bluuebunny/crossref_metadata_2025_split huggingface dataset:
Novel Spatial Domain Integral Equation Formulation for the Analysis of Rectangular Waveguide Steps Close to Arbitrarily Shaped Dielectric and/or Conducting Posts
Authors: Quesada Pereira F. D. , Gómez Molina C. , Alvarez Melcon A. , Boria V. E. , Guglielmi M. 
Published: March 2018

AbstractIn this paper, a novel integral equation formulation expressed in the spatial domain is proposed for the analysis of rectangular waveguide step discontinuities. The important novelty of the proposed formulation is that which allows to easily take into account the electrical influence of a given number of arbitrarily shaped conducting and dielectric posts placed close to the waveguide discontinuity. For the sake of simplicity, and without loss of generality, the presented integral equation has been particularized and solved for inductive rectangular waveguide geometry. In this case, the integral equation mixed‐potentials kernel is written in terms of parallel plate Green's functions with an additional ground plane located on the waveguide step. Therefore, the unknowns of the problem are reduced to an equivalent magnetic surface current on the step aperture and equivalent magnetic and electric surface currents on the dielectric and conducting posts close to the discontinuity. The numerical solution of the final integral equation is efficiently computed after the application of acceleration techniques for the slowly convergent series representing the Green's functions of the problem. The numerical method has been validated through several simulation examples of practical microwave devices, including compact size band‐pass cavity filters and coupled dielectric resonators filters. The results have been compared to those provided by commercial full‐wave electromagnetic simulation software packages, showing in all cases a very good agreement, and with substantially enhanced numerical efficiencies.
Onsets of Solar Proton Events in Satellite and Ground Level Observations: A Comparison
Authors: He Jing , Rodriguez Juan V. 
Published: March 2018

AbstractThe early detection of solar proton event onsets is essential for protecting humans and electronics in space, as well as passengers and crew at aviation altitudes. Two commonly compared methods for observing solar proton events that are sufficiently large and energetic to be detected on the ground through the creation of secondary radiation—known as ground level enhancements (GLEs)—are (1) a network of ground‐based neutron monitors (NMs) and (2) satellite‐based particle detectors. Until recently, owing to the different time resolution of the two data sets, it has not been feasible to compare these two types of observations using the same detection algorithm. This paper presents a comparison between the two observational platforms using newly processed >100 MeV 1 min count rates and fluxes from National Oceanic and Atmospheric Administration's Geostationary Operational Environmental Satellite (GOES) 8–12 satellites, and 1 min count rates from the Neutron Monitor Database. We applied the same detection algorithm to each data set (tuned to the different background noise levels of the instrument types). Seventeen SPEs with GLEs were studied: GLEs 55–70 from Solar Cycle 23 and GLE 71 from Solar Cycle 24. The median difference in the event detection times by GOES and NM data is 0 min, indicating no innate benefit in time of either system. The 10th, 25th, 75th, and 90th percentiles of the onset time differences (GOES minus NMs) are −7.2 min, −1.5 min, 2.5 min, and 4.2 min, respectively. This is in contrast to previous studies in which NM detections led GOES by 8 to 52 min without accounting for different alert protocols.
Vibrational Energy Transport in Hybrid Ordered/Disordered Nanocomposites: Hybridization and Avoided Crossings of Localized and Delocalized Modes
Authors: Zhu Taishan , Swaminathan‐Gopalan Krishnan , Cruse Kevin J. , Stephani Kelly , Ertekin Elif 
Published: February 2018

AbstractVibrational energy transport in disordered media is of fundamental importance to several fields spanning from sustainable energy to biomedicine to thermal management. This work investigates hybrid ordered/disordered nanocomposites that consist of crystalline membranes decorated by regularly patterned disordered regions formed by ion beam irradiation. The presence of the disordered regions results in reduced thermal conductivity, rendering these systems of interest for use as nanostructured thermoelectrics and thermal device components, yet their vibrational properties are not well understood. Here, the mechanism of vibrational transport and the reason underlying the observed reduction is established in detail. The hybrid systems are found to exhibit glass‐crystal duality in vibrational transport. Lattice dynamics reveals substantial hybridization between the localized and delocalized modes, which induces avoided crossings and harmonic broadening in the dispersion. Allen/Feldman theory shows that the hybridization and avoided crossings are the dominant drivers of the reduction. Anharmonic scattering is also enhanced in the patterned nanocomposites, further contributing to the reduction. The systems exhibit features reminiscent of both nanophononic materials and locally resonant nanophononic metamaterials, but operate in a manner distinct to both. These findings indicate that such “patterned disorder” can be a promising strategy to tailor vibrational transport through hybrid nanostructures.
1D SnO2 with Wire‐in‐Tube Architectures for Highly Selective Electrochemical Reduction of CO2 to C1 Products
Authors: Fan Lei , Xia Zheng , Xu Meijia , Lu Yingying , Li Zhongjian 
Published: February 2018

