Effect Of Chemical Environment Research Articles

Human Fibroblast and Human Bone Marrow Cell Response to Lithographically Nanopatterned Adhesive Domains on Protein Rejecting Substrates

The separate influence of topographical and chemical cues on cell attachment and spreading are well documented; however, that of duel-cue substrates is less so. In this study graft copolymers that sterically stabilize biological surfaces were employed alongside nanotopographical features fabricated by colloidal lithography. This resulted in the production of a range of substrates whereby the effect of chemistry and or topography on both on human fibroblast and bone marrow cell adhesion and spreading could be observed. The current studies indicate an enhancement of cell response as a consequence of modifications in material topography, whereas the current selected chemical cues inhibited cell function. Critically, in combination, topography modulated the effects of chemical environment.

構造体コンクリートの破壊挙動モニタリングによる損傷度評価

The durability of concrete structures decreases easily due to such physical or chemical environmental effects as freezing-thawing process, chemical attack, fatigue or carbonation. The degree of damage in concrete is, in most cases, evaluated by a compression test and a rebound hammer test. For effective maintenance of concrete structures, it is necessary to evaluate not only the strength of concrete but also the damage degree. Quantitative damage evaluation system of concrete is proposed by applying acoustic emission (AE) method and damage mechanics. The procedure is named DeCAT, which is an abbreviation of “Damage Estimation of Concrete by Acoustic Emission Technique”. In this study, the relative damage evaluation of concrete by DeCAT in core tests. Core-samples were collected from a reinforced concrete water channel that had been used for 23 to 73 years. Mechanical properties of compressive strengths and Young's moduli were measured during the compression test, and dynamic Young's moduli were calculated from a longitudinal wave velocity. By estimating the concrete damage, it can be quantitatively evaluated from AE generating behavior under compression test and Calm ratio under cyclic loading test.

Effect of chemical environment on high-pressure Raman response of single-walled carbon nanotubes

The pressure-induced Raman peak shifts for single-walled carbon nanotubes (SWNTs) have been studied using different solvents as hydrostatic pressure-transmitting fluids (PTF). We suggest that the variation in the nanotube response to hydrostatic pressure with different PTF is evidence that the common solvents used are able to penetrate the interstitial spaces in the nanotube bundle. With hexane, we find the surprising result that the individual nanotubes appear unaffected by hydrostatic pressures (i.e. a flat Raman response) up to 0.7 GPa. Qualitatively similar results have been obtained with butanol. Following the approach of Amer et al. [M. S. Amer, M. S. El-Ashry and J. F. Maguire, J. Chem. Phys. 121 2752 (2004)], we speculate that this is due to the inability of SWNTs to adsorb some solvents onto their surface at low pressure.

P67 高温下における貴金属の再結晶に対する化学雰囲気の効果(序報)(ポスターセッション,日本火山学会2006年秋季大会)

P67 高温下における貴金属の再結晶に対する化学雰囲気の効果(序報)(ポスターセッション,日本火山学会2006年秋季大会)

High pressure Raman spectroscopy of single-walled carbon nanotubes: Effect of chemical environment on individual nanotubes and the nanotube bundle

Abstract The pressure-induced tangential mode Raman peak shifts for single-walled carbon nanotubes (SWNTs) have been studied using a variety of different solvents as hydrostatic pressure-transmitting media. The variation in the nanotube response to hydrostatic pressure with different pressure transmitting media is evidence that the common solvents used are able to penetrate the interstitial spaces in the nanotube bundle. With hexane, we find the surprising result that the individual nanotubes appear unaffected by hydrostatic pressures (i.e. a flat Raman response) up to 0.7 GPa. Qualitatively similar results have been obtained with butanol. Following the approach of Amer et al. [J. Chem. Phys. 121 (2004) 2752], we speculate that this is due to the inability of SWNTs to adsorb some solvents onto their surface at lower pressures. We also find that the role of cohesive energy density in the solvent–nanotube interaction is more complex than previously thought.

(98) Molecular Analysis of Abscission Layer Activation in Apple Fruit Pedicels

Abscission of leaves, floral organs, and fruit is a developmentally and environmentally regulated process initiated in specialized thin layers of cells within abscission zones (AZs). Very little is known about early molecular events that drive abscission, especially of fruit. Commercial apple production relies on the use of flower and fruit abscission-promoting and -inhibiting compounds to enhance fruit quality, control preharvest fruit drop, and maintain consistent annual bearing. The success of chemical treatments is strongly influenced by numerous factors, including environment, genotype, developmental stage of the fruit, and physiological state of the tree. Toward developing improved strategies for regulating fruit abscission, we carried out transcriptional profiling of competent-quiescent and activated abscission layers. We found that a decisive event in the sequential process of abscission layer development is the transcriptional activation of the MdPEL1 gene, encoding a plant pectate lyase protein and potentially involved in the degradation of the middle lamella of adjacent abscission layer cells. Additionally, regulatory elements of at least 12 homologous pectate lyase genes in Arabidopsis thaliana were found to direct expression in floral AZs and in dehiscence zones along valve margins, suggesting that these genes have evolutionary conserved function. This work identifies a novel role for pectate lyases in plants. Furthermore, many abscission-related genes identified in this study are being used to track biochemical and regulatory pathways that participate in abscission in response to chemical treatments or environmental effects.

