A novel framework for studying the impact of binding energy distributions on the chemistry of dust grains

The evaporation of molecules from dust grains is crucial to understanding some key aspects of the star- and the planet-formation processes. During the heating phase, the presence of young protostellar objects induces molecules to evaporate from the dust surface into the gas phase, enhancing its chemical complexity. Similarly, in circumstellar discs, the position of the so-called snow lines is determined by evaporation, with important consequences for the formation of planets. The amount of molecules that are desorbed depends on the interaction between the species and the grain surface, which is controlled by the binding energy. Recent theoretical and experimental works point towards a distribution of values for this parameter instead of the single value often employed in astrochemical models.We present a new “multi-binding energy” framework to assess the effects that a distribution of binding energies has on the amount of species bound to the grains. We find that the efficiency of the surface chemistry is significantly influenced by this process, with crucial consequences on the theoretical estimates of the desorbed species.

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Statistical study of uncertainties in the diffusion rate of species on interstellar ice and its impact on chemical model predictions

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833804 ◽

2018 ◽

Vol 620 ◽

pp. A109 ◽

Cited By ~ 4

Author(s):

Wasim Iqbal ◽

Valentine Wakelam ◽

Pierre Gratier

Keyword(s):

Binding Energy ◽

Gas Phase ◽

Pearson Correlation ◽

Correlation Coefficients ◽

Surface Species ◽

Adsorbed Species ◽

Key Species ◽

Almost All ◽

The Impact ◽

Dust Surface

Contact. Diffusion of species on the dust surface is a key process for determining the chemical composition of interstellar ices. On the dust surface, adsorbed species diffuse from one potential well to another and react with other adsorbed reactants, resulting in the formation of simple and complex molecules. Aims. We study the impact on the abundances of the species simulated by the chemical codes by considering the uncertainties in the diffusion energy of adsorbed species. We aim to limit the uncertainties in the abundances as calculated by chemical codes by identifying the surface species that result in a larger error because of the uncertainties in their diffusion energy. Methods. We ran various cases with 2000–10 000 simulations in each case and varied the diffusion energies of some or all surface species randomly. We calculated Pearson correlation coefficients between the abundances and the ratio of diffusion to binding energy of adsorbed species. We identified the species that introduce maximum uncertainty in the ice and gas-phase abundances. With these species we ran three sets, with 2000 simulations in each, to quantify the uncertainties they introduce. Results. We present the abundances of various molecules in the gas phase and also on the dust surface at different time intervals during the simulation. We show which species produce a large uncertainty in the abundances. We sorted species into different groups in accordance with their importance in propagating uncertainty in the chemical network. Conclusions. We show that CO, H2, O, N, and CH3 are the key species for uncertainties in the abundances, while CH2, HCO, S and O2 come next, followed by NO, HS, and CH. We also show that by limiting the uncertainties in the ratio of diffusion to binding energy of these species, we can eliminate the uncertainties in the gas-phase abundances of almost all the species.

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Chemical Kinetics Simulations of Ice Chemistry on Porous Versus Non-Porous Dust Grains

Frontiers in Astronomy and Space Sciences ◽

10.3389/fspas.2021.643297 ◽

2021 ◽

Vol 8 ◽

Author(s):

Drew A. Christianson ◽

Robin T. Garrod

Keyword(s):

Chemical Kinetics ◽

Interstellar Dust ◽

Three Dimensional ◽

Binding Energies ◽

Inert Gases ◽

Chemical Effect ◽

Dust Grains ◽

Interstellar Clouds ◽

Dust Grain ◽

Grain Surface

The degree of porosity in interstellar dust-grain material is poorly defined, although recent work has suggested that the grains could be highly porous. Aside from influencing the optical properties of the dust, porosity has the potential to affect the chemistry occurring on dust-grain surfaces, via increased surface area, enhanced local binding energies, and the possibility of trapping of molecules within the pores as ice mantles build up on the grains. Through computational kinetics simulations, we investigate how interstellar grain-surface chemistry and ice composition are affected by the porosity of the underlying dust-grain material. Using a simple routine, idealized three-dimensional dust-grains are constructed, atom by atom, with varying degrees of porosity. Diffusive chemistry is then simulated on these surfaces using the off-lattice microscopic Monte Carlo chemical kinetics model, MIMICK, assuming physical conditions appropriate to dark interstellar clouds. On the porous grain surface, the build-up of ice mantles, mostly composed of water, leads to the covering over of the pores, leaving empty pockets. Once the pores are completely covered, the chemical and structural behavior is similar to non-porous grains of the same size. The most prominent chemical effect of the presence of grain porosity is the trapping of molecular hydrogen, formed on the grain surfaces, within the ices and voids inside the grain pores. Trapping of H2 in this way may indicate that other volatiles, such as inert gases not included in these models, could be trapped within dust-grain porous structures when ices begin to form.