AbstractElectrochemical reduction of CO2 (ERC) into useful products, such as formic acid and carbon monoxide, is a fascinating approach for CO2 fixation as well as energy storage. Sn‐based materials are attractive catalysts for highly selective ERC into C1 products (including HCOOH and CO), but still suffer from high overpotential, low current density, and poor stability. Here, One‐dimensional (1D) SnO2 with wire‐in‐tube (WIT) structure is synthesized and shows superior selectivity for C1 products. Using the WIT SnO2 as the ERC catalyst, very high Faradaic efficiency of C1 products (>90%) can be achieved at a wide potential range from −0.89 to −1.29 V versus RHE, thus substantially suppressing the hydrogen evolution reaction. The electrocatalyst also exhibits excellent long‐term stability. The improved catalytic activity of the WIT SnO2 over the commercial SnO2 nanoparticle indicates that higher surface area and large number of grain boundaries can effectively enhance the ERC activity. Synthesized via a facile and low‐cost electrospinning technology, the reduced WIT SnO2 can serve as a promising electrocatalyst for efficient CO2 to C1 products conversion.
Novel Safeguarding Tactile e‐Skins for Monitoring Human Motion Based on SST/PDMS–AgNW–PET Hybrid Structures
Authors: Wang Sheng , Gong Liping , Shang Zejin , Ding Li , Yin Guansheng , Jiang Wanquan , Gong Xinglong , Xuan Shouhu 
Published: March 2018

AbstractA novel versatile electrical skin (e‐skin) with safeguarding and multisensing properties based on hybrid structures is developed by assembling Ag nanowires (AgNWs), polyester (PET) film with hybrid shear stiffening polymer/polydimethylsiloxane (SST/PDMS) matrix. The hybrid SST/PDMS polymer shows stable configuration. Storage modulus of the SST/PDMS increases from 5.5 kPa to 0.39 MPa when the shear frequency changes from 0.1 to 100 Hz, exhibiting typical rate‐dependent behavior. e‐Skin functions as a human‐monitoring device by detecting various motions such as gentle touching, stroking, elbow bending, as well as speaking. More importantly, due to the shear stiffening characteristic, e‐skin with high damping capacity exhibits safeguarding performance, which can dissipate impact force from 720 to 400 N and increase buffer time (from 0.9 to 2 ms). Meanwhile, distinguishable resistance values can reveal the level of harsh impact applied on the e‐skin. In addition, the visible thermosensation effect of e‐skin similar to chameleon epidermis is convenient for assessing environmental temperature. e‐Skin arrays can precisely map the dynamic impact location and pressure distribution. Finally, the high electrical sensitivity and shear stiffening performance are attributed to the disturbance of AgNW effective conductive paths and dynamic BO bonds, respectively.
Halogen‐Bond‐Promoted α‐C−H Amination of Ethers for the Synthesis of Hemiaminal Ethers
Authors: Pan Zhangjin , Fan Zhenwei , Lu Beili , Cheng Jiajia 
Published: February 2018

AbstractA simple halogen‐bond‐promoted α‐C−H amination of ether/thioether with a variety of N−H compounds has been accomplished. In the presence of low‐cost and readily available perfluorobutyl iodide, a diverse range of hemiaminal ether derivatives, including the valuable hydrazone hemiaminal ethers, were quickly assembled under thermal or visible‐light irradiation conditions. Mechanistic studies suggest that a halogen‐bond adduct was formed and a radical chain pathway might be operative. Synthetic application of the method has been demonstrated via the preparation of the anti‐viral and anti‐tumor drug, Tegafur.magnified image
A Versatile Reagent and Method for Direct Aliphatic Sulfonylation
Authors: Shavnya Andre , Hesp Kevin D. , Tsai Andy S. 
Published: March 2018

