Chemistry of enediynyl azides: activation through a novel pathway

The spontaneous activation of a nonaromatic enediynyl azide under ambient conditions has been demonstrated. The aromatic enediyne followed the expected cycloaddition with the alkene in the neighbouring arm to form a stable bridged bicyclic enediyne

Mortality and pulmonary complications in patients undergoing surgery with perioperative SARS-CoV-2 infection: an international cohort study

Background: The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on postoperative recovery needs to be understood to inform clinical decision making during and after the COVID-19 pandemic. This study reports 30-day mortality and pulmonary complication rates in patients with perioperative SARS-CoV-2 infection. Methods: This international, multicentre, cohort study at 235 hospitals in 24 countries included all patients undergoing surgery who had SARS-CoV-2 infection confirmed within 7 days before or 30 days after surgery. The primary outcome measure was 30-day postoperative mortality and was assessed in all enrolled patients. The main secondary outcome measure was pulmonary complications, defined as pneumonia, acute respiratory distress syndrome, or unexpected postoperative ventilation. Findings: This analysis includes 1128 patients who had surgery between Jan 1 and March 31, 2020, of whom 835 (74·0%) had emergency surgery and 280 (24·8%) had elective surgery. SARS-CoV-2 infection was confirmed preoperatively in 294 (26·1%) patients. 30-day mortality was 23·8% (268 of 1128). Pulmonary complications occurred in 577 (51·2%) of 1128 patients; 30-day mortality in these patients was 38·0% (219 of 577), accounting for 81·7% (219 of 268) of all deaths. In adjusted analyses, 30-day mortality was associated with male sex (odds ratio 1·75 [95% CI 1·28–2·40], p\textless0·0001), age 70 years or older versus younger than 70 years (2·30 [1·65–3·22], p\textless0·0001), American Society of Anesthesiologists grades 3–5 versus grades 1–2 (2·35 [1·57–3·53], p\textless0·0001), malignant versus benign or obstetric diagnosis (1·55 [1·01–2·39], p=0·046), emergency versus elective surgery (1·67 [1·06–2·63], p=0·026), and major versus minor surgery (1·52 [1·01–2·31], p=0·047). Interpretation: Postoperative pulmonary complications occur in half of patients with perioperative SARS-CoV-2 infection and are associated with high mortality. Thresholds for surgery during the COVID-19 pandemic should be higher than during normal practice, particularly in men aged 70 years and older. Consideration should be given for postponing non-urgent procedures and promoting non-operative treatment to delay or avoid the need for surgery. Funding: National Institute for Health Research (NIHR), Association of Coloproctology of Great Britain and Ireland, Bowel and Cancer Research, Bowel Disease Research Foundation, Association of Upper Gastrointestinal Surgeons, British Association of Surgical Oncology, British Gynaecological Cancer Society, European Society of Coloproctology, NIHR Academy, Sarcoma UK, Vascular Society for Great Britain and Ireland, and Yorkshire Cancer Research

Theory of anomalous diffusive reaction rates on realistic self-affine fractals

We developed a theoretical method based on limited scale power law form of the interfacial roughness power spectrum and the solution of diffusion equation under the diffusion-limited boundary conditions on rough interfaces. This theoretical method is useful for the analysis of diffusion-limited flux/current to limited scale self-affine random fractal interfaces and is compared with experimentally measured electrochemical current for nano- and micron scales of roughness. The new result explains experimental findings of the temporal scale invariance as well as deviation from this in transition, short, and long time regions. Our result show flux/current transients in terms of three dominant fractal morphological parameters, that is, fractal dimension, lower cutoff length scale of fractality, and topothesy, for the limited length scales of fractality. More broadly, these results are applicable for all time scales and roughness factors

Theory of partial diffusion-limited interfacial transfer/reaction on realistic fractals

The problems of diffusive transport to and across an irregular interface are of general interest, but are considered a difficult class of problems for theoretical understanding. In this paper we discuss theory of partial diffusion-limited interfacial transfer/reaction on a realistic fractal interface. The surface irregularity is modeled as a random surface fractal, which is characterized by statistically isotropic self-affine fractals on limited length scales. The power spectrum of roughness of such surface fractal is approximated in terms of power law function for the intermediate wave-numbers (or spatial frequency components in roughness). This description of roughness consists of four fractal morphological characteristic features. Results unravel the connection between the flux/current, surface morphology and its kinetics following a step of surface activity (like a potential step experiment). We show the dependence of reaction flux/current on various fractal roughness characteristics related to power spectrum, and discuss the dynamic crossover of charge transfer controlled regime to fractal morphology controlled diffusion regime to classical inverse square root of time regime

Theory of potentiostatic current transients for coupled catalytic reaction at random corrugated fractal electrode