Plaque biofilms: The effect of chemical environment on natural human plaque biofilm architecture

The architecture of microbial biofilms especially the outer regions have an important influence on the interaction between biofilm and local environment particularly on the flux of materials into and out of biofilm compartments and as a consequence, biofilm metabolic behaviour. In the case of dental plaque biofilms, architecture will determine access of nutrients including acidogenic substrates and therapeutic materials to the microbial biomass and to the underlying tooth surface. Manipulation of this architecture may offer a means of altering mass transfer into the whole biofilm and biomass and raises the possibility of improving access of therapeutics. Plaque biofilms formed in vivo on human enamel were subjected to a number of different chemical conditions while under observation by confocal laser scanning microscopy in reflection mode. In this way the outer 50-100 microm or so of the biofilms was examined. Density and distribution of biomass were recorded as degree of reflectance. The amount and density of biofilm biomass increased from the plaque saliva interface towards the interior. Plaque biofilms were robust and little affected by mechanical manipulation, high ionic strength or low pH (2.5). Detergent (SLS), however, often appeared to either remove biomass and/or dramatically reduce its density.

Substitution and chemical environment effects on the absorption spectrum of indigo

The UV/visible spectra of a series of indigo derivatives have been evaluated by using ab initio methods. The combination of the Polarizable continuum model for estimating bulk solvent effects with the TD-B3LYP6-311 + G(2d,p)B3LYP6-311G(d,p) level of approximation, leads to an accurate description of the wavelength of maximum absorption of indigoids compounds. Using this procedure, we have assessed the effects of both the surroundings (solvent and solid state) and the substitution pattern. For the latter, we obtained a mean absolute deviation of only 7 nm (0.02 eV) compared to experiment, for a set of 86 molecules/solvents.

The Effect of Compound Composition and Strain on Vacancies in Si/SiGe Heterostructures

In this paper we study the effect of chemical environment and elastic strains, which can arise in layered heterostructures due to the lattice parameter mismatch, on the vacancy formation energy in random Si-Ge compounds. Ab initio calculations demonstrate a number of simple trends characterizing the vacancy formation energy dependence on vacancy charge, the number of Ge atoms in its neighbourhood and on the magnitude of elastic strains. The obtained parameters of vacancy-germanium interaction indicate, in particular, a tendency for preferential vacancy accumulation in SiGe region of Si/SiGe/Si layered structures, which is confirmed here by Monte- Carlo simulation of high-temperature vacancy annealing and agrees well with recent experimental observations.

Grain-growth kinetics in wadsleyite: Effects of chemical environment

Grain-growth kinetics in wadsleyite was investigated using a multianvil high-pressure apparatus. Fine-grained wadsleyite aggregates were synthesized by isostatic hot-pressing and were subsequently annealed under high pressure and temperature in a controlled chemical environment. Wadsleyite samples show normal grain-growth characterized by a log-normal grain-size distribution following the relation, L n − L 0 n = k t where n is a constant, L the grain-size at time t, L 0 the grain-size at time t = 0 and k is a rate constant that depends on temperature T and chemical environments ( f O 2 : oxygen fugacity in Pa, C OH: water content in H/10 6Si) as: k = A ′ D f O 2 r D exp − H D ′ * R T + A ′ W f O 2 r W C OH q exp − H W ′ * R T with A ′ D = 10 − 4.9 ± 6.1 ( − 8.0 ± 7.4 ) ( m n s − 1 P a − r D ) , r D = 0.12 ± 0.11(0.20 ± 0.14), H D ′ * = 410 ± 230(500 ± 270) kJ/mol, A ′ W = 10 − 18.2 ± 1.4 ( − 24.0 ± 1.7 ) ( m n s − 1 P a − r W ) , r W = 0.14 ± 0.05(0.22 ± 0.06), q = 1.7 ± 0.3(2.2 ± 0.3) and H W ′ * = 120 ± 60(160 ± 70) kJ/mol with assumed value of n = 2(3) (values in parentheses denote parameters for n = 3). Both water and oxygen fugacities significantly enhance grain-growth kinetics. The large value of the parameter describing the water fugacity dependence, q ∼ 1.5–2.5, cannot be explained solely by a simple model in which grain-growth is controlled by diffusion of atoms (defects) across the grain-boundaries The interaction of grain-boundaries with charged defects or the density of hydrated ledges may be important factors that control the grain-growth kinetics of wadsleyite. When compared at similar thermo-chemical conditions, grain-growth of wadsleyite is found to be more sluggish than grain-growth of olivine. The present results show that a small wadsleyite grain-size (<1 mm) in subducting slabs can be maintained for a significant geological time (∼1 My) under “dry” (<200 H/10 6Si) conditions when the temperature is lower than 1500 K, whereas when a large amount of water (>100,000 H/10 6Si) is present, a small grain-size (<1 mm) can only be maintained for a significant time at low temperatures (<600 K).

