bluuebunny/crossref_metadata_2025_split huggingface dataset:
Galvanic Replacement Reactions of Active‐Metal Nanoparticles
Authors: Niu Kai‐Yang , Kulinich Sergei A. , Yang Jing , Zhu Aaron L. , Du Xi‐Wen 
Published: February 2012

AbstractWe present a systemic investigation of a galvanic replacement technique in which active‐metal nanoparticles are used as sacrificial seeds. We found that different nanostructures can be controllably synthesized by varying the type of more noble‐metal ions and liquid medium. Specifically, nano‐heterostructures of noble metal (Ag, Au) or Cu nanocrystals on active‐metal (Mg, Zn) cores were obtained by the reaction of active‐metal nanoparticles with more noble‐metal ions in ethanol; Ag nanocrystal arrays were produced by the reaction of active‐metal nanoparticles with Ag+ ions in water; spongy Au nanospheres were generated by the reaction of active‐metal nanoparticles with AuCl4− ions in water; and SnO2 nanoparticles were prepared when Sn2+ were used as the oxidant ions. The key factors determining the product morphology are shown to be the reactivity of the liquid medium and the nature of the oxidant–reductant couple, whereas Mg and Zn nanoparticles played similar roles in achieving various nanostructures. When microsized Mg and Zn particles were used as seeds in similar reactions, the products were mainly noble‐metal dendrites. The new approach proposed in this study expands the capability of the conventional nanoscale galvanic replacement method and provides new avenues to various structures, which are expected to have many potential applications in catalysis, optoelectronics, and biomedicine.
Unifying Metal‐ and Organocatalysis for Asymmetric Oxidative Iminium Activation: A Relay Catalytic System Enabling the Combined Allylic Oxidation of Alcohols and Prolinol Ether Catalyzed Iminium Reactions
Authors: Rueping Magnus , Sundén Henrik , Sugiono Erli 
Published: February 2012

AbstractA multicatalytic system consisting of tetrapropylammonium perruthenate/N‐methylmorpholine N‐oxide (TPAP/NMO) as oxidant, and diarylprolinol TMS‐ether as chiral amine catalyst, has been developed and applied in the efficient construction of valuable chiral molecules. The one‐pot domino reactions elaborated in the present study are based on the in situ generation of α,β‐unsaturated aldehydes from allylic alcohols and their subsequent use in various asymmetric transformations (e.g., cyclopropanation, Michael addition, Michael addition/acetalization). TPAP as a substrate‐selective redox catalyst is well tolerated by the amine catalyst and the domino reactions proceed in good yields and high enantioselectivities. The compatibility of metal and organocatalysis presented herein widens the scope of asymmetric iminium catalysis.
A Chemo‐Mechanical Tweezer for Single‐Molecular Characterization of Soft Materials
Authors: Guo Jun , Chen Guojun , Ning Xinghai , Li Xiuru , Zhou Jianfeng , Jagielska Anna , Xu Bingqian , Boons Geert‐Jan 
Published: February 2012

AbstractA new atomic force microscopy (AFM)‐based chemo‐mechanical tweezer has been developed that can measure mechanical properties of individual macromolecules in supramolecular assembly and reveal positions of azide‐containing polymers. A key feature of the new technology is the use of an AFM tip densely modified with 4‐dibenzocyclooctynols (chemo‐mechanical tweezer) that can react with multiple azide containing macromolecules of micelles to give triazole “clicked” compounds, which during retracting phases of AFM imaging are removed from the macromolecular assembly thereby providing a surface topographical image and positions of azide‐containing polymers. The force–distance curves gave mechanical properties of removal of individual molecules from a supramolecular assembly. The new chemo‐mechanical tweezer will make it possible to characterize molecular details of macromolecular assemblies thereby offering new avenues to tailor properties of such assemblies.
High‐Pressure Synthesis and Structural Investigation of H3P8O8N9: A New Phosphorus(V) Oxonitride Imide with an Interrupted Framework Structure
Authors: Sedlmaier Stefan J. , Celinski Vinicius R. , Schmedt auf der Günne Jörn , Schnick Wolfgang 
Published: February 2012

