bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Semiconductor Surfactants with Fullerenol Heads and Colored Tails for Carbon Dioxide Photoconversion
Authors: Kunkel Marius , Sutter Sebastian , Polarz Sebastian
Published: July 2019

The leaf is a prime example of a material converting waste (CO2) into value with maximum sustainability. As the most important constituent, it contains the coupled photosystems II and I, which are imbedded in the cellular membrane of the chloroplasts. Can key functions of the leaf be packed into soap? We present next‐generation surfactants that self‐assemble into bilayer vesicles (similar to the cellular membrane), are able to absorb photons of two different visible wavelengths, and exchange excited charge carriers (similar to the photosystems), followed by conversion of CO2 (in analogy to the leaf). The amphiphiles contain five dye molecules as the hydrophobic entity attached exclusively to one hemisphere of a polyhydroxylated fullerene (Janus‐type). We herein report on their surfactant, optical, electronic, and catalytic properties. Photons absorbed by the dyes are transferred to the fullerenol head, where they can react with different species such as CO2 to give formic acid.
Perquinolines A–C: Unprecedented Bacterial Tetrahydroisoquinolines Involving an Intriguing Biosynthesis
Authors: Rebets Yuriy , Nadmid Suvd , Paulus Constanze , Dahlem Charlotte , Herrmann Jennifer , Hübner Harald , Rückert Christian , Kiemer Alexandra K. , Gmeiner Peter , Kalinowski Jörn , Müller Rolf , Luzhetskyy Andriy
Published: July 2019

Metabolic profiling of Streptomyces sp. IB2014/016‐6 led to the identification of three new tetrahydroisoquinoline natural products, perquinolines A–C (1–3). Labelled precursor feeding studies and the cloning of the pqr biosynthetic gene cluster revealed that 1–3 are assembled by the action of several unusual enzymes. The biosynthesis starts with the condensation of succinyl‐CoA and l‐phenylalanine catalyzed by the amino‐7‐oxononanoate synthase‐like enzyme PqrA, representing rare chemistry in natural product assembly. The second condensation and cyclization events are conducted by PqrG, an enzyme resembling an acyl‐CoA ligase. Last, ATP‐grasp RimK‐type ligase PqrI completes the biosynthesis by transferring a γ‐aminobutyric acid or β‐alanine moiety. The discovered pathway represents a new route for assembling the tetrahydroisoquinoline cores of natural products.
Coupling of Solar Energy and Thermal Energy for Carbon Dioxide Reduction: Status and Prospects
Authors: Wang Zhou‐jun , Song Hui , Liu Huimin , Ye Jinhua
Published: July 2019

Enormous efforts have been devoted to the reduction of carbon dioxide (CO2) by utilizing various driving forces, such as heat, electricity, and radiation. However, the efficient reduction of CO2 is still challenging because of sluggish kinetics. Recent pioneering studies from several groups, including us, have demonstrated that the coupling of solar energy and thermal energy offers a novel and promising strategy to promote the activity and/or manipulate selectivity in CO2 reduction. Herein, we clarify the definition and principles of coupling solar energy and thermal energy, and comprehensively review the status and prospects of CO2 reduction by coupling solar energy and thermal energy. Catalyst design, reactor configuration, photo‐mediated activity/selectivity, and mechanism studies in photo‐thermo CO2 reduction will be emphasized. The aim of this Review is to promote understanding towards CO2 activation and provide guidelines for the design of new catalysts for the efficient reduction of CO2.
Nucleophilic Iron Complexes in Proton‐Transfer Catalysis: An Iron‐Catalyzed Dimroth Cyclocondensation
Authors: Baykal Aslihan , Zhang Dihan , Knelles Jakob , Alt Isabel T. , Plietker Bernd
Published: July 2019

The nucleophilic iron complex Bu4N[Fe(CO)3(NO)] (TBA[Fe]) is an active catalyst in C−H‐amination but also in proton‐transfer catalysis. Herein, we describe the successful use of this complex as a proton‐transfer catalyst in the cyclocondensation reaction between azides and ketones to the corresponding 1,2,3‐triazoles. Cross‐experiments indicate that the proton‐transfer catalysis is significantly faster than the nitrene‐transfer catalysis, which would lead to the C−H amination product. An example of a successful sequential Dimroth triazole–indoline synthesis to the corresponding triazole‐substituted indolines is presented.
On the validity of time‐dependent AUC estimation in the presence of cure fraction
Authors: Beyene Kassu M. , El Ghouch Anouar , Oulhaj Abderrahim
Published: July 2019

During the last decades, several approaches have been proposed to estimate the time‐dependent area under the receiver operating characteristic curve (AUC) of risk tools derived from survival data. The validity of these estimators relies on some regularity assumptions among which a survival function being proper. In practice, this assumption is not always satisfied because a fraction of the population may not be susceptible to experience the event of interest even for long follow‐up. Studying the sensitivity of the proposed estimators to the violation of this assumption is of substantial interest. In this paper, we investigate the performance of a nonparametric simple estimator, developed for classical survival data, in the case when the population exhibits a cure fraction. Motivated from the current practice of deriving risk tools in oncology and cardiovascular disease prevention, we also assess the loss, in terms of predictive performance, when deriving risk tools from survival models that do not acknowledge the presence of cure. The simulation results show that the investigated method is valid even under the presence of cure. They also show that risk tools derived from survival models that ignore the presence of cure have smaller AUC compared to those derived from survival models that acknowledge the presence of cure. This was also attested with a real data analysis from a breast cancer study.
External validation of a prognostic model to predict survival of patients with sentinel node-negative melanoma
Authors: Ipenburg N A , Nieweg O E , Ahmed T , van Doorn R , Scolyer R A , Long G V , Thompson J F , Lo S
Published: July 2019

Background

Identifying patients with sentinel node-negative melanoma at high risk of recurrence or death is important. The European Organisation for Research and Treatment of Cancer (EORTC) recently developed a prognostic model including Breslow thickness, ulceration and site of the primary tumour. The aims of the present study were to validate this prognostic model externally and to assess whether it could be improved by adding other prognostic factors.

