Showing papers on "Chemical binding published in 1983"

Bragg's Rule of Stopping Power Additivity: A Compilation and Summary of Results

Abstract: Stopping power additivity, as expressed by Bragg's rule, is an important concept in many practical situations involving charged particles. Its validity has been investigated in a large number of studies and the wide range of data is confusing and at times conflicting. No previous comprehensive survey of the data has been undertaken. Thus a compilation is attempted here of a hundred or so papers which have included tests of Bragg's rule. Their main results are indicated and a summary is given of the effects of chemical binding and phase on the stopping power of heavy charged particles. Such effects are confirmed on the evidence available. Chemical binding effects become more significant for materials containing low-Z constituents and as energy falls into and through the transition region. Deviations of up to 50% have been observed in atomic stopping cross sections extracted from measurements on hydrocarbons. There is still some conflicting evidence appearing on phase effects. However, in general a broad consensus is emerging indicating significant differences in H/sub 2/O and organic and similar materials. Stopping cross sections in the vapor phase are greater by up to approx. 5 or 10% at energies around those of the stopping power maximum for protonsmore » and He ions. The effects decrease as energy increases.« less

Binary (e, 2e) spectroscopic study and momentum space chemistry of the two-electron systems He and H2

Abstract: The spherically averaged momentum distributions of the ground-state orbitals of the two-electron systems He(1s) and H 2 (1σ g ) have been determined using an improved high momentum resolution (Δ p ≈ 0.1 a o −1 fwhm) binary (e, 2e) spectromet The present result for He(1s) is in excellent agreement with the earlier (e, 2e) measurements. Similarly the result for H 2 (1σ g ) is in good agreement with earlier (e, 2e) measurements by Weigold et al. and Dey et al. However, for H 2 the recent measurement reported by Midgall et al. is not in agreement with the present or earlier work. The results are compared with theoretical momentum distributions calculated using wavefunctions of varying quality ranging from minimal basis to extended Hartree-Fock. In addition the binary (e, 2e) momentum distributions measured in the present work for the two-electron systems He and H 2 are found to be in good agreement with those derived from the experimental Compton profiles reported by Lee. Momentum density and density difference maps are used in comparison with their respective position-space counterparts to provide a complementary perspective to chemical binding phenomena and to further extend the study and understanding of momentum-space chemical properties. This alternative topographical view of chemical binding and bond formation is discussed in detail for the process H+H → H 2 (1σ g ) as a function of internuclear separation.

Nature of Insulin Binding to Plastic Bags

Abstract: The nature of insulin binding to plastic bags was evaluated to determine if it followed the physical laws of adsorption. To determine whether insulin is adsorbed on a liquid/air interface, the influence of foam in vials of radiolabeled insulin was evaluated. Using a bag-to-bag transfer method, the influence of regular insulin and detergent on radiotracer insulin binding was assessed. To evaluate the reversibility of the binding, bag pieces with bound radioactive insulin were washed with distilled water, detergent, and left to soak in detergent before measuring radioactivity. The radiolabeled insulin was adsorbed in the foam and then released into the bulk of the solution when the foam disappeared; hence, insulin can be entrapped in a liquid/air interface. The addition of regular insulin decreased the binding of the radiotracer insulin to the bag walls. The bound insulin could be removed by washing with water and detergent, but soaking in detergent did not remove a small residual quantity of the bound insulin, suggesting that minimal chemical binding or diffusion of the insulin into the plastic may occur. Insulin binding to plastic bags primarily follows the physical laws of adsorption.

