Theoretical study of fructose adsorption and conversion to trioses on metal-organic frameworks.

The conversion of chemically modified biomass into more valuable chemicals has recently gained significant attention from industry. In this study, we investigate the adsorption of fructose and its conversion into two trioses, glyceraldehyde (GLA) and dihydroxyacetone (DHA), on metal-organic frameworks using density functional theory calculations. The reaction mechanism proceeds through two main steps: first, the opening of the fructose ring; second, the retro-aldol fragmentation, which is favored over intramolecular hydrogen shifts. The substitution of a tetravalent metal in the metal-organic framework leads to different adsorption strengths in the order Hf-NU-1000 > Zr-NU-1000 > Ti-NU-1000. The catalytic activities of Hf-NU-1000 and Zr-NU-1000 are found to be similar. Both are more active than Ti-NU1000, corresponding to their relative Lewis acidity. It was found that functionalization of the organic linkers of the Hf-NU-1000 MOF does not improve its catalytic activity. The catalytic activity follows the order Hf-MOF-808 > Hf-NU-1000 > Hf-UIO-66 when based on either the overall activation energy or the turnover frequency (TOF).

A Simple Electron-Density Based Force Field Model for High-Energy Interactions between Atoms and Molecules.

In high-energy molecular dynamics or Monte Carlo simulations, standard force fields optimized for simulations at ambient temperatures are inadequate. This is largely because their repulsive parts have been regarded as not very significant, even well below zero interaction energies. It is, therefore, not obvious which force fields to resort to for simulating hot gases or plasmas. A force field model that uses the electronic densities of noninteracting atoms or molecules within the pair approximation is introduced. We start by deriving a naïve model that neglects any exchange and correlation effects between the electronic clouds and then correct this model by adding a term calibrated from ab initio calculations using the CCSD(T)/cc-pVTZ level of theory. The resulting expression for this term can be regarded as a simple exchange-correlation function. We compare the results for the repulsive part of the potential energy hypersurfaces with the force fields commonly used on some dimers of small molecules.

Multi-layer inverse design of vertical grating couplers for high-density, commercial foundry interconnects.

Density-based topology optimization is used to design large-scale, multi-layer grating couplers that comply with commercial foundry fabrication constraints while simultaneously providing beam profiles that efficiently couple to a single-mode optical fiber without additional optics. Specifically, we describe the design process and experimentally demonstrate both single- and dual-polarization grating couplers that couple at normal incidence (0° from the normal) with low backreflections (-13.7 dB and -15.4 dB at the center wavelength), broad 3 dB bandwidths (75 nm and 89 nm), and standard coupling efficiencies (-4.7 dB and -7.0 dB). The dual-polarization grating couplers exhibit over 30 dB of polarization extinction across the entire band. The devices were fabricated on the GlobalFoundries 45CLO CMOS platform and characterized across three separate wafers. This new design approach produces distinct features for multiple foundry layers and yields emitters with arbitrary, user-specified far-field profiles.

Sensing the ortho Positions in C6Cl6 and C6H4Cl2 from Cl2- Formation upon Molecular Reduction.

The geometrical effect of chlorine atom positions in polyatomic molecules after capturing a low-energy electron is shown to be a prevalent mechanism yielding Cl2-. In this work, we investigated hexachlorobenzene reduction in electron transfer experiments to determine the role of chlorine atom positions around the aromatic ring, and compared our results with those using ortho-, meta- and para-dichlorobenzene molecules. This was achieved by combining gas-phase experiments to determine the reaction threshold by means of mass spectrometry together with quantum chemical calculations. We also observed that Cl2- formation can only occur in 1,2-C6H4Cl2, where the two closest C-Cl bonds are cleaved while the chlorine atoms are brought together within the ring framework due to excess energy dissipation. These results show that a strong coupling between electronic and C-Cl bending motion is responsible for a positional isomeric effect, where molecular recognition is a determining factor in chlorine anion formation.

Electron-impact ionization cross sections of small molecules containing Fe and Cr∗.

We present the electron-impact ionization cross sections (EICSs) of iron and chromium hydrides, nitrides, and oxides. The motivation of this work stems from the fact that chemical sputtering from a steel surface exposed to a hot plasma can create these molecules which in turn influence the composition and energy balance of the plasma. The latter influence is quantified by the EICS which we derive by using two semi-empirical methods which can be employed in the relevant energy range of 10-1000 eV. They are important molecular properties for plasma- and materials science. We discuss the foundations of the methods and present the cross sections of the high- and low-spin states of the species in their neutral ground states and of their cations.

Understanding the interactions between lithium polysulfides and anchoring materials in advanced lithium-sulfur batteries using density functional theory.

