bluuebunny/crossref_metadata_2025 huggingface dataset:
Nanotubes of the disulfides of groups 4 and 5 metals
Authors: Nath Manashi , Rao C. N. R.
Published: October 2007

Nanotubes of HfS2, ZrS2, NbS2, and TaS2 have been obtained by the reduction of the corresponding metal trisulfides in a stream of H2 (mixed with an inert gas in some cases) at elevated temperatures. The nanotubes have been characterized by transmission electron microscopy (TEM) and other techniques. These disulfide nanotubes make an important addition to the growing family of nanotubes of inorganic layered materials.
Organometallic precursor route to carbon nanotubes
Authors: Govindaraj A. , Rao C. N. R.
Published: October 2007

Multi-walled as well as single-walled carbon nanotubes are conveniently prepared by the pyrolysis of organometallic precursors, such as metallocenes and phthalocyanines, in a reducing atmosphere. Pyrolysis of organometallics alone or in mixture with hydrocarbons also yields aligned nanotube bundles with useful field emission properties. By pyrolyzing organometallics in the presence of thiophene, Y-junction nanotubes are obtained in large quantities. The junction nanotubes have a good potential in nanoelectronics. Carbon nano-tubes prepared from organometallics are useful for preparing nanowires and nanotubes of materials such as BN, GaN, SiC, and Si3N4.
Mesoscale organization of metal nanocrystals
Authors: Kulkarni G. U. , Thomas P. John , Rao C. N. R.
Published: October 2007

Nanocrystals of metals covered by alkanethiols organize themselves in two-dimensional arrays. We discuss such arrays of metal nanocrystals at length, with focus on the dependence of the structure and the stability of the arrays on the particle diameter and the distance between the particles. Three-dimensional superstructures of metal nanocrystals obtained by the use of alkanedithiols are examined. These ordered two- and three-dimensional structures of thiolized metal nanocrystals are good examples of mesoscale self-assembly. The association of metal nanocrystals to give rise to giant clusters with magic nuclearity provides an even more graphic demonstration of mesoscale self-assembly.
Structure and dynamics of monolayers on planar and cluster surfaces
Authors: Pradeep T. , Sandhyarani N.
Published: October 2007

Organized molecular assemblies have been one of the intensely pursued areas of contemporary chemistry. Among the various methodologies used to make organized monolayer structures, self-assembled monolayers (SAMs) have been attractive to many materials chemists owing to the simplicity of the preparative method and high stability. Advances in various techniques and their application in the study of SAMs have significantly improved our understanding of these molecular systems. These studies have been further intensified since the successful preparation of stable metal clusters protected with monolayers. This article reviews the structure, temperature-induced phase transitions, and associated dynamics of monolayers, principally in the context of our own work in this area. Alkanethiols on Au(111) and Ag(111) are taken as archetypal systems to discuss the properties of 2D SAMs; studies from our laboratory have been on evaporated thin films. Alkanethiols on Au and Ag cluster surfaces are taken as examples of 3D SAMs. Although our principal focus will be on alkanethiols, we will touch upon a few other adsorbate systems as well.
Assembling nanoparticles and biomacromolecules using electrostatic interactions
Authors: Sastry Murali
Published: October 2007

Nanotechnology is witnessing impressive advances on many different fronts. One of the key areas with important commercial implications concerns the assembly of nanoparticles to form thin films and superstructures by what is commonly known as the "bottom-up" approach. This paper covers some of the more recent developments in this fascinating field with particular emphasis on the work from the author's laboratory on assembly of nanoparticles using electrostatic interactions. The use of electrostatic interactions enables extension of the assembly protocols to the immobilization of biomacromolecules such as proteins/enzymes and DNA with exciting application potential.
Nonequilibrium processes for generating silicon nanostructures in single-crystalline silicon
Authors: Sen P. , Akhtar J.
Published: October 2007

The possibility of modifying existing materials through technology has become the recipe for preparation of advanced materials. Nonequilibrium processing of silicon through MeV ion irradiation will be shown here to yield interesting properties. We propose localization of vibrational energy following an ion irradiation process and their transport (nonlinear transport of energy) through linear chains of a single-crystalline lattice. The localization of energy can involve 3­4 atoms, and, hence, nanometer-sized entities evolve, distinguishable from the remaining periodic lattice owing to their unique interatomic distances. The energy required to produce these structures is supplied by a single high-energy heavy ion, incident normal to a suitable crystal face so as to lose energy by the electronic energy loss mechanism. These entities can be trapped at a desired location that leads to silicon nanostructures with modified band-gaps.
Solvothermal routes to capped oxide and chalcogenide nanoparticles
Authors: Gautam Ujjal K. , Ghosh Moumita , Rajamathi Michael , Seshadri Ram
Published: October 2007

