bluuebunny/crossref_metadata_2025 huggingface dataset:
Proximal balloon occlusion versus distal filter protection in carotid artery stenting: A meta‐analysis and review of the literature
Authors: Omran Jad , Mahmud Ehtisham , White Christopher J. , Aronow Herbert D. , Drachman Douglas E. , Gray William , Abdullah Obai , Abu‐Fadel Mazen , Firwana Belal , Mishkel Gergory , Al‐Dadah Ashraf S.
Published: November 2016

Introduction

Carotid artery stenting (CAS) is typically performed using embolic protection devices (EPDs) as a means to reduce the risk of procedure‐related stroke. In this study, we compared procedural morbidity and mortality associated with distal (D‐EPD) vs. proximal (P‐EPD) protection.

Methods

MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials were queried from January 1998 through May 2015. Only studies comparing (D‐EPD) and (P‐EPD) were included. Two independent reviewers selected and appraised studies and extracted data in duplicate. Random‐effects meta‐analysis was used to pool outcomes across studies. Heterogeneity of treatment effect among studies was assessed using the I2 statistics. Publication bias was assessed using inspection of funnel plots. The primary endpoints included 30‐day mortality and stroke. Secondary endpoints included new cerebral lesions on diffusion‐weighted magnetic resonance imaging (DW‐MRI) and contralateral lesions on DW‐MRI.

Results

A total of 12,281 patients were included from 18 studies (13 prospective and 5 retrospective) comparing (D‐EPD) and (P‐EPD) in the setting of CAS. The mean patient age was 69 years and 64% of patients were male. No evidence of publication bias was detected. There was no significant difference between the two modalities in terms of the risk of stroke (risk difference [RD] 0.0, 95% confidence interval [CI] −0.01 to 0.01) or mortality (RD 0.0, 95% CI −0.01 to 0.01) nor was there any difference in the incidence of new cerebral lesions on DW‐MRI or contralateral DW‐MRI lesions.

Conclusions

In patients undergoing CAS, both D‐EPD and P‐EPD provide similar levels of protection from peri‐procedural stroke and 30 days mortality. © 2016 Wiley Periodicals, Inc.
Novel use of the medtronic micro vascular plug for PDA closure in preterm infants
Authors: Wang‐Giuffre Elizabeth W. , Breinholt John P.
Published: November 2016

Objectives

To describe a single institution experience with a new endovascular occlusion device used for transcatheter patent ductus arteriosus (PDA) closure in preterm infants.

Background

The PDA is a defect largely treated via cardiac catheterization except for the smallest patients.

Methods

Medical records and catheterization reports of all premature neonates who underwent PDA device closure with the Medtronic Micro Vascular Plug (MVP) (Medtronic, Minneapolis, MN) between September 2015 and June 2016 were reviewed. Procedural details, complications, and short term outcomes were recorded.

Results

Eight premature neonates born at a median gestational age of 28 weeks (23 to 35 weeks) underwent PDA closure with a Medtronic MVP. All devices were deployed via a 4F angled Glide catheter in prograde fashion without arterial access. Median age and weight was 52 days (15–112 days) and 2,550 g (1,800–3,500 g), respectively. Fluoroscopy and echocardiography were utilized for the procedure. Complete closure was achieved in all patients with no procedural complications, pulmonary artery or aortic obstruction or death. One device embolized 9 days after deployment and was successfully retrieved.

Conclusions

This study describes transcatheter PDA closure with the Medtronic MVP. The major advantage is the ability to deliver the device via a standard catheter in prograde fashion, and avoid the hemodynamic instability produced by rigid delivery sheaths. It also further validates the ability to close the PDA without arterial access, providing improved access to this procedure to smaller and more vulnerable children. © 2016 Wiley Periodicals, Inc.
Effect of post‐primary percutaneous coronary intervention bivalirudin infusion on net adverse clinical events and mortality: A comprehensive pairwise and network meta‐analysis of randomized controlled trials
Authors: Shah Rahman , Matin Khalid , Rogers Kelly C. , Rao Sunil V.
Published: November 2016

Objective

To compare the efficacies of various post‐percutaneous coronary intervenetion (PCI) bivalirudin doses on net adverse clinical events (NACEs) and mortality.

Background

In primary PCI, lower risk of bleeding with bivalirudin (vs. unfractionated heparin [UFH]) is counterbalanced by an increased risk of acute stent thrombosis (ST). Several randomized clinical trials (RCTs) and a recent meta‐analysis suggest that acute ST risk may be eliminated without compromising the bleeding benefit, but only if the full dose, not a low dose, of bivalirudin is continued post‐PCI. However, it is not known whether this improved risk leads to lower rates of NACEs and mortality.

Methods

Scientific databases and Web sites were searched for RCTs. Trials were included if study patients were undergoing primary PCI for acute ST‐segment elevation myocardial infarction and were randomly assigned to bivalirudin or UFH treatment. The bivalirudin arm was divided based on post‐PCI bivalirudin dosage: The Biv‐Full group received 1.75 mg/kg/h, the Biv‐Low group, 0.25 mg/kg/h, and the Biv‐No group, none.

