The Diffusion of Phosphorus in Silicon from High Surface Concentrations

1984 ◽  
Vol 36 ◽  
Author(s):  
H. F. Schaake
Keyword(s):  
Experimental Data ◽  
Point Defect ◽  
Enhancement Factor ◽  
High Surface ◽  
Intrinsic Diffusion ◽  
High Concentration ◽  
Surface Enhancement ◽  
Charged Species ◽  
Phosphorus In Silicon ◽  
Positively Charged

ABSTRACTAn interstitial model is developed to quantitatively account for the anomalous effects which accompany the diffusion of phosphorus in silicon from high surface concentrations. Phosphorus is assumed to diffuse as both a positively charged (intrinsic diffusion) and an uncharged interstitial (high concentration case). Silicon is assumed to diffuse as both an uncharged (instrinsic) and a negatively charged interstitial (high phosphorus concentrations). The effect of internal fields on charged species is included. An excellent fit is found with published experimental data if a surface enhancement factor, analogous to that for the case of oxidation enhancement, is used. Flat-top diffusion is modelled by assuming the formation of a dislocation array, which alters the point defect equilibria.

A Steady-State Model for Coupled Defect Impurity Diffusion in Silicon

1989 ◽  
Vol 163 ◽  
Author(s):  
F. F. Morehead ◽  
R. F. Lever
Keyword(s):  
Steady State ◽  
High Surface ◽  
Local Equilibrium ◽  
Surface Concentration ◽  
Extended Model ◽  
High Concentration ◽  
Steady State Model ◽  
High Surface Concentration ◽  
Phosphorus In Silicon ◽  
Diffusion Profiles

AbstractWe extend our earlier model which was proposed to explain tails in the diffusion profiles of high concentration boron and phosphorus in silicon. Our quasi-steady-state approach is generalized here to include both vacancies (V) and interstitials (I) at equivalent levels. I-V recombination is regarded as near local equilibrium, occurring through reactions of the defects with defect-impurity pairs. This approach leads to the well-known plateau, kink and tail in high surface concentration P diffusions in Si and to the less well recognized tails in B as well. Our extended model, in its simplest form, allows a more complete and less restrictive treatment of Au diffusion in Si. An important advantage is the direct inclusion of these defect-impurity interactions and the resulting gradients in the defect concentrations.

Influence of nascent polypeptide positive charges on translation dynamics

2020 ◽  
Vol 477 (15) ◽  
pp. 2921-2934
Author(s):  
Rodrigo D. Requião ◽  
Géssica C. Barros ◽  
Tatiana Domitrovic ◽  
Fernando L. Palhano
Keyword(s):  
Mrna Decay ◽  
Translation Termination ◽  
Published Data ◽  
Translation Efficiency ◽  
Amino Acid Residues ◽  
High Concentration ◽  
Strong Argument ◽  
Translation Arrest ◽  
Exit Tunnel ◽  
Positively Charged

Protein segments with a high concentration of positively charged amino acid residues are often used in reporter constructs designed to activate ribosomal mRNA/protein decay pathways, such as those involving nonstop mRNA decay (NSD), no-go mRNA decay (NGD) and the ribosome quality control (RQC) complex. It has been proposed that the electrostatic interaction of the positively charged nascent peptide with the negatively charged ribosomal exit tunnel leads to translation arrest. When stalled long enough, the translation process is terminated with the degradation of the transcript and an incomplete protein. Although early experiments made a strong argument for this mechanism, other features associated with positively charged reporters, such as codon bias and mRNA and protein structure, have emerged as potent inducers of ribosome stalling. We carefully reviewed the published data on the protein and mRNA expression of artificial constructs with diverse compositions as assessed in different organisms. We concluded that, although polybasic sequences generally lead to lower translation efficiency, it appears that an aggravating factor, such as a nonoptimal codon composition, is necessary to cause translation termination events.

Tenacious Mass Transfer Limitations Drive Catalytic Selectivity during Electrochemical Carbon Dioxide Reduction

2019 ◽  
Author(s):  
Kailun Yang ◽  
Recep Kas ◽  
Wilson A. Smith
Keyword(s):  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Catalyst Layer ◽  
Active Surface ◽  
Active Surface Area ◽  
High Concentration ◽  
Copper Electrodes ◽  
Surface Enhanced ◽  
Local Current

<p>This study evaluated the performance of the commonly used strong buffer electrolytes, i.e. phosphate buffers, during CO<sub>2</sub> electroreduction in neutral pH conditions by using in-situ surface enhanced infrared absorption spectroscopy (SEIRAS). Unfortunately, the buffers break down a lot faster than anticipated which has serious implications on many studies in the literature such as selectivity and kinetic analysis of the electrocatalysts. Increasing electrolyte concentration, surprisingly, did not extend the potential window of the phosphate buffers due to dramatic increase in hydrogen evolution reaction. Even high concentration phosphate buffers (1 M) break down within the potentials (-1 V vs RHE) where hydrocarbons are formed on copper electrodes. We have extended the discussion to high surface area electrodes by evaluating electrodes composed of copper nanowires. We would like highlight that it is not possible to cope with high local current densities on these high surface area electrodes by using high buffer capacity solutions and the CO<sub>2</sub> electrocatalysts are needed to be evaluated by casting thin nanoparticle films onto inert substrates as commonly employed in fuel cell reactions and up to now scarcely employed in CO<sub>2</sub> electroreduction. In addition, we underscore that normalization of the electrocatalytic activity to the electrochemical active surface area is not the ultimate solution due to concentration gradient along the catalyst layer.This will “underestimate” the activity of high surface electrocatalyst and the degree of underestimation will depend on the thickness, porosity and morphology of the catalyst layer. </p> <p> </p>

