Theoretical study and analysis of o-nitrophenol adsorption using layered double hydroxides containing Ca-Al, Ni-Al and Zn-Al

A theoretical assessment of the o-nitrophenol adsorption on layered double hydroxides containing different metallic species (Ca-Al, Ni-Al and Zn-Al) was performed. Experimental o-nitrophenol adsorption isotherms obtained at different adsorption temperatures with these layered double hydroxides were analyzed using a statistical physics monolayer model. Model calculations showed that the o-nitrophenol aggregation could occur with a high degree. It was estimated that the o-nitrophenol adsorption implied a non-flat orientation on all adsorbent surfaces and this process was multi-molecular. It was also demonstrated that there was no significant difference on the o-nitrophenol adsorption capacities of tested adsorbents, which varied from 77 to 135, 95 to 122 and 74 and 130 mg/g for Ca-Al, Ni-Al and Zn-Al layered double hydroxides, respectively. This finding suggested that the incorporation of Ca-Al, Ni-Al and Zn-Al in the layered double hydroxide structure played a similar role to adsorb o-nitrophenol molecules from aqueous solution. Calculated adsorption energies and thermodynamic functions confirmed an exothermic adsorption with the presence of physical-based interaction forces. This paper highlights the importance of reliable theoretical calculations based on statistical physics theory to contribute in the understanding of the adsorption mechanisms of a relevant water pollutant using layered double hydroxides as promising adsorbents for industrial applications.

Hybrid localized graph kernel for machine learning energy-related properties of molecules and solids

Nowadays, the coupling of electronic structure and machine learning techniques serves as a powerful tool to predict chemical and physical properties of a broad range of systems. With the aim of improving the accuracy of predictions, a large number of representations for molecules and solids for machine learning applications has been developed. In this work we propose a novel descriptor based on the notion of molecular graph. While graphs are largely employed in classification problems in cheminformatics or bioinformatics, they are not often used in regression problem, especially of energy-related properties. Our method is based on a local decomposition of atomic environments and on the hybridization of two kernel functions: a graph kernel contribution that describes the chemical pattern and a Coulomb label contribution that encodes finer details of the local geometry. The accuracy of this new kernel method in energy predictions of molecular and condensed phase systems is demonstrated by considering the popular QM7 and BA10 datasets. These examples show that the hybrid localized graph kernel outperforms traditional approaches such as, for example, the smooth overlap of atomic positions and the Coulomb matrices.

Make it clean, make it safe: A review on virus elimination via adsorption

Recently, the potential dangers of viral infection transmission through water and air have become the focus of worldwide attention, via the spread of COVID-19 pandemic. The occurrence of large-scale outbreaks of dangerous infections caused by unknown pathogens and the isolation of new pandemic strains require the development of improved methods of viruses' inactivation. Viruses are not stable self-sustaining living organisms and are rapidly inactivated on isolated surfaces. However, water resources and air can participate in the pathogens' diffusion, stabilization, and transmission. Viruses inactivation and elimination by adsorption are relevant since they can represent an effective and low-cost method to treat fluids, and hence limit the spread of pathogen agents. This review analyzed the interaction between viruses and carbon-based, oxide-based, porous materials and biological materials (e.g., sulfated polysaccharides and cyclodextrins). It will be shown that these adsorbents can play a relevant role in the viruses removal where water and air purification mostly occurring via electrostatic interactions. However, a clear systematic vision of the correlation between the surface potential and the adsorption capacity of the different filters is still lacking and should be provided to achieve a better comprehension of the global phenomenon. The rationalization of the adsorption capacity may be achieved through a proper physico-chemical characterization of new adsorbents, including molecular modeling and simulations, also considering the adsorption of virus-like particles on their surface. As a most timely perspective, the results on this review present potential solutions to investigate coronaviruses and specifically SARS-CoV-2, responsible of the COVID-19 pandemic, whose spread can be limited by the efficient disinfection and purification of closed-spaces air and urban waters.

Investigation of tautomerism of 1,3,5-triazine derivative, stability, and acidity of its tautomers from density functional theory

Recent studies have identified N2,N4-bis(4-fluorophenethyl)-N6-(3-(dimethylamino)propyl)-1,3,5-triazine-2,4,6-triamine (1TZ(7,8,9)) as a potent, pure antagonist that inhibits thermosensory transient receptor potential vanilloid 1 channel (TRPV1) channel activity. This study provides theoretical data on the stability and acidity of the tautomers of this molecule. We show that this triazine can exist as three predominant tautomers (2TZ(5,7,8), 4TZ(3,7,9), 7TZ(1,8,9)). In the aqueous phase, equilibrium constants calculations show that only the tautomeric equilibria between 1TZ(7,8,9) and the three most stable triazines can be present which suggests that these three tautomeric equilibria would be the basis of 1TZ(7,8,9)'s biological activity.