AbstractThe first crystalline phosphorus oxonitride imide H3P8O8N9 (=P8O8N6(NH)3) has been synthesized under high‐pressure and high‐temperature conditions. To this end, a new, highly reactive phosphorus oxonitride imide precursor compound was prepared and treated at 12 GPa and 750 °C by using a multianvil assembly. H3P8O8N9 was obtained as a colorless, microcrystalline solid. The crystal structure of H3P8O8N9 was solved ab initio by powder X‐ray diffraction analysis, applying the charge‐flipping algorithm, and refined by the Rietveld method (C2/c (no. 15), a=1352.11(7), b=479.83(3), c=1820.42(9) pm, β=96.955(4)°, Z=4). H3P8O8N9 exhibits a highly condensed (κ=0.47), 3D, but interrupted network that is composed of all‐side vertex‐sharing (Q4) and only threefold‐linking (Q3) P(O,N)4 tetrahedra in a Q4/Q3 ratio of 3:1. The structure, which includes 4‐ring assemblies as the smallest ring size, can be subdivided into alternating open‐branched zweier double layers {oB,${2{{2\hfill \atop \infty \hfill}}}$}[2P3(O,N)7] and layers containing pairwise‐linked Q3 tetrahedra parallel (001). Information on the hydrogen atoms in H3P8O8N9 was obtained by 1D 1H MAS, 2D homo‐ and heteronuclear (together with 31P) correlation NMR spectroscopy, and a 1H spin‐diffusion experiment with a hard‐pulse sequence designed for selective excitation of a single peak. Two hydrogen sites with a multiplicity ratio of 2:1 were identified and thus the formula of H3P8O8N9 was unambiguously determined. The protons were assigned to Wyckoff positions 8f and 4e, the latter located within the Q3 tetrahedra layers.
Preparation and Photophysical and Photoelectrochemical Properties of a Covalently Fixed Porphyrin–Chemically Converted Graphene Composite
Authors: Umeyama Tomokazu , Mihara Junya , Tezuka Noriyasu , Matano Yoshihiro , Stranius Kati , Chukharev Vladimir , Tkachenko Nikolai V. , Lemmetyinen Helge , Noda Kei , Matsushige Kazumi , Shishido Tetsuya , Liu Zheng , Hirose‐Takai Kaori , Suenaga Kazu , Imahori Hiroshi 
Published: February 2012

AbstractChemically converted graphene (CCG) covalently linked with porphyrins has been prepared by a Suzuki coupling reaction between iodophenyl‐functionalized CCG and porphyrin boronic ester. The covalently linked CCG–porphyrin composite was designed to possess a short, rigid phenylene spacer between the porphyrin and the CCG. The composite material formed stable dispersions in DMF and the structure was characterized by spectroscopic, thermal, and microscopic measurements. In steady‐state photoluminescence spectra, the emission from the porphyrin linked to the CCG was quenched strongly relative to that of the porphyrin reference. Fluorescence lifetime and femtosecond transient absorption measurements of the porphyrin‐linked CCG revealed a short‐lived porphyrin singlet excited state (38 ps) without yielding the porphyrin radical cation, thereby substantiating the occurrence of energy transfer from the porphyrin excited state to the CCG and subsequent rapid decay of the CCG excited state to the ground state. Consistently, the photocurrent action spectrum of a photoelectrochemical device with a SnO2 electrode coated with the porphyrin‐linked CCG exhibited no photocurrent response from the porphyrin absorption. The results obtained here provide deep insight into the interaction between graphenes and π‐conjugated systems in the excited and ground states.
Theoretical Study on the Mechanism of Ni‐Catalyzed Alkyl–Alkyl Suzuki Cross‐Coupling
Authors: Li Zhe , Jiang Yuan‐Ye , Fu Yao 
Published: February 2012