Methods

Patients with sentinel node-negative cutaneous melanoma were included in this retrospective single-institution study. The β values of the EORTC prognostic model were used to predict recurrence-free survival and melanoma-specific survival. The predictive performance was assessed by discrimination (c-index) and calibration. Seeking to improve the performance of the model, additional variables were added to a Cox proportional hazards model.

Results

Some 4235 patients with sentinel node-negative cutaneous melanoma were included. The median follow-up time was 50 (i.q.r. 18·5–81·5) months. Recurrences and deaths from melanoma numbered 793 (18·7 per cent) and 456 (10·8 per cent) respectively. Validation of the EORTC model showed good calibration for both outcomes, and a c-index of 0·69. The c-index was only marginally improved to 0·71 when other significant prognostic factors (sex, age, tumour type, mitotic rate) were added.

Conclusion

This study validated the EORTC prognostic model for recurrence-free and melanoma-specific survival of patients with negative sentinel nodes. The addition of other prognostic factors only improved the model marginally. The validated EORTC model could be used for personalizing follow-up and selecting high-risk patients for trials of adjuvant systemic therapy.
Effect of Solvent, Role of Formic Acid and Rh/C Catalyst for the Efficient Liquefaction of Lignin
Authors: Matsagar Babasaheb M. , Wang Zheng‐Yen , Sakdaronnarong Chularat , Chen Season S. , Tsang Daniel C. W. , Wu Kevin C.‐W.
Published: July 2019

We demonstrate highly efficient liquefaction of alkali lignin with a very high yield of THF‐soluble bio‐oil (91.5 wt %) using formic acid (FA) and Rh/C catalyst under relatively mild reaction conditions (250 °C, 6 h) in EtOH−H2O co‐solvent system. The monomeric products are identified in which alkyl guaiacols accounts for the main proportion. The role of FA was not only used as a liquid‐phase in‐situ hydrogen source but also acts as organic acid which can catalyze the hydrolysis reaction of −C−O−C ether bonds of lignin. Moreover, in the present study, the role of Rh/C and FA is demonstrated for the liquefaction of lignin. The replacement of pure H2 gas by the liquid‐phase FA (hydrogen source) can effectively prevent the char formation. The utilization of Rh/C catalyst helps for the conversion of alkenyl guaiacols to alkyl guaiacols suggesting the hydrogenation of phenolic monomers and further cleavage by hydrogenation results in the formation of bio‐oil with lower molecular weight (Mn=466 g mol−1) as well as lower O/C ratio (0.26).
HFIP‐Functionalized Co3O4 Micro‐Nano‐Octahedra/rGO as a Double‐Layer Sensing Material for Chemical Warfare Agents
Authors: Alali Khaled Tawfik , Liu Jingyuan , Chen Rongrong , Liu Qi , Zhang Hongsen , Li Jundong , Hou Jindi , Li Rumin , Wang Jun
Published: July 2019

Semiconductor metal oxides (SMO)‐based gas‐sensing materials suffer from insufficient detection of a specific target gas. Reliable selectivity, high sensitivity, and rapid response–recovery times under various working conditions are the main requirements for optimal gas sensors. Chemical warfare agents (CWA) such as sarin are fatal inhibitors of acetylcholinesterase in the nerve system. So, sensing materials with high sensitivity and selectivity toward CWA are urgently needed. Herein, micro‐nano octahedral Co3O4 functionalized with hexafluoroisopropanol (HFIP) were deposited on a layer of reduced graphene oxide (rGO) as a double‐layer sensing materials. The Co3O4 micro‐nano octahedra were synthesized by direct growth from electrospun fiber templates calcined in ambient air. The double‐layer rGO/Co3O4‐HFIP sensing materials presented high selectivity toward DMMP (sarin agent simulant, dimethyl methyl phosphonate) versus rGO/Co3O4 and Co3O4 sensors after the exposure to various gases owing to hydrogen bonding between the DMMP molecules and Co3O4‐HFIP. The rGO/Co3O4‐HFIP sensors showed high stability with a response signal around 11.8 toward 0.5 ppm DMMP at 125 °C, and more than 75 % of the initial response was maintained under a saturated humid environment (85 % relative humidity). These results prove that these double‐layer inorganic–organic composite sensing materials are excellent candidates to serve as optimal gas‐sensing materials.
ZnO Quantum Dots Coupled with Graphene toward Electrocatalytic N2 Reduction: Experimental and DFT Investigations
Authors: Liu Ya‐ping , Li Yu‐biao , Huang Da‐jian , Zhang Hu , Chu Ke
Published: July 2019