Thymol nanoemulsion promoted broiler chicken's growth, gastrointestinal barrier and bacterial community and conferred protection against Salmonella Typhimurium

The present study involved in vivo evaluation of the growth promoting effects of thymol and thymol nanoemulsion and their protection against Salmonella Typhimurium infection in broilers. One-day old 2400 chicks were randomly divided into eight groups; negative and positive control groups fed basal diet without additives and thymol and thymol nanoemulsion groups (0.25, 0.5 and 1% each). At d 23, all chicks except negative control were challenged with S. Typhimurium. Over the total growing period, birds fed 1% thymol nanoemulsion showed better growth performance even after S. Typhimurium challenge, which came parallel with upregulation of digestive enzyme genes (AMY2A, PNLIP and CCK). Additionally, higher levels of thymol nanoemulsion upregulated the expression of MUC-2, FABP2, IL-10, IgA and tight junction proteins genes and downregulated IL-2 and IL-6 genes expression. Moreover, 1% thymol nanoemulsion, and to lesser extent 0.5% thymol nanoemulsion and 1% thymol, corrected the histological alterations of cecum and liver postinfection. Finally, supplementation of 1% thymol, 0.5 and 1% thymol nanoemulsion led to increased Lactobacilli counts and decreased S. Typhimurium populations and downregulated invA gene expression postinfection. This first report of supplying thymol nanoemulsion in broiler diets proved that 1% nano-thymol is a potential growth promoting and antibacterial agent.

Adsorption mechanisms of fatty acids on fluorite unraveled by infrared spectroscopy and first-principles calculations

HYPOTHESIS

The adsorption mechanisms of fatty acids on minerals are largely debated from years, and their understanding is now required to improve flotation processing in the critical context of raw materials. Three wavenumbers have been observed in the literature for the asymmetric stretching vibration of COO^- after the adsorption of fatty acids on mineral surfaces. They have been interpreted as different adsorbed forms, such as a precipitate formation, an adsorption of sole or bridged carboxylates, an anion exchange, or adsorbed modes, such as monodentate or bidentate configurations.

EXPERIMENTS/THEORY

Diffuse reflectance infrared Fourier transform spectroscopy was combined with ab initio molecular dynamics simulations and simulation of infrared spectra. Fluorite and sodium octanoate - or longer-chain fatty acids - were used as prototypical materials for all the investigations.

FINDINGS

At low fatty acids concentration, the asymmetric stretching vibration of COO^- peaks at 1560 cm^-1 while, at higher concentration, this infrared band converts into a doublet peaking at 1535 and 1575 cm^-1. Using simulations, we assign the band at 1560 cm^-1 to the adsorption of a carboxylate molecule bridged on a sodium counter-cation and the doublet at 1535 and 1575 cm^-1 to the adsorption of the sole carboxylate anion under a monodentate or a bidentate binuclear configuration, respectively. The formation of an adsorbed layer on the mineral surface is initiated by the adsorption of a sodium carboxylate and followed by the adsorption of mixed sole anionic forms. The role of the carboxylate counter-cation is highlighted for the first time, which was totally ignored in the literature beforehand. This particularly opens the path to the development of innovative strategies to enhance the separation contrast between minerals, which is of uttermost importance for the recovery of critical raw materials.

Structure-Elasticity Relationship of Potassium Silicate Glasses from Brillouin Light Scattering Spectroscopy and Molecular Dynamics Simulations

Brillouin light scattering (BLS) spectroscopy and molecular dynamic (MD) simulations allowed the identification of a relationship between the elastic properties and the structure of K-containing glasses of formula (K₂O)_x-(SiO₂)_1-x, having different K₂O concentrations. Excellent agreement was observed between experimental data and simulations. The peculiar elastic properties observed for these potassium silicate glasses have been extensively discussed in terms of structural and energetic features of the materials. Elastic properties were shown to be strongly dependent on the asymmetry of potential energy in the K-BO interactions and the K-NBO interactions. A low K₂O content (below 10-15% K₂O) appeared to be in favor of K⁺-BO interactions and high asymmetry of potential energy, whereas a high K₂O content (from 10 to 15% K₂O) was in favor of K⁺-NBO interactions with lower asymmetry. Our results suggest a possible explanation to the observed anomalous dependence of elastic properties of potassium silicate glasses with K₂O amount.

