Decrease In Hydrogen Content Research Articles

Structural properties of a-SiC:H- and a-SiN:H-Alloys from XPS-analyses and IR-absorption

XPS-analyses and IR-absorption in a-Si 1−xC x:H and a-Si 1−xN x:H versus alloy composition for a-SiC:H show a kink in chemical shifts of core levels which indicates an alternating S C network structure and a strong increase in H content. For a-SiN:H the results point towards a statistical distribution of Si and N and a noticeable decrease in hydrogen content.

Impurity doping in chemically vapor-deposited amorphous hydrogenated silicon from disilane

Physical properties of amorphous hydrogenated silicon produced by the chemical vapor deposition (CVD) of disilane have been investigated as a function of doping ratio of phosphine or diborane. The growth rate is decreased by phosphine doping and increased by boron doping. It is found that the electrical conductivity can be controlled over a wide range by phosphorus or boron doping. The optical band gap is lowered by doping as a result of decrease in hydrogen content. Also, a wide band gap of a-SixN1−x:H has been prepared by CVD of a Si2H6+NH3 gas mixture.

Processes controlling metal ion attenuation in acid mine drainage streams

Two acid mine drainage streams have been investigated by detailed analysis of their sediments and waters, to obtain an understanding of the dominant processes which control the transport and attenuation of heavy metals under conditions of chronic high-level pollutant input. One of the water-courses has a thick hydrous iron oxide crust on its bed, where biotically mediated oxidation of ferrous iron resulted in precipitation of amorphous ferric hydroxide, along with substantial quantities of adsorbed silica, sulphate and Al and lesser quantities of As. Small amounts of K and Pb (and possibly hydronium) jarosites were also present in the sediments. Changes in pH and in the concentrations of Cu, Zn, and Cd appear to be mainly the result of dilution by seeps and tributaries. Although no sediment was recovered during collection of water samples from the second stream, saturation index calculations imply that precipitation should have been occurring. The observed down-stream loss of a number of elements supported this conclusion. The solids predicted to be precipitating were A1(OH) 3, Cu 2(OH) 2CO 3, and Fe(OH) 3. Observed decreases in the concentrations of Cd, Zn and Mn can be accounted for on the basis of dilution alone. However, the additional mechanism of neutralization by higher pH inflows is required to account for the decrease in hydrogen ion concentration downstream. The basis for a potentially useful new technique (congruent element analysis) which enables the identification of conservative components in streams is presented. Comparison of logarithmic concentration versus distance plots delineates the point where chemical removal mechanisms become important for each element.

Hydrogen diffusion in LaNi 5H 6 studied by quasi-elastic neutron scattering

We present the results of new high resolution quasi-elastic neutron scattering measurements of the hydrogen diffusion coefficient in LaNi 5H 6 between 280 and 400 K. The crucial importance of multiple-scattering corrections in the evaluation of data at small momentum transfers is demonstrated. The diffusion coefficient follows the equation D = (2.1 ± 0.7) × 10 −3 exp {−(275 ± 15) meV/kT} cm 2 s −1 and decreases with decreasing hydrogen concentration. The anomalous concentration dependence and the existence of composite spectra at large momentum transfers is explained by hydrogen diffusion in the presence of structural traps.

Influence of hydrogen absorption on magnetic ordering in some zirconium-based Laves phase compounds

Magnetization measurements were carried out on several zirconium-based hexagonal Laves phase compounds, i.e. the ZrMn 2 + δ, (Zr,Ti)Mn 2, Zr(Mn,Fe) 2 and Zr(Fe,Al) 2 systems and their hydrides. The absorbed hydrogen leads to a large increase (20%–30%) in volume without a change in the crystal structure. ZrMn 2 + δ is a weak Pauli paramagnet but becomes a spin glass near-ferromagnet by hydriding, indicating that the manganese moments are subjected to competing ferromagnetic and antiferromagnetic coupling tendencies. In the (Zr 1− x Ti x )Mn 2 hydrides, ferromagnetic, spin-glass-like, ferromagnetic and antiferromagnetic behaviors appear at 4.2 K in the sequence of increasing x and/or decrease in hydrogen concentration. In the Zr(Mn,Fe) 2 system, the hydrogen absorption increases both the magnetic moments and the magnetic transition temperatures, while absorbed hydrogen leads to suppression of ferromagnetism in the Zr(Fe,Al) 2 system. These varied and complex magnetic behaviors are attributed to the effects of 1. (1)variations in the interatomic distances, 2. (2) changes in the 3d electron concentration and 3. (3) varying local hydrogen concentrations occurring as a result of statistical fluctuations.

A sensitive and rapid method for determination of pyrophosphatase activity.

A new, rapid and sensitive method of measuring the rate and amount of PPi hydrolysis is described. The method is based on registration of small pH changes, caused by decrease of hydrogen-ion concentration during the pyrophosphatase reaction. With this detected value of hydrogen-ion concentration change and the buffering capacity of each reaction mixture determined by titration, the rate and amount of PPi hydrolysis can be calculated. The results obtained by pH method are in good agreement with values determined by direct phosphate analysis. The described method can be applied to the continuous determination of pyrophosphatase activity in chromatophores, mitochondria, crude extracts or purified enzymes.

Interaction of hydrogen with dislocations in palladium—I. Activity and diffusivity and their phenomenological interpretation

Activity and diffusivity of hydrogen in deformed and annealed palladium has been measured by an electrochemical technique for different degrees of deformation (73, 50, 15, and 6%), at 295 and 322 K and over a wide range of hydrogen concentration from about 1 to 10 4 at.ppm. Deviations from the ideal solution behavior are drastic at the low concentration side where the solubility enhancement is as high as 1.2·10 6 for 73% deformation and 1 at.ppm. From a plot of the free excess enthalpy the ratio of the dislocation densities in samples of different deformation is obtained. The diffusivity decreases with decreasing hydrogen concentration but at very low concentrations of some at.ppm an enhancement of the diffusion is observed. The high concentration results can be calculated from the activity measurements assuming that the activity gradient is the driving force for diffusion, but the increase of diffusivity at low concentrations disagrees with these calculations and is explained by dislocation pipe diffusion. Evidence for this transport mechanism is also given by an unusual diffusion behaviour during current pulse measurements at low concentrations. At 295 K the dislocation pipe diffusivity is about ten times as much as the bulk value in annealed samples.

Adherence of staphylococcus aureus to influenza A virus-infected Madin-Darby canine kidney cell cultures.

Madin-Darby canine kidney cells infected with influenza A virus (strains PR8, FM1, Jap 305, and Tex 1) were tested with nine strains of Staphylococcus aureus and group B Streptococcus type Ic to determine whether mammalian cells become susceptible to bacterial adherence as a result of virus infection. Bacterial adherence to virus-infected cells varied depending on the virus strain and on the strain of bacteria tested. A quantitative radioassay was developed to study the parameters of adherence. Attachment of 3H-labeled S. aureus grown in chemically defined or biologically complex medium to FM1 virus-infected cells was significantly increased (P less than 0.0005) compared with attachment to control cells. Adherence coincided with the appearance of hemadsorption, which is a marker of the presence of virus-induced glycoproteins on the cell surface. Adherence was temperature dependent, increased with a decrease in hydrogen ion concentration, and was not affected by the presence of K+, Mg2+, or Ca2+. Adherence was blocked when 3H-labeled S. aureus was pretreated with trypsin but not when cells were pretreated with neuraminidase.

The Interrelationship between Soot and Fuel NOx Control in Gas Turbine Combustors

The decreased hydrogen content of future fuels will lead to increased formation of soot, while increased organically bound nitrogen in the fuel can result in excessive NOx emission. Control concepts for these two problems are in conflict: prevention of soot requires leaner operation while control of emissions from fuel nitrogen requires fuel-rich operation. However, recent results of two DOE research programs point to both processes having a major dependence on “hydrocarbon breakthrough.” Control of both fuel nitrogen conversion and soot formation can be achieved by primary zone operation at equivalence ratios just below that for hydrocarbon breakthrough. This paper reviews the evidence for the importance of hydrocarbon breakthrough, explains our current understanding of why hydrocarbon breakthrough is important, and offers suggestions of how these results might be applied.