Lithium-sulfur batteries (LSBs) are promising energy storage devices because of their high theoretical capacity and energy density. However, the "shuttle" effect in lithium polysulfides (LiPSs) is an unresolved issue that can hinder their practical commercial application. Research on LSBs has focused on finding appropriate materials that suppress this effect by efficiently anchoring the LiPSs intermediates. Quantum chemical computations are a useful tool for understanding the mechanistic details of chemical interaction involving LiPSs, and they can also offer strategies for the rational design of LiPSs anchoring materials. In this perspective, we highlight computational and theoretical work performed on this topic. This includes elucidating and characterizing the adsorption mechanisms, and the dominant types of interactions, and summarizing the binding energies of LiPSs on anchoring materials. We also give examples and discuss the potential of descriptors and machine learning approaches to predict the adsorption strength and reactivity of materials. We believe that both approaches will become indispensable in modelling future LSBs.

Adsorption and dehydration of ethanol on isomorphously B, Al, and Ga substituted H-ZSM-5 zeolite: an embedded ONIOM study.

Dehydration reactions are important in the petroleum and petrochemical industries, especially for the feedstock production. In this work, the catalytic activity of zeolites with different acidities for the dehydration of ethanol to ethylene and diethylether is investigated by density functional calculations on cluster models of three isomorphous B, Al, and Ga substituted H-ZSM-5 zeolites. Both unimolecular and bimolecular mechanisms are investigated. Detailed reaction profiles for the dehydration reaction, assuming either a stepwise or a concerted mechanism, were calculated by using the ONIOM(MP2:M06-2X) + SCREEP method. The adsorption energies of ethanol are -21.6, -28.1, and -27.7 kcal mol-1 on H-[B]-ZSM-5, H-[Al]-ZSM-5, and H-[Ga]-ZSM-5 zeolites, respectively. The activation energies for the rate-determining step of the unimolecular concerted mechanism for the ethylene formation are 48.5, 42.6, and 43.6 kcal mol-1 on H-[B]-ZSM-5, H-[Al]-ZSM-5, and H-[Ga]-ZSM-5 zeolites, respectively. The activation energies for the ethoxy formation as the rate-determining step for the bimolecular formation of diethylether are 42.3, 40.0, and 41.1 kcal mol-1 on H-[B]-ZSM-5, H-[Al]-ZSM-5, and H-[Ga]-ZSM-5 zeolites, respectively. The results indicate that the catalytic activities for the dehydration of ethanol decrease in the order H-[Al]-ZSM-5 ~ H-[Ga]-ZSM-5 > H-[B]-ZSM-5. Besides the acid strength, the zeolite framework affects the reaction by stabilizing the reaction intermediates, leading to more stable adsorption complexes and lower activation barriers.

Electronic structure and reactivity of tirapazamine as a radiosensitizer.

Tirapazamine (TP) has been shown to enhance the cytotoxic effects of ionizing radiation in hypoxic cells, thus making it a candidate for a radiosensitizer. This selective behavior is often directly linked to the abundance of O2. In this paper, we study the electronic properties of TP in vacuum, micro-hydrated from one up to three molecules of water and embedded in a continuum of water. We discuss electron affinities, charge distribution, and bond dissociation energies of TP, and find that these properties do not change significantly upon hydration. In agreement with its large electron affinity, and bond breaking triggered by electron attachment requires energies higher than 2.5 eV, ruling out the direct formation of bioactive TP radicals. Our results suggest, therefore, that the selective behavior of TP cannot be explained by a one-electron reduction from a neighboring O2 molecule. Alternatively, we propose that TP's hypoxic selectivity could be a consequence of O2 scavenging hydrogen radicals.

Right-to-left Ventricular Diameter Ratio At Computed Tomographic Pulmonary Angiography in Patients with Acute Pulmonary Embolism and Obstructive Sleep Apnea.

PURPOSE: Right ventricular (RV) dysfunction in acute pulmonary embolism (PE) is a critical determinant of outcome. Obstructive sleep apnea (OSA) is a common comorbidity of PE and might also affect RV function. Therefore, we sought to investigate RV dysfunction in PE patients in proportion to the severity of OSA by evaluating the right-to-left ventricular (RV/LV) diameter ratio on computed tomographic pulmonary angiography (CTPA). MATERIALS AND METHODS: 197 PE patients were evaluated for sleep-disordered breathing by portable monitoring and nocturnal polysomnography. RV dilatation was defined as an RV/LV diameter ratio of ⩾ 1.0. RESULTS: RV dilatation was significantly more frequent in OSA patients compared to study participants without OSA (66.4% vs 49.1%, P = .036). Elevated troponin I values, indicating myocardial injury due to acute, PE-related RV strain, were significantly more frequent in OSA patients with an apnea-hypopnea index (AHI) ⩾ 15/h compared to those with an AHI < 15/h (62.1% vs 45.8%, P = .035). However, RV dysfunction documented by the RV/LV diameter ratio on CTPA was not significantly associated with the severity of OSA in multivariable regression analysis. CONCLUSION: Patients with moderate or severe OSA might compensate acute, PE-related RV strain better, as they are adapted to repetitive right heart pressure overloads during sleep.