Disclosing the behavior under hydrostatic pressure of rhombohedral MgIn2Se4 by means of first-principles calculations

AM2X4 crystalline materials display important technological electronic, optical and magnetic properties that are sensitive to general stress effects. In this paper, the behavior under hydrostatic pressure of the ambient condition rhombohedral phase of MgIn2Se4 is investigated in detail for the first time. We carried out first-principles calculations within the density functional theory framework aimed at determining the pressure-induced polymorphic sequence of this selenide. To accurately evaluate transition pressures at room temperature, thermal corrections have been included after the computation of phonon dispersion curves in potential candidate phases, namely the initial rhombohedral R3[combining macron]m one, inverse and direct spinels, LiTiO2-type and defective I4[combining macron] structures. Only the transition from the R3[combining macron]m to the inverse spinel phase was found to fulfill the thermodynamic and mechanical stability criteria. The direct spinel could appear as metastable if kinetic effects hinder the above transition. Additionally, electronic band structures and chemical bonding properties were analyzed from the outcome of our quantum-mechanical solutions reporting band gap values and ionicity and noncovalent interaction indexes. It is shown that the investigated compound keeps behaving as a semiconductor, loses its van der Waals interactions, and becomes more covalent as hydrostatic pressure is applied.

In silico drug discovery of IKK-β inhibitors from 2-amino-3-cyano-4-alkyl-6-(2-hydroxyphenyl) pyridine derivatives based on QSAR, docking, molecular dynamics and drug-likeness evaluation studies

The Inhibitor of IKK-β (nuclear factor kappa B kinase subunit beta), a specific modulator of NF-κB (nuclear factor-κB), is considered a valid target to discover new active compounds for various cancers and rheumatoid arthritis treatment. In this study a series of thirty 2-amino-3-cyano-4-alkyl-6-(2-hydroxyphenyl) pyridine derivatives was involved for a quantitative structure activity relationship model (QSAR) elaboration which allows the prediction of the pIC50 values of new designed compounds. The model can be used to predict the activity of new compounds within its applicability domain. Then a molecular docking study was carried out to identify the interactions between the compounds and the amino acids of the active site. After that, golden triangle, Veber's rule, and Lipinski's rule properties were calculated to identify the drug-likeness properties of the investigated compounds. Finally, in-silico-toxicity studies were performed to predict the toxicity of the new designed compounds. The analysis of the results of QSAR model and molecular docking succeeded to screen 21 interesting compounds with better inhibitory concentration having a good affinity to IKK-β. All compounds were within the range set by Veber's rule and Lipinski's rule. the analysis of golden triangle showed that the thirty 2-amino-3-cyano-4-alkyl-6-(2-hydroxyphenyl) pyridine derivatives would not have clearance and cell membrane permeability problems except comp6 comp12,comp20, comp21, and comp26.As for the new designed compounds, their properties may have these problems, except two compounds which are: A8m, A8p. The A1m, A1p, A3p and A11m compounds were predicted to be nontoxic. These findings indicate that the novel potent candidate drugs have promising potential to IKK-β enzyme inhibition and should motivate future experimental investigations.Communicated by Ramaswamy H. Sarma.

DNA Nucleobase under Ionizing Radiation: Unexpected Proton Transfer by Thymine Cation in Water Nanodroplets

The effect of ionizing radiation on DNA constituents is a widely studied fundamental process using experimental and computational techniques. In particular, radiation effects on nucleobases are usually tackled by mass spectrometry in which the nucleobase is embedded in a water nanodroplet. Here, we present a multiscale theoretical study revealing the effects and the dynamics of water droplets towards neutral and ionized thymine. In particular, by using both hybrid quantum mechanics/molecular mechanics and full ab initio molecular dynamics, we reveal an unexpected proton transfer from thymine cation to a nearby water molecule. This leads to the formation of a neutral radical thymine and a Zundel structure, while the hydrated proton localizes at the interface between the deprotonated thymine and the water droplet. This observation opens entirely novel perspectives concerning the reactivity and further fragmentation of ionized nucleobases.

Incorporation of trivalent cations in NaX zeolite nanocrystals for the adsorption of O2 in the presence of CO2