Results

Six RCTs involving 16,842 patients were found. In pairwise meta‐analysis, bivalirudin improved 30‐day all‐cause mortality by 35% and cardiac mortality by 32%, but did not yield a NACE rate better than that achieved with UFH. Subgroup analysis showed the Biv‐Full group had a 46% lower NACE rate and 47% lower all‐cause mortality than UFH. These effects were not seen in the other two groups. Network meta‐analysis yielded similar results. At treatment ranking, the Biv‐Full group yielded the best treatment efficacy.

Conclusions

In primary PCI, full‐dose bivalirudin infusion for 3‐4 hr after PCI appeared to improve NACE rates compared to UFH. It also seemed to be the most effective strategy for improving cardiac mortality and all‐cause mortality. © 2016 Wiley Periodicals, Inc.
Evaluation of AgPd Nanoshells in Dual Catalysis: One‐Pot Silane Oxidation and Reduction of Organic Compounds
Authors: Kisukuri Camila M. , Reis João L. M. S. , Rodrigues Thenner S. , Camargo Pedro H. C. , Andrade Leandro H.
Published: November 2016

AgPd nanoshells (AgPd NSs) were used as dual catalysts for hydrogen production and reduction of organic compounds in a one‐pot protocol. AgPd NSs were very efficient catalysts for the reduction of several functional groups, including alkenes, alkynes, imines, nitro compounds, and azides. Excellent chemoselectivities were observed for α,β‐unsaturated ketones, esters, and cinnamonitrile. Also, deuterium‐labeled compounds were prepared by using D2O instead of H2O. A packed‐bed reactor containing the immobilized AgPd NSs in silica (AgPd/SiO2) was designed to be used in continuous‐flow conditions. An optimized flow system with AgPd NSs was able to give the desired compounds in high conversions with 30–60 min residence time (tR).
Scanning Electrochemical Microscopy and Voltammetric Investigation of Silver Nanoparticles Embedded within a Nafion Membrane
Authors: Pecchielan Giulia , Battistel Dario , Daniele Salvatore
Published: November 2016

In this paper, silver nanoparticles (AgNPs), incorporated in the poly(perfluorosulfonic) acid membrane Nafion 117, were fabricated by chemical reduction of the Ag+‐loaded membranes, using HCOH in a basic medium as reducing agent. The AgNP content within the membrane varied proportionally to the concentration of AgNO3used in the incorporation step of Ag+in the ion exchange. Information on size and density of the AgNPs within the matrix was obtained by SEM analysis. The size of the AgNPs varied between 10 and 20 nm, regardless of the AgNO3concentration used for their preparation, while AgNPs density was the higher, the greater the AgNO3concentration in the solution was. Information on the oxidation state of Ag in the AgNPs and their distribution and aggregation on the surface of the Nafion membranes were obtained by SECM measurements. The use of [Ir(Cl)6]3−and Ru(NH3)63+as redox mediators allowed establishing whether the AgNPs were interconnected to create nanochain networks to provide AgNPs‐loaded Nafion membranes with electronic conductivity. Moreover, combination of SECM and anodic stripping voltammetry allowed establishing the reactivity of the AgNP–Nafion composites in terms of AgIspecies released at the nanocomposite/solution interface. These aspects are relevant for the potential application of these AgNPs‐loaded membranes for antimicrobial protection purposes.
Dipole Moment Effect on the Electrochemical Desorption of Self‐Assembled Monolayers of 310‐Helicogenic Peptides on Gold
Authors: Gobbo Pierangelo , Antonello Sabrina , Guryanov Ivan , Polo Federico , Soldà Alice , Zen Federico , Maran Flavio
Published: November 2016

The front cover artwork is provided by Pierangelo Gobbo and Flavio Maran, University of Padova (Italy). The image highlights how the orientation of the dipole moment associated with helical peptides affects the electrodesorption potential of the corresponding self‐assembled monolayers. Read the full text of the Article at 10.1002/celc.201600573.
Nerve Gas Simulant Sensing by a Uranyl–Salen Monolayer Covalently Anchored on Quartz Substrates
Authors: Trusso Sfrazzetto Giuseppe , Millesi Salvatrice , Pappalardo Andrea , Tomaselli Gaetano A. , Ballistreri Francesco P. , Toscano Rosa Maria , Fragalà Ignazio , Gulino Antonino
Published: November 2016

A uranyl complex monolayer that easily allows the optical detection of a nerve gas simulant, namely, dimethyl methylphosphonate, is reported. Both UV/Vis spectroscopy and photoelectron data confirm that the functional hybrid material coordinates a Lewis base by means of the P=O group, which interacts with the uranium equatorial site available for complexation.
Fine Tuning of the Anisotropy Barrier by Ligand Substitution Observed in Linear {Dy2Ni2} Clusters
Authors: Li Yan , Shang Qiu , Zhang Yi‐Quan , Yang En‐Cui , Zhao Xiao‐Jun
Published: November 2016

