bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diffusion‐weighted imaging and diagnosis of transient ischemic attack
Authors: Brazzelli Miriam , Chappell Francesca M. , Miranda Hector , Shuler Kirsten , Dennis Martin , Sandercock Peter A. G. , Muir Keith , Wardlaw Joanna M. 
Published: October 2013

ObjectiveMagnetic resonance (MR) diffusion‐weighted imaging (DWI) is sensitive to small acute ischemic lesions and might help diagnose transient ischemic attack (TIA). Reclassification of patients with TIA and a DWI lesion as “stroke” is under consideration. We assessed DWI positivity in TIA and implications for reclassification as stroke.MethodsWe searched multiple sources, without language restriction, from January 1995 to July 2012. We used PRISMA guidelines, and included studies that provided data on patients presenting with suspected TIA who underwent MR DWI and reported the proportion with an acute DWI lesion. We performed univariate random effects meta‐analysis to determine DWI positive rates and influencing factors.ResultsWe included 47 papers and 9,078 patients (range = 18–1,693). Diagnosis was by a stroke specialist in 26 of 47 studies (55%); all studies excluded TIA mimics. The pooled proportion of TIA patients with an acute DWI lesion was 34.3% (95% confidence interval [CI] = 30.5–38.4, range = 9–67%; I2 = 89.3%). Larger studies (n > 200) had lower DWI‐positive rates (29%; 95% CI = 23.2–34.6) than smaller (n < 50) studies (40.1%; 95% CI = 33.5–46.6%; p = 0.035), but no other testable factors, including clinician speciality and time to scanning, reduced or explained the 7‐fold DWI‐positive variation.InterpretationThe commonest DWI finding in patients with definite TIA is a negative scan. Available data do not explain why ⅔ of patients with definite specialist‐confirmed TIA have negative DWI findings. Until these factors are better understood, reclassifying DWI‐positive TIAs as strokes is likely to increase variance in estimates of global stroke and TIA burden of disease. ANN NEUROL 2014;75:67–76
Catalytic Functionalization of C(sp2)H and C(sp3)H Bonds by Using Bidentate Directing Groups
Authors: Rouquet Guy , Chatani Naoto 
Published: October 2013

AbstractCH bonds are ubiquitous in organic compounds. It would, therefore, appear that direct functionalization of substrates by activation of CH bonds would eliminate the multiple steps and limitations associated with the preparation of functionalized starting materials. Regioselectivity is an important issue because organic molecules can contain a wide variety of CH bonds. The use of a directing group can largely overcome the issue of regiocontrol by allowing the catalyst to come into proximity with the targeted CH bonds. A wide variety of functional groups have been evaluated for use as directing groups in the transformation of CH bonds. In 2005, Daugulis reported the arylation of unactivated C(sp3)H bonds by using 8‐aminoquinoline and picolinamide as bidentate directing groups, with Pd(OAc)2 as the catalyst. Encouraged by these promising results, a number of transformations of CH bonds have since been developed by using systems based on bidentate directing groups. In this Review, recent advances in this area are discussed.
Cationic, Two‐Coordinate Gold π Complexes
Authors: Brooner Rachel E. M. , Widenhoefer Ross A. 
Published: October 2013

AbstractCationic, two‐coordinate gold π complexes that contain a phosphine or N‐heterocyclic supporting ligand have attracted considerable attention recently owing to the potential relevance of these species as intermediates in the gold‐catalyzed functionalization of CC multiple bonds. Although neutral two‐coordinate gold π complexes have been known for over 40 years, examples of the cationic two‐coordinate gold(I) π complexes germane to catalysis remained undocumented prior to 2006. This situation has changed dramatically in recent years and well‐defined examples of two‐coordinate, cationic gold π complexes containing alkene, alkyne, diene, allene, and enol ether ligands have been documented. This Minireview highlights this recent work with a focus on the structure, bonding, and ligand exchange behavior of these complexes.
Transition‐Metal‐Catalyzed Laboratory‐Scale Carbon–Carbon Bond‐Forming Reactions of Ethylene
Authors: Saini Vaneet , Stokes Benjamin J. , Sigman Matthew S. 
Published: October 2013

AbstractEthylene, the simplest alkene, is the most abundantly synthesized organic molecule by volume. It is readily incorporated into transition‐metal‐catalyzed carbon–carbon bond‐forming reactions through migratory insertions into alkylmetal intermediates. Because of its D2h symmetry, only one insertion outcome is possible. This limits byproduct formation and greatly simplifies analysis. As described within this Minireview, many carbon–carbon bond‐forming reactions incorporate a molecule (or more) of ethylene at ambient pressure and temperature. In many cases, a useful substituted alkene is incorporated into the product.
A Theoretical Study on the Structure, Intramolecular Interactions, and Detonation Performance of Hydrazinium Dinitramide
Authors: Zhang Xueli , Liu Yan , Wang Fang , Gong Xuedong 
Published: October 2013