The O₂ and CO₂ sorption properties of nanosized zeolite X with faujasite type structure through a partial ionic exchange of sodium (Na⁺) by trivalent cations (Gd³⁺ and Ce³⁺) were evaluated. Three faujasite samples were studied, the as-synthesized Na-X possessing Na⁺ solely, and the modified samples Na-Gd-X and Na-Ce-X containing Gd³⁺ (1.8 wt%) and Ce³⁺ (0.82 wt%), respectively. Incorporating scarce amounts of trivalent cations modified the adsorption affinity of zeolites towards O₂ and CO₂ as demonstrated by in situ Fourier-transform infrared spectroscopy (FTIR). While Na-Ce-X encounters the highest O₂ physisorption capacity, the Na-Gd-X is adsorbing the highest quantities of molecular CO₂. All three samples exhibit the chemisorbed CO₂ in the form of carbonates, while the Na-X stores carbonates in monodentate and polydentate forms, the Na-Gd-X and Na-Ce-X allow the formation of polydentate carbonates only. Density functional theory (DFT) calculations revealed that trivalent cations tend to adsorb gases through two cations simultaneously which explains the presence of polydentate carbonates exclusively in the corresponding modified zeolites. The DFT results confirmed the higher affinity of Na-Gd-X and Na-Ce-X nanocrystals towards O₂ in the presence of CO₂. The affinity of Na-Gd-X and Na-Ce-X nanocrystals towards O₂ opens the door of their use as oxygen transporters for medical applications where CO₂ is constantly present. The toxicity of the nanosized zeolites and their performance in O₂ release are reported too.

The Challenge of Tungsten Skarn Processing by Froth Flotation: A Review

Recently, tungsten has drawn worldwide attention considering its high supply risk and economic importance in the modern society. Skarns represent one of the most important types of tungsten deposits in terms of reserves. They contain fine-grained scheelite (CaWO₄) associated with complex gangue minerals, i.e., minerals that display similar properties, particularly surface properties, compared to scheelite. Consistently, the froth flotation of scheelite still remains, in the twenty first century, a strong scientific, industrial, and technical challenge. Various reagents suitable for scheelite flotation (collectors and depressants, mostly) are reviewed in the present work, with a strong focus on the separation of scheelite from calcium salts, namely, fluorite, apatite, and calcite, which generally represent significant amounts in tungsten skarns. Albeit some reagents allow increasing significantly the selectivity regarding a mineral, most reagents fail in providing a good global selectivity in favor of scheelite. Overall, the greenest, most efficient, and cheapest method for scheelite flotation is to use fatty acids as collectors with sodium silicate as depressant, although this solution suffers from a crucial lack of selectivity regarding the above-mentioned calcium salts. Therefore, the use of reagent combinations, commonly displaying synergistic effects, is highly recommended to achieve a selective flotation of scheelite from the calcium salts as well as from calcium silicates.

Ternary adsorption of cobalt, nickel and methylene blue on a modified chitin: Phenomenological modeling and physical interpretation of the adsorption mechanism

The simultaneous adsorption of three pollutants cobalt (Co), methylene blue (MB) and nickel (Ni) on a modified chitin surface from ternary systems was investigated. Multicomponent experimental adsorption data were determined at 298-328 K and pH 6. These experimental studies indicated that Ni adsorption was higher than those obtained for Co and MB. The multicomponent adsorption mechanism of this ternary system was analyzed with statistical physics theory where a set of new models with different hypotheses was developed and tested. Results showed that an adsorption model assuming that the pollutants Co, MB and Ni were adsorbed on three different types of modified chitin receptor sites was the most appropriate. This model was also utilized to calculate the corresponding adsorption energies to describe the possible interactions between these adsorbates and the surface of modified chitin. A general analysis of trends and magnitude of the model parameters provided a deeper understanding of the ternary adsorption mechanism at molecular level. Macroscopically, the ternary adsorption mechanism was interpreted via a calculation of three thermodynamic functions.

Copper-enriched diamond-like carbon coatings promote regeneration at the bone-implant interface

There have been several attempts to design innovative biomaterials as surface coatings to enhance the biological performance of biomedical implants. The objective of this study was to design multifunctional Cu/a-C:H thin coating depositing on the Ti-6Al-4V alloy (TC4) via magnetron sputtering in the presence of Ar and CH4 for applications in bone implants. Moreover, the impact of Cu amount and sp2/sp3 ratio on the interior stress, corrosion behavior, mechanical properties, and tribological performance and biocompatibility of the resulting biomaterial was discussed. X-ray photoelectron spectroscopy (XPS) revealed that the sp2/sp3 portion of the coating was enhanced for samples having higher Cu contents. The intensity of the interior stress of the Cu/a-C:H thin bio-films decreased by increase of Cu content as well as the sp2/sp3 ratio. By contrast, the values of Young's modulus, the H3/E2 ratio, and hardness exhibited no significant difference with enhancing Cu content and sp2/sp3 ratio. However, there was an optimum Cu content (36.8 wt.%) and sp2/sp3 ratio (4.7) that it is feasible to get Cu/a-C:H coating with higher hardness and tribological properties. Electrochemical impedance spectroscopy test results depicted significant improvement of Ti-6Al-4V alloy corrosion resistance by deposition of Cu/a-C:H thin coating at an optimum Ar/CH4 ratio. Furthermore, Cu/a-C:H thin coating with higher Cu contents showed better antibacterial properties and higher angiogenesis and osteogenesis activities. The coated samples inhibited the growth of bacteria as compared to the uncoated sample (p < 0.05). In addition, such coating composition can stimulate angiogenesis, osteogenesis and control host response, thereby increasing the success rate of implants. Moreover, Cu/a-C:H thin films encouraged development of blood vessels on the surface of titanium alloy when the density of grown blood vessels was increased with enhancing the Cu amount of the films. It is speculated that such coating can be a promising candidate for enhancing the osseointegration features.