Electrochemical reduction of N2 to NH3 is a promising method for artificial N2 fixation, but it requires efficient and robust electrocatalysts to boost the N2 reduction reaction (NRR). Herein, a combination of experimental measurements and theoretical calculations revealed that a hybrid material in which ZnO quantum dots (QDs) are supported on reduced graphene oxide (ZnO/RGO) is a highly active and stable catalyst for NRR under ambient conditions. Experimentally, ZnO/RGO was confirmed to favor N2 adsorption due to the largely exposed active sites of ultrafine ZnO QDs. DFT calculations disclosed that the electronic coupling of ZnO with RGO resulted in a considerably reduced activation‐energy barrier for stabilization of *N2H, which is the rate‐limiting step of the NRR. Consequently, ZnO/RGO delivered an NH3 yield of 17.7 μg h−1 mg−1 and a Faradaic efficiency of 6.4 % in 0.1 m Na2SO4 at −0.65 V (vs. RHE), which compare favorably to those of most of the reported NRR catalysts and thus demonstrate the feasibility of ZnO/RGO for electrocatalytic N2 fixation.
Gold(I) Complexes Stabilized by Nine‐ and Ten‐Membered N‐Heterocyclic Carbene Ligands
Authors: Cervantes‐Reyes Alejandro , Rominger Frank , Rudolph Matthias , Hashmi A. Stephen K.
Published: July 2019

Nine‐ and ten‐membered N‐heterocyclic carbene (NHC) ligands have been developed and for the first time their gold(I) complexes were synthesized. The protonated NHC pro‐ligands 2 a–h were prepared by the reaction of readily available N,N′‐diarylformamidines with bis‐electrophilic building blocks, followed by anion exchange. In situ deprotonation of the tetrafluoroborates 2 a–h with tBuOK in the presence of AuCl(SMe2) provided fast access to NHC‐gold(I) complexes 3–10. These new NHC‐gold(I) complexes show very good catalytic activity in a cycloisomerization reaction (0.1 mol % catalyst loading, up to 100 % conversion) and their solid‐state structures reveal high steric hindrance around the metal atom (%Vbur up to 53.0) which is caused by their expanded‐ring architecture.
Tuning Redox Active Polyoxometalates for Efficient Electron‐Coupled Proton‐Buffer‐Mediated Water Splitting
Authors: Lei Jie , Yang Jun‐Jie , Liu Ting , Yuan Ru‐Ming , Deng Ding‐Rong , Zheng Ming‐Sen , Chen Jia‐Jia , Cronin Leroy , Dong Quan‐Feng
Published: July 2019

We present strategies to tune the redox properties of polyoxometalate clusters to enhance the electron‐coupled proton‐buffer‐mediated water splitting process, in which the evolution of hydrogen and oxygen can occur in different forms and is separated in time and space. By substituting the heteroatom template in the Keggin‐type polyoxometalate cluster, H6ZnW12O40, it is possible to double the number of electrons and protonation in the redox reactions (from two to four). This increase can be achieved with better matching of the energy levels as indicated by the redox potentials, compared to the ones of well‐studied H3PW12O40 and H4SiW12O40. This means that H6ZnW12O40 can act as a high‐performance redox mediator in an electrolytic cell for the on‐demand generation of hydrogen with a high decoupling efficiency of 95.5 % and an electrochemical energy efficiency of 83.3 %. Furthermore, the H6ZnW12O40 cluster also exhibits an excellent cycling behaviour and redox reversibility with almost 100 % H2‐mediated capacity retention during 200 cycles and a high coulombic efficiency >92 % each cycle at 30 mA cm−2.
Cover Picture: Catalytic Enantioselective Protonation of Monofluorinated Silyl Enol Ethers towards Chiral α‐Fluoroketones (Chin. J. Chem. 8/2019)
Authors: Liao Kui , Hu Xiao‐Si , Zhu Ren‐Yi , Rao Ruo‐Han , Yu Jin‐Sheng , Zhou Feng , Zhou Jian
Published: July 2019

The cover picture shows a highly enantioselective organocatalytic protonation of monofluorinated silyl enol ethers to α‐secondary α‐fluoroketones using water as proton source. Notably, in the presence of D2O and MeOD, the facile access of chiral α‐deuterated α‐fluoroketones in excellent enantioselectivity is achieved. More details are discussed by Zhou et al. on page 799–806.

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On the Oxidation State of Cu2O upon Electrochemical CO2 Reduction: An XPS Study
Authors: Permyakova Anastasia A. , Herranz Juan , El Kazzi Mario , Diercks Justus S. , Povia Mauro , Mangani Léa Rose , Horisberger Michael , Pătru Alexandra , Schmidt Thomas J.
Published: July 2019

The encouraging selectivity of copper oxides for the electroreduction of CO2 into ethylene and alcohols has led to a vivid debate on the possible relation between their operando (sub‐)surface oxidation state (i. e. fully reduced or partially oxidized) and this distinct reactivity. The high roughness of the Cu oxides used in previous studies on this matter adds complexity to this controversy and motivated us to prepare quasi‐planar Cu2O thin films that displayed a CO2 reduction selectivity similar to that of oxide‐derived copper catalysts reported in previous studies. Most importantly, when the post‐mortem thin films were transferred for characterization in an air‐free environment, X‐ray photoelectron spectroscopy measurements confirmed their complete reduction in the course of the CO2 reduction reaction. Thus, our results indicate that the selectivity of the Cu oxides featured in previous studies stems from their enhanced roughness, highlighting the importance of controlled sample transfer upon post‐mortem characterization with ex situ techniques.
Influences of potential oil and gas development and future climate on Sage‐grouse declines and redistribution
Authors: Heinrichs Julie A. , O'Donnell Michael S. , Aldridge Cameron L. , Garman Steven L. , Homer Collin G.
Published: July 2019

