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This study investigates the representations of white ethnic identities in Non-Summit, a Korean television show, to disaggregate the generalized perception of homogenous whiteness and argue for a dialectical construction of white power and domination in Korea. Specifically, it focuses on representations of Russianness in Non-Summit in relation to the US Americanness, contextualized within post-Cold War and globalized cultural politics prevalent in Korea. Employing critical textual analysis, this study analyzes verbal and visual discourses constructing Russianness and US Americanness in Non-Summit. The findings suggest, in Non-Summit, Russianness is represented as ideologically and culturally deprived, and it appears as a dispossessed white identity that does not earn hegemony like US Americanness. At times, the marginal representations of Russianness seem to weaken the power of whiteness operating in and through the show. However, an encompassing global white supremacy remains intact when Russianness is fit into the category of whiteness through a re-whitening process. [ABSTRACT FROM AUTHOR]

Polypharmacy and its rising global prevalence is a growing public health burden. Using a large representative nationwide Korean cohort (N = 761,145), we conducted a retrospective cross-sectional study aiming to identify subpopulations of patients with polypharmacy and characterize their unique patterns through cluster analysis. Patients aged ≥ 30 years who were prescribed at least one medication between 2014 and 2018 were included in our study. Six clusters were identified: cluster 1 mostly included patients who were hospitalized for a long time (4.3 ± 5.3 days); cluster 2 consisted of patients with disabilities (100.0%) and had the highest mean number of prescription drugs (7.7 ± 2.8 medications); cluster 3 was a group of low-income patients (99.9%); cluster 4 was a group of high-income patients (80.2%) who frequently (46.4 ± 25.9 days) visited hospitals/clinics (7.3 ± 2.7 places); cluster 5 was mostly elderly (74.9 ± 9.8 years) females (80.3%); and cluster 6 comprised mostly middle-aged (56.4 ± 1.5 years) males (88.6%) (all P < 0.001). Patients in clusters 1–5 had more prescribed medications and outpatient visit days than those in cluster 6 (all P < 0.001). Given limited health care resources, individuals with any of the identified phenotypes may be preferential candidates for participation in intervention programs for optimal medication use. [ABSTRACT FROM AUTHOR]

Backgound: Central obesity in midlife is a risk factor of cognitive decline and dementia, and also one of the factors that make cognitive functions deteriorate rapidly. Objective: The objective of this study is to investigate the relationship between truncal body composition (fat and muscle) and cognitive impairment in patients with dementia. Methods: A total of 81 female over 60 years of age with probable Alzheimer's disease were recruited between November 2014 and September 2015. The Mini-Mental State Examination, Global Deterioration Scale, and Clinical Dementia Rating Scale were used to assess the cognitive functions. Both truncal fat and muscle mass were measured using body dual-energy X-ray absorptiometry and used as a percentage of body weight (TMM% and TFM%). Correlations between truncal composition and cognitive status were assessed by simple correlation analysis, which was followed by partial correlation analysis with age and educational years. Results: TFM% was not related to cognitive impairment. In contrast, TMM% had a significantly negative correlation with all three cognitive assessment scores. After further adjusting for age, educational years, and vascular factors, there was still a relationship between TMM% and cognitive functions. Conclusions: Unlike truncal fat mass that showed no relevance with cognitive functions, the truncal muscle mass was negatively correlated with cognitive status. The truncal muscle mass is thought to affect cognitive status in dementia patients somehow. [ABSTRACT FROM AUTHOR]

The stabilities of radicals play a central role in determining the thermodynamics and kinetics of many reactions in organic chemistry. In this data descriptor, we provide consistent and validated quantum chemical calculations for over 200,000 organic radical species and 40,000 associated closed-shell molecules containing C, H, N and O atoms. These data consist of optimized 3D geometries, enthalpies, Gibbs free energy, vibrational frequencies, Mulliken charges and spin densities calculated at the M06-2X/def2-TZVP level of theory, which was previously found to have a favorable trade-off between experimental accuracy and computational efficiency. We expect this data to be useful in the further development of machine learning techniques to predict reaction pathways, bond strengths, and other phenomena closely related to organic radical chemistry. Measurement(s) SMILES string • Standard Transformed Enthalpy Change • Standard Gibbs Free Energy Change • vibrational frequency • Charge • spin density • infrared spectrum • organic radical • closed-shell molecules Technology Type(s) computational modeling technique Factor Type(s) molecular structure Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.12609365 [ABSTRACT FROM AUTHOR]

