bluuebunny/crossref_metadata_2025 huggingface dataset:
Enantioconvergent Cross‐Couplings of Alkyl Electrophiles: The Catalytic Asymmetric Synthesis of Organosilanes
Authors: Schwarzwalder Gregg M. , Matier Carson D. , Fu Gregory C.
Published: January 2019

Metal‐catalyzed enantioconvergent cross‐coupling reactions of alkyl electrophiles are emerging as a powerful tool in asymmetric synthesis. To date, high enantioselectivity has been limited to couplings of electrophiles that bear a directing group or a proximal p/π orbital. Herein, we demonstrate for the first time that enantioconvergent cross‐couplings can be achieved with electrophiles that lack such features; specifically, we establish that a chiral nickel catalyst can accomplish Negishi reactions of racemic α‐halosilanes with alkylzinc reagents with good enantioselectivity under simple and mild conditions, thereby providing access to enantioenriched organosilanes, an important class of target molecules.
Visual Chemical Detection Mechanism by a Liquid Gating System with Dipole‐Induced Interfacial Molecular Reconfiguration
Authors: Fan Yi , Sheng Zhizhi , Chen Jun , Pan Hong , Chen Baiyi , Wu Feng , Wang Shuli , Chen Xinyu , Hou Xu
Published: January 2019

Chemical detection has a wide range of applications. The detection of a certain substance is so vital that new detection mechanisms with features such as low‐cost, accessibility, and readily available visual markers are in demand. Herein, a liquid‐gating‐based chemical‐detection mechanism is reported, which has a dynamic gas/liquid interface due to dipole‐induced interfacial molecular reconfiguration. The mechanism exhibits a sensitive relationship between the dipole‐force‐induced rearrangement of interfacial molecules and transmembrane gating behavior. These features can be utilized to create visual markers for detection by converting the analyte‐mediated interfacial interaction to a pressure‐driven marker movement. This “green” detection mechanism requires no electrical energy input and has readily available markers for anyone to observe directly. This new mechanism opens a window for a more in‐depth exploration of combining liquid‐gating mechanisms with detection mechanisms.
Accessing Ambiphilic Phosphine Boronates through C−H Borylation by an Unforeseen Cationic Iridium Complex
Authors: Wright Shawn E. , Richardson‐Solorzano Stephanie , Stewart Tiffany N. , Miller Christopher D. , Morris Kelsey C. , Daley Christopher J. A. , Clark Timothy B.
Published: January 2019

Ambiphilic molecules, which contain a Lewis base and Lewis acid, are of great interest based on their unique ability to activate small molecules. Phosphine boronates are one class of these substrates that have interesting catalytic activity. Direct access to these phosphine boronates is described through the iridium‐catalyzed C−H borylation of phosphines. An unconventional cationic iridium catalyst was identified as optimal for a range of phosphines, providing good yields and selectivity across a diverse class of phosphine boronates (isolated as the borane‐protected phosphine). A complimentary catalyst system (quinoline‐based silane ligand with [(COD)IrOMe]2) was optimal for biphenyl‐based phosphines. Selective polyborylation was also shown providing bis‐ and tris‐borylated phosphines. Deprotection of the phosphine boronate provided free ambiphilic phosphine boronates, which do not have detectable interactions between the phosphorus and boron atoms in solution or the solid state.
Aluminum(I)/Boron(III) Redox Reactions
Authors: Hofmann Alexander , Pranckevicius Conor , Tröster Tobias , Braunschweig Holger
Published: January 2019

Reactions between BIII species and the novel nucleophilic cyclopentadienyl‐stabilized AlI reagent (1) result in a diversity of complexes bearing different Al/B oxidation states and coordination geometries. With the triarylborane B(C6F5)3, a simple AlI→BIII adduct is formed. In contrast, a bulky aryldihaloborane undergoes oxidative addition with the formation of a covalent bora‐alane species. With an N‐heterocyclic carbene‐stabilized amino(bromo)borenium ion, a redox reaction was observed, where the product is a borylene‐alane BI→AlIII complex. Additionally, reaction of 1 with BI3 results in complete scrambling of all of the Al/B‐bound substituents, and the formation of a cyclopentadienylboron(I)→AlI3 complex. These latter reactions are the first examples of the reduction of a boron(III) compound to a borylene by a p‐block reagent, and illustrate how subtle changes in the nature of the borane can result in highly divergent reaction outcomes.
Hydrogen‐Bond‐Enabled Dynamic Kinetic Resolution of Axially Chiral Amides Mediated by a Chiral Counterion
Authors: Fugard Alison J. , Lahdenperä Antti S. K. , Tan Jaqueline S. J. , Mekareeya Aroonroj , Paton Robert S. , Smith Martin D.
Published: January 2019

Non‐biaryl atropisomers are valuable in medicine, materials, and catalysis, but their enantioselective synthesis remains a challenge. Herein, a counterion‐mediated O‐alkylation method for the generation of atropisomeric amides with an er up to 99:1 is outlined. This dynamic kinetic resolution is enabled by the observation that the rate of racemization of atropisomeric naphthamides is significantly increased by the presence of an intramolecular O−H⋅⋅⋅NCO hydrogen bond. Upon O‐alkylation of the H‐bond donor, the barrier to rotation is significantly increased. Quantum calculations demonstrate that the intramolecular H‐bond reduces the rotational barrier about the aryl–amide bond, stabilizing the planar transition state for racemization by approximately 40 kJ mol−1, thereby facilitating the observed dynamic kinetic resolution.
Chlorine‐resistant and internal‐concentration‐polarization‐mitigated polyamide membrane via tethering poly(ethylene glycol) methacrylate
Authors: Chen Qing , Sun Fei , Zhou Jin , Lu Yao , Li Yuan‐Yuan , Yu Hai‐Yin , Gu Jia‐Shan
Published: January 2019