Multiple environmental stressors impact wildlife populations, but we often know little about their cumulative and combined influences on population outcomes. We generally know more about past effects than potential future impacts, and direct influences such as changes of habitat footprints than indirect, long‐term responses in behavior, distribution, or abundance. Yet, an understanding of all these components is needed to plan for future landscapes that include human activities and wildlife. We developed a case study to assess how spatially explicit individual‐based modeling could be used to evaluate future population outcomes of gradual landscape change from multiple stressors. For Greater Sage‐grouse in southwest Wyoming, USA, we projected oil and gas development footprints and climate‐induced vegetation changes 50 years into the future. Using a time‐series of planned oil and gas development and predicted climate‐induced changes in vegetation, we recalculated habitat selection maps to dynamically modify future habitat quantity, quality, and configuration. We simulated long‐term Sage‐grouse responses to habitat change by allowing individuals to adjust to shifts in habitat availability and quality. The use of spatially explicit individual‐based modeling offered a useful means of evaluating delayed indirect impacts of landscape change on wildlife population outcomes. The inclusion of movement and demographic responses to oil and gas infrastructure resulted in substantive changes in distribution and abundance when cumulated over several decades and throughout the regional population. When combined, additive development and climate‐induced vegetation changes reduced abundance by up to half of the original size. In our example, the consideration of only a single population stressor the final possible population size by as much as 50%. Multiple stressors and their cumulative impacts need to be broadly considered through space and time to avoid underestimating the impacts of multiple gradual changes and overestimating the ability of populations to withstand change.
Northern forest winters have lost cold, snowy conditions that are important for ecosystems and human communities
Authors: Contosta Alexandra R. , Casson Nora J. , Garlick Sarah , Nelson Sarah J. , Ayres Matthew P. , Burakowski Elizabeth A. , Campbell John , Creed Irena , Eimers Catherine , Evans Celia , Fernandez Ivan , Fuss Colin , Huntington Thomas , Patel Kaizad , Sanders‐DeMott Rebecca , Son Kyongho , Templer Pamela , Thornbrugh Casey
Published: July 2019

Winter is an understudied but key period for the socioecological systems of northeastern North American forests. A growing awareness of the importance of the winter season to forest ecosystems and surrounding communities has inspired several decades of research, both across the northern forest and at other mid‐ and high‐latitude ecosystems around the globe. Despite these efforts, we lack a synthetic understanding of how winter climate change may impact hydrological and biogeochemical processes and the social and economic activities they support. Here, we take advantage of 100 years of meteorological observations across the northern forest region of the northeastern United States and eastern Canada to develop a suite of indicators that enable a cross‐cutting understanding of (1) how winter temperatures and snow cover have been changing and (2) how these shifts may impact both ecosystems and surrounding human communities. We show that cold and snow covered conditions have generally decreased over the past 100 years. These trends suggest positive outcomes for tree health as related to reduced fine root mortality and nutrient loss associated with winter frost but negative outcomes as related to the northward advancement and proliferation of forest insect pests. In addition to effects on vegetation, reductions in cold temperatures and snow cover are likely to have negative impacts on the ecology of the northern forest through impacts on water, soils, and wildlife. The overall loss of coldness and snow cover may also have negative consequences for logging and forest products, vector‐borne diseases, and human health, recreation, and tourism, and cultural practices, which together represent important social and economic dimensions for the northern forest region. These findings advance our understanding of how our changing winters may transform the socioecological system of a region that has been defined by the contrasting rhythm of the seasons. Our research also identifies a trajectory of change that informs our expectations for the future as the climate continues to warm.
Why are monarch butterflies declining in the West? Understanding the importance of multiple correlated drivers
Authors: Crone Elizabeth E. , Pelton Emma M. , Brown Leone M. , Thomas Cameron C. , Schultz Cheryl B.
Published: July 2019

Understanding the factors associated with declines of at‐risk species is an important first step in setting management and recovery targets. This step can be challenging when multiple aspects of climate and land use are changing simultaneously, and any or all could be contributing to population declines. We analyzed population trends of monarch butterflies in western North America in relation to likely environmental drivers. Unlike the larger eastern monarch population, past analyses of western monarchs have only evaluated the importance of climate (i.e., not land use) factors as drivers of abundance. We used partial least squares regression (PLSR) to evaluate the potential importance of changes in land use and climate variables. Trends in western monarch abundance were more strongly associated with land use variables than climate variables. Conclusions about importance of climate and land use variables were robust to changes in PLSR model structure. However, individual variables were too collinear to unambiguously separate their effects. We compared these conclusions to the more widely used technique of multiple regression, followed by multi‐model inference (MRMI). Naïve interpretation of MRMI results could be misleading, if collinearity were not taken into account. MRMI was also highly sensitive to variation in model construction. Our results suggest a two‐pronged approach to monarch conservation, specifically, starting efforts now to restore habitat, while also using experiments to more clearly delineate separate effects of climate and land use factors. They also demonstrate the utility of PLSR, a technique that is growing in use but is still relatively under‐appreciated in conservation biology.
Nitrogen controls the net primary production of an alpine Kobresia meadow in the northern Qinghai‐Tibet Plateau
Authors: Dai Licong , Ke Xun , Du Yangong , Zhang Fawei , Li Yikang , Li Qian , Lin Li , Peng Cuoji , Shu Kai , Cao Guangmin , Guo Xiaowei
Published: July 2019

