Showing papers on "Chemical binding published in 1993"

A molecular photoionic AND gate based on fluorescent signalling

Abstract: MOLECULES that perform logic operations are prerequisites for molecular information processing and computation1–11. We12,13 and others14–16 have previously reported receptor molecules that can be considered to perform simple logic operations by coupling ionic bonding or more complex molecular-recognition processes with photonic (fluorescence) signals: in these systems, chemical binding (the 'input') results in a change in fluorescence intensity (the 'output') from the receptor. Here we describe a receptor (molecule (1) in Fig. 1) that operates as a logic device with two input channels: the fluorescence signal depends on whether the molecule binds hydrogen ions, sodium ions or both. The input/output characteristics of this molecular device correspond to those of an AND gate.

1993 ALCAN Award Lecture Chemical binding within and between inorganic rings; the design and synthesis of molecular conductors

Abstract: For a given number of skeletal atoms, the π-electron count of an unsaturated heterocycle can be modified by the incorporation of heteroatoms from different periodic groups. Sulfur and nitrogen are particularly effective in this regard, as their high electronegativity can stabilize electron-rich π-systems. A variety of aromatic, anti-aromatic, and radical systems can be prepared from admixtures of these elements. While the properties of these ring systems are interesting in their own right, the compounds are not without relevance in the design of new materials. The strong interannular interactions that are developed between these rings in the solid state makes them ideal candidates for the fabrication of molecular conductors. The origins and development of this area of research are the subjects of this presentation.

Strategies for the Immobilization of Antibodies

Abstract: The immobilization of antibodies in two-dimensional (physical adsorption and immobilization via binding proteins) and that in three-dimensional (chemical binding to polypeptide strands) coverage of solid matrices have been compared. Methods of optimizing exposure of the immunoglobulin paratope after binding to surfaces to permit unimpaired antibody-antigen complex formation have been investigated. At comparable antibody densities, a larger number of paratopes are available for complex formation when antibodies are immobilized by means of binding protein (Protein A, Protein G, secondary antibodies, and F(ab) 2 fragments of secondary antibodies) compared to physical adsorption. Using a primary coat of binding protein, reproducible immobilization of antibodies at densities up to two orders of magnitude lower than densities produced by physical adsorption and chemical immobilization is achieved. Binding of antibodies by means of polypeptide strands can be used to obtain multi-layers of IgG molecules. This method of immobilization gives the IgG molecules some flexibility in lateral positioning which leads to formation of clusters and increased attachment to the solid matrix, impairing the paratopes′ ability to form complexes. However, flexible attachment can permit separation of the IgG molecules by treatment with detergents (e.g., Tween) or with charged molecules (e.g., fluorescein) or by introducing binding proteins as spacers. The implications for engineering organized multilayers of antibodies for optical biosensors are reviewed.

Hematite identification in pseudo-particles of Moroccan rubified soils

Abstract: A B S T R A C T: In Moroccan calcareous mountains, red soils are distinguishable from brown soils, not only by their colour but also by their microaggregated structure. Clay mineral dispersion studies of these soils were carried out by increasing pH, after different treatments. The formation of the pseudo-particles appears to be dependent on the fixation of amorphous Fe on clay and on the chemical binding of those clays by amorphous Al-hydroxy-polycations. This can be explained by the high isoelectric point of ferric compounds such as ferrihydrite which are soluble in ammonium oxalate. Based on these results and using techniques of granulometric analysis, red clays aggregated in pseudo-particles were separated from less rubified clays. Hematite was identified in pseudoparticles from red soils and an increase of amorphous Fe has been shown in aggregated clays. These microstructural conditions characterizing rubification could also favour it, by creating microsites where water activity decreases and allows the crystallization of hematite by dehydration of ferrihydrite.

Superprecision mirror surface work method

Abstract: PURPOSE:To mirror surface-polish a worked surface without generating distortion, crack, thermal deterioration, etc., by generating a suspension flow in a direction along a fine region of the worked surface and also parallelly arranging a workpiece relatively in a direction tilted at a predetermined angle in a 0 to 90 deg. range relating to the axial direction of a work unit. CONSTITUTION:A long scale column-shaped work unit 1 is rotated while pressed by a fixed load to a plane-shaped worked surface 4 of a workpiece 2 to roll-in a suspension 5, uniformly dispersing superfine particles 3, between the work unit 1 and the worked surface 4, and the superfine particles 3 pass one after another in a direction along the worked surface 4 to perform surface work without causing deterioration by mutual action by one kind of chemical binding in an interface between the superfine particle 3 and the worked surface 4. Further, the workpiece 2 is relatively moved in a direction tilted at a predetermined angle in a 1 to 90 deg. range with an axial direction of the work unit 1 serving as the reference, and an influence by an irregular streaks, numerously formed along a circumference of the work unit 1 by a limit of work accuracy at the time of manufacturing the work unit 1, is removed to superaccurately mirror- surface polish the worked surface 4.