We review our recent contributions to the use of solvothermal methods for the preparation of different oxide and chalcogenide nanoparticles. We have prepared sub 10-nm g-Fe2O3, ZnFe2O4, and CoFe2O4 particles by the decomposition of the corresponding cupferron complexes in the presence of n-octylamine or n-dodecylamine in solvothermal toluene. Similarly, dodecanethiol-capped chalcogenide nanoparticles of CdSe have been prepared by reacting cadmium stearates with H2Se under solvothermal conditions. The H2Se is generated in situ by the reduction of Se by tetralin. Using this latter technique, we have also been able to prepare PbSe and PbI2 in toluene under solvothermal conditions, albeit in bulk (rather than nanocrystalline) form. In the preparation of PbI2, HI is prepared by the in situ reduction of I2 by tetralin.
Stars and stripes. Nanoscale misfit dislocation patterns on surfaces
Authors: Pushpa Raghani , Narasimhan Shobhana
Published: October 2007

Close-packed metal surfaces and heteroepitaxial systems frequently display a structure consisting of regularly spaced misfit dislocations, with a network of domain walls separating face-centered cubic (fcc) and hexagonal close-packed (hcp) domains. These structures can serve as templates for growing regularly spaced arrays of nanoislands. We present a theoretical investigation of the factors controlling the size and shape of the domains, using Pt(111) as a model system. Upon varying the chemical potential, the surface structure changes from being unreconstructed to the honeycomb, wavy triangles, "bright stars", or Moiré patterns observed experimentally on Pt(111) and other systems. For the particular case of Pt(111), isotropically contracted star-like patterns are favored over uniaxially contracted stripes.
Mesoscopic domains of cobalt nanocrystals
Authors: Pileni M. P.
Published: October 2007

In this paper, various mesoscopic structures made of cobalt nanocrystals are presented. It is demonstrated that the evaporation time and the application of an external magnetic field during the evaporation process play a major role in the shape of mesostructure obtained. Their magnetic properties change with the shape of the mesostructure.
Electrochemical tuning and mechanical resilience of single-wall carbon nanotubes
Authors: Ghosh Shankar , Teredesai Pallavi V. , Sood A. K.
Published: October 2007

Single-wall carbon nanotubes (SWNTs) are fascinating systems exhibiting many novel physical properties. In this paper, we give a brief review of the structural, electronic, vibrational, and mechanical properties of carbon nanotubes. In situ resonance Raman scattering of SWNTs investigated under electrochemical biasing demonstrates that the intensity of the radial breathing mode varies significantly in a nonmonotonic manner as a function of the cathodic bias voltage, but does not change appreciably under anodic bias. These results can be quantitatively understood in terms of the changes in the energy gaps between the 1D van Hove singularities in the electron density of states, arising possibly due to the alterations in the overlap integral of π bonds between the π-orbitals of the adjacent carbon atoms. In the second part of this paper, we review our high-pressure X-ray diffraction results, which show that the triangular lattice of the carbon nanotube bundles continues to persist up to ∼10 GPa. The lattice is seen to relax just before the phase transformation, which is observed at ∼10 GPa. Further, our results display the reversibility of the 2D lattice symmetry even after compression up to 13 GPa well beyond the 5 GPa value observed recently. These experimental results explicitly validate the predicted remarkable mechanical resilience of the nanotubes.
Substrate temperature dependence of electrical conduction in nanocrystalline CdTe:TiO2 sputtered films
Authors: Sharma S. N. , Shivaprasad S. M. , Kohli Sandeep , Rastogi A. C.
Published: October 2007

TiO2 thin films with high volume fraction (∼50­70 %) of CdTe nanoparticles were prepared by radio frequency (rf) magnetron sputtering from a composite TiO2:CdTe target. With increase in substrate temperature Ts from room temperature (RT ∼300 K) to 373 K, a transition from an ordered structure exhibiting metallic-type conduction to a disordered structure exhibiting nonmetallic-type conduction was observed for annealed nanocrystalline CdTe:TiO2 films. The annealed RT-deposited films showed a large coalescence of distinct islands (size ∼0.3­0.7 µm) mainly of Cd and CdTe, and as result, a 3D network was realized. For metallic regime films, electrical conduction is essentially due to electrical percolation through Cd/CdTe crystallites embedded in an amorphous TiO2 matrix. However, the annealed high Ts films consisted of noncoalescent, small islands (size ∼0.15­0.3 µm) of Cd and CdTe embedded in amorphous TiO2 matrix. Here, the conduction is essentially by hopping mechanism via thermally activated tunneling.
Sensors and sensor arrays based on conjugated polymers and carbon nanotubes
Authors: Dai Liming , Soundarrajan Prabhu , Kim Taehyung
Published: October 2007

The need for cheaper, faster, and more accurate measurements has been a driving force for the development of new sensing devices. As is well known, the electrical conductivity of conjugated polymers can be reliably regulated over a wide range through interactions with electron acceptors and donors. This, together with the fast optical dynamics (either in the ground or excited states) of most conjugated polymers, has made conjugated polymers very attractive as transducer-active materials. On the other hand, the unusual electronic, mechanical, and thermal properties of carbon nanotubes have also led to their potential use in a wide range of devices, including sensors. In particular, the ability of carbon nanotubes and their derivatives to operate as gas and glucose sensors has been recently demonstrated. This article provides a status review on the research and development of sensors and sensor arrays based on conjugated polymers and carbon nanotubes. The unique features characteristic of most reported sensing transduction modes related to conjugated polymers and carbon nanotubes are discussed, along with their pros and cons.
Solubility and crystallization in biological fluids and the problems of life and health
Authors: Gutzow I. , Atanassova S. , Neykov K.
Published: October 2007

