bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis, Stabilization, Functionalization and, DFT Calculations of Gold Nanoparticles in Fluorous Phases (PTFE and Ionic Liquids)
Authors: Redel Engelbert , Walter Michael , Thomann Ralf , Vollmer Christian , Hussein Laith , Scherer Harald , Krüger Michael , Janiak Christoph 
Published: August 2009

AbstractGold nanoparticles (Au‐NPs) were reproducibly obtained by thermal, photolytic, or microwave‐assisted decomposition/reduction under argon from Au(CO)Cl or KAuCl4 in the presence of n‐butylimidazol dispersed in the ionic liquids (ILs) BMIm+BF4−, BMIm+OTf−, or BtMA+NTf2− (BMIm+=n‐butylmethylimidazolium, BtMA+=n‐butyltrimethylammonium, OTf−=−O3SCF3, NTf2−=−N(O2SCF3)2). The ultra small and uniform nanoparticles of about 1–2 nm diameter were produced in BMIm+BF4− and increased in size with the molecular volume of the ionic liquid anion used in BMIm+OTf− and BtMA+NTf2−. Under argon the Au‐NP/IL dispersion is stable without any additional stabilizers or capping molecules. From the ionic liquids, the gold nanoparticles can be functionalized with organic thiol ligands, transferred, and stabilized in different polar and nonpolar organic solvents. Au‐NPs can also be brought onto and stabilized by interaction with a polytetrafluoroethylene (PTFE, Teflon) surface. Density functional theory (DFT) calculations favor interactions between IL anions instead of IL cations. This suggests a Au⋅⋅⋅F interaction and anionic Aun stabilization in fluorine‐containing ILs. The 19F NMR signal in BMIm+BF4− shows a small Au‐NP concentration‐dependent shift. Characterization of the dispersed and deposited gold nanoparticles was done by transmission electron microscopy (TEM/HRTEM), transmission electron diffraction (TED), dynamic light scattering (DLS), UV/Vis absorbance spectroscopy, scanning electron microscopy (SEM), electron spin resonance (ESR), and electron probe micro analyses (EPM, SEM/EDX).
Natural Abundance 25Mg Solid‐State NMR of Mg Oxyanion Systems: A Combined Experimental and Computational Study
Authors: Cahill Lindsay S. , Hanna John V. , Wong Alan , Freitas Jair C. C. , Yates Jonathan R. , Harris Robin K. , Smith Mark E. 
Published: August 2009

AbstractSolid‐state 25Mg magic angle spinning nuclear magnetic resonance (MAS NMR) data are reported from a range of organic and inorganic magnesium–oxyanion compounds at natural abundance. To constrain the determination of the NMR interaction parameters (δiso, χQ, ηQ) data have been collected at three external magnetic fields (11.7, 14.1 and 18.8 T). Corresponding NMR parameters have also been calculated by using density functional theory (DFT) methods using the GIPAW approach, with good correlations being established between experimental and calculated values of both χQ and δiso. These correlations demonstrate that the 25Mg NMR parameters are very sensitive to the structure, with small changes in the local Mg2+ environment and the overall hydration state profoundly affecting the observed spectra. The observations suggest that 25Mg NMR spectroscopy is a potentially potent probe for addressing some key problems in inorganic materials and of metal centres in biologically relevant molecules.
One‐Step Synthesis of Folic Acid Protected Gold Nanoparticles and Their Receptor‐Mediated Intracellular Uptake
Authors: Li Gaiping , Li Dan , Zhang Lixue , Zhai Junfeng , Wang Erkang 
Published: August 2009

