Oxygen Healing and CO2 /H2 /Anisole Dissociation on Reduced Molybdenum Oxide Surfaces Studied by Density Functional Theory.

Reduced molybdenum oxides are versatile catalysts for deoxygenation and hydrodeoxygenation reactions. In this work, we have performed spin-polarized DFT calculations to investigate oxygen healing energies on reduced molybdenum oxides (reduced α-MoO3 , γ-Mo4 O11 and MoO2 ). We find that Mo+4 on MoO2 (100) is the most active for abstracting an oxygen from the oxygenated compounds. We further explored CO2 adsorption and dissociation on reduced α-MoO3 (010) and MoO2 (100). In comparison to reduced α-MoO3 (010), CO2 adsorbs more strongly on MoO2 (100). We find that CO2 dissociates on MoO2 (100) via a two-step process, the overall barrier for which is 0.6 eV. This barrier is 1.7 eV lower than that on reduced α-MoO3 (010), suggesting a much higher activity for deoxygenation of CO2 to CO. As H2 dissociation is shown to be the rate-limiting step for hydrodeoxygenation reactions, we also studied activation barriers for H2 chemisorption on MoO2 (100). We find that the chemisorption barriers are 0.7 eV lower than that reported on reduced α-MoO3 (010). Finally, we have studied the dissociation (C-O cleavage) of anisole (a lignin-based biofuel model compound) on MoO2 (100). We find that anisole binds very strongly on MoO2 (100) with an adsorption energy of -1.47 eV. According to Sabatier's principle, strongly adsorbing reactants poison the catalyst surface, which may explain the low activity of MoO2 observed during experiments for hydrodeoxygenation of anisole.

Azomethine ylide cycloaddition of 1,3-dienyl esters: highly regio- and diastereoselective synthesis of functionalized pyrrolidinochromenes.

An efficient protocol for the synthesis of tricyclic pyrrolidinochromenes has been developed via an intramolecular 1,3-dipolar cycloaddition of azomethine ylides generated in situ from 1,3-dienyl ester tethered O-hydroxyarylaldehyde and glycine esters. The reaction is highly regio- and diastereoselective in nature and provided the potentially bioactive pyrrolidine fused tricyclic cycloadducts in excellent yields with wide substrate scope. Interestingly this reaction constructs two rings and four contiguous stereogenic centers in which one of them is an all carbon quaternary center in a unique fashion.

Nascent Decomposition Pathways of CH4 Pyrolysis in Gas-Phase Metal Halides.

We have performed a combined quantum mechanical and microkinetic modeling study to understand the nascent decomposition pathways of methane pyrolysis, catalyzed by gas-phase ZnCl2, in a constant pressure batch reactor at 1273 K. We find that ZnCl2 catalyzes methane pyrolysis with an apparent activation energy of 227 kJ/mol. We have also performed sensitivity analysis on a reaction network comprising initiation, termination, and primary propagation reactions. The results suggest that the whole reaction network can be simplified to four reactions, which contributes to the initial rate of methane decomposition. Based on these insights, we have also explored the catalyzing effects of gas-phase AlCl3, CoCl2, CuCl2, FeCl2, and NiCl2 for methane decomposition. Our calculations suggest that gas-phase CuCl2 and NiCl2 are the most active catalysts among the metal halides studied in this work.

Domino ring opening and selective O/S-alkylation of cyclic ethers and thioethers.

Chemoselective domino ring opening and selective O/S-alkylation of ethers/thioethers over enol C/O alkylation has been observed. Various 2-aryl chromanones/thiochromanones with alkyl/allyl bromides were smoothly converted into the corresponding highly functionalized ethers and thioethers in excellent yields with high selectivity. An unusual, chemoselective domino ring opening and selective ether/thioether O/S-alkylation over. An unusual, chemoselective domino ring opening and selective ether/thioether O/S alkylation over enol C/O alkylation has been observed.

Rhodium-Catalyzed Diastereoselective [3 + 2] Cycloaddition of Carbonyl Ylide: An Access to the Core Ring System of Cordigol and Lophirone H.

This paper describes a new synthetic strategy for the construction of tricyclic chromeno/quinolino furan frameworks via creation of two new rings and three contiguous stereogenic centers with high diastereoselectivity through a rhodium-catalyzed intramolecular carbonyl ylide cycloaddition reaction for the first time. This protocol allows the synthesis of the core ring system of natural products such as cordigol and lophirone H.

Dermatological findings in SARS-CoV-2 positive patients: An observational study from North India.