An analysis is given of several biologically important processes, connected with the crystallization and kinetics of liophilization in aqueous physiological solutions. These are glass formation and vitrification of life, precipitation of slightly soluble salts and kinetics of crystallization in human urine, and the solution of CaOX concretions under the influence of biocompatible solubilizators, which are normal constituents of human urine. The problems investigated experimentally are treated in the framework of the capillary theory of nucleation and the Debye–Hückel model of ionic solutions.
Calculation of the free Gibbs energy of phase transitions using solubility data. 1. The system Na2SO4-Na2Se04-H2O at 15 °C: Stable and metastable
Authors: Balarew Chr.
Published: October 2007

The solubility isotherms of the systems Na2SO4 ·10H2O–Na2SeO4·10H2O–H2O and Na2SO4·7H2O–Na2SeO4 ·7H2O–H2O have been investigated at 15 °C. It is established that discontinuous series of mixed crystals are formed in both systems. Two methods of calculation of the free Gibbs energy of phase transition at the interruption point of the solubility diagrams are used: (i) on the basis of the composition of the two mixed crystal types, which are in equilibrium with the saturated solution in the eutonic point of the system, and (ii) from the distribution coefficients between each of the mixed crystal phases and their saturated solution, using both experimentally obtained values and calculated distribution coefficients for ideal isomorphic mixing. The data found by the two methods exhibit very good agreement. It is established that the free Gibbs energy of the phase transition in the case of decahydrates is lower than in the case of heptahydrates. This fact is considered as a confirmation of the buffering action of water molecules with respect to the distortion of the crystal structures of the pure salts provoked by the formation of mixed crystals.
Nonlinear mass transfer and hydrodynamic stability in solubility phenomena
Authors: Bojadjiev Chr.
Published: October 2007

The dissolution of gases, liquids,or solids in liquids is a heterogeneous reaction, and in many cases, the reaction rate is limited by a diffusive transfer of substance in the boundary layer at the face interphase. In modern industry, intensive interphase mass transfer processes are accomplished by large concentration gradients. This can result in a set of nonlinear effects and the difference between experimental data and predictions of the linear mass transfer theory. One of the main nonlinear effects is a result of the induction of a secondary flow at the interface boundary. This can lead to essential changes of the dissolution rate and the hydrodynamic stability of the system.
New mechanism for the dissolution of sparingly soluble minerals
Authors: Tang Ruikang , Nancollas George H.
Published: October 2007

A requirement for the determination of the solubility of minerals is to ensure that equilibrium has been reached. Recent constant composition dissolution studies of sparingly soluble calcium phosphates have revealed an interesting and unusual behavior in that the rates decreased, eventually resulting in effective reaction suppression, even though the solutions remained undersaturated. Traditional theories of dissolution assume a volume diffusion-controlled mechanism with reaction continuing until true equilibrium has been reached. The new results for sparingly soluble salts point to the importance not only of particle size on the dissolution rate but also the participation of critical phenomena. Although the crystal size decreases during dissolution, when the reaction is controlled by poly-pitting (the formation and growth of pits), the edge free energy increases at the very first stage of reaction owing to the creation of pits and dissolution steps. The constant composition experimental results demonstrate the development of surface roughness as the dissolution steps are formed, implying an increase of the total edge length during the reaction. This is an exactly analogous mechanism to that of crystal growth, in which the formation of embryos of critical size plays a key role in the overall mechanism. In contrast to crystal growth, dissolution is a process of size reduction, and, when the particle size is sufficiently reduced, critical phenomena become important so that the influence of size must be taken into consideration. It is interesting to recognize that these critical phenomena are readily apparent for sparingly soluble minerals for which the critical conditions are attained much more readily. The results point to the importance of understanding the detailed mechanism of dissolution when attempts are made to measure, experimentally, the solubilities of sparingly soluble minerals.
Structural investigation of water and aqueous solutions by Raman spectroscopy
Authors: Rull F.
Published: October 2007

In the context of a long study of the dynamical properties of water and inorganic aqueous solutions using infrared (IR) and Raman spectroscopy,we present here recent results of the influence of salt concentration on the dynamics of water molecules. The main systems studied were salts of XnYm
type (where X = Li+, Na+, K+, Rb+, Cs+, Mg2+, Zn2+ and Y = Cl–,ClO4
–, NO3
–, SO4
–2).

The whole spectrum reflects the molecular and ionic interactions between solvent molecules and solvent–solute and solute–solute molecules. Nevertheless, each spectral region supplies different information about these intermolecular interactions.

The strong modifications in intensity and band profile undergone by the v(OH) band depends mainly on the nature of anions while cations have a weak influence. A picture of these different situations in a particular salt solution needs the support of a model of the dynamic structure of the water solvent. A discussion of the current state of the dynamical models of liquid water and new ideas on water dynamics are presented on the basis of the results obtained from the study of internal OH/OD vibrations of water in diluted mixtures of D2O/H2O.