Humus-bound residues of phenylamide herbicides: their nature, persistence and monitoring

Abstract: The chemical binding of certain pesticide residues to soil humus raises concerns about persistence, crop contamination and residue monitoring. Using radiochemical as well as conventional techniques, the nature, fate and analytical recovery of humus-bound 3,4-dichloroaniline (DCA), the principal residue of several phenylamide herbicides, were explored. Although not a growth substrate, DCA was extensively mineralized during a two-week incubation period in vitro by a Pseudomonas putida strain. Biodegradation occurred via oxidative deamination to 4,5-dichlorocatechol, followed by ring cleavage and dechlorination. However, in soil, the formation of humic complexes resulted in a DCA half-life of more than one year, and DCA was mineralized essentially at the rate of the humus fraction to which it became attached. Addition of aniline enhanced the mineralization of free and humus-bound DCA in vitro , as well as in soil. Humus-bound DCA did not appear to have adverse effects on soil microorganisms, but due to the microbial turnover of humus, DCA was liberated in intact form and gave rise to low-level crop contamination. The use of model monomers in the study of DCA attachment to soil humus revealed that quinoidal rather than phenolic groups constituted the principal attachment sites. DCA binding appeared to be a sequential reaction, leading from relatively loose to increasingly hydrolysis-resistant attachment. A modified Bleidner distillation process succeeded in recovering 98% of the solvent-unextractable DCA from freshly formed humic complexes. Laboratory studies as well as analysis of a field soil treated for 10 consecutive years by 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) indicated that DCA accumulation to problem levels in agricultural soils is unlikely.

Theoretical Compton profile anisotropies in molecules and solids. IX. Chemical bonding and 0–90 anisotropies in the first‐row diatomic hydrides AH

Abstract: An analysis of the parallel–perpendicular Compton profile anisotropies in the first‐row diatomic hydrides is presented. Both the total and molecular orbital anisotropies present trends that may be related to the nature of the chemical binding in the molecules.

Charge Distributions and Chemical Effects: A New Approach to the Electronic Structure and Energy of Molecules

Abstract: 1 Electronic Charge Distributions.- Electron Population Analysis.- Basis Functions.- 2 Charge Analysis of Simple Alkanes.- Inductive Effects of Alkyl Groups.- Back-Calculation of Atomic Charges from the Inductive Effects.- Comparison with Theoretical Population Analyses.- Conclusions.- 3 A Modified Population Analysis.- Criterion for Selecting a Theoretical Method for the Study of Molecular Properties Involving Charges.- A Modified Population Analysis.- Numerical Comparisons of Atomic Charges.- The "Most Even Electron Distribution".- On the Precision of Theoretical Charges.- Inductive Effects and Charge Distributions.- Conclusions.- 4 Charge Analyses Involving Nuclear Magnetic Resonance Shifts.- Relationships between Nuclear Magnetic Resonance Shifts and Atomic Charges.- Charge-Shift Relationships Involving sp2 Carbon Atoms.- Relationships Involving sp3 Carbon Atoms.- Relationships Involving Oxygen Atoms.- Charge Analyses.- Conclusions.- 5 The Molecular Energy, A Theory of Electron Density.- The Molecule in its Hypothetical Vibrationless State.- Energy Components in Isolated Atoms.- Relationships between Electronic, Orbital, and Total Energies in Molecules.- Binding of an Atom in a Molecule.- Non-Transferability of Bond Energy Terms.- Charge Dependence of Chemical Binding.- Evaluation of the aij Parameters.- Physical Interpretation of the aij Parameters.- Summary.- 6 Energy Analysis of Saturated Hydrocarbons.- The Boat and Chair Forms of Cyclohexane.- General Formulas for Saturated Hydrocarbons.- Definition of Charges Satisfying Eqs. 5.46-5.48.- Numerical Applications: Saturated Hydrocarbons.- Nonbonded Interaction Energies.- Approximate ?Em2Calculations of Saturated Hydrocarbons.- Conclusions.- 7 On the Role of Vibrational Energies.- Outline of Calculations.- Noncyclic Alkanes.- Cycloalkanes.- Ethylenic Hydrocarbons.- Carbonyl Compounds.- Ethers.- On the Quasi-Additivity of Vibrational Energies.- Ring Strain and Vibrational Energies.- Summary.- 8 Unsaturated Hydrocarbons.- Energy Formula for CnH2n Olefins.- Numerical Applications: CnH2n Olefins.- Bond-by-Bond Calculation of Olefins.- Exo- vs. Endocyclic Double Bonds.- Dienes, Allenes, Alkynes and Benzene.- Conclusions.- 9 Energy Analysis of Oxygen-Containing Compounds.- Charge Normalization.- Ethers.- Carbonyl Compounds.- Conclusions.- 10 Conclusion and Assessment.- Charge Distributions.- Molecular Energies.- Appendix Summary of Final Equations and Input Parameters.- Author Index.