We developed a mathematical model for the first order homogeneous catalytic chemical reaction coupled with an electron transfer (EC′) on a rough working electrode. Results are obtained for the various roughness models of electrode corrugations, viz., (i) roughness as an exact periodic function, (ii) roughness as a random function with known statistical properties, and (iii) roughness as a random function with statistical self-affine fractality over a finite range of length scales. Method of Green's function is used in the formulation to obtain second-order perturbation (in roughness profile) expressions for the concentration, the local current density and the current transients. A general operator structure between these quantities and arbitrary roughness profile is emphasized. The statistically averaged (randomly rough) electrode response is obtained by an ensemble averaging over all possible surface configurations. An elegant mathematical formula between the average electrochemical current transient and surface structure factor or power-spectrum of roughness is obtained. This formula is used to obtain an explicit equation for the current on an approximately self-affine (or realistic) fractal electrode with a limited range of length scales of irregularities. This description of realistic fractal is obtained by cutoff power law power-spectrum of roughness. The realistic fractal power-spectrum consists of four physical characteristics, viz., the fractal dimension (D_H), lower (ℓ) and upper (L) cutoff length scales of fractality and a proportionality factor (μ), which is related to the topothesy or strength of fractality. Numerical calculations are performed on final results to understand the effect of catalytic reaction and fractal morphological characteristics on potentiostatic current transients

Pulse Electrodeposited AuWO3 Catalyst from a WaterIonic Liquid Microemulsion for Photoaccelerated Methanol Electrooxidation

For improving the separation efficiency of photogenerated carriers and electrocatalytic activity, we have used visible light-responsive tungsten oxide (WO3) as a support for a plasmonic gold nanoparticle (Au NP) cocatalyst. It has been fabricated by a two-step optimized pulse electrodeposition method in aqueous and water-in-ionic liquid microemulsion media. By taking advantage of interfacial heterojunctions and the synergistic effect, the plasmonic Au NP electrocatalyst on WO3-coated fluorine-doped tin oxide as a photoanode has shown enhanced electrocatalytic current density as well as a negative shift in the onset potential under light irradiation for methanol electrooxidation. The pulse electrodeposited Au–WO3 nanocatalyst under light irradiation displays ∼3.85 times enhancement in electrocatalytic activity than without light irradiation, and it has been attributed to the simultaneous enhancement in electron–hole (e–/h+) pair separation of WO3 and Au NP surface plasmon resonance absorption. The mechanism of enhanced electrocatalytic performance of Au–WO3 has also been proposed under light illumination

Antioxidant activity and electrochemical elucidation of the enigmatic redox behavior of curcumin and its structurally modified analogues

Here, we report studies on the antioxidant activity and redox behavior of curcumin and its structurally modified synthetic analogues. We have synthesized a number of analogues of curcumin which abrogate its keto-enol tautomerism or substitute the methylene group at the centre of its heptadione moiety implicated in the hydride transfer and studied their redox property. From cyclic voltammetric studies, it is demonstrated that H-atom transfer from CH2 group at the center of the heptadione link also plays an important role in the antioxidant properties of curcumin along with that of its phenolic -OH group. In addition, we also show that the conversion of 1, 3-dicarbonyl moiety of curcumin to an isosteric heterocycle as in pyrazole curcumin, which decreases its rotational freedom, leads to an improvement of its redox properties as well as its antioxidant activity. (C) 2014 Elsevier Ltd. All rights reserved

Diffusion-controlled potentiostatic current transients on realistic fractal electrodes

We analyze the problem of diffusion to irregular electrode whose irregularity is characterized as statistically isotropic self-affine fractals on limited length scales. The power spectrum of a surface fractal is approximated in terms of a white noise for low wave-numbers and a power law function for the intermediate wave-numbers. This power spectrum has four fractal morphological parameters. They are fractal dimension (D_H), lower (ℓ) and upper (L) cutoff length scales of fractality, and the proportionality factor (μ) related to topothesy or strength of roughness. Our explicit results for the potentiostatic current transient and its limiting laws are presented. These limiting laws are: (i) short time expansion, (ii) long time expansion and (iii) intermediate time expansion. The intermediate time limiting law for the current transient captures the classical anomalous power law behavior which is usually observed in experimental data. Our results show that the scaling exponent of anomalous region is dependent on D_H as well as on ℓ and μ. These results also unravel the connection between the crossover times and the roughness characteristics of realistic fractal surfaces. We demonstrate an excellent comparison between the theoretical results and the experimental potentiostatic current transient. Finally, we also show the localization of current density on a rough corrugated electrode where surface corrugation is taken as a band-limited Weierstrass–Mandelbrot random function

Reduced graphene oxide-supported nickel oxide catalyst with improved CO tolerance for formic acid electrooxidation

The superior catalytic activity along with improved CO tolerance for formic acid electro-oxidation has been demonstrated on a NiO-decorated reduced graphene oxide (rGO) catalyst. The cyclic voltammetry response of rGO-NiO/Pt catalyst elucidates improved CO tolerance and follows direct oxidation pathway. It is probably due to the beneficial effect of residual oxygen groups on rGO support which is supported by FT-IR spectrum. A strong interaction of rGO support with NiO nanoparticles facilitates the removal of CO from the catalyst surface. The chronoamperometric response indicates a higher catalytic activity and stability of rGO-NiO/Pt catalyst than the NiO/Pt and unmodified Pt electrode catalyst for a prolonged time of continuous oxidation of formic acid. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved