bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reactions of nitrogen nucleophiles with enantiopure cyclohexenyl electrophiles: a stereo‐ and regio‐ selective study
Authors: Boyd Derek R. , Sharma Narain D. , Belhocine Tayeb , Malone John F. , McGregor Stuart T. , Atchison Jordan , McIntyre Peter A. B. , Stevenson Paul J. 
Published: August 2013

The reactions of enantiopure cyclohexene epoxides and trans‐1,2‐bromoacetates, derived from the corresponding substituted benzene cis‐dihydrodiol metabolites, with nitrogen nucleophiles, were examined and possible mechanisms proposed. An initial objective was the synthesis of new 1,2‐aminoalcohol enantiomers as potential chiral ligands and synthetic scaffolds for library generation. These apparently simple substitution reactions proved to be more complex than initially anticipated and were found to involve a combination of different reaction mechanisms.Allylic trans‐1,2‐azidohydrins were prepared by Lewis acid‐catalysed ring‐opening of cyclic vinyl epoxides with sodium azide via an SN2 mechanism. On heating, these trans‐1,2‐azidohydrins isomerized to the corresponding trans‐1,4‐azidohydrins via a suprafacial allyl azide [3,3]‐sigmatropic rearrangement mechanism. Conversion of a 1,2‐azidohydrin to a 1,2‐azidoacetate moved the equilibrium position in favour of the 1,4‐substitution product. Allylic trans‐1,2‐bromoacetates reacted with sodium azide at room temperature to give C‐2 and C‐4 substituted products. A clean inversion of configuration at C‐2 was found, as expected, from a concerted SN2‐pathway. However, substitution at C‐4 was not stereoselective and resulted in mixtures of 1,4‐cis and 1,4‐trans products. This observation can be rationalized in terms of competitive SN2 and SN2′ reactions allied to a [3,3]‐sigmatropic rearrangement. cis‐1,2‐Azidohydrins and cis‐1,2‐azidoacetates were much more prone to rearrange than the corresponding trans‐isomers.Reaction of the softer tosamide nucleophile with trans‐1,2‐bromoacetates resulted, predominantly, in C‐4 substitution via a syn‐SN2′ mechanism. One application of the reaction of secondary amines with allylic cyclohexene epoxides, to give trans‐1,2‐aminoalcohols, is in the synthesis of the anticholinergic drug vesamicol, via an SN2 mechanism. Copyright © 2013 John Wiley & Sons, Ltd.
Surface Functionalization of COC Microfluidic Materials by Plasma and Click Chemistry Processes
Authors: Ladner Yoann , d'Orlyé Fanny , Perréard Camille , Da Silva Bradley , Guyon Cédric , Tatoulian Michael , Griveau Sophie , Bedioui Fethi , Varenne Anne 
Published: August 2013

AbstractA robust method for COC surfaces functionalization was developed for the first time by plasma polymerization. 1‐bromopropane in the vapor phase allowed the formation of a brominated deposit on COC surfaces, which stability, homogeneity and chemical nature were evaluated for different experimental conditions. The analysis of vapor phase was achieved by mass spectrometry to control brominated precursor fragmentation. Following nucleophilic exchange in the presence of NaN3 to convert the brominated surface to azide‐bearing surface, these modified COC were further functionalized with a fluorescent alkyne, via the copper‐catalyzed azide–alkyne cycloaddition reaction, i.e. “click” reaction. Surface modifications were characterized by water contact angle measurement, ellipsometry, electrochemical microscopy, XPS, IR and fluorescence microscopy. This new process was proved to be efficient and stable in time up to 7 days.
Nanofunctional gallium oxide (Ga2O3) nanowires/nanostructures and their applications in nanodevices
Authors: Kumar Sudheer , Singh R. 
Published: August 2013