AbstractWe report here a facile method to obtain folic acid (FA)‐protected gold nanoparticles (Au NPs) by heating an aqueous solution of HAuCl4/FA in which FA acts as both the reducing and stabilizing agent. The successful formation of FA‐protected Au NPs is demonstrated by UV/Vis spectroscopy, transmission electron microscopy (TEM), selected‐area electron diffraction (SAED), X‐ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). The intracellular uptake of these nanoparticles is facilitated by HeLa cells overexpressing the folate reporter, which itself is significantly inhibited by free FA in a competitive assay as quantified by inductively coupled plasma mass spectroscopy (ICP‐MS). This simple one‐step approach affords a new perspective for creating functional nanomaterials, and the resulting biocompatible, functional Au NPs may find some prospective applications in various biomedical fields.
From Mono‐ to Poly‐Substituted Frameworks: A Way of Tuning the Acidic Character of CcH in o‐Carborane Derivatives
Authors: Puga Alberto V. , Teixidor Francesc , Sillanpää Reijo , Kivekäs Raikko , Arca Massimiliano , Barberà Gemma , Viñas Clara 
Published: August 2009

AbstractThe incorporation of iodine atoms onto the boron vertices of the o‐carborane framework causes, according to spectroscopic data, a uniform increase in the acidic character of the CcH (Cc= cluster carbon) vertices, whereas the incorporation of methyl groups onto the boron vertices of the o‐carborane framework reduces their acidity. Methyl groups when attached to boron are electron‐withdrawing in boron clusters, whereas iodine atoms bonded to boron act as electron donors. This has been proven on B‐methyl and B‐iodinated o‐carboranes with NMR spectroscopy measurements and DFT calculations of natural bond orbital (NBO) charges, which show a cumulative buildup of positive cluster‐only total charge (CTC) on B‐methyl o‐carboranes and a cumulative buildup of negative cluster‐only total charge for B‐iodinated o‐carboranes.
Iodinated ortho‐Carboranes as Versatile Building Blocks to Design Intermolecular Interactions in Crystal Lattices
Authors: Puga Alberto V. , Teixidor Francesc , Sillanpää Reijo , Kivekäs Raikko , Viñas Clara 
Published: August 2009

AbstractThe crystal structures of numerous iodinated ortho‐carboranes have been studied, which has revealed the diversity of intermolecular interactions that these substances can adopt in the solid state. The nature—mostly as it relates to hydrogen and/or halogen bonds—and relative strength of such interactions can be adjusted by selectively introducing substituents onto the cluster, thus enabling the rational design of crystal lattices. In this work we present the newly determined crystal structures of the following iodinated ortho‐carboranes: 9‐I‐1,2‐closo‐C2B10H11, 4,5,7,8,9,10,11,12‐I8‐1,2‐closo‐C2B10H4, 3,4,5,6,7,8,9,10,11,12‐I10‐1,2‐closo‐C2B10H2, 1‐Me‐8,9,10,12‐I4‐1,2‐closo‐C2B10H7, 1,2‐Me2‐8,9,10,12‐I4‐1,2‐closo‐C2B10H6, and 1,2‐Ph2‐8,9,10,12‐I4‐1,2‐closo‐C2B10H6. Their 3D supramolecular organization has been thoroughly investigated and compared to similar previously published crystal structures. Such a systematic survey has allowed us to draw some general trends. CcH⋅⋅⋅IB hydrogen bonds (Cc= cluster carbon atoms) appear to be significant in the growth of the crystal lattices of these compounds, given the acidity of hydrogen atoms bonded to Cc, and the polarization of BI bonds. These hydrogen bonds can be disrupted by selectively blocking the positions next to Cc, that is, B(3) and B(6), with bulky substituents that prevent iodine atoms from approaching as hydrogen acceptors. Halogen bonds of the type BI⋅⋅⋅IB are frequently observed in most cases, thus suggesting that these interactions could be attractive in boron clusters. In addition, different substituents can be grafted onto the ortho‐carborane surface, thereby providing further possibilities for homomeric or heteromeric molecular assembly.
Tripeptides of the Type H‐D‐Pro‐Pro‐Xaa‐NH2 as Catalysts for Asymmetric 1,4‐Addition Reactions: Structural Requirements for High Catalytic Efficiency
Authors: Wiesner Markus , Neuburger Markus , Wennemers Helma 
Published: August 2009