To improve chlorine resistance and mitigate the internal concentration polarization (ICP), a membrane surface was tethered with poly(ethylene glycol) methacrylate (PEGMA). Characterization by attenuated total reflection–Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy analysis, and field emission scanning electron microscopy indicated the successful tethering of PEGMA onto the membrane. The antifouling and antichlorine characteristics were assessed in reverse osmosis (RO) and forward osmosis (FO) processes. The water flux increased obviously to 85.00 from 60.00 L m−2 h−1 (LMH) in the RO process; the chlorine stability of the modified membrane was improved. The greatly reduced structural parameters indicated that the ICP of the FO membrane was successfully alleviated; the water flux decreased greatly for the original membrane from 3.40 to 0.01 LMH, whereas it fell only slightly from 10.99 to 9.32 LMH for the modified membrane during synthetic sewage treatment. The ICP was greatly mitigated; the antichlorine performances and the antifouling characteristics drastically improved after grafting with PEGMA. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47406.
Low‐dielectric‐constant benzocyclobutene–organosilicon resins constructed from cyclotetrasiloxane
Authors: Huang Yawen , Zhang Quanli , Peng Qiuxia , Hu Huan , Yu Hongtao , Yang Junxiao , Liu Lili
Published: January 2019

Organosilicon resins have been demonstrated to be promising materials for low‐dielectric‐constant (low‐k) related applications. In this study, we proposed a method to further reduce the dielectric constant (k) value of organosilicon resins with [1,1‐dimethyl,1‐(4′‐benzocyclobutenyl)silyl] cyclotetrasiloxane (BCB‐D4) as a building block. This building block was prepared by the hydrosilylation reaction of tetravinyl cyclotetrasiloxane with dimethyl–benzocyclobutene–silane. The reaction of benzocyclobutene on BCB‐D4 by bulk polymerization in modules directly produced a highly crosslinked resin (poly{[1,1‐dimethyl,1‐(4′‐benzocyclobutenyl)silyl] cyclotetrasiloxane) [poly(BCB‐D4)]). Poly(BCB‐D4) exhibited a low k of about 2.70; this value was greatly lower than the k (~3.0) of conventional benzocyclobutene–organosilicon resins obtained by the curing of linear polysiloxane. The low k was possibly due to the porous structure, which was constructed from multifunctionalized and cyclic building blocks. In addition, poly(BCB‐D4) also exhibited a relatively high modulus (5.0 GPa) without a sacrifice in the thermal resistance. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47465.
Piezoelectric electrospun polyacrylonitrile with various tacticities
Authors: Street Reva M. , Minagawa Masatomo , Vengrenyuk Andriy , Schauer Caroline L.
Published: January 2019

Electrospinning of urea clathrate polymerized polyacrylonitrile (PAN) with isotacticity 25% and 52% was achieved in N,N‐dimethylformamide (DMF) at room temperature. Although the molecular weights of the 25% and 52% were found to be comparable by size exclusion chromatography, creation of uniform nanofibers with comparable diameters (average of ~450 nm) required concentrations of 5 % w/v and 3.5% w/v, respectively. X‐ray diffraction (XRD) analysis demonstrated that the polymer retained semicrystalline structure and suggested that crystallinity was correlated with increasing isotacticity. Fourier transform infrared spectroscopy (FTIR) also confirmed increased crystallinity as compared to commercially purchased free‐radical polymerized PAN due to a shift in the ~1250 cm−1 methine peak. Periodic semistatic normal load piezoelectric testing of the electrospun isotactic PAN samples also exhibited an average of ~30% of the piezoelectric response of electrospun (65:35) poly(vinylidene fluoride‐trifluoroethylene) (PVDF‐TrFE), a current gold standard for piezoelectric polymers, whereas commercially purchased free‐radical polymerized PAN exhibited no observable piezoelectric response. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47530.
Chemical Kinetic Strategies for High‐Throughput Screening of Protein Aggregation Modulators
Authors: Sárkány Zsuzsa , Rocha Fernando , Damas Ana M. , Macedo‐Ribeiro Sandra , Martins Pedro M.
Published: January 2019

Insoluble aggregates staining positive to amyloid dyes are known histological hallmarks of different neurodegenerative disorders and of type II diabetes. Soluble oligomers are smaller assemblies whose formation prior to or concomitant with amyloid deposition has been associated to the processes of disease propagation and cell death. While the pathogenic mechanisms are complex and differ from disease to disease, both types of aggregates are important biological targets subject to intense investigation in academia and industry. Here we review recent advances in the fundamental understanding of protein aggregation that can be used on the development of anti‐amyloid and anti‐oligomerization drugs. Specifically, we pinpoint the chemical kinetic aspects that should be attended during the development of high‐throughput screening assays and in the hit validation phase. The strategies here devised are expected to establish a connection between basic research and pharmaceutical innovation.
Tertiary Amines Differentiated from Primary and Secondary Amines by Active Ester‐Functionalized Hexabenzoperylene in Field Effect Transistors
Authors: Li Changqing , Wang Yujing , Zhang Tiankai , Zheng Bo , Xu Jianbin , Miao Qian
Published: January 2019