Generation of neutronic thermal data in support of space nuclear propulsion

Abstract: The scattering kernel data for [sup 7]LiH have been generated for the first time in the temperature range 50--1000 K. This is based on a phonon distribution function derived from both experimental data and theoretical calculations. A detailed study of the variation of the moderator temperature coefficient [alpha][sub m](T) with temperature, T, is carried out for a typical space nuclear reactor of the particle bed type. It is established that the moderator temperature coefficient due to chemical binding effects follows the relationship [alpha][sub m](T) = C F[sub v](H)[sup 1.6] where F[sub v](H) is the volume fraction of bound solid hydrogen and C is a normalization constant which depends on the moderator capture thermal cross section. The value 1.65 is to be compared with 1.54 [plus minus] 0.06 derived in a previous study where water scattering kernels are applied. For control and safety reasons, a minimization of this positive component temperature coefficient can be most effective by operating the moderator at high temperatures. Advantages of this approach are outlined. In addition, suggestions are made to render the overall temperature coefficient negative.

Chemical binding from the infinite dimensional limit

Abstract: The electronic structure of molecules calculated in the limit of infinite spatial dimensions is related to properties in three-dimensional space. In the spirit of the electrostatic theorem, we introduce the concept of antibinding and binding regions to visualize chemical binding. In addition, criteria are developed to determine the ionic or covalent character of the bond. The computational effort requires only the minimization of a multidimensional potential surface at the infinite dimensional limit, yet detailed information can be extracted. Numerical examples are given for the one-electron diatomic molecule

Manufacture of copper clad laminated plate

Abstract: PURPOSE:To enhance the adhesive power of an adhesive for copper foil and a base material impregnated with resin to a high level. CONSTITUTION:A process to add hydroxyl to the surface of copper foil is performed. A copper clad laminated plate is manufactured by stacking the base material impregnated with resin over the copper foil through a coupling agent in a laminated fashion and forming the stacked materials. Thus it is possible to enhance the binding power between the surface of the copper foil and the coupling agent through the chemical binding of hydroxyl to the coupling agent and improve the adhesive properties of the resin of the impregnated base material with the copper foil due to the coupling agent.

Energy dependence of particle reflection coefficient of ions from solid surfaces in the low energy region below 200 eV

Abstract: The reflection coefficients of Cu + and Ni + ions from graphite and gold film deposited on graphite in the energy range between 10 and 200 eV have been measured using the retention method. The reflection coefficient is determined from the difference between the charge number obtained by integration of the current of incident ion beam through the target and the retained number of incident ion species, not reflected from the target, obtained by means of the RBS technique. It is found that the reflection coefficients of both ions from graphite are less than 0.10 and that those from gold film are peaked at around 40–50 eV and their peak values are about 0.40. The experimental data are compared with the computer simulation data calculated by Eckstein et al. taking into account the chemical binding of neutral atoms of irradiated ion species at the surface.

Manufacture of metal core laminated plate

Abstract: PURPOSE:To enhance the adhesive properties of the resin with a metal plate as a core to a high level. CONSTITUTION:A process to donate hydroxyl to the surface of a metal plate is performed. A metal core laminated plate is manufactured by stacking a resin-impregnated base material over the metal plate through a coupling agent using a laminated molding technique. Thus it is possible to enhance the binding power between the surface of the metal plate and the coupling agent through a chemical binding reaction between hydroxyl and the coupling agent and also increase the effect of improving the adhesive properties between the metal plate and the resin of resin-impregnated base material due to the coupling agent.

Description of Contaminant Sediment-Water Interactions Using RECOVERY

Abstract: : Bedded sediments serve as sinks for many contaminants. Deposition of contaminants into the sediment begins a series of processes that may cycle contaminants back into the water column creating potentially adverse ecological impacts on aquatic biota. Sorption processes influence the mobility of contaminants from the sediment. Sorption is a general term referring to chemical binding that may be both reversible and irreversible. Desorption quantifies the reversibility of contaminants and is important because the availability of contaminants for uptake depend on the rate of desorption. The overall objective of this study was to use experimental data and a model simulation to predict desorption kinetics of organic contaminants and to assess the potential effect of contaminated sediment on the overlying water. In the experimental phase, several PAHs and polychlorinated biphenyl (PCB) 153 were quantified. Radiolabeled PAHs and PCB 153 were selected as tracers to determine the rate and magnitude of contaminant mobilization from five reservoir sediments. Data from the experimental phase will be used to verify and assess the applicability of the RECOVERY model in predicting desorption