AbstractThe structures of hydrazinium dinitramide (HDN) in the gas phase and in aqueous solution have been studied at different levels of theory by using quantum chemistry. The intramolecular hydrogen‐bond interactions in HDN were studied by employing the quantum theory of atoms in molecules (QTAIM), as well as those in ammonium dinitramide (ADN), hydrazinium nitroformate (HNF), and ammonium nitroformate (ANF) for comparison. The results showed that HDN possessed the strongest hydrogen bonds, with the largest hydrogen‐bond energy (−47.95 kJ mol−1) and the largest total hydrogen‐bond energy (−60.29 kJ mol−1). In addition, the charge transfer between the cation and the anion, the binding energy, the energy difference between the frontier orbitals, and the second‐order perturbation energy of HDN were all the largest among the investigated compounds. These strongest intramolecular interactions accounted for the highest decomposition temperature of HDN among all four compounds. The IR spectra in the gas phase and in aqueous solution were very different and showed the significant influence of the solvent. The UV spectrum showed the strongest absorption at about 253 nm. An orbital‐interaction diagram demonstrated that the transition of electrons mainly happened inside the anion of HDN. The detonation velocity (D=8.34 km s−1) and detonation pressure (P=30.18 GPa) of HDN were both higher than those of ADN (D=7.55 km s−1 and P=24.83 GPa). The composite explosive HDN/CL‐20 with the weight ratio wCL−20/wHDN=0.388:0.612 showed the best performance (D=9.36 km s−1, P=39.82 GPa), which was close to that of CL‐20 (D=9.73 km s−1, P=45.19 GPa) and slightly better than that of the composite explosive ADN/CL‐20 (wCL−20/wADN=0.298:0.702, D=9.34 km s−1, P=39.63 GPa).
Biocatalytic Performance of pH‐Sensitive Magnetic Nanoparticles Derived from Layer‐by‐Layer Ionic Self‐Assembly of Chitosan with Glucoamylase
Authors: Wang Jian‐zhi , Zhao Guang‐hui , Li Yan‐feng , Peng Xiao‐meng , Li Yan‐tao 
Published: October 2013

AbstractBased on the characteristics of polycations of chitosan and glucoamylase, which are oppositely charged, they were successfully alternatingly deposited onto the surface of aldehyde‐modified Fe3O4 nanoparticles by using a layer‐by‐layer ion exchange method to form magnetic carriers to construct multilayer films (designated as Fe3O4@(CS/GA)n). The (CS/GA)n film systems were endowed with the pH‐dependent properties of chitosan as well as the catalytic activity of glucoamylase. The changes in weight loss and surface chemistry, morphology, and magnetic sensitivity were monitored and verified by UV/Vis spectroscopy, zeta potential, TEM, and a vibrating sample magnetometer. Subsequently, the influence of the number of bilayers, storage stability, pH, temperature, and reusability of Fe3O4@(CS/GA)5 biocatalysts on catalytic activity were investigated. The results from characterization and determination remarkably indicate that Fe3O4@(CS/GA)5 presents excellent catalytic activity, storage stability, pH stability, and reusability in comparison with free enzyme. Fe3O4@(CS/GA)5 retained >60 % of its initial activity at 65 °C over 6 h; the optimum temperature and pH also increased to the ranges of 45–65 °C and 2.5–3.5, respectively, and only 27 % activity was lost after 10 cycles. This new strategy simplifies the reaction protocol and improves encapsulation efficiency and catalytic activity for new potential applications in biotechnology.
Rh‐Catalyzed AldehydeAldehyde Cross‐Aldol Reaction under Base‐Free Conditions: In Situ Aldehyde‐Derived Enolate Formation through Orthogonal Activation
Authors: Lin Luqing , Yamamoto Kumiko , Matsunaga Shigeki , Kanai Motomu 
Published: October 2013