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Effect of Binding Energies on the Encounter Desorption

Frontiers in Astronomy and Space Sciences ◽

10.3389/fspas.2021.671622 ◽

2021 ◽

Vol 8 ◽

Author(s):

Ankan Das ◽

Milan Sil ◽

Rana Ghosh ◽

Prasanta Gorai ◽

Soutan Adak ◽

...

Keyword(s):

Adsorption Energy ◽

Quantum Chemical ◽

Binding Energies ◽

Chemical Calculation ◽

Surface Species ◽

Water Ice ◽

Chemical Complexity ◽

Hydrogen Molecules ◽

Simple Molecules ◽

Grain Surface

The abundance of interstellar ice constituents is usually expressed with respect to the water ice because, in denser regions, a significant portion of the interstellar grain surface would be covered by water ice. The binding energy (BE) or adsorption energy of the interstellar species regulates the chemical complexity of the interstellar grain mantle. Due to the high abundance of water ice, the BE of surface species with the water is usually provided and widely used in astrochemical modeling. However, the hydrogen molecules would cover some part of the grain mantle in the denser and colder part of the interstellar medium. Even at around ∼10 K, few atoms and simple molecules with lower adsorption energies can migrate through the surface. The BE of the surface species with H2 substrate would be very different from that of a water substrate. However, adequate information regarding these differences is lacking. Here, we employ the quantum chemical calculation to provide the BE of 95 interstellar species with H2 substrate. These are representative of the BEs of species to a H2 overlayer on a grain surface. On average, we notice that the BE with the H2 monomer substrate is almost ten times lower than the BE of these species reported earlier with the H2O c-tetramer configuration. The encounter desorption of H and H2 was introduced [with ED(H,H2)=45 K and ED(H2,H2)=23 K] to have a realistic estimation of the abundances of the surface species in the colder and denser region. Our quantum chemical calculations yield higher adsorption energy of H2 than that of H [ED(H,H2) = 23–25 K and ED(H2,H2) = 67–79 K]. We further implement an astrochemical model to study the effect of encounter desorption with the present realistic estimation. The encounter desorption of the N atom [calculations yield ED(N,H2)=83 K] is introduced to study the differences with its inclusion.

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Particularities of the independent auditor's report on reliability of accounting (financial) statements for 2019: COVID-19 as qualitatively essential information (Part 2)

International Accounting ◽

10.24891/ia.23.7.777 ◽

2020 ◽

Vol 23 (7) ◽

pp. 777-799

Author(s):

O.I. Shvyreva ◽

Z.I. Kruglyak ◽

A.V. Petukh

Keyword(s):

Financial Reporting ◽

Financial Statements ◽

Economic Situation ◽

Risk Disclosure ◽

Essential Information ◽

Logical Method ◽

Annual Reporting ◽

The Face ◽

Key Aspects ◽

The Impact

Subject. This article discusses the issues related to the practice of financial reporting in the face of uncertainties caused by the coronavirus contagion, as well as the specifics of the audit strategy and formation of an audit opinion on this reporting. Objectives. The article aims to identify the quality characteristics of financial reporting prepared in the context of the COVID-19 pandemic and justify the key aspects of assurance engagement completion in an extremely uncertain epidemiological and economic situation. Methods. For the study, we used an abstract-logical method, content analysis techniques, systematization, and classification. Results. Analyzing the impact of the extremely uncertain epidemiological and economic situation on financial statements, the article clarifies aspects of disclosure of events after the reporting date and threats to business continuity in the annual reporting of economic entities. The article identifies possible alternative procedures and algorithms to obtain proper evidence when it is insufficient in the face of the inability to meet certain audit standards requirements in a remote audit environment. The article defines the impact of COVID-19 risk disclosure on the structure of the audit report and opinion. Relevance. The results of the study can be used in the practical activities of economic entities that prepare financial statements in the face of significant uncertainty, as well as auditors and audit organizations.