Abstractmagnified imageA brief review on beta gallium oxide (β‐Ga2O3) nanowires (NWs) and nanostructures (NS) is presented in this article. β‐Ga2O3 is a wide‐bandgap (Eg ∼ 4.9 eV) semiconductor and can be doped with n‐ and p‐type dopants, which can lead to applications in many functional devices. Here, we will first discuss briefly the properties of β‐Ga2O3 in bulk form. Then we will describe the growth of β‐Ga2O3 NWs/NS using various techniques including thermal CVD, MOCVD and laser ablation. The present status of research in the area of nanowire growth will be highlighted in this section. Then we will describe the luminescence properties of β‐Ga2O3 NWs such as photoluminescence (PL) and cathodoluminescence (CL). The origin of various peaks in the PL and CL spectra of β‐Ga2O3 NWs/ NS will be presented, with reference to various experimental studies carried out recently. In the final section, we will describe various applications of β‐Ga2O3 NWs in nanodevices such as field effect transistors (FET), gas sensors and deep‐UV photodetectors. Finally, we will give a conclusion and future perspective of the research in the area of this important semiconducting oxide. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Conceptualizing the Science Curriculum: 40 Years of Developing Assessment Frameworks in Three Large‐Scale Assessments
Authors: KIND PER MORTEN 
Published: August 2013

ABSTRACTThe paper analyzes conceptualizations in the science frameworks in three large‐scale assessments, Trends in Mathematics and Science Study (TIMSS), Programme for International Student Assessment (PISA), and National Assessment of Educational Progress (NAEP). The assessments have a shared history, but have developed different conceptualizations. The paper asks how and why the frameworks are different and seeks answers by studying their development. The methodology is document analysis by, first, tracing developments within each assessment, next, comparing developments and conceptualization across the assessments, and, last, relating the frameworks to trends of developments in educational theory. The outcome of the analysis provides a complex picture with the assessments following their own lines of development but with influence from trends in assessment and educational theory. Five main conceptualizations are found to have existed over time, with different definition of scientific behavior and explanations to the relationship between knowledge and behavior. The frameworks have moved toward more elaborated explanations of the science domain, providing assessors with better support for operationalizing learning objectives. Currently, the assessments are faced with a challenge of adapting to the “practice turn” in science studies and learning science and thereby accounting for scientific behavior as a community practice. The paper concludes with suggestions for how frameworks may be improved to achieve this aim. © 2013 Wiley Periodicals, Inc. Sci Ed 97:671–694, 2013
Investigation of Chromium Complexes with a Series of Tripodal Ligands
Authors: Schäfer Sabrina , Becker Jonathan , Beitat Alexander , Würtele Christian 
Published: August 2013

AbstractA series of chromium(II) complexes containing the tripodal ligands tmpa, Me2uns‐penp, Me4apme and Me6tren were prepared and investigated with regard to their reactivity towards dioxygen. It was possible to structurally characterize the complexes [Cr(Me2uns‐penp)Cl]2(BPh4)2, [Cr(Me6tren)Cl]Cl, [Cr(Me4apme)Cl]BPh4 and [Cr(Me4ampe)Cl3]. The complexes show reactions with dioxygen, but it was not possible to characterize intermediates of these reactions. The oxidation behavior of the complexes towards organic substrates like toluene was investigated and oxidation of toluene to benzaldehyde was observed.
2, 6‐Bis((E)‐((5‐benzoyl‐2‐thioxo‐4‐phenylpyrimidin‐1(2H)‐yl)imino)methyl)‐4‐(methyl)phenol and its Metal(II) Complexes: Synthesis, Spectroscopy, Biological Activity, and Photoluminescence Features
Authors: Gulcan Mehmet , Zengin Hüseyin , Çelebi Metin , Sönmez Mehmet , Berber İsmet 
Published: August 2013

AbstractThe preparation, characterization, magnetic measurements, antimicrobial activity, and photoluminescence properties of a number of metal complexes with a Schiff base ligand derived from 2, 6‐diformyl‐4‐methylphenol and 1‐amino‐5‐benzoyl‐4‐phenyl‐1H‐pyrimidine‐2‐thione are reported herein. UV/Vis spectra and magnetic measurements infer square planar stereochemistry for PdII and PtII complexes, and octahedral arrangement for the other metal complexes. The compounds results in intense emission (where λmax = 402 nm) upon irradiation by UV light. The photoluminescence quantum yields and long excited‐state lifetimes of the ligand and its complexes were calculated as 42 % and 3.94 ns, respectively. The photoluminescence intensities and quantum yields of metal complexes changed upon complexation with various metal ions. The ligand and its complexes are of interest as organic emitting materials for electroluminescent devices. The complexes were additionally evaluated for in vitro the antimicrobial activity against bacterial and fungal strains. While CuII, CoII, and PtII complexes have good antifungal efficiency against yeast (MICs, 80 μg·mL–1), only the complex [Cu(L)(AcO)]·4H2O had effective and selective antimicrobial activity against all tested microorganisms with MIC values in the range of 40–80 μg·mL–1, except for E. coli ATCC 4230. This study suggests that the complex [Cu(L)(AcO)]·4H2O may be a new potential antimicrobial substance towards bacteria and fungi.
Hydrothermal Synthesis of 3D Copper(II)‐Organic Frameworks: In situ Formation of 3‐Hydroxopyrazine‐2‐carboxylate from 3‐Aminopyrazine‐2‐carboxylic Acid
Authors: Dehghanpour Saeed , Jahani Khadijeh , Mahmoudi Ali , Babakhodaverdi Mogtaba , Tabatabaei Robabehsadat , Notash Behrouz 
Published: August 2013

AbstractAbstract. The metal organic framework, [Cu5(C5H2N2O3)4(H2O)4(NO3)2·10H2O]n (1), was synthesized by a hydrothermal reaction via copper nitrate and in situ generated 3‐hydroxopyrazine‐2‐carboxylate from 3‐aminopyrazine‐2‐carboxylic acid. Compound 1 was characterized by elemental analysis, infrared spectroscopy, TG analysis, and single‐crystal X‐ray diffraction. It has a 3D structure constructed from Cu2+ cations, bridging NO3– anions, and 3‐hydroxopyrazine‐2‐carboxylate units. The NO3– anions act as μ2‐bridging ligand and the 3‐hydroxopyrazine‐2‐carboxylate units coordinate pentadentately through the two oxygen atoms of their carboxylate group, the oxygen atom of the hydroxyl group and two nitrogen atoms. The ligands link the CuII ions to form trinuclear units. These are further connected to form a novel 3D MOF, with a novel 4‐nodal 3,3,3,4‐connected net topology of an unprecedented point (Schläfli) symbol (6.7.9)(64.8.9)(7.102)(72.10).
Brief report: Testing measurement invariance and differences in self‐concept between adolescents with and without physical illness or developmental disability
Authors: Ferro Mark A. , Boyle Michael H. 
Published: August 2013

ABSTRACTThe aim of this study was to test for measurement invariance and examine differences in global self‐concept between adolescents with and without physical illness or developmental disability. The sample consisted of adolescents 10–19 years who participated in the Canadian National Longitudinal Survey of Children and Youth (N = 8491). Multiple group confirmatory factor analysis was used to test for measurement invariance. Twenty‐three percent (n = 1966) of participants had a physical illness or developmental disability. Support was found for strict measurement invariance between groups suggesting adolescents in both groups perceived items similarly, indicating that comparisons between adolescents with and without physical illness or developmental disability are meaningful. Controlling for several sociodemographic characteristics, evidence suggested that self‐concept is lower in adolescents with physical illness or developmental disability, β = −0.24, p = 0.0005, compared to their healthy peers. Future work should attempt to understand the processes leading to compromised self‐concept in adolescents with physical illness or developmental disability.
‘Listen to them’: Adolescents' views on helping young people who self‐injure
Authors: Berger Emily , Hasking Penelope , Martin Graham 
Published: August 2013

ABSTRACTNon‐suicidal self‐injury (NSSI) among adolescents is a significant problem, yet the majority do not seek professional help. Parents and teachers are arguably most in contact with young people, and are critical in identifying and referring adolescent self‐injurers. This study explored what adolescents believe parents and teachers can do to help young people who self‐injure. A school‐based sample of 2637 students (aged 12–18 years) completed a self‐report questionnaire. Adolescents believe having non‐judgemental parents and teachers to talk to, improved parent–child relationships, referral to professionals, reduced school pressures, and student education, are pivotal to helping young self‐injurers. However, many adolescents, particularly those exposed to NSSI, were unsure about whether parents and teachers could do anything to help. These finding have important implications for educational programs that prepare parents and teachers to address adolescent NSSI.
Simulating effects of biomarker enrichment on Alzheimer's disease prevention trials: Conceptual framework and example
Authors: Leoutsakos Jeannie‐Marie S. , Bartlett Alexandra L. , Forrester Sarah N. , Lyketsos Constantine G. 
Published: August 2013