Finally, a comparative analysis of the influence on the dynamics of water molecules under the concentration of perchlorate and chloride salts of monovalent cations in water and isotopic D2O/H2O mixtures was undertaken using Raman spectroscopy.
Derivation of complete phase diagrams for ternary systems with immiscibility phenomena and solid–fluid equilibria
Authors: Valyashko V. M.
Published: October 2007

Four main types of binary fluid-phase diagrams and available experimental data on binary systems are used as a starting point for derivation of the systematic classification of binary complete phase diagrams by the method of continuous topological transformations. This method and the classification of binary phase diagrams, containing the boundary versions of phase diagrams with ternary nonvariant points, are applied to derive the main types of fluid and complete phase diagrams for ternary systems with one volatile component and immiscibility phenomena in two constituent binary subsystems. The results gained from this analysis of derived fluid and complete phase diagrams of ternary systems are represented.
Nomenclature of regular single-strand organic polymers (IUPAC Recommendations 2002)
Authors: Kahovec J. , Fox R. B. , Hatada K.
Published: October 2007

A structure-based nomenclature for regular single-strand organic polymers is described. In concept, a generic name for the polymer (ABC)
n
is poly(ABC), in which (ABC) is a constitutional repeating unit (CRU) representing the chemical structure of the polymer chain, and A, B, and C are the subunits that comprise the CRU. To provide a unique and unambiguous name, rules are given to identify the preferred CRU and to name it using the names of A, B, and C based on current organic nomenclature. Provisions are made for naming end-groups of the polymers and the polymer substituents. In addition, the document contains a glossary of concepts and definitions, a list of common subunit names, and a variety of examples of structure-based polymer names. The document is a revision of the 1975 Rules.
Natural and synthetic substances related to human health (IUPAC Technical Report)
Authors: Topliss J. G. , Clark A. M. , Ernst E. , Hufford C. D. , Johnston G. A. R. , Rimoldi J. M. , Weimann B. J.
Published: October 2007

There is a widespread belief on the part of the general public that natural substances are inherently superior to synthetic substances with regard to efficacy and safety in matters related to human health. This question is examined by reviewing the therapeutic use of drugs and herbal medicine preparations, the role of vitamins and nutrients, and the effects of toxic substances. A comparison of the characteristics of natural and synthetic substances within these categories shows a similar range of favorable and unfavorable effects. It is apparent that molecular structure and dose determine the effect of substances on human health, not whether they are of natural or synthetic origin.
ABCG subfamily of human ATP-binding cassette proteins
Authors: Lorkowski Stefan , Cullen Paul
Published: October 2007

ATP-binding cassette (ABC) proteins form one of the largest known protein families and have been found in all known organisms. Most members of the human ABC protein family are membrane-spanning transporters that use energy derived from the hydrolysis of ATP to transport specific substrates across cell membranes. Mutations in certain human ABC transporters of the subfamilies A, B, C, and D have been shown to cause a wide variety of inherited diseases such as the lung condition cystic fibrosis, the nervous degenerative condition adrenoleukodystrophy (of Lorenzo’s Oil fame), hereditary macular degeneration of the eye (Stargardt’s disease), and inherited deficiency of circulating high-density lipoproteins (Tangier disease or familial hypoalphalipoproteinemia). Very recent studies showed that mutations in two members of the subfamily G of human ABC transporters (ABCG5 and ABCG8) cause a condition called sitosterolemia in which plant sterols accumulate in the body and may be responsible for influencing total body sterol homeostasis. In addition, other members of the subfamily G, namely ABCG1 and ABCG4, have also been shown to be involved in cellular lipid trafficking and are thought to play important roles during foam cell formation of human macrophages. By contrast, ABCG2 is a multidrug resistance transporter.

In this review, we focus on the current knowledge and physiological background of the members of the subfamily G. We also present new insights on the evolutionary relationship of human and nonhuman ABCG proteins.
Thick films of ceramic superconducting, electro-ceramic materials
Authors: Altenburg H. , Plewa J. , Plesch G. , Shpotyuk O.
Published: October 2007

The use of thick films becomes more and more important in particular for electronic and microelectronic applications. The term “thick film ” does not relate so much to the thickness of the film but more to the kind of deposition. Thick films are made by low-priced processes such as doctor (dr) blading, screen-printing, or spraying methods, etc. The preparation of thick films of ceramic material by these methods generally implies a processing sequence of the following steps: preparation of the oxide powders; preparation of pastes and slurries; painting/printing, etc.of the pastes onto a suitable substrate; drying at low temperature; and sintering at high temperature to get a consolidated layer. These technologies and the fabricated thick films of thermoresistive and superconducting materials will be discussed.
Catalyic conversion of hydrocarbons in zeolites from first principles
Authors: Benco Ľubomír , Demuth Thomas , Hutschka François
Published: October 2007