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Problems with the Interpretation of the “Slovak Reformation”

Journal of Early Modern Christianity ◽

10.1515/jemc-2020-2026 ◽

2020 ◽

Vol 7 (2) ◽

pp. 305-318

Author(s):

Eva Kowalská

Keyword(s):

Ethnic Identity ◽

Language Policies ◽

Structural Problems ◽

Vernacular Language ◽

Cultural Implications ◽

The Reformation ◽

Reformation Movement ◽

Key Aspects ◽

The Impact

AbstractStructural problems of communities affected by the “Slovak Reformation,” issues with accepting the situation or simply the relationships among various cultural phenomena, like literacy or language policies, are key aspects in studying the impact of the Reformation in Hungary, especially with respect to Slovaks. Information gathered from the Reformation had a direct and long-lasting impact on the formation of vernacular language, as well as on the search for and the construction of an ethnic identity. Searching for evidence left by the Slovak presence in the Reformation movement thus presents challenging though notable problems for Slovak historiography. The confessional division and its political as well as cultural implications have evoked long-lasting discussions among historians as well as politicians. This study focuses on the most relevant issues within these processes.

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Reproduction in Trypanosomatids: Past and Present

Biology ◽

10.3390/biology10060471 ◽

2021 ◽

Vol 10 (6) ◽

pp. 471

Author(s):

Camino Gutiérrez-Corbo ◽

Bárbara Domínguez-Asenjo ◽

María Martínez-Valladares ◽

Yolanda Pérez-Pertejo ◽

Carlos García-Estrada ◽

...

Keyword(s):

Low Income ◽

Phenotypic Diversity ◽

Natural Populations ◽

Genetic Exchange ◽

Health Concern ◽

Current Debate ◽

Naturally Occurring ◽

Experimental Works ◽

Genomic Recombination ◽

The Impact

Diseases caused by trypanosomatids (Sleeping sickness, Chagas disease, and leishmaniasis) are a serious public health concern in low-income endemic countries. These diseases are produced by single-celled parasites with a diploid genome (although aneuploidy is frequent) organized in pairs of non-condensable chromosomes. To explain the way they reproduce through the analysis of natural populations, the theory of strict clonal propagation of these microorganisms was taken as a rule at the beginning of the studies, since it partially justified their genomic stability. However, numerous experimental works provide evidence of sexual reproduction, thus explaining certain naturally occurring events that link the number of meiosis per mitosis and the frequency of mating. Recent techniques have demonstrated genetic exchange between individuals of the same species under laboratory conditions, as well as the expression of meiosis specific genes. The current debate focuses on the frequency of genomic recombination events and its impact on the natural parasite population structure. This paper reviews the results and techniques used to demonstrate the existence of sex in trypanosomatids, the inheritance of kinetoplast DNA (maxi- and minicircles), the impact of genetic exchange in these parasites, and how it can contribute to the phenotypic diversity of natural populations.

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A DFT study of spherands containing five anisyl groups — Highly preorganized to bind the alkali metal

Canadian Journal of Chemistry ◽

10.1139/v06-130 ◽

2006 ◽

Vol 84 (8) ◽

pp. 1045-1049 ◽

Cited By ~ 4

Author(s):

Shabaan AK Elroby ◽

Kyu Hwan Lee ◽

Seung Joo Cho ◽

Alan Hinchliffe

Keyword(s):

Density Functional Theory ◽

Binding Energy ◽

Density Functional ◽

Ionic Radius ◽

Binding Energies ◽

Cavity Size ◽

X Ray Diffraction ◽

Functional Theory ◽

X Ray ◽

Good Agreement

Although anisyl units are basically poor ligands for metal ions, the rigid placements of their oxygens during synthesis rather than during complexation are undoubtedly responsible for the enhanced binding and selectivity of the spherand. We used standard B3LYP/6-31G** (5d) density functional theory (DFT) to investigate the complexation between spherands containing five anisyl groups, with CH2–O–CH2 (2) and CH2–S–CH2 (3) units in an 18-membered macrocyclic ring, and the cationic guests (Li+, Na+, and K+). Our geometric structure results for spherands 1, 2, and 3 are in good agreement with the previously reported X-ray diffraction data. The absolute values of the binding energy of all the spherands are inversely proportional to the ionic radius of the guests. The results, taken as a whole, show that replacement of one anisyl group by CH2–O–CH2 (2) and CH2–S–CH2 (3) makes the cavity bigger and less preorganized. In addition, both the binding and specificity decrease for small ions. The spherands 2 and 3 appear beautifully preorganized to bind all guests, so it is not surprising that their binding energies are close to the parent spherand 1. Interestingly, there is a clear linear relation between the radius of the cavity and the binding energy (R2 = 0.999).Key words: spherands, preorganization, density functional theory, binding energy, cavity size.