Imprinting isolated single iron atoms onto mesoporous silica by templating with metallosurfactants

HYPOTHESIS

One of the main drawbacks of metal-supported materials, traditionally prepared by the impregnation of metal salts onto pre-synthesized porous supports, is the formation of large and unevenly dispersed particles. Generally, the larger are the particles, the lower is the number of catalytic sites. Maximum atom exposure can be reached within single-atom materials, which appear therefore as the next generation of porous catalysts.

EXPERIMENTS

Herein, we designed single iron atom-supported silica materials through sol-gel hydrothermal treatment using mixtures of a non-ionic surfactant (Pluronic P123) and a metallosurfactant (cetyltrimethylammoniumtrichloromonobromoferrate, CTAF) as porogens. The ratio between the Pluronic P123 and the CTAF enables to control the silica structural and textural properties. More importantly, CTAF acts as an iron source, which amount could be simply tuned by varying the non-ionic/metallo surfactants molar ratio.

FINDINGS

The fine distribution of iron atoms onto the silica mesopores results from the iron distribution within the mixed micelles, which serve as templates for the polymerization of the silica matrix. Several characterization methods were used to determine the structural and textural properties of the silica material (XRD, N₂ sorption isotherms and TEM) and the homogeneous distribution and lack of clustering of iron atoms in the resulting materials (elemental analysis, magnetic measurements, pair distribution function (PDF), MAS-NMR and TEM mapping). The oxidation and spin state of single-iron atoms determined from their magnetic properties were confirmed by DFT calculations. This strategy might find straightforward applications in preparing versatile single atom catalysts, with improved efficiency compared to nanosized ones.

Improved tribological properties, thermal and colloidal stability of poly-α-olefins based lubricants with hydrophobic MoS2 submicron additives

HYPOTHESIS

Newtonian liquids, usually used as base oil lubricants, exhibit low viscosity under extreme thermal conditions, needed for the functioning of wind turbines. This is directly affecting the colloidal stability and the tribological properties of the formulations containing additives, such as MoS₂. Here, it was hypothesized that the surface hydrophobization of MoS₂ particles will allow for an increased colloidal stability of the resulting formulations, for temperatures as high as 80 °C.

EXPERIMENTS

The antifriction properties and the thermal stability of the designed formulations were determined on submicron MoS₂ particles dispersed in poly-α-olefins (PAO) base oils of different dynamic viscosities (from 32 to 1650 mPa·s at 25 °C). The submicron particles of MoS₂ (300-500 nm in diameter) were synthesised by a simple one-pot solvothermal method under mild conditions. The resulting particles were hydrophobized in situ in PAO base oils using alkyltrichlorosilane grafting agents with two chain lengths (C8 and C18).

FINDINGS

The covalent grafting of alkylsilanes through Mo-O-Si bonds was confirmed by DFT calculations and FT-IR measurements. Turbiscan optical analysis revealed that thermal and colloidal stabilities can be significantly improved depending on oil viscosity and chain length of the grafting agent. The formulations in the PAO65 oil remained highly stable (TSI < 1), even at 80 °C. Herein, we demonstrate the impact of hydrophobization degree on the tribological properties of the lubricants, which, importantly, could reach ultra-low friction coefficients, less than 0.02.

Ab Initio Study of the Stepwise versus Concerted Fragmentation Pathways in Microhydrated Thymine Radical Cations

Thymine radiation-induced fragmentation is characterised by ring opening and the loss of HNCO/NCO. These pathways have been investigated using DFT calculations in the presence of zero, one and two water molecules. In addition to the already characterised stepwise fragmentation mechanism, we propose a novel concerted pathway reported here for the first time. We show that both the stepwise and concerted mechanisms are competitive with activation energies of 2.05 eV and 2.00 eV, respectively, in the gas phase. The effect of microhydration on these mechanisms are examined based on the most stable conformations found by an exploration of the potential energy surface performed by using DFT-based ab initio molecular dynamics. Microhydration is also accompanied by an increase in the activation energies, with respect to gas phase, amounting to 0.47 eV-an increase that is associated to a stabilising effect of water in agreement with recent experimental studies. However, we also point out that this effect is greatly dependent on the specific water arrangement around thymine and could be limited to only 0.13 eV for some configurations.

