bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparative Studies of Thermally Induced Homolytic CarbonCarbon Bond Cleavage Reactions of Strained Dicarba[2]ferrocenophanes and Their Ring‐Opened Oligomers and Polymers
Authors: Russell Andrew D. , Gilroy Joe B. , Manners Ian 
Published: March 2014

AbstractReactivity studies of dicarba[2]ferrocenophanes and also their corresponding ring‐opened oligomers and polymers have been conducted in order to provide mechanistic insight into the processes that occur under the conditions of their thermal ring‐opening polymerisation (ROP) (300 °C). Thermolysis of dicarba[2]ferrocenophane rac‐[Fe(η5‐C5H4)2(CHPh)2] (rac‐14; 300 °C, 1 h) does not lead to thermal ROP. To investigate this system further, rac‐14 was heated in the presence of an excess of cyclopentadienyl anion, to mimic the postulated propagating sites for thermally polymerisable analogues. This afforded acyclic [(η5‐C5H5)Fe(η5‐C5H4)‐CH2Ph] (17) through cleavage of both a FeCp bond and also the CC bond derived from the dicarba bridge. Evidence supporting a potential homolytic CC bond cleavage pathway that occurs in the absence of ring‐strain was provided through thermolysis of an acyclic analogue of rac‐14, namely [(η5‐C5H5)Fe(η5‐C5H4)(CHPh)2‐C5H5] (15; 300 °C, 1 h), which also afforded ferrocene derivative 17. This reactivity pathway appears general for post‐ROP species bearing phenyl substituents on adjacent carbons, and consequently was also observed during the thermolysis of linear polyferrocenylethylene [Fe(η5‐C5H4)2(CHPh)2]n (16; 300 °C, 1 h), which was prepared by photocontrolled ROP of rac‐14 at 5 °C. This afforded ferrocene derivative [Fe(η5‐C5H4CH2Ph)2] (23) through selective cleavage of the H(Ph)CC(Ph)H bonds in the dicarba linkers. These processes appear to be facilitated by the presence of bulky, radical‐stabilising phenyl substituents on each carbon of the linker, as demonstrated through the contrasting thermal properties of unsubstituted linear trimer [(η5‐C5H5)Fe(η5‐C5H4)(CH2)2(η5‐C5H4)Fe(η5‐C5H4)(CH2)2(η5‐C5H4)Fe(η5‐C5H5)] (29) with a H2CCH2 spacer, which proved significantly more stable under analogous conditions. Evidence for the radical intermediates formed through CC bond cleavage was detected through high‐resolution mass spectrometric analysis of co‐thermolysis reactions involving rac‐14 and 15 (300 °C, 1 h), which indicated the presence of higher molecular weight species, postulated to be formed through cross‐coupling of these intermediates.
Single‐Step Gas‐Phase Polyperfluoroalkylation of Naphthalene Leads to Thermodynamic Products
Authors: San Long K. , Bukovsky Eric V. , Kuvychko Igor V. , Popov Alexey A. , Strauss Steven H. , Boltalina Olga V. 
Published: March 2014

AbstractHigh‐temperature gas‐phase, solvent‐ and catalyst‐free reaction of naphthalene with an excess of RFI reagent (RFCF3, C2F5, n‐C3F7, and n‐C4F9) was used for the first time to produce a series of highly perfluoroalkylated naphthalene products NAPH(RF)n with n=2–5. Four 95+ % pure 1,3,5,7‐NAPH(RF)4 with RFCF3, C2F5, n‐C3F7, and n‐C4F9 were isolated using a simple chromatography‐free procedure. These new compounds were fully characterized by 19F and 1H NMR spectroscopy, X‐ray crystallography (for RFCF3 and C2F5), atmospheric‐pressure chemical ionization mass spectrometry, and cyclic and square‐wave voltammetry. DFT calculations confirm that the proposed synthesis yields the most stable isomers that have not been accessed by alternative preparation techniques.
Formal Total Synthesis of Kendomycin by Way of Alkyne Metathesis/Gold Catalysis
Authors: Hoffmeister Laura , Persich Peter , Fürstner Alois 
Published: March 2014