Herein, we report two novel derivatives of hexabenzoperylene (HBP) that are functionalized with ester groups. Methyl acetate functionalized HBP (1) in single crystals self‐assembles into a supramolecular nanosheet, which has a two‐dimensional π‐stack of HBP sandwiched between two layers of ester groups. With the same self‐assembly motif, active ester‐functionalized HBP (2) in field effect transistors has enabled differentiation of tertiary amines from primary and secondary amines, in agreement with the fact that active ester reacts with primary and secondary amines but not with tertiary amines to form amides.
Generation of “Sumanenylidene”: A Ground‐State Triplet Carbene on a Curved π‐Conjugated Periphery
Authors: Yakiyama Yumi , Wang Yufeng , Hatano Sayaka , Abe Manabu , Sakurai Hidehiro
Published: January 2019

We have observed the generation of sumanenylidene (2), a divalent, neutral‐carbon species at the benzylic position of sumanene (1). We also clarified both experimentally and theoretically that the ground state of compound 2 was a triplet state and that its singlet–triplet energy gap (ΔEST) was similar to that in fluorenylidene. The curved structure of compound 2 led to slightly better spin delocalization over the two adjacent aromatic rings than in planar systems, because of the unpaired spins on the σ and π orbitals. Synthetic application of the carbene precursor, diazosumanene (5), with a variety of thiocarbonyl compounds revealed its utility for the preparation of tetrasubstituted alkene compounds (e.g., that contain a strongly electron‐donating unit) that are directly conjugated to the sumanene (1) moiety.
A Series of Iodoargentates Directed by Solvated Metal Cations Featuring Uptake and Photocatalytic Degradation of Organic Dye Pollutants
Authors: Wei Qi , Wang Di , Pan Jie , Han Song‐De , Wang Guo‐Ming
Published: January 2019

By using solvated metal cations as structure‐directing agents, three new iodoargentates, namely, [Fe(DMSO)6][Ag6I9]⋅DMSO (1), [Fe(H2O)6][Ag15I18] (2) and [Cd(DMSO)6][Ag8I10] (3) (DMSO=dimethyl sulfoxide) have been solvothermally prepared and structurally characterized. The structures of compounds 1 and 2 can be described as 1D chains constructed from the linkage of [Ag6I9] and [Ag5I11] building units, respectively. For compound 3, the [Ag10I22] building blocks are directly interconnected to form a 2D [Ag8I10] layer, which are further interconnected via intermolecular forces to generate a 3D supramolecular framework with 1D large channels occupied by [Cd(DMSO)6]2+ cations. Interestingly, compounds 1–3 exhibit an ion‐exchange behavior for the adsorption of a specific dye (methylene blue, MB). Moreover, photocatalytic experiments indicate that these iodoargentates can be considered as promising photocatalysts for the degradation of organic dye pollutants.
St. Philips footbridge in Bristol
Authors: Beade‐Pereda Héctor , McElhinney John , Barbulescu Bogdan
Published: January 2019

The transformation of an area originally used for railway maintenance into a new neighbourhood in the city centre is one of the most important urban development projects being carried out in Bristol. The new St Philips footbridge spans the River Avon contributing to provide the needed accessibility for development to a site previously isolated by several infrastructures and the watercourse. The footbridge is an innovative solution to a complex crossing problem: the connection of two banks with a significant elevation and appearance difference and one of them being developed to high architectural standards faster than the other. The design should be appropriate for both immediate and medium‐term scenarios and to harmoniously coexist with the close existing bridges and the future buildings. The bridge is a 50m‐span and 4‐m wide steel beam with a forked geometry, hosting a ramp for disabled and cyclists and a staircase as part of its own structure to maximise functionality. The design approach to generate its shape was at the same time structural, aesthetical, and functional. Thanks to this holistic approach, the bridge is compact, simple, elegant and clearly legible for both footbridge and river path users.
Direct Imaging of Protein‐Specific Methylation in Mammalian Cells
Authors: Doll Franziska , Steimbach Raphael R. , Zumbusch Andreas
Published: January 2019

Abundant post‐translational modification through methylation alters the function, stability, and/or localization of a protein. Malfunctions in post‐translational modification are associated with severe diseases. To unravel protein methylation sites and their biological functions, chemical methylation reporters have been developed. However, until now, their usage was limited to cell lysates. Herein, we present the first generally applicable approach for imaging methylation of individual proteins in human cells, which is based on a combination of chemical reporter strategies, bioorthogonal ligation reactions, and FRET detected by means of fluorescence lifetime imaging microscopy. Through this approach, methylation of histone 4 and the non‐histone proteins tumor suppressor p53, kinase Akt1, and transcription factor Foxo1 in two human cell lines has been successfully imaged. To further demonstrate its potential, the localization‐dependent methylation state of Foxo1 in the cellular context has been visualized.
Catalytic Conversion of 1‐butene over Modified Versions of Commercial ZSM‐5 to Produce Clean Fuels and Chemicals
Authors: Silva Andreia F. , Fernandes Auguste , Antunes Margarida M. , Ribeiro Maria F. , Silva Carlos M. , Valente Anabela A.
Published: January 2019