Application of biological activated carbon anaerobic reactor for treatment of hazardous chemicals

2006 ◽  
Vol 53 (11) ◽  
pp. 251-260 ◽  
Author(s):  
H. Tsuno ◽  
M. Kawamura ◽  
T. Oya
Keyword(s):  
Experimental Data ◽  
Activated Carbon ◽  
Organic Compounds ◽  
Adsorptive Capacity ◽  
Biological Degradation ◽  
Hazardous Chemicals ◽  
High Concentration ◽  
Expanded Bed ◽  
Biological Activated Carbon ◽  
Anaerobic Reactor

An expanded-bed anaerobic reactor with granular activated carbon (GAC) medium has been developed to treat wastewaters that contain a high concentration of inhibitory and/or refractory organic compounds as well as readily degradable organic compounds. The process is characterised by a combination of two removal mechanisms; adsorption on GAC and biological degradation by microorganisms grown on GAC. Applicability of the reactor to treatment of phenol, chloroacetaldehyde (CAA), pentachlorophenol (PCP) and tetrachloroethylene (PCE) was discussed based on experimental data. All chemicals focused on here were removed well and stably at a removal efficiency of more than 98% even during starting operation and shock load operation. Chemicals in influent that exceeded biological degradation capacity was initially adsorbed on GAC and then gradually degraded, and hence the adsorptive capacity of GAC was regenerated biologically. These results proved that a biological activated carbon anaerobic reactor was effective for treatment of wastewater containing hazardous chemicals, especially for strongly absorbable chemicals, as well as readily degradable organic compounds at high concentration.

scholarly journals Experimental Data and Modelling of the Solubility of High-Carotenoid Paprika Extract in Supercritical Carbon Dioxide

Molecules ◽  
2019 ◽  
Vol 24 (22) ◽  
pp. 4174 ◽  
Author(s):  
Dorota Kostrzewa ◽  
Agnieszka Dobrzyńska-Inger ◽  
August Turczyn
Keyword(s):  
Experimental Data ◽  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Static Method ◽  
Coefficient Of Determination ◽  
High Concentration ◽  
Relative Deviation ◽  
Measurement Results ◽  
Supercritical Carbon

The studies of solubility of the paprika extract with a high concentration of carotenoids in carbon dioxide under the pressure of 20–50 MPa and at temperatures of 313.15–333.15 K were carried out using the static method. The highest solubility of paprika extract was achieved at the temperature of 333.15 K and under the pressure of 50 MPa. The obtained experimental data were correlated with five density-based models, applied for prediction of solubility in the supercritical carbon dioxide (the Chrastil, del Valle and Aguilera, Adachi and Lu, Sparks et al. and Bian et al. models). The accuracy of particular models with reference to measurement results was specified with the average absolute relative deviation (AARD) and coefficient of determination (R2). Results showed that solubility calculated based on the selected models was compliant with experimental data.

ATOMISTIC SIMULATION OF DISSIPATIVE CHARGE CARRIER DYNAMICS FOR PHOTOCATALYSIS

2012 ◽  
Vol 1390 ◽  
Author(s):  
Talgat M. Inerbaev ◽  
Dmitri S. Kilin ◽  
James Hoefelmeyer
Keyword(s):  
Charge Transfer ◽  
High Surface ◽  
High Surface Area ◽  
Oxidation Catalysis ◽  
Electron Hole ◽  
Charge Carrier Dynamics ◽  
Electron Hole Pair ◽  
Charge Transfer Dynamics ◽  
Reduced Density ◽  
Positively Charged

ABSTRACTPhoto-excitation of high surface area semiconductor nanorods decorated with surface catalyst particles are investigated. DFT-based simulation is applied to the charge transfer dynamics at the interface of the supported nanocatalyst by modeling dynamics of photo-excitations. The modeling is performed by reduced density matrix method in the basis of Kohn-Sham orbitals. The energy of photo-excitation is dissipating due to interaction with lattice vibrations, treated through non-adiabatic coupling as the electron/hole pair relaxes to the conduction / valence band edges. The methodology is applied to TiO2 nanorod modeled as a periodic anatase (100) slab functionalized by minimalistic nano-clusters or doping. Simulations of these models demonstrate the formation of charge transfer state in both time and frequency domain. Computed charge dynamics leads to creation of positively charged areas on the nanorod surface that is an important prerequisite for oxidation catalysis. Our computation identifies optimal composition and morphology of nanocatalyst for such applications as water splitting for hydrogen production or solar cells.

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