bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nitrene Insertion into Aromatic and Benzylic C−H Bonds Catalyzed by Copper Complexes of Fluorinated Bis‐ and Tris(pyrazolyl)borates
Authors: Ponduru Tharun T. , Sun Zhicheng , Cundari Thomas R. , Rasika Dias H. V. 
Published: July 2019

AbstractFluorinated bis‐ and tris(pyrazolyl)boratocopper complexes catalyze the nitrene insertion to C−H bonds of aromatic hydrocarbons efficiently producing amination products in good to excellent yields at room temperature. Imidoiodanes, PhI=NTs (Ts=p‐toluenesulfonyl) and PhI=NNs (Ns=p‐nitrophenylsulfonyl) serve as the nitrene source. The bis(pyrazolyl)borate catalyst [H2B(3,5‐(CF3)2Pz)2]Cu(NCMe) with PhI=NNs produced the arene C−H functionalized product of mesitylene in 87 % yield with only trace amounts of benzylic C−H insertion. The use of [H2B(3,5‐(CF3)2‐4‐(NO2)Pz)2]Cu(NCMe) that has an even weakly donating pyrazolate generated the arene C−H insertion product exclusively. The tris(pyrazolyl)borate complex [HB(3,5‐(CF3)2Pz)3]Cu(NCMe), in contrast, generated the benzylic amination product from mesitylene and PhI=NNs in 82 % yield with only very minor amounts of arene C−H functionalization. DFT calculations suggest that Cu‐nitrene moiety generated from [HB(3,5‐(CF3)2Pz)3]Cu(NCMe) and PhI=NNs activates the benzylic C−H bond of mesitylene via a hydrogen atom abstraction (HAA) followed by a radical rebound (RR) pathway, whereas the functionalization of sp2 C−H bonds of mesitylene by [H2B(3,5‐(CF3)2Pz)2]Cu(NNs) ensues possibly via a nitrene addition to the arene core.
Continuous Hydrogenation of Carbon Dioxide to Formic Acid and Methyl Formate by a Molecular Iridium Complex Stably Heterogenized on a Covalent Triazine Framework
Authors: Corral‐Pérez Juan José , Billings Amelia , Stoian Dragos , Urakawa Atsushi 
Published: July 2019

AbstractContinuous synthesis of formic acid and methyl formate via CO2 hydrogenation is demonstrated using a molecular iridium complex stably immobilized on a solid covalent triazine framework (CTF) under high‐pressure conditions. Compared to formic acid synthesis, methyl formate synthesis is advantageous to enhance the selectivity and yield of formates under kinetically favorable high temperature conditions. Transient in situ vibrational spectroscopy shows that the CTF strongly interacts with CO2 and H2, and even activates methanol. Hence, CTF is a promising support for molecular catalysts, even under harsh supercritical and flow conditions, through its strong binding capability.
Alkali‐Driven Assembly of Protein‐Rich Biomass Boosts the Electrocatalytic Activity of the Derived Carbon Materials for Oxygen Reduction
Authors: Liang Kaixin , Xu Ying , Wang Liqiang , Liu Youcai , Liu You‐Nian 
Published: July 2019

AbstractThough of great significance, it is still a challenge to facilely engineer biomass into heteroatom‐doped porous carbon materials (HPCs)‐based electrocatalysts with high activity and durability to replace Pt‐based ones for oxygen reduction reaction (ORR). Herein, alkali‐driven assembly strategy is proposed to boost the ORR catalytic performance of the HPCs derived from protein‐rich biomass. Egg white for instance, can self‐assemble into a hydrogel with 3D networks in the presence of alkali. The formed hydrogel can work as a self‐heteroatom (N, S) doped and self‐activated precursor for fabricating HPCs. The as‐obtained NSPC‐1‐900 ORR catalyst has onset potential (Eonset) and half‐wave potential (E1/2) values of 1.03 and 0.88 V (vs. RHE) respectively, and it represents an air electrode catalyst for Zn‐air batteries with high power density and durability. This work affords a facile and effective strategy of utilizing low‐cost, abundant and sustainable biomass to prepare HPCs for energy storage and conversion.
Investigation of the Phase Equilibria of CO2/CH3OH/H2O and CO2/CH3OH/H2O/H2 Mixtures
Authors: Vogel Kevin , Hocke Elisabeth , Beisswenger Lucien , Drochner Alfons , Etzold Bastian J. M. , Vogel Herbert 
Published: July 2019