A novel coronavirus (severe acute respiratory syndrome corononavirus-2; SARS-CoV-2) has affected millions of people across the world. The coronavirus disease (COVID-19) resulting from SARS-CoV-2 manifests in variable clinical severity, featuring both respiratory and extra-respiratory symptoms. Dermatological manifestations of COVID-19 are sparsely reported. To study the various dermatological findings in SARS-CoV-2 positive patients in Indian population. Institutional ethical committee permission was sought and102 SARS-CoV-2 positive patients were included in the study. A thorough clinical examination was done to determine the nature and frequency of various dermatological manifestations in these patients. Out of the 102 positive cases, 95 were males. The mean age of the group was 39.30 years. Thirteen patients (12.7%) were found to have dermatological manifestations. Three (2.9%) had maculopapular rash, two (1.9%) had urticarial lesions and eight (7.8%) patients had itching without any specific cutaneous signs. Trunk was the most frequently affected area, followed by the extremities. No mucosal signs and symptoms were detected. Dermatological manifestations were seen in a small group of COVID-19 patients. The presentation may vary in different population groups and based on severity of disease.

Palladium catalyzed chemo- and site-selective C-H acetoxylation and hydroxylation of oxobenzoxazine derivatives.

An efficient protocol for the introduction of acetoxy and hydroxy functionalities on unactivated aryl sp2 carbons of oxobenzoxazine derivatives via an ortho-C-H activation reaction using a palladium catalyst has been developed for the first time. Interestingly, this intermolecular C-H functionalization reaction takes place in a facile and simple manner with high chemo- and site selectivity.

Rates of adsorption and desorption: Entropic contributions and errors due to mean-field approximations.

We have performed exact classical rate calculations to compute adsorption and desorption rate constants with a model representative of a real system. We compute the desorption rate using transition-state theory by taking the dividing-surface far from the surface of the solid. We find that using a mean-field assumption, i.e., applying potential of mean force to transition state theory, could lead to two orders-of-magnitude errors in the rate constant owing to large fluctuations in the desorption barrier. Furthermore, we compute the adsorption rate by including a dynamical factor which reflects the probability of sticking to the solid surface. We find that the sticking probability is highly sensitive to the coverage. Also, we find that the adsorption rate computed from the mean-field assumption is not very different from the exact adsorption rate. We also compute entropic contribution to desorption rates and compare it to that obtained from two limiting models of adsorption-2D ideal gas and 2D ideal lattice gas. We show that at high temperatures (700 K), the entropic contribution to desorption rates computed from the exact calculations is very close to that obtained from the 2D ideal gas model. However, for lower to intermediate temperatures from 200 K to 500 K, the entropic contributions cover a wide range which lies in between the two limiting models and could lead to over two-orders-of-magnitude errors in the rate coefficient.

Monolithic optical link in silicon-on-insulator CMOS technology.

This work presents a monolithic laterally-coupled wide-spectrum (350 nm < λ < 1270 nm) optical link in a silicon-on-insulator CMOS technology. The link consists of a silicon (Si) light-emitting diode (LED) as the optical source and a Si photodiode (PD) as the detector; both realized by vertical abrupt n+p junctions, separated by a shallow trench isolation composed of silicon dioxide. Medium trench isolation around the devices along with the buried oxide layer provides galvanic isolation. Optical coupling in both avalanche-mode and forward-mode operation of the LED are analyzed for various designs and bias conditions. From both DC and pulsed transient measurements, it is further shown that heating in the avalanche-mode LED leads to a slow thermal coupling to the PD with time constants in the ms range. An integrated heat sink in the same technology leads to a ∼ 6 times reduction in the change in PD junction temperature per unit electrical power dissipated in the avalanche-mode LED. The analysis paves way for wide-spectrum optical links integrated in smart power technologies.

Low power wide spectrum optical transmitter using avalanche mode LEDs in SOI CMOS technology.

This paper presents a low power monolithically integrated optical transmitter with avalanche mode light emitting diodes in a 140 nm silicon-on-insulator CMOS technology. Avalanche mode LEDs in silicon exhibit wide-spectrum electroluminescence (400 nm < λ < 850 nm), which has a significant overlap with the responsivity of silicon photodiodes. This enables monolithic CMOS integration of optocouplers, for e.g. smart power applications requiring high data rate communication with a large galvanic isolation. To ensure a certain minimum number of photons per data pulse (or per bit), light emitting diode drivers must be robust against process, operating conditions and temperature variations of the light emitting diode. Combined with the avalanche mode light emitting diode's steep current-voltage curve at relatively high breakdown voltages, this conventionally results in high power consumption and significant heating. The presented transmitter circuit is intrinsically robust against these issues, thereby enabling low power operation.

Patient Radiation Dose Reduction during Transarterial Chemoembolization Using a Novel X-Ray Imaging Platform.