The application of the density functional techniques to processes of the conversion of hydrocarbons in zeolites has been reviewed. The conversion of hydrocarbons over zeolites is an important industrial process. The microscopic steps of the conversion, however, are still not satisfactorily understood. In order to examine reaction pathways, both static and molecular dynamics density functional theory (DFT) calculations have been performed. Simulated structural and spectral properties compare reasonably with experimental data. Comparison of energies of physisorption and chemisorption indicates possible reaction channel of the conversion through the chemisorption at the specific O-sites of the zeolite.
Nonvacuum-based deposition techniques for superconducting ceramic coatings
Authors: Van Driessche I. , Penneman G. , Bruneel E. , Hoste S.
Published: October 2007

The widespread use of vacuum-based techniques for the deposition of ceramic coatings with specific electric, magnetic, optical, and mechanical properties is well established in the research environment, and some of them have been implemented in a variety of industrial processes. However, obtaining uninterrupted deposition at high speed, increasing flexibility in composition and in film thickness, and attaining independence of geometric constraints are areas in which many vacuum techniques will need sustained development in order to answer industrial demands. The development of the next generation of deposition methods, which could alleviate some of these shortcomings and which are based on deposition under atmospheric environment and from aqueous precursor materials, is a real challenge for the community of solid-state chemists and delineates the subject of this overview.
Silicon-based ceramics from polymer precursors
Authors: Interrante Leonard V. , Moraes K. , Liu Q. , Lu N. , Puerta A. , Sneddon L. G.
Published: October 2007

A hyperbranched polycarbosilane of the type [R3SiCH2−]
x
[−SiR2CH2−]
y
[−SiR(CH2−)1.5]
z
[−Si(CH2−)2]
l
(R = H, –CH2CH=CH2, or OR) has been prepared, which was used as a source of inorganic/organic hybrid materials and, through pyrolysis, as a precursor to inorganic solids with unusual microstructures and properties. A partially allyl-substituted derivative “AHPCS”, nominally ['Si(allyl)0.1H0.9CH2']
n
, has been extensively studied as a precursor to silicon carbide (SiC) and is now used commercially as a SiC matrix source for C- and SiC-fiber-reinforced composites and binder for particulate ceramics. The alkoxy derivatives, ['Si(OR)2CH2'], (R = Me, Et) yield, after hydrolysis and condensation, carbosilane/siloxane gels with unusually high surface areas (700–900 m2/g) and microporosity that is retained in the resultant SiOxCy ceramics formed after pyrolysis to 1000 °C. The fully condensed ['Si(O)CH2'] gel in the latter case was obtained as thin, adherent films on Si surfaces by spin coating and was found to exhibit dielectric constants as low as 2.0 after heating to 400 °C. The SiC precursor, AHPCS, has also been used recently, along with other polymeric precursors, to make two-phase (SiC/C and SiC/BN) amorphous ceramics that exhibit unusual microstructures and thermal/mechanical properties. These microstructures are formed during the mixing and thermosetting of the constituent polymers, which undergo phase separation due to their immiscibility. Certain of the SiC/C composites, which have the C phase uniformly distributed as ca.1-µm droplets in a SiCx matrix, exhibit high oxidation resistance, and microindentation tests on the SiC/BN system suggest unusual toughness.
Engineering and chemistry of the glass melting process
Authors: Nemec L.
Published: October 2007

Improved glass-melting technology, intelligent process control, glass quality control, and establishing novel melting conditions, are realized by different kinds of physicochemical models. The model application is preceded by the analysis of homogenization processes, i.e., heating, dissolution, or vitrification and refining. The energy consumption of the process, the pull rate and size of the melting space, and glass quality are the main technological factors taken into account. In the following step, the optimum conditions are applied to simplified and complex models or processes. The mentioned models are mostly represented by systems containing melt and numerous inhomogeneities (solid particles, bubbles).
Hydrothermally treated cement-based building materials. Past, present, and future
Authors: Ray A.
Published: October 2007

Hydrothermally cured or autoclaved cement-based building products have provided many challenges to researchers, manufacturers, and users since their inception nearly 100 years ago. The advantages, including the development of high strength within a few hours and a reduction of drying shrinkage, of the hydrothermal curing process have resulted in a variety of building products; inevitably, the technology of their production has undergone many stages of refinement. With the advent of nonconventional starting materials for the production of modern cements, and the push to utilize renewable resources to form blended cements, the chemical and physical make-up of hydrothermally cured building materials have changed considerably in recent years and will continue to change. It is, therefore, important to understand the chemical reactions taking place in an autoclave, and the consequent phase developments, if building materials produced by this process continue to be successful in the long term. A wide range of analytical techniques exists for characterizing the phase development in cement-based materials. The purpose of this paper is to illustrate the strength of thermal methods, especially when used in combination with other analytical techniques, in the understanding of hydrothermal reactions.
Importance of chemistry in high-tech ceramics design
Authors: Šajgalík P.
Published: October 2007