A global-scale data set of mining areas.

The area used for mineral extraction is a key indicator for understanding and mitigating the environmental impacts caused by the extractive sector. To date, worldwide data products on mineral extraction do not report the area used by mining activities. In this paper, we contribute to filling this gap by presenting a new data set of mining extents derived by visual interpretation of satellite images. We delineated mining areas within a 10 km buffer from the approximate geographical coordinates of more than six thousand active mining sites across the globe. The result is a global-scale data set consisting of 21,060 polygons that add up to 57,277 km2. The polygons cover all mining above-ground features that could be identified from the satellite images, including open cuts, tailings dams, waste rock dumps, water ponds, and processing infrastructure. The data set is available for download from https://doi.org/10.1594/PANGAEA.910894 and visualization at www.fineprint.global/viewer .

Dehydrogenation of ethanol to acetaldehyde with nitrous oxide over the metal-organic framework NU-1000: a density functional theory study.

The conversion of ethanol to more valuable hydrocarbon compounds receives great attention in chemical industries because it could diminish the dependency on petroleum as raw material. We investigate the catalytic performance of Fe-supported MOF NU-1000 for the dehydrogenation of ethanol to acetaldehyde with nitrous oxide (N2O) by deriving the relevant reaction profiles with density functional theory calculations. In the proposed mechanism, the activation barrier of the rate-determining step is almost four times lower in the presence of N2O than without it. The supported NU-1000 framework plays also important role since it facilitates electron transfers and stabilizes all species along the reaction coordinate. When considering the catalytic activity of tetravalent metal centers (Zr, Hf and Ti) substituted into NU-1000 it is found that their activity decreases in the order Hf ≥ Zr > Ti, based on activation energies and turnover frequencies (TOF). Concerning MOF linkers, we show that the catalytic activity is not further improved by functionalizing NU-1000 with either electron-donating or electron-withdrawing organic groups.

Iterative training set refinement enables reactive molecular dynamics via machine learned forces.

Machine learning approaches have been successfully employed in many fields of computational chemistry and physics. However, atomistic simulations driven by machine-learned forces are still very challenging. Here we show that reactive self-sputtering from a beryllium surface can be simulated using neural network trained forces with an accuracy that rivals or exceeds other approaches. The key in machine learning from density functional theory calculations is a well-balanced and complete training set of energies and forces. We have implemented a refinement protocol that corrects the low extrapolation capabilities of neural networks by iteratively checking and improving the molecular dynamic simulations. The sputtering yield obtained for incident energies below 100 eV agrees perfectly with results from ab initio molecular dynamics simulations and compares well with earlier calculations based on pair potentials and bond-order potentials. This approach enables simulation times, sizes and statistics similar to what is accessible by conventional force fields and reaching beyond what is possible with direct ab initio molecular dynamics. We observed that a potential fitted to one surface, Be(0001), has to be augmented with training data for another surface, Be(011̄0), in order to be used for both.

Obstructive sleep apnea is associated with pulmonary artery thrombus load, disease severity, and survival in acute pulmonary embolism.

INTRODUCTION: Obstructive sleep apnea (OSA) may have prothrombotic effects. OBJECTIVE: To investigate the effect of OSA on disease severity, pulmonary artery thrombus load, and prognosis in patients with acute pulmonary embolism (PE). METHODS: In 101 PE patients, disease severity was determined by the simplified PE severity index (sPESI) score, pulmonary artery thrombus load was quantified by the pulmonary artery obstruction index (PAOI), and sleep-disordered breathing was evaluated by nocturnal polygraphy. RESULTS: Obstructive sleep apnea patients with an apnea-hypopnea index (AHI) ≥ 15/h cohort were significantly older (p < 0.001) and had significantly lower oxygen saturations (p = 0.008) when acute PE was diagnosed. The sPESI scores (p < 0.001), the PAOI (p = 0.005) and the N-terminal pro-brain-type natriuretic peptide (NT-proBNP) values (p = 0.009), were significantly higher in the AHI ≥ 15/h subgroup. In a multivariate regression analysis, the AHI remains a significant predictor for sPESI scores ≥ 1 (p = 0.003), increased NT-proBNP levels (p = 0.047), and elevated PAOI (p = 0.032). During the median follow-up time of 53 (interquartile range 38-70) months, all-cause and cardiovascular-related mortality was significantly higher in the AHI ≥ 15/h cohort (p = 0.004 and p = 0.015, respectively). CONCLUSIONS: Obstructive sleep apnea is associated with pulmonary artery thrombus load, disease severity, and survival in acute PE possibly due to its prothrombotic effects.