Three new heterometallic single‐molecule magnets (SMMs), [Dy2Ni2(bipy)2(RC6H4COO)10] [bipy=2,2′‐bipyridine, R=H (1), CH3 (2), and NO2 (3)], are synthesized solvothermally with different 3‐substituted benzoate ligands (RC6H4COO−), and are characterized both structurally and magnetically. Structural analyses reveal that the three entities are structurally analogous, exhibiting an approximately linear {Dy2Ni2} core bridged by ten carboxylate moieties from the RC6H4COO− ligands. A noncoordinating substituent group attached on the phenyl ring results in minor geometry distortions of 1–3, but causes a significant decrease in the Mulliken atomic charge on the axially shortest O donor through inductive and/or conjugative effects. Weak intramolecular ferromagnetic (for DyIII⋅⋅⋅DyIII) and antiferromagnetic (for DyIII⋅⋅⋅NiII) interactions with slightly different coupling strengths are observed in 1–3 at low temperatures, and the effective anisotropy barriers to block the magnetization reversal are 39.9, 25.9, and 2.8 cm−1, respectively, under zero direct‐current field. Ab initio calculations reveal that ligand substitution by the noncoordinating electron‐withdrawing/electron‐donating group can give rise to good modulation of the energy gap between the two lowest Kramers doublets, as well as the orientation of the local easy axis of the DyIII ion magnetization. The directions of the local easy axis of the DyIII ion can further influence the dipole spin–spin interaction and the molecular anisotropy of the entire molecule, which, together with the energy separation between the ground and first excited ground states, become the significant factors determining the effective anisotropy barrier heights of 1–3. These important results demonstrate that the charge distributions of the ligand‐field environments play essential roles in SMM performance, which should be considered seriously and utilized efficiently during the rational design of new, more feasible and practical SMMs.
Chirality Transfer in Gold(I)‐Catalysed Hydroalkoxylation of 1,3‐Disubstituted Allenes
Authors: Webster Stacey , Sutherland Daniel R. , Lee Ai‐Lan
Published: November 2016

Gold(I)‐catalysed intermolecular hydroalkoxylation of enantioenriched 1,3‐disubstituted allenes was previously reported to occur with poor chirality transfer due to rapid allene racemisation. The first intermolecular hydroalkoxylation of allenes with efficient chirality transfer is reported here, exploiting conditions that suppress allene racemisation. A full substrate scope study reveals that excellent regio‐ and stereoselectivities are achieved when a σ‐withdrawing substituent is present.
meso–meso‐Linked Diarylamine‐Fused Porphyrin Dimers
Authors: Fukui Norihito , Yorimitsu Hideki , Osuka Atsuhiro
Published: November 2016

A meso–meso‐linked diphenylamine‐fused porphyrin dimer and its methoxy‐substituted analogue were synthesized from a meso–meso‐linked porphyrin dimer by a reaction sequence involving Ir‐catalyzed β‐selective borylation, iodination, meso‐chlorination, and SNAr reactions with diarylamines followed by electron‐transfer‐mediated intramolecular double C−H/C−I coupling. While these dimers commonly display characteristic split Soret bands and small oxidation potentials, they produced different products upon oxidation with tris(4‐bromophenyl)aminium hexachloroantimonate. Namely, the diphenylamine‐fused porphyrin dimer was converted into a dicationic closed‐shell quinonoidal dimer, while the methoxy‐substituted dimer gave a meso–meso, β‐β doubly linked porphyrin dimer.
Modelling Chemical Reasoning to Predict and Invent Reactions
Authors: Segler Marwin H. S. , Waller Mark P.
Published: November 2016

The ability to reason beyond established knowledge allows organic chemists to solve synthetic problems and invent novel transformations. Herein, we propose a model that mimics chemical reasoning, and formalises reaction prediction as finding missing links in a knowledge graph. We have constructed a knowledge graph containing 14.4 million molecules and 8.2 million binary reactions, which represents the bulk of all chemical reactions ever published in the scientific literature. Our model outperforms a rule‐based expert system in the reaction prediction task for 180 000 randomly selected binary reactions. The data‐driven model generalises even beyond known reaction types, and is thus capable of effectively (re‐)discovering novel transformations (even including transition metal‐catalysed reactions). Our model enables computers to infer hypotheses about reactivity and reactions by only considering the intrinsic local structure of the graph and because each single reaction prediction is typically achieved in a sub‐second time frame, the model can be used as a high‐throughput generator of reaction hypotheses for reaction discovery.
Control of the Termination Mechanism in Radical Polymerization by Viscosity: Selective Disproportionation in Viscous Media
Authors: Nakamura Yasuyuki , Ogihara Tasuku , Hatano Sayaka , Abe Manabu , Yamago Shigeru
Published: November 2016

The termination mechanism of radical polymerization, that is, disproportionation (Disp) versus combination (Comb), determines the chain length and end‐group structure of the resulting polymer as well as polymer properties, and yet factors governing the mechanism are still unclear. Furthermore, no attempts have been made to control the mechanism. Here, the effects of temperature and viscosity on the termination of methyl methacrylate (MMA) and styrene (St) polymerization were elucidated by using small molecular model‐radicals and the corresponding polymer radicals in various solvents. The results showed that Disp was preferred over Comb if the temperature was decreased and the viscosity of the media was increased for all the radicals examined. Although the temperature effect on the Disp/Comb selectivity is counterintuitive because Disp should be favored entropically over Comb considering the decrease in the number of polymer chains in Comb, the results clearly showed that the observed inverse temperature effect was a result of the viscosity effect. Disp was favored over Comb at lower temperatures and in more viscous solvents because the transition state leading to Disp is more flexible than that for Comb. Because of the significant viscosity effect, Disp selectively occurred in highly viscous solvents; the Disp/Comb selectivity was 97/3 in both MMA and St termination. For the first time, the termination mechanism was intentionally controlled and such a high Disp selectivity was observed. In particular, the termination mechanism in St is described as Comb in textbooks, but nearly complete inversion of the selectivity from Comb to Disp is realized by simply changing the viscosity of the media.
Advanced Magnetic Resonance Techniques for the Structural Characterization of Aminoxyl Radicals and Their Inorganic–Organic Nanocomposite Systems
Authors: Eckert Hellmut
Published: November 2016

