it was shown that superoxide, or dioxide(1-), is formed in vivo. The discovery that in aerobic organisms enzymes catalyze the disproportionation of this radical resulted in new areas of research, such as radical biology and radicals in medicine. Interest in simple radicals was further boosted most recently by the remarkable observation that the radical nitrogen monoxide is formed enzymatically from the amino acid arginine. Radicals are important in a variety of catalytic processes and in the atmospheric gas and liquid phases; furthermore, a substantial number of inorganic radicals have been observed in interstellar gas clouds.

Contents:

1. Introduction

2. Definitions

3. Nomenclature

3.1. Introduction

3.2. Coordination nomenclature

3.2.1. Selection of the central atom

3.2.2. Radicals with net charges

3.2.3. Attached atoms or groups of atoms

3.2.4. The radical dot

3.2.5. Examples

3.3. Substitutive nomenclature
Species-selective determination of selenium compounds in biological materials (Technical Report)
Authors: Lobinski R. , Edmonds J. S. , Suzuki K. T. , Uden P. C.
Published: October 2007

There is substantial evidence of the complexity of selenium speciation in living organisms and of the importance of the selective determination of the particular species of this element in order to understand its metabolism and biological significance in clinical chemistry, biology, toxicology, and nutrition. The state-of-the-art of analytical techniques available for this purpose is critically evaluated with particular emphasis on the element-selective detection and identification of the detected selenium compounds. Whereas there are a number of techniques available that are able to detect various selenium species in living organisms selectively, few techniques exist that are able to identify and to characterize the species detected.
Thermodynamic characterization of high-temperature superconductors in the yttrium-barium-copper-oxygen system. The Y123 solid solution (Technical Report)
Authors: Voronin G. F.
Published: October 2007

The aim of this report is to inform the chemical community about a self-consistent thermodynamic data set for the YBa2 Cu3 O6+z (1 ≥ z ≥ 0) solid solution, that is well known as the Y123 phase and possesses superconducting properties at z~1 and low temperatures. About 3300 experimental points obtained in 240 miscellaneous experiments published in 78 papers have been processed simultaneously in order to obtain the most reliable Gibbs energy function of the Y123 phase in the temperature range from 250 to 1300 K and pressures up to 100 kbar. A function is recommended for approximation of the Gibbs energy, which has 16 adjustable parameters. All other thermodynamic properties of the Y123 solution, including the conditions for its internal stability, can be derived from the assessed Gibbs energy. Brief descriptions of the thermodynamic model, experimental and data assessment methods as well as examples of self-consistent thermodynamic data applications are given.
Properties and units in the clinical laboratory sciences. Part XII. Properties and units in clinical pharmacology and toxicology (Technical Report) (IFCC-IUPAC 1999)
Authors: Olesen Henrik , Cowan David , De La Torre Rafael , Bruunshuus Ivan , Rohde Morten , Kenny Desmond
Published: October 2007

The term designating a substance being an active ingredient of a drug may be a generic name, a nonproprietary name, a registered trade name, a fantasy name, or other. This causes difficulties in the transmission of requests and reports on properties for such substances in biological fluids to and from the clinical laboratories, and in the collating of this information from different sources.

The document comprises a list of properties of drugs in biological fluids for use in electronic transmission systems. Systematic names are presented together with a code value for each.
Effects of vitamin C supplementation in human volunteers with a range of cholesterol levels on biomarkers of oxygen radical-generated damage
Authors: Anderson D. , Phillips B. J. , Yu Tian-Wei , Edwards A. J. , Ayesh R. , Butterworth K. R.
Published: October 2007

