The influence of chemical environment on the infrared spectra of embedded molecules in astrophysical ices

2017 ◽  
Vol 13 (S332) ◽  
pp. 346-352 ◽  
Author(s):  
Victor S. Bonfim ◽  
Sergio Pilling
Keyword(s):  
Dielectric Constant ◽  
Cross Section ◽  
Continuum Model ◽  
Solid Phase ◽  
Chemical Environment ◽  
Effect Of Temperature ◽  
Individual Species ◽  
Polarized Continuum Model ◽  
Different Types ◽  
Astrophysical Ices

AbstractIn this work, one intends to computationally simulate and investigate, via thermochemical calculations, how the chemical environment influences some molecular properties, such as IR spectra and absorption cross section, of individual species embedded in the solid phase employing the Polarized Continuum Model (PCM) approach. The trial molecules used here to check these effects are CO, CO2 and H2O. The solid phase (bulk ice) is simulated using different dielectric constant values representing different types of astrophysical ice at PCM approach. The effect of temperature is also investigated since it is known it affects the dielectric constant of the solvent medium.

Models of the equilibrium distribution of organic chemicals between water and solid phases of environmental media

2014 ◽  
Vol 22 (4) ◽  
pp. 430-444 ◽  
Author(s):  
Eva M. Webster
Keyword(s):  
Organic Phase ◽  
Solid Phase ◽  
Ion Pairs ◽  
Chemical Environment ◽  
Individual Species ◽  
Linear Free Energy Relationship ◽  
Organic Chemicals ◽  
Equilibrium Models ◽  
Adsorption Models

Water–solid phase equilibrium distributions are foundational to multimedia environmental fate models of anthropogenic organic chemicals. This contextual review of equilibrium models of ionizing organics in aqueous–solids systems highlights the broad range of modeling assumptions and paradigms that have been employed. The complexity of soils and sediment, especially the organic phase, is provided as background along with a description of equilibrium models for nonpolar, nonionizing organics. The ways in which these single-species models have been modified and adapted for application to ionizing organics is detailed. The individual species proposed as contributing to observed distributions include the neutral parent, ions, and ion pairs. The debate over the role of the organic phase in soil and sediment solids is presented. Both absorption and surface adsorption models are described. Organic carbon (OC)-dependent models range from the simple Karickhoff equation to complex molecular connectivity indices models and polyparameter linear free energy relationship (pp-LFER) models. Adsorption models are derived from inorganic interaction chemistry. They include the early Langmuir model and Freundlich equation and continue to the modern Model VI and the NICA-Donnan model. Adsorption models focus on the mineral phase, but the role of the organic phase is not entirely dismissed. Dual mode models seek to combine absorption to OC with adsorption interactions. Conclusions drawn from studies of acid behavior do not predict the sorption of bases; bases are described separately. No single explanation and accompanying model of the distribution behavior of ionizing organics has emerged as the clear choice for regulatory use. The complexity of chemical–environment interactions is such that models are either challenging to parameterize and understand or they fail to capture key aspect(s) of the system critical to understanding of one or more classes of chemical or environmental medium. Future research directions are suggested including the possible benefit of removing sorbate–sorbent or chemical–environment distinctions.

Acetylene chemisorption at palladium: Effect of temperature and structure of the surface

1984 ◽  
Vol 49 (6) ◽  
pp. 1448-1458
Author(s):  
Josef Kopešťanský
Keyword(s):  
Work Function ◽  
Atomic Hydrogen ◽  
Effect Of Temperature ◽  
Thermally Stable ◽  
Template Effect ◽  
Temperature Range ◽  
Adsorbed Layers ◽  
Different Types ◽  
Adsorption Complexes ◽  
Low Coverage

The effect of temperature and structure of the palladium surfaces on acetylene chemisorption was studied along with the interaction of the adsorbed layers with molecular and atomic hydrogen. The work function changes were measured and combined with the volumetric measurements and analysis of the products. At temperature below 100 °C, acetylene is adsorbed almost without dissociation and forms at least two different types of thermally stable adsorption complexes. Acetylene adsorbed at 200 °C is partly decomposed, especially in the low coverage region. Besides the above mentioned effects, the template effect of adsorbed acetylene was studied in the temperature range from -80° to 25 °C. It has been shown that this effect is a typical phenomenon of the palladium-acetylene system which is not due to surface impurities.