AbstractIn an attempt to study the ability of the latest generation of alkyne metathesis catalysts to process sterically hindered substrates, two different routes to the bacterial metabolite kendomycin (1) were explored. Whereas the cyclization of the overcrowded arylalkyne 39 and related substrates turned out to be impractical or even impossible, ring closure of the slightly relaxed diyne 45 was achieved in excellent yield under notably mild conditions with the aid of the molybdenum alkylidyne 2 endowed with triphenylsilanolate ligands. The resulting cycloalkyne 46 was engaged into a gold‐catalyzed hydroalkoxylation, which led to benzofuran 47 that had already previously served as a late‐stage intermediate en route to 1.
Dinuclear Ru–Aqua Complexes for Selective Epoxidation Catalysis Based on Supramolecular Substrate Orientation Effects
Authors: Di Giovanni Carlo , Poater Albert , Benet‐Buchholz Jordi , Cavallo Luigi , Solà Miquel , Llobet Antoni 
Published: March 2014

AbstractRu–aqua complex {[RuII(trpy)(H2O)]2(μ‐pyr‐dc)}+ is a powerful epoxidation catalyst for a wide range of linear and cyclic alkenes. High turnover numbers (TNs), up to 17000, and turnover frequencies (TOF), up to 24120 h−1 (6.7 s−1), have been obtained using PhIO as oxidant. This species presents an outstanding stereospecificity for both cis and trans olefins towards the formation of their corresponding cis and trans epoxides. In addition, it shows different reactivity to cis and trans olefins due to a substrate orientation supramolecular effect transmitted by its ligand scaffold. This effect together with the impressive reaction rates are rationalized using electrochemical techniques and DFT calculations.
Supercritical Carbon Dioxide Assisted Deposition of Fe3O4 Nanoparticles on Hierarchical Porous Carbon and Their Lithium‐Storage Performance
Authors: Wang Lingyan , Zhuo Linhai , Zhang Chao , Zhao Fengyu 
Published: March 2014

AbstractA composite of highly dispersed Fe3O4 nanoparticles (NPs) anchored in three‐dimensional hierarchical porous carbon networks (Fe3O4/3DHPC) as an anode material for lithium‐ion batteries (LIBs) was prepared by means of a deposition technique assisted by a supercritical carbon dioxide (scCO2)‐expanded ethanol solution. The as‐synthesized Fe3O4/3DHPC composite exhibits a bimodal porous 3D architecture with mutually connected 3.7 nm mesopores defined in the macroporous wall on which a layer of small and uniform Fe3O4 NPs was closely coated. As an anode material for LIBs, the Fe3O4/3DHPC composite with 79 wt % Fe3O4 (Fe3O4/3DHPC‐79) delivered a high reversible capacity of 1462 mA h g−1 after 100 cycles at a current density of 100 mA g−1, and maintained good high‐rate performance (728, 507, and 239 mA h g−1 at 1, 2, and 5 C, respectively). Moreover, it showed excellent long‐term cycling performance at high current densities, 1 and 2 A g−1. The enhanced lithium‐storage behavior can be attributed to the synergistic effect of the porous support and the homogeneous Fe3O4 NPs. More importantly, this straightforward, highly efficient, and green synthetic route will definitely enrich the methodologies for the fabrication of carbon‐based transition‐metal oxide composites, and provide great potential materials for additional applications in supercapacitors, sensors, and catalyses.
Electrochemical Degradation of Carbamazepine in Aqueous Solutions – Optimization of Kinetic Aspects by Design of Experiments
Authors: Palo Patricia , Dominguez Joaquin R. , Sánchez‐Martín Jesús , González Teresa 
Published: March 2014