Swift heavy ion (150 MeV:Ag13 +) induced structural changes in a-C:H films studied by Raman spectroscopy

A study of the structural changes in amorphous hydrogenated carbon (a-C:H) films induced by swift heavy ion irradiation and laser irradiation is performed. The effect of irradiation on the a-C:H films is found to be dependent on the initial microstructure of the films, i.e., the type of bonding of the carbon atoms and the distribution of hydrogen in the carbon matrix as understood from Raman spectroscopy. The attempt has been made to create a consistent picture of the effect of cluster type, cluster size, network configuration and chemical environment (hydrogen concentration) on Raman spectra. Various possible mechanisms are discussed leading to the changes due to laser and swift heavy ion irradiation, such as change in cluster size, type and C and H erosion, etc., investigated by Raman spectroscopy.

Surfactants and interfacial phenomena

Surfactants and interfacial phenomena

The effects of chemical environment on the nucleation, growth, and stability of ettringite [Ca 3Al(OH) 6] 2(SO 4) 3·26H 2O

Ettringite is responsible for both the initial set of Portland cement and for premature concrete deterioration. A new method of ettringite crystal growth by combining calcium hydroxide and aluminum sulfate solutions was devised to reliably produce crystals that could be seen with a light microscope (45×–320×). The nucleation, growth, morphology, and stability of ettringite in the presence of over 300 chemicals and admixtures, many of which are present in the concrete environment, was then investigated. The plasticizers sorbitol, citrate, and tartrate were found to inhibit ettringite nucleation and growth, as did certain lignosulfonate air-entraining admixtures. The Type B set retarder borax inhibited ettringite formation at <44 ppm. The consequences and implications of this are discussed.

Effects of chemical environment on diffusivities within thin Nafion ® films as monitored from chronoamperometric responses of generator–collector double microband assemblies

The possibility of monitoring in situ the modifications of a polymeric thin film in relation to its chemical environment by means of measurement of diffusive properties and assessment of the volume available to diffusion is investigated. These measurements are performed electrochemically through the monitoring of the currents at paired-microband electrodes operated in a generator–collector mode. The experimental results reported here were primarily focused to assess the validity of the principle. This involved the evaluation of the effects of the chemical environment of the polymer on the diffusional cross-talk of Fe III redox species incorporated into a Nafion ® micrometric film coating the electrode assembly. Modification of the chemical environment was performed by adding different amounts of organic compound such as methanol, ethanol, ethyleneglycol, propanol and dimethylformamide (DMF) (from 0 to 20% v/v) into the 0.1 mol l −1 H 2SO 4 electrolyte in which the assembly is placed. An procedure that could be automated based on a theoretical diffusional model developed previously was used to analyze the generator–collector chronoamperometric responses. This allowed the determination of the concentration c o and the diffusion coefficients of Fe III and Fe II species within Nafion ® films as well as the film thickness h. This showed a concentration dependence of the Fe III diffusion coefficient suggesting that the rate of physical diffusion of iron centers governs mainly the charge transport within Nafion ® thin films under the conditions investigated. The presence of an organic compound in the surrounding electrolyte caused a decrease of the steady-state generator–collector current, the effect being the most significant for DMF. The magnitude of this decrease was observed to depend on the nature and the concentration of the organic compound added to the electrolyte. Detailed chronoamperometric analyses established that the current decrease was related principally to the decrease in diffusion coefficient and to a moderate change of the amount of iron species available to diffusional transport, without significant change of the film thickness. This suggested that the presence of organic compound modified the plasticization of the polymer matrix.

Study of changes in L32 EELS ionization edges upon formation of Ni-based intermetallic compounds.

