bluuebunny/crossref_metadata_2025_split huggingface dataset:
Facile Synthesis of High‐Quality, Water‐Soluble, Near‐Infrared‐Emitting PbS Quantum Dots
Authors: Deng Dawei , Zhang Wenhao , Chen Xinyang , Liu Fei , Zhang Jian , Gu Yueqing , Hong Jianming 
Published: June 2009

AbstractPbS quantum dots (QDs) with strong near‐infrared (NIR) fluorescence have been prepared directly in aqueous solution, by using dihydrolipoic acid (DHLA) as a stabilizer. The photoluminescence (PL) emission maximum could be tuned conveniently over a wide range (from ca. 870 nm to 1010 nm) by manipulating the experimental conditions, such as the Pb/S or DHLA/Pb molar ratios. Under optimized conditions, the maximum PL quantum yield was approximately 10 %. These resultant PbS QDs were highly stable when stored in the dark at 4 °C. After one month of storage, the PL emission intensity decreased by only about 20 %, and no obvious spectral redshift was observed. We scaled up further the synthesis of PbS QDs in the lab, where the concentration of QDs was increased to 8 mM from the usual 1 mM. The experimental results from transmission electron microscopy (TEM) imaging, selected area electron diffraction (SAED), and powder X‐ray diffractometry (XRD) analyses indicated that the as‐prepared PbS QDs had an extremely small diameter (less than 4 nm) and exhibited a face‐centered cubic crystal structure. Such aqueous quantum dots are considered to have tremendous applications in biomedical imaging and the fabrication of nanoscaled devices because of their low toxicity, strong fluorescence, excellent water‐solubility, stability, and biological compatibility relative to other highly toxic thiol (3‐mercaptopropionic acid) stabilized NIR‐emitting QDs (such as CdTe, CdHgTe, HgTe). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Phosphane‐ and Phosphite‐Substituted Diiron Diselenolato Complexes as Models for [FeFe]‐Hydrogenases
Authors: Harb Mohammad K. , Windhager Jochen , Daraosheh Ahmad , Görls Helmar , Lockett L. Tori , Okumura Noriko , Evans Dennis H. , Glass Richard S. , Lichtenberger Dennis L. , El‐khateeb Mohammad , Weigand Wolfgang 
Published: June 2009

AbstractThe displacement of terminal CO ligands in Fe2(μ‐Se2C3H5CH3)(CO)6 (1) by triphenylphosphane, trimethyl phosphite, and bis(diphenylphosphanyl)ethane (dppe) ligands is investigated. Treatment of 1 with 1 equiv. of triphenylphosphane afforded Fe2(μ‐Se2C3H5CH3)(CO)5(PPh3) (2). The mono‐ and disubstituted phosphite complexes Fe2(μ‐Se2C3H5CH3)(CO)5P(OMe)3 (3) and Fe2(μ‐Se2C3H5CH3)(CO)4[P(OMe)3]2 (4) were obtained from the reaction of 1 with excess P(OMe)3 at reflux in toluene. In contrast, the reaction of 1 with 1 equiv. of dppe in the presence of Me3NO·2H2O gave a mixture of Fe2(μ‐Se2C3H5CH3)(CO)4(κ2‐dppe) (5) and [Fe2(μ‐Se2C3H5CH3)(CO)5]2(μ‐dppe) (6). The newly synthesized complexes 2–6 were fully characterized by IR, 1H NMR, 13C NMR, 77Se{1H} NMR, and 31P{1H} NMR spectroscopy, mass spectrometry, elemental analysis, and X‐ray diffraction analysis. Complex 2 has proved to be a catalyst for the electrochemical reduction of the weak acid, acetic acid, to give molecular hydrogen. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Water‐Soluble (Phosphane)gold(I) Complexes – Applications as Recyclable Catalysts in a Three‐Component Coupling Reaction and as Antimicrobial and Anticancer Agents
Authors: Elie Benelita T. , Levine Chaya , Ubarretxena‐Belandia Iban , Varela‐Ramírez Armando , Aguilera Renato J. , Ovalle Rafael , Contel María 
Published: June 2009