This paper deals with the role of chemistry in the design of high-tech ceramic materials. Grain boundary composition of polycrystalline ceramics dictates the hardness fracture toughness and creep resistance of liquid-phase sintered silicon nitride and silicon carbide materials.
Effects of iron oxidation states on the surface and structural properties of smectites
Authors: Stucki J. W. , Lee K. , Zhang L. , Larson R. A.
Published: October 2007

The oxidation state of iron (Fe) in the crystal structure of smectite clay minerals profoundly alters their physical-chemical properties. Among the properties affected are layer charge, cation exchange and fixation capacity, swelling in water, particle size, specific surface area, layer stacking order, magnetic exchange interactions, octahedral site occupancy, surface acidity, and reduction potential. Also affected is the surface chemistry of the clay, which alters clay–water and clay–organic interaction mechanisms. Rates and extents of degradation of pesticides are increased in the presence of reduced smectites compared to oxidized and reduced-reoxidized counterparts. A hypothesis regarding the mechanism for Fe reduction in clay minerals was first developed in 1963, and subsequent modifications have been proposed periodically through the present time. Recent studies clearly reveal that the process of Fe reduction involves more than the mere transfer of an electron to octahedral Fe(III) in the clay crystal. Ancillary reactions occur that produce significant structural modifications, some of which are reversible and others of which are not. Such changes in the crystal-chemical environment of structural Fe are thought to play a dominant role in altering the clay surface chemistry.
Examples of molecular switching in inorganic solids, due to temperature, light, pressure, and magnetic field
Authors: Varret F. , Bleuzen A. , Boukheddaden K. , Bousseksou A. , Codjovi E. , Enachescu C. , Goujon A. , Linares J. , Menendez N. , Verdaguer M.
Published: October 2007

We describe various molecular switching processes occurring in several types of inorganic solids: spin cross-over (SC) compounds, photomagnetic Prussian blue analogs (PBAs), and valence-tautomeric system. Their thermo-, photo-, piezo-, and magneto-chromic properties are illustrated by recent examples. A common description of their static properties by a two-level model is given.
Measurement of pH. Definition, standards, and procedures (IUPAC Recommendations 2002)
Authors: Buck R. P. , Rondinini S. , Covington A. K. , Baucke F. G. K. , Brett Christopher M. A. , Camoes M. F. , Milton M. J. T. , Mussini T. , Naumann R. , Pratt K. W. , Spitzer P. , Wilson G. S.
Published: October 2007

The definition of a “primary method of measurement ” has permitted a full consideration of the definition of primary standards for pH, determined by a primary method (cell without transference, Harned cell), of the definition of secondary standards by secondary methods, and of the question whether pH, as a conventional quantity, can be incorporated within the internationally accepted system of measurement, the International System of Units (SI, Système International d’ Unités). This approach has enabled resolution of the previous compromise IUPAC 1985 Recommendations [Pure Appl. Chem.
57, 531 (1985)]. Furthermore, incorporation of the uncertainties for the primary method, and for all subsequent measurements, permits the uncertainties for all procedures to be linked to the primary standards by an unbroken chain of comparisons. Thus, a rational choice can be made by the analyst of the appropriate procedure to achieve the target uncertainty of sample pH. Accordingly, this document explains IUPAC recommended definitions, procedures, and terminology relating to pH measurements in dilute aqueous solutions in the temperature range 5-50 °C. Details are given of the primary and secondary methods for measuring pH and the rationale for the assignment of pH values with appropriate uncertainties to selected primary and secondary substances.
Evolution of the secondary metabolite versus evolution of the species
Authors: Pietra F.
Published: October 2007

Four stereochemical series of diastereomeric polyhalogenated chamigrane sesquiterpenes -headed by obtusol, isoobtusol, rogiolol, and cartilagineol- suggest the existence of four lineages of red seaweeds in the genus Laurencia.On another front, concerning marine ciliates, euplotane sesquiterpenes characterize worldwide the morphospecies Euplotes crassus, well differentiated from Euplotes raikov, Euplotes rariseta, and Euplotes vannus, which furnish different-skeleton sesquiterpenoids, and the latter also C30-backbone isoprenoids. The latter three morphospecies, however, show polymorphism in the variability of their isoprenoids.
Advances in science and technology. Maintaining the effectiveness of the Chemical Weapons Convention
Authors: Gee John
Published: October 2007

A truly chemical weapons-free world can be achieved only with the active support and backing of the international scientific community. With input from the scientific and industrial communities, the Chemical Weapons Convention (CWC) was finalized in 1992 and entered into force in 1997. This paper provides a summary of the operations of the Organisation for the Prohibition of Chemical Weapons (OPCW), describes some of the major challenges facing the Convention, and suggests ways in which scientific advances might be able to improve the implementation of the Convention.
Verification under the Chemical Weapons Convention. A reflective review
Authors: Manley R. G.
Published: October 2007

The verification regime of the Chemical Weapons Convention (CWC) has now been in operation for more than five years. Its two principal components are the declarations to be made by States Parties and the on-site inspections carried out by the Organisation for the Prohibition of Chemical Weapons (OPCW) inspectors to verify these declarations. Its implementation has proved to be a resounding success - more than 1200 on-site inspections have been carried out in ver 50 of the Convention ’s 145 States Parties and many practical lessons have been learned. To ensure the continued success of the verification regime, some problems -particularly in relation to industry declarations, the updating of the approved list of inspection equipment, on-site sampling and analysis, and off-site analysis- need to be resolved.
Biotechnology and chemical weapons control
Authors: Wheelis M.
Published: October 2007