The study of neutron capture processes in AlN nanoparticles

2021 ◽  
pp. 2150127
Author(s):  
T. G. Naghiyev
Keyword(s):  
Computer Modeling ◽  
Cross Section ◽  
Neutron Capture ◽  
Absorption Cross Section ◽  
Effective Cross Section ◽  
Absorption Cross ◽  
Effective Absorption ◽  
Different Types ◽  
N Isotopes

The neutron capture processes in the AlN nanoparticles were investigated by computer modeling. Neutrons absorption were separately investigated for aluminum (Al) and nitrogen (N) atoms in the AlN nanoparticles. The modeling was performed separately for each stable Al and N isotopes, because the effective absorption cross-section of different types of isotopes of Al and N atoms is different. Moreover, effective cross-section spectra of neutron capture for aluminum and nitrogen atoms were comparatively investigated.

The Hertzian Spectrum of Rubber and Its Micellar Constitution

1946 ◽  
Vol 19 (4) ◽  
pp. 1085-1087
Author(s):  
Pierre Girard ◽  
Paul Abadie
Keyword(s):  
Dielectric Constant ◽  
Electric Field ◽  
Wave Length ◽  
Structural Features ◽  
Loss Angle ◽  
First Case ◽  
Dipolar Molecules ◽  
Alternating Electric Field ◽  
Different Types ◽  
Absorption And Dispersion

Abstract The spectra which were studied lie within the region of hertzian frequencies, and can be represented either by dispersion curves showing the dielectric constant of the substance as a function of the frequency (or wave length λ), or by absorption curves showing the loss angle as a function of this frequency. These two types of curves represent the same phenomenon, i.e., orientation of the dipolar molecules in the alternating electric field, in accordance with the theory of Debye. The spectra and their interpretation depend chiefly on whether the molecules are crystalloid with relatively small and similar dimensions, or are colloidal, with large and unequal dimensions. In the first case, the spectra gives evidence chiefly on the form of the molecules and their structural features. Dilution in a nonpolar solvent shows for certain dipolar compounds, e.g., alcohol, considerable deformations, which differ according to the solvent. In the case of colloids, e.g., rubber, which has a permanent moment, the spectra and the meaning of these spectra are far different. In this case the spectra indicate that the absorption and dispersion values in the hertzian region are closely related to the micellar constitution, i.e., to the different types of micelles, to their size, and to the proportion of each type.

scholarly journals Characteristic-Aroma-Component-Based Evaluation and Classification of Strawberry Varieties by Aroma Type

Molecules ◽  
2021 ◽  
Vol 26 (20) ◽  
pp. 6219
Author(s):  
Lixia Sheng ◽  
Yinan Ni ◽  
Jianwen Wang ◽  
Yue Chen ◽  
Hongsheng Gao
Keyword(s):  
Solid Phase ◽  
Economic Value ◽  
Gas Chromatography Mass Spectrometry ◽  
Volatile Components ◽  
Solid Phase Micro Extraction ◽  
Ripe Fruit ◽  
Volatile Organic ◽  
Different Types ◽  
Aroma Components

The unique fruity aroma of strawberries, a popular fruit of high economic value, is closely related to all the volatile organic compounds (VOCs) contained within them. Despite extensive studies on the identification of VOCs in strawberries, systematic studies on fruit-aroma-related VOCs are few, resulting in a lack of effective standards for accurately distinguishing aroma types. In the present study, solid-phase micro extraction and gas chromatography–mass spectrometry were used to analyze and identify VOCs in the ripe fruit of each of the 16 strawberry varieties at home and abroad and to explore their characteristic aroma components and the classification of such varieties by aroma type. The results suggested remarkable variations in the types and contents of VOCs in different strawberry varieties, of which esters were dominant. The principal volatile components, consisting of four esters, three alcohols, one aldehyde, and one ketone, in 16 strawberry varieties were detected based on the absolute and relative contents of VOCs in the fruit. The characteristic aroma components in strawberries, containing nine esters, six aldehydes, and one alcohol, were determined based on the aroma values of different VOCs, and the characteristic aroma components were divided into five types further based on aroma descriptions. Sixteen strawberry varieties were finally divided into four aroma types, namely, peachy, pineapple, fruity, and floral, based on the contributions of different types. The results provided a basis and standard for classifying strawberries by aroma type, studying the hereditary regularity of the fruity aroma of strawberries, and improving aroma quality.

