Showing papers on "Chemical binding published in 1994"

Drug targeting with nanoparticles

Abstract: Nanoparticles are colloidal polymeric particles (size < 1000 nm) to which drugs are bound by sorption, incorporation, or chemical binding. After intravenous injection they normally distribute into the organs of the reticuloendothelial system (liver, spleen, lungs, bone marrow). However, their body distribution can be altered by coating with surfactants or with physiological components such as serum complement factors. The influence of these coatings on the body distribution and possible mechanisms for the alteration of this distribution are discussed. Differently coated nanoparticles can be used for the targeting of bound drugs to tumors, to the brain, and to inflamed areas in the body.

Chemical binding and electron correlation effects in x-ray and high energy electron scattering

Abstract: The total, inelastic and elastic intensities for x‐ray and high energy electron scattering from the ten‐electron molecules CH4, NH3, H2O, and HF have been calculated with configuration interaction wave functions. The probability density of the interelectronic distance or the radial intracule density is extracted from the intensities. The importance of basis sets, chemical binding, and electron correlation to the scattered intensities and the radial intracule density has been examined. It has been found that scattered intensities predicted with correlated wave functions agree well with experiment. Based on the electron pair distribution, the exchange and correlation holes in molecular systems have been briefly discussed.

Electronegativity, hardness, and a semiempirical density functional theory of chemical binding

Abstract: Chemical binding is modeled through interatomic charge transfer and accumulation of electron density at the bond center using the concepts of electronegativity and hardness parameters defined for the bond region. The generalized electronegativity and hardness parameters for the up- and down-spin electrons are also defined within the framework of spin-polarized density functional theory, leading to the formulation of covalent binding in molecules in terms of a two-way flow of unpaired electrons between the atoms. The associated energy changes corresponding to these descriptions are shown to provide quite accurate predictions of bond energies for simple heteronuclear diatomic molecules. © 1994 John Wiley & Sons, Inc.

Change of Hardness and Chemical Potential in Chemical Binding: A Quantitative Model

Abstract: In this paper we relate the change of chemical hardness and potential with the binding energies as the chemical binding takes place. We use a simple model to demonstrate that the hardness change is not only related to the binding energy of the molecule being formed, but also to the binding energies of the corresponding molecular cations and anions. Similar expressions are also derived for chemical potential. We have shown that our analysis can explain the existing data. The separated limit values of hardness and chemical potential are also derived. Two demonstrative calculations on the molecules H 2 and HF are presented. The future potential of this model is discussed.

A New Simple Density Functional Approach to Chemical Binding

Abstract: A new simple density functional approach to chemical binding in molecules is developed by representing the electron density reorganization of the constituent atoms in terms of the atomic charges and dipoles. The potential and capacity parameters for the atomic dipole are introduced, and a new equation for binding energy is derived. The calculated numerical results on the bond energies of a number of homo- and heteronuclear diatomics are shown to agree quite well with available data

No mimics O2 in the carotid body chemoreception.

Abstract: Nitric oxide (NO) by virtue of its chemical binding with biological heme compounds in competition with O2 (Martin et al., 1986), can mimic carotid body responses to PO2 changes. That NO is produced endogenously (Palmeret al., 1987) and that its application dilates blood vessels and improved coronary blood flow have long been known (Amezcua et al., 1989). More recently nitric oxide synthase (NOS) which generates NO from L-arginine has been localized in many tissues including blood vessels (Moncada et al., 1991), peripheral nerves (Gillespie et al., 1990) neurons in the central nervous system (CNS) and ganglia (Ross et al., 1990; Garthwaite, 1990; Bredt et al., 1990). The consensus is that the mechanism of effects of NO is due to its reaction with soluble guanylate cyclase, a heme compound, and an increased production of cGMP which mediates the physiological responses (Bredt & Snyder, 1992)

Investigations of Fungal Fruiting Bodies as Biosorbents for the Removal of Heavy Metals from Industrial Processing Streams

Abstract: The revival of interest in biotechnology has fueled research in many sectors of environmental biotechnology. The present paper describes research utilizing adsorbents prepared from wood-rotting mushrooms growing wild in tropical forests. Nine species of mushrooms were screened using copper(II) as the model adsorbate. While may species showed excellent potential, comparable to biosorbents reported in literature, Ganodernma lucidum emerged as the best biosorbent. This biosorbent was further developed for use in a packed—bed bioreactor for treatment that adsorption is by chemical binding to the biosorbent. ∗Present address: Department of Chemistry, Indian Institute of Technology, Kanpur, India.