Biotechnology is revolutionizing the way new drugs are discovered, from a substantially empirical art to a rational, predictive process in which targets of drugs are selected on the basis of known physiology, then ligands that can bind to these targets are designed. The same process could be used to identify promising new chemical weapons (CW) agents, which would be synthesized from unscheduled precursors. Biotechnology thus has the potential of fueling CW proliferation. It can also aid the development of novel nonlethal chemical agents, the development of which could have a number of negative consequences for CW control.
Trends in processing and manufacturing that will affect implementation of the Chemical Weapons Convention
Authors: Parshall G. W.
Published: October 2007

Several new developments in synthesis science and manufacturing technology may affect the task of implementing the Chemical Weapons Convention (CWC) constraints on the production of toxic agents for military or terrorist purposes. The combination of automated synthesis methods and high-throughput screening protocols could potentially yield new toxic agents not specifically proscribed by the CWC, but such approaches are unlikely to seriously impact the work of the Organisation for the Prohibition of Chemical Weapons (OPCW) in the near future. On the other hand, new developments in manufacturing may have a serious impact on the work of the OPCW inspectors. The wide use of versatile, multipurpose production facilities in making fine chemicals complicates the task of discerning whether a particular facility is used only for nonprohibited purposes under the CWC. New catalytic processes and automated process control permit production of toxic chemicals with fewer emissions that contaminate the environment and might provide clues to the nature of the processes being conducted. Tiny microreactors operated continuously under computer control can produce significant quantities of toxic chemicals (including CWC scheduled compounds) with a very small “footprint”within a larger production facility. These technical developments together with the dispersal of chemical production facilities and skills may seriously complicate the tasks of the OPCW inspectors.
Strategies of conducting reactions on a small scale. Selectivity engineering and process intensification
Authors: Sharma M. M.
Published: October 2007

Advances in conducting reactions, new catalysts, and reactors have made manufacturing on a small scale very facile and even efficient. Selectivity engineering and process intensification permit minimalization of the chemical industry, and some demanding chemistry can be handled in a facile way.
Microreactors. Prospects already achieved and possible misuse
Authors: Löwe Holger , Hessel Volker , Mueller A.
Published: October 2007

Microreactors as a no el concept in chemical technology enable the introduction of new reaction procedures in chemistry, pharmaceutical industry, and molecular biology. Miniaturized reaction systems offer many exceptional technical advantages for a large number of applications. The large surface-to-volume ratio of miniaturized fluid components allows for significantly enhanced process control and heat management. Moreover, the unique possibilities of microchemical systems pave the way to a distributed point-of-use and on-demand production of extremely harmful and toxic substances.

On the other side of the coin,miniaturization of complete set-ups for chemical syntheses to a suitcase or even to a shoe-box size opens several possibilities to possibly use them as tools for terrorist attacks and to facilitate the clandestine manufacture of chemical agents. Microfabrication techniques are common and allow the machining of special materials (e.g., high-alloyed steel, titanium, ceramics, or glass). Meanwhile, micromachining techniques are available anywhere in the world. Therefore, these techniques are no longer unique nor proprietary and they cannot pre ent construction or distribution of microreaction systems by people with allegiance to a terrorist organization.
Terrorism. Industry prevention and the Chemical Weapons Convention
Authors: Kelliher Marybeth
Published: October 2007

The 11 September 2001 terrorist attacks introduced the United States to domestic and complex terrorism. According to terrorism experts, public and private sector targets are indistinguishable to the perpetrators of this evolved form of terrorism. The global chemical industry’s counteroffensive against international terrorism depends in part on implementation of the Chemicals Weapons Convention (CWC), long supported by the American Chemistry Council (ACC) and its sister associations in the International Council of Chemical Associations (ICCA). This paper describes the U.S. chemical industry’s response to September 11th and how adherence to the letter and spirit of the CWC helps prevent terrorism.
Conventional analytical methods for chemical warfare agents
Authors: Hill H. H. , Martin S. J.
Published: October 2007

Analytical methods that are currently used for the detection and identification of chemical warfare agents are reviewed and classified by the number of dimensions of information they provide. Single dimensional sensors target specific compounds or classes of compounds. Although they can be less expensive and more portable than multidimensional sensors, multidimensional sensors detect a broader threat spectrum with greater precision and accuracy. The recommendation for analytical field verification during inspections under the Chemical Weapons Convention (CWC) is to use simple two-dimensional analytical methods, such as gas chromatography (GC) or ion mobility spectrometry (IMS), for on-site screening of chemical weapons (CW) agents or to fully equip a modern, mobile analytical laboratory located in an airplane, which can be moved rapidly throughout the world to each inspection site and provide high-quality analytical data on-site.
Premliminary steps of the analytical process. From sampling to detection
Authors: de Castro M. D. Luque
Published: October 2007