AbstractThe storage of excess electricity from renewable energy sources is nowadays a crucial topic. One promising technology is the methanol (CH3OH) synthesis from H2/CO2 mixtures. The achievable one‐pass conversion is limited within this exothermic equilibrium reaction. A possibility to overcome this limitation would be withdrawing CH3OH and H2O from the gas phase through in situ condensation under reaction conditions. In this work, the phase equilibrium for mixtures representative for different degrees of conversion was studied. A view cell was employed to determine systematically the single‐ and two‐phase regimes and obtain phase envelopes for mixtures of H2, CO2, CH3OH, and H2O from 66 to 305 °C and 61 to 233 bar. Furthermore, the densities in the single‐phase area were determined and quantified by an empirical model.
Influence of Temperature on the Performance of Gas Diffusion Electrodes in the CO2 Reduction Reaction
Authors: Löwe Armin , Rieg Carolin , Hierlemann Tim , Salas Nicolas , Kopljar Dennis , Wagner Norbert , Klemm Elias 
Published: July 2019

AbstractA detailed investigation of the influence of operating temperature on the electrochemical reduction of CO2 to formate at tin oxide loaded gas diffusion electrodes (GDEs). Ambient pressure electrolysis is performed between 20 and 70 °C with a focus on maximizing current density and energy efficiency while maintaining an average formate faradaic efficiency of at least 80 %. The best performance is achieved at a temperature of 50 °C, which allows a current density of 1000 mA cm−2. Lower or higher temperatures both show an increased hydrogen evolution at said current density. Further investigation of CO2 transport limitation revealed a minimum at 50 °C, which is explained by the opposing influence of temperature on CO2 diffusion coefficients and solubility. This explanation is supported by an estimate of the current density at which hydrogen evolution starts to increase based on the flooded agglomerate model. Long‐term operation for 24 h also revealed an optimum temperature of 50 °C, which helps to suppress the increasing rate of hydrogen evolution and with that a mechanical degradation of the GDE.
Alkyliodines in High Oxidation State: Enhanced Synthetic Possibilities and Accelerated Catalyst Turn‐Over
Authors: Bosnidou Alexandra E. , Muñiz Kilian 
Published: July 2019

AbstractIn contrast to aryliodine(III) compounds, which have matured into a particularly attractive class of oxidants in modern synthesis, the synthetic potential of related alkyliodine(III) derivatives has remained widely underestimated. This is surprising since several unique synthetic possibilities arise directly from the low stability of their central carbon–iodine bond. In this respect, these high‐oxidation‐state iodine compounds resemble environmentally benign variants of the prominent metal counterparts such as those derived from palladium, nickel and copper. This Concept article summarizes the general reactivity trends in alkyliodine(III) chemistry and discusses selected examples of their strategic use as highly reactive, transient species in organic synthesis and homogeneous catalysis.
Temperature‐Controlled Stereodivergent Synthesis of 2,2′‐Biflavanones Promoted by Samarium Diiodide
Authors: Soto Martín , Soengas Raquel G. , Silva Artur M. S. , Gotor‐Fernández Vicente , Rodríguez‐Solla Humberto 
Published: July 2019

AbstractIn this work, the first example of a radical stereodivergent reaction directed towards the stereoselective synthesis of both (R*,R*)‐ and (R*,S*)‐2,2′‐biflavanones promoted by samarium diiodide is reported. Control experiments showed that the selectivity of this reaction was exclusively controlled by the temperature. It was possible to generate a variety of 2,2′‐biflavanones bearing different substitution patterns at the aromatic ring in good‐to‐quantitative yields, being both stereoisomers of the desired compounds obtained with total or high control of selectivity. A mechanism that explains both the generation of the corresponding 2,2′‐biflavanones and the selectivity is also discussed. The structure and stereochemistry determination of each isomer was unequivocally elucidated by single‐crystal X‐ray diffraction experiments.
Efficacious Doxorubicin Delivery Using Glutathione‐Responsive Hollow Non‐phospholipid Vesicles Bearing Lipoyl Cholesterols
Authors: Kumar Krishan , Yadav Lalit , Kondaiah Paturu , Chaudhary Sandeep 
Published: July 2019