Electron and nuclear spins are extremely sensitive probes of their local structural and dynamic surroundings. Their Zeeman energy levels are modified by different types of local magnetic and electric fields created by their structural environment, which influence their magnetic resonance condition. For this reason, electron spin resonance (ESR) and nuclear magnetic resonance (NMR) spectroscopies have become extremely powerful tools of structural analysis, which are being widely used for the structural characterization of complex solids. Following a brief introduction into the basic theoretical foundations the most commonly used techniques and their application towards the structural characterization of paramagnetic solids based on aminoxyl radicals and their inorganic–organic nanocomposites will be described. Both ESR and NMR observables are useful for monitoring intermolecular interactions between unpaired electron spins, which are particularly important for the design of organically based ferromagnetic systems. ESR and NMR methods based on this effect can be used for monitoring the synthesis of polynitroxides and for evaluating the catalytic function of aminoxyl intercalation compounds. Finally, the sensitivity of ESR signals to motional dynamics can be exploited for characterizing molecule‐surface interactions in nanocomposite systems. In the context of the latter work recently developed signal enhancement strategies are described, using polarization transfer from electron spins to nuclear spins for NMR spectroscopic detection.
1H‐ und 13C‐NMR‐Spektroskopie
Authors: Findeisen Matthias , Siehl Hans‐Ullrich , Berger Stefan
Published: November 2016

Der gegenwärtige Stand der Routine 1D 1H‐ und 13C‐NMR‐Spektroskopie wird geschildert. Nach einer knappen Einführung in die zu Grunde liegende Theorie werden die zurzeit verfügbaren Spektrometer und Softwaresysteme diskutiert. Anhand eines Beispiels aus der Naturstoffchemie wird die Vorgehensweise bei der Analyse der Spektren erläutert.
Positive cooperativity of CaSiO3 and platinum‐tin catalyst in reaction of acetic acid to ethanol
Authors: Zhang Jianqiang , Luo Jian , Gao Jun , Liu Dianhua
Published: November 2016

Catalytic hydrogenation of acetic acid to ethanol was investigated in a fixed‐bed micro‐reactor with calcium silicate‐modified platinum‐tin catalyst at mild reaction condition. The modified catalyst exhibited excellent performance for the ethanol synthesis process at relatively low pressure. According to the results of H2‐pulse chemisorption experiments, the introduction of calcium silicate promoted the dispersion of platinum particles. The NH3‐TPD and H2‐TPR results showed the decrease of acid content on catalyst surface and the enhancement of reducibility after the CaSiO3 modification. Additionally, the results of XPS indicated that Sn (0) was emergent and Pt (2+) was sharply decreased after reduction. Both the H2‐TPR and XPS results supported the formation of Pt‐Sn alloy during the reduction process at 623 K. The Pt‐Sn alloy changed the electron density and benefited the free hydrogen dissociation and hydrogenation. The enhancement of reaction temperature and pressure both promoted acetic acid conversion. The kinetic model of power‐function type was established to describe the process of hydrogenation. The results of residual analysis confirmed that the raised kinetic model for acetic acid to ethanol reaction was suitable.
Rhodium(III)/Amine Synergistically Catalyzed Enantioselective Alkylation of Aldehydes with α,β‐Unsaturated 2‐Acyl Imidazoles
Authors: Gong Jun , Li Kuan , Qurban Saira , Kang Qiang
Published: November 2016

A synergistic catalysis combination of chiral‐at‐metal rhodium complex and amine catalyst was developed for enantioselective alkylation of aldehydes with α,β‐unsaturated 2‐acyl imidazoles. The corresponding adducts were obtained in good yields with excellent enantioselectivities (up to 99% ee).
Quantifying the suitability of CIE D50 and a simulators based on LED light sources
Authors: Gu H.T. , Pointer M.R. , Liu X.Y. , Ronnier Luo M.
Published: November 2016

In this study, two psychophysical experiments, colour‐difference assessment and colour‐appearance estimation, were conducted to investigate the perceived quality of four CIE illuminant simulators, including two simulators based on LED light sources. The perceived colour‐differences of 30 metameric pairs, seen under the different simulators, were evaluated by 10 colour‐normal observers using the gray scale method and the colour appearance of the colour inconstant sample in each pair assessed in a magnitude estimation method. Colorimetric measures revealed that LED simulators can achieve the desired quality according to the relevant ISO and CIE standards. The results of the experiments showed that an LED simulator outperformed the conventional fluorescent lamp‐based simulator for the CIE illuminant D50 condition. In addition, an LED simulator worked almost equally well as a conventional simulator for simulating CIE illuminant A. These findings strongly indicated the good quality of LED simulators based on a limited number of channels, and the superiority of LED technology. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 408–418, 2017
New Method to Study Ion–Molecule Reactions at Low Temperatures and Application to the Reaction
Authors: Allmendinger Pitt , Deiglmayr Johannes , Schullian Otto , Höveler Katharina , Agner Josef A. , Schmutz Hansjürg , Merkt Frédéric
Published: November 2016