AbstractNi‐catalyzed cross‐coupling of unactivated secondary alkyl halides with alkylboranes provides an efficient way to construct alkyl–alkyl bonds. The mechanism of this reaction with the Ni/L1 (L1=trans‐N,N′‐dimethyl‐1,2‐cyclohexanediamine) system was examined for the first time by using theoretical calculations. The feasible mechanism was found to involve a NiI–NiIII catalytic cycle with three main steps: transmetalation of [NiI(L1)X] (X=Cl, Br) with 9‐borabicyclo[3.3.1]nonane (9‐BBN)R1 to produce [NiI(L1)(R1)], oxidative addition of R2X with [NiI(L1)(R1)] to produce [NiIII(L1)(R1)(R2)X] through a radical pathway, and CC reductive elimination to generate the product and [NiI(L1)X]. The transmetalation step is rate‐determining for both primary and secondary alkyl bromides. KOiBu decreases the activation barrier of the transmetalation step by forming a potassium alkyl boronate salt with alkyl borane. Tertiary alkyl halides are not reactive because the activation barrier of reductive elimination is too high (+34.7 kcal mol−1). On the other hand, the cross‐coupling of alkyl chlorides can be catalyzed by Ni/L2 (L2=trans‐N,N′‐dimethyl‐1,2‐diphenylethane‐1,2‐diamine) because the activation barrier of transmetalation with L2 is lower than that with L1. Importantly, the Ni0–NiII catalytic cycle is not favored in the present systems because reductive elimination from both singlet and triplet [NiII(L1)(R1)(R2)] is very difficult.
Generating Orally Active Galanin Analogues with Analgesic Activities
Authors: Robertson Charles R. , Pruess Timothy H. , Grussendorf Erin , White H. Steve , Bulaj Grzegorz 
Published: February 2012

AbstractThe endogenous neuropeptide galanin has anticonvulsant and analgesic properties mediated by galanin receptors expressed in the central and peripheral nervous systems. Our previous work showed that by combining truncation of the galanin peptide with N‐ and C‐terminal modifications afforded analogues that suppress seizures or pain upon intraperitoneal (i.p.) administration. To generate orally active galanin analogues, the previously reported lead compound Gal‐B2 (NAX 5055) was redesigned by 1) central truncation, (2) introduction of D‐amino acids, and 3) addition of backbone spacers. Analogue D‐Gal(7‐Ahp)‐B2, containing 7‐aminoheptanoic acid as a backbone spacer and an oligo‐D‐lysine motif at the C terminus, exhibits anticonvulsant and analgesic activity post‐i.p. administration. Oral administration of D‐Gal(7‐Ahp)‐B2 demonstrates analgesic activity with decreases in both acute and inflammatory pain in the mouse formalin model of pain at doses as low as 8 mg kg−1.
Computational modelling of cardiac electrophysiology: explanation of the variability of results from different numerical solvers
Authors: Pathmanathan P. , Bernabeu M.O. , Niederer S.A. , Gavaghan D.J. , Kay D. 
Published: February 2012

SUMMARYA recent verification study compared 11 large‐scale cardiac electrophysiology solvers on an unambiguously defined common problem. An unexpected amount of variation was observed between the codes, including significant error in conduction velocity in the majority of the codes at certain spatial resolutions. In particular, the results of the six finite element codes varied considerably despite each using the same order of interpolation. In this present study, we compare various algorithms for cardiac electrophysiological simulation, which allows us to fully explain the differences between the solvers. We identify the use of mass lumping as the fundamental cause of the largest variations, specifically the combination of the commonly used techniques of mass lumping and operator splitting, which results in a slightly different form of mass lumping to that supported by theory and leads to increased numerical error. Other variations are explained through the manner in which the ionic current is interpolated. We also investigate the effect of different forms of mass lumping in various types of simulation. Copyright © 2012 John Wiley & Sons, Ltd.
A model of axonal transport drug delivery: effects of diffusivity
Authors: Kuznetsov A.V. 
Published: February 2012

SUMMARYThis paper investigates the effects of diffusivity on retrograde dynein‐driven transport of pharmaceutical agent complexes (PACs) in axons. The model is designed with two goals in mind: (1) to capture results on axonal transport drug delivery reported in recent experimental research by Filler et al. (Filler AG, Whiteside GT, Bacon M, Frederickson M, Howe FA, Rabinowitz MD, Sokoloff AJ, Deacon TW, Abell C, Munglani R, Griffiths JR, Bell BA, Lever AML. Tri‐partite complex for axonal transport drug delivery achieves pharmacological effect. BMC Neuroscience 2010; 11: 8) and (2) to produce analytically tractable equations. It is shown that the inclusion of a diffusion process in the model produces equations that can still be solved by Laplace transform, although the last step of the solution, finding the inverse Laplace transform, has to be accomplished numerically, thus leading to a hybrid analytical and numerical solution technique. The effects of diffusivity and the kinetic rates describing PAC transition between the dynein‐driven and accumulated states on transport of PACs toward the neuron soma are investigated. Copyright © 2012 John Wiley & Sons, Ltd.
Azafullerene C59N–Phthalocyanine Dyad: Synthesis, Characterisation and Photoinduced Electron Transfer
Authors: Rotas Georgios , Ranta Jenni , Efimov Alexander , Niemi Marja , Lemmetyinen Helge , Tkachenko Nikolai , Tagmatarchis Nikos 
Published: February 2012

AbstractThe synthesis of a new azafullerene C59N–phthalocyanine (Pc) dyad is described. The key step for the synthesis of the C59N–Pc dyad was the formation of the C59N‐based carboxylic acid, which was smoothly condensed with hydroxy‐modified Pc. The structure of the C59N–Pc dyad was verified by 1H and 13C NMR spectroscopy, IR spectroscopy, UV/Vis spectroscopy and MS measurements. The photophysical and electrochemical properties of the C59N–Pc dyad were investigated in both polar and non‐polar solvents by steady state and time‐resolved photoluminescence and absorption spectroscopy, as well as by cyclic voltammetry. Different relaxation pathways for the photoexcited C59N–Pc dyad, as a result of changing the solvent polarity, were found, thus giving rise to energy‐transfer phenomena in non‐polar toluene and charge‐transfer processes in polar benzonitrile. Finally, the detailed quenching mechanisms were evaluated and compared with that of a C60–Pc dyad, which revealed that the different excited‐state energies and reduction potentials of the two fullerene spheres (i.e. C59N vs. C60) strongly diverged in the deactivation pathways of the excited states of the corresponding phthalocyanine dyads.
Shear Modulus of a Coulomb Crystal of Ions: Effects of Ion Motion and Electron Background Polarization
Authors: Baiko D. A. 
Published: February 2012

AbstractShear modulus of a body‐centered cubic Coulomb crystal of ions is calculated by thermodynamic perturbation theory taking into account ion motion. Classic and quantum regimes of ion motion are considered. The calculations in the classic range of high temperatures agree well with previous Monte Carlo simulations. In this case, the shear modulus is given by a sum of a positive contribution due to the static lattice and a negative ∝ T contribution due to the ion motion. In the quantum regime of low temperatures, the contribution to the shear modulus due to the ion motion saturates at a negative constant value, determined by zero‐point ion vibrations.The correction to the static lattice shear modulus due to the polarization of the electron background is also calculated. The background polarization is described by a dielectric function in the linear response formalism. We compare two dielectric functions (simple Thomas‐Fermi and more realistic Jancovici) and find dependence of the correction to the shear modulus on the ion charge number and the electron degree of relativity.The numerical results are approximated by simple analytical formulas. They can be applied to matter in white dwarf cores and neutron star crusts for precise modeling of oscillations of these astrophysical objects (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamic Screening in Solar and Stellar Nuclear Reactions
Authors: Däppen W. , Mussack K. 
Published: February 2012