Immobilisation of pollutants in the preparation of briquettes from organic products or waste products such as, for example, domestic refuse, sewage sludge and industrial hazardous waste

Abstract: To reduce the emission of pollutants in the thermal treatment (incineration, gasification, pyrolysis) of briquettes of organic products and waste products and to reduce the leachability of the residues, inorganic additives are added in the preparation of the briquettes With utilisation of exothermic heat of reaction and under pressure, chemical reactions are initiated and accelerated during the pressing step, so that chemical binding of pollutants takes place during pressing and during the pyrolysis and/or incineration to give sparingly soluble minerals, mixed oxides and natural or technical silicates

Gulfs of Northern Red Sea: Depositional Settings of Distinct Siliciclastic-Carbonate Interfaces: ABSTRACT

Abstract: The two narrow gulfs of the northern Red Sea, Gulf of Suez and Gulf of Eilat (Aqaba), have had different tectonic histories, but both display active interfingering of siliciclastic and carbonate facies. In an early stage of rifting, these embryonic seas are flanked by rugged mountains (about 2,000 m, 6,500 ft) and narrow coastal plains built of fans composed of poorly sorted terrigenous debris. An arid setting promotes aperiodic transport of siliciclastic sediments as well as deposition of evaporites (coastal sabkhas) and carbonates (reefs and associated sediments). Gulf margins prograde by a combination of rapid fan deposition during flash floods and subsequent carbonate stabilization of terrigenous fans and cones during intervening periods. High-resolution seismic and s de-scan sonar data suggest that narrow pathways for sediment transport are continually active on these features and probably accommodate much of the sediment transport to deep water during small discharge events. Large flash floods may completely overwash carbonates at the distal ends of fans, requiring renewed reef development. Rapid siliciclastic deposition, coupled with biological and chemical binding of carbonates as well as their tendency toward vertical buildups, results in steep slopes along the gulf margins. The Gulf of Suez is shallow ( 12 km, 7.5 mi) and geometrically complicated strait separates it from the northern Red Sea. In contrast, the Gulf of Eilat is deep ( 50 cm/sec, 20 in./sec)--tend to streamline reefs and sediment bodies, creating spindle-shaped carbonate platforms. The Gulf of Eilat has no mid-gulf platforms, but a complex of reef-dominated carbonates exists on gulf-normal structural blocks at the Strait of Tiran. A cross section reduction of this already narrow strait by lowering of sea level, reef growth, and/or sedimentation could drasticall change the basin-filling process through restricted flow by eliminating reef growth and initiating salt deposition. End_of_Article - Last_Page 541------------

A brief survey of the basic theoretical arguments on molecular structures and chemical bondings

Abstract: The authors briefly describe some theoretical approaches to the problems of chemical binding and molecular shapes and summarize their contribution to the description of the electronic structure of chemical species.

Apparatus for the cooling of solid residues of gasification

Abstract: The present specification describes and claims a method and apparatus for use in cooling the solid residue of gasification of a reactor operated at a pressure above atmospheric for the gasification of carbonaceous materials The residue of gasification is conducted out of the reactor into a cooling apparatus located therebelow and flows through the cooling apparatus from the top to the bottom thereof A cooling liquid is introduced into the solid residue in the upper region of the cooling apparatus and is metered such that the greater portion of the heat contained in the residue is eliminated in the form of heat of vaporization, sensible heat and chemical binding energy with the resultant steam and reaction products produced The remaining residual heat which corresponds to the difference between the desired final temperature and the temperature after cooling by the liquid, is eliminated by a gas blown into the bottom region of the cooling apparatus and/or by indirect heat exchange