AbstractElectrodegradation of simulated pharmaceutical wastewaters was performed and optimized according to response surface methodology. To this end, carbamazepine (CBZ) was used as a model compound and a design of experiments was planned for evaluating the influence of two main variables in the electrochemical process: initial CBZ concentration (in logarithm terms) and the current density. Target variable was an apparent first‐order kinetic constant (k) designed ad hoc. Interaction of variables was confirmed and an optimum k constant of 0.72 min−1 was obtained. CBZ was also removed from real wastewater matrices, such as urban wastewater or surface water from river and lake.
High‐Throughput Synthesis of Peptide α‐Thioesters: A Safety Catch Linker Approach Enabling Parallel Hydrogen Fluoride Cleavage
Authors: Brust Andreas , Schroeder Christina I. , Alewood Paul F. 
Published: March 2014

AbstractPeptide α‐thioesters are fundamental building blocks in peptide and protein science, providing powerful tools for peptide medicinal chemistry. The application of peptide α‐thioesters in native chemical ligation reactions has enabled synthetic access to cysteine‐rich peptides and proteins, cyclic peptides as well as labeled and chemically modified biomolecules. An efficient high‐throughput synthesis of peptide α‐thioester building blocks would be beneficial for many medicinal chemical applications that require peptides and proteins. Herein we present a novel synthetic route to cysteine‐rich peptide α‐thioesters using a safety catch linker that enables a parallel synthetic strategy for chemical protein synthesis. ACP(68–75), bradykinin and dynorphin(1–13) were synthesized via Boc chemistry in their thioester form on a safety catch amide linker (SCAL), employing polystyrene‐ or poly(ethylene glycol)‐based resins, compartmentalized in tea bags. This compartmentalized resin/linker strategy facilitated a parallel hydrogen fluoride cleavage in which each peptide thioester was subsequently cyclized by native chemical ligation, demonstrating the utility of this approach. A naturally occurring bioactive cyclic peptide, the sunflower trypsin inhibitor SFTI‐1, was synthesized to demonstrate the viability of this method to access important peptide biomolecules.
Cystic pancreatic neuroendocrine tumors: The value of cytology in preoperative diagnosis
Authors: Morales‐Oyarvide Vicente , Yoon Won Jae , Ingkakul Thun , Forcione David G. , Casey Brenna W. , Brugge William R. , Fernández‐del Castillo Carlos , Pitman Martha B. 
Published: March 2014

BACKGROUNDCystic pancreatic neuroendocrine tumors (cPanNETs) account for 13% to 17% of PanNETs. Although the value of endoscopic ultrasound (EUS) imaging and cyst fluid analysis (CFA) in their preoperative diagnosis has been well described, limited information is available about the diagnostic role of cytology samples obtained from fine‐needle aspiration (FNA).METHODSCytopathology records between 1992 and 2013 were searched for all reports of cysts interpreted as PanNET. Patient demographics, clinical and radiologic information, CFA, histopathology, and cytopathology findings were recorded. Performance characteristics of cytology and EUS for the accurate diagnosis of cPanNET were calculated.RESULTSIn total, 35 FNAs from 33 patients with cPanNETs were identified, and 34 EUS were performed. Cytology made a specific diagnosis of a cPanNET in 71% of the biopsies compared with a specific diagnosis by EUS in 38% of cases. An interpretation of suspicious for cPanNET was given in 77% of cases by cytology and in 47% by EUS. Cytology identified 86% of the lesions as high‐risk pancreatic cysts compared with 56% by EUS. Diagnostic morphology was present on both cytology and cell block preparations in 60% of aspirates, on cytology only in 20%, and on cell block only in 20%. CFA was performed on 51% cyst fluids. All cysts but 1 revealed low carcinoembryonic antigen levels (range, 0.2 to >500 ng/mL; mean, 29.5 ng/mL), and amylase levels were <500 U/L in all but 2 cases (range, 16‐1493 U/L; mean, 205 U/L).CONCLUSIONSCytology is the most accurate test for preoperative diagnosis of cPanNETs. EUS is insufficiently accurate for independent diagnosis, and carcinoembryonic antigen and amylase analyses are noncontributory. Cancer (Cancer Cytopathol) 2014;122:435–444. © 2014 American Cancer Society.
Molecular Theory of Phase Separation in Nematic Liquid Crystals Doped with Spherical Nanoparticles
Authors: Osipov Mikhail A. , Gorkunov Maxim V. 
Published: March 2014

AbstractA molecular‐statistical theory is developed, which enables one to describe the nematic–isotropic phase transition in liquid crystals doped with spherical nanoparticles taking into account the effects of phase separation. It has been shown that in the case of strong interaction between nanoparticles and mesogenic molecules the nematic nanocomposite possesses a number of unexpected properties. In particular, the nematic–isotropic co‐existence region appears to be very broad, and the system either undergoes a direct transition from the isotropic phase into the phase‐separated state, or undergoes the transition into the homogeneous nematic phase first and then phase‐separates at a lower temperature. Phase separation does not occur at all if the concentration of the nanoparticles is sufficiently low, and in some cases it takes place only within a finite region of nanoparticle concentration. A number of temperature–concentration phase diagrams is presented and the molar fractions of nanoparticles in the co‐existing isotropic and nematic phases are calculated numerically as functions of temperature.
A Time‐Dependent DFT Study of the Absorption and Fluorescence Properties of Graphene Quantum Dots
Authors: Zhao Meilian , Yang Feng , Xue Ying , Xiao Dan , Guo Yong 
Published: March 2014

AbstractAbsorption and fluorescence spectra of graphene quantum dots (GQDs) have been computed by using time‐dependent density functional theory (TDDFT). Different functionals, including PBE, TPSSh, B3LYP, PBE0, CAM‐B3LYP, and LC‐ωPBE, have been tested and B3LYP/6‐31G(d) has been proven to be the most accurate method for our work. The bulk solvent effects of toluene and dichloromethane have been assessed by using the polarizable continuum model (PCM). The absorption wavelength of GQDs in solvents is red‐shifted compared with that in the gas phase. Edge functionalization effects analysis shows that a small number of substituted groups on GQDs induce a small redshift whereas a large redshift occurs when the edges of GQDs are all decorated. Little difference in the fluorescent emission was observed in solvents and in the gas phase. Molecular orbital transition and transition density matrix analysis have been performed. The electronic transition mainly occurs in the middle part of the structure of C132. The strong absorption of C132 corresponds to a S0→S3 transition and the fluorescence emission is ascribed to a S1→S0 transition, which indicates that Kasha’s rule is obeyed.
Characterization and Distribution of Poly(3‐hexylthiophene) Phases in an Annealed Blend Film
Authors: Hu Rong , Zhang Wei , Wang Peng , Qin Yujun , Liang Ran , Fu Li‐Min , Zhang Jian‐Ping , Ai Xi‐Cheng 
Published: March 2014

AbstractThe characteristic absorption spectra of three kinds of phases, the isolated, ordered, and disordered phases, in a solvent‐vapor annealed poly(3‐hexylthiophene)/[6,6]‐phenyl‐C61‐butyric acid methyl ester (P3HT/PCBM) blend film were studied by means of spectroelectrochemistry (SEC) and time‐resolved absorption spectroscopy (TAS). The results reveal that the content of three phases are 12 % isolated, 37 % ordered, and 51 % disordered for the annealed P3HT neat film, and 25 % isolated, 31 % ordered, and 44 % disordered for the annealed P3HT/PCBM blend film. The vertical distribution of the different phases in the blend film was studied by SEC, and the results show that the ordered and isolated phases are mainly distributed in the top and in the bottom of the annealed films, respectively, while the disordered phase is mainly distributed in the middle and the bottom of the films.
Photophysical Evidence of Charge‐Transfer‐Complex Pairs in Mixed‐Linker 5‐Amino/5‐Nitroisophthalate CAU‐10
Authors: Ferrer Belén , Alvaro Mercedes , Baldovi Hermenegildo G. , Reinsch Helge , Stock Norbert 
Published: March 2014

AbstractThe photochemistry of two isostructural metal–organic frameworks based on 5‐amino/5‐formamidoisophthalate (CAU‐10‐NH2/NHCHO) or mixed‐linker 5‐amino/5‐formamido‐ and 5‐nitroisophthalate (CAU‐10‐NO2/NH2/NHCHO) has been studied using laser flash photolysis. 355 nm excitation of CAU‐10‐NH2/NHCHO leads to a transient absorption spectrum characterized by a broad continuous absorption from 380 to 800 nm that was attributed to the presence of holes (440 nm) and electrons (600 nm) based on iPrOH and N2O quenching, respectively. In contrast, no transients were observed for the isostructural mixed‐linker CAU‐10‐NO2/NH2/NHCHO, data that is compatible with the uniform distribution of linkers 5‐amino/5‐formamido/5‐nitroisophthalate as charge‐transfer complex pairs. The same effect of quenching of 5‐aminoisophthalate transients by 5‐nitroisophthalate was also observed in aqueous solution (pH 9) but with much lower strength. Using a simple Stern–Volmer formalism allowed the estimation of the interaction of 5‐aminoisophthalate with 5‐nitroisophthalate in MOF to be 5.2×104 times stronger than in the aqueous phase.
A Facile, Template‐Free Synthesis of AgCl Hierarchical Architectures: Precursors of Highly Efficient Visible‐Light Plasmonic Photocatalysts of Ag@AgCl
Authors: Wang Yu , Chen Gang , Di Andi , Xu Haiming 
Published: March 2014

AbstractThis paper describes a facile, template‐free synthesis of AgCl hierarchical structures by a gas–liquid interfacial method and the morphology of AgCl (microrods or film) can be conveniently varied or controlled by changing the solvents of AgNO3 without using any surfactants. The AgCl composites were then photoreduced to form highly efficient visible‐light plasmonic photocatalyst Ag@AgCl nanostructures. SEM, XRD, X‐ray photoelectron spectroscopy, and UV/Vis diffuse reflectance spectroscopy were used to characterize the obtained product. The photocatalytic activity of the obtained product was evaluated by the photodegradation of methyl orange pollutant under visible‐light irradiation, and it was found that Ag@AgCl microrods exhibited high visible‐light photocatalytic activity and good stability.
Natural reversal of left‐right gut/gonad asymmetry in C. elegans males is independent of embryonic chirality
Authors: Callander Davon C. , Alcorn Melissa R. , Birsoy Bilge , Rothman Joel H. 
Published: March 2014

SummaryAnatomical left‐right (L/R) asymmetry in C. elegans is established in the four‐cell embryo as a result of anteroposterior skewing of transverse mitotic spindles with a defined handedness. This event creates a chiral embryo and ultimately an adult body plan with fixed L/R positioning of internal organs and components of the nervous system. While this “dextral” configuration is invariant in hermaphrodites, it can be reversed by physical manipulation of the early embryo or by mutations that interfere with mitotic spindle orientation, which leads to viable, mirror‐reversed (sinistral) animals. During normal development of the C. elegans male, the gonad develops on the right of the midline, with the gut bilaterally apposed on the left. However, we found that in males of the laboratory N2 strain and Hawaiian (“Hw”) wild isolate, the gut/gonad asymmetry is frequently reversed in a temperature‐dependent manner, independent of normal embryonic chirality. We also observed sporadic errors in gonad migration occurring naturally during early larval stages of these and other wild strains; however, the incidence of such errors does not correlate with the frequency of L/R gut/gonad reversals in these strains. Analysis of N2/Hw hybrids and recombinant inbred advanced intercross lines (RIAILs) indicate that the L/R organ reversals are likely to result from recessively acting variations in multiple genes. Thus, unlike the highly reproducible L/R asymmetries of most structures in hermaphrodites, the L/R asymmetry of the male C. elegans body plan is less rigidly determined and subject to natural variation that is influenced by a multiplicity of genes. genesis 52:581–587, 2014. © 2014 Wiley Periodicals, Inc.
Symmetry breakage in the frog Xenopus: Role of Rab11 and the ventral‐right blastomere
Authors: Tingler Melanie , Ott Tim , Tözser Janos , Kurz Sabrina , Getwan Maike , Tisler Matthias , Schweickert Axel , Blum Martin 
Published: March 2014