Overhead Transparencies for Viewing Molecular Structure in Three Dimensions

Abstract: A major aim in the study of macromolecules such as DNA and proteins is to determine their structure and thus learn how they work One of the most exciting aspects of the discovery of the structure of DNA was that its simple, self-complementary organization immediately suggested how it could be replicated in each generation (Watson & Crick 1953) A protein's form is also crucial to its function Virtually all proteins seem to work by selectively interacting with other molecules (Doolittle 1985) It is the shape of the protein, including overall geometry as well as the surface arrangement of its charges, which allows the selective chemical binding that is the basis of its action The understanding of protein and nucleic acid shapes has been made easier by the development of computer technology that can produce images of the molecules as stereo pairs The left and right images of such a pair are separated on the page by a distance of about 6 cm and are meant to be viewed by the left and right eye, respectively This can be done with the use of a special viewing device, or it can be done unaided with a little practice A stereo pair gives the observer a three-dimensional view of the image This makes it easy to see the arrangement of the parts of a molecule and lets the viewer quickly understand its shape Research articles dealing with protein or nucleic acid structure commonly include stereo pair pictures of these macromolecules, often showing their interactions with other structures The enlarged projected image from an ordinary overhead transparency of such a stereo pair cannot be viewed successfully either unaided or with the usual viewing device, since the lines of sight from the two eyes would have to diverge in order to see the left and right images properly The eyes will not allow this divergence A useful stereo image for overhead projection can be easily produced, however, using technology available to most teachers An anaglyph is a picture that combines the two images of a stereo pair, one image in red being superimposed upon the second image which is green When viewed with glasses that carry a red and a green lens in the proper arrangement, the three-dimensional effect is seen Transparency-making films that produce a red or green image on clear film from any xerographed copy are available at modest cost [Century Business Products, Inc, 10089-C Allisonville Rd, PO Box 50653, Indianapolis, IN 48250, (317) 842-7293] An ordinary infrared transparency maker is used Inexpensive red/green glasses can also be purchased (The 3-D Zone, PO Box 741159, Los Angeles, CA 90004, (213) 662-3831) (I have found that a system using red and green works best Some stereo glasses are red and blue; be sure to specify red and green) It is best to obtain permission from the copyright holder when making overhead transparencies from any published material To construct an anaglyph from a stereo pair, the picture is copied by xerography, enlarging if necessary to give a size appropriate for use on an overhead projector The right and left images of the copied stereo pair are then cut apart; one is used to make a red-image transparency, and the other a greenimage transparency using the abovementioned films Next, an anaglyph is produced by accurately superimposing one transparency over the other in such a way as to give the proper threedimensional effect when the image is viewed with the red/green glasses This operation can be done easily and with adequate precision by placing the transparencies one over the other on a sheet of white paper, and adjusting the two images relative to each other while viewing with the red/green glasses (if the left eye image has been made in green, then the red lens should be in front of the left eye) Before this adjustment, one should examine the original stereo pair carefully in the usual way as described earlier in order to judge which parts of the molecule are meant to be seen as relatively distant from the viewer, and which near In the anaglyph, those parts which are most distant should be ones where the red and green images will be closest to each other (usually they should be made to overlap) The nearest parts will have the two images most separated from each other When the desired arrangement is achieved, as judged by the threedimensional appearance, the transparencies are taped together The top of the picture should be indicated, as the viewing orientation is important The process is one of trial and error, but I have not found it to be difficult The number of protein structures being solved is rapidly increasing, and it has become clear that there are some unforseen general principles of structure emerging There seems to be a limited number of structural categories for proteins In addition, certain substructures can be recognized as common to proteins that seem to have unrelated actions, though such substructures may function similarly in the proteins that contain them The use of three-dimensional images is particularly helpful for demonstrating these findings

Oscillating term of the inelastic scattering factor

Abstract: Formulas have been derived to calculate the factor of inelastic scattering of fast electrons by a molecular gas S(s) with inclusion of the chemical binding effect. In contrast to the free atoms approximation, the function S(s) has an oscillating term.

A New Electronegativity-Based Approach to Chemical Binding.

Abstract: A new theory of chemical binding modelled through the accumulation of electron density at the bond centre using the concepts of bond electronegativity and bond hardness is reported and shown to provide accurate prediction of bond energies for a number of diatomic and simple polyatomic (ABn) molecules.