AbstractWater‐soluble compounds of the type [AuCl(PR3)] with alkyl‐bis(m‐sulfonated‐phenyl) (mC6H4SO3Na)2 and dialkyl‐(m‐sulfonated‐phenyl) (mC6H4SO3Na) (R = nBu, Cp) phosphanes have been prepared. Dialkylphosphane compounds generate water‐soluble nanoparticles of 10–15 nm radius when dissolved in water. These air‐stable complexes have been evaluated as catalysts in the synthesis of propargylamines by a three‐component coupling reaction of aldehydes, amines, and alkynes in water. The antimicrobial activity of the new complexes against gram‐positive and gram‐negative bacteria and yeast has been evaluated. The new compounds display moderate to high antibacterial activity. The more lipophilic compounds are also potent against fungi. Their cytotoxic properties have been analyzed in vitro by utilizing human Jurkat T‐cell acute lymphoblastic leukemia cells. Compounds with dialkyl‐(m‐sulfonated‐phenyl) (mC6H4SO3Na) phosphanes displayed moderate to high cytotoxicity on this cell line. The cell death mechanism involves mainly early apoptosis. The catalytic/biological activity of the previously described compound with commercial m‐trisulfonated‐triphenylphosphane [AuCl(TPPTS)] (6) has also been evaluated to compare the effects of the higher basicity and lipophilicity of the alkyl‐ and dialkyl‐(m‐sulfonated‐phenyl)phosphanes on these new compounds. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Chiral Lewis Base Catalyzed Enantioselective Acetylcyanation of α‐Oxo Esters
Authors: Li Fei , Widyan Khalid , Wingstrand Erica , Moberg Christina 
Published: June 2009

AbstractAcetyl cyanide adds to alkyl benzoylformates and to 2‐oxoalkanoates to yield enantioenriched acylated cyanohydrins in one step in the presence of a catalytic amount of a chiral base. The reaction is accelerated by Lewis acids and by the addition of a catalytic amount of methanol. Under optimized conditions, 94 % of a 94:6 mixture of the O‐acetylated and non‐protected cyanohydrins was formed from methyl benzoylformate in the presence of cinchonidine; from this mixture the acylated compound with 66 % ee was isolated in 77 % yield. Ethyl pyruvate and tert‐butyl 2‐oxobutanoate were more reactive, and essentially full conversion to the products with 69 and 82 % ee, respectively, was achieved. The reaction proceeds by a non‐selective addition of cyanide ion to give the non‐protected cyanohydrin followed by a dynamic kinetic resolution to provide the enantioenriched acetylated product. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
The Influence of Different Spacer Lengths on the Selectivity of Self‐Assembly Processes of Bis(bipyridine)‐BINOL Helicates
Authors: Bunzen Jens , Hapke Marko , Lützen Arne 
Published: June 2009

AbstractThe synthesis and self‐assembly behaviour of a series of enantiomerically pure bis(chelating) ligands is reported. The ligands differ in the spacer unit between a BINOL core and two bipyridyl groups as the chelating entities and were found to undergo completely diastereoselective self‐assembly to dinuclear double‐stranded helicates with silver(I) salts, as demonstrated by NMR and CD spectroscopy and ESI mass spectrometry. Upon coordination to iron(II) or zinc(II) ions, however, a dramatic loss in the diastereoselectivity of the self‐assembly of dinuclear triple‐stranded helicates was observed as a result of increasing spacer length. In the case of zinc(II), the self‐assembly processes were even found to be nonselective with regard to the composition of the helicates.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Efficient Synthesis of Hybrid (Hydroquinone–Schiff base)cobalt Oxidation Catalysts
Authors: Johnston Eric V. , Karlsson Erik A. , Tran Lien‐Hoa , Åkermark Björn , Bäckvall Jan‐E. 
Published: June 2009

AbstractHybrid catalysts A and B have recently been found to efficiently transfer electrons from a metal catalyst to molecular oxygen in biomimetic oxidations. In the present work hybrid catalysts A and B were synthesized in high yield from inexpensive starting materials. The key step is an efficient Suzuki cross‐coupling, which allows the use of unprotected aldehyde 5. The new synthesis of the title hybrid catalysts is easy to carry out and can be scaled up. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Natural Product Synthesis Featuring Intramolecular Diels–Alder Approaches – Total Syntheses of Tubelactomicins and Spiculoic Acid A
Authors: Tadano Kin‐ichi 
Published: June 2009