Quantum mechanistic study of furan and 2-methylfuran hydrodeoxygenation on molybdenum and tungsten sulfide clusters

One of the possibilities of limiting carbon dioxide emissions is to use pyrolysis oils from biomass. However, their very high oxygen content confers to these oils a chemical instability and a high viscosity. Among the oxygen-containing compounds present in bio-oils, furanic compounds derived from the decomposition of cellulosic and hemi-cellulosic biomass are the most refractory to deoxygenation. The major products of their hydrodeoxygenation are alkanes and secondly alkenes, but the intermediates are still subject to controversy. In this work, we performed a DFT simulation of the hydrodeoxygenation of furan (C₄H₄O) and 2-methylfuran in the presence of molybdenum and tungsten sulphide Mo(W)S_2. The aim of this work is to elucidate the reaction intermediates and to compare the activities of the two catalytic sites used in our reaction conditions. Our calculations show that the partial hydrogenation of the two molecules occurs preferentially in position (2,5). The hydrogenolysis reactions of the C-O bonds occur in two steps. The molybdenum sulphide exhibits higher catalytic activity.

A first principle evaluation of the adsorption mechanism and stability of volatile organic compounds into NaY zeolite

Removal of volatile organic compounds (VOCs) from indoor or outdoor environments is an urgent challenge for the protection of human populations. Inorganic sorbents such as zeolites are a promising solution to tackle this issue. Using dispersion corrected periodic DFT calculations, we have studied the interaction between sodium-exchanged faujasite zeolite and a large set of VOCs including aromatics, oxygenates and chlorinated compounds. The computed interaction energies range from about −25 (methane) to −130 kJ/mol (styrene). Methane is by far the less interacting specie with the NaY zeolite. All other VOCs present interaction energies higher in absolute value than 69 kJ/mol. Most of them show a similar adsorption strength, between −70 and −100 kJ/mol. While the electrostatic interactions are important in the case of oxygenates and acrylonitrile, van der Waals interactions predominate in hydrocarbons and chlorides. By monitoring the variation of molecular bond lengths of the different VOCs before and after adsorption, we have then evaluated the tendency of adsorbate to react and form by-products, since a significant stretching would evidently lead to the activation of the bond. While hydrocarbons, tetrachloroethylene and acrylonitrile seem to be not activated upon adsorption, all oxygenates and 1,1,2-trichloroethane could possibly react once adsorbed.

Dibenzyl Disulfide Adsorption on Cationic Exchanged Faujasites: A DFT Study

Although dibenzyl disulfide (DBDS) is used as a mineral oil stabilizer, its presence in electrical transformer oil is associated as one of the major causes of copper corrosion and subsequent formation of copper sulfide. In order to prevent these undesirable processes, MY zeolites (with M = Li, Na, K, Cs, Cu or Ag) are proposed to adsorb molecularly DBDS. In this study, different MY zeolites are investigated at the DFT+D level in order to assess their ability in DBDS adsorption. It was found that CsY, AgY and CuY exhibit the best compromise between high interaction energies and limited S-S bond activation, thus emerging as optimal adsorbents for DBDS.

Benchmarking the performance of approximate van der Waals methods for the structural and energetic properties of SiO2 and AlPO4 frameworks

Density functional theory (DFT) calculations using sixteen different approaches, fourteen of which were designed to include dispersion interactions [DFT + D and van der Waals (vdW)-DF methods], were performed for a set of sixteen framework compounds with either SiO₂ or AlPO₄ composition. The compounds include four dense structures (α-quartz, α-cristobalite, and their AlPO₄ analogues), eight all-silica zeolites, and four aluminophosphate zeotypes (AlPOs). We analyzed the performance in reproducing the equilibrium structure for all systems, and computed bulk moduli and relative stabilities were compared to experiments for those compounds where experimental data are available. We found that the results obtained with functionals that take into account dispersive interactions are closer to experiments than those obtained with a bare generalized gradient functional. However, the variation among individual methods is considerable, and functionals that perform well for one quantity may give rather large deviations for another. Taking together the whole body of results, it appears that the Perdew-Burke-Ernzerhof functional including a many-body dispersion correction and the rev-vdW-DF2 methods present the best performance for the description of SiO₂ and AlPO₄ materials.

