bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Numerical Study of Atmospheric Perturbations Induced by Heat From a Wildland Fire: Sensitivity to Vertical Canopy Structure and Heat Source Strength
Authors: Kiefer Michael T. , Zhong Shiyuan , Heilman Warren E. , Charney Joseph J. , Bian Xindi 
Published: February 2018

AbstractAn improved understanding of atmospheric perturbations within and above a forest during a wildland fire has relevance to many aspects of wildland fires including fire spread, smoke transport and dispersion, and tree mortality. In this study, the ARPS‐CANOPY model, a version of the Advanced Regional Prediction System (ARPS) model with a canopy parameterization, is utilized in a series of idealized numerical experiments to investigate the influence of vertical canopy structure on the atmospheric response to a stationary sensible heat flux at the ground (“fire heat flux”), broadly consistent in magnitude with the sensible heat flux from a low‐intensity surface fire. Five vertical canopy structures are combined with five fire heat flux magnitudes to yield a matrix of 25 simulations. Analyses of the fire‐heat‐flux‐perturbed u component of the wind, vertical velocity, kinetic energy, and temperature show that the spatial pattern and magnitude of the perturbations are sensitive to vertical canopy structure. Both vertical velocity and kinetic energy exhibit an increasing trend with increasing fire heat flux that is stronger for cases with some amount of overstory vegetation than cases with exclusively understory vegetation. A weaker trend in cases with exclusively understory vegetation indicates a damping of the atmospheric response to the sensible heat from a surface fire when vegetation is most concentrated near the surface. More generally, the results presented in this study suggest that canopy morphology should be considered when applying the results of a fire‐atmosphere interaction study conducted in one type of forest to other forests with different canopy structures.
Seasonal Dynamics of Dissolved Methane in Lakes of the Mackenzie Delta and the Role of Carbon Substrate Quality
Authors: Cunada C. L. , Lesack L. F. W. , Tank S. E. 
Published: February 2018

AbstractDissolved CH4 among lake waters of the Mackenzie River Delta was tracked in 2014 to assess how river‐to‐lake connection times, plus carbon substrate quantity and quality, affects the patterns and dynamics of CH4. An under‐ice survey of 29 lakes, three open‐water surveys of 43 lakes, and weekly surveys of 6 lakes revealed that CH4 among lake‐waters ranged from very high concentrations at the end of winter, with highest concentrations linked to shortest annual river connection times, to considerably lower concentrations as open water progressed, with a limited concentration range among lakes by late summer. Lakes most strongly affected by thermokarst varied irregularly from this pattern and did not have the highest CH4 concentrations. CH4 among lake waters was generally related to measures of carbon substrate quantity, where relations with macrophyte biomass and dissolved organic carbon in lake water were statistically stronger than % organic matter within the lake sediments. CH4 was also directly related to the molecular weight (a[250]:a[365]) of dissolved organic matter at the end of winter, but was inversely related to this measure during open water. Carbon quality per se, after accounting for differences in carbon quantity (macrophyte biomass, dissolved organic carbon concentrations, or organic content of lake sediments), appears to play a significant role in controlling CH4 concentrations among the lake waters, particularly during winter ice cover. Carbon quality in lake sediments and of dissolved organic matter in winter lake waters appears to be as important as thermokarst augmentation of carbon quantity for enhancing methanogenesis in this lake‐rich Arctic system.
Hurricane Impact on Seepage Water in Larga Cave, Puerto Rico
Authors: Vieten Rolf , Warken Sophie , Winter Amos , Schröder‐Ritzrau Andrea , Scholz Denis , Spötl Christoph 
Published: February 2018

AbstractHurricane‐induced rainfall over Puerto Rico has characteristic δ18O values which are more negative than local rainfall events. Thus, hurricanes may be recorded in speleothems from Larga cave, Puerto Rico, as characteristic oxygen isotope excursions. Samples of 84 local rainfall events between 2012 and 2013 ranged from −6.2 to +0.3‰, whereas nine rainfall samples belonging to a rainband of hurricane Isaac (23–24 August 2012) ranged from −11.8 to −7.1‰. Cave monitoring covered the hurricane season of 2014 and investigated the impact of hurricane rainfall on drip water chemistry. δ18O values were measured in cumulative monthly rainwater samples above the cave. Inside the cave, δ18O values of instantaneous drip water samples were analyzed and drip rates were recorded at six drip sites. Most effective recharge appears to occur during the wet months (April–May and August–November). δ18O values of instantaneous drip water samples ranged from −3.5 to −2.4‰. In April 2014 and April 2015 some drip sites showed more negative δ18O values than the effective rainfall (−2.9‰), implying an influence of hurricane rainfall reaching the cave via stratified seepage flow months to years after the event. Speleothems from these drip sites in Larga cave have a high potential for paleotempestology studies.
Molecular Genetics of Parkinsonism
Authors: Lesage Suzanne , Brice Alexis 
Published: February 2018

