The mechanism of the production of atomic hydrogen by hot tungsten

1936 ◽  
Vol 32 (4) ◽  
pp. 653-656 ◽  
Author(s):  
J. K. Roberts ◽  
G. Bryce
Keyword(s):  
Temperature Variation ◽  
Atomic Hydrogen ◽  
Hydrogen Molecule ◽  
Hydrogen Pressure ◽  
The Other ◽  
Square Root ◽  
Important Process ◽  
Experimental Conditions ◽  
Tungsten Atom ◽  
Tungsten Surface

The fact that the rate of production of atomic hydrogen at a tungsten surface at a given temperature is proportional to the square root of the hydrogen pressure means either that the important process is the evaporation of atoms from an adsorbed film which over the whole range of experimental conditions is sparsely occupied, or that the production of atoms is in the main due to a process in which a hydrogen molecule strikes a bare tungsten atom in the surface, one atom being adsorbed and the other evaporating and the surface being almost completely covered over the whole range of experimental conditions. Either process leads to a temperature variation in the rate of atom production in agreement with experiment. A definite decision between the two processes cannot yet be made.

A study of the properties of hydrogen films on tungsten by the method of contact potentials

1937 ◽  
Vol 33 (3) ◽  
pp. 394-402 ◽  
Author(s):  
R. C. L. Bosworth
Keyword(s):  
Dipole Moment ◽  
Hydrogen Atom ◽  
Gas Phase ◽  
Atomic Hydrogen ◽  
The Other ◽  
Condensation Coefficient ◽  
Effective Dipole Moment ◽  
Tungsten Atom ◽  
Contact Potential ◽  
Hydrogen Molecules

In a study of the properties of hydrogen on tungsten by the method of contact potentials the following points have been established:(1) The contact potential of a 92% covered surface of hydrogen on tungsten against bare tungsten is 1·04 V., and the Richardson constants for such a surface are, approximately,A = 30, b = 5·60 V.(2) A film of deuterium is 20 m V. positive relative to a similar hydrogen film.(3) Over the range of temperatures and pressures used by Bryce in a study of the production of atomic hydrogen the films are nearly saturated, so that the production of atomic hydrogen is primarily due to a molecule striking a bare tungsten atom, one atom being adsorbed and the other going into the gas phase.(4)The condensation coefficient for hydrogen molecules on cold tungsten is 0·01.(5) The effective dipole moment of each hydrogen atom on the surface is −0·42 Debye unit and is independent of the fraction of the surface covered.

scholarly journals Theory of the elastic scattering of electrons in molecular hydrogen

1930 ◽  
Vol 129 (811) ◽  
pp. 616-627 ◽  
Keyword(s):  
Elastic Scattering ◽  
Cross Sections ◽  
Atomic Hydrogen ◽  
Molecular Hydrogen ◽  
Hydrogen Molecule ◽  
Incident Beam ◽  
Quantum Mechanical ◽  
Experimental Conditions ◽  
Actual Case ◽  
Mechanical Methods

Since tbe introduction of quantum mechanical methods, the theory of scattering of electrons by atoms and ions has been developed very considerably. In the case of elastic collisions it is possible to determine the effective cross sections presented by atoms to a beam of electrons, from a knowledge of the potential in the atom. This has been done for helium by Mott and the calculated cross sections agree well with the experimental. Unfortunately, the simplest theoretical case, that of the elastic scattering of electrons by atomic hydrogen, the theory of which has been given by Elsasser, is extremely difficult to attain experimentally, 50 to 60 per cent, atomic hydrogen being the maximum at present attainable. It thus would seem of interest to consider what effects would be expected by using molecular instead of atomic hydrogem This case is also novel in that we are considering an axially symmetrical field and the number of electrons scattered through a given angle depends on the orientation of the axis relative to the initial and final beams. In an actual case the axes of the molecules may be taken as in random directions, the hydrogen molecule having no permanent dipole moment and so being only slightly oriented by the electric field of the incident beam. This permits us to average the scattering over all orientation to obtain experimental conditions.