AM-1 molecular orbital calculations of silica-alanine-nitrogen interaction.

Abstract: Chemical binding of proteins with bioactive surfaces is modeled using a semi-empirical molecular orbital theory (AM-1). The model calculates the optimized molecular structures of an amino acid (L-alanine) interacting with a cyclotetrasiloxane silica cluster (a four-membered hydrated silica ring). The calculated heats of formation for various orientations of alanine show +5 kcal/mol difference for binding via the −NH2 group following a condensation reaction with a pentacoordinate Si intermediate. Hydrogen bonding of the alanine via the COOH group occurs with +13 to +15 kcal/mole differences in heats of formation and imposes a highly specific geometric orientation on the amino acid. Association of a diatomic N2 molecule with the silica cluster before interaction with alanine inhibits formation of an intermolecular bond, as is observed experimentally in studies of silicaalanine epitaxy. © 1994 John Wiley & Sons, Inc.

Fiber optic detector and method for using same for detecting chemical species

Abstract: An optical sensing device for uranyl and other substances, a method for making an optical sensing device and a method for chemically binding uranyl and other indicators to glass, quartz, cellulose and similar substrates. The indicator, such as arsenazo III, is immobilized on the substrate using a chemical binding process. The immobilized arsenazo III causes uranyl from a fluid sample to bind irreversibly to the substrate at its active sites, thus causing absorption of a portion of light transmitted through the substrate. Determination of the amount of light absorbed, using conventional means, yields the concentration of uranyl present in the sample fluid. The binding of uranyl on the substrate can be reversed by subsequent exposure of the substrate to a solution of 2,6-pyridinedicarboxylic acid. The chemical binding process is suitable for similarly binding other indicators, such as bromocresol green.

Binding and Reduction of Silver Ions in Thin Polymeric Films of poly-[Fe(vbpy)2(CN)2],poly-vbpy

Abstract: Thin films of poly-[ Fe(vbpy),] (PF& formed an electrode surfaces by reductive electropolymerization of [ Fe(vbpy)3] (PF& (vbpy is 4-methyl-4’-vinyl-2,2’-bipyridine) undergo vbpy displacement with [NEt4] C N in acetonitrile to give poly[Fe(vbpy)z(CN)~],poly-vbpy. The dicyano films incorporate AgNOz forming poly[Fe(vbpy)z(CN)(CNAg)] (NO2),poly-vbpy as shown by FT-IR and XPS. Electrochemical reduction results in the formation of colloidal silver particles dispersed throughout the films. Under potential hold conditions, further aggregation occurs accompanied by diffusion to the film-electrode interface. Incorporation of AgNOz into films of poly[Fe(~bpy)~](PF6)2 also occurs but by partitioning rather than chemical binding. Electrochemical reduction gives colloidal Ago. Reduction of either film with AgN02 in the external solution results in the formation of C0.5 to 2-3 bm sized particles on the film surface as shown by SEM measurements.

Combined EPMA and AES depth profiling of a multilayer Ti-Al-O-N coating

Abstract: In order to compare thin-film electron probe microanalysis (EPMA) and Auger electron spectroscopy (AES) regarding reliability in quantifying chemical compositions of Ti-Al-O-N coatings with depth, a multilayer was prepared on a silicon wafer by using reactive ionized cluster beam deposition technique. Within a total thickness of about 25 nm the composition of the multilayer varied step by step from Ti-Al-O-N at the bottom to Al-O at the top. AES and, as an innovation, EPMA crater edge profiling was applied to measure the composition with depth. For quantification special thin-film EPMA techniques based on Monte Carlo simulations were applied. The chemical binding states of Al and Ti with depth were analysed using a high resolution energy analyser (MAC 3) for the AES investigations working in the direct mode. According to the deposition procedure the concentration profiles of the components varied with depth for both AES and EPMA measurements. AES provided a better depth resolution than EPMA. To get a true calibration of the depth scale an in-situ measurement method like an optical interferometry will be required. Assuming that the relative sensitivity factors are available AES depth profiling delivers concentration profiles with good accuracy. The new EPMA application provided quantitative depth profiles concerning concentration and coverage. For EPMA crater edge profiling the coating needs to be deposited on a foreign substrate because depth distributions of elements being present in both the layer and the substrate cannot be resolved. The combination of AES-depth profiling with EPMA crater edge profiling techniques is a powerful tool to analyse heterostructures quantitatively.