Twenty-four men and 24 women, all nonsmoking, and maintaining normal dietary habits were assigned to 3 groups of 16. Each group comprising 4 males with "low" cholesterol levels (<6 mmol/L) matched for age and build with 4 males with "high" cholesterol levels (>6 mmol/L) and 8 similarly matched females. A three-treatment, three-treatment period, cross-over design was adopted. The three treatments were placebo, 60 mg vitamin C/day (the recommended daily allowance) and 6 g vitamin C/day for 14 days with 6 weeks between treatments. Blood samples were taken at the end of each treatment period. Vitamin C supplementation significantly increased plasma vitamin C concentrations and total antioxidant capacity, but did not affect cholesterol status or plasma ras p21 protein levels. There was a nonsignificant dose-related decrease in plasma lipid peroxidation breakdown products. DNA damage, measured in lymphocytes by the Comet assay and chromosome aberration test, was not increased after vitamin C supplementation. Sensitivity to hydrogen peroxide (in the Comet assay) was also unaffected, but sensitivity to chromosome aberration induced by bleomycin was increased by supplementation. A significant gender difference was found in plasma vitamin C levels, antioxidant capacity, and number of chromosome aberrations. Results were independent of low and high cholesterol status.
Cytochrome P4501A and associated mixed-function oxidase induction in fish as a biomarker for toxic carcinogenic pollutants in the aquatic environment
Authors: Arinç Emel , Sen Alaattin , Bozcaarmutlu Azra
Published: October 2007

Polycyclic aromatic hydrocarbons (PAHs), dioxins, dibenzofurans, and polychlorinated biphenyls (PCBs) present in polluted environment induce cytochrome P4501A (CYP1A) isozyme in fish, which in turn results in a marked increased production of carcinogenic metabolites from PAHs. The induction of hepatic CYP1A in fish by certain classes of chemicals has been suggested as an early warning system, a "most sensitive biological response" for assessing environmental contamination conditions. This has implications for human fish consumption, as well as for the health status of aquatic organisms. Correlation between elevated CYP1A and altered steroid metabolism and decreased reproductive success has been pointed out. The induction of CYP1A and associated enzyme activities has now been confirmed in a number of field studies. Cases where these biomarkers have been studied in field conditions will be presented. Special emphasis will be given to field studies in which the induction of CYP1A activity, 7-ethoxyresorufin O-deethylase (EROD) activities and immunochemical detection of CYP1A in leaping mullet and common sole are used as a biomarker for PAH- and/or PCB-type pollutants along the Izmir Bay on the Aegean Sea.
Role of neuronal nitric oxide in methamphetamine neurotoxicity and protection by nNOS inhibitor
Authors: Desaiah D. , Reddy S. L. N. , Imam S. Z. , Ali S. F.
Published: October 2007

Methamphetamine (METH) is a potent psychostimulant known to produce neurotoxicity. The dopaminergic pathway is particularly sensitive to METH. Recent studies showed that 7-nitroindazole (7-NI), a selective inhibitor of neuronal nitric oxide synthase (nNOS), provided protection against METH neurotoxicity both in vitro and in vivo. The present studies were conducted to determine the nNOS activity in various regions of the brain of young adult male Sprague-Dawley rats treated with different doses of METH. Rats were injected ip with 5, 10, 20, and 40 mg/kg and 24 h after the rats were sacrificed and the brain regions (hippocampus, frontal cortex, and cerebellum) were quickly dissected. The cytosolic fractions were prepared, and the nNOS activity was determined using the 3H-citrulline assay. The results showed that nNOS activity was significantly increased in all three brain regions of rats treated with METH. The increase was dose dependent reaching a maximum of 40-100% over the control values. Rats treated with 7NI 30 min prior to METH injection provided protection against the toxicity and also showed a reduction of nNOS activity. The activation of nNOS is known to increase the synthesis of NO which is involved in the regulation of several neurotransmitter pathways including catecholaminergic system. Reducing the METH-induced production of NO by pretreatment with selective inhibitor of nNOS, 7-NI, provided protection against METH neurotoxicity.
Risk assessment. Principles and consequences
Authors: Purchase I. F. H.
Published: October 2007