scholarly journals 2-step reaction kinetics for hydrogen absorption into bulk material via dissociative adsorption on the surface

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Taro Yakabe ◽  
Gaku Imamura ◽  
Genki Yoshikawa ◽  
Naoya Miyauchi ◽  
Masahiro Kitajima ◽  
...  
Keyword(s):  
Reaction Kinetics ◽  
Dynamic Process ◽  
Hydrogen Absorption ◽  
Hydrogen Pressure ◽  
Absorption Rate ◽  
Bulk Material ◽  
Dissociative Adsorption ◽  
The Other ◽  
Hyperbolic Function ◽  
Square Root

AbstractWe have demonstrated that the process of hydrogen absorption into a solid experimentally follows a Langmuir-type (hyperbolic) function instead of Sieverts law. This can be explained by independent two theories. One is the well-known solubility theory which is the basis of Sieverts law. It explains that the amount of hydrogen absorption can be expressed as a Langmuir-type (hyperbolic) function of the square root of the hydrogen pressure. We have succeeded in drawing the same conclusion from the other theory. It is a 2-step reaction kinetics (2sRK) model that expresses absorption into the bulk via adsorption on the surface. The 2sRK model has an advantage to the solubility theory: Since it can describe the dynamic process, it can be used to discuss both the amount of hydrogen absorption and the absorption rate. Some phenomena with absorption via adsorption can be understood in a unified manner by the 2sRK model.

scholarly journals H2 Transformations on Graphene Supported Palladium Cluster: DFT-MD Simulations and NEB Calculations

Catalysts ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1306
Author(s):  
Francesco Ferrante ◽  
Antonio Prestianni ◽  
Marco Bertini ◽  
Dario Duca
Keyword(s):  
Atomic Hydrogen ◽  
Density Functional ◽  
Hydrogen Molecule ◽  
Md Simulations ◽  
Vacant Site ◽  
Functional Theory ◽  
H2 Adsorption ◽  
Palladium Cluster ◽  
Supported Palladium ◽  
Dynamics Simulations

Molecular dynamics simulations based on density functional theory were employed to investigate the fate of a hydrogen molecule shot with different kinetic energy toward a hydrogenated palladium cluster anchored on the vacant site of a defective graphene sheet. Hits resulting in H2 adsorption occur until the cluster is fully saturated. The influence of H content over Pd with respect to atomic hydrogen spillover onto graphene was investigated. Calculated energy barriers of ca. 1.6 eV for H-spillover suggest that the investigated Pd/graphene system is a good candidate for hydrogen storage.

scholarly journals Mechanism of Stochastic Resonance in a Quorum Sensing Network Regulated by Small RNAs

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Ya-nan Zhu ◽  
Jianwei Shen ◽  
Yong Xu
Keyword(s):  
Quorum Sensing ◽  
Stochastic Resonance ◽  
Small Rna ◽  
Small Rnas ◽  
Cell Communication ◽  
The Other ◽  
Important Process ◽  
Positive Role ◽  
Bacterial Quorum Sensing ◽  
Bacterial Quorum

Bacterial quorum sensing (QS) is an important process of cell communication and more and more attention is paid to it. Moreover, the noises are ubiquitous in nature and often play positive role. In this paper, we investigate how the noise enhances the QS though the stochastic resonance (SR) and explain the mechanism of SR in this quorum sensing network. In addition, we also discuss the interaction between the small RNA and the other genes in this network and discover the biological importance.