AbstractAn efficient methodology has been developed for the two‐step synthesis of aliphatic sulfinate salts, sulfonamides, sulfonyl fluorides, and unsymmetrical sulfones on the basis of alkylation of a new versatile sulfonylating reagent. The new reagent is easily accessible in one step; the developed protocols are conducted under mild conditions and have a broad substrate scope.magnified image
Selective Hydrogen Atom Abstraction through Induced Bond Polarization: Direct α‐Arylation of Alcohols through Photoredox, HAT, and Nickel Catalysis
Authors: Twilton Jack , Christensen Melodie , DiRocco Daniel A. , Ruck Rebecca T. , Davies Ian W. , MacMillan David W. C. 
Published: February 2018

AbstractThe combination of nickel metallaphotoredox catalysis, hydrogen atom transfer catalysis, and a Lewis acid activation mode, has led to the development of an arylation method for the selective functionalization of alcohol α‐hydroxy C−H bonds. This approach employs zinc‐mediated alcohol deprotonation to activate α‐hydroxy C−H bonds while simultaneously suppressing C−O bond formation by inhibiting the formation of nickel alkoxide species. The use of Zn‐based Lewis acids also deactivates other hydridic bonds such as α‐amino and α‐oxy C−H bonds. This approach facilitates rapid access to benzylic alcohols, an important motif in drug discovery. A 3‐step synthesis of the drug Prozac exemplifies the utility of this new method.
Pyrrolidines and Piperidines by Ligand‐Enabled Aza‐Heck Cyclizations and Cascades of N‐(Pentafluorobenzoyloxy)carbamates
Authors: Hazelden Ian R. , Carmona Rafaela C. , Langer Thomas , Pringle Paul G. , Bower John F. 
Published: February 2018

AbstractLigand‐enabled aza‐Heck cyclizations and cascades of N‐(pentafluorobenzoyloxy)carbamates are described. These studies encompass the first examples of efficient non‐biased 6‐exo aza‐Heck cyclizations. The methodology provides direct and flexible access to carbamate protected pyrrolidines and piperidines.
Scrutinizing Defects and Defect Density of Selenium‐Doped Graphene for High‐Efficiency Triiodide Reduction in Dye‐Sensitized Solar Cells
Authors: Meng Xiangtong , Yu Chang , Song Xuedan , Iocozzia James , Hong Jiafu , Rager Matthew , Jin Huile , Wang Shun , Huang Longlong , Qiu Jieshan , Lin Zhiqun 
Published: February 2018

AbstractUnderstanding the impact of the defects/defect density of electrocatalysts on the activity in the triiodide (I3−) reduction reaction of dye‐sensitized solar cells (DSSCs) is indispensable for the design and construction of high‐efficiency counter electrodes (CEs). Active‐site‐enriched selenium‐doped graphene (SeG) was crafted by ball‐milling followed by high‐temperature annealing to yield abundant edge sites and fully activated basal planes. The density of defects within SeG can be tuned by adjusting the annealing temperature. The sample synthesized at an annealing temperature of 900 °C exhibited a superior response to the I3− reduction with a high conversion efficiency of 8.42 %, outperforming the Pt reference (7.88 %). Improved stability is also observed. DFT calculations showed the high catalytic activity of SeG over pure graphene is a result of the reduced ionization energy owing to incorporation of Se species, facilitating electron transfer at the electrode–electrolyte interface.
Analyte‐Triggered DNA‐Probe Release from a Triplex Molecular Beacon for Nanopore Sensing
Authors: Guo Bingyuan , Sheng Yingying , Zhou Ke , Liu Quansheng , Liu Lei , Wu Hai‐Chen 
Published: February 2018

AbstractA new nanopore sensing strategy based on triplex molecular beacon was developed for the detection of specific DNA or multivalent proteins. The sensor is composed of a triplex‐forming molecular beacon and a stem‐forming DNA component that is modified with a host–guest complex. Upon target DNA hybridizing with the molecular beacon loop or multivalent proteins binding to the recognition elements on the stem, the DNA probe is released and produces highly characteristic current signals when translocated through α‐hemolysin. The frequency of current signatures can be used to quantify the concentrations of the target molecules. This sensing approach provides a simple, quick, and modular tool for the detection of specific macromolecules with high sensitivity and excellent selectivity. It may find useful applications in point‐of‐care diagnostics with a portable nanopore kit in the future.
Taking Advantage of Hydrophobic Fluorine Interactions for Self‐Assembled Quantum Dots as a Delivery Platform for Enzymes
Authors: Carrillo‐Carrion Carolina , Atabakhshi‐Kashi Mona , Carril Mónica , Khajeh Khosro , Parak Wolfgang J. 
Published: February 2018