Risk assessment is an important tool in deciding how to allocate resources to controlling risks. In most cases it is based on hazard data derived from animal experiments and on exposure data from an assessment of the likely or actual exposure of the population of interest. Recent advances have improved the understanding of the use of the no adverse effect level (NOAEL) and safety factor for risk assessment by providing a scientific justification of the 100-fold safety factor. Concern about the risks of exposure by various routes simultaneously (aggregate exposure) and the risks of exposure to mixtures (cumulative risk assessment) have lead to new approaches to these issues. For many years, risk assessment of genotoxic carcinogens has relied on low-dose extrapolation using mathematical models. Recently, these methods are being reconsidered and, in some cases, replaced with the NOAEL/safety factor approach combined with all information on the mechanism of action and the magnitude of the response. It is vitally important to ensure that risk assessment provides accurate and unbiased estimates of risk of exposure so that appropriate measures can be taken to control the risks.
Sectional hair testing. Judicial and clinical applications
Authors: Tsatsakis Aristidis M. , Tzatzarakis Manolis
Published: October 2007

Modern sophisticated analytical tools have enabled toxicologists to investigate hair specimens for the presence of drugs. Although great sensitivity and specificity in hair analysis have been already achieved, some concerns about bias due to hair color, lack of reference materials, and dose versus concentration relationship make the quantitative data sometimes debatable. The most commonly held opinion in this field nowadays indicates that hair analysis has sufficient scientific validity. Experts should always be aware and take into account limitations of hair analysis results and its evaluation. Unresolved scientific issues, however, should not obstruct the admissibility of strongly positive test results. Recent applications of hair testing include forensic investigations, epidemiological studies, gestational drug exposure, legal issues, clinical drug monitoring, and historical research. In this paper, the use of sectional hair tests to assess exposure to drugs of abuse (evaluation of toxicomania) and to assess compliance with carbamazepine, phenytoin and valproic acid therapy regime is presented. We conclude that hair drug versus time profiles give strong evidence that confirm chronic abuse, the diagnosis of drugs of abuse poisoning, and the state of addiction (toxicomania). Additionally, they may be used as a marker of the dosage history and the compliance of patients under long-term treatment with carbamazepine and phenytoin.
Cleaner industrial processes using hydrogen peroxide
Authors: Sanderson William R.
Published: October 2007

Recent research progress in catalytic systems for potential use with hydrogen peroxide in industrial chemical synthesis is reviewed, with special focus on work published in the last five years. The main types of chemistry employed are critically appraised regarding their suitability for industrial exploitation. The most significant catalyst types are discussed in terms of the positive features identified to date, and the obstacles yet to be surmounted in order to become more widely adopted. It is believed that fully inorganic systems have more scope for commercialization than those containing organic ligands or supports, however robust. Critical targets are larger-pore analogs of titanium silicalite TS-1, more exploration of smectite-based materials, effective immobilization of activated metal peroxo systems, and improvements in design and manipulation of polyoxometallate compounds. Cooperation between branches of chemistry that have not traditionally worked closely together is advocated.
Heteropolyacids. Versatile green catalysts usable in a variety of reaction media
Authors: Misono Makoto , Ono Izumi , Koyano Gaku , Aoshima Atsushi
Published: October 2007

Basic characteristics of heteropolyacids as green catalysts are overviewed, focusing on the various reaction fields in which the heteropolyacid catalysts function as acid and oxidation catalysts, and then two industrial processes which were made very green by the use of heteropolyacid catalysts in liquid biphase systems are described. In this context an interesting new reaction field formed at the interfacial layer of a solid heteropolyacid and liquid has also been reported.
Free radicals in synthesis. Clean reagents affording oxidative or reductive termination
Authors: Murphy John A.
Published: October 2007