Bond dissociation enthalpies (BDEs) of organic molecules play a fundamental role in determining chemical reactivity and selectivity. However, BDE computations at sufficiently high levels of quantum mechanical theory require substantial computing resources. In this paper, we develop a machine learning model capable of accurately predicting BDEs for organic molecules in a fraction of a second. We perform automated density functional theory (DFT) calculations at the M06-2X/def2-TZVP level of theory for 42,577 small organic molecules, resulting in 290,664 BDEs. A graph neural network trained on a subset of these results achieves a mean absolute error of 0.58 kcal mol−1 (vs DFT) for BDEs of unseen molecules. We further demonstrate the model on two applications: first, we rapidly and accurately predict major sites of hydrogen abstraction in the metabolism of drug-like molecules, and second, we determine the dominant molecular fragmentation pathways during soot formation. Bond dissociation enthalpies are key quantities in determining chemical reactivity, their computations with quantum mechanical methods being highly demanding. Here the authors develop a machine learning approach to calculate accurate dissociation enthalpies for organic molecules with sub-second computational cost. [ABSTRACT FROM AUTHOR]

Catalytic fast pyrolysis using the zeolite ZSM-5 is an attractive process for converting lignocellulosic biomass into fuels and chemicals. Ga-modified ZSM-5 has demonstrated improved hydrocarbon yields compared to ZSM-5 due to additional functionality imparted by Ga; however, there is little knowledge of the active Ga species and its role in the catalytic mechanisms. Here, we employ micropyrolyzer – GC-MS experiments and theoretical calculations to demonstrate that a hydrogen-pretreated Ga species (Ga*/ZSM-5) and a reductive environment are critical towards upgrading pine pyrolysis vapors into high yields of alkenes and aromatic hydrocarbons at near atmospheric pressure. The total carbon yield (g C in product per g C in pine) in alkenes and aromatic hydrocarbons under these conditions was 37% compared to 25% for the parent ZSM-5 catalyst. The corresponding carbon yield was only 19% for Ga*/ZSM-5 under inert conditions indicating that both the hydrogen-pretreated Ga* species and reducing atmosphere are required to obtain high hydrocarbon yields. The ratio of carbon in alkenes to carbon in aromatic hydrocarbons increased to 2.5 with Ga*/ZSM-5 under a reductive environment vs. 0.4 for ZSM-5. The carbon yield of alkenes increased with Ga loading; in contrast, increasing catalyst acidity promoted aromatic hydrocarbon production. Experiments conducted with isopropanol demonstrated high selectivity to propene over Ga*/ZSM-5 under reductive environments, indicating enhancement of dehydration reactions. A computational mechanism study was conducted to identify the active Ga species ([GaH2]+, [GaO]+, [Ga(OH)2]+ or [GaH(OH)]+) using the dehydration of isopropanol as a model reaction. Theoretical calculations suggested that [Ga(OH)2]+ and [GaH(OH)]+ are the most likely species responsible for dehydration with 39.7 and 38.8 kcal mol−1 activation energy barriers, respectively, and based on thermodynamic analysis, their ratio in the catalyst is dictated by H2 partial pressure and temperature. The model compound studies and computational results provide mechanistic support for the observed biomass experiments showing increased alkene selectivity. [ABSTRACT FROM AUTHOR]

9,9′‐Spirobifluorene‐based closo‐o‐carboranyl (SFC1 and SFC2) compounds and their nido‐derivatives (nido‐SFC1 and nido‐SFC2) were prepared and characterized. The two closo‐compounds displayed major absorption bands assignable to π–π* transitions involving the spirobifluorene group, as well as weak intramolecular charge‐transfer (ICT) transitions between the o‐carboranes and their spirobifluorene moieties. The nido‐compounds exhibited slightly blueshifted absorption bands resulting from the absence of the ICT transitions corresponding to the o‐carborane moieties due to the anionic character of the nido‐o‐carboranes. While SFC1 exhibited only high‐energy emissions in THF at 298 K (only from locally excited (LE) states assignable to π–π* transitions on the spirobifluorene group), remarkable emissions in the low‐energy region were observed in the rigid state such as in THF at 77 K and in the film state. SFC2 displayed intense emissions in the low‐energy region in all states. The fact that neither of the nido‐derivatives of SFC1 and SFC2 exhibited low‐energy emissions and the TD‐DFT calculation results of each closo‐compound clearly verified that the low‐energy emission was based on ICT‐based radiative decay. The conformational barriers from each relative energy calculation upon changing the dihedral angles around the o‐carborane cages for both compounds confirmed that the rotation of the o‐carborane cages and terminal phenyl rings for SFC1 is freer than that for SFC2. [ABSTRACT FROM AUTHOR]