AbstractThe chemoselective generation of aldehyde‐derived enolates to realize an aldehydealdehyde cross‐aldol reaction is described. A combined Rh/dippf system efficiently promoted the isomerization/aldol sequence by using primary allylic, homoallylic, and bishomoallylic alcohols; secondary allylic and homoallylic alcohols; and trialkoxyboranes that were derived from primary allylic and homoallylic alcohols. The reaction proceeded at ambient temperature under base‐free conditions, thus giving cross‐aldol products with high chemoselectivity. Mechanistic studies, as well as its application to double‐aldol processes under protecting‐group‐free conditions, are also described.
Thermodynamic Phase Transition Through Crystal‐to‐Crystal Process of Photochromic 1,2‐Bis(5‐phenyl‐2‐propyl‐3‐thienyl)perfluorocyclopentene
Authors: Kitagawa Daichi , Kobatake Seiya 
Published: October 2013

AbstractA photochromic diarylethene, 1,2‐bis(5‐phenyl‐2‐propyl‐3‐thienyl)perfluorocyclopentene (1a), was found to have two polymorphic crystal forms, α‐ and β‐crystals. From X‐ray crystallographic analysis, the space groups of α‐ and β‐crystals were determined to be P21/c and C2/c, respectively. The difference between two crystal forms is ascribed to the orientation of two of four molecules in the unit cell. The thermodynamic phase transition from α‐ to β‐forms occurred via a crystal‐to‐crystal process, as confirmed by differential scanning calorimetry measurements, optical microscopic observations in the reflection mode and under crossed Nicols, and powder X‐ray diffraction measurements. The movement of the molecules in the crystal was evaluated by analyzing the change of face indices before and after the phase transition.
Phase‐Transfer‐Catalyzed Asymmetric Synthesis of Axially Chiral Anilides
Authors: Liu Kun , Wu Xiangfei , Kan S. B. Jennifer , Shirakawa Seiji , Maruoka Keiji 
Published: October 2013

AbstractCatalytic asymmetric synthesis of axially chiral o‐iodoanilides and o‐tert‐butylanilides as useful chiral building blocks was achieved by means of binaphthyl‐modified chiral quaternary ammonium‐salt‐catalyzed N‐alkylations under phase‐transfer conditions. The synthetic utility of axially chiral products was demonstrated in various transformations. For example, axially chiral N‐allyl‐o‐iodoanilide was transformed to 3‐methylindoline by means of radical cyclization with high chirality transfer from axial chirality to C‐centered chirality. Furthermore, stereochemical information on axial chirality in o‐tert‐butylanilides could be used as a template to control the stereochemistry of subsequent transformations. The transition‐state structure of the present phase‐transfer reaction was discussed on the basis of the X‐ray crystal structure of ammonium anilide, which was prepared from binaphthyl‐modified chiral ammonium bromide and o‐iodoanilide. The chiral tetraalkylammonium bromide as a phase‐transfer catalyst recognized the steric difference between the ortho substituents on anilide to obtain high enantioselectivity. The size and structural effects of the ortho substituents on anilide were investigated, and a wide variety of axially chiral anilides that possess various functional groups could be synthesized with high enantioselectivities. This method is the only general way to access a variety of axially chiral anilides in a highly enantioselective fashion reported to date.
Mechanistic study of stress corrosion cracking of carbon steel in ethanol
Authors: Torkkeli J. , Hirsi V. , Saukkonen T. , Hänninen H. 
Published: October 2013

AbstractMechanistic study of stress corrosion cracking of carbon steel in fuel‐grade ethanol was made using slow strain rate testing and constant tensile load testing at yield strength stress level of the steels. Characterization of the fracture surface was made using SEM and SEM–EDS. Selective dissolution of ferrite from pearlite phase was observed. Crack initiation took place preferably from pearlite phase. Corroded zones consisting of crystallographic pits were found from fracture surfaces.
Comparison study on anticorrosion performances of the epoxy coatings with two different nano‐polyanilines for Q235 steel
Authors: Hou W. P. , Liu Y. , Ge Z. Y. , Zhao W. Y. 
Published: October 2013

AbstractSulfuric acid doped nano‐polyaniline was prepared by direct mixed oxidation in two different systems. A novel approach for preparing polyaniline (PANI) in FeCl2/H2O2 system was developed. The PANI possessed an excellent dispensability. Corrosion protection of epoxy coatings containing two kinds of polyaniline (PANI) on Q235 steel was studied by electrochemical impendance spectroscopy (EIS) technique and Tafel polarization test in 3.5 wt% sodium chloride (NaCl) aqueous solution. The results indicated that the epoxy coating containing PANI obtained in FeCl2/H2O2 system had the best performance of the corrosion protection among three systems under investigation. The possible protective mechanism of PANI was discussed.
Significantly changed intergranular corrosion and exfoliation corrosion behavior of the ultra‐fine grained Al–5 mass% Cu alloy fabricated by ECAP
Authors: Song D. , Ma A. B. , Jiang J. H. , Lin P. H. , Lu F. M. , Zhang L. Y. 
Published: October 2013