AbstractIn this study, we developed redox‐sensitive vesicles using synthesised lipoyl cholesterol derivatives, a non‐ionic surfactant and an optimum level of free cholesterol. Interestingly, concentration‐dependent self‐assembly was observed by scanning electron microscopy, wherein vesicles manifested as hollow spherical (at 0.15 mm) and triangular (0.50 mm). The redoxresponsive characteristics of the vesicles was probed in the presence of dithiothreitol; they underwent a clear increase in size as observed by dynamic light scattering measurements. These vesicles could easily encapsulate an anticancer drug, doxorubicin, and were observed to be stable in the presence of serum. They showed substantial release of the drug in response to biologically relevant stimulus, that is, glutathione. A toxicity assessment on HeLa and HepG2 cancer cells demonstrated activities of the drug‐loaded vesicles comparable to that of free drug, whereas significantly enhanced toxicity and apoptotic induction were observed against drug‐resistant HeLa cells, which was determined by studying the cellular internalisation of doxorubicin.
Undesired Bulk Oxidation of LiMn2O4 Increases Overpotential of Electrocatalytic Water Oxidation in Lithium Hydroxide Electrolytes
Authors: Baumung Max , Kollenbach Leon , Xi Lifei , Risch Marcel 
Published: July 2019

AbstractChemical and structural changes preceding electrocatalysis obfuscate the nature of the active state of electrocatalysts for the oxygen evolution reaction (OER), which calls for model systems to gain systematic insight. We investigated the effect of bulk oxidation on the overpotential of ink‐casted LiMn2O4 electrodes by a rotating ring‐disk electrode (RRDE) setup and X‐ray absorption spectroscopy (XAS) at the K shell core level of manganese ions (Mn−K edge). The cyclic voltammogram of the RRDE disk shows pronounced redox peaks in lithium hydroxide electrolytes with pH between 12 and 13.5, which we assign to bulk manganese redox based on XAS. The onset of the OER is pH‐dependent on the scale of the reversible hydrogen electrode (RHE) with a Nernst slope of −40(4) mV/pH at −5 μA monitored at the RRDE ring. To connect this trend to catalyst changes, we develop a simple model for delithiation of LiMn2O4 in LiOH electrolytes, which gives the same Nernst slope of delithiation as our experimental data, i. e., 116(25) mV/pH. From this data, we construct an ERHE‐pH diagram that illustrates robustness of LiMn2O4 against oxidation above pH 13.5 as also verified by XAS. We conclude that manganese oxidation is the origin of the increase of the OER overpotential at pH lower than 14 and also of the pH dependence on the RHE scale. Our work highlights that vulnerability to transition metal redox may lead to increased overpotentials, which is important for the design of stable electrocatalysts.
A low‐power voltage differencing buffered amplifier
Authors: Gupta Priyanka , Pandey Rajeshwari 
Published: July 2019

SummaryA low‐voltage, high‐performance voltage differencing buffered amplifier (VDBA) designed using differential flipped voltage followers (DFVF) is presented in this paper. The proposed VDBA is capable of providing high transconductance and wide bandwidth (BW) with low biasing currents and buffer transfer ratio close to unity. Mathematical formulations for transconductance and buffer transfer ratio are deduced through low‐frequency small signal analysis. Pre and post layout simulations for characterization of the proposed structure are carried out on Cadence Virtuoso using gpdk 0.18‐μm CMOS process parameters. The transconductance of the proposed VDBA is observed to be varying from 411.8 μS to 1.374 mS for a corresponding bias current range of 10 to 75 μA, and the 3‐dB bandwidth (BW) is recorded to be 1.2 GHz. The PVT analysis is carried out to show the effect of process corners. To check the robustness of the proposed VDBA, Monte Carlo analysis is performed, and results have been included in the form of histograms.
A low complexity mechanism for congestion notification in rural IPSec‐enabled heterogeneous backhaul networks
Authors: Figuera Carlos , Morgado Eduardo , Municio Esteban , Simó‐Reigadas Javier 
Published: July 2019

SummaryManagement in wireless backhaul networks is a challenging task, especially in rural and isolated environments. In these scenarios, the backhaul network usually consists of a set of heterogeneous wireless links that provide limited and variable bandwidth to the access networks, often 3G/4G small cells. Because of the highly constrained nature of this type of backhaul network, intelligent and joint management in both the backhaul network and the access network is crucial in order to avoid performance degradation caused by traffic congestion. In order to avoid the saturation in the backhaul network, access networks should consider the backhaul state when taking decisions in the admission control and scheduling procedures. However, no standardized mechanisms currently exist for sharing management information between both networks. In this work, we propose to use the Explicit Congestion Notification (ECN) bit in the outer IP headers present in the Iuh 3GPP IPSec‐enabled interfaces in order to notify the backhaul congestion state to the access network. We analyze for the referred scenario, compatibility and security details, validating our approach by running numerically simulations and implementing the notification mechanism. Our low complexity approach offers 2% accuracy and backhaul update latency lower than 10 ms during 80% of the time, which makes the solution appropriate for admission control and scheduling intervals in small cells.
Can we predict histological outcome of distinctive cohorts of patients with glandular cell abnormalities on ThinPrep Papanicolaou testing based on human papillomavirus status, age, and associated squamous abnormalities?
Authors: Harbhajanka Aparna , Dahoud Wissam , Michael Claire W. 
Published: July 2019