Lignocellulosic biomass offers a renewable carbon source which can be anaerobically digested to produce short-chain carboxylic acids. Here, we assess fuel properties of oxygenates accessible from catalytic upgrading of these acids a priori for their potential to serve as diesel bioblendstocks. Ethers derived from C2 and C4 carboxylic acids are identified as advantaged fuel candidates with significantly improved ignition quality (>56% cetane number increase) and reduced sooting (>86% yield sooting index reduction) when compared to commercial petrodiesel. The prescreening process informed conversion pathway selection toward a C11 branched ether, 4-butoxyheptane, which showed promise for fuel performance and health- and safety-related attributes. A continuous, solvent-free production process was then developed using metal oxide acidic catalysts to provide improved thermal stability, water tolerance, and yields. Liter-scale production of 4- butoxyheptane enabled fuel property testing to confirm predicted fuel properties, while incorporation into petrodiesel at 20 vol % demonstrated 10% improvement in ignition quality and 20% reduction in intrinsic sooting tendency. Storage stability of the pure bioblendstock and 20 vol % blend was confirmed with a common fuel antioxidant, as was compatibility with elastomeric components within existing engine and fueling infrastructure. Technoeconomic analysis of the conversion process identified major cost drivers to guide further research and development. Life-cycle analysis determined the potential to reduce greenhouse gas emissions by 50 to 271% relative to petrodiesel, depending on treatment of coproducts. [ABSTRACT FROM AUTHOR]

Lignocellulosic biomass offers the potential to produce renewable fuels at a scale commensurate with petroleum consumption. Hybrid approaches that combine biological and chemocatalytic processes have garnered increasing attention due to their flexibility for feedstock utilization and diversity of potential products. Of note, lignocellulosic sugars can be converted biologically to short-chain carboxylic acids, while subsequent chemocatalytic upgrading can elongate the carbon backbone and remove oxygen from the structure to produce drop-in hydrocarbon fuels. However, hybrid conversion processes are typically not designed with the fuel properties in mind a priori. In this work, we apply a "fuel property first" design approach to produce a tailored hydrocarbon bioblendstock with lower intrinsic sooting and drop-in diesel fuel potential. Initially, model predictions for six fuel properties critical to diesel applications (physicochemical requirements, energy content, safety considerations, autoignition ability, and sooting tendency) were used to screen an array of hydrocarbons accessible from upgrading individual and mixed C2/C4 acids. This screening step allowed for down-selection to a non-cyclic branched C14 hydrocarbon (5-ethyl-4-propylnonane) that can be synthesized from butyric acid through sequential catalytic reactions of acid ketonization, ketone condensation, and hydrodeoxygenation. Following evaluation of each conversion step with model compounds, butyric acid was then converted through an integrated catalytic process scheme to achieve >80% overall carbon yield to a hydrocarbon mixture product containing >60% of the target C14 hydrocarbon. The potential of this conversion strategy to produce a hydrocarbon diesel bioblendstock from lignocellulosic biomass was then demonstrated using corn stover-derived butyric acid produced from Clostridium butyricum fermentation. Experimental fuel property testing of the purified C14 blendstock validated the majority of the fuel property model predictions, including <50% of the intrinsic sooting tendency when compared to conventional diesel. Meanwhile, the crude conversion product met fuel property target metrics, validating conversion process development. When the C14 bioblendstock was blended into a petroleum diesel at 20 vol%, the blend maintained low cloud point, high energy density, and cetane number. Notably, the blend reduced sooting tendency by more than 10%, highlighting the potential of the tailored bioblendstock to reduce particulate emissions. [ABSTRACT FROM AUTHOR]

2-Phenylpyridine- and 2-(benzo[b]thiophen-2-yl)pyridine-based (ppy- and btp-based) o-carboranyl (Car1 and Car2) and their B(CH3)2-C∧N-chelated (Car1B and Car2B) compounds were prepared and fully characterised by multinuclear NMR spectroscopy and elemental analysis. The solid-state structure of Car2B was determined by single-crystal X-ray diffraction, which revealed a four-coordinated dimethylboryl centre. All compounds displayed major absorption bands that were assigned to π–π* transitions involving the ppy and btp moieties, as well as weak intramolecular charge-transfer (ICT) transitions between the o-carboranes and their aryl groups. Furthermore, the chelated compounds exhibited dominant low-energy absorption bands (λabs = 333 nm for Car1B and 383 nm for Car2B) resulting from the reinforcement of ICT transitions that correspond to the o-carborane moieties through the restriction of aromatic-ring free rotation. While Car1 and Car2 did not exhibit photoluminescence emissions in toluene at 298 K, Car1B and Car2B showed intense emissions, which are assignable to π–π* transitions associated with each chelated aryl group. However, Car1 and Car2 evidently emitted at around 450 nm in solution at 77 K, invoked by radiative ICT transitions between the carborane and the ppy or btp moiety, indicating that ICT-based radiative decay is only invigorated in the rigid state in the absence of structural variations, such as C–C bond fluctuations in the carborane cage and aromatic-ring free rotation. Interestingly, while Car1 in the film state exhibited a weak ICT-based emission spectrum, and Car1B and Car2B showed intense emissions originating from π–π* transitions associated with each chelated aryl group, Car2 showed significantly enhanced emissions in the same energy region as that exhibited in solution at 77 K, resulting in a much larger quantum efficiency over that in solution. DFT-optimised structures of Car1 and Car2 in their ground and the first-excited states clearly reveal that the enhanced emissive features of Car2 in the film state are strongly associated with the retained planarity of the btp moiety in both the ground and excited states. The photophysical results for these o-carboranyl compounds definitively reveal that the planarities of the aryl groups appended to the o-carborane decisively affect the efficiency of radiative decay based on ICT involving the o-carborane. [ABSTRACT FROM AUTHOR]

This article examines the representation of Ali Abdul, the Pakistani character in the global Netflix hit Squid Game. While Ali has been celebrated for increasing South Asian representation in Korean media, we contextualize his portrayal through the lens of Korean multiculturalism. In doing so, we consider how the representation of Ali reflects the conditional acceptance of migrant men established by state-led Korean multicultural policies and politics. Through a close reading of the conditions that humanize Ali as both worthy of sympathy and unequal to his Korean counterparts, we argue that Ali's acceptance hinges upon his relation to Korean protagonists in ways that further a vision of ethnocentric nation-building through the racialization of dark-skinned masculinity. [ABSTRACT FROM AUTHOR]

An amendment to this paper has been published and can be accessed via a link at the top of the paper. [ABSTRACT FROM AUTHOR]

Catalytic fast pyrolysis (CFP) is a conversion process that integrates rapid thermochemical depolymerization of solid feedstocks with catalytic transformation to yield small molecules for fuel and chemical products. This process is well‐suited for the conversion of nonfossil feedstocks such as biomass and waste plastics, and thereby holds great potential for the production of renewable commodities. In spite of many technological developments in various aspects of CFP achieved over decades of research, this technology has yet to attain commercial success for the production of fuels and chemicals from renewable feedstocks. Effective CFP processes require careful coordination of chemical and physical phenomena that span very large length and time scales. A broad spectrum of scientific progress in both pyrolysis and catalytic upgrading has provided the foundation for successful deployment of CFP, although additional progress in process‐scale integration is yet required for commercial realization. Modeling and simulation tools provide an important framework wherein the CFP technologies by be better understood and evaluated from a holistic perspective. Here we provide a detailed description of the multiscale phenomena underlying CFP, describe challenges and associated technical progress, and suggest strategies for an integrated approach to advance this technology toward commercialization. This article is categorized under: Bioenergy > Systems and Infrastructure Bioenergy > Science and Materials [ABSTRACT FROM AUTHOR]