Effect of disorder on the hydrogen content in Si+

Hydrogen concentrations in disordered silicon were measured after exposure to a low-energy hydrogen rf discharge plasma at temperatures between 300 and 425 °C. The saturation hydrogen concentration is found to increase with disorder until amorphization is reached, whereupon the hydrogen content decreases. These results demonstrate that the amorphous structure cannot be considered as a simple extension of a highly defected crystalline structure. We further find that the hydrogen in a-Si exposed to atomic hydrogen in a plasma is bonded only in the monohydride site with an infrared absorption band at ν=1985 cm−1.

Steady-State Kinetics of Trypsin-Catalyzed Hydrolysis of a Synthetic Substrate, Dansyl-D-Arginine Methyl Ester

The trypsin-catalyzed hydrolysis of a synthetic ester substrate, dansyl-D-arginine methyl ester (D-DAME), was followed by the entire progression curve method. This ester substrate, which is a D-enantiomer of arginine, is hydrolyzed to the extent of nearly the pH or the initial substrate concentration. The double-reciprocal plot of the velocity of hydrolysis against the residual substrate concentration showed good linearity. As regards the dependency of this straight line on pH at a constant initial substrate concentration, both the slope and the intercept on the 1/v axis decreased with decrease of hydrogen ion concentration in the pH range below 8 and the lines intersected at a point in the second quadrant. At constant pH the slope of the double-reciprocal plot between the velocity of hydrolysis and the residual substrate concentration increased linearly with increase of the initial substrate concentration. The results obtained cannot be interpreted simply in terms of the three-step mechanism for the trypsin- and chymotrypsin-catalyzed hydrolyses of ester substrates. In particular, it is significant that the catalytic rate constant obtained for the overall enzymatic reaction is very similar to the rate constant of conformational change of the enzyme molecule due to the formation of enzyme-substrate complex in the trypsin-catalyzed hydrolyses of L- and D-DAME.

Growth rate of titanium carbide whiskers in chemical vapor deposition

The growth of titanium carbide crystals from the TiCl 4-CH 4-H 2 system was studied using a flow method. The deposition substrates were graphite plates and mullite tubes heated externally. Only polyhedral microcrystallites were formed on graphite plates. On the mullite substrate tubes, polyhedral microcrystallites were deposited at the temperature lower than 1360°C and whiskers with diameters of 10–300 μm grew above 1360°C. Whiskers were obtained at [CH 4]/[TiCl 4] ⩽ 1 and P TiCl 4 = 7.7– 31.0 Torr. The growth rate of whiskers showed maxima against both titanium tetrachloride and methane concentrations. The growth rate decreased with a decrease in hydrogen concentration. The maximum linear growth rate observed was ∼1.2 × 10 -4 1098 1184 V 3 cm/sec. The titanium carbide whiskers were found to grow preferentially in the [111] direction.

Combustion considerations for future jet fuels

This paper presents recent results which contribute to the combustion technology base necessary for the future development of aircraft jet fuels from non-petroleum resources. Specifically, the effects of fuel hydrogen and nitrogen content have been studied using a T56 combustor rig. Although most of this work has involved fuel blending to simulate alternate fuel properties, data acquired using an actual oil shale jet fuel have been included. Increases of combustor liner temperature with decreased fuel hydrogen content were found to be substantial. A new, non-dimensional temperature parameter is presented which provides an excellent means of correlating results for combustors having rich primary zones designs. Limited data for new, low-smoke lean designs indicate much less sensitivity of combustor liner temperature to fuel hydrogen content. Although smoke emission also increased with decreased hydrogen content, gaseous exhaust emissions were unchanged. Fuel bound nitrogen conversion to NO x under practical aircraft combustion conditions (up to 838°K inlet temperature) was found to be dependent on both fuel nitrogen concentration and combustor inlet temperature. Finally, future directions for alternate jet fuel combustion efforts are summarized. Recommendations range from an expanded scope of combustor and engine testing to required fundamental combustion research.