Neurotoxic organotin reagents currently play a key role in radical chemistry. As a result, this is an important area for development of new clean replacement reactions. The pharmaceutical industry in particular has had to avoid use of radical methodology for the formation of carbon_carbon bonds for this reason. With the current dawn in green chemistry, a host of new clean radical methods is beginning to flourish. Our aim has been to develop new nontoxic methodology for carbon_carbon bond formation by radical chemistry, which would provide either reductive termination (giving a hydrogen atom to the ultimate radical, as happens with tributyltin hydride), or oxidative functionalization, installing a useful polar group at the site of the ultimate radical. Two methods for effecting radical reactions in an environmentally friendly way are presented: (i) The tetrathiafulvalene (TTF)-mediated radical-polar crossover reaction converts arenediazonium salts to aryl radicals, which have sufficient lifetime to cyclize onto alkenes—the resulting alkyl radicals couple with TTF+• to afford sulfonium salts which, in turn, undergo solvolysis to alcohols, ethers or amides. The method provides the key step in a synthesis of (±)-aspidospermidine. (ii) Hypophosphite salts and hypophosphorous acid, on the other hand, form C_C bonds with reductive termination. These economical reagents afford radicals efficiently, starting from aryl iodides, alkyl bromides, and alkyl iodides, and give very easy separation of products from by-products.
Biocatalysis. Biological systems for the production of chemicals
Authors: Held M. , Schmid A. , van Beilen J. B. , Witholt B.
Published: October 2007

Biocatalysis harnesses the catalytic potential of enzymes to produce building blocks and end-products for the pharmaceutical and chemical industry. Located at the interface between fermentation processes and petrol-based chemistry, biotransformation processes broaden the toolbox for bioconversion of organic compounds to functionalized products.
Dissolving biomolecules and modifying biomedical implants with supercritical carbon dioxide
Authors: Webb Paul B. , Marr Patricia C. , Parsons Andrew J. , Gidda Harmanjit S. , Howdle Steven M.
Published: October 2007

We describe two methodologies for dissolving ionic/polar species in scCO2. Both lead to a broadening of the range of applications for scCO2. Fluorinated surfactants may be used to prepare water in carbon dioxide microemulsions to allow solubilization of ionic and biological species. We outline also the preparation of scCO2 soluble metal precursors that can be impregnated efficiently into polymeric substrates. Further processing by heat or UV light leads to metallic particles distributed throughout a polymer substrate. The clean synthesis of such composites can be applied to the development of improved medical implants.
Diels_Alder reactions in water
Authors: Otto Sijbren , Engberts Jan B. F. N.
Published: October 2007

This review illustrates how water, as an environmentally friendly solvent, can have significant additional benefits when it is used as a solvent for the Diels_Alder reaction. The mechanism by which the unique properties of water enhance the rate and selectivity are discussed. Also, possibilities for the achievement of further increases in rate and enantioselectivity of aqueous Diels_Alder reactions through Lewis-acid and micellar catalysis are reviewed.
Green Lewis acid catalysis in organic synthesis
Authors: Kobayashi Shū , Manabe Kei
Published: October 2007

New types of Lewis acids as water-stable catalysts have been developed. Metal salts such as rare earth metal triflates can be used in carbon_carbon bond-forming reactions in aqueous media. These salts can be recovered after the reactions and reused. Furthermore, Lewis acid_surfactant-combined catalysts, which can be used for reactions in water without using any organic solvents, have been also developed. Finally, Lewis acid catalysis in supercritical carbon dioxide has been successfully performed. These investigations will contribute to development of environmentally friendly Lewis acid catalysis.
Ionic liquids. Green solvents for the future
Authors: Earle Martyn J. , Seddon Kenneth R.
Published: October 2007

Ionic liquids, being composed entirely of ions, were once mainly of interest to electrochemists. Recently, however, it has become apparent that, inter alia, their lack of measurable vapor pressure characterizes them as green solvents, and that a wide range of chemical reactions (reviewed here) can be performed in them.
Chemical research needed to improve high-temperature processing of advanced ceramic materials (Technical report)
Authors: Kolar D.
Published: October 2007