The pharmacokinetics of tiopronin as such is unknown

Abstract: The lack of investigation of the chemical binding of tiopronin to other compounds has hampered our understanding of the drug. From analytical studies [1, 2, 3], however, and from comparison with other thiols it can be deduced that in biological fluids several molecular species of tiopronin will be found including a) tiopronin as a free thiol (T-SH), the administered form, b)tiopronin as a symmetrical disulphide (T-S-S-T), or as mixed disulphide (T-S-S-R) with another low-molecular thiols (R-SH), such as cysteine and glutathione, and c) tiopronin as mixed disulphide with proteins (T-S-S-P) bearing a free thiolgroup.

Water-based manicure

Abstract: PURPOSE: To obtain a water-based manicure, improved in water resistance, capable of stably dispersing an inorganic powder therein without causing the caking even in the case of settling, readily redispersing the pigment and excellent in usability by coating and treating the surface of the inorganic powder with a water and oil repellent and blending the resultant pigment therein CONSTITUTION: This water-based manicure is obtained by blending an inorganic pigment treated by coating with a water and oil repellent and excellent in redispersibility of the inorganic pigment and usability The inorganic pigment is prepared by carrying out the sticking treatment or chemical binding treatment of the surface of the inorganic pigment with the water and oil repellent In the case of the sticking treatment, eg a compound having a fluoroalkyl group (eg a perfluoro polyether) can preferably be used In the case of the chemical binding treatment, eg a fluorosilane, etc, such as a perfluoroalkylsilane can suitably be used For example, talc, kaolin, sericite, mica or titanium-treated mica can be used as the inorganic pigment The water-based manicure is preferably blended with 01-10wt%, especially 02-40wt% inorganic pigment

Antifouling glass article having low reflectance

Abstract: PURPOSE:To obtain the subject glass article useful as CRT front glass of computers, etc., by forming an antireflecting film composed of a porous substance and an antifouling layer of a fluorosilane on the surface of a glass substrate. CONSTITUTION:A porous layer of this glass article is typically a skeletal layer prepared in treating the glass surface with an inorganic acid. This layer is obtained by immersing a silicate glass substrate in a supersaturated aqueous solution of silica in 1-4 mol hydrosilicofluoric acid per 1 at 25-50 deg.C for 1-4hr, eluting components other than silicon oxide in the surface layer of the substrate, e.g. components such as Na or K in the aqueous solution and removing the components from the surface layer. The thickness of the surface layer is preferably 10-300nm. A material for forming an antifouling layer may be a material having chemical binding properties to the porous surface and a low surface free energy. A fluorosilane-based material is preferred as an especially effective one and heptadecafluoromethyldichlorosilane, etc., are preferred. The antifouling layer is prepared by a vacuum CVD method.

Compressed light filler for thermosets and process for its manufacture

Abstract: Lightweight filler contg an (in)organic fibre carrier material in which thermoplastic polymer elastic hollow microbeads have been embedded by thermal adhesion or use of a binder The vol of the carrier material has been reduced by mechanical compression Pref the carrier material is a 5-500 (20-100) g web, felt, woven fabric, array or knit of high modular, 2-70 (5-25) mm short fibres or endless drawn elementary fibres, eg glass fibres, carbon fibres, drawn PE fibres or aramid fibres The thermal or chemical binding of the hollow microbeads may be carried out by dissolving them in monostyrene 5-300 (20-100) wt% binder (eg acrylate dispersion) is added to the filler (wrt) microbeads) The microbeads have a dia of pref 20-100 microns, a wt distribution of 3-40 (5-20) g per m /mm material thickness The uncompressed material comprises 10-60 vol% microbeads, whilst the compressed material comprises 50-95 (40-80) vol% microbeads The material is kept compressed by (in)organic sewing yarns and the stitches comprise individual seams (eg frayed binding), or the sewing yarns alternately cross over each other to form an interconnected pattern or network of seams (eg knit binding)

Energy depositions of protons in allotropic carbon ultrathin films

Abstract: We present the effects of structure, chemical binding, and number of layers on stopping for clean, unreconstructed diamond (100) one- to four-layer films with lattice constants fixed at crystalline values, and for graphite mono- and dilayers at their optimized bond lengths. First Born approximation stopping cross sections for protons incident normally on the films were obtained from orbital versions of the kinetic theory of stopping and of the local plasma approximation. The required electron momentum density was generated from the real space Kohn–Sham orbitals. We find a strong static quantum size effect in the stopping of diamond ultra-thin films as opposed to graphite, for which the stopping is only very weakly dependent on the layer number. © 1994 John Wiley & Sons, Inc.