Ionization and fragmentation of uracil upon microhydration

We study at the DFT level the ionization and the fragmentation of uracil in the presence of zero, one and two water molecules, to unravel the effect of microhydration on the reactivity of this nucleobase. We show that the microhydration lowers the adiabatic and vertical ionization potentials by 0.41 eV and 0.22 eV, respectively. Furthermore, microhydration increases the activation energies of the different dissociation channels up to 0.5 eV and restricts the formation of some fragments, in particular those corresponding to the C5-C6 fragmentation pathway. For the first time, our theoretical study shows new transition states and minima not found for the gas phase, hence indicating a change in the fragmentation mechanisms, as well as a stabilizing effect of microhydration, confirming previous experimental studies.

Proton Mobility, Intrinsic Acid Strength, and Acid Site Location in Zeolites Revealed by Varying Temperature Infrared Spectroscopy and Density Functional Theory Studies

The intrinsic Brønsted acid strength in solid acids relates to the energy required to separate a proton from a conjugate base, for example a negatively charged zeolite framework. The reliable characterization of zeolites' intrinsic acidity is fundamental to the understanding of acid catalysis and setting in relation solid Brønsted acids with their activity and selectivity. Here, we report an infrared spectroscopic study with partial isotopic deuterium exchange of a series of 15 different acidic aluminosilicate materials, including ZSM-5 zeolites with very few defects. Varying Temperature Infrared spectroscopy (VTIR) permitted estimating activation energies for proton diffusion. Two different proton transfer mechanisms have been distinguished for two different temperature ranges. Si-rich zeolites appeared to be promising proton-transfer materials ( E_act. < 40 kJ mol^-1) at temperatures above 150 °C (423 K). Further, a linear bathochromic shift of the Si-(OD)-Al stretching vibration as a function of temperature was observed. It can be assumed that this red-shift is related to the intrinsic O-(H/D) bond strength. This observation allowed the extrapolation and estimation of precise v(O-D)@0 K values, which could be attributed to distinct crystallographic locations through Density Functional Theory (DFT) calculations. The developed method was used to reliably determine the likelihood of the position of a proton in ZSM-5 zeolites under catalytically relevant conditions ( T > 423 K), which has so far never been achieved by any other technique.

Comparative study of structural and electronic properties of GaSe and InSe polytypes

Equilibrium crystal structures, electron band dispersions, and bandgap values of layered GaSe and InSe semiconductors, each being represented by four polytypes, are studied via first-principles calculations within the density functional theory. A number of practical algorithms to take into account dispersion interactions are tested, from empirical Grimme corrections to many-body dispersion schemes. Due to the utmost technical accuracy achieved in the calculations, nearly degenerate energy-volume curves of different polytypes are resolved, and the conclusions concerning the relative stability of competing polytypes drawn. The predictions are done as for how the equilibrium between different polytypes will be shifted under the effect of hydrostatic pressure. The band structures are inspected under the angle of identifying features specific for different polytypes and with respect to modifications of the band dispersions brought about by the use of modified Becke-Johnson (mBJ) scheme for the exchange-correlation potential. As another way to improve the predictions of bandgaps values, hybrid functional calculations according to the HSE06 scheme are performed for the band structures, and the relation with the mBJ results are discussed. Both methods nicely agree with the experimental results and with state-of-the-art GW calculations. Some discrepancies are identified in cases of close competition between the direct and indirect gap (e.g., in GaSe); moreover, the accurate placement of bands revealing relatively localized states is slightly different according to mBJ and HSE06 schemes.

A DFT study of RuO4 interactions with porous materials: metal–organic frameworks (MOFs) and zeolites

The potential use of zeolite and MOF materials for the capture of RuO₄ has been investigated for the first time. A hydrated form of HKUST-1 could be a promising sorbent due to its ability to form multiple hydrogen bonds.

Testing for HTLV 1 and HTLV 2 among blood donors in Western Saudi Arabia: prevalence and cost considerations

BACKGROUND

Screening all blood donors for human T-cell lymphotropic viruses 1 and 2 (HTLV 1 and HTLV 2) is mandatory in Saudi Arabia. The aim of this study is to evaluate the results and costs associated with the current testing policy for HTLV 1 and HTLV 2 in blood donors at King Abdulaziz University Hospital (KAUH), Jeddah.

STUDY DESIGNS AND METHODS

Donor-testing results from Blood Transfusion Services at KAUH were reviewed over a 10-year period, from January 2006 through December 2015. All donors were screened using chemiluminescent microparticle immunoassay. Reactive samples were then tested by Western blot for confirmation. Costs associated with testing were calculated.

RESULTS

Data of 107 419 donations in the study period were reviewed. Saudi nationals constituted 51 168 donors (47·6%). Of 107 419 blood donors tested for HTLV 1 and HTLV 2 antibody, and 95 (0·088%) donors were reactive to screening tests. None of the samples found to be reactive to screening tests was positive by Western blot. The average cost of testing was US$ 171 870 per year.