SummaryVertebrates display asymmetric arrangements of inner organs such as heart and stomach. The Nodal signaling cascade in the left lateral plate mesoderm in all cases directs asymmetric morphogenesis and placement during organogenesis. Mechanisms that lead up to left‐asymmetric Nodal induction seem to differ between the vertebrates. Cilia produce a leftward extracellular fluid flow in zebrafish, medaka, mouse, rabbit, and Xenopus embryos during neurulation. In Xenopus, earlier asymmetric cues were described. Some, such as Rab11, apparently act in the zygote. Others were efficiently manipulated in ventral‐right cells at the four‐cell stage, a lineage presumably independent of the ciliated gastrocoel roof plate (GRP) during neurulation. Here, we show that one‐ and four‐cell manipulations of Rab11 showed equal low efficiencies of left–right disturbances. We also reevaluated the lineage of the GRP. By tracing back future ciliated cells from the gastrula to the four‐cell stage, we show that ventral cells contribute to ciliated sensory cells at the border of the GRP. Knockdown of the Nodal inhibitor Coco in the ventral right lineage resulted in embryos with ectopic right‐sided Nodal and Pitx2c expression. Together, these experiments support a cilia‐based mechanism of symmetry breakage in the frog Xenopus. genesis 52:588–599, 2014. © 2014 Wiley Periodicals, Inc.
Emotion regulation difficulties in anorexia nervosa before and after inpatient weight restoration
Authors: Haynos Ann F. , Roberto Christina A. , Martinez Margaret A. , Attia Evelyn , Fruzzetti Alan E. 
Published: March 2014

ABSTRACTObjectiveThis study examined: (1) changes in emotion regulation difficulties in underweight inpatients with anorexia nervosa (AN) following weight restoration, (2) differences in emotion regulation between AN subtypes at acute and weight‐restored stages of illness.MethodRepeated measure analyses of variance examined changes in scores on the Difficulties in Emotion Regulation Scale (DERS; Gratz and Roemer, J Psychopathol Behav Assess, 26, 41–54, 2004) and other clinical variables in a group of inpatients with AN from hospital admission (N = 65) to weight restoration (N = 51). Correlations between BMI and DERS scores at both time points were examined. Emotion regulation difficulties were compared between individuals with AN, restricting type (AN‐R) and AN, binge/purge type (AN‐BP) at both time points using multivariate analysis of covariance.ResultsAll clinical variables, except for the DERS, significantly improved with weight restoration (p < .001). There were no associations between BMI and DERS prior to or after weight restoration and AN subtypes did not significantly differ in emotion regulation difficulties.DiscussionUnlike other clinical variables, emotion regulation difficulties in AN did not improve with weight restoration. In addition, both subtypes of AN appear to have similar difficulties with emotion regulation. The treatment of AN might be enhanced by focusing on improving emotion regulation abilities. © 2014 Wiley Periodicals, Inc. Int J Eat Disord 2014; 47:888–891
Increased genetic divergence between two closely related fir species in areas of range overlap
Authors: Wang Jing , Abbott Richard J. , Ingvarsson Pär K. , Liu Jianquan 
Published: March 2014

AbstractBecause of introgressive hybridization, closely related species can be more similar to each other in areas of range overlap (parapatry or sympatry) than in areas where they are geographically isolated from each other (allopatry). Here, we report the reverse situation based on nuclear genetic divergence between two fir species, Abies chensiensis and Abies fargesii, in China, at sites where they are parapatric relative to where they are allopatric. We examined genetic divergence across 126 amplified fragment length polymorphism (AFLP) markers in a set of 172 individuals sampled from both allopatric and parapatric populations of the two species. Our analyses demonstrated that AFLP divergence was much greater between the species when comparisons were made between parapatric populations than between allopatric populations. We suggest that selection in parapatry may have largely contributed to this increased divergence.