Electron impact ionisation cross sections of cis- and trans-diamminedichloridoplatinum(II) and its hydrolysis products.

We report total electron-impact ionisation cross sections (EICSs) of cisplatin, its hydrolysis products and transplatin in the energy range from threshold to 10 keV using the binary-encounter-Bethe (BEB) and its relativistic variant (RBEB), and the Deutsch-Märk (DM) methods. We find reasonable agreement between all three methods, and we also note that the RBEB and the BEB methods yield very similar (almost identical) results in the considered energy range. For cisplatin, the resulting EICSs yield cross section maxima of 22.09 × 10-20 m2 at 55.4 eV for the DM method and 18.67 × 10-20 m2 at 79.2 eV for the (R)BEB method(s). The EICSs of monoaquated cisplatin yield maxima of 12.54 × 10-20 m2 at 82.8 eV for the DM method and of 9.74 × 10-20 m2 at 106 eV for the (R)BEB method(s), diaquated cisplatin yields maxima of 7.56 × 10-20 m2 at 118.5 eV for the DM method and of 5.77 × 10-20 m2 at 136 eV for the (R)BEB method(s). Molecular geometry does not affect the resulting EICS significantly, which is also reflected in very similar EICSs of the cis- and trans-isomer. Limitations of the work as well as desirable future directions in the research area are discussed.

D-Dimer Predicts Disease Severity but Not Long-Term Prognosis in Acute Pulmonary Embolism.

D-dimer might be correlated with prognosis in pulmonary embolism (PE). The predictive value of plasma D-dimer for disease severity and survival was investigated in the lowest and highest D-dimer quartile among 200 patients with PE. Patients with high D-dimers were significantly more often hypotensive (P = .001), tachycardic (P = .016), or hypoxemic (P = .001). Pulmonary arterial obstruction index (PAOI) values were significantly higher in the high D-dimer quartile (P < .001). Elevated troponin I (TNI) levels (P < .001), simplified PE severity indices ≥1 (P < .001), right-to-left ventricular (RV/LV) diameter ratios ≥1 (P < .001), and thrombolysis (P = .001) were more frequent in the high D-dimer quartile. D-dimer was associated with RV/LV ratios ≥1 (P = .021), elevated PAOI (P < .001) or TNI levels (P < .001), hypotension (P < .001), tachycardia (P = .003), and hypoxemia (P < .001), but not with long-term all-cause mortality. D-dimer predicts disease severity but not long-term prognosis in acute PE, possibly due to a more aggressive treatment strategy in severely affected patients.

Phenol Tautomerization Catalyzed by Acid-Base Pairs in Lewis Acidic Beta Zeolites: A Computational Study.

We investigate the tautomerization of phenol catalyzed by acid-base active pair sites in Lewis acidic Beta zeolites by means of density functional calculations using the M06-L functional. An analysis of the catalytic mechanism shows that hafnium on the Beta zeolite causes the strongest absorption of phenol compared to zirconium, tin, and germanium. This can be rationalized by the highest delocalization of electron density between the Lewis site and the oxygen of phenol which can in turn be quantified by the perturbative E(2) stabilization energy. The reaction is assumed to proceed in two steps, the phenol O-H bond dissociation and the protonation of the intermediate to form the cyclohexa-2,4-dien-1-one product. The rate determining step is the first one with a free activation energy of 26.3, 25.0, 22.1 and 22.7 kcal mol-1 for Ge-Beta, Sn-Beta, Zr-Beta, and Hf-Beta zeolites, respectively. The turnover frequencies follow these reaction barriers. Hence, the intrinsic catalytic activity of the Lewis acidic Beta zeolites studied here is in the order of Hf-Beta≈Zr-Beta>Sn-Beta> Ge-Beta for the tautomerization of phenol.

Total and partial electron impact ionization cross sections of fusion-relevant diatomic molecules.