Abstract

Over the past decade, genetic causes of parkinsonism have been elucidated, but they account in most populations, for less than 10% of the cases. Since the discovery of the first gene responsible for Parkinson disease (PD),
SCNA
encoding α‐synuclein, linkage mapping and positional cloning have identified autosomal dominantly or recessively inherited PD‐causing mutations in the genes encoding
parkin
,
PINK1
,
DJ‐1
,
LRRK2
and
ATP13A2
, indicating that PD has a highly heterogeneous aetiology. With the introduction of next‐generation sequencing, rare mutations in
DNAJC6
,
SYNJ1
,
VPS13C
,
VPS35
,
DNAJC13
,
TMEM230
and
CHCHD2
were then discovered to cause inherited parkinsonism. In addition, genetic studies from candidate genes, to unbiased genome‐wide approaches including association and next‐generation sequencing have nominated a number of disease determinants. In this article, we will highlight the current progress and future prospects in the field of PD genetics, since 2010.

Key Concepts

The introduction of next‐generation sequencing technologies associated with exome/genome sequencing has accelerated the discovery of novel causative genes and susceptibility factors in numerous Mendelian disorders.

Integrative approaches combining DNA sequencing with gene expression and methylome data will support and accelerate the identification and functional characterisation of the biological variants and disease genes.

Deep and accurate patient phenotyping is of major importance for the success of gene identification in heterogeneous diseases.

The use of larger and more homogeneous cohorts (endophenotype) will increase the chances of identifying high/intermediate risk variants in whole exome/whole genome sequencing.

Identification of additional PD and parkinsonism‐associated genes will enable further elucidation of the disease mechanisms and the development of disease‐modifying therapeutic strategies.

Meta‐analysis of many genome‐wide association studies improves the power to detect more associations and to investigate the consistency or heterogeneity of these associations across diverse datasets and study populations.
Biomedical Applications of Recombinant Silk‐Based Materials
Authors: Aigner Tamara Bernadette , DeSimone Elise , Scheibel Thomas 
Published: February 2018

AbstractSilk is mostly known as a luxurious textile, which originates from silkworms first cultivated in China. A deeper look into the variety of silk reveals that it can be used for much more, in nature and by humanity. For medical purposes, natural silks were recognized early as a potential biomaterial for surgical threads or wound dressings; however, as biomedical engineering advances, the demand for high‐performance, naturally derived biomaterials becomes more pressing and stringent. A common problem of natural materials is their large batch‐to‐batch variation, the quantity available, their potentially high immunogenicity, and their fast biodegradation. Some of these common problems also apply to silk; therefore, recombinant approaches for producing silk proteins have been developed. There are several research groups which study and utilize various recombinantly produced silk proteins, and many of these have also investigated their products for biomedical applications. This review gives a critical overview over of the results for applications of recombinant silk proteins in biomedical engineering.
Breaking the Current‐Retention Dilemma in Cation‐Based Resistive Switching Devices Utilizing Graphene with Controlled Defects
Authors: Zhao Xiaolong , Ma Jun , Xiao Xiangheng , Liu Qi , Shao Lin , Chen Di , Liu Sen , Niu Jiebin , Zhang Xumeng , Wang Yan , Cao Rongrong , Wang Wei , Di Zengfeng , Lv Hangbing , Long Shibing , Liu Ming 
Published: February 2018