A comparative study of systems of heavier rare-earth metals with hydrogen [Gd, Tb, Dy, Lu

Hydrogen equilibrium pressures as a function of hydrogen content of the metal and temperature have been measured for gadolinium, terbium, dysprosium, and lutetium, in the primary solid-solution range up to and including the two-phase region with the dihydride phase. All systems show strong similarities, and all are marked by a decrease in heat of solution of hydrogen in the metal with decreasing hydrogen concentration.

The effects of intraparticle diffusion on the yield of the liquid-phase hydrogenation of phenylacetylene in a stirred basket reactor.

The liquid-phase consecutive hydrogenations of phenylacetylene are investigated in the presence of a 0.5% Pt-Al2O3 catalyst. Experiments are performed in a stirred reactor with basket impellers in which the catalyst pellets are held, and a stirred slurry reactor in which the finely powdered pellets are suspended. The intrinsic kinetic equations are derived empirically from the rate measurements with the powdered catalysts. Under the intrinsic kinetic limitation, the intrinsic yield of styrene is independent of both the initial concentration of phenylacetylene and the hydrogen concentration. With the catalyst pellets the hydrogenation rates and the yields are significantly influenced by the intraparticle diffusion. The yield in the regime of the diffusional limitation is reduced below the intrinsic yield, but it is restored up to the level of the intrinsic yield with increasing initial concentration of phenylacetylene and/or decreasing hydrogen concentration. The intraparticle diffusion effects on the hydrogenations are modeled theoretically and solved numerically. By the favorable assessment of the effective diffusivities of the reaction species, the calculated conversion and yield are in good agreement with the experimental results.

Interaction of maleic acid derivatives with gelatin

AbstractThis work deals with the crosslinking efficiency of different maleic acid derivatives (glycol dimaleate, glycerol trimaleate, pentaerithritol tetramaleate, mannitol hexamaleate) and copolymer of vinyl maleate for a better understanding of the mechanism of crosslinking. The reactions were carried out in an aqueous gel state of the biopolymer at 50°C. The kinetics of network formation was followed by measuring the melting point of the gel in contact with water. Such factors, as the decrease of hydrogen ion concentration or the increase of water content of the gel, were found to accelerate the rate of crosslinking. Amines, which were able to block the active sites in a competitive reaction, retarded the process. Synthetic polymers were used to delimit the possibilities of the interactions which might be responsible for the crosslinking. It was assumed that primarily the free amino groups of gelatin are involved in the crosslinking reaction by forming H‐bonds with the maleates.

Gastric absorption of L(+) and D(-) lactic acid and their effects on the transmucosal ion transport in innervated, non-secreting cat stomachs.

AbstractOn instillation of 170 mM lactic acid (L or D) into unstimulated whole stomach pouches in cats the hydrogen ion concentration decreased more slowly than on instillation of 170 mM hydrochloric acid. When 700 mM lactic acid (L or D) was instilled the reverse was found. On instillation of 170 mM HCI subsequent to an instillation of 170 mM lactic acid (L or D) the changes in concentration of eleotrolytes as well as the net fluxes of electrolytes were of the same order of magnitude as during a preceding control instillation of HCI. On instillation of 170 mM HCI subsequent to an instillation of 700 mM lactic acid (L or D) the decrease in hydrogen ion concentration and the increase in sodium ion concentration were significantly larger than in the control instillation of HCI. The net influx of sodium ions was significantly increased but not the net efflux of hydrogen ions. After exposure of the gastric mucosa to 700 mM lactic acid (L or D) it produced a mucoid fluid that contained mainly sodium and chloride ions. This explained the results obtained when HCl was instilled subsequent to an instillation of 700 mM lactic acid. No morphological changes were found on examination in the scanning electron microscope of gastric mucosae exposed to 6 ml of 700 mM L lactic acid.