Net primary production (NPP) is a fundamental property of natural ecosystems. Understanding the temporal variations of NPP could provide new insights into the responses of communities to environmental factors. However, few studies based on long‐term field biomass measurements have directly addressed this subject in the unique environment of the Qinghai‐Tibet plateau (QTP). We examined the interannual variations of NPP during 2008–2015 by monitoring both aboveground net primary productivity (ANPP) and belowground net primary productivity (BNPP), and identified their relationships with environmental factors with the general linear model (GLM) and structural equation model (SEM). In addition, the interannual variation of root turnover and its controls were also investigated. The results show that the ANPP and BNPP increased by rates of 15.01 and 143.09 g/m2 per year during 2008–2015, respectively. BNPP was mainly affected by growing season air temperature (GST) and growing season precipitation (GSP) rather than mean annual air temperature (MAT) or mean annual precipitation (MAP), while ANPP was only controlled by GST. In addition, available nitrogen (AN) was significantly positively associated with BNPP and ANPP. Root turnover rate averaged 30%/year, increased with soil depth, and was largely controlled by GST. Our results suggest that alpine Kobresia meadow was an N‐limited ecosystem, and the NPP on the QTP might increase further in the future in the context of global warming and nitrogen deposition.
Bumble bee parasite prevalence but not genetic diversity impacted by the invasive plantImpatiens glandulifera
Authors: Vanderplanck Maryse , Roger Nathalie , Moerman Romain , Ghisbain Guillaume , Gérard Maxence , Popowski Dominik , Granica Sebastian , Fournier Denis , Meeus Ivan , Piot Niels , Smagghe Guy , Terrana Lucas , Michez Denis
Published: July 2019

While many bee species are experiencing population declines, some host plant generalist bees remain common in Europe, partly because they seem able to shift to new resources. However, foraging on a new alternative plant, such as an invasive species, can modify diet quality and have a potentially detrimental effect on bee health. Herein, we investigated whether the spread of the invasive plantImpatiens glanduliferaaffectsBombus pascuorumpopulation regarding parasite prevalence, genetic structure, and nest density in Belgium. While no difference in bumble bee genetic structure was detected between invaded and uninvaded sites, we show thatI. glanduliferaoccurrence was significantly correlated with a decrease in the prevalence ofApicystis bombibut not the prevalence of three other parasite species (i.e.,Crithidia bombi,Nosema bombi,Nosema ceranae, andNosemasp.). Regarding our investigations, this effect was likely not due to variation in local bumble bee population fitness beforeI. glanduliferaflowering, nor to the relative abundance of other pollinators such asApis mellifera, but the unique chemical composition (i.e., polyphenol rich) of the pollen ofI. glanduliferaremained as an interesting hypothesis. WhereasB. pascuorumqueens probably colonize all the potential nesting sites in an area, invaded byI. glanduliferaor not, the abundance of polyphenol ampelopsin in pollen fromI. glanduliferapollen might reduce local parasite prevalence. Our field study confirms that bumble bee parasite prevalence is potentially related to the particular chemical composition of collected pollen. Plant traits such as secondary metabolite occurrence could play a key role in the health and conservation of bumble bees.
Fire, leaf harvest, and abiotic factors drive demography of an ecologically and culturally important understory plant
Authors: Hart‐Fredeluces G. , Ticktin T.
Published: July 2019

Understanding how multiple simultaneous drivers interact to influence plant demography is critical for protecting plant diversity in the context of global change. Fire is a key disturbance in forested ecosystems, but the interactive effects of fire and other abiotic and management factors on understory plants are poorly understood. Beargrass (Xerophyllum tenax) is perennial herb that provides food, habitat, and nesting material for a wide range of animals. Beargrass populations are prescribe‐burned by Native American experts, and leaves are subsequently harvested at low‐intensity for use in weaving. Leaves for weaving are reportedly becoming harder to find due to lack of fire and competition with commercial harvesters. To elucidate the effects of fire and its interactions with leaf harvest and abiotic factors on beargrass populations, we collected demographic data on more than 1000 individuals over three years across fire severities in combination with individual‐level soil moisture and light measurements. We also conducted an experiment simulating low‐intensity leaf harvest. We built mixed‐effects models to test our predictions that fire would increase growth and reproduction, and that it would mediate the effects of soil moisture and leaf harvest on beargrass growth. Fire increased growth as well as sexual and vegetative reproduction, providing evidence that beargrass is fire‐adapted. Leaf harvest both reduced survival probability and increased the probability of vegetative reproduction. Individual growth increased with early growing season soil moisture in unburned and low‐severity fire areas but did not vary with soil moisture in high‐severity areas. In sum, fire is a key driver of beargrass demography and fire interacted with other factors to influence beargrass vital rates. Understanding the impacts of changes to management and abiotic factors on understory species such as beargrass, and the ecosystem services they provide, requires attention to interactions among multiple environmental factors.
Rain downpours affect survival and development of insect herbivores: the specter of climate change?
Authors: Chen Cong , Harvey Jeffrey A. , Biere Arjen , Gols Rieta
Published: July 2019