EELS L32 ionization edges in several Ni-based intermetallic compounds have been studied and interpreted in terms of the distribution of electrons in the valence d-bands. It is demonstrated that the integral EELS cross-sections change only slightly upon the formation of intermetallic compounds and therefore the charge transfer between atoms is negligible. On the other hand, the changes in the fine energy-loss near-edge structure (ELNES) of the Ni L3 edge can be readily detected indicating an important redistribution of d-electrons at the Ni site with alloying. These features are well reproduced by ab-initio calculations with a FLAPW method in its WIEN97 implementation. In contrast to the drastic effect of chemical environment, structural transformations in the investigated intermetallics result in smaller ELNES changes, which can be detected by only exceptional instruments with a higher energy resolution.

Chemical Environment Effects on the Photophysical Behavior of Two-Photon Materials

AbstractA set of six new two-photon engineered diethylamino-substituted styryl pyrazine (DEASP) dyes have been developed as chemically responsive chromophores. This work employs UV/Vis spectroscopy to draw structure-optical property relationships and to quantify the solvatochromic effect observed for these dyes. Absorbance profiles for each of these dyes have been measured in 22 solvents ranging from very nonpolar (TMS) to very polar (water). Absorbance maxima of the longest wavelength π→π transitions have been correlated to nine empirical scales of solvent polarity, and a comparative analysis is presented. Dimroth &amp; Reichardt's and Kamlet &amp; Taft's single parameter scales have been recalculated with spectral data obtained for the six DEASP dyes. The correlation of these established and recalculated scales are shown and discussed. DEASP chromophores are found to exhibit high sensitivity to their chemical environment and exceptional range as solvatochromic probes. Current models of solvatochromism, based on dipolar probes, cannot account for the solvatochromism observed in our quadrupolar dyes, and fail to describe the effect of the chemical environment on this family of twophoton dyes. The need to develop a more universal model of solvation incorporating higher order moment contributions is apparent.

The Synthesis and Catalytic Application of a New Class of Imprinted Silica

AbstractThe effect of chemical environment surrounding a synthetic heterogeneous catalyst active site is investigated using the hydrophilic imprinting of silica. Two model reaction systems have been used for this study: (i) Knoevenagel condensation of 3-nitrobenzaldehyde and malononitrile and (ii) Suzuki coupling of bromobenzene and phenylboronic acid. Using a catalyst in which isolated imprinted amines are surrounded by an acidic silanol-rich environment led to rate accelerations of over 120-fold relative to catalysts in which the amines are surrounded by a hydrophobic environment consisting of trimethylsilyl functional groups for system (i). This result parallels our previous study on the effect of the outer sphere composition on rate acceleration of Knoevenagel reactions using isophthalaldehyde as the aldehyde reactant. We also extended our method for the hydrophilic imprinting of bulk silica to organometallic systems, by successfully synthesizing a tethered palladium complex within the imprinted pocket. This material was used as an active catalyst for (ii). Our results show that a hydrophobic framework environment results in higher initial turnover frequencies than an acidic silanol-rich framework for the Suzuki coupling reaction of bromobenzene and phenylboronic acid, albeit with a lower overall effect than observed in the Knoevenagel system (i). Altogether, these results demonstrate the control of chemical reactivity via the rational design of the outer sphere using an imprinting approach.

Electron transfer in ion interactions with chlorine covered silver surfaces

The effect of chemical environment on the neutralisation of ions with adsorbate covered surfaces was investigated on the example of H + and rare gas ion scattering on chlorine covered Ag. Changes in coverage from the submonolayer chemisorption to chloride nucleation stage, strongly affect electron transfer. In the case of H +, Ne + and Ar + these changes induce an “unusual” non-linear, oscillating, coverage dependence of electron transfer probabilities, due to modifications in the surface electronic structure. In case of the more highly bound He, we assign the observed changes to modifications in quasi-resonant charge transfer rates involving the Cl 3s core level, because of the core level shifts induced by changes in chemical environment.

Effect of silica fume, metakaolin, and low-calcium fly ash on chemical resistance of concrete

Effects of aggressive chemical environments were evaluated on the mortars prepared with ordinary portland cement (OPC) and silica fume (SF)/metakaolin (MK)/low-calcium fly ash at various replacement levels. The natural adverse chemical environmental conditions were simulated using sulfuric acid, hydrochloric acid, nitric acid, acetic acid, phosphoric acid, and a mixture of sodium and magnesium sulfates. Chemical resistance information was used in conjunction with compressive strength measurements to propose realistic OPC/mineral admixture proportions.

Effects of Chemical Environments on Pultruded E-Glass Reinforced Polyesters

In this work, the chemical resistance of six kinds of pultruded E-glass fiber reinforced isophthalic polyesters are studied. They contain 50 w% or 60 w% glass. The composites were either unfilled or filled with calcium carbonate or kaolin clay. The mechanical, physical, optical, and structural properties of the pultruded flat profiles before and after immersion in seawater, demineralized water, sodium hydroxide (5%), and sulfuric acid (10%) were analyzed over the period of one year.