Of the principal classes of engineering materials, ceramics are in many ways the most interesting and challenging. Many properties, or combination, of properties, not achievable with other classes of materials give ceramics enormous technical potential. The main obstacles that prevent the wider use of ceramics include insufficient reliability, reproducibility, and high cost. The physical basis of the processing steps is well established, however, the chemical reactions which occur during the high-temperature processing frequently influence the densification process and microstructure development of ceramics in an unpredictable way. Therefore, an ability to understand and control the chemical processes that occur during ceramic processing are necessary to advance and open up new uses for technical ceramics. The aim of this present report, resulting from discussions of an ad hoc group of ceramists and chemists, is to expose the areas of chemical research that can most benefit the processing, and further the use, of ceramic materials.
Guidelines for preservation of methodological choices in the publication of computational results: B. Semiempirical electronic structure calculations(Technical report)
Authors: Stewart James J. P.
Published: October 2007

Guidelines are presented to assist authors in preparing manuscripts that describe the results of semiempirical computations. These guidelines are not intended to recommend how semiempirical calculations should be done, but rather to ensure that the reader can have a clear understanding of what actually was done. They are written in a form to facilitate reprinting in original research journals and as information sheets that can be distributed to authors and reviewers.
Microelectrodes. Definitions, characterization, and applications (Technical report)
Authors: Stulík Karel , Amatore Christian , Holub Karel , Marecek Vladimír , Kutner Wlodzimierz
Published: October 2007

Theory, preparation,and applications of microelectrodes and microelectrode arrays are critically reviewed, and future trends in the field are outlined. An operational definition of a microelectrode is also recommended.
Nomenclature of Lignans and Neolignans (IUPAC Recommendations 2000)
Authors: Moss G. P.
Published: October 2007

Lignans and neolignans are a large group of natural products characterized by the coupling of two C6C3 units. For nomenclature purposes the C6C3 unit is treated as propylbenzene and numbered from 1 to 6 in the ring, starting from the propyl group, and with the propyl group numbered from 7 to 9, starting from the benzene ring. With the second C6C3 unit the numbers are primed. When the two C6C3 units are linked by a bond between positions 8 and 8' the compound is referred to and named as a lignan. In the absence of the C-8 to C-8' bond, and where the two C6C3 units are linked by a carbon–carbon bond it is referred to and named as a neolignan. The linkage with neolignans may include C-8 or C-8'. Where there are no direct carbon–carbon bonds between the C6C3 units and they are linked by an ether oxygen atom the compound is named as an oxyneolignan. The nomenclature provides for the naming of additional rings and other modifications following standard organic nomenclature procedures for naming natural products. Provision is included to name the higher homologues. The sesquineolignans have three C6C3 units, and dineolignans have four C6C3 units.
Spontaneous fission half-lives for ground-state nuclide (Technical report)
Authors: Holden Norman E. , Hoffman Darleane C.
Published: October 2007

Measurements of the spontaneous fission half-lives of nuclides of elements Z = 82 through 109 have been compiled (cutoff date of April 1998) and evaluated. Recommended values are tabulated along with total half-lives.
Determination of polar compounds, polymerized and oxidized triacylglycerols, and diacylglycerols in oils and fats: results of collaborative studies and the standardized method (Technical report)
Authors: Dobarganes M. C. , Velasco J. , Dieffenbacher A.
Published: October 2007

A description is given of the development by collaborative study of two standardized methods for the determination of polar compounds in oils and fats by adsorption chromatography using silica minicolumns, and for quantification of polymerized triacylglycerols, oxidized triacylglycerols, and diacylglycerols in polar compounds by high-performance size-exclusion chromatography. The first procedure is sensitive, allowing savings in time, solvents, and reagents as compared to the previous determination (Standard Method 2.507), while the second is very rapid, giving a detailed information on the main groups of compounds in fats and oils associated with hydrolysis, oxidation, and thermal polymerization. Both methods are useful for the analysis of used frying fats as well as for the analysis of virgin or refined oils.
Formylation of carbohydrates and the evolution of synthetic routes to artificial oligosaccharides and glycoconjugates
Authors: Dondoni Alessandro
Published: October 2007