CONCLUSION

No donors were confirmed to have HTLV 1 and HTLV 2 in this cohort exceeding 100 000 donors. We propose changes to the policy mandating universal testing by replacing it with universal leukodepletion coupled with targeted screening to donors coming from endemic area or donors at risk. Such changes are expected to lead to a reduction of testing cost without affecting safety.

Research Note. One minute, intraoperative assessment of the viability of hydatid cysts using a simple reagent strip test

The aim of the current work was to evaluate the possibility of using a rapid and simple reagent strip test to investigate the viability of hydatid cysts intraoperatively, via testing certain biochemical parameters. Thirty eight HCF samples were processed and examined by different methods for determining the viability status. Using the reagent strip test in the current study, the highest significant level of glucose was detected in HCF samples with the highest viability % at pH 7.5 and the lowest significant level of glucose was detected in HCF samples with the lowest viability % at pH 8.5, indicating a likely correlation between glucose concentration and the viability of PSs. On the contrary, protein was not detected in HCF containing viable PSs and was found to be higher in HCF containing non-viable PSs, denoting the possible degenerative processes in such PSs. Haemoglobin was found in trace amounts in all of our samples. In addition, the strip test detected bacterial contamination in 8 samples and biliary leakage in 7 samples. Our results suggest that the simple reagent strip test can assist in providing fast, uncomplicated primary data regarding the viability status of the hydatid cysts. Thus, it may aid the surgeons to make informed decisions for further management and appropriate follow up to minimise the risk of post-operative recurrence.

Performance of CuII -, PbII -, and HgII -Exchanged Mordenite in the Adsorption of I2 , ICH3 , H2 O, CO, ClCH3 , and Cl2 : A Density Functional Study

Periodic dispersion-corrected DFT is used to investigate the adsorption of I₂ and ICH₃ , which may be released during a severe nuclear accident, for three divalent cation (Cu²⁺ , Pb²⁺ and Hg²⁺ )-exchanged mordenites with an Si/Al ratio of 23. Gases such as H₂ O, CO, ClCH₃ , and Cl₂ present in the containment atmosphere can inhibit the selective adsorption of iodine species. To identify the most promising adsorbents, a systematic study is performed in which all the possible cationic sites in the main channel of the mordenite structure are considered. For the energetically most stable sites, the divalent cation is located in the small rings (five- or six-membered) containing two Al atoms, while in the energetically less stable configurations, the two Al atoms are far apart (>7 Å) and the cation is close to only one Al atom. Upon adsorption of the various molecules, the coordination number of the cation decreases with increasing interaction energy, as the molecules can attract the divalent cations from the framework. Finally, the computed interaction energies show that Hg-mordenite (MOR) could be a suitable material for selective adsorption of volatile iodine species, contrary to Cu-MOR and Pb-MOR.

Performance of CuII -, PbII -, and HgII -Exchanged Mordenite in the Adsorption of I2 , ICH3 , H2 O, CO, ClCH3 , and Cl2 : A Density Functional Study

Periodic dispersion-corrected DFT is used to investigate the adsorption of I₂ and ICH₃ , which may be released during a severe nuclear accident, for three divalent cation (Cu²⁺ , Pb²⁺ and Hg²⁺ )-exchanged mordenites with an Si/Al ratio of 23. Gases such as H₂ O, CO, ClCH₃ , and Cl₂ present in the containment atmosphere can inhibit the selective adsorption of iodine species. To identify the most promising adsorbents, a systematic study is performed in which all the possible cationic sites in the main channel of the mordenite structure are considered. For the energetically most stable sites, the divalent cation is located in the small rings (five- or six-membered) containing two Al atoms, while in the energetically less stable configurations, the two Al atoms are far apart (>7 Å) and the cation is close to only one Al atom. Upon adsorption of the various molecules, the coordination number of the cation decreases with increasing interaction energy, as the molecules can attract the divalent cations from the framework. Finally, the computed interaction energies show that Hg-mordenite (MOR) could be a suitable material for selective adsorption of volatile iodine species, contrary to Cu-MOR and Pb-MOR.

Thermodynamic and structural properties of binary calcium silicate glasses: insights from molecular dynamics

The thermodynamic and structural properties of calcium-modified binary silicate glasses have been computed using molecular dynamics simulations.

Dissociative iodomethane adsorption on Ag-MOR and the formation of AgI clusters: an ab initio molecular dynamics study

Using ab initio MD simulations, a full transformation path of iodomethane in Ag-MOR is explored: from adsorption to formation of AgI clusters.