An overview of current ways of automating or accelerating the preliminary steps of the analytical process is presented as a way of emphasizing the role of these steps in the final results. Sampling and weighing, dissolution, leaching or physical removal, in addition to clean-up and preconcentration are the steps discussed along with this overview.
Integrated chemical systems on microchips for analysis and assay. Potential future, mobile high-performance detection system for chemical weapons
Authors: Kikutani Yoshikuni , Tokeshi M. , Sato K. , Kitamori Takehiko
Published: October 2007

By analogy to unit operations (e.g., mixers, reactors, etc.) used in conventional chemical engineering, the concept of microunit operations permits the integration of complicated chemical systems onto a small microchip. A protocol for fabrication of such microchips is described, and its use is illustrated in several examples. In addition, the thermal lens microscope, which determines nonfluorescent species at the single-molecule level, is indispensable as an ultrasensitive detector for general use. Applications of microchip technology are given for chemical analysis, immunoassay, and full bioassay. Microchip analysis can provide very large enhancements in sensitivity and substantial reductions in measurement time as compared with conventional analytical methods.
Chemical and biological safety: Biosensors and nanotechnological methods for the detection and monitoring of chemical and biological agents
Authors: Varfolomeyev S. , Kurockhin I. , Eremenko A. , Efremenko Elena
Published: October 2007

The elaboration of highly sensitive and express methods for quantitative and qualitative detection and monitoring of chemical warfare agents (CWA), organophosphate and carbamate pesticides, compounds with delayed neurotoxicity, and pathogenic microorganisms and viruses is discussed. The application of potentiometric and amperometric biosensors, automatic biosensors discriminating the neurotoxins of different classes, is performed. The information about biosensors detecting the compounds with delayed neurotoxicity through the evaluation of “neurotoxic esterase”activity in the blood is presented. The use of immunochip technology for the detection of pathogenic microorganisms and viruses is demonstrated. The enzymatic methods of destruction of organophosphorus neurotoxins are considered as the base of new defense technology.
Transitioning analytical instrumentation from the laboratory to harsh environments
Authors: Turner R. B.
Published: October 2007

The development of sensitive analytical instrumentation for autonomous operation in harsh environments is a difficult and expensive process. The management of risk in this process is aided by the use of technology readiness levels (TRLs) and awareness that the exponential growth of costs through development militates very strongly against progressing the development prematurely. It is also essential to have a very clear view of the intended outcome at the earliest possible stage and to test the systems in realistic environments as soon and as often as possible. Economic production of large quantities of instruments requires considerable attention to the details of the production process and the control of materials; there is a constant battle against contamination. Future instrumentation might involve a combination of analytical techniques, but the desire for more selectivity and sensitivity must be balanced against cost, complexity, and reliability.
Impact of scientific developments on the Chemical Weapons Convention (IUPAC Technical Report)
Authors: Parshall G. W. , Pearson G. S. , Inch T. D. , Becker Edwin D.
Published: October 2007

This document was prepared as a report from IUPAC to the Organisation for the Prohibition of Chemical Weapons (OPCW) to provide an evaluation of scientific and technological advances in the chemical sciences relevant to the Chemical Weapons Convention (CWC). The report is intended to assist OPCW and its Member States in preparation for the First Review Conference to be held on 28 April 2003. The CWC, now ratified by 145 nations and in effect since 1997, totally prohibits the production, storage, or use of toxic chemicals as weapons of war. This report is based on an IUPAC Workshop held in Bergen**, Norway, 30 June to 3 July 2002. The report highlights developments in organic synthesis and changes in chemical plant design that will pose new challenges to the Convention, but it also describes recent and probable future developments in analytical chemistry that should assist in implementation of the Convention. The key issues identified at the Workshop are listed, and the findings and observations are summarized in 18 points.
The effects of sound patterning in poetry: A cognitive pragmatic approach
Authors: MacMahon Barbara
Published: October 2007

In this article I posit a pragmatic model of how sound-patterning in poetry contributes to interpretation, with particular attention to the cognitive processes involved. The model is based in cognitive pragmatics (relevance theory) and psycholinguistics (spreading activation models), and the focus here is largely on segmental patterning such as rhyme and alliteration, though there is also some reference to metrical features. The article draws on relevance theory notions of literary language conveying a range of weak implicatures and thus resulting in diffuse and non-propositional impressions (Sperber and Wilson 1995 [1986]), notions used so far in relevance theory approaches to literary features such as repetition and metaphor. The article develops Pilkington's (2000) argument that poetic form, in slowing down lines and anticipating rhyming words, allows for longer access and deeper exploration of information associated with lexical concepts. Such exploration can lead to a potentially wide range of interpretive material. Here I focus on associative, iconic, and mimetic effects, which, I argue, are enabled through the spreading of semantic properties along sequences of relatively contiguous similar sounding words, and through the association of formal properties with semantic and encyclopaedic information. Through the analysis, my aim is also to account for the instability of poetic interpretation. The argument is presented with reference to poetry by Pope and Keats.