A highly effective method for the synthesis of formyl C-glycosides is described via addition of 2-lithiothiazole or 2-lithiobenzothiazole to sugar lactones, deoxygenation of the resulting ketols, and releasing of the formyl group from the heterocyclic ring. The synthetic utility of these sugar aldehydes is demonstrated by the development of synthetic methods to more elaborate C-glycosides. These include various (1-6)-C-disaccharides and some higher oligomers up to a C,C,C,C-pentasaccharide; C-glycosyl amino acid isosteres of N-glycosyl asparagines; the methylene isostere of β-Δ-galactosyl ceramide; linear and cylic (2-1)-ketoside oligomers. An alternative synthesis of ethylene-bridged glycosyl asparagine isosteres is illustrated by the use of ethynyl C-glycosides as starting materials.
Glyoxylic acid derivatives in asymmetric synthesis
Authors: Jurczak Janusz , Bauer Tomasz
Published: October 2007

Synthesis of chiral derivatives of glyoxylic acid with special emphasis on N-glyoxyloyl-(2R)-bornane-10,2-sultam is presented. Investigation of glyoxylic acid chiral derivatives in various stereocontrolled organic syntheses showed their excellent ability to provide products of high optical purity. Application of our methodology to the synthesis of natural products and their analogs is presented.
Application of directed evolution in the development of enantioselective enzymes
Authors: Reetz Manfred T.
Published: October 2007

A novel approach to developing enantioselective enzymes for use in organic chemistry has been devised which is independent of structural or mechanistic aspects. The underlying idea is to combine appropriate methods of random mutagenesis, gene expression, and high-throughput screening for enantioselectivity. If these actions are performed in repetitive cycles, an evolutionary pressure is created that leads to sequential improvements of the enantioselectivity of a given enzyme-catalyzed reaction. The concept is illustrated by an example involving the lipase-catalyzed hydrolytic kinetic resolution of an α-chiral ester, the enantio-selectivity increasing from ee = 2% (E =1.1) for a wild-type enzyme to ee = 90-93% (E = 25) for the best mutants.
Allylic boron and zinc derivatives in synthesis and transformations of nitrogen heterocycles
Authors: Bubnov Yu. N. , Klimkina E. V. , Zhun' I. V. , Pastukhov F. V. , Yampolsky I. V.
Published: October 2007

Reductive allylation of certain nitrogen heterocycles (indoles, isoquinoline, 4-vinylpyridine, and lactams) with allylic boron and zinc derivatives is presented.
Vinylogous aldol reaction of heterocyclic silyloxy dienes. Application in synthesis
Authors: Casiraghi Giovanni , Zanardi Franca , Rassu Gloria
Published: October 2007

A versatile, readily accessible triad of 2-enoxy silane synthons derived from furan, pyrrole, and thiophene is presented. These heterocycles, in reacting with carbonyl and carbonyl-related acceptors, act as vinylogous nucleophile modules, giving rise to diverse, functionality-rich, γ-substituted α,β-unsaturated carbonyl constructs. These, in turn, are invaluable platforms onto which further functional elements and chirality may be introduced. A couple of appealing applications—the variable construction of a repertoire of carbasugars and a library of annonaceous acetogenin segments—have been chosen to illustrate the viability of this vinylogous aldol approach.
Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, P. R. China
Authors: Ma Shengming , Li Lintao , Wei Qi , Xie Hexin , Wang Guangwei , Shi Zhangjie , Zhang Junliang
Published: October 2007

The hydrohalogenation reactions of electron-deficient allenes, such as 1,2-allenyl ketones, carboxylic acids, esters, amides, nitriles, sulfoxides, sulfones, and phosphine oxides with MX in HOAc, CF3COOH-HOAc, CF3COOH or AlCl3/H2O, afforded β-halo-β,γ-unsaturated functionalized alkenes. The regioselectivity of the reaction could be controlled by the reaction conditions.
Bicyclopropylidene. A unique tetrasubstituted alkene and versatile C6-building block for organic synthesis
Authors: Molander Gary A.
Published: October 2007