Risk of occupational cancers. Effect of deoxyribonucleic acid adducts

Abstract: Chemical binding to deoxyribonucleic acid (DNA) is thought to be the critical initiation event in cancer formation. These adducts potentially produce deleterious biological effects if not repaired. Many occupational chemical carcinogens are fairly well correlated with their ability to form adducts with DNA. Ideally, DNA should be directly measured in target tissues, generally internal organs for most mutagens/carcinogens. There is considerable interest however in DNA adduct formation in white blood cells. It is conceivable that the major route of chemical intake that leads to white blood cell DNA adducts in exposed workers may not be inhalation. Oral intake and absorption through the skin may play a major role. 32 P-postlabelling is sensitive enough for the analysis of DNA adducts, but cannot be considered as a routine test. It is a promising method for detecting DNA damage resulting from exposure to complex occupational compounds.

Car instrument panel, dashboard or internal sections - formed from moulded layered structure of thermoplastic coating and adhesive on thermo-hardened resin

Abstract: Mfr. of a structure (6) consisting of at least one body (8) partially covered with a coating (7). The coating (7), produced by moulding of a thermoplastic material, and the body (8), formed from a thermohardened resin (9), are sepd. by a layer of adhesive (10) co-operating with at least one of the constituents of the structure (6) to increase the mechanical and/or chemical attachment of the surface of the coating (7) in contact with the body (8). Pref. after moulding of the coating (7), a layer of adhesive (10) is moulded on the surface of the coating using the same procedure. The layered prod. comprising coating plus adhesive is then removed from the mould. One of the faces of the prod. may have a granular surface. Adhesive may be either finely divided mineral or vegetable material which improves mechanical attachment or a thermoplastic material which improves the chemical binding between the coating (7) and body (8). The coating (7) can be made from either PVC or a mixture of PVC and polyurethane, and the adhesive layer formed from polyurethane. USE/ADVANTAGE - Mfr. of dashboard/instrument panels and other moulded interior sections for automobile industry. (claimed). Regular distribution of adhesive agent irrespective of shape of body. Suitable for attachment of coating to foams.

The Chemical Bond

Abstract: We have just found that the equation $$ \Delta E_a^* = \Delta E_a^{*o} - \frac{1}{{{\gamma ^{\text{e}}}}}\Delta \left( {V_{{\text{ne}}}^{e{\text{ff}}} + 2V_{{\text{nn}}}^{e{\text{ff}}}} \right) $$ (3.1) offers a sensible route towards the calculation of chemical binding. It is not the only way, of course, but it has the merit of offering a fresh insight into problems of chemical interest: bonds and bond energies. Bond dissociation energies are even more important, for that matter, because of their role in the interpretation of chemical reactions, but an understanding of bond energies in unperturbed ground-state molecules is required in the first place. Here we put emphasis on the factors governing the energies—and, subsequently, the dissociation—of chemical bonds without suggesting (even remotely) that eq. (3.1) is a panacea for solving all our problems. First of all, we should remember that (3.1) applies only to molecules at equilibrium.

Metallization on polyimide film by Ion and Vapor Deposition (IVD) method

Abstract: We have prepared copper thin films on polyimide films by evaporation of copper metal and simultaneous irradiation of argon ions with energies in the range of 0.5 to 10keV. The argon ion density irradiated at the interface between the copper thin film and the substrate was changed from 5×10 14 to 5×10 16 ions/cm 2 in each ion energy range. The adhesion of copper films was evaluated by means of peel strength. The copper films prepared with 0.5keV argon ions have strong adhesion, but the adhesion of copper films with 5keV and 10keV argon ions was lower than that of copper films prepared without argon ion irradiation. The chemical states of the polyimide film surface and the chemical binding states at the interlayer were evaluated by Fourier transform infrared spectroscopy and X-ray photoelectron spectrometry. The film surface was carbonized by argon ion bombardment, and the carbonization was promoted with the increase of ion energy. The carbonization caused the decrease of the copper film adhesion. The adhesion didn't depend on the chemical binding states at the interlayer. It is consider that the increase of the adhesion was attributed to the anchor effect caused by the diffusion of copper atoms into the substrate by argon ion bombardment.