Lytic polysaccharide monooxygenases (LPMOs) are a group of recently discovered enzymes that play important roles in the decomposition of recalcitrant polysaccharides. Here, we report the biochemical, structural, and computational characterization of an LPMO from the white‐rot fungus Heterobasidion irregulare (HiLPMO9B). This enzyme oxidizes cellulose at the C1 carbon of glycosidic linkages. The crystal structure of HiLPMO9B was determined at 2.1 Å resolution using X‐ray crystallography. Unlike the majority of the currently available C1‐specific LPMO structures, the HiLPMO9B structure contains an extended L2 loop, connecting β‐strands β2 and β3 of the β‐sandwich structure. Molecular dynamics (MD) simulations suggest roles for both aromatic and acidic residues in the substrate binding of HiLPMO9B, with the main contribution from the residues located on the extended region of the L2 loop (Tyr20) and the LC loop (Asp205, Tyr207, and Glu210). Asp205 and Glu210 were found to be involved in the hydrogen bonding with the hydroxyl group of the C6 carbon of glucose moieties directly or via a water molecule. Two different binding orientations were observed over the course of the MD simulations. In each orientation, the active‐site copper of this LPMO preferentially skewed toward the pyranose C1 of the glycosidic linkage over the targeted glycosidic bond. This study provides additional insight into cellulose binding by C1‐specific LPMOs, giving a molecular‐level picture of active site substrate interactions. Database: The atomic coordinates and structure factors for HiLPMO9B have been deposited in the Protein Data Bank with accession code 5NNS. [ABSTRACT FROM AUTHOR]

Partial deoxygenation of bio-oil by catalytic fast pyrolysis with subsequent coupling and hydrotreating can lead to improved economics and will aid commercial deployment of pyrolytic conversion of biomass technologies. Biomass pyrolysis efficiently depolymerizes and deconstructs solid plant matter into carbonaceous molecules that, upon catalytic upgrading, can be used for fuels and chemicals. Upgrading strategies include catalytic deoxygenation of the vapors before they are condensed (in situ and ex situ catalytic fast pyrolysis), or hydrotreating following condensation of the bio-oil. In general, deoxygenation carbon efficiencies, one of the most important cost drivers, are typically higher for hydrotreating when compared to catalytic fast pyrolysis alone. However, using catalytic fast pyrolysis as the primary conversion step can benefit the entire process chain by: (1) reducing the reactivity of the bio-oil, thereby mitigating issues with aging and transport and eliminating need for multi-stage hydroprocessing configurations; (2) producing a bio-oil that can be fractionated through distillation, which could lead to more efficient use of hydrogen during hydrotreating and facilitate integration in existing petroleum refineries; and (3) allowing for the separation of the aqueous phase. In this perspective, we investigate in detail a combination of these approaches, where some oxygen is removed during catalytic fast pyrolysis and the remainder removed by downstream hydrotreating, accompanied by carbon–carbon coupling reactions in either the vapor or liquid phase to maximize carbon efficiency toward value-driven products (e.g. fuels or chemicals). The economic impact of partial deoxygenation by catalytic fast pyrolysis will be explored in the context of an integrated two-stage process. Finally, improving the overall pyrolysis-based biorefinery economics by inclusion of production of high-value co-products will be examined. [ABSTRACT FROM AUTHOR]

Body volume by three-dimensional body scanning (3DBS) may be an alternative index for evaluating body fatness. The aim of this study was to evaluate the association of body volume with body fatness and metabolic syndrome. This study included 38 Korean women whose body volume was measured using 3DBS. We measured body fatness using dual-energy X-ray absorptiometry and computed tomography. Participants with metabolic syndrome were defined as having three or more of the following components: high blood pressure (≥130/85 mmHg), elevated fasting glucose (≥100 mg/dl), hypertriglyceridemia (≥150 mg/dl), low high-density lipoprotein-cholesterol (<50 mg/dl), and abdominal obesity measured by waist circumference ≥80 cm. Total body, trunk, lower trunk, and limb volumes were significantly correlated with body mass index, waist circumference, total fat mass, percentage body fat, and abdominal fat areas. After adjustment for age, current smoking, at-risk drinking, and physical inactivity, the odds ratios (95% confidence intervals) for metabolic syndrome associated with total body, trunk, lower trunk, and limb volume were 1.08 (1.01–1.16), 1.11 (1.01–1.22), 1.20 (1.01–1.43), and 1.31 (1.04–1.66), respectively. Body volume by 3DBS was significantly associated with body fatness and metabolic syndrome. 3DBS may be a useful tool for detecting and monitoring body fatness and metabolic syndrome. [ABSTRACT FROM PUBLISHER]