AbstractCation‐based resistive switching (RS) devices, dominated by conductive filaments (CF) formation/dissolution, are widely considered for the ultrahigh density nonvolatile memory application. However, the current‐retention dilemma that the CF stability deteriorates greatly with decreasing compliance current makes it hard to decrease operating current for memory application and increase driving current for selector application. By centralizing/decentralizing the CF distribution, this current‐retention dilemma of cation‐based RS devices is broken for the first time. Utilizing the graphene impermeability, the cation injecting path to the RS layer can be well modulated by structure‐defective graphene, leading to control of the CF quantity and size. By graphene defect engineering, a low operating current (≈1 µA) memory and a high driving current (≈1 mA) selector are successfully realized in the same material system. Based on systematically materials analysis, the diameter of CF, modulated by graphene defect size, is the major factor for CF stability. Breakthrough in addressing the current‐retention dilemma will instruct the future implementation of high‐density 3D integration of RS memory immune to crosstalk issues.
Nanomaterials Safer‐by‐Design: An Environmental Safety Perspective
Authors: Lin Sijie , Yu Tianyu , Yu Zhenyang , Hu Xialin , Yin Daqiang 
Published: February 2018

AbstractDesigning safer nanomaterials and nanostructures has gained increasing attention in the field of nanoscience and technology in recent years. Based on the body of experimental evidence contributed by environmental health and safety studies, materials scientists now have a better grasp on the relationships between the nanomaterials' physicochemical characteristics and their hazard/safety profiles. Therefore, it is expected that an integration of design synthesis and safety assessment will foster nanomaterials safer‐by‐design by considering both applications and implications. From the environmental safety perspective, the most recent advances that demonstrate effective nanomaterials safer‐by‐design are highlighted.
Preferential Charge Generation at Aggregate Sites in Narrow Band Gap Infrared Photoresponsive Polymer Semiconductors
Authors: Sulas Dana B. , London Alexander E. , Huang Lifeng , Xu Lihua , Wu Zhenghui , Ng Tse Nga , Wong Bryan M. , Schlenker Cody W. , Azoulay Jason D. , Sfeir Matthew Y. 
Published: February 2018

AbstractInfrared organic photodetector materials are investigated using transient absorption spectroscopy, demonstrating that ultrafast charge generation assisted by polymer aggregation is essential to compensate for the energy gap law, which dictates that excited state lifetimes decrease as the band gap narrows. Short sub‐picosecond singlet exciton lifetimes are measured in a structurally related series of infrared‐absorbing copolymers that consist of alternating cyclopentadithiophene electron‐rich “push” units and strong electron‐deficient “pull” units, including benzothiadiazole, benzoselenadiazole, pyridalselenadiazole, or thiadiazoloquinoxaline. While the ultrafast lifetimes of excitons localized on individual polymer chains suggest that charge carrier generation will be inefficient, high detectivity for polymer:PC71BM infrared photodetectors is measured in the 0.6 < λ < 1.5 µm range. The photophysical processes leading to charge generation are investigated by performing a global analysis on transient absorption data of blended polymer:PC71BM films. In these blends, charge carriers form primarily at polymer aggregate sites on the ultrafast time scale (within our instrument response), leaving quickly decaying single‐chain excitons unquenched. The results have important implications for the further development of organic infrared optoelectronic devices, where targeting processes such as excited state delocalization over aggregates may be necessary to mitigate losses to ultrafast exciton decay as materials with even lower band gaps are developed.
Hydroaminomethylation in Aqueous Solvent Systems – An Efficient Pathway to Highly Functionalized Amines
Authors: Faßbach Thiemo A. , Sommer Fridolin O. , Vorholt Andreas J. 
Published: February 2018

AbstractTandem‐catalyzed hydroaminomethylation is a useful tool for synthesizing linear amines from olefins and amines in an atom‐efficient manner. To enable the coupling of highly functionalized, hydrosoluble amines with non‐water‐soluble olefins, this reaction must be transferred to aqueous biphasic solvent systems. In this work, we systematically evaluate reaction conditions to provide a selective hydroaminomethylation of 1‐octene with diethanolamine as model substrates. Although water is both the condensation side product and the solvent, yields of 79% were achieved using a catalytic system consisting a rhodium precursor and a sulfonated diphosphine ligand. This approach was applied to other functionalized amines, proving this concept is a suitable tool for the catalytic alkylation of highly functionalized amines.magnified image
Characterization of the Valence and Conduction Band Levels of n = 1 2D Perovskites: A Combined Experimental and Theoretical Investigation
Authors: Silver Scott , Yin Jun , Li Hong , Brédas Jean‐Luc , Kahn Antoine 
Published: February 2018