Intercalation Processes in Cobalt Substituted Nickel Oxyhydroxides

1990 ◽  
Vol 210 ◽  
Author(s):  
Claude Delmas
Keyword(s):  
Ir Spectroscopy ◽  
Mechanical Treatment ◽  
Positive Charge ◽  
Van Der Waals ◽  
The Other ◽  
Hydrolysis Reaction ◽  
Water Molecules ◽  
Layered Oxides ◽  
Experimental Conditions ◽  
Cobalt Ions

AbstractChimie douce reactions (hydrolysis and reduction) from layered oxides : NaNiO2, NaxCoO2 and NaNil-xCoxO2 lead to numerous oxyhydroxides and hydroxides which differ by the composition of the intersheet space.According to the experimental conditions of the hydrolysis reaction, the oxyhydroxides can be unhydrated or intercalated with one or two layers of water molecules. From the most hydrated phases, the other ones can be obtained by chemical, thermal and even mechanical treatment.The reduction of Co-substituted nickel oxyhydroxides leads to hydroxides in which nickel and cobalt ions are respectively divalent and trivalent. In order to compensate the excess of positive charge in the (Ni, Co)O2 sheet, anions (OH-, CO32-, SO42-, NO3-) are inserted in the Van der Waals gap.For the highest anion amounts, well ordered α*-type materials are obtained. Water molecules are simultaneously inserted in the interslab space. Their structure is strongly related to the hydrotalcite one. When the amouit of anions in the intersheet space is not sufficient, interstratified materials are obtained. In this case the (Ni,Co)(OH)2 slabs are separated by a layer of CO32- anions and water molecules (α*-type) or by an empty Van der Waals gap (β(II)-type). The amount of α*-type planes in the structure increases with the cobalt amount. All these materials have been characterized by IR spectroscopy which allows to detect the existence of two types of O-H bonds (free in α*-type plane or hydrogen bonded in ²(II)-type plane).

In Vitro Binding of Zearalenone to Different Adsorbents

2005 ◽  
Vol 68 (3) ◽  
pp. 613-615 ◽  
Author(s):  
DANTE J. BUENO ◽  
LILIANA DI MARCO ◽  
GUILLERMO OLIVER ◽  
ALICIA BARDÓN
Keyword(s):  
Activated Carbon ◽  
Calcium Sulfate ◽  
Fusarium Species ◽  
The Other ◽  
Experimental Conditions ◽  
In Vitro Binding ◽  
Other Hand ◽  
Vitro Binding ◽  
Dose Levels

Zearalenone (ZEA) is a potent estrogenic metabolite produced by some Fusarium species. No treatment has been successfully employed to get rid of the ZEA contained in foods. This study was conducted to evaluate the ability (adsorptive power) of five adsorbents—activated carbon, bentonite, talc, sandstone, and calcium sulfate—to trap ZEA in vitro. Activated carbon was the best adsorbent, binding 100% ZEA (pH 3 and 7.3) at 0.1, 0.25, 0.5, and 1% dose levels. Bentonite, talc, and calcium sulfate were less efficient than activated carbon but still could bind ZEA to some extent. On the other hand, sandstone was inactive in the experimental conditions employed. Our results indicate that activated carbon could be a good candidate for detoxification of ZEA present in foods.

scholarly journals Infestation of froghopper nymphs changes the amounts of total phenolics in sugarcane

2005 ◽  
Vol 62 (6) ◽  
pp. 543-546 ◽  
Author(s):  
Rafael José Navas da Silva ◽  
Eduardo Rossini Guimarães ◽  
José Francisco Garcia ◽  
Paulo Sérgio Machado Botelho ◽  
Maria Inês Tiraboschi Ferro ◽  
...  
Keyword(s):  
Phenolic Compounds ◽  
Low Temperature ◽  
Temperature Variation ◽  
Total Phenolics ◽  
The Other ◽  
Plant Phenolics ◽  
High Moisture ◽  
Randomized Design ◽  
Leaf Tissues ◽  
Completely Randomized Design