AbstractSignificantly changed intergranular corrosion (IGC) and exfoliation corrosion (EFC) behaviors of the equal‐channel‐angular‐pressed (ECAPed) Al–Cu alloy were discovered through immersion test, electrochemical measurements, and microstructure observation. The ECAPed alloys with ultra‐fine grained (UFG) α(Al) matrix and extremely refined θ‐phase particles displayed obvious decreased IGC sensitivity, but deteriorated susceptibility to EFC. The decreased IGC sensitivity of ECAPed alloys presented decreased IGC propagation depths in immersion test in NaCl + H2O2 solutions and increased polarization resistance in electrochemical impedance spectrum test in MIL‐H‐600 solution. The reason for the decreased IGC sensitivity was the breakage of the net structure of θ phase during ECAP process, which destroys the continuity of IGC propagation channel. The deteriorated susceptibility to EFC of ECAPed alloys in EXCO solution presented gradual evolution from serious IGC attack into obvious lamellar EFC, and finally complete dissolution of surface grains. Meanwhile, the EFC propagation depths were sharply decreased with the increasing ECAP passes. This phenomenon was caused by the aspects ratio evolution of deformed grains and the gradually decreased IGC sensitivity of the ECAPed alloys.
Photophysics and morphology of a polyfluorene donor–acceptor triblock copolymer for solar cells
Authors: Yan Chao , Cadby Ashley J. , Parnell Andrew J. , Tang Weihua , Skoda Maximilian W. A. , Mohamad David , King Simon P. , Reynolds Luke X. , Haque Saif A. , Wang Tao , Parnell Steven R. , Holmes Andrew B. , Jones Richard A. L. , Jones David J. 
Published: October 2013

ABSTRACTWe present a study of the optical, structural and device properties of a polyfluorene (PFM)‐based (PFM‐F8BT‐PFM) donor–acceptor triblock copolymer for use in an organic solar cell. Neutron reflectivity is employed to probe the vertical composition profile before and after thermal annealing while the crystallinity was examined using grazing incidence wide‐angle X‐ray. The absorption spectra and photoluminescence emission for the triblock and analogous blend of PFM with F8BT reveal a greater degree of intermixing in the triblock. However, the triblock copolymer exhibits exciplex emission, which necessitates a geminate polar pair; long‐lived exciplex states are detrimental in organic photovoltaic devices. The triplet yield in the triblock and the blend is estimated using photoinduced absorption, with the triblock copolymer generating a triplet population 20 times that of the blend. This is far from ideal as triplets are wasted states in organic photovoltaic devices and they can also act as scavengers of polarons reducing the efficiency even more. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys.2013,51, 1705–1718
Rapid dislocation‐density mapping of as‐cut crystalline silicon wafers
Authors: Needleman David Berney , Choi1 Hyunjoo , Powell1 Douglas M. , Buonassisi Tonio 
Published: October 2013

AbstractRapid quantification of structural defects, especially dislocations, is desired for characterization of semiconductor materials. Herein, we outline and validate a low‐cost approach for dislocation‐density quantification in silicon, involving a high‐resolution commercial dark‐field imaging device, a flatbed scanner. This method requires minimal surface preparation and can be performed on as‐cut 15.6 × 15.6 cm2wafers in less than 5 minutes. The method has been tested at a spatial resolution down to 250 µm. At 1 mm resolution, the average root mean square of the normalized error was 0.39.magnified imageFlatbed scanner image of a defect‐etched 15.6 × 15.6 cm2silicon wafer (left) and the corresponding dislocation‐density map obtained using our technique (right).(© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sonographic prediction of vaginal delivery in prolonged labor: a two‐center study
Authors: Eggebø T. M. , Hassan W. A. , Salvesen K. Å. , Lindtjørn E. , Lees C. C. 
Published: October 2013