Investigation of Steel Hydrogenation During Cadmium Electroplating from Cyanide Solutions and Some Questions Connected with Hydrogen Embrittlement Elimination

SummaryDuring cadmium electrodeposition from cyanide electrolytes, intensive hydrogenation not only of the steel substrate but also of the first layers of the cadmium deposit takes place. Hydrogen codeposited with cadmium is in the mobile state and when plated specimens are aged at room temperature (20°C) it diffuses from the deposit into the steel, resulting in an increase of hydrogen concentration in the steel substrate. This effect of the ‘reverse’ hydrogen diffusion from the deposit into the substrate is revealed to an even greater extent when bright cadmium plated specimens are heated. In this case, when the cadmium deposit is thicker than 10 μm the hydrogen concentration in the steel substrate increases 1·5-2 times, a corresponding deterioration of steel ductility being observed. The higher hydrogen permeability of dull cadmium deposits results in a significant decrease of hydrogen concentration in specimens having such coatings after only 2 h of heating at 200°C. The heating of bright plated specim...

Electron Spin Resonance Investigation of the Conducting Dihydrides of Gadolinium and Gadolinium–Yttrium Alloys

Electron spin resonance linewidths and g shifts have been obtained in the temperature range 100–300°K for the gadolinium f electrons in the systems MHx (1.90 < x < 2.46; M ≡ Gd, Gd0.71Y0.29, or Gd0.50Y0.50). The systems behave differently depending on whether x > xcor x < xc; xc = 2.12, 2.07, 1.91 forM ≡ Gd, Gd0.71Y0.29, and Gd0.50Y0.50, respectively. For x > xc the g shifts (relative to g for Gd in insulators) were ≈ + 0.01, independent of x and of temperature. These shifts are interpreted as the result of the exchange interaction − JS·s between the gadolinium f electrons and the s conduction electrons, indicating that hydrogen enters the lattice as H−. The g values are slightly temperature dependent for x <x c. The linewidth is proportional to the temperature, characteristic of the Korringa formula, above x = xc. Below x = xc the linewidth becomes temperature independent and increases with decreasing hydrogen content. This temperature independent broadening is linked with vacant tetrahedral interstices, normally occupied by hydrogens in the face-centered cubic metal lattice.

Effect of various activators on the salivary amylase of the bug Lygus disponsi

The effect of various activators on the salivary amylase of Lygus disponsi was investigated. The salivary amylase was strongly activated by glutamine and moderately by asparagine, aspartic acid, and glutamic acid. The activating effect of glutamine at pH 7·0 began to appear at about 10 −4 M of glutamine concentration, reaching a maximum at about 10 −1 M. The activating effect of KNO 3 at pH 7·0 began to develop at about 10 −5 M of KNO 3, reaching a maximum in the range 10 −3 ∼10 −1 M, and then decreased sharply. The activating effect of KNO 3, as well as NaCl, increased linearly with the decrease in hydrogen-ion concentration and was even appreciable at pH 4·5-5·0, which was the optimum pH for the action of salivary amylase. In the presence of KNO 3 or NaCl activity of the salivary amylase was extended over a wide pH range and the optimum pH was shifted from pH 4·5 to 5·0 to about pH 6·0. The activating effect of the mixture (NaCl+KNO 3) was not in general given by the simple sum of the activating effect of each component. When one of the components was of such a concentration that, if used alone, it would exhibit maximum attainable activation, the effect due to the other component was completely masked, whereas when the concentration of each component was such that it produced an activating effect less than the maximum, both components in the mixture played the rôle of activators. Only when their individual activating powers were sufficiently small did their sum coincide with the observed value for the mixture. The salivary amylase was strongly to moderately activated by various plant extracts and the gut extract. The activating effect of the flower bud extract of rape at pH 7·0 appeared at an extract concentration of 10 −3 to 10 −4, reaching a maximum at about 7·5 × 10 −2. It may be possible that NO 3− and Cl − increase the rate of starch digestion in the gut and are useful for stabilizing the function of the amylase against the change of pH in the gut, and consequently play a part in extending the host range of L. disponsi.