AbstractBackgroundWe present a conceptual framework for simulations to determine the utility of biomarker enrichment to increase statistical power to detect a treatment effect in future Alzheimer's disease prevention trials. We include a limited set of simulation results to illustrate aspects of this framework.MethodsWe simulated data based on the Alzheimer's Disease Anti‐Inflammatory Prevention Trial, and a range of sample sizes, biomarker positive predictive values, and treatment effects. We also investigated the consequences of assuming homogeneity of parameter estimates as a function of dementia outcome.ResultsUse of biomarkers to increase the sample fraction that would develop Alzheimer's disease in the absence of intervention from 0.5 to 0.8 would increase power from 0.35 to 0.69 with n = 200. Ignoring sample heterogeneity resulted in overestimation of power.ConclusionBiomarker enrichment can increase statistical power, but estimates of the expected increase are sensitive to a variety of assumptions outlined in the framework.
The iron cage exposed: Institutional pressures and heterogeneity across the healthcare supply chain
Authors: Bhakoo Vikram , Choi Thomas 
Published: August 2013

AbstractThe healthcare industry has been known to operate in a strong institutional environment (i.e. government regulations), and the implementation of inter‐organizational systems (IOS) has followed an institutional process. Extending this perspective across different tiers in the healthcare supply chain, we investigate how organizations in different tiers in the supply chain (i.e. hospitals, distributors and manufacturers) respond to institutional pressures when implementing IOS. How institutional dynamics unfold across multiple tiers of a supply chain is an uncharted area of research, and we take the theory‐building case study approach using data collected from ten organizations. Because organizations are embedded in their respective tiers, our within‐tier analyses are equivalent to cross‐organization analyses. In this regard, the cross‐case analyses occur at two different levels: at each tier level (i.e. across multiple hospitals, multiple distributors and multiple manufacturers) and across the supply chain (i.e. across all three tiers). The study shows how different institutional pressures such as coercive, mimetic, and normative manifest across the tiers. It also demonstrates how a differential mix of endogenous and institutional pressures lead to mixed organizational responses across the tiers. The propositions developed from the study enrich institutional theory arguments within the information systems and supply chain management disciplines. They highlight how the IOS implementation dynamics within and across different tiers in a supply chain result in heterogeneous rather than isomorphic consequences, thereby exposing the “iron cage” of institutionalization.
Mixing in a vortex breakdown flow
Authors: Meunier P. , Hourigan K. 
Published: August 2013

AbstractIn this paper we present experimental and theoretical results on the mixing inside a cylinder with a rotating lid. The helical flow that is created by the rotation of the disc is well known to exhibit a vortex breakdown bubble over a finite range of Reynolds numbers. The mixing properties of the flow are analysed quantitatively by measuring the exponential decay of the variance as a function of time. This homogenization time is extremely sensitive to the asymmetries of the flow, which are introduced by tilting the rotating or the stationary disc and accurately measured using particle image velocimetry (PIV). In the absence of vortex breakdown, the homogenization time is strongly decreased (by a factor of 10) with only a moderate tilt angle of the rotating lid (of the order of $1{5}^{\circ } $). This phenomenon can be explained by the presence of small radial jets at the periphery which create a strong convective mixing. A simple model of exchange flow between the periphery and the bulk correctly predicts the scaling laws for the homogenization time. In the presence of vortex breakdown, the scalar is trapped inside the vortex breakdown bubble, and thus increases substantially the time needed for homogenization. Curiously, the tilt of the rotating lid has a weak effect on the mixing, but a small tilt of the stationary disc (of the order of ${2}^{\circ } $) strongly decreases (by a factor of 10) the homogenization time. Even more surprising is that the homogenization time diverges when the size of the bubble vanishes. All of these features are recovered by applying the Melnikov theory to calculate the volume of the lobes that exit the bubble. It is the first time that this technique has been applied to a three-dimensional stationary flow with a non-axisymmetric perturbation and compared with experimental results, although it has been applied often to two-dimensional flows with a periodic perturbation.
Global bifurcations to subcritical magnetorotational dynamo action in Keplerian shear flow
Authors: Riols A. , Rincon F. , Cossu C. , Lesur G. , Longaretti P.-Y. , Ogilvie G. I. , Herault J. 
Published: August 2013

AbstractMagnetorotational dynamo action in Keplerian shear flow is a three-dimensional nonlinear magnetohydrodynamic process, the study of which is relevant to the understanding of accretion processes and magnetic field generation in astrophysics. Transition to this form of dynamo action is subcritical and shares many characteristics with transition to turbulence in non-rotating hydrodynamic shear flows. This suggests that these different fluid systems become active through similar generic bifurcation mechanisms, which in both cases have eluded detailed understanding so far. In this paper, we build on recent work on the two problems to investigate numerically the bifurcation mechanisms at work in the incompressible Keplerian magnetorotational dynamo problem in the shearing box framework. Using numerical techniques imported from dynamical systems research, we show that the onset of chaotic dynamo action at magnetic Prandtl numbers larger than unity is primarily associated with global homoclinic and heteroclinic bifurcations of nonlinear magnetorotational dynamo cycles born out of saddle-node bifurcations. These global bifurcations are found to be supplemented by local bifurcations of cycles marking the beginning of period-doubling cascades. The results suggest that nonlinear magnetorotational dynamo cycles provide the pathway to injection of both kinetic and magnetic energy for the problem of transition to turbulence and dynamo action in incompressible magnetohydrodynamic Keplerian shear flow in the absence of an externally imposed magnetic field. Studying the nonlinear physics and bifurcations of these cycles in different regimes and configurations may subsequently help to understand better the physical conditions of excitation of magnetohydrodynamic turbulence and instability-driven dynamos in a variety of astrophysical systems and laboratory experiments. The detailed characterization of global bifurcations provided for this three-dimensional subcritical fluid dynamics problem may also prove useful for the problem of transition to turbulence in hydrodynamic shear flows.
On the thinnest steady threads obtained by gravitational stretching of capillary jets
Authors: Rubio-Rubio M. , Sevilla A. , Gordillo J. M. 
Published: August 2013

AbstractExperiments and global linear stability analysis are used to obtain the critical flow rate below which the highly stretched capillary jet, generated when a Newtonian liquid issues from a vertically oriented tube, is no longer steady. The theoretical description, based on the one-dimensional mass and momentum equations retaining the exact expression for the interfacial curvature, accurately predicts the onset of jet self-excited oscillations experimentally observed for wide ranges of liquid viscosity and nozzle diameter. Our analysis, which extends the work by Sauter & Buggisch (J. Fluid Mech.vol. 533, 2005, pp. 237–257), reveals the essential stabilizing role played by the axial curvature of the jet, the latter effect being especially relevant for injectors with a large diameter. Our findings allow us to conclude that, surprisingly, the size of the steady threads produced at a given distance from the exit can be reduced by increasing the nozzle diameter.
Bounds for Euler from vorticity moments and line divergence
Authors: Kerr Robert M. 
Published: August 2013

AbstractThe inviscid growth of a range of vorticity moments is compared using Euler calculations of anti-parallel vortices with a new initial condition. The primary goal is to understand the role of nonlinearity in the generation of a new hierarchy of rescaled vorticity moments in Navier–Stokes calculations where the rescaled moments obey ${D}_{m} \geq {D}_{m+ 1} $, the reverse of the usual ${\Omega }_{m+ 1} \geq {\Omega }_{m} $ Hölder ordering of the original moments. Two temporal phases have been identified for the Euler calculations. In the first phase the $1\lt m\lt \infty $ vorticity moments are ordered in a manner consistent with the new Navier–Stokes hierarchy and grow in a manner that skirts the lower edge of possible singular growth with ${ D}_{m}^{2} \rightarrow \sup \vert \boldsymbol{\omega} \vert \sim A_{m}{({T}_{c} - t)}^{- 1} $ where the ${A}_{m} $ are nearly independent of $m$. In the second phase, the new ${D}_{m} $ ordering breaks down as the ${\Omega }_{m} $ converge towards the same super-exponential growth for all $m$. The transition is identified using new inequalities for the upper bounds for the $- \mathrm{d} { D}_{m}^{- 2} / \mathrm{d} t$ that are based solely upon the ratios ${D}_{m+ 1} / {D}_{m} $, and the convergent super-exponential growth is shown by plotting $\log (\mathrm{d} \log {\Omega }_{m} / \mathrm{d} t)$. Three-dimensional graphics show significant divergence of the vortex lines during the second phase, which could be what inhibits the initial power-law growth.