The oligomerisation of light olefins, obtainable from fossil/renewable sources and refinery streams, is an attractive route to produce clean synthetic fuels and added‐value chemicals. ZSM‐5 is a type of catalyst used in commercial olefin oligomerisation processes. Using appropriate modification procedures, it was possible to prepare catalysts with improved performances. Various modified versions of commercially available ZSM‐5 were prepared and investigated for 1‐butene oligomerisation under high‐pressure, continuous‐flow operation (30 bar, 200 °C). Simple, up‐scalable top‐down strategies involving base‐acid treatments of ZSM‐5 led to catalysts possessing enlarged pores and the required acidity for converting 1‐butene to higher molar mass products. In targeting diesel type products, the modified catalysts led to up to 86 % butenes conversion, space time yield of 852 mg gcat−1 h−1 and mass ratio diesel:naphtha cuts of 2.2. Characterisation studies and multivariate/principal component analysis helped categorise the differently prepared catalysts, and gain insights into complex interplay of material properties influencing the catalytic reaction.
Synthesis of Nickel‐Doped Ceria Catalysts for Selective Acetylene Hydrogenation
Authors: Riley Christopher , De La Riva Andrew , Zhou Shulan , Wan Qiang , Peterson Eric , Artyushkova Kateryna , Farahani Majid D. , Friedrich Holger B. , Burkemper Laura , Atudorei Nicu‐Viorel , Lin Sen , Guo Hua , Datye Abhaya
Published: January 2019

Metallic nickel is known to be an active, but not a selective hydrogenation catalyst for conversion of alkynes to alkenes. On the other hand, nickel oxide is not active. Recently, we have demonstrated that nickel doped into ceria provides an inexpensive catalyst for selective hydrogenation of acetylene in the presence of ethylene. Here, we evaluate various synthesis methods to achieve optimal selective hydrogenation performance. We examined incipient wetness impregnation, coprecipitation, solution combustion, and sol‐gel synthesis to study how the method of preparation affects catalytic structure and behavior. Sol‐gel synthesis, coprecipitation, and solution combustion synthesis methods favor nickel incorporation into the ceria lattice, while incipient wetness impregnation creates segregated nickel species on the ceria surface. For hydrogenation of acetylene, these nickel surface species lead to poor ethylene selectivity due to ethane and oligomer formation. However, when nickel is incorporated into the ceria lattice, ethane formation is prevented even while achieving 100 % conversion of acetylene. Coke formation is also significantly reduced on these catalysts compared to conventional nanoparticle counterparts. We conclude that sol‐gel synthesis provides the optimal method for creating a uniform dopant distribution within the high surface area ceria.
Oxygen Vacancy Induced Structural Distortions in Black Titania: A Unique Approach using Soft X‐ray EXAFS at the O–K Edge
Authors: Leedahl Brett , de Boer Tristan , Yuan Xiaotao , Moewes Alexander
Published: January 2019

Unknown changes in the crystalline order of regular TiO2 result in the formation of black titania, which has garnered significant interest as a photocatalytic material due to the accompanying electronic changes. Herein, the nature of the lattice distortion caused by an oxygen vacancy was determined that in turn results in the formation of mid‐band‐gap states found in previous studies of black titania. An innovative technique is introduced using a state‐of‐the‐art silicon drift detector, which can be used in conjunction with extended X‐ray absorption fine structure (EXAFS) to measure bulk interatomic distances. Also discussed is how the energy dispersive nature of such a detector can allow for an unimpeded signal, indefinitely in energy space, thereby sidestepping the hurdles of more conventional EXAFS, which is often impeded by other absorption edges.
Exohedral Addition Chemistry of the Fullerenide Anions C602− and C60⋅−
Authors: Wabra Isabell , Holzwarth Johannes , Hauke Frank , Hirsch Andreas
Published: January 2019

A systematic screening study of the exohedral reactivity of the reduced fullerenes (fullerenides) C602− and C60⋅− is reported. These doubly and singly negatively charged carbon cages were prepared by two‐fold reduction of C60 with potassium, leading to K2C60, or by in situ monoreduction with the radical anion of benzonitrile PhCN⋅−, respectively. Several series of electrophiles, including geminal and distant dihalides, benzyl bromides, and diazonium compounds, were employed as addition partners. In general, the investigated bromides proved to be the most suitable reaction partners. A series of fullerene adducts and cycloadducts involving either 1,2‐ or 1,4‐addition patterns, depending on the precise architecture and the steric demand of the addends, were synthesized and fully characterized. Some of the reaction products are unprecedented and inaccessible forms of neutral C60. The fullerenide chemistry presented here closely resembles related reactions of graphenides and carbon nanotubides, which are the most powerful methods for the functionalization of these macromolecular forms of synthetic carbon allotropes (SCAs). Activation of C60 by negative charging represents a little explored concept of fullerene chemistry, providing both new insights of fullerene reactivity itself and new types of exohedral derivatives.
Anthracene‐Based Cyclophanes with Selective Fluorescent Responses for TTP and GTP: Insights into Recognition and Sensing Mechanisms
Authors: Agafontsev Aleksandr M. , Shumilova Tatiana A. , Rüffer Tobias , Lang Heinrich , Kataev Evgeny A.
Published: January 2019