AbstractBackgroundThe cytology diagnosis of glandular cell abnormalities (GCAs) is diagnostically challenging, causing inadequate reproducibility. Histological outcome of GCA on cytology varies from benign to malignant diseases. The goal of this study is to evaluate histological outcome and identify distinctive cohorts of patients with GCA based on human papillomavirus (HPV) status, age, and associated squamous abnormality to stratify the patient into high risk for squamous/glandular lesions.MethodsFrom 2012 to 2017, out of 162 088 ThinPrep Papanicolaou tests performed, 998 (0.61%) were reported as GCAs. Histologic follow‐up was available in 638 cases and 429 had concurrent HPV results.ResultsThe overall rate of high‐risk human papillomavirus (hrHPV)‐positivity (hrHPV+) was 33.6% (144/429 cases). Among the hrHPV+ cases, 18.1% had cervical intraepithelial neoplasia 2/3 (CIN2/3), 3.5% squamous cell carcinoma (SCC), 3.5% cervical adenocarcinoma in situ (AIS)/adenocarcinoma (ADC), and 2.8% endometrial carcinoma. Among hrHPV‐ cases, 1.4% had CIN2/3, 1.1% AIS/ADC, and 17.5% endometrial carcinoma. The high‐grade cervical lesions (CIN2/3/AIS/ADC) were significantly higher in women with hrHPV+ and associated squamous abnormalities compared to hrHPV‐ and no squamous abnormality in all age groups except patients >65 years. Endometrial carcinoma was most commonly present in women >65 years especially with HPV‐ and no associated squamous abnormalities.ConclusionsHPV testing is useful for predicting the risk of high‐grade cervical neoplasia in women with GCA especially with associated squamous abnormalities on cytology. The endometrial carcinoma is more frequent in hrHPV‐ older women. The combination of cytology with knowledge of associated squamous abnormality, hrHPV status, and age can significantly aid in stratifying the patient into high risk for glandular/squamous lesions which facilitates appropriate management of these patients.
Feedbacks between nitrogen fixation and soil organic matter increase ecosystem functions in diversified agroecosystems
Authors: Blesh Jennifer 
Published: July 2019

AbstractNitrogen (N) losses from intensified agriculture are a major cause of global change, due to nitrate (NO3−) export and the eutrophication of aquatic systems as well as emissions of nitrous oxide (N2O) into the atmosphere. Diversified agroecosystems with legume cover crops couple N and carbon (C) inputs to soil and reduce N pollution, but there is a need to identify controls on legume N2 fixation across ecosystems with variable soil conditions. Here, I tested the hypothesis that N mineralization from turnover of soil organic matter (SOM) regulates legume N2 fixation across 10 farms that spanned a gradient of SOM levels. I separated soil samples into two SOM fractions, based on size and density, which are indicators of soil nutrient cycling and N availability (free particulate organic matter and intra‐aggregate particulate organic matter [POM]). This study indicates downregulation of legume N2 fixation in diversified agroecosystems with increasing N availability in intra‐aggregate POM and increasing N mineralization. Intercropping the legume with a grass weakened the relationship between N in POM and N2 fixation due to N assimilation by the grass. Further, mean rates of N and C mineralization across sites increased with two seasons of a legume‐grass cover crop mixture, which could enhance this stabilizing feedback between soil N availability and N2 fixation over time. These results suggest a potential mechanism for the diversity–ecosystem‐function relationships measured in long‐term studies of agroecosystems, in which regular use of legume cover crops increases total soil organic C and N and reduces negative environmental impacts of crop production.
Physiological dynamics, reproduction‐maintenance allocations, and life history evolution
Authors: English Sinead , Bonsall Michael B. 
Published: July 2019