PURPOSE: To evaluate radiation dose reduction in patients undergoing transarterial chemoembolization with the use of a new image acquisition and processing platform. MATERIALS AND METHODS: Radiation-dose data were obtained from 176 consecutive chemoembolization procedures in 135 patients performed in a single angiography suite. From January 2013 through October 2013, 85 procedures were performed by using our institution's standard fluoroscopic settings. After upgrading the x-ray fluoroscopy system with an image acquisition and processing platform designed to reduce image noise and reduce skin entrance dose, 91 chemoembolization procedures were performed from November 2013 through December 2014. Cumulative dose-area product (CDAP), cumulative air kerma (CAK), and total fluoroscopy time were recorded for each procedure. Image quality was assessed by three interventional radiologists blinded to the x-ray acquisition platform used. RESULTS: Patient radiation dose indicators were significantly lower for chemoembolization procedures performed with the novel imaging platform. Mean CDAP decreased from 3,033.2 dGy·cm(2) (range, 600.3-9,404.1 dGy·cm(2)) to 1,640.1 dGy·cm(2) (range, 278.6-6,779.9 dGy·cm(2); 45.9% reduction; P < .00001). Mean CAK decreased from 1,445.4 mGy (range, 303.6-5,233.7 mGy) to 971.7 mGy (range, 144.2-3,512.0 mGy; 32.8% reduction; P < .0001). A 20.3% increase in mean total fluoroscopy time was noted after upgrading the imaging platform, but blinded analysis of the image quality revealed no significant degradation. CONCLUSIONS: Although a small increase in fluoroscopy time was observed, a significant reduction in patient radiation dose was achieved by using the optimized imaging platform, without image quality degradation.

The inferior emissary vein: a reliable landmark for right adrenal vein sampling.

BACKGROUND: Right adrenal vein (RAV) catheterization can be a very challenging step in adrenal venous sampling (AVS). Visualization of the inferior emissary vein (IEV) may be an indication of successful RAV catheterization. PURPOSE: To compare the rate of successful RAV sampling in the presence of the IEV. MATERIAL AND METHODS: Retrospective review of all consecutive patients with PA who underwent AVS between April 2009 and April 2012 was performed. A total of 30 patients were identified. Procedural images, cortisol, and aldosterone values obtained from sampling of the RAV and inferior vena cava (IVC) were reviewed. Cortisol measurements obtained from RAV samples were divided by measurements from the infra-renal IVC blood samples in order to calculate the selectivity index (SI). An SI >3 was considered indicative of technically successful RAV sampling. RESULTS: RAV sampling was considered technically successful in 29 out of 30 cases (97%). In cases of successful RAV sampling (29 patients), the IEV was identified in 25 patients (86%). The IEV was visualized in isolation in 16 patients (64%), and in conjunction with visualization of the RAV or right adrenal gland stain in nine patients (36%). The IEV was not visualized in the one case of unsuccessful RAV sampling. Visualizing the IEV had a sensitivity of 86.2% for successful RAV sampling. CONCLUSION: The IEV may serve as a reliable landmark for the RAV during RAV sampling.

Nucleation near the eutectic point in a Potts-lattice gas model.

We use the Potts-lattice gas model to study nucleation at and near the eutectic composition. We use rare-event methods to compute the free energy landscape for the competing nucleation products, and short trajectories at the barrier top to obtain prefactors. We introduce a procedure to tune the frequency of semigrand Monte Carlo moves so that the dynamics of a small closed system roughly resemble those of an infinite system. The non-dimensionalized nucleation rates follow trends as predicted by the classical nucleation theory. Finally, we develop corrections that convert free energy surfaces from closed (canonical) simulations into free energy surfaces from open (semigrand) simulations. The new corrections extend earlier corrections to now address situations like nucleation at the eutectic point where two products nucleate competitively.

Oncocytic adrenal cortical adenoma: a benign lesion mimicking malignancy.

Adrenocortical tumours are rare in children and account for only 0.3%-0.4% of all neoplasms in childhood. They present with variable signs and symptoms, depending on the type of hormonal hypersecretion. The majority of the adrenocortical tumours in children are functional (90%) and malignant (88%). Here, we describe a functional plurihormonal oncocytic adrenal cortical adenoma in a young girl, that mimicked a malignant adrenal lesion, clinically as well as on imaging and biochemical features. This report bears the objective of being aware of the atypical biochemical as well as imaging characteristics of oncocytic adrenal tumours.

Ab initio dynamics of cellulose pyrolysis: nascent decomposition pathways at 327 and 600 °C.

We modeled nascent decomposition processes in cellulose pyrolysis at 327 and 600 °C using Car-Parrinello molecular dynamics (CPMD) simulations with rare events accelerated with the metadynamics method. We used a simulation cell comprised of two unit cells of cellulose Iß periodically repeated in three dimensions to mimic the solid cellulose. To obtain initial conditions at reasonable densities, we extracted coordinates from larger classical NPT simulations at the target temperatures. CPMD-metadynamics implemented with various sets of collective variables, such as coordination numbers of the glycosidic oxygen, yielded a variety of chemical reactions such as depolymerization, fragmentation, ring opening, and ring contraction. These reactions yielded precursors to levoglucosan (LGA)-the major product of pyrolysis-and also to minor products such as 5-hydroxy-methylfurfural (HMF) and formic acid. At 327 °C, we found that depolymerization via ring contraction of the glucopyranose ring to the glucofuranose ring occurs with the lowest free-energy barrier (20 kcal/mol). We suggest that this process is key for formation of liquid intermediate cellulose, observed experimentally above 260 °C. At 600 °C, we found that a precursor to LGA (pre-LGA) forms with a free-energy barrier of 36 kcal/mol via an intermediate/transition state stabilized by anchimeric assistance and hydrogen bonding. Conformational freedom provided by expansion of the cellulose matrix at 600 °C was found to be crucial for formation of pre-LGA. We performed several comparison calculations to gauge the accuracy of CPMD-metadynamics barriers with respect to basis set and level of theory. We found that free-energy barriers at 600 °C are in the order pre-LGA < pre-HMF < formic acid, explaining why LGA is the kinetically favored product of fast cellulose pyrolysis.

Ester-directed orthogonal dual C-H activation and ortho aryl C-H alkenylation via distal weak coordination.

An unprecedented orthogonal cross-coupling between aromatic C(sp2) and aliphatic olefinic C(sp2) carbons of two same molecules via dual C-H bond activation in an intermolecular fashion has been developed using a distal ester-directing group. This new coupling reaction led to the synthesis of the highly functionalized 1,3-diaryl molecular architecture in very good yields and with high chemo- and regioselectivities. In addition, using ester as the distal directing group, ortho C-H olefination of α-methyl aryl acrylates and cinnamic esters with various alkenes has been achieved in very good yields and with a wide range of substrate scope.

Simulating infrared spectra and hydrogen bonding in cellulose Iß at elevated temperatures.

We have modeled the transformation of cellulose Iß to a high temperature (550 K) structure, which is considered to be the first step in cellulose pyrolysis. We have performed molecular dynamics simulations at constant pressure using the GROMOS 45a4 united atom forcefield. To test the forcefield, we computed the density, thermal expansion coefficient, total dipole moment, and dielectric constant of cellulose Iß, finding broad agreement with experimental results. We computed infrared (IR) spectra of cellulose Iß over the range 300-550 K as a probe of hydrogen bonding. Computed IR spectra were found to agree semi-quantitatively with experiment, especially in the O-H stretching region. We assigned O-H stretches using a novel synthesis of normal mode analysis and power spectrum methods. Simulated IR spectra at elevated temperatures suggest a structural transformation above 450 K, a result in agreement with experimental IR results. The low-temperature (300-400 K) structure of cellulose Iß is dominated by intrachain hydrogen bonds, whereas in the high-temperature structure (450-550 K), many of these transform to longer, weaker interchain hydrogen bonds. A three-dimensional hydrogen bonding network emerges at high temperatures due to formation of new interchain hydrogen bonds, which may explain the stability of the cellulose structure at such high temperatures.

Spectroscopic signatures of nitrogen-substituted zeolites.

Nanoporous acid catalysts such as zeolites form the backbone of catalytic technologies for refining petroleum. With the promise of a biomass economy, new catalyst systems will have to be discovered, making shape-selective base catalysts especially important because of the high oxygen content in biomass-derived feedstocks. Strongly basic zeolites are attractive candidates, but such materials are notoriously difficult to make due to the strong inherent acidity of aluminosilicates. Several research groups have endeavored to produce strongly basic zeolites by treating zeolites with amines, but to date there is no compelling evidence that nitrogen is incorporated into zeolite frameworks. In this communication, we detail synthesis, NMR spectroscopy, and quantum mechanical calculations showing that nitrogen adds onto both surface and interior sites while preserving the framework structure of zeolites. This finding is crucial for the rational design of new biomass-refinement catalysts, allowing 50 years of zeolite science to be brought to bear on the catalytic synthesis of biofuels.

Optic nerve avulsion associated with central retinal artery occlusion following rotational globe injury.

Avulsion of the optic nerve head is a rare and severe complication of ocular blunt trauma. Herein, we describe a case of 16-year-old boy, who presented with a rare combination of optic nerve avulsion associated with central retinal artery occlusion, following blunt trauma with a leather ball. This report highlights the potential blinding complication following rotational injury.