AbstractIn the hot, dense plasma of solar and stellar interiors, Coulomb potentials are screened, resulting in increased nuclear reaction rates. Although Salpeter's approximation for static screening is widely accepted and used in stellar modeling, the question of screening in nuclear reactions was revisited in the 1990s. In particular the issue of dynamic effects was raised by Shaviv and Shaviv, who applied the techniques of molecular dynamics to the conditions in the Sun's core in order to numerically determine the effect of screening. By directly calculating the motion of ions and electrons due to Coulomb interactions, the simulations are used to compute the effect of screening without the mean‐field assumption inherent in Salpeter's approximation. In the last few years, the USC group has first reproduced Shaviv and Shaviv's numerical analysis of the screening energy, showing an effect of dynamic screening. When the consequence for the reaction‐rate was computed, a rather surprising resulted, which is contrary to that from static screening theory. Our calculations showed that dynamic screening does not significantly change the reaction rate from that of the bare Coulomb potential. If this can be independently confirmed, then the effects of dynamic screening are highly relevant and should be included in stellar nuclear reaction rates (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Improvement of Wave Packet Molecular Dynamics Using Packet Splitting
Authors: Morozov I. V. , Valuev I. A. 
Published: February 2012

AbstractThe method of Wave Packet Molecular Dynamics Method (WPMD) is a promising replacement of the classical molecular dynamics for the simulations of many‐electron systems including nonideal plasmas. In this contribution we report on a packet splitting technique where an electron is represented by multiple Gaussians, with mixing coefficients playing the role of additional dynamic variables. It provides larger flexibility and better accuracy than the original WPMD with a single Gaussian per electron. As a test case we consider ionization of hydrogen atom in a short laser pulse, where the split packets provide a basis for quantum branching (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An evaluation of the DRI‐ETG EIA method for the determination of ethyl glucuronide concentrations in clinical and post‐mortem urine
Authors: Turfus Sophie C. , Vo Tu , Niehaus Nadia , Gerostamoulos Dimitri , Beyer Jochen 
Published: February 2012

A commercial enzyme immunoassay for the qualitative and semi‐quantitative measurement of ethyl glucuronide (EtG) in urine was evaluated. Post‐mortem (n=800), and clinical urine (n=200) samples were assayed using a Hitachi 902 analyzer. The determined concentrations were compared with those obtained using a previously published liquid chromatography‐tandem mass spectrometry (LC‐MS/MS) method for the quantification of EtG and ethyl sulfate.Using a cut‐off of 0.5 µg/ml and LC‐MS/MS limit of reporting of 0.1 µg/ml, there was a sensitivity of 60.8% and a specificity of 100% for clinical samples. For post‐mortem samples, sensitivity and specificity were 82.4% and 97.1%, respectively. When reducing the cut‐off to 0.1 µg/ml, the sensitivity and specificity were 83.3% and 100% for clinical samples whereas for post‐mortem samples the sensitivity and specificity were 90.3 % and 88.3 %, respectively. The best trade‐offs between sensitivity and specificity for LC‐MS/MS limits of reporting of 0.5 and 0.1 µg/ml were achieved when using immunoassay cut‐offs of 0.3 and 0.092 µg/ml, respectively. There was good correlation between quantitative results obtained by both methods but analysis of samples by LC‐MS/MS gave higher concentrations than by enzyme immunoassay (EIA), with a statistically significant proportional bias (P<0.0001, Deming regression) for both sample types. The immunoassay is reliable for the qualitative and semi‐quantitative presumptive detection of ethyl glucuronide in urine. Copyright © 2012 John Wiley & Sons, Ltd.
Distribution patterns of groundwater‐dependent vegetation species diversity and their relationship to groundwater attributes in northwestern China
Authors: Zhu JunTao , Yu JingJie , Wang Ping , Yu Qiang , Eamus Derek 
Published: February 2012