scholarly journals Improving Solvation Energy Predictions Using The SMD Solvation Method and Semiempirical Electronic Structure Methods

2018 ◽  
Author(s):  
Jimmy C. Kromann ◽  
Casper Steinmann ◽  
Jan Halborg Jensen
Keyword(s):  
Continuum Model ◽  
Solvation Energy ◽  
Solvation Model ◽  
Polar Solvents ◽  
Data Set ◽  
Solvation Energies ◽  
Polarized Continuum Model ◽  
Electronic Structure Methods ◽  
Aqueous Solvation ◽  
Model C

The PM6 implementation in the GAMESS program is extended to elements requiring d-integrals and interfaced with the conducter-like polarized continuum model (C-PCM) of solvation, in- cluding gradients. The accuracy of aqueous solvation energies computed using AM1, PM3, PM6, and DFTB and the SMD continuum solvation model is tested using the MNSOL data set. The errors in SMD solvation energies predicted using NDDO-based methods is considerably larger than when using DFT and HF, with RMSE values of 3.4-5.9 (neutrals) and 6-15 kcal/mol (ions) compared to 2.4 and ca 5 kcal/mol for HF/6-31G(d). For the NDDO-based methods the errors are especially large for cations and considerably higher than the corresponding COSMO results, which suggests that the NDDO/SMD results can be improved by re-parameterizing the SMD parameters focusing on ions. We found the best results are obtained by changing only the radii for hydrogen, carbon, oxygen, nitrogen, and sulfur and this leads to RMSE values for PM3 (neutrals: 2.8/ions: ca 5 kcal/mol), PM6 (4.7/ca 5 kcal/mol), and DFTB (3.9/ca 5 kcal/mol) that are more comparable to HF/6-31G(d) (2.4/ca 5 kcal/mol). Though the radii are optimized to reproduce aqueous solvation energies, they also lead more accurate predictions for other polar solvents such as DMSO, acetonitrile, and methanol, while the improvements for non-polar solvents are negligible.

Time-Resolved Reflectivity Study of Solid-Phase Epitaxial Regrowth in Relaxed and Strained Si1−xGex Epilayers

1992 ◽  
Vol 281 ◽  
Author(s):  
T. E. Haynes ◽  
C. Lee ◽  
K. S. Jones
Keyword(s):  
Composition Dependence ◽  
Solid Phase ◽  
Strain Relaxation ◽  
Alloy Layer ◽  
Atomic Fraction ◽  
Bulk Alloy ◽  
Strained Layers ◽  
Time Resolved ◽  
Epitaxial Regrowth ◽  
Different Types

ABSTRACTThe rate of solid-phase epitaxial regrowth has been studied using time-resolved reflectivity in three different types of SiGe/Si epilayers amorphized by ion implantation. In two of these cases, the alloy epilayer contained either 12% or 20% Ge, and the amorphization depth was greater than the thickness (2000 Å) of the SiGe alloy layer. Time-resolved reflectivity measurements showed that the rate of regrowth was not constant in these two cases, but first decreased after passing the SiGe/Si interface, and then increased. The minimum regrowth rate occurred closer to the SiGe/Si interface in the epilayers with the larger Ge atomic fraction. In the third type of sample, the alloy epilayer thickness was ∼7μm, so that the initial epilayer (15% Ge) had the lattice constant of the bulk alloy. Furthermore, amorphization and regrowth occurred entirely within the relaxed alloy layer. In this case, the regrowth rate was constant. The composition dependence of the regrowth-rate transient in the strained layers is discussed in the context of a ‘critical-thickness’ model of strain relaxation.