AbstractSelf‐assembly of nanoparticles provides unique opportunities as nanoplatforms for controlled delivery. By exploiting the important role of noncovalent hydrophobic interactions in the engineering of stable assemblies, nanoassemblies were formed by the self‐assembly of fluorinated quantum dots in aqueous medium through fluorine–fluorine interactions. These nanoassemblies encapsulated different enzymes (laccase and α‐galactosidase) with encapsulation efficiencies of ≥74 %. Importantly, the encapsulated enzymes maintained their catalytic activity, following Michaelis–Menten kinetics. Under an acidic environment the nanoassemblies were slowly disassembled, thus allowing the release of encapsulated enzymes. The effective release of the assayed enzymes demonstrated the feasibility of this nanoplatform to be used in pH‐mediated enzyme delivery. In addition, the as‐synthesized nanoassemblies, having a diameter of about 50 nm, presented high colloidal stability and fluorescence emission, which make them a promising multifunctional nanoplatform.
Risk of malignancy in resected pancreatic mucinous cystic neoplasms
Authors: Keane M. G. , Shamali A. , Nilsson L. N. , Antila A. , Millastre Bocos J. , Marijinissen Van Zanten M. , Verdejo Gil C. , Maisonneuve P. , Vaalavuo Y. , Hoskins T. , Robinson S. , Ceyhan G. O. , Abu Hilal M. , Pereira S. P. , Laukkarinen J. , Del Chiaro M. 
Published: February 2018

Abstract

Background
Pancreatic mucinous cystic neoplasms (MCNs) are rare mucin-producing cystic tumours defined by the presence of ovarian-type stroma. MCNs have a malignant potential and thus surgery is frequently performed. The aim of this cohort study was to define better the criteria for surgical resection in patients with MCN.

Methods
This multicentre retrospective study included all resected MCNs between 2003 and 2015 in participating centres. Lesions without ovarian-type stroma were excluded. Patient characteristics, preoperative findings, histopathology findings and follow-up data were recorded.

Results
The study included 211 patients; their median age was 53 (range 18–82) years, and 202 (95·7 per cent) were women. Median preoperative tumour size was 55 (range 12–230) mm. Thirty-four of the 211 (16·1 per cent) were malignant, and high-grade dysplasia (HGD) was found in a further 13 (6·2 per cent). One-third of MCNs in men were associated with invasive cancer, compared with 15·3 per cent in women. Five cases of malignant transformation occurred in MCNs smaller than 4 cm. All cases of malignancy or HGD were associated with symptoms or features of concern on preoperative cross-sectional imaging. In multivariable analysis, raised carbohydrate antigen 19-9 (odds ratio (OR) 10·54, 95 per cent c.i. 2·85 to 218·23; P &lt; 0·001), tumour size (OR 4·23, 3·02 to 11·03; P = 0·001), mural nodules (OR 3·55, 1·31 to 20·55; P = 0·002) and weight loss (OR 3·40, 2·34 to 12·34; P = 0·034) were independent factors predictive of malignant transformation.

Conclusions
Small indeterminate MCNs with no symptoms or features of concern may safely be observed as they have a low risk of malignant transformation.
Credibility of sustainability reports: The contribution of audit committees
Authors: Al‐Shaer Habiba , Zaman Mahbub 
Published: February 2018

AbstractConcerns about the credibility of sustainability reports can be mitigated through assurance. Although audit committee remit encompasses monitoring of sustainability issues, there are potential complementary and substitution issues between governance mechanisms. This paper explores the relationship between audit committees and sustainability reporting assurance using resource dependency theory. We find audit committee characteristics have an impact, additional to that of the board of directors and the existence of sustainability committees, on voluntary sustainability assurance. Our results also show that audit committee independence is associated with use of a Big Four audit firm for sustainability assurance. A negative association between sustainability committees and assurance, however, indicates assurance could be a burden for small firms. Overall, the findings suggest audit committees add credibility and help improve sustainability reporting through their independence, expertise and oversight.
Photomodulating Gene Expression by Using Caged siRNAs with Single‐Aptamer Modification
Authors: Zhang Liangliang , Chen Changmai , Fan Xinli , Tang Xinjing 
Published: February 2018

AbstractCaged siRNAs incorporating terminal modification were rationally designed for photochemical regulation of gene silencing induced by RNA interference (RNAi). Through the conjugation of a single oligonucleotide aptamer at the 5′ terminus of the antisense RNA strand, enhancement of the blocking effect for RNA‐induced silencing complex (RISC) formation/processing was expected, due both/either to the aptamers themselves and/or to their interaction with large binding proteins. Two oligonucleotide aptamers (AS1411 and MUC‐1) were chosen for aptamer‐siRNA conjugation through a photolabile linker. This caging strategy was successfully used to photoregulate gene expression both of firefly luciferase and of green fluorescent protein (GFP) in cells. Further patterning experiments revealed that spatial regulation of GFP expression was successfully achieved by using the aptamer‐modified caged siRNA and light activation. We expect that further optimized caged siRNAs featuring aptamer conjugation will be promising for practical applications to spatiotemporal photoregulation of gene expression in the future.
Multicolor Upconversion Nanoprobes Based on a Dual Luminescence Resonance Energy Transfer Assay for Simultaneous Detection and Bioimaging of [Ca2+]i and pHi in Living Cells
Authors: Song Xinyue , Yue Zihong , Zhang Jiayu , Jiang Yanxialei , Wang Zonghua , Zhang Shusheng 
Published: February 2018

AbstractIntracellular [Ca2+]i and pHi have a close relationship, and their abnormal levels can result in cell dysfunction and accompanying diseases. Thus, simultaneous determination of [Ca2+]i and pHi can more accurately investigate complex biological processes in an integrated platform. Herein, multicolor upconversion nanoparticles (UCNPs) were prepared with the advantages of no spectral overlapping, single NIR excitation wavelengths, and greater tissue penetration depth. The upconversion nanoprobes were easily prepared by the attachment of two fluorescent dyes, Fluo‐4 and SNARF‐4F. Based on the dual luminescence resonance energy transfer (LRET) process, the blue and green fluorescence of the UCNPs were specially quenched and selectively recovered after the detachment and/or absorbance change of the attached fluorescent dyes, enabling dual detection. Importantly, the developed nanoprobe could successfully be applied for the detection of [Ca2+]i and pHi change in adenosine triphosphate (ATP) and ethylene glycol tetraacetic acid (EGTA) stimulation in living cells.
Boosting Luminescence of Planar‐Fluorophore‐Tagged Metal–Organic Cages Via Weak Supramolecular Interactions
Authors: Luo Dong , Li Mian , Zhou Xiao‐Ping , Li Dan 
Published: February 2018

AbstractA variety of planar organic fluorophores (R=phenyl, naphthalenyl, pyrenyl) and luminescence promotors (X=Cl, Br, I) were equipped, respectively, on the alternatively arranged vertices of cubic ZnII‐imidazolate cages through orthogonal subcomponent self‐assembly. It was found that supramolecular interactions, especially weak C−H⋅⋅⋅X interactions, play a key role in activating an efficient radiative pathway, coupled with reduced nonradiative decay rate through metal coordination, therefore significantly boosting the emission quantum yields of the system. This finding provides a strategy that utilizes molecular geometry and supramolecular interactions to modulate the emission efficiency of luminescent cage‐based materials.
Transition‐Metal‐Catalyzed Regioselective Asymmetric Mono‐Hydrogenation of Dienes and Polyenes
Authors: Margarita Cristiana , Rabten Wangchuk , Andersson Pher G. 
Published: February 2018

AbstractOrganic compounds containing multiple C=C bonds are attractive substrates for catalytic asymmetric hydrogenation. The full saturation of prochiral double bonds, controlling the creation of two or more stereocenters in one step, is obviously a remarkable goal. However, another fascinating and useful option is to selectively introduce a new defined stereogenic center while leaving other double bonds untouched. Thus, the retained functionalities can be further exploited in synthesis. Examples of regio‐ and enantioselective mono‐hydrogenations of polyolefins are highlighted in this Concept article, and are divided according to the nature of the reduced double bond and the transition‐metal catalyst used. Alkenes bearing coordinating functional groups are often preferentially hydrogenated by Rh‐ and Ru‐complexes, while the more recently developed Ir‐based catalysts promote the selective saturation on alkyl‐substituted olefins. Relevant applications of this effective methodology in the synthesis of natural products are included to demonstrate its value in organic synthesis.