ABSTRACTObjectiveTo investigate whether head–perineum distance (HPD) measured by transperineal ultrasound is predictive of vaginal delivery and time remaining in labor in nulliparous women with prolonged first stage of labor and to compare the predictive value with that of angle of progression (AoP).MethodsThis was a prospective observational study at Stavanger University Hospital, Norway and Addenbrooke's Hospital, Cambridge, UK from January 2012 to April 2013, of nulliparous women with singleton pregnancies with cephalic presentation at term with prolonged first stage of labor. We used transperineal ultrasound to measure HPD (shortest distance between the outer bony limit of the fetal skull and the perineum) and AoP (angle between a line through the long axis of the symphysis and the tangent to the fetal head) and transabdominal ultrasound to classify fetal head position. The main outcomes were vaginal delivery and time remaining in labor.ResultsOf 150 women enrolled, 39 underwent delivery by Cesarean section. The area under the receiver–operating characteristics curve for the prediction of vaginal delivery was 81% (95% CI, 73–89%) using HPD as the test variable and 72% (95% CI, 63–82%) using AoP. HPD was ≤ 40 mm in 84 (56%) women, of whom 77 (92%; 95% CI, 84–96%) delivered vaginally. HPD was > 40 mm in the other 66 (44%) women, of whom 34 (52%; 95% CI, 40–63%) delivered vaginally. AoP was ≥ 110° in 84 of the 145 (58%) in whom this was available and, of these, 74 (88%; 95% CI, 79–93%) delivered vaginally. AoP was < 110° in the other 61 (42%) women, of whom 35 (57%; 95% CI, 45–69%) delivered vaginally. Multivariable logistic regression analysis showed that HPD ≤ 40 mm (odds ratio (OR), 4.92; 95% CI, 1.54–15.80), AoP ≥ 110° (OR, 3.11; 95% CI, 1.01–9.56), non‐occiput posterior position (OR, 3.36; 95% CI, 1.24–9.12) and spontaneous onset of labor (OR, 4.44; 95% CI, 1.42–13.89) were independent predictors for vaginal delivery. Both ultrasound methods were predictive for the time remaining in labor.ConclusionTransperineal ultrasound measurement of HPD and AoP provide important information about the likelihood of vaginal delivery and the time remaining in labor in nulliparous women with prolonged labor. Copyright © 2013 ISUOG. Published by John Wiley & Sons Ltd.
Investigating Factors Affecting Water‐In‐Diesel Fuel Nanoemulsions
Authors: Noor El‐Din Mahmoud R. , El‐Hamouly Sabrnal H. , Mohamed Hamed M. , Mishrif Marwa R. , Ragab Ahmad M. 
Published: September 2013

AbstractIn this work, water‐in‐diesel fuel nanoemulsions were prepared with mixed nonionic surfactants. Several mixtures of sorbitan monooleate and polyoxyethylene (20) sorbitan monooleate, with different Hydrophilic–Lipophilic Balance (HLB) values (9.6, 9.8, 10, 10.2 and 10.4) were prepared to achieve the optimal HLB value. Three mixed surfactant concentrations were prepared at 6, 8 and 10 wt% to identify the optimum concentration. Five emulsions with different water contents: 5, 6, 7, 8 and 9 % (wt/wt) were prepared using a high energy method under the optimum conditions (HLB = 10 and mixed surfactant concentration = 10 %). The effect of the HLB value, mixed surfactant concentration and water content on the droplet size has been studied. The interfacial tension and thermodynamic properties of the individual and the blended emulsifiers were investigated. Droplet size of the prepared nanoemulsions was determined by dynamic light scattering and the nanoemulsion stability was assessed by measuring the variation of the droplet size as a function of time. From the results obtained, it was found that the mean droplet size was formed between 49.5 and 190 nm depending on the HLB value, surfactant concentration and water content of the blended emulsifiers.
Production of Canolol from Canola Meal Phenolics via Hydrolysis and Microwave‐Induced Decarboxylation
Authors: Khattab Rabie Y. , Eskin Michael N. A. , Thiyam‐Hollander Usha 
Published: September 2013

AbstractA potent antioxidant, anti‐inflammatory and anti‐mutagenic agent; 4‐vinyl‐2,6‐dimethoxyphenol (canolol) was obtained from canola meal in a significant yield via alkaline (NaOH)/enzymatic (ferulic acid esterase) hydrolysis followed by microwave‐assisted decarboxylation. The hydrolysis was carried out either through using canola meal directly as a substrate or by using the 70 % aqueous methanolic extract filtrates. The hydrolyzed extracts underwent RP‐HPLC analysis which showed that 81.0 and 94.8 % of the total phenolics were hydrolyzed to sinapic acid after the alkaline hydrolysis of the meal and the methanolic extracts, respectively. The enzymatic hydrolysis showed lower conversion rates (49.5 and 58.3 %). The hydrolyzed extracts were consequently decarboxylated using 8‐diazabicyclo[5.4.0]undec‐7‐ene under microwave irradiation at different conditions. The HPLC profiling of decarboxylated extracts showed that using microwave at 300 W of microwave power for 12 min brought the highest sinapic acid conversion to canolol (58.3 %) yielding 4.2 mg canolol from each gram of canola meal suggesting that the process could be commercially economical.