Bicyclopropylidene (4), now readily available in preparatively viable quantities, is evolving as a useful C6 building block for organic synthesis due to its enhanced reactivity at the C-H, the C=C, as well as both types of C-C single bonds. Monosubstituted derivatives are accessible by deprotonation/electrophilic substitution. Di- and tetrasubstituted bicyclopropylidenes are best made by copper-mediated reductive dimerization of bromolithiocarbenoids. The 1,3-dipolar cycloadducts of nitrones rearrange to spirocyclopropanated piperidones, palladium-catalyzed codimerizations with acrylates occur with opening of one of the rings to yield precursors to bicyclo[3.3.0]octene and bicyclo[5.3.0]decene skeletons. Silicon-heteroatom bonds can be added across the double bond of 4 under palladium catalysisjust like across a C텡C triple bond, and carbopalladation of the double bond in 4 occurs more rapidly than that in an acrylate. A variety of new three-component reactions of 4 with alkenyl as well as aryl halides and dienophiles have been developed and extended to be carried out in a combinatorial sense, even on a polymer support, with an additional dimension added in the cleavage step. Most of the reported reactions of bicyclopropylidene (4) proceed with good to excellent yields.
Versatility of β-lactams in synthesis. Studies directed toward the synthesis of complex nucleoside antibiotics and some macrocyclic peptides
Authors: Palomo Claudio , Aizpurua Jesús M. , Ganboa Iñaki , Oiarbide Mikel
Published: October 2007

The diastereoselective [2+2] cycloaddition of α-hydroxyketene equivalents with chiral α,ω-oxyaldehyde-derived imines followed by the 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-promoted ring expansion of the resulting α-hydroxy β-lactam adducts provides an unconventional and short route to α-amino acid N-carboxy anhydrides (NCAs). The required enantiopure α,ω-oxyaldehydes were obtained either from the chiral pool or through the Sharpless AD methodology. Following the present strategy, several nonproteinogenic NCAs were synthesized, which were further coupled with α-amino acid esters giving rise to key fragments of some nucleoside antibiotics and macrocyclic peptides.
From phosphatriafulvenes to phosphabenzenes and stable six-membered phosphaallenes
Authors: Hofmann Michael A. , Bergsträßer Uwe , Regitz Manfred
Published: October 2007

Phosphatriafulvenes readily react with kinetically stabilized phosphaalkynes. Depending on the substituent at the phosphorus atom of the phosphatriafulvene, different six-membered phosphaheterocycles can be isolated. On the one hand, 1,3-diphosphabenzenes are formed, which can be isomerized thermally to diphospha dewarbenzenes or complexed by Cr(CO)3. On the other hand, 1,3-diphosphaisobenzenes are thus available. They are converted to bicyclic six-membered allenes via 1,3-dipolar cycloaddition to the P/C double bond.
Use of visible light. Second-generation titanium oxide photocatalysts prepared by the application of an advanced metal ion-implantation method
Authors: Anpo Masakazu
Published: October 2007

Titanium oxide catalysts were implanted with various transition-metal ions by a high-voltage acceleration technique, then calcined in O2 at around 723 K to produce photocatalysts capable of absorbing visible light, the extent of the red shift depending on the amount and kind of metal ions implanted. Such metal ion-implanted titanium oxide photocatalysts, specifically using Cr or V ions, were successful in carrying out various photocatalytic reactions such as the decomposition of NO into N2, O2, and N2O at 293 K, significantly under irradiation with visible light longer than 450 nm. In outdoor field tests, these Cr and V ion-implanted titanium oxide photocatalysts showed three to four times higher photocatalytic reactivity for the decomposition of NO under solar beam irradiation, as compared with the original unimplanted titanium oxide photocatalyst.
Selective monomethylation reactions of methylene-active compounds with dimethylcarbonate. An example of clean synthesis
Authors: Tundo Pietro
Published: October 2007