AbstractAllocation of resources to competing processes of growth, maintenance, or reproduction is arguably a key process driving the physiology of life history trade‐offs and has been shown to affect immune defenses, the evolution of aging, and the evolutionary ecology of offspring quality. Here, we develop a framework to investigate the evolutionary consequences of physiological dynamics by developing theory linking reproductive cell dynamics and components of fitness associated with costly resource allocation decisions to broader life history consequences. We scale these reproductive cell allocation decisions to population‐level survival and fecundity using a life history approach and explore the effects of investment in reproduction or tissue‐specific repair (somatic or reproductive) on the force of selection, reproductive effort, and resource allocation decisions. At the cellular level, we show that investment in protecting reproductive cells increases fitness when reproductive cell maturation rate is high or reproductive cell death is high. At the population level, life history fitness measures show that cellular protection increases reproductive value by differential investment in somatic or reproductive cells and the optimal allocation of resources to reproduction is moulded by this level of investment. Our model provides a framework to understand the evolutionary consequences of physiological processes underlying trade‐offs and highlights the insights to be gained from considering fitness at multiple levels, from cell dynamics through to population growth.
Mediation of stemflow water and nutrient availabilities by epiphytes growing above other epiphytes in a subtropical forest
Authors: Chen Liang‐Chu , Wang Lih‐Jih , Martin Craig E. , Lin Teng‐Chiu 
Published: July 2019

AbstractStemflow is the most importance source of water and nutrients to epiphytes growing on tree stems that lack access to canopy soils. Many host trees are inhabited by a large number of epiphyte species, often growing in close proximity. The nutrient and water relationships among such co‐occurring epiphytes are largely unknown. We examined stemflow quality and quantity before and after passing through a substrate‐forming epiphyte, Asplenium nidus, and two nonsubstrate‐forming epiphytes, Haplopteris flexuosa and Liparis nakaharai, in a subtropical rainforest in Taiwan. The results indicate that stemflow quantity decreased after passing through these epiphytes. The magnitude of decreases was large for H. flexuosa (63%) and L. nakaharai (74%) but minor for A. nidus (5.6%), possibly because the vertical leaves of the latter collected throughfall, compensating for the water they retained. There was an overall decrease in stemflow ion concentrations after passing through A. nidus, likely due to greater retention than leaching of ions, but an overall increase after passing through L. nakaharai and H. flexuosa, possibly the result of greater leaching than retention. Our results indicate that epiphytes growing under A. nidus received more stemflow with few nutrients and those growing under the two nonsubstrate‐forming epiphytes received less stemflow but with more nutrients. Currently, the growth of epiphytes is limited by water at the study site, so that Asplenium provides favourable microhabitat for epiphytes growing below. If climate change lead to drier conditions, substrate‐forming epiphytes could become oases in the forest canopy desert and attract more epiphytes to grow underneath.
Trends in modes of death in heart failure over the last two decades: less sudden death but cancer deaths on the rise
Authors: Moliner Pedro , Lupón Josep , de Antonio Marta , Domingo Mar , Santiago‐Vacas Evelyn , Zamora Elisabet , Cediel Germán , Santesmases Javier , Díez‐Quevedo Crisanto , Troya Maria Isabel , Boldó Maria , Altmir Salvador , Alonso Nuria , González Beatriz , Núñez Julio , Bayes‐Genis Antoni 
Published: July 2019

AimsBetter management of heart failure (HF) over the past two decades has improved survival, mainly by reducing the incidence of death due to cardiovascular (CV) causes. Deaths due to non‐CV causes, particularly cancer, may be increasing. This study explored the modes of death of consecutive patients who attended a HF clinic over 17 years.Methods and resultsA total of 935 deaths were ascertained from 2002 to 2018 among 1876 patients (mean age 65.8 ± 12.5 years, 75% men, left ventricular ejection fraction < 50%) admitted to our HF clinic. Median follow‐up was 4.2 years [1.9–7.8]. Mode of death was curated from patient health records and verified by the Catalan and Spanish health system databases. Trends for every mode of death were assessed by polynomial regression. Two trends were observed: a significant reduction in sudden death (P = 0.03) without changes in HF progression as mode of death (P = 0.26), and a significant increase in non‐CV modes of death (P < 0.001). Non‐CV deaths accounted for 17.4% of deaths in 2002 and 65.8% of deaths in 2018. A total 138 deaths were due to cancer (37% of non‐CV deaths). A significant trend was observed towards a progressive increase in cancer deaths over time (P = 0.002). The main mode of cancer mortality was lung cancer.ConclusionsThe modes of death in HF have shifted over the last two decades. Patients with HF die less due to sudden death and more due to non‐CV causes, mainly cancer. Whether HF triggers cancer, or cancer develops in HF survivors, deserves further insight.