The increased rate of sugarcane harvest without previous burn has provided a very favorable environment to the froghopper Mahanarva fimbriolata (Stal, 1854), with high moisture and low temperature variation. Few works have studied the response of sugarcane to this pest, so little is known about resistant cultivars. Plant phenolics are widely studied compounds because of their known antiherbivore effect. This research aims to determine if the attack of M. fimbriolata nymphs stimulates the accumulation of total phenolics in sugarcane. The experiment was carried out in greenhouse and arranged in completely randomized design, in a 3 X 2 X 4 factorial with three replications. Second instar nymphs of M. fimbriolata were infested at the following rates: control, 2-4 and 4-8 nymphs per pot (first-second infestations, respectively). Pots were covered with nylon net and monitored daily to isolate the effect of leaf sucking adults. Leaf and root samples were collected and kept frozen in liquid nitrogen until analyses. Infested plants showed higher levels of phenolics in both root and leaf tissues. In roots, the cultivar SP80-1816 accumulated more phenolic compounds in response to the infestation of M. fimbriolata. On the other hand, higher levels were found in leaves and roots of control plants of SP86-42, which might be an indication of a non-preference mechanism. The increase of total phenolics in sugarcane infested with root-sucking froghopper nymphs does not seem to be useful to detect the resistance to this pest.

The Effects of Adverse Environmental Conditions on Workload

1975 ◽  
Vol 19 (3) ◽  
pp. 301-304
Author(s):  
Ann E. Martin
Keyword(s):  
Environmental Conditions ◽  
Environmental Variables ◽  
Secondary Task ◽  
The Other ◽  
Random Numbers ◽  
Performance Decrement ◽  
Experimental Conditions ◽  
Continuous Noise ◽  
Adverse Environmental Conditions ◽  
Intermittent Noise

The present study was conducted to investigate the effects of environmental conditions on visual workload. The environmental variables used were temperature, studied at levels of 45°F., WBGT, and 95°F., WBGT; and noise, studied at 83 dBA intermittent noise and 93 dBA continuous noise. Workload was defined as the amount of attention demanded from an operator as measured by performance decrement on a secondary task while performing a primary and secondary task simultaneously. The secondary task was reading random numbers, and the primary task was reading word lists. Significant differences (p<.05) were found between the control condition and all experimental conditions. The low temperature and high temperature-continuous noise conditions were significantly different from the other conditions. Noise and temperature were found to significantly increase workload (p<05).

scholarly journals Cultivation of Milky Mushroom (Calocybeindica) in Greenhouse

2021 ◽  
pp. 63-69
Author(s):  
P. Indraja ◽  
M. Madhava ◽  
S. Satyam ◽  
P. R. Chandra ◽  
S. Joy Prince
Keyword(s):  
Relative Humidity ◽  
Traditional Method ◽  
Large Scale ◽  
Nutritive Value ◽  
Edible Mushroom ◽  
Atmospheric Temperature ◽  
The Other ◽  
Controlled Environment ◽  
Mushroom Cultivation ◽  
Experimental Conditions

Mushroom cultivation is one of the most important steps in diversification of agriculture. Milky mushroom (Calocybeindica) is a tropical edible mushroom, popular because of its good nutritive value and it can be cultivated commercially on large scale. Generally, by creating controlled environment in rooms mushroom cultivation is taken up, In traditional method  it is typical to manage the atmospheric temperature and humidity in desired range, which can be maintained easily in greenhouse by automatic control system.Cultivation of milky mushroom in greenhouse was taken up in controlled environment under three different conditions of controlled temperature and relative humidity (RH). The experimental conditions are 28°C and 79% RH, 24°C and 84% RH and 32°C and 72%RH. The yield obtained was found maximum at 24°C temperature and 84% relative humidity when compared with the other two greenhouse environment conditions. The yield from the mushroom cultivation under controlled environmental conditions in greenhouse was found to be high when compared with the conventional practice. It was concluded that, the mushroom cultivation yields high under controlled greenhouse conditions and also economical compared to the conventional method.

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