AbstractThis study presents a combined experimental and theoretical study of the electronic structure of two 2D metal halide perovskite films. Ultraviolet and inverse photoemission spectroscopies are performed on solution‐processed thin films of the n = 1 layered perovskite butylammonium lead iodide and bromide, BA2PbI4 and BA2PbBr4, characterized by optical absorption and X‐ray diffraction, to determine their valence and conduction band densities of states, transport gaps, and exciton binding energies. The electron spectroscopy results are compared with the densities of states determined by density functional theory calculations. The remarkable agreement between experiment and calculation enables a detailed identification and analysis of the organic and inorganic contributions to the valence and conduction bands of these two hybrid perovskites. The electron affinity and ionization energies are found to be 3.1 and 5.8 eV for BA2PbI4, and 3.1 and 6.5 eV for BA2PbBr4. The exciton binding energies are estimated to be 260 and 300 meV for the two materials, respectively. The 2D lead iodide and bromide perovskites exhibit significantly less band dispersion and a larger density of states at the band edges than the 3D analogs. The effects of using various organic ligands are also discussed.
Mitigation of Inflammatory Immune Responses with Hydrophilic Nanoparticles
Authors: Li Bowen , Xie Jingyi , Yuan Zhefan , Jain Priyesh , Lin Xiaojie , Wu Kan , Jiang Shaoyi 
Published: February 2018

AbstractWhile hydrophobic nanoparticles (NPs) have been long recognized to boost the immune activation, whether hydrophilic NPs modulate an immune system challenged by immune stimulators and how their hydrophilic properties may affect the immune response is still unclear. To answer this question, three polymers, poly(ethylene glycol) (PEG), poly(sulfobetaine) (PSB) and poly(carboxybetaine) (PCB), which are commonly considered hydrophilic, are studied in this work. For comparison, nanogels with uniform size and homogeneous surface functionalities were made from these polymers. Peripheral blood mononuclear cells (PBMCs) stimulated by lipopolysaccharide (LPS) and an LPS‐induced lung inflammation murine model were used to investigate the influence of nanogels on the immune system. Results show that the treatment of hydrophilic nanogels attenuated the immune responses elicited by LPS both in vitro and in vivo. Moreover, we found that PCB nanogels, which have the strongest hydration and the lowest non‐specific protein binding, manifested the best performance in alleviating the immune activation, followed by PSB and PEG nanogels. This reveals that the immunomodulatory effect of hydrophilic materials is closely related to their hydration characteristics and their ability to resist non‐specific binding in complex media.
Heteroleptic Copper(I)‐Based Complexes for Photocatalysis: Combinatorial Assembly, Discovery, and Optimization
Authors: Minozzi Clémentine , Caron Antoine , Grenier‐Petel Jean‐Christophe , Santandrea Jeffrey , Collins Shawn K. 
Published: February 2018

AbstractA library of 50 copper‐based complexes derived from bisphosphines and diamines was prepared and evaluated in three mechanistically distinct photocatalytic reactions. In all cases, a copper‐based catalyst was identified to afford high yields, where new heteroleptic complexes derived from the bisphosphine BINAP displayed high efficiency across all reaction types. Importantly, the evaluation of the library of copper complexes revealed that even when photophysical data is available, it is not always possible to predict which catalyst structure will be efficient or inefficient in a given process, emphasizing the advantages for catalyst structures with high modularity and structural variability.
Thermally Rearranged Polymer Membranes Containing Tröger's Base Units Have Exceptional Performance for Air Separations
Authors: Meckler Stephen M. , Bachman Jonathan E. , Robertson Benjamin P. , Zhu Chenhui , Long Jeffrey R. , Helms Brett A. 
Published: February 2018

AbstractThe influence of segmental chain motion on the gas separation performance of thermally rearranged (TR) polymer membranes is established for TR polybenzoxazoles featuring Tröger's base (TB) monomer subunits as exceptionally rigid sites of contortion along the polymer backbone. These polymers are accessed from solution‐processable ortho‐acetate functionalized polyimides, which are readily synthesized as high‐molecular‐weight polymers for membrane casting. We find that thermal rearrangement leads to a small increase in d‐spacing between polymer chains and a dramatic pore‐network reconfiguration that increases both membrane permeability and O2/N2 selectivity, putting its performance above the 2015 upper bound.
Solid‐Solution Alloy Nanoparticles of the Immiscible Iridium–Copper System with a Wide Composition Range for Enhanced Electrocatalytic Applications
Authors: Wang Fenglong , Kusada Kohei , Wu Dongshuang , Yamamoto Tomokazu , Toriyama Takaaki , Matsumura Syo , Nanba Yusuke , Koyama Michihisa , Kitagawa Hiroshi 
Published: February 2018