Three anthracene‐based cyclophanes were synthesized and their binding properties towards nucleoside triphosphates were studied. A new polycyclic amine derived from dearomatized anthracene was identified as a major side product in the cyclization reaction between 9,10‐anthracenedicarboxaldehyde and diethylenetriamine. Its structure was determined by single‐crystal X‐ray analysis. The cyclophanes were found to form 1:1 complexes with all nucleoside triphosphates as well as with pyrophosphate in a buffered aqueous solution at pH 6.2. A turn‐on fluorescence response was observed for all nucleotides except for GTP, which demonstrated strong fluorescence quenching. The strongest turn‐on fluorescence was observed for the largest receptor 3 in the presence of thymidine triphosphate (TTP). Based on the NMR and fluorescence experiments, two major binding modes for nucleotide complexes were identified.
A Closed Metallomolecular Cage that can Open its Aperture by Disulfide Exchange
Authors: Akine Shigehisa , Miyashita Masato , Nabeshima Tatsuya
Published: January 2019

Invited for the cover of this issue is the group of Shigehisa Akine at Kanazawa University and Tatsuya Nabeshima at the University of Tsukuba. The image, designed by Prof. Akine, depicts a visualization of the possible “open” intermediate molecule that allows a guest to enter and exit. Read the full text of the article at 10.1002/chem.201805359.
Nonmosaic somatic HIF2A mutations associated with late onset polycythemia‐paraganglioma syndrome: Newly recognized subclass of polycythemia‐paraganglioma syndrome
Authors: Pang Ying , Gupta Garima , Jha Abhishek , Yue Xupeng , Wang Herui , Huynh Thanh‐Truc , Li Aiguo , Li Liping , Baker Eva , Chew Emily , Feelders Richard A. , Korpershoek Esther , Zhuang Zhengping , Yang Chunzhang , Pacak Karel
Published: January 2019

Background

Somatic mutations in hypoxia‐inducible factor 2α (HIF2A) are associated with polycythemia‐paraganglioma syndrome. Specifically, the classic presentation of female patients with recurrent paragangliomas (PGLs), polycythemia (at birth or in early childhood), and duodenal somatostatinomas has been described. Studies have demonstrated that somatic HIF2A mutations occur as postzygotic events and some to be associated with somatic mosaicism affecting hematopoietic and other tissue precursors. This phenomenon could explain the development of early onset of polycythemia in the absence of erythropoietin‐secreting tumors.

Methods

Correlation analysis was performed between mosaicism of HIF2A mutant patients and clinical presentations.

Results

Somatic HIF2A mutations (p.A530V, p.P531S, and p.D539N) were identified in DNA extracted from PGLs of 3 patients. No somatic mosaicism was detected through deep sequencing of blood genomic DNA. Compared with classic syndrome, both polycythemia and PGL in all 3 patients developed at an advanced age with polycythemia at age 30, 30, and 17 years and PGLs at age 34, 30, and 55 years, respectively. Somatostatinomas were not detected, and 2 patients had ophthalmic findings. The biochemical phenotype in all 3 patients was noradrenergic with 18F‐fluorodopa PET/CT as the most sensitive imaging modality. All patients demonstrated multiplicity, and none developed metastatic disease.

Conclusion

These findings suggest that newer techniques need to be developed to detect somatic mosaicism in patients with this syndrome. Absence of HIF2A mosaicism in patients with somatic HIF2A mutations supports association with late onset of the disease, milder clinical phenotype, and an improved prognosis compared with patients who have HIF2A mosaicism.
Risk‐stratified surveillance in dermatofibrosarcoma protuberans: Less is more
Authors: Gladdy Rebecca A. , Wunder Jay S.
Published: January 2019

Dermatofibrosarcoma is a dermal sarcoma that is predominately indolent, and local recurrence is the main pattern of failure. In this editorial, the need to perform routine surveillance for the majority of patients is challenged, and risk factors for recurrence are highlighted to define the subset of patients who warrant clinical follow‐up.
Air‐Stable Symmetric Ambipolar Field‐Effect Transistors Based on Reduced Graphene Oxide‐OTS Self‐Assembled Monolayer Heterostructure
Authors: Peng Peng , Liu Hongtao , Wu Bin , Tang Qingxin , Liu Yunqi
Published: January 2019

Graphene has attracted great interest in the past decade due to its unique band structure and physical properties such as quantum electronic transport, extremely high mobility, high elasticity and optical properties. Graphene is generally obtained by mechanical exfoliation, epitaxial growth, chemical vapor deposition and chemical synthesis approaches, wherein the reduction of graphene oxide (GO) is a practical approach to synthesize large‐scale graphene. Via reduction, highly conductive reduced graphene oxide (RGO) can be obtained, which has electrical and optical properties analogous to those of graphene. However, Field‐effect transistors (FETs) based RGO typically exhibit p‐type in ambient rather than the ambipolar behavior of intrinsic graphene, due to the doping effect induced by substrate and the air. Meanwhile, large hysteresis accompanies with the p‐type transistor. Here, a self‐assembled monolayer (SAM) of octadecyltrichlorosilane (OTS)‐RGO heterostructure is developed, in which RGO is sandwiched between OTS SAMs. The heterostructure passivates the RGO device and eliminates the doping of graphene from the surroundings. The obtained RGO FETs exhibit air‐stable symmetric ambipolar behavior with Dirac point at 0 V gate voltage and negligible hysteresis. This approach will also be applicable to pristine graphene and other two‐dimensional materials to obtain the intrinsic properties under ambient conditions, thereby promoting the research and applications of two‐dimensional materials.
Organic Two‐Dimensional Assembly with Rectification Property Mediated by Cucurbit[8]uril
Authors: Zhang Zhi‐Yuan , Chen Yong , Qi Ji‐Wei , Liu Yu
Published: January 2019