AbstractAnalysis of the structural and functional requirements within the asymmetric peptidic catalyst H‐D‐Pro‐Pro‐Asp‐NH2 led to the development of the closely related peptide H‐D‐Pro‐Pro‐Glu‐NH2 as an even more efficient catalyst for asymmetric conjugate addition reactions of aldehydes to nitroolefins. In the presence of as little as 1 mol % of H‐D‐Pro‐Pro‐Glu‐NH2, a broad range of aldehydes and nitroolefins react readily with each other. The resulting γ‐nitroaldehydes were obtained in excellent yields and stereoselectivities at room temperature. Within the structure of the peptidic catalysts, the D‐Pro‐Pro motif is the major contributor to the high stereoselectivities. The C‐terminal amide and the spacer to the carboxylic acid in the side‐chain of the C‐terminal amino acid are responsible for the fine‐tuning of the stereoselectivity. The peptidic catalysts not only allow for highly effective asymmetric catalysis under mild conditions, but also function in the absence of additives.
Asymmetric [2,3]‐Wittig Rearrangement of Oxygenated Allyl Benzyl Ethers in the Presence of a Chiral di‐tBu‐bis(oxazoline) Ligand: A Novel Synthetic Approach to THF Lignans
Authors: Kitamura Maria , Hirokawa Yoshimi , Maezaki Naoyoshi 
Published: August 2009

AbstractWe have accomplished highly enantioselective [2,3]‐Wittig rearrangements of functionalized allyl benzyl ethers in the presence of a chiral di‐tBu‐bis(oxazoline) ligand. In various oxygenated benzylic ethers, the reactions proceeded with excellent diastereo‐ and enantioselectivities, although the presence of a methoxy substituent at the ortho‐position on the benzyl group drastically decreased the enantioselectivity. Conversely, o‐ethyl and o‐phenyl substituents had no significant effect on the selectivity. We found that the C2‐substituent of the allylic moiety played an important role in producing high enantioselectivity. Highly enantioselective [2,3]‐Wittig rearrangement in the presence of catalytic amounts of the chiral ligands is also described.
Enhanced Reactivities of Iron(IV)‐Oxo Porphyrin π‐Cation Radicals in Oxygenation Reactions by Electron‐Donating Axial Ligands
Authors: Kang Yaeun , Chen Hui , Jeong Yu Jin , Lai Wenzhen , Bae Eun Hae , Shaik Sason , Nam Wonwoo 
Published: August 2009

AbstractThe proximal axial ligand in heme iron enzymes plays an important role in tuning the reactivities of iron(IV)‐oxo porphyrin π‐cation radicals in oxidation reactions. The present study reports the effects of axial ligands in olefin epoxidation, aromatic hydroxylation, alcohol oxidation, and alkane hydroxylation, by [(tmp)+. FeIV(O)(p‐Y‐PyO)]+ (1‐Y) (tmp=meso‐tetramesitylporphyrin, p‐Y‐PyO=para‐substituted pyridine N‐oxides, and Y=OCH3, CH3, H, Cl). In all of the oxidation reactions, the reactivities of 1‐Y are found to follow the order 1‐OCH3 > 1‐CH3 > 1‐H > 1‐Cl; negative Hammett ρ values of −1.4 to −2.7 were obtained by plotting the reaction rates against the σp values of the substituents of p‐Y‐PyO. These results, as well as previous ones on the effect of anionic nucleophiles, show that iron(IV)‐oxo porphyrin π‐cation radicals bearing electron‐donating axial ligands are more reactive in oxo‐transfer and hydrogen‐atom abstraction reactions. These results are counterintuitive since iron(IV)‐oxo porphyrin π‐cation radicals are electrophilic species. Theoretical calculations of anionic and neutral ligands reproduced the counterintuitive experimental findings and elucidated the root cause of the axial ligand effects. Thus, in the case of anionic ligands, as the ligand becomes a better electron donor, it strengthens the FeOH bond and thereby enhances its H‐abstraction activity. In addition, it weakens the FeO bond and encourages oxo‐transfer reactivity. Both are Bell–Evans–Polanyi effects, however, in a series of neutral ligands like p‐Y‐PyO, there is a relatively weak trend that appears to originate in two‐state reactivity (TSR). This combination of experiment and theory enabled us to elucidate the factors that control the reactivity patterns of iron(IV)‐oxo porphyrin π‐cation radicals in oxidation reactions and to resolve an enigmatic and fundamental problem.
Epothilone Analogues with Benzimidazole and Quinoline Side Chains: Chemical Synthesis, Antiproliferative Activity, and Interactions with Tubulin
Authors: Dietrich Silvia Anthoine , Lindauer Renate , Stierlin Claire , Gertsch Jürg , Matesanz Ruth , Notararigo Sara , Díaz José Fernando , Altmann Karl‐Heinz 
Published: August 2009