AbstractFor the first time, we synthesize solid‐solution alloy nanoparticles of Ir and Cu with a size of ca. 2 nm, despite Ir and Cu being immiscible in the bulk up to their melting over the whole composition range. We performed a systematic characterization on the nature of the IrxCu1−x solid‐solution alloys using powder X‐ray diffraction, scanning transmission electron microscopy coupled with energy‐dispersive X‐ray spectroscopy and X‐ray photoelectron spectroscopy. The results showed that the IrxCu1−x alloys had a face‐centered‐cubic structure; charge transfer from Cu to Ir occurred in the alloy nanoparticles, as the core‐level Ir 4f peaks shifted to lower energy region with the increase in Cu content. Furthermore, we observed that the alloying of Ir with Cu enhanced both the electrocatalytic oxygen evolution and oxygen reduction reactions. The enhanced activities could be attributed to the electronic interaction between Ir and Cu arising from the alloying effect at atomic‐level.
Catalytic Enantioselective Aza‐Benzoin Reactions of Aldehydes with 2H‐Azirines
Authors: Peng Qiupeng , Guo Donghui , Bie Jianbo , Wang Jian 
Published: February 2018

AbstractThe unprecedented enantioselective aza‐benzoin reaction of aldehydes with 2H‐azirines was developed by utilizing a chiral N‐heterocyclic carbene as the catalyst. A wide range of corresponding aziridines can be obtained in good yields with high enantioselectivities. The obtained optically active aziridines should be useful in the synthesis of other valuable molecules.
Nucleophilic Activation of Sulfur Hexafluoride: Metal‐Free, Selective Degradation by Phosphines
Authors: Buß Florenz , Mück‐Lichtenfeld Christian , Mehlmann Paul , Dielmann Fabian 
Published: February 2018

AbstractThe development of new methods for the chemical activation of the extremely inert greenhouse gas sulfur hexafluoride (SF6) not only is of current environmental interest, but also offers new opportunities for applications of SF6 as a reagent in organic synthesis. We herein report the first nucleophilic activation of SF6 by Lewis bases, namely by phosphines, which results either in its complete degradation to phosphine sulfides and difluorophosphoranes or in the selective conversion of SF6 into a bench‐stable, crystalline salt containing the SF5− anion. Quantum chemical calculations reveal a nucleophilic substitution mechanism (SN2) for the initial fluorine abstraction from SF6 by the phosphine. Furthermore, a scalable one‐pot procedure for the complete decomposition of SF6 into solid, nonvolatile products is presented based on cheap and commercially available starting materials.
Calcium carbonate and wood reinforced hybrid PVC composites
Authors: Croitoru Catalin , Spirchez Cosmin , Cristea Daniel , Lunguleasa Aurel , Pop Mihai Alin , Bedo Tibor , Roata Ionut Claudiu , Luca Mihai Alexandru 
Published: February 2018

ABSTRACTIn this article, poly(vinyl chloride) (PVC) sandwich‐structured hybrid composites with amorphous calcium carbonate and wood‐filled cores were obtained by compression molding. It has been determined that wood addition up to a weight ratio of 33% reported to the total filler amount is beneficial in improving both the inter‐filler and filler‐matrix interfacial adhesion, which alongside with the promoting of the amorphous PVC matrix crystallization is responsible for an increase up to 34% in the flexural strength of the composites, compared to unfilled PVC. The hybrid filled composites present up to 35% lower friction coefficients and up to 20% higher Brinell hardness values than the composites filled with calcium carbonate alone. Subsequently, wood addition determines an increase in the oxidation onset temperature for PVC and an increase with up to 20% in the sound and thermal‐insulative properties of the composites, compared to unfilled PVC. The dominating dispersive part of the composites surface energy aids in improving the mass and dimensional stability of the assembly to both water and dilute hydrochloric acid aqueous solutions. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46317.