ABSTRACTThe study of the patterns of plant species diversity and the factors influencing these patterns is the basis of ecology and is also fundamental to conservation biology. Groundwater‐dependent vegetation (GDV) must have access to groundwater to maintain their growth and function, and this is especially common in arid and semi‐arid regions, including north‐western China. In this paper, plant species diversity and groundwater attributes (composition and depth) were investigated in 31 plots in the Ejina Delta in north‐western China to determine whether groundwater attributes influenced patterns species diversity in GDV. Detrended canonical correspondence analyses and generalised additive models were performed to analyse the data. A total of 29 plant species were recorded in the 31 plots; perennial herbs with deep roots had an advantage over all other groups, and GDV species diversity was primarily affected by groundwater depth (GWD), salinity (SAL) and total dissolved solids (TDS), HCO3−, Ca2+, pH, and SO42−. The herb layer species diversity and total species diversity reached their maximum in similar, moderate environmental conditions. The diversity of the tree species was influenced by SAL and TDS and was maximal at large values of GWD and low values of SAL and TDS. The diversity of shrub species was affected by Ca2+ and Mg2+ and was maximal low GWD and high SAL and TDS. Patrick's and Shannon–Wiener's index of the total community diversity presented a bimodal pattern along gradients of GWD and SAL, whilst Simpson's and Pielou's index showed a partially unimodal pattern. On the basis of field investigation and the analysis of field data, we concluded that the perfect combination of GWD and SAL for GDV species diversity is 2 m and 1·8 g l−1, respectively. The appropriate combination range is 2–5 m and 1·8–4·2 g l−1, and the critical combination for the damaged GDV species diversity is 5 m and 4·2 g l−1. Copyright © 2012 John Wiley & Sons, Ltd.
Self‐Assembly of 1D, 2D, and 3D Lanthanide‐Metal Coordination Polymers Based on a 2‐(Pyridin‐4‐yl)‐4,5‐imidazoledicarboxylate Linker: Synthesis, Structures, and Luminescence
Authors: Sun Lin , Li Gui‐Zhu , Xu Mei‐Hua , Li Xiao‐Jian , Li Jian‐Rong , Deng Hong 
Published: February 2012

AbstractThree series of novel lanthanide‐based 1D, 2D, and 3D metallic coordination frameworks involving the 2‐pyridin‐4‐yl‐4,5‐imidazoledicarboxylic acid (H3PIDC) ligand have been characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, and single‐crystal X‐ray diffraction. The compound [Tb(PIDC)(H2O)4]·H3PIDC·4H2O (1) upon slow evaporation at room temperature gave a 1D coordination chain framework constructed of [Tb2O2] dimers bridged through the carboxylate groups of PIDC3– ligands; a 3D supramolecular structure is generated through hydrogen bonding and π–π interactions. The second kind of lanthanide‐based coordination framework, namely [Ln(H2PIDC)(ox)H2O]·3H2O [Ln = Sm (2), Gd (3), Dy (4), and Ho (5), ox = oxalic acid], synthesized under hydrothermal conditions, self‐assemble through Ln2[H2PIDC]2 building blocks and bridging oxalate ligands to give a 2D coordination layer structure. The adjacent layers stack to form a 3D supramolecular framework through weak interactions such as hydrogen bonding and π–π interactions. The third series of lanthanide‐based coordination compounds with chemical formula [Ln(HPIDC)(ox)1/2H2O]·3H2O [Ln = Gd (6), Dy (7), Tb (8) and Ho (9)] were also synthesized by hydrothermal reaction. These isostructural compounds contain an infinite –Ln–O–C–O–Ln– zigzag chain, which connect to each other through the oxygen atoms of the HPIDC2– ligands to form a wave‐like layer. The layers are bridged by oxalate ligands to generate a 3D coordination framework.