3. Sedimentary rocks

2016 ◽  
pp. 29-50
Author(s):  
Jan Zalasiewicz
Keyword(s):  
Sedimentary Rock ◽  
Chemical Weathering ◽  
Sedimentary Rocks ◽  
Chemical Environment ◽  
Combined Effects ◽  
Star System ◽  
The Earth ◽  
Different Types ◽  
Physical And Chemical

The Earth has the greatest abundance and variety of sedimentary strata in our star system, dating back some 3.8 billion years. ‘Sedimentary rocks’ describes the processes that create different types of sedimentary rocks, which form a key guideline in reconstructing Earth’s history. Particles are created by both physical and chemical weathering. These particles are then moved by different modes of transport and sorted by size, which affect the resulting sedimentary rock. Sedimentary layers can remain as soft muds or loose sands for millions of years, but most buried sedimentary layers harden and turn into rock, under the combined effects of increasing heat and pressure, and of changes in chemical environment.

scholarly journals Bhabha scattering in very special relativity at finite temperature

2020 ◽  
Vol 80 (8) ◽  
Author(s):  
Alesandro Ferreira dos Santos ◽  
Faqir C. Khanna
Keyword(s):  
Differential Cross Section ◽  
Special Relativity ◽  
Cross Section ◽  
Differential Cross ◽  
Local Form ◽  
Bhabha Scattering ◽  
Thermo Field Dynamics ◽  
Different Types ◽  
Non Local ◽  
Very Special Relativity

Abstract In this paper the differential cross section for Bhabha scattering in the very special relativity (VSR) framework is calculated. The main characteristic of the VSR is to modify the gauge invariance. This leads to different types of interactions appearing in a non-local form. In addition, using the Thermo Field Dynamics formalism, thermal corrections for the differential cross section of Bhabha scattering in VSR framework are obtained.

scholarly journals Prevalence of Gastrointestinal Helminth Infections in Indigenous Chickens of Selected Areas of Barisal District, Bangladesh

2014 ◽  
Vol 12 (2) ◽  
pp. 135-139 ◽  
Author(s):  
MN Alam ◽  
M Mostofa ◽  
MAHNA Khan ◽  
MA Alim ◽  
AKMA Rahman ◽  
...  
Keyword(s):  
Cross Section ◽  
Helminth Parasites ◽  
Ascaridia Galli ◽  
Routine Examination ◽  
Pathological Lesions ◽  
Heterakis Gallinarum ◽  
Indigenous Chickens ◽  
Gastrointestinal Helminth ◽  
Helminth Infections ◽  
Different Types

The prevalence of gastrointestinal helminth infections and the gross pathological lesions produced by them were studied from February 2012 to January 2013 in the Department of Pharmacology of Bangladesh Agricultural University, Mymensingh. In this study, a total of 320 indigenous chickens aged ranging from 2 to 4 months were examined to identify the different types of gastrointestinal helminth infections in indigenous chickens. During routine examination, six species of helminth parasites were recorded, of which five species of nematodes such as Ascaridia galli, Heterakis gallinarum, Capillaria spp, Acuaria hamulosa and Dispharynx spiralis; and one species was cestode called Raillietina tetragona. The highest prevalence was observed for Ascaridia galli (41.56%) followed in descending order by Raillietina tetragona (19.68%), Heterakis gallinarum (15.62%), Acuaria hamulosa (8.75%), Capillaria spp. (4.68% ) and Disopharinx spiralis (1.56%). The gross pathological lesions were observed in case of Acuaria hamulosa and Heterakis gallinarum infection. In case of Acuaria hamulosa infection keratinization of gizzard mucosa and cross section of adult Acuaria hamulosa were seen along with marked infiltration of neutrophils. The results of this study suggest that both nematodes and cestodes are highly prevalent in indigenous chickens in the studied area.DOI: http://dx.doi.org/10.3329/bjvm.v12i2.21275 Bangl. J. Vet. Med. (2014). 12 (2): 135-139 

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