AbstractA series of epothilone B and D analogues bearing isomeric quinoline or functionalized benzimidazole side chains has been prepared by chemical synthesis in a highly convergent manner. All analogues have been found to interact with the tubulin/microtubule system and to inhibit human cancer cell proliferation in vitro, albeit with different potencies (IC50 values between 1 and 150 nM). The affinity of quinoline‐based epothilone B and D analogues for stabilized microtubules clearly depends on the position of the N‐atom in the quinoline system, while the induction of tubulin polymerization in vitro appears to be less sensitive to N‐positioning. The potent inhibition of human cancer cell growth by epothilone analogues bearing functionalized benzimidazole side chains suggests that these systems might be conjugated with tumor‐targeting moieties to form tumor‐targeted prodrugs.
Synthesis of stoichiometric LiNbO3 nanopowder through a wet chemical method
Authors: Yao Shuhua , Zheng Feifei , Liu Hong , Wang Jiyang , Zhang Huaijin , Yan Tao , Wu Jianbo , Xia Zongren , Qin Xiaoyong 
Published: August 2009

AbstractStoichiometric lithium niobate powder which are used as feeding material in near stoichometric LiNbO3 crystal growth have been successfully prepared from commercial niobium hydroxide [Nb(OH)5] and nontoxic DL‐malic acid by a wet chemical method. The synthesis temperature was pre‐determined by the results from thermogravimetric and differential thermal analysis. The structure and morphology of the as‐prepared samples were observed by using the infrared spectroscopy and the scanning electron microscopy. The X‐ray diffraction experiment showed that lithium niobate powder had an ilmenite structure, and its unit cell parameters were calculated to be a = b = 0.5140 nm, c = 1.3738 nm, and V = 0.3144 nm3. The melting point of the synthesized powder is 1239 °C and Curie temperature Tc is 1122 °C. This synthesis method would be helpful to grow the near‐stoichiometric LiNbO3 crystal with double crucible techniques. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sonochemical synthesis and characterization of ZnO nanorod/Ag nanoparticle composites
Authors: Li Fei , Liu Xueqin , Qin Qinghua , Wu Jianfang , Li Zhen , Huang Xintang 
Published: August 2009

AbstractA simple sonochemical route for the synthesis of Ag nanoparticles on ZnO nanorods is reported. Ultrasonic irradiation of a mixture of ZnO nanorods, Ag(NH3)2+, and formaldehyde in an aqueous medium yields ZnO nanorod/Ag nanoparticle composites. The powder X‐ray diffraction of the ZnO/Ag composites shows additional diffraction peaks corresponding to the face‐center‐cubic structured Ag crystalline, apart from the signals from the ZnO nanorods. Scanning electron microscopy and transmission electron microscopy images of the ZnO/Ag composites reveal that the ZnO nanorods are coated with Ag nanoparticles with a mean size of several tens nanometer. The absorption band of ZnO/Ag composites is distinctly broadened and red‐shifted, indicating the strong interfacial interaction between ZnO nanorods and Ag nanoparticles. This sonochemical method is simple, mild and readily scaled up, affording a simple way for synthesis of other composites. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Defect structure characteristics in near‐stoichiometric In:LiNbO3 single crystals grown by K2O‐flux method
Authors: Fang Shuangquan , Han Zhaoxiang , Qiao Yingjie , Liu Yingying , Jia Qi 
Published: August 2009

AbstractWith K2O as flux, near‐stoichiometric In:LiNbO3 (In:SLN) crystals with different indium contents were grown by the top seed solution growth (TSSG) method. Defect structure characteristics and the replacement principle of extrinsic ions were derived from X‐ray powder diffraction, differential thermal analysis (DTA), ultraviolet‐visible (UV) absorption and infrared (IR) spectrum measurement. Further analysis indicated that the threshold concentration of In2O3 in near‐stoichiometric LiNbO3 crystals were about 1.1 mol%. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis and field emission properties of SnO2 nanowalls
Authors: Li L. J. , Yu K. , Wang Y. 
Published: August 2009

AbstractSnO2 nanowalls were synthesized on silicon substrate by the thermal chemical vapor transport method at a low temperature of around 650 °C under atmospheric pressure. The microstructure and morphology of the SnO2 nanowalls were evaluated by using scanning electron microscopies and X‐ray diffraction. Room temperature photoluminescence spectra of the nanowalls showed a broad emission band centering at about 530 nm. Field emission measurements demonstrated that the nanowalls possessed good performance with a turn‐on field of ∼3.5 V/μm and a threshold field of ∼6.1 V/μm. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Columnar grain growth pattern with fluid flowing in molten pool
Authors: Ma Rui , Dong Zhibo , Wei Yanhong , Zhan Xiaohong , Wang Yong 
Published: August 2009

AbstractA coupled model was used to simulate columnar grain growth in TIG (tungsten inert‐gas) molten pool of nickel base alloy. The cellular automaton algorithm for dendritic growth is incorporated with solute transport model to take fluid flow into consideration. The results indicate that shear flow changes the solute distribution at the S/L (Solid/Liquid) interface, leading to asymmetrical growth of columnar grains. The dendrite arms on the upstream side grow fast, while the growth of dendrite arms on the downstream side is much delayed. However, dendrite arms on both sides are not as well‐developed as the grain growth without flow. With inlet flow velocity increasing, the phenomenon becomes more obvious. In addition, shear flow also results in more severe coring segregation. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis of Ru microspheres by self‐assembly in tungstosilicate acid solution and photocatalytic degradability of cango red
Authors: Zhang Li , Wang Hongyan , Wang Cong 
Published: August 2009

AbstractThe formation of Ru microspheres by hydrothermal treated method in tungstosilicate acid (H4SiW12O40, TSA) solution is described. The particles are characterized by X‐ray diffraction analysis (XRD) and scanning electron microscopy (SEM), respectively. The growth process of these microspheres has been examined. The results show that it is possible to synthesize and assemble other noble metal particles with unique superstructure. The characteristic catalytic behavior of the Ru microspheres is established by studying the decolorization of cango red in the presence of UV light. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An effective IPv4–IPv6 translation mechanism for SIP applications in next generation networks
Authors: Chen Whai‐En , Huang Ya‐Lin , Lin Yi‐Bing 
Published: August 2009

AbstractIn a next generation network, the IPv6‐enabled IP multimedia subsystem (IMS) network may connect to an IPv4 network. When an IPv4/IPv6 dual‐stack user equipment (UE) initiates a call by sending an IPv6 SIP INVITE message to an IPv4‐only user agent (UA), the call cannot be established correctly. To resolve this problem, the IMS‐application layer gateway solution, the redirect solution, and the interactive connectivity establishment solution have been proposed. In this paper, we propose an effective solution where only the IPv6 INVITE message is translated into an IPv4 INVITE message. Upon receipt of the IPv4 200 OK message replied from the IPv4‐only UA, the dual‐stack UE learns that the correspondent UA supports IPv4‐only and utilizes IPv4 instead of IPv6 to send the subsequent SIP messages and real‐time transport protocol (RTP) packets. The proposed solution is compared with the existing solutions in terms of network node modification, call setup complexity, and RTP transmission latency. Our study indicates that the proposed solution outperforms the other three solutions in the call setup and the RTP transmission. Copyright © 2009 John Wiley & Sons, Ltd.
Auditory stream biasing in children with reading impairments
Authors: Ouimet Tialee , Balaban Evan 
Published: August 2009

AbstractReading impairments have previously been associated with auditory processing differences. We examinedauditory stream biasing, a global aspect of auditory temporal processing. Children with reading impairments, control children and adults heard a 10 s long stream‐bias‐inducing sound sequence (a repeating 1000 Hz tone) and a test sequence (eight repetitions of two pure tones of 1000 and 1420 Hz in an XYX‐XYX… pattern) with a variable delay interval (from 0.09 to 8 s) between the two sequences. Reading‐impaired children had a significantly lower proportion of streamed responses than control children and adults. Streamed responses in reading‐impaired participants differed according to their musical experience, but musically experienced reading‐impaired participants were still significantly different from musically experienced controls. Reading impairments are associated with global differences in auditory integration, and musical experience needs to be considered when investigating auditory processing capabilities. Copyright © 2009 John Wiley & Sons, Ltd.
High‐sensitivity detection of ATP using bioluminescence at an optical fiber end
Authors: Iinuma Masataka , Ushio Yasuaki , Kuroda Akio , Kadoya Yutaka 
Published: August 2009

AbstractWe investigated the sensitivity of ATP detection based on bioluminescence at an optical fiber end where luciferase molecules were immobilized via silica‐binding protein molecules. Luminescence was detected by an avalanche photodiode (APD), with coupling optics to make full use of the merits of compactness, high quantum efficiency, and low noise of the APD. The core diameter and the numerical aperture of the optical fiber, as well as the design of the coupling optics, were optimized so as to realize high photon‐collection efficiency. A detection limit of about 10−10 M was obtained, which corresponds to 10−15 mol of ATP. A rough estimation shows that the photon count rate is still two orders of magnitude lower than that limited by diffusion or reaction processes, implying a possibility of further improvement of the sensitivity. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(9): 53–59, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10054
Mechanical dissociation of retinal neurons with vibration
Authors: Motomura Tamami , Hayashida Yuki , Murayama Nobuki 
Published: August 2009

AbstractNeuromorphic devices that implement the functions of biological neural circuits by means of VLSI technology have been attracting great attention in engineering fields in the last decade. Concurrently, progress in neuroscience research has demonstrated nonlinear computations at the single neuron level, suggesting that individual neurons are not merely passive circuit elements but computational units. Thus, elucidating the properties of neuronal signal processing is an essential step in developing the next generation of neuromorphic devices. In this study, we developed a method of dissociating single neurons from specific sublayers of mammalian retinas without using proteolytic enzymes, instead combining tissue incubation in a low‐Ca2+ medium with a vibrodissociation technique previously developed for slices of brain and spinal cord. Our method takes less time and requires less manual skill than in the conventional enzymatic method, but yields a sufficient number of cells usable for acute electrophysiological experiments. Single retinal neurons dissociated by our method are useful for measuring nonlinear membrane conductances as well as spike firing properties in the perforated‐patch whole‐cell configuration. These neurons also enable us to investigate the effects of proteolytic enzymes on membrane excitability in such cells. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(9): 43–52, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10062