We report a highly regular organic two‐dimensional assembly made of cucurbit[8]uril and aromatic units that shows peculiar optoelectronic properties. We found that this individual self‐assembled microplate displayed a good conductivity under forward bias but nearly no current was detected under reverse bias along the stacking direction. This unique phenomenon is due to the coordination assembly of cucurbit[8]uril with aromatic units and aromatic stacking between layers. Moreover, the fluorescent properties are maintained in the solid state. Our result might show advantages in fabricating optoelectronic devices and help others to design organic two‐dimensional materials with specific functions.
Conducting a Reproducible Mendelian Randomization Analysis Using the R Analytic Statistical Environment
Authors: Rasooly Danielle , Patel Chirag J.
Published: January 2019

Mendelian randomization (MR) is defined as the utilization of genetic variants as instrumental variables to assess the causal relationship between an exposure and an outcome. By leveraging genetic polymorphisms as proxy for an exposure, the causal effect of an exposure on an outcome can be assessed while addressing susceptibility to biases prone to conventional observational studies, including confounding and reverse causation, where the outcome causes the exposure. Analogous to a randomized controlled trial where patients are randomly assigned to subgroups based on different treatments, in an MR analysis, the random allocation of alleles during meiosis from parent to offspring assigns individuals to different subgroups based on genetic variants. Recent methods use summary statistics from genome‐wide association studies to perform MR, bypassing the need for individual‐level data. Here, we provide a straightforward protocol for using summary‐level data to perform MR and provide guidance for utilizing available software. © 2019 by John Wiley & Sons, Inc.
Visible‐Light‐Driven Photocatalytic Z‐Scheme Overall Water Splitting in La5Ti2AgS5O7‐based Powder‐Suspension System
Authors: Song Zhimin , Hisatomi Takashi , Chen Shanshan , Wang Qian , Ma Guijun , Li Shikuo , Zhu Xiaodi , Sun Song , Domen Kazunari
Published: January 2019

La5Ti2CuxAg1−xS5O7 (x=0–1) is a type of long‐wavelength‐responsive oxysulfide photocatalysts for hydrogen evolution and has been demonstrated to enable the Z‐scheme water‐splitting coupling with oxygen evolution photocatalysts (OEPs) in the particulate sheet. Among La5Ti2CuxAg1−xS5O7 materials, La5Ti2AgS5O7 was found to have the highest performance on Z‐scheme overall water splitting in conjunction with PtOx‐WO3 as an OEP and a triiodide/iodide (I3−/I−) redox couple as a shuttle electron mediator in a powder‐suspension system. Loading Pt/NiS on La5Ti2AgS5O7 benefitted the Z‐scheme to achieve an apparent quantum yield of 0.12 % at 420 nm. The results for this powder‐suspension system differ from earlier studies on photocatalyst sheet configurations, in which p‐type doping and the formation of a solid solution could effectively enhance the water‐splitting activity. This work not only demonstrates a La5Ti2AgS5O7‐based Z‐scheme water‐splitting photocatalyst but also improves the understanding of the difference between particulate sheets and a powder‐suspension system available in an optimal strategy for water splitting.
Kinetic Competition between Water‐Splitting and Photocorrosion Reactions in Photoelectrochemical Devices
Authors: Nandjou Fredy , Haussener Sophia
Published: January 2019

Semiconductor photocorrosion is a major challenge for the stability of photoelectrochemical water‐splitting devices. Usually, photocorrosion is studied on the basis of thermodynamic aspects, by comparing the redox potentials of water to the self‐decomposition potentials of the semiconductor or analyzing the equilibrium phases at given electrolyte conditions. However, that approach does not allow for a prediction of the decomposition rate of the semiconductor or the branching ratio with the redox reaction. A kinetic model has been developed to describe detailed reaction mechanisms and investigate competition between water‐splitting and photocorrosion reactions. It is observed that some thermodynamically unstable semiconductors should photocorrode in a few minutes, whereas others are expected to operate over a period of years as a result of their extremely low photocorrosion current. The photostability of the semiconductor is mainly found to depend on surface chemical properties, catalyst activity, charge carrier density, and electrolyte acidity.
Selective Hydrogenation of CO2 to CH3OH on Supported Cu Nanoparticles Promoted by Isolated TiIV Surface Sites on SiO2
Authors: Noh Gina , Lam Erwin , Alfke Jan Lucas , Larmier Kim , Searles Keith , Wolf Patrick , Copéret Christophe
Published: January 2019

Small and narrowly distributed Cu nanoparticles, supported on SiO2 decorated with isolated TiIV sites, prepared through surface organometallic chemistry, showed significantly improved CO2 hydrogenation activity and CH3OH selectivity compared to the corresponding Cu nanoparticles supported on SiO2. These isolated Lewis acid TiIV sites, evidenced by UV/Vis spectroscopy, are proposed to stabilize surface intermediates at the interface between Cu nanoparticles and the support.
Geographic patterns of the climate sensitivity of lakes
Authors: McCullough Ian M. , Cheruvelil Kendra Spence , Collins Sarah M. , Soranno Patricia A.
Published: January 2019