LynF, an enzyme from the TruF family, O-prenylates tyrosines in proteins; subsequent Claisen rearrangements give C-prenylated tyrosine products. These reactions in tyrosines and model phenolic systems have been explored with DFT and SCS-MP2 calculations. Various ab initio benchmarks have been used (CBS-QB3, MP2, SCS-MP2) to examine the accuracy of commonly used density functionals, such as B3LYP and M06-2X. Solvent effects from water were considered by using implicit and explicit models. Studies of the ortho- C-prenylation and Claisen rearrangement of tyrosine, and the Claisen rearrangement of α,α-dimethylallyl (prenyl) coumaryl ether establish the energetics of these reactions both in the gas phase and in aqueous solution. [ABSTRACT FROM AUTHOR]

Objective: To investigate the bilateral concurrence and relationships between distolingual (DL) roots and DL canals of the mandibular first molars and second mesiobuccal (MB2) canals of the maxillary first molars using cone-beam computed tomography (CBCT). Methods: A total of 150 CBCT images showing all mandibular and maxillary first molars were retrospectively investigated in a South Korean subpopulation. The patient age, sex, positions of first molars, and presence of roots and canals were assessed. The frequency, bilateral concurrence of DL roots, DL canals, and MB2 canals, and concurrent relationship of DL roots or DL canals with MB2 canals were investigated. Data were analyzed using Fisher's exact test and odds ratios from binary logistic regression. Results: The prevalences of DL roots, DL canals, and MB2 canals were 24.7, 42.7, and 56.0 %, respectively, and showed significant bilateral concurrence. A concurrent relationship between DL roots and MB2 canals was not demonstrated, whereas the presence of a DL canal was significantly correlated with the presence of an MB2 canal on the same side. Conclusions: The presence of a DL root of the mandibular first molar, a strong ethnic characteristic, could not predict the presence of an MB2 canal of the maxillary first molar. The correlation between DL canals and MB2 canals on the same side and the significant bilateral concurrence, whether present or absent, of DL roots, DL canals, and MB2 canals can aid clinicians in the prediction of additional canals in the first molars. [ABSTRACT FROM AUTHOR]

Quality of life (QOL) is associated with body mass index (BMI). Self-awareness of false body image may influence the behavior of weight control and QOL. This study was conducted to identify the relationships between BMI and QOL, and distortion of self-estimated body image and its impact on QOL and the general health of Korean adults. A total of 229 adults who visited two university hospitals in Seoul and Chungju cities for regular health check-up responded to a questionnaire. To assess QOL, a Korean version of the obesity-related Quality of Life Scale (KOQOL) was used. The results showed that obesity-related quality of life decreased as BMI increased and as alcohol consumption became heavier. In the low weight and normal body weight groups, a portion of the groups had a more obese self-estimated body image than their actual BMI. In the overweight and obese groups, some had a leaner self-estimated body image than their actual BMI. Persons who had a self-body image of being fat had a low QOL. For Korean adults over 20 and under 65, a higher BMI is associated with a lower obesity-related quality of life. Persons who thought themselves fat had a lower QOL, regardless of their real body type. [ABSTRACT FROM AUTHOR]

9,9′-Spirobifluorene-based o-carboranyl compounds C1 and C2 were prepared and fully characterized by multinuclear nuclear magnetic resonance (NMR) spectroscopy and elemental analysis. The solid-state structure of C1 was also determined by single-crystal X-ray diffractometry. The two carboranyl compounds display major absorption bands that are assigned to π−π* transitions involving their spirobifluorene groups, as well as weak intramolecular charge-transfer (ICT) transitions between the o-carboranes and their spirobifluorene groups. While C1 only exhibited high-energy emissions (λem = ca. 350 nm) in THF at 298 K due to locally excited (LE) states assignable to π−π* transitions involving the spirobifluorene group alone, a remarkable emission in the low-energy region was observed in the rigid state, such as in THF at 77 K or the film state. Furthermore, C2 displays intense dual emissive patterns in both high- and low-energy regions in all states. Electronic transitions that were calculated by time-dependent-DFT (TD-DFT) for each compound based on ground (S0) and first-excited (S1) state optimized structures clearly verify that the low-energy emissions are due to ICT-based radiative decays. Calculated energy barriers that are based on the relative energies associated with changes in the dihedral angle around the o-carborane cages in C1 and C2 clearly reveal that the o-carborane cage in C1 rotates more freely than that in C2. All of the molecular features indicate that ICT-based radiative decay is only available to the rigid state in the absence of structural fluctuations, in particular the free-rotation of the o-carborane cage. [ABSTRACT FROM AUTHOR]