Studies of ion–molecule reactions at low temperatures are difficult because stray electric fields in the reaction volume affect the kinetic energy of charged reaction partners. We describe a new experimental approach to study ion–molecule reactions at low temperatures and present, as example, a measurement of the
reaction with the
ion prepared in a single rovibrational state at collision energies in the range Ecol/kB=5–60 K. To reach such low‐collision energies, we use a merged‐beam approach and observe the reaction within the orbit of a Rydberg electron, which shields the ions from stray fields. The first beam is a supersonic beam of pure ground‐state H2 molecules and the second is a supersonic beam of H2 molecules excited to Rydberg–Stark states of principal quantum number n selected in the range 20–40. Initially, the two beams propagate along axes separated by an angle of 10°. To merge the two beams, the Rydberg molecules in the latter beam are deflected using a surface‐electrode Rydberg–Stark deflector. The collision energies of the merged beams are determined by measuring the velocity distributions of the two beams and they are adjusted by changing the temperature of the pulsed valve used to generate the ground‐state H2 beam and by adapting the electric‐potential functions applied to the electrodes of the deflector. The collision energy is varied down to below Ecol/kB=10 K, that is, below Ecol≈1 meV, with an energy resolution of 100 μeV. We demonstrate that the Rydberg electron acts as a spectator and does not affect the cross sections, which are found to closely follow a classical Langevin‐capture model in the collision energy range investigated. Because all neutral atoms and molecules can be excited to Rydberg states, this method of studying ion–molecule reactions is applicable to other reactions involving singly charged cations.
Insights into the Gelating Abilities of Ricinelaidic Acid and its Ammonium Salts: How do Stereochemistry, Charge, and Chain Lengths Control Gelation of a Long‐Chain Alkenoic Acid?
Authors: Zhang Mohan , Weiss Richard G.
Published: November 2016

The gelating abilities of ricinelaidic acid (d‐REA), the trans‐isomer of ricinoleic acid (d‐RA), and a series of its alkylammonium and alkane‐α,ω‐diammonium salts have been examined in a wide range of organic liquids. The gelation efficiency of the trans acid is much better than that of the cis, although neither is as efficient as is the completely saturated molecular gelator analogue, (R)‐12‐hydroxystearic acid (d‐12HSA). The formation of ammonium salts also improves the gelation ability of d‐REA in high polarity liquids. The gelating properties are highly dependent upon the chain length of the alkyl group of the alkylammonium salts, but not very dependent on the chain length of the alkane‐α,ω‐diammonium salts. Structural insights from Fourier transform infrared spectroscopy and powder X‐ray diffraction indicate that the absence or presence of unsaturation, the incorporation of (charged) ammonium centers, and the different chain lengths of the alkylammonium salts lead to different packing arrangements and different strengths of H‐bonding interactions within the gel assemblies of the d‐REA derivatives. Insights into the relationships among the various systematic structural changes to d‐REA and the properties of their aggregated structures, including the gel states, are provided.
The Role of Entropy in Nanoparticle Agglomeration
Authors: Kätelhön Enno , Sokolov Stanislav V. , Bartlett Thomas R. , Compton Richard G.
Published: November 2016

Agglomeration processes in non‐interacting particle systems can be understood from a thermodynamic point of view. If the enthalpy of agglomeration is negligible, the distribution of agglomeration states adopts the state of highest entropy. Herein, we provide the exact analytical solution to the mole fractions of agglomerates comprising i monomers, xi=2−i.
3D bioengineered tissues: From advancements in in vitro safety to new horizons in disease modeling
Authors: Hardwick RN , Viergever C , Chen AE , Nguyen DG
Published: November 2016

Research aimed at more fully emulating human biology in vitro has rapidly progressed in recent years with advancements in 3D tissue engineering and microphysiological systems. The initial target of such systems has been directed towards drug and chemical safety assessment, with the goal of improving sensitivity and predictive capabilities. Here we discuss recent developments of in vitro organ culture systems, and their future applications in modeling human disease.
Numerical design of Metal‐Organic Vapour Phase Epitaxy process for gallium nitride epitaxial growth
Authors: Skibinski J. , Caban P. , Wejrzanowski T. , Oliver G.J. , Kurzydlowski K.J.
Published: November 2016

The paper presents the results of numerical simulations and experimental measurements of the epitaxial growth of gallium nitride in Metal Organic Vapor Phase Epitaxy within a AIX‐200/4RF‐S reactor. The aim was to develop optimal process conditions for obtaining the most homogeneous crystal layer. Since there are many factors influencing the chemical reactions on the crystal growth area such as: temperature, pressure, gas composition or reactor geometry, it is difficult to design an optimal process. In this study various process pressures and hydrogen volumetric flow rates have been considered. Due to the fact that it is not economically viable to test every combination of possible process conditions experimentally, detailed 3D modeling has been used to get an overview of the influence of process parameters. Numerical simulations increased the understanding of the epitaxial process by calculating the heat and mass transfer distribution during the growth of gallium nitride. Appropriate chemical reactions were included in the numerical model which allowed for the calculation of the growth rate of the substrate. The results obtained have been applied to optimize homogeneity of GaN film thickness and its growth rate.
New Mechanism for the Reduction of Vanadyl Acetylacetonate to Vanadium Acetylacetonate for Room Temperature Flow Batteries
Authors: Shamie Jack S. , Liu Caihong , Shaw Leon L. , Sprenkle Vincent L.
Published: November 2016

In this study, a new mechanism for the reduction of vanadyl acetylacetonate, VO(acac)2, to vanadium acetylacetonate, V(acac)3, is introduced. V(acac)3 has been studied for use in redox flow batteries (RFBs) for some time; however, contamination by moisture leads to the formation of VO(acac)2. In previous work, once this transformation occurs, it is no longer reversible because there is a requirement for extreme low potentials for the reduction to occur. Here, we propose that, in the presence of excess acetylacetone (Hacac) and free protons (H+), the reduction can take place between 2.25 and 1.5 V versus Na/Na+ via a one‐electron‐transfer reduction. This reduction can take place in situ during discharge in a novel hybrid Na‐based flow battery (HNFB) with a molten Na–Cs alloy as the anode. The in situ recovery of V(acac)3 during discharge is shown to allow the Coulombic efficiency of the HNFB to be ≈100 % with little or no capacity decay over cycles. In addition, utilizing two‐electron‐transfer redox reactions (i.e., V3+/V4+ and V2+/V3+ redox couples) per V ion to increase the energy density of RFBs becomes possible owing to the in situ recovery of V(acac)3 during discharge. The concept of in situ recovery of material can lead to more advances in maintaining the cycle life of RFBs in the future.
Regioselectivity and Reaction Mechanism of Ru‐Catalyzed Hydrogenolysis of Squalane and Model Alkanes
Authors: Nakagawa Yoshinao , Oya Shin‐ichi , Kanno Daisuke , Nakaji Yosuke , Tamura Masazumi , Tomishige Keiichi
Published: November 2016

The dependence of the C−C hydrogenolysis activity on reaction parameters and the structure of the substrate alkanes was investigated for Ru/CeO2 catalyst with very small (dispersion: H/Ru=0.89) Ru particles. The substrate concentration and reaction temperature did not have a significant effect on the selectivity pattern, except that methane production was promoted at high temperatures. However, the hydrogen pressure had a marked effect on the selectivity pattern. Ctertiary−C bond dissociation, terminal Csecondary−Cprimary bond dissociation, and fragmentation to form excess methane had negative reaction order with respect to hydrogen partial pressure, whereas Csecondary−Csecondary bond dissociation had an approximately zero reaction order. Therefore, a high hydrogen pressure is essential for the regioselective hydrogenolysis of Csecondary−Csecondary bonds in squalane. Ru/SiO2 catalyst with larger Ru particles showed similar changes in the product distribution during the change in hydrogen pressure. The reaction mechanism for each type of C−C bond dissociation is proposed based on reactivity trends and DFT calculations. The proposed intermediate species for the internal Csecondary−Csecondary dissociation, terminal Csecondary−Cprimary dissociation, and Ctertiary−C dissociation is alkyls, alkylidynes, and alkenes, respectively.
Understanding the Reaction Mechanism of Glycerol Hydrogenolysis over a CuCr2O4Catalyst
Authors: Yun Yang Sik , Kim Tae Yong , Yun Danim , Lee Kyung Rok , Han Jeong Woo , Yi Jongheop
Published: November 2016

The reaction mechanism of glycerol hydrogenolysis to 1,2‐propanediol over a spinel CuCr2O4catalyst was investigated by using DFT calculations. Theoretical models were developed from the results of experimental characterization. Adsorption configurations and energetics of the reactant, intermediates, final product, and transition states were calculated on Cu(1 1 1) and CuCr2O4(1 0 0). Based on our DFT results, we found that the formation of acetol is preferred to that of 3‐hydroxypropionaldehyde thermodynamically and kinetically on both surfaces. For glycerol hydrogenolysis to 1,2‐propanediol, the CuCr2O4surface is less exothermic but more kinetically favorable than the Cu surface. The low activation barrier during the reaction on the CuCr2O4surface is attributed to the unique surface structure; the cubic spinel structure provides a stable adsorption site on which reactants are allowed to be dehydrated and hydrogenated easily with the characteristic adsorption configuration. The role of the Cu and Cr atoms in a CuCr2O4surface were revealed. The results of reaction tests supported our theoretical calculations.
Mutiphase oscillator using dissipatively coupled transmission lines with regularly spaced tunnel diodes
Authors: Narahara Koichi
Published: November 2016

A generation scheme is proposed for multiphase oscillatory signals based on mutual synchronization of the oscillating pulse edges developed in point‐coupled transmission lines periodically loaded with tunnel diodes (TDs). When supplied with an appropriate voltage at the end of a TD line, a pulse edge is shown to exhibit a spatially extended limit‐cycle oscillation on the line. When two TD lines are dissipatively coupled, such edge oscillations are mutually synchronized such that two edges simultaneously pass the connecting cells. Based on this observation, the scheme employs multiple point‐coupled TD lines, wherein the first and last lines are linked at the same position. Its design criterion is obtained by applying the phase reduction method to the transmission equation of a TD line. In addition, several time‐domain calculations demonstrate the validity of the scheme. Copyright © 2016 John Wiley & Sons, Ltd.
Fine‐needle aspiration biopsy of pancreatic neuroendocrine tumors: Correlation between Ki‐67 index in cytological samples and clinical behavior
Authors: Díaz del Arco Cristina , Esteban López‐Jamar J. Miguel , Ortega Medina Luis , Díaz Pérez J. Ángel , Fernández Aceñero Ma Jesús
Published: November 2016

Background

Mitotic count in hematoxylin‐eosin stained slides and Ki‐67 index allow stratification of patients for prognosis and therapeutic decision making in pancreatic neuroendocrine tumors (PNETs). However, the utility of Ki‐67 determination in cytological material and its association to PNET prognosis are under discussion.

Methods

We have retrospectively reviewed all cases of EUS‐FNA cytology of pancreatic lesions performed in the Hospital Clínico San Carlos (Madrid) between 2006 and 2016. We have analyzed the potential association between the Ki‐67 estimation in PNET cytological material and patient outcomes.

Results

We identified 24 PNET cases. Mean age was 56.8 years and most patients were males (54%). PNETs were mainly located in the head and tail of the pancreas and the mean tumor size was 36 mm. Cell block from cytology was available in 12 cases (50%), and there were 19 G1, 2 G2, and 3 G3 tumors. All cases graded as G2 (2 patients) or G3 (three patients) on cytology were stage IV, and the 19 cases graded as G1 ranged from stages IA to IV. All patients with G2 tumors on cytology died due to PNET. Of the three patients with G3 lesions, two died of disease and the other died 2 months after diagnosis from causes other than PNET. 78% of the patients with G1 tumors are stable and currently being followed‐up.

Conclusion

Higher Ki‐67 index in cytology specimens portends a worse outcome, although some G1 tumors may progress or cause death. Diagn. Cytopathol. 2017;45:29–35. © 2016 Wiley Periodicals, Inc.
Abiotic proxies for predictive mapping of nearshore benthic assemblages: implications for marine spatial planning
Authors: McHenry Jennifer , Steneck Robert S. , Brady Damian C.
Published: November 2016

Marine spatial planning (MSP) should assist managers in guiding human activities toward sustainable practices and in minimizing user conflicts in our oceans. A necessary first step is to quantify spatial patterns of marine assemblages in order to understand the ecosystem's structure, function, and services. However, the large spatial scale, high economic value, and density of human activities in nearshore habitats often makes quantifying this component of marine ecosystems especially daunting. To address this challenge, we developed an assessment method that employs abiotic proxies to rapidly characterize marine assemblages in nearshore benthic environments with relatively high resolution. We evaluated this assessment method along 300 km of the State of Maine's coastal shelf (<100 m depth), a zone where high densities of buoyed lobster traps typically preclude extensive surveys by towed sampling gear (i.e., otter trawls). During the summer months of 2010–2013, we implemented a stratified‐random survey using a small remotely operated vehicle that allowed us to work around lobster buoys and to quantify all benthic megafauna to species. Stratifying by substrate, depth, and coastal water masses, we found that abiotic variables explained a significant portion of variance (37–59%) in benthic species composition, diversity, biomass, and economic value. Generally, the density, diversity, and biomass of assemblages significantly increased with the substrate complexity (i.e., from sand‐mud to ledge). The diversity, biomass, and economic value of assemblages also decreased significantly with increasing depth. Last, demersal fish densities, sessile invertebrate densities, species diversity, and assemblage biomass increased from east to west, while the abundance of mobile invertebrates and economic value decreased, corresponding mainly to the contrasting water mass characteristics of the Maine Coastal Current system (i.e., summertime current direction, speed, and temperature). Integrating modeled predictions with existing GIS layers for abiotic conditions allowed us to scale up important assemblage attributes to define key foundational ecological principles of MSP and to find priority regions where some bottom‐disturbing activities would have minimal impact to benthic assemblages. We conclude that abiotic proxies can be strong forcing functions for the assembly of marine communities and therefore useful tools for spatial extrapolations of marine assemblages in congested (heavily used) nearshore habitats.
Disordered eating behaviors among transgender youth: Probability profiles from risk and protective factors
Authors: Watson Ryan J. , Veale Jaimie F. , Saewyc Elizabeth M.
Published: November 2016

Purpose

Research has documented high rates of disordered eating for lesbian, gay, and bisexual youth, but prevalence and patterns of disordered eating among transgender youth remain unexplored. This is despite unique challenges faced by this group, including gender‐related body image and the use of hormones. We explore the relationship between disordered eating and risk and protective factors for transgender youth.

Methods

An online survey of 923 transgender youth (aged 14–25) across Canada was conducted, primarily using measures from existing youth health surveys. Analyses were stratified by gender identity and included logistic regressions with probability profiles to illustrate combinations of risk and protective factors for eating disordered behaviors.

Results

Enacted stigma (the higher rates of harassment and discrimination sexual minority youth experience) was linked to higher odds of reported past year binge eating and fasting or vomiting to lose weight, while protective factors, including family connectedness, school connectedness, caring friends, and social support, were linked to lower odds of past year disordered eating. Youth with the highest levels of enacted stigma and no protective factors had high probabilities of past year eating disordered behaviors.

Discussion

Our study found high prevalence of disorders. Risk for these behaviors was linked to stigma and violence exposure, but offset by social supports. Health professionals should assess transgender youth for disordered eating behaviors and supportive resources. © 2016 Wiley Periodicals, Inc.(Int J Eat Disord 2017; 50:515–522)
Environmental (in)dependence of a hybrid zone: Insights from molecular markers and ecological niche modeling in a hybrid zone ofOriganum(Lamiaceae) on the island of Crete
Authors: Bariotakis Michael , Koutroumpa Konstantina , Karousou Regina , Pirintsos Stergios A.
Published: November 2016

The role of environment and the relative significance of endogenous versus exogenous selection in shaping hybrid zones have been crucial issues in the studies of hybridization. Recent advances in ecological niche modeling (ENM) offer new methodological tools, especially in combination with the genotyping of individuals in the hybrid zone. Here, we study the hybrid zone between the widely known spicesOriganum onitesandOriganum vulgaressp.hirtumin Crete. We analyze the genetic structure of both parental taxa and their hybridOriganum × intercendensusingAFLPmarkers on 15 sympatric and 12 allopatric populations and employ ecological niche modeling and niche similarity tests to study their niche patterns. We complement these analyses with seed viability measurements. Our study revealed that the hybridizing taxaO. onitesandO. vulgaressp.hirtumand the resulting genotypic classes showed geographical and environmental niche similarities based on the predictions ofENMs and the subsequent similarity tests. The occurrence of the hybrid zone is not directly dependent on environmental factors which favor the fitness of the hybrid compared to the parental taxa, but rather on aspects such as historical factors and management practices, which may contribute to the localization and maintenance of the contact zone between parental species. Our results suggest that if a minimum required niche differentiation between genotypic classes is not achieved, environmental dependence might not have a prominent role on the outcome of the hybridization.
Generalized joint attribute modeling for biodiversity analysis: median‐zero, multivariate, multifarious data
Authors: Clark James S. , Nemergut Diana , Seyednasrollah Bijan , Turner Phillip J. , Zhang Stacy
Published: November 2016

Probabilistic forecasts of species distribution and abundance require models that accommodate the range of ecological data, including a joint distribution of multiple species based on combinations of continuous and discrete observations, mostly zeros. We develop a generalized joint attribute model (GJAM), a probabilistic framework that readily applies to data that are combinations of presence‐absence, ordinal, continuous, discrete, composition, zero‐inflated, and censored. It does so as a joint distribution over all species providing inference on sensitivity to input variables, correlations between species on the data scale, prediction, sensitivity analysis, definition of community structure, and missing data imputation. GJAM applications illustrate flexibility to the range of species‐abundance data. Applications to forest inventories demonstrate species relationships responding as a community to environmental variables. It shows that the environment can be inverse predicted from the joint distribution of species. Application to microbiome data demonstrates how inverse prediction in the GJAM framework accelerates variable selection, by isolating effects of each input variable's influence across all species.
Vegetation dynamics and rainfall sensitivity for different vegetation types of the Australian continent in the dry period 2002–2010
Authors: Liu N. , Harper R.J. , Dell B. , Liu S. , Yu Z.
Published: November 2016

Over the past 100 years, Australia has experienced pronounced changes in rainfall patterns, which in south‐western Australia (SWAU) has resulted in both a >50% decrease of runoff since 1975 and effects on vegetation health. Resolving the dynamics of vegetation and climate is a prerequisite for predicting the response of vegetation to future climates and carbon mitigation objectives. With multi‐resource vegetation indices (VIs; normalized difference vegetation index and leaf area index) and gridded climate data, this paper examines vegetation dynamics and sensitivity to rainfall change on the Australian continent for the past long drought period (2002–2010). We found that rainfall and VIs declined across 90% and 80% of the whole continent, respectively, compared to the baseline period of 2000–2001. The most dramatic declines in VIs occurred in open shrublands near the center of Australia and in SWAU, coinciding with significant reductions in rainfall and soil moisture. Overall, a strong relationship between water (rainfall and soil moisture) and VIs was detected in places where rainfall declined dramatically (up to 5 mm/year since 1970). For five major vegetation types, croplands showed the highest sensitivity to water change, followed by grasslands and woody savanna. Moderate sensitivity of open shrublands to water change was found, while evergreen broadleaf forests only showed a slight sensitivity to soil moisture change. Although there was no consistent significant relationship between rainfall and VIs of evergreen broadleaf forests, forests in south‐eastern Australia, where rainfall had declined since 1997, have become more sensitive to rainfall change than in SWAU. Our results provide evidence that, at this scale of assessment and with interpolated data sets, a lasting reduced rainfall pattern has been a key factor constraining vegetation growth over the Australian continent.
Heterogeneities in the infection process drive ranavirus transmission
Authors: Brunner Jesse L. , Beaty Lynne , Guitard Alexandra , Russell Deanna
Published: November 2016

Transmission is central to our understanding and efforts to control the spread of infectious diseases. Because transmission generally requires close contact, host movements and behaviors can shape transmission dynamics: random and complete mixing leads to the classic density‐dependent model, but if hosts primarily interact locally (e.g., aggregate) or within groups, transmission may saturate. Manipulating host behavior may thus change both the rate and functional form of transmission. We used the ranavirus–wood frog (Lithobates sylvaticus) tadpole system to test whether transmission rates reflect contacts, and whether the functional form of transmission can be influenced by the distribution of food in mesocosms (widely dispersed, promoting random movement and mixing vs. a central pile, promoting aggregations). Contact rates increased with density, as expected, but transmission rapidly saturated. Observed rates of transmission were not explained by observed contact rates or the density‐dependent model, but instead transmission in both treatments followed models allowing for heterogeneities in the transmission process. We argue that contacts were not generally limiting, but instead that our results are better explained by heterogeneities in host susceptibility. Moreover, manipulating host behavior to manage the spread of infectious disease may prove difficult to implement.