Climate change is a well‐recognized threat to lake ecosystems and, although there likely exists geographic variation in the sensitivity of lakes to climate, broad‐scale, long‐term studies are needed to understand this variation. Further, the potential mediating role of local to regional ecological context on these responses is not well documented. In this study, we examined relationships between climate and water clarity in 365 lakes from 1981 to 2010 in two distinct regions in the northeastern and midwestern United States. We asked (1) How do climate–water‐clarity relationships vary across watersheds and between two geographic regions? and (2) Do certain characteristics make some lakes more climate sensitive than others? We found strong differences in climate–water‐clarity relationships both within and across the two regions. For example, in the northeastern region, water clarity was often negatively correlated with summer precipitation (median correlation = −0.32,n = 160 lakes), but was not correlated with summer average maximum temperature (median correlation = 0.09,n = 205 lakes). In the midwestern region, water clarity was not related to summer precipitation (median correlation = −0.04), but was often negatively correlated with summer average maximum temperature (median correlation = −0.18). There were few strong relationships between local and sub‐regional ecological context and a lake's sensitivity to climate. For example, ecological context variables explained just 16–18% of variation in summer precipitation sensitivity, which was most related to total phosphorus, chlorophylla, lake depth, and hydrology in both regions. Sensitivity to summer maximum temperature was even less predictable in both regions, with 4% or less of variation explained using all ecological context variables. Overall, we identified differences in the climate sensitivity of lakes across regions and found that local and sub‐regional ecological context weakly influences the sensitivity of lakes to climate. Our findings suggest that local to regional drivers may combine to influence the sensitivity of lake ecosystems to climate change, and that sensitivities among lakes are highly variable within and across regions. This variability suggests that lakes are sensitive to different aspects of climate change (temperature vs. precipitation) and that responses of lakes to climate are heterogeneous and complex.
Species‐level biodiversity assessment using marine environmental DNA metabarcoding requires protocol optimization and standardization
Authors: Jeunen Gert‐Jan , Knapp Michael , Spencer Hamish G. , Taylor Helen R. , Lamare Miles D. , Stat Michael , Bunce Michael , Gemmell Neil J.
Published: January 2019

DNA extraction from environmental samples (environmental DNA; eDNA) for metabarcoding‐based biodiversity studies is gaining popularity as a noninvasive, time‐efficient, and cost‐effective monitoring tool. The potential benefits are promising for marine conservation, as the marine biome is frequently under‐surveyed due to its inaccessibility and the consequent high costs involved. With increasing numbers of eDNA‐related publications have come a wide array of capture and extraction methods. Without visual species confirmation, inconsistent use of laboratory protocols hinders comparability between studies because the efficiency of target DNA isolation may vary. We determined an optimal protocol (capture and extraction) for marine eDNA research based on total DNA yield measurements by comparing commonly employed methods of seawater filtering and DNA isolation. We compared metabarcoding results of both targeted (small taxonomic group with species‐level assignment) and universal (broad taxonomic group with genus/family‐level assignment) approaches obtained from replicates treated with the optimal and a low‐performance capture and extraction protocol to determine the impact of protocol choice and DNA yield on biodiversity detection. Filtration through cellulose‐nitrate membranes and extraction with Qiagen's DNeasy Blood & Tissue Kit outperformed other combinations of capture and extraction methods, showing a ninefold improvement in DNA yield over the poorest performing methods. Use of optimized protocols resulted in a significant increase in OTU and species richness for targeted metabarcoding assays. However, changing protocols made little difference to the OTU and taxon richness obtained using universal metabarcoding assays. Our results demonstrate an increased risk of false‐negative species detection for targeted eDNA approaches when protocols with poor DNA isolation efficacy are employed. Appropriate optimization is therefore essential for eDNA monitoring to remain a powerful, efficient, and relatively cheap method for biodiversity assessments. For seawater, we advocate filtration through cellulose‐nitrate membranes and extraction with Qiagen's DNeasy Blood & Tissue Kit or phenol‐chloroform‐isoamyl for successful implementation of eDNA multi‐marker metabarcoding surveys.
Drawdown flushing in a chain of reservoirs—Effects on grayling populations and implications for sediment management
Authors: Reckendorfer Walter , Badura Hannes , Schütz Claudia
Published: January 2019

We used an information theoretic approach to assess the effects of an ecologically adjusted sediment management scheme on grayling (Thymallus thymallus L. 1758) populations. Additionally to reservoir operation, candidate models included a variety of parameters and processes that may influence grayling populations such as flow, temperature, density dependence, and bird predation. Population parameters analyzed included total densities, young of the year numbers, and larval densities. These analyses were supplemented by a characterization of sediments and sedimentation patterns in the reach. Investigations were carried out in six sites affected by flushing and in one control site. A total of thirteen flushing operations have been undertaken within the study period leading to considerable remobilization of fine sediments and gravel. Due to seasonal and hydrological restrictions, not every flood could be used for flushing. These limitations led to an interrupted management throughout the chain of reservoirs as well as to long time intervals between flushing events with possible effects on spawning habitat quality. None of the investigated population parameters was affected by flushing, and thus, the study generally supports the current reservoir management scheme. Our analyses revealed the magnitude and timing of high water events, temperature, and density‐dependent effects, that is, population densities the year before, as the most influential variables for grayling population dynamics in the investigated stretch. The siltation of reservoirs is a significant problem for reservoir storage, flood protection, river deltas, and coastal zones. Its management—which is inevitable to safeguard river deltas and secure flood protection—poses also the challenge to safeguard riverine ecosystems below reservoirs. Based on our experience, we propose a periodic flushing regime in concordance with the hydrograph thereby mimicking the timing, magnitude, frequency, and duration of natural SSC pulses and gravel transport. This flushing regime minimizes adverse downstream environmental impacts and maximizes benefits.
Fruit production is influenced by tree size and size‐asymmetric crowding in a wet tropical forest
Authors: Minor David M. , Kobe Richard K.
Published: January 2019