In the upgrading of biomass pyrolysis vapors to hydrocarbons, dehydration accomplishes a primary objective of removing oxygen, and acidic zeolites represent promising catalysts for the dehydration reaction. Here, we utilized density functional theory calculations to estimate adsorption energetics and intrinsic kinetics of alcohol dehydration over H-ZSM-5, H-BEA, and H-AEL zeolites. The ONIOM (our Own N-layered Integrated molecular Orbital and molecular Mechanics) calculations of adsorption energies were observed to be inconsistent when benchmarked against QM (Quantum Mechanical)/Hartree–Fock and periodic boundary condition calculations. However, reaction coordinate calculations of adsorbed species and transition states were consistent across all levels considered. Comparison of ethanol, isopropanol (IPA), and tert-amyl alcohol (TAA) over these three zeolites allowed for a detailed examination of how confinement impacts on reaction mechanisms and kinetics. The TAA, seen to proceed via a carbocationic mechanism, was found to have the lowest activation barrier, followed by IPA and then ethanol, both of which dehydrate via a concerted mechanism. Barriers in H-BEA were consistently found to be lower than in H-ZSM-5 and H-AEL, attributed to late transition states and either elevated strain or inaccurately estimating long-range electrostatic interactions in H-AEL, respectively. Molecular dynamics simulations revealed that the diffusivity of these three alcohols in H-ZSM-5 were significantly overestimated by Knudsen diffusion, which will complicate experimental efforts to develop a kinetic model for catalytic fast pyrolysis. [ABSTRACT FROM AUTHOR]

Herein, we investigated the effect of ring planarity by fully characterizing four pyridine-based o-carboranyl compounds. o-Carborane was introduced to the C4 position of the pyridine rings of 2-phenylpyridine and 2-(benzo[b]thiophen-2-yl)pyridine (CB1 and CB2, respectively), and the compounds were subsequently borylated to obtain the corresponding C∧N-chelated compounds CB1B and CB2B. Single-crystal X-ray diffraction analysis of the molecular structures of CB2 and CB2B confirmed that o-carborane is appended to the aryl moiety. In photoluminescence experiments, CB2, but not CB1, showed an intense emission, assignable to intramolecular charge transfer (ICT) transition between the aryl and o-carborane moieties, in both solution and film states. On the other hand, in both solution and film states, CB1B and CB2B demonstrated a strong emission, originating from π-π * transition in the aryl groups, that tailed off to 650 nm owing to the ICT transition. All intramolecular electronic transitions in these o-carboranyl compounds were verified by theoretical calculations. These results distinctly suggest that the planarity of the aryl groups have a decisive effect on the efficiency of the radiative decay due to the ICT transition. [ABSTRACT FROM AUTHOR]

Biological routes to the production of fuels from renewable feedstocks hold significant promise in our efforts towards a sustainable future. The fatty acid decarboxylase enzyme (OleTJE) is a cytochrome P450 enzyme that converts long and medium chain fatty acids to terminal alkenes and shares significant similarities in terms of structure, substrate scope and mechanism with the hydroxylase cytochrome P450 (P450BSβ). Recent reports have demonstrated that catalytic pathways in these enzymes bifurcate when the heme is in its iron-hydroxo (compound II) state. In spite of significant similarities, the fundamental underpinnings of their different characteristic wild-type reactivities remain ambiguous. Here, we develop point charges, modified parameters and report molecular simulations of this crucial intermediate step. Water occupancies and substrate mobility at the active site are observed to be vital differentiating aspects between the two enzymes in the compound II state and corroborate recent experimental hypotheses. Apart from increased substrate mobility in the hydroxylase, which could have implications for enabling the rebound mechanism for hydroxylation, OleTJE is characterized by much stronger binding of the substrate carboxylate group to the active site arginine, implicating it as an important enabling actor for decarboxylation. [ABSTRACT FROM AUTHOR]