Changes in the frequency, duration, and intensity of rainfall events are among the abiotic effects predicted under anthropogenic global warming. Heavy downpours may profoundly affect the development and survival of small organisms such as insects. Here, we examined direct (physically on the insects) and indirect (plant‐mediated) effects of simulated downpours on the performance of caterpillars of two lepidopteran herbivores (Plutella xylostella and Pieris brassicae) feeding on black mustard (Brassica nigra) plants. Host plants were exposed to different rainfall regimes both before and while caterpillars were feeding on the plants in an attempt to separate direct and indirect (plant‐mediated) effects of rainfall on insect survival and development. In two independent experiments, downpours were simulated as a single long (20 min) or as three short (5 min) daily events. Downpours had a strong negative direct effect on the survival of P. xylostella, but not on that of P. brassicae. Direct effects of downpours consistently increased development time of both herbivore species, whereas effects on body mass depended on herbivore species and downpour frequency. Caterpillar disturbance by rain and recorded microclimatic cooling by 5°C may explain extended immature development. Indirect, plant‐mediated effects of downpours on the herbivores were generally small, despite the fact that sugar concentrations were reduced and herbivore induction of secondary metabolites (glucosinolates) was enhanced in plants exposed to rain. Changes in the frequency of precipitation events due to climate change may impact the survival and development of insect herbivores differentially. Broader effects of downpours on insects and other arthropods up the food chain could seriously impair and disrupt trophic interactions, ultimately destabilizing communities.
Indolylglycines Backbones in the Synthesis of Enantiopure 3,3‐Spiroindolenines, Indolyl Tetracyclic Hemiaminals, and 3‐Indolyl‐maleimides Frameworks
Authors: Markus Jozef , Ferko Branislav , Berkeš Dušan , Moncol Ján , Lawson Ata Martin , Othman Mohamed , Daïch Adam
Published: July 2019

This paper describes the synthesis of novel N‐substituted 3‐indolylglycines (3IGs), in high yields and optical purity via three‐component Mannich reaction (3CR) of indole and free glyoxylic acid in the presence of primary and secondary aliphatic amines. By using this efficient approach, a series of racemic 3‐indolylglycines (3IGs) as well as the optically pure (S)‐3‐indolylglycine ((S)‐3IG) in multigram synthesis using (R‐1‐phenylethylamine ((R)‐α‐PEA) as chiral pool were synthetized. In parallel investigations, 3IGs were used as the starting material for the highly stereoselective synthesis of spiroindolenines bearing three controlled contiguous stereogenic centers. Despite our expectations, the N‐chloroacetyl esters of 3IGs did not provide the expected spiroindolenine derivatives but led us to the discovery of a new methodology for the preparation of 3‐indolylmaleimides (3IMs); compounds known for their broad range of important biological and fluorescence activities.
sp2‐C–H Acetoxylation of Diversely Substituted (E)‐1‐(Arylmethylene)‐2‐phenylhydrazines Using PhI(OAc)2 as Acetoxy Source at Ambient Conditions
Authors: Brahmachari Goutam , Karmakar Indrajit
Published: July 2019

A catalyst‐ and additive‐free simple and straightforward method for regioselective direct sp2 C–H acetoxylation reaction of aldehyde hydrazones has been achieved at ambient temperature employing PIDA as an acetoxy source. The scope of the reaction has been successfully verified with a wide range of biologically important aldehyde hydrazones with diverse functional group tolerance. The method is highly selective, mild and efficient, operationally simple, rapid and high‐yielding.
Designing Graphite‐Based Positive Electrodes and Their Properties in Dual‐Ion Batteries Using Particle Size‐Adjusted Active Materials
Authors: Nowak Christine , Froboese Linus , Winter Martin , Placke Tobias , Haselrieder Wolfgang , Kwade Arno
Published: July 2019

In almost all state‐of‐the‐art lithium‐ion batteries, the negative electrode is made from graphite. For dual‐ion batteries (DIBs), graphite electrodes can even be used as negative and positive electrodes as the electrolyte provides both cations and anions for energy storage. As the amount of active material is very high in graphite electrodes, one of the main structure‐controlling parameters is its particle size distribution (PSD). Based on changes in the active material particle size and resulting changes in electrode structure, the corresponding cell characteristics like coulombic efficiency or power density are strongly affected. Herein, results for graphite positive electrodes manufactured with different PSDs of one typical commercial synthetic graphite are displayed. A high‐performance single‐wheel air classifier is used to create the differently distributed graphite particle fractions that do not vary in particle shapes for all fractions created. To gain a better understanding of the particle size impact on electrode properties, the electronic and mechanical properties, as well as the electrode structure, are investigated. The electrochemical performance of the Li metal/graphite system is correlated with structure properties influenced by PSD.
Polysulfide Shuttle Suppression by Electrolytes with Low‐Density for High‐Energy Lithium–Sulfur Batteries
Authors: Weller Christine , Pampel Jonas , Dörfler Susanne , Althues Holger , Kaskel Stefan
Published: July 2019