Dimethylcarbonate (DMC), an environmentally friendly substitute for dimethylsulfate and methyl halides in methylation reactions, is also a very selective reagent. Under batch conditions, with potassium carbonate as the catalyst, the reactions of DMC, used as the solvent of the reactions, with methylene-active compounds (arylacetonitriles and arylacetoesters, aroxyacetonitriles and methyl aroxyacetates, benzylaryl- and alkylaryl-sulfones) produce monomethylated derivatives, with a selectivity not previously observed (i. e., >99%). These are examples of "green chemistry".
Role of reference materials for the realization of physicochemical properties. Past, present, and future
Authors: Marsh Kenneth N.
Published: October 2007

Reference materials have long been considered essential for both calibration and checking the correct operation of equipment used for the determination of physicochemical properties. Up until the 1970s, the maintenance of pure reference materials and the means to verify their properties through measurement using state-of-the-art equipment was the prerogative of many national standards laboratories. Over the last 30 years, many of the standards laboratories have either limited or eliminated their activity in maintaining both reference materials and state-of-the-art measuring equipment. One reason is the ready availability of high-purity materials from commercial sources and the ease with which one can now determine purity. A second reason is the ready availability of instruments to measure digitally fundamental quantities such as time, temperature, length, frequency, and voltage accurately has enabled chemical calibration using reference materials to be replaced in many instruments by electrical calibration. At the same time, digitization has enabled the computerization of the whole measurement process. Such automated devices, if not checked with reference materials, can give highly reproducible results but have large systematic errors, leading to poor values. The role of physicochemical reference materials in the past and the present will be outlined, and their status in the future will be explored.
Endothermic microbial growth. A calorimetric investigation of an extreme case of entropy-driven microbial growth
Authors: von Stockar U. , Marison I. W. , Liu J.-S.
Published: October 2007

Life is almost always associated with the generation of heat. Thus far, all chemotrophic life forms that have been studied in calorimeters were found to be exothermic. Certain literature reports have even cast doubt on the existence of endothermic growth, even though thermodynamic principles do not rule it out. The present report describes the first experiments demonstrating the actual existence of chemotrophic life forms that take up heat rather than produce it.
Potentiometric Selectivity Coefficients of Ion-Selective Electrodes. Part I. Inorganic Cations (Technical Report)
Authors: Umezawa Yoshio , Bühlmann Philippe , Umezawa Kayoko , Tohda Koji , Amemiya Shigeru
Published: October 2007

Potentiometric selectivity coefficients have been collected for ionophore-based ion-selective electrodes (ISEs) for inorganic cations reported from 1988-1997. In addition to numerical values of K
(A,B)
pot together with the methods and conditions for their determination, response slopes, linear concentration ranges, chemical compositions, and ionophores structures for the ISE membranes are tabulated.
Temperature control modes in thermal analysis
Authors: Ozawa Takeo
Published: October 2007

Now we can use several temperature control modes, for example, isothermal run including stepwise heating and cooling, constant rate heating (or cooling), temperature control for sample thermal history, sample-controlled thermal analysis (SCTA or controlled-rate thermal analysis, CRTA), temperature jump, rate jump, temperature modulation, and repeated temperature scanning. Their advantages and drawbacks are reviewed with some illustrative examples, especially for application to kinetic analysis. The combined use of these varieties of temperature control mode is recommended by showing examples. Temperature modulation and repeated temperature scanning are discussed in comparison with temperature-modulated differential scanning calorimetry (DSC), and common and analogous points are elucidated. In relation to this, the possibility of the imaginary part of the overall reaction rate constant in complex reactions is postulated. Finally, these modes are classified and tabulated from two viewpoints, and other possible modes are shown.