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np-Pair Correlations in the Isovector Pairing Model

Symmetry ◽

10.3390/sym13081405 ◽

2021 ◽

Vol 13 (8) ◽

pp. 1405

Author(s):

Feng Pan ◽

Yingwen He ◽

Lianrong Dai ◽

Chong Qi ◽

Jerry P. Draayer

Keyword(s):

Binding Energy ◽

Occupation Number ◽

Mean Field ◽

Energy Difference ◽

Binding Energies ◽

Pair Correlations ◽

Isospin Symmetry Breaking ◽

Pairing Model ◽

Proton Pairing ◽

Spin Basis

A diagonalization scheme for the shell model mean-field plus isovector pairing Hamiltonian in the O(5) tensor product basis of the quasi-spin SUΛ(2) ⊗ SUI(2) chain is proposed. The advantage of the diagonalization scheme lies in the fact that not only can the isospin-conserved, charge-independent isovector pairing interaction be analyzed, but also the isospin symmetry breaking cases. More importantly, the number operator of the np-pairs can be realized in this neutron and proton quasi-spin basis, with which the np-pair occupation number and its fluctuation at the J = 0+ ground state of the model can be evaluated. As examples of the application, binding energies and low-lying J = 0+ excited states of the even–even and odd–odd N∼Z ds-shell nuclei are fit in the model with the charge-independent approximation, from which the neutron–proton pairing contribution to the binding energy in the ds-shell nuclei is estimated. It is observed that the decrease in the double binding-energy difference for the odd–odd nuclei is mainly due to the symmetry energy and Wigner energy contribution to the binding energy that alter the pairing staggering patten. The np-pair amplitudes in the np-pair stripping or picking-up process of these N = Z nuclei are also calculated.

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Coronavirus, the great toilet paper panic and civilisation

Thesis Eleven ◽

10.1177/07255136211033167 ◽

2021 ◽

pp. 072551362110331

Author(s):

Jon Stratton

Keyword(s):

General Population ◽

Federal Government ◽

Perceived Threat ◽

The Novel ◽

Social Breakdown ◽

Toilet Paper ◽

Western Civilisation ◽

Novel Coronavirus ◽

Key Aspects ◽

The Impact

Panic buying of toilet rolls in Australia began in early March 2020. This was related to the realisation that the novel coronavirus was spreading across the country. To the general population the impact of the virus was unknown. Gradually the federal government started closing the country’s borders. The panic buying of toilet rolls was not unique to Australia. It happened across all societies that used toilet paper rather than water to clean after defecation and urination. However, research suggests that the panic buying was most extreme in Australia. This article argues that the panic buying was closely linked to everyday notions of Western civilisation. Pedestal toilets and toilet paper are key aspects of civilisation and the fear of the loss of toilet paper is connected to anxiety about social breakdown, the loss of civilisation. This is the fear manifested in the perceived threat posed by the virus.

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Interfacial Adhesion of Cu to Self-Assembled Monolayers on SiO2

MRS Proceedings ◽

10.1557/proc-695-l7.7.1 ◽

2001 ◽

Vol 695 ◽

Author(s):

G. Cui ◽

M. Lane ◽

K. Vijayamohanan ◽

G. Ramanath

Keyword(s):

Binding Energy ◽

Photoelectron Spectroscopy ◽

Interfacial Adhesion ◽

Adhesion Energy ◽

Binding Energies ◽

Self Assembled Monolayers ◽

Chemical Binding ◽

Barrier Materials ◽

Assembled Monolayers ◽

Self Assembled

ABSTRACTAs the critical feature size in microelectronic devices continues to decrease below 100 nm, new barrier materials of > 5 nm thickness are required. Recently we have shown that self-assembled monolayers (SAMs) are attractive candidates that inhibit Cu diffusion into SiO2. For SAMs to be used as barriers in real applications, however, they must also promote adhesion at the Cu/dielectric interfaces. Here, we report preliminary quantitative measurements of interfacial adhesion energy and chemical binding energy of Cu/SiO2 interfaces treated with nitrogen-terminated SAMs. Amine-containing SAMs show a ~10% higher adhesion energy with Cu, while interfaces with Cu-pyridine bonds actually show degraded adhesion, when compared with that of the reference Cu/SiN interface. However, X-ray photoelectron spectroscopy (XPS) measurements show that Cu-pyridine and Cu-amine interactions have a factor-of-four higher binding energy than that of Cu-N bonds at Cu/SiN interfaces. The lack of correlation between adhesion and chemical binding energies is most likely due to incomplete coverage of SAMs.

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