A low‐density electrolyte composition is introduced for lithium–sulfur (Li–S) batteries with intrinsic and effective polysulfide shuttle suppression. Hexyl methyl ether (HME) is used in combination with 1,3‐dioxolane (DOL) as a solvent for the Li–S battery electrolyte. The choice of solvent limits the dissolution of polysulfides, leading to successful suppression of the parasitic polysulfide shuttle. Hence, high coulombic efficiencies of 98% can be obtained in coin cells for over 50 cycles. The impact of the specifically adapted electrolyte solvent is studied systematically by varying solvent combinations in order to enable the development of light innovative shuttle suppressing electrolytes. In contrast to concepts relying on hydrofluoro ether dilution, the presented electrolyte features a significantly reduced mass density at 2 m lithium bis(trifluoromethanesulfonylimide) (LiTFSI) conductive salt enabling significant weight reduction on the Li–S prototype cell level, thus, allowing energy densities up to 400 Wh kg−1.
Volatility forecasting with bivariate multifractal models
Authors: Liu Ruipeng , Demirer Riza , Gupta Rangan , Wohar Mark
Published: July 2019

This paper examines volatility linkages and forecasting for stock and foreign exchange markets from a novel perspective by utilizing a bivariate Markov‐switching multifractal model that accounts for possible interactions between stock and foreign exchange markets. Examining daily data from major advanced and emerging nations, we show that generalized autoregressive conditional heteroskedasticity models generally offer superior volatility forecasts for short horizons, particularly for foreign exchange returns in advanced markets. Multifractal models, on the other hand, offer significant improvements for longer horizons, consistently across most markets. Finally, the bivariate multifractal model provides superior forecasts compared to the univariate alternative in most advanced markets and more consistently for currency returns, while its benefits are limited in the case of emerging markets.
Experimental and analytical investigation on an automobile radiator with CuO/EG‐water based nanofluid as coolant
Authors: Maisuria Mahendra B. , Sonar Devendraprasad M. , Rathod Manish K. , Bhatt Manhar K.
Published: July 2019

In the present study, experimental and analytical thermal performance of automobile radiator using nanofluids is investigated and compared with performance obtained with conventional coolants. Effect of operating parameters and nanoparticle concentration on heat transfer rate are studied for water as well as CuO/EG‐water based nanofluid analytically. The results are presented in the form of graphs showing variations of net heat transfer rate for various coolant flow rate, air velocity, and source temperature for various CuO/EG‐water based nanofluids. Experimental results indicate that with the increase in coolant flow rate and air velocity, heat transfer rate increases, reaches maximum and then decreases. Experimental investigation of a radiator is carried out using CuO/EG‐water based nanofluids. Results obtained by experimental work and analytical MATLAB code are almost the same. Maximum absolute error in water and air side is within 12% for all flow condition and coolant fluids. Nusselt number of nanofluid is calculated using equation number 33[9]. The results obtained from experimental work using 0.2% volume CuO/EG‐water based nanofluids are compared with the results obtained from MATLAB code. The results show that the maximum error in the outlet temperature of the coolant and air is 12% in each case. Thus MATLAB code can be used for different concentration of nanofluids to study the effect of operating parameters on heat transfer rate. Thus MATLAB code developed is valid for given heat exchanger applications. From the results obtained by already validated MATLAB code, it is concluded that increase in coolant flow rate, air velocity, and source temperature increases the heat transfer rate. Addition of nanoparticles in the base fluid increases the heat transfer rate for all kind of base fluids. Among all the nanofluid analyzed in this study, water‐based nanofluid gives highest value of heat transfer rate and is recommended for the heat exchanger applications under normal operating conditions. Maximum enhancement is observed for ethylene glycol‐water (4:6) mixture for 1% volume concentration of CuO is almost equal to 20%. As heat transfer rate increases with the use of nanofluids, the heat transfer area of the radiator can be minimized.
Modeling the effective thermal conductivity of nanofluids using full factorial design analysis
Authors: Grine Wassila , Benhamza Mohamed E. H.
Published: July 2019

In this paper, a full factorial design analysis is proposed for predicting nanofluid thermal conductivity ratio (TCR) as well as determining the effects of critical factors and their interactions. A statistical design of experiment approach with three variables (volume fraction, temperature, and nanoparticle diameter) at two levels is carried out. Three types of oxide‐water nanofluids (Al2O3‐water, CuO‐water, and TiO2‐water) are used to evaluate the effectiveness of the proposed mathematical model. The significance and adequacy of the regression model were evaluated by the analysis of variance. The predicted model has a root mean square error equals to 0.0074, R2 = 0.99, and P < .0013, thus showing good results compared to a set of experimental data as well as other mathematical model results. The results illustrate that the TCR of metallic oxide nanoﬂuids increases with temperature and nanoparticles volume fraction but decreases when nanoparticle size intensiﬁes. Furthermore, it is found that the nanoparticles volume fraction has a great impact on the nanoﬂuids thermophysical properties. Finally, the obtained results confirm that the proposed model is considerably accurate and capable of predicting nanoﬂuids thermal conductivity and that it can be used with ease as an alternative to many other models.
Establishment of a hepatocellular carcinoma patient‐derived xenograft platform and its application in biomarker identification
Authors: Hu Bo , Li Hong , Guo Wei , Sun Yun‐Fan , Zhang Xin , Tang Wei‐Guo , Yang Liu‐Xiao , Xu Yang , Tang Xiao‐Yan , Ding Guo‐Hui , Qiu Shuang‐Jian , Zhou Jian , Li Yi‐Xue , Fan Jia , Yang Xin‐Rong
Published: July 2019