In tropical forest communities, seedling recruitment can be limited by the number of fruit produced by adults. Fruit production tends to be highly unequal among trees of the same species, which may be due to environmental factors. We observed fruit production for ~2,000 trees of 17 species across 3 years in a wet tropical forest in Costa Rica. Fruit production was modeled as a function of tree size, nutrient availability, and neighborhood crowding. Following model selection, tree size and neighborhood crowding predicted both the probability of reproduction and the number of fruit produced. Nutrient availability only predicted only the probability of reproduction. In all species, larger trees were more likely to be reproductive and produce more fruit. In addition, number of fruit was strongly negatively related to presence of larger neighboring trees in 13 species; presence of all neighboring trees had a weak‐to‐moderate negative influence on reproductive status in 16 species. Among various metrics of soil nutrient availability, only sum of base cations was positively associated with reproductive status, and for only four species.SynthesisOverall, these results suggest that direct influences on fruit production tend to be mediated through tree size and crowding from neighboring trees, rather than soil nutrients. However, we found variation in the effects of neighbors and nutrients among species; mechanistic studies of allocation to fruit production are needed to explain these differences.
Characterizing neutral and adaptive genomic differentiation in a changing climate: The most northerly freshwater fish as a model
Authors: O'Malley Kathleen G. , Vaux Felix , Black Andrew N.
Published: January 2019

Arctic freshwater ecosystems have been profoundly affected by climate change. Given that the Arctic charr (Salvelinus alpinus) is often the only fish species inhabiting these ecosystems, it represents a valuable model for studying the impacts of climate change on species life‐history diversity and adaptability. Using a genotyping‐by‐sequencing approach, we identified 5,976 neutral single nucleotide polymorphisms and found evidence for reduced gene flow between allopatric morphs from two high Arctic lakes, Linne'vatn (Anadromous, Normal, and Dwarf) and Ellasjøen (Littoral and Pelagic). Within each lake, the degree of genetic differentiation ranged from low (Pelagic vs. Littoral) to moderate (Anadromous and Normal vs. Dwarf). We identified 17 highly diagnostic, putatively adaptive SNPs that differentiated the allopatric morphs. Although we found no evidence for adaptive differences between morphs within Ellasjøen, we found evidence for moderate (Anadromous vs. Normal) to high genetic differentiation (Anadromous and Normal vs. Dwarf) among morphs within Linne'vatn based on two adaptive loci. As these freshwater ecosystems become more productive, the frequency of sympatric morphs in Ellasjøen will likely shift based on foraging opportunities, whereas the propensity to migrate may decrease in Linne'vatn, increasing the frequency of the Normal morph. The Dwarf charr was the most genetically distinct group. Identifying the biological basis for small body size should elucidate the potential for increased growth and subsequent interbreeding with sympatric morphs. Overall, neutral and adaptive genomic differentiation between allopatric and some sympatric morphs suggests that the response of Arctic charr to climate change will be variable across freshwater ecosystems.
Assessing the long‐term carbon‐sequestration potential of the semi‐natural salt marshes in the European Wadden Sea
Authors: Mueller Peter , Ladiges Nils , Jack Alexander , Schmiedl Gerhard , Kutzbach Lars , Jensen Kai , Nolte Stefanie
Published: January 2019

Salt marshes and other blue carbon ecosystems have been increasingly recognized for their carbon (C)‐sink function. Yet, an improved assessment of organic carbon (OC) stocks and C‐sequestration rates is still required to include blue C in C‐crediting programs. Particularly, factors inducing variability in the permanence of sequestration and allochthonous contributions to soil OC stocks require an improved understanding. This study evaluates the potential for long‐term C sequestration in the semi‐natural salt marshes of the European Wadden Sea (WS), conducting deep (1.3 m) down‐core OC‐density assessments in sites with known site histories and accretion records. Because these young marshes have developed from tidal‐flat ecosystems and have undergone rapid succession during the last 80–120 yr, the identification of different ecosystem stages down‐core was crucial to interpret possible changes in OC density. This was conducted based on the down‐core distribution of different foraminiferal taxa and grain sizes. Comparisons of historic and recent accretion rates were conducted to understand possible effects of accretion rate on down‐core changes in OC density. δ13C in OC was used to assess the origin of accumulated OC (autochthonous vs. allochthonous sources). We show that large amounts of short‐term accumulated OC are lost down‐core in the well‐aerated marsh soils of the WS region and thus emphasize the importance of deep sampling to avoid overestimation of C sequestration. Despite steep declines in OC‐density down‐core, minimum values of OC density in the salt‐marsh soils were considerably higher than those of the former tidal‐flat sediments that the marshes were converted from, illustrating the greater C‐sequestration potential of the vegetated ecosystem. However, our data also suggest that marine‐derived allochthonous OC makes up a large fraction of the effectively, long‐term preserved OC stock, whereas atmospheric CO2 removal by marsh vegetation contributes relatively little. The implication of this finding for C‐crediting approaches in blue C ecosystems has yet to be clarified.