We report calculations of total (and absolute) electron-impact ionization cross sections (EICSs) for the fusion-relevant diatomic molecular species BeH, BeN, BeO, WH, WBe, WN, WO, O2, and N2 by means of the Deutsch-Märk and the binary-encounter-Bethe methods in the energy range from threshold to 10 keV. In addition, we discuss an empirical scheme to estimate partial cross sections from the total ones based on reaction energetics and empirical threshold laws and explore its accuracy by assessing available experimental data on total and partial EICSs. Finally, we also report parameters obtained by fitting the calculated cross sections to an expression commonly used in fusion edge plasma modeling.

Computational study of the carbonyl-ene reaction between formaldehyde and propylene encapsulated in coordinatively unsaturated metal-organic frameworks M3(btc)2 (M = Fe, Co, Ni, Cu and Zn).

The carbonyl-ene reaction between encapsulated formaldehyde and propylene over the coordinatively unsaturated metal-organic frameworks M3(btc)2 (M = Fe, Co, Ni, Cu and Zn) has been investigated by means of density functional calculations. Zn3(btc)2 adsorbs formaldehyde strongest due to electron delocalization between Zn and the oxygen atom of the reactant molecule. The reaction is proposed to proceed in a single step involving proton transfer and carbon-carbon bond formation. We find the relative catalytic activity to be Zn3(btc)2 > Fe3(btc)2 ≥ Co3(btc)2 > Ni3(btc)2 > Cu3(btc)2, based on activation energy and turnover frequencies (TOF). The low activation energy for Zn3(btc)2 compared to the others can be explained by the delocalization of electron density between the carbonyl bond and the catalyst active sites, leading to a more stable transition state. The five MOFs are used to propose a descriptor for the relationship between activation energy on one side and electronic properties or adsorption energies on the other side in order to allow a quick screening of other catalytic materials for this reaction.

Furfural to Furfuryl Alcohol: Computational Study of the Hydrogen Transfer on Lewis Acidic BEA Zeolites and Effects of Cation Exchange and Tetravalent Metal Substitution.

The hydrogen transfer of furfural to furfuryl alcohol with i-propanol as the hydrogen source over cation-exchanged Lewis acidic BEA zeolite has been investigated by means of density functional calculations. The reaction proceeds in three steps. First the O-H bond of i-propanol is broken to form a propoxide intermediate. After that, the furylmethoxy intermediate is formed via hydrogen transfer process, and finally furylmethoxy abstracts the proton to form the furfuryl alcohol product. The second step is rate-determining by requiring the highest activation energy (23.8 kcal/mol) if the reaction takes place on Li-Sn-BEA zeolite. We find that the catalytic activity of various cation-exchanged Sn-BEA zeolites is in the order Li-Sn-BEA > Na-Sn-BEA > K-Sn-BEA. The lower activation energy for Li-Sn-BEA compared to Na-Sn-BEA and K-Sn-BEA can be explained by the larger charge transfer from the carbonyl bond to the catalyst, leading to its activation and to the attraction of the hydrogen being transferred. The larger charge transfer in turn is due to the smaller gap between the energies of furfural HOMO and the zeolite LUMO in Li-Sn-BEA, compared to both Na-Sn-BEA and K-Sn-BEA. In a similar way, we also compare the catalytic activity of tetravalent metal centers (Sn, Zr, and Hf) substituted into BEA and find in the order Zr ≥ Hf > Sn, based on activation energies. Finally we investigate statistically which property of the reactants is a suitable descriptor for an approximative prediction of the reaction rate in order to be able to quickly screen promising catalytic materials for this reaction.

Is acute pulmonary embolism more severe in the presence of obstructive sleep apnea? Results from an observational cohort study.

Obstructive sleep apnea (OSA) might influence disease severity in acute pulmonary embolism (PE). 253 survivors of acute PE were evaluated for sleep-disordered breathing by portable monitoring and nocturnal polysomnography. PE patients with an apnea-hypopnoea index (AHI) ≥ 15/h were significantly older (p < 0.001), had significantly impaired renal (p < 0.001) and left ventricular functions (p = 0.003), showed significantly elevated troponin I (p = 0.005) and D-dimer levels (p = 0.024), were hospitalised significantly longer (p < 0.001), and had significantly elevated PE severity scores (p = 0.015). Moderate or severe OSA was significantly (p = 0.006) more frequent among intermediate- and high-risk PE patients (81.0%) compared to the low-risk PE cohort (16.3%). Multiple logistic regression analysis revealed that PE patients in the AHI ≥ 15/h cohort were at significant risk for myocardial injury (p = 0.015). Based on clinical risk stratification models, patients with no relevant OSA syndrome tended to be at a lower risk for short-term mortality (p = 0.068). Acute PE might present more severely in OSA patients, possibly due to nocturnal hypoxemia or OSA-related hypercoagulability.