Using a method optimized in hepatocellular carcinoma (HCC), we established patient‐derived xenograft (PDX) models with an increased take rate (42.2%) and demonstrated that FBS +10% dimethyl sulfoxide exhibited the highest tumor take rate efficacy. Among 254 HCC patients, 103 stably transplantable xenograft lines that could be serially passaged, cryopreserved and revived were established. These lines maintained the diversity of HCC and the essential features of the original specimens at the histological, transcriptome, proteomic and genomic levels. Tumor engraftment was associated with lack of encapsulation, poor tumor differentiation, large size and overexpression of cancer stem cell biomarkers, and was an independent predictor for overall survival and tumor recurrence after resection. To confirm the preclinical value of the PDX model in HCC treatment, several antitumor agents were tested in 16 selected PDX models. The results revealed a high degree of pharmacologic heterogeneity in the cohort, as well as heterogeneity to different agents in the same individual. The sorafenib responses observed between HCC patients and the corresponding PDXs were also consistent. After molecular characterization of the PDX models, we explored the predictive markers for sorafenib response and found that mitogen‐activated protein kinase kinase kinase 1 (MAP3K1) might play an important role in sorafenib resistance and sorafenib response is impaired in patients with MAP3K1 downexpression. Our results indicated that PDX models could accurately reproduce patient tumors biology and could aid in the discovery of new treatments to advance in precision medicine.
Analyzing credit risk transmission to the nonfinancial sector in Europe: A network approach
Authors: Gross Christian , Siklos Pierre L.
Published: July 2019

We use a factor model and elastic net shrinkage to model a high‐dimensional network of European credit default swap (CDS) spreads. Our empirical approach allows us to assess thejointtransmission of bank and sovereign risk to the nonfinancial corporate sector. Our findings identify a sectoral clustering in the CDS network, where financial institutions are in the center and nonfinancial entities as well as sovereigns are grouped around the financial center. The network has a geographical component reflected in different patterns of real‐sector risk transmission across countries. Our framework also provides dynamic estimates of risk transmission, a useful tool for systemic risk monitoring.
MicroRNA‐140 inhibit prostate cancer cell invasion and migration by targeting YES proto‐oncogene 1
Authors: Zhao Shijia , Jie Chuanling , Xu Pengchao , Diao Yan
Published: July 2019

Prostate cancer (PCa), which is an aggressive malignancy of the male genitourinary system. In the present study, the effects of microRNA‐140 (miR‐140) on PCa were determined. We transfected miR‐140 mimics or negative control into PCa cells, and we used MTT, wound healing, and Transwell assays for determining the capacities of miR‐140 in cell proliferation, migration, and invasion, respectively. We also confirmed the relationship between miR‐140 and YES proto‐oncogene 1 (YES1) using Luciferase reporter assay. The results showed that miR‐140 was downregulated in PCa cells and tissues, and overexpression of miR‐140 could significantly suppress their capacities of proliferation, migration, and invasion. Moreover, YES1 was shown to be a direct target of miR‐140. Moreover, miR‐140 expression is negatively correlated with YES1 levels. miR‐140 exhibits significant tumor‐suppressive effects in PCa by inhibiting YES1. The study indicated that miR‐140 and YES1 could be the potential targets for PCa therapy.
Glutathione peroxidase 3 (GPX3) suppresses the growth of melanoma cells through reactive oxygen species (ROS)‐dependent stabilization of hypoxia‐inducible factor 1‐α and 2‐α
Authors: Yi Zihan , Jiang Lu , Zhao Lei , Zhou Meiling , Ni Yueli , Yang Yuye , Yang Huixin , Yang Lijuan , Zhang Qiao , Kuang Yingmin , Deng Mingjia , Zhu Yuechun
Published: July 2019

In this study, we aimed to explore the mechanism of glutathione peroxidase 3 (GPX3) in the growth of malignant melanoma (MM) cells by hypoxia‐inducible factor‐1α (HIF1‐α) and HIF2‐α regulating the metabolism through reactive oxygen species (ROS). The messenger RNA and protein expression of GPX3, HIF1‐α, HIF2‐α in tissues, and cell lines were measured by reverse transcription‐quantitative PCR and Western blot analysis. A375 cells were transfected with GPX3 overexpression plasmid, small interfering RNA (siRNA) targeting GPX3, or siRNA targeting HIF1‐α/HIF2‐α to upregulate or downregulate the expression of GPX3 or HIF1‐α/HIF2‐α. The effects of H2O2 and N‐acetylcysteine (NAC) on the levels of HIF1‐α and HIF2‐α after overexpression of GPX3 were studied. The cell viability was detected by Cell Counting Kit‐8. The levels of ROS, glucose uptake and lactic acid production, oxidative phosphorylation, and glycolysis of cells were measured for assessment of cellular metabolism. The expression of GPX3 decreased, while ROS, HIF1‐α, and HIF2‐α increased in MM tissues and cells. Overexpression of GPX3 inhibited the viability of MM cells and the growth of melanoma xenografts. The overexpression of GPX3 reduced the glucose uptake, extracellular lactic acid content, and extracellular acidification rate and increased the oxygen consumption rate level. Overexpression of GPX3 could reduce the levels of HIF1‐α and HIF2‐α, which could regulate metabolic levels. GPX3 reduced ROS level in MM to inhibit HIF1‐α and HIF2‐α. The addition of H2O2 increased while NAC reduced the protein levels of HIF1‐α and HIF2‐α in the cells overexpressing GPX3. Our study demonstrates that GPX3 inhibits the growth of MM cells through its inhibitory effect on cell metabolic disorder by inhibiting HIF1‐α via regulating ROS.