AbstractWe have recently accomplished the total syntheses of the antimicrobial tricyclic 16‐membered macrolides (+)‐tubelactomicin A, B, D, and E by common synthetic approaches based on intramolecular Diels–Alder (IMDA) reactions. These total syntheses established the relative and absolute configurations of three antibiotics – (+)‐tubelactomicins B, D, and E – for which only planar structures had been previously reported. In addition, we have very recently accomplished the total synthesis of a marine natural product, (+)‐spiculoic acid A, by an IMDA strategy. This Microreview summarizes our total syntheses of the four tubelactomicns and the total synthesis of (+)‐tubelactomicin A by Tatsuta et al. Both approaches were based on the use of stereoselective IMDA reactions for the construction of the lower‐half segments of the antibiotics. Total syntheses of the unnatural (–) and natural (+) enantiomers of spiculoic acid A, the former achieved by Baldwin and Lee's group and the latter achieved by the author's group, are also summarized. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Reaction of the Electrogenerated Cyanomethyl Anion with Carbonyl Compounds: A Clean and Safe Synthesis of β‐Hydroxynitriles
Authors: Bianchi Gabriele , Feroci Marta , Rossi Leucio 
Published: June 2009

AbstractThe electrogenerated cyanomethyl anion reacts with carbonyl compounds to yield the corresponding β‐hydroxynitriles in moderate to high yields. The reported methodology is very clean and safe, avoiding the use of any classical base or catalyst. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Assay of bradykinin metabolites in human body fluids by CE‐LIF coupled with transient ITP preconcentration
Authors: Chen Ying , Zhang Lan , Xu Liangjun , Lin Jin‐Ming , Chen Guonan 
Published: June 2009

AbstractA CE with LIF detection was developed for the separation and determination of three bradykinin (BK) metabolites: BK2‐9, BK1‐7 and BK1‐5. BK fragments were derivatized with 5‐(4, 6‐dichloro‐s‐triazin‐2‐ylamino) fluorescein before CE‐LIF analysis. Eighty millimolar of Tris‐H3PO4 (pH 9.0) was selected as the derivatization media. Three BK fragments were baseline separated within 10 min by using 0.2 M TAPS‐Tris buffer (pH 8.5) as the running buffer. Meanwhile we have also developed a simple, quick, and sensitive on‐column transient ITP preconcentration for CE‐LIF detection of three BK fragments. Ten millimolar of Tris‐HCl (pH 9.0) was chosen as the leading electrolyte and 0.2 M TAPS‐Tris (pH 8.5) containing 10 mM 1‐butyl‐3‐methylimidazolium tetrafluoroborate as the terminating electrolyte and also served as the running buffer during CZE separation. By using this transient ITP coupled with CE‐LIF, concentration detection limits (S/N=3) for BK2‐9, BK1‐7 and BK1‐5 were 0.3, 0.1 and 0.1 pmol/L, respectively. This method has been applied to the assay of human saliva and plasma samples with satisfactory results.
Chiral ligand‐exchange CE assays for separation of amino acid enantiomers and determination of enzyme kinetic constant
Authors: Qi Li , Qiao Juan , Yang Gengliang , Chen Yi 
Published: June 2009

AbstractThis paper deals with studies on the use of Zn(II)‐L‐ornithine complex as a chiral selecting system for the enantioseparation and UV detection of amino acids (AAs) by using the principle of ligand‐exchange CE. Successful enantioseparation of three pairs of label‐free aromatic AAs and four pairs of labeled AA enantiomers have been achieved with a buffer of 100.0 mM boric acid, 5.0 mM ammonium acetate, 3.0 mM ZnSO4and 6.0 mML‐Orn at pH 8.2. This new method was shown to be applicable to the quantitative analysis ofD‐ andL‐aromatic AAs, with a linear range between 12.5 and 800.0 μg/mL, and a correlation coefficient above 0.99. Thus this assay, which is facile and relatively rapid, allows us to measure the enzyme catalytic activity in the incubation ofD,L‐AAs withD‐AA oxidase. Using this new method, we can determine the enzyme kinetic constant, lending insight into potential enzyme mechanism.
Hydroxyethylcellulose‐graft‐poly (4‐vinylpyridine) as a novel, adsorbed coating for protein separation by CE
Authors: Yang Runmiao , Liu Yuhai , Wang Yanmei 
Published: June 2009

AbstractA novel graft copolymer, hydroxyethylcellulose‐graft‐poly (4‐vinylpyridine), used as a physically adsorbed coating of the fused‐silica (FS) capillaries, was synthesized by using ceric ammonium nitrate initiator in aqueous nitric acid solution. EOF measurements showed that the above graft copolymer coating of the FS capillaries could suppress EOF effectively compared with the bare FS capillaries. The adsorbed coating exhibited minimal interactions with proteins, providing efficient protein separations with excellent repeatability. Interestingly, the electrical charge of the coated capillary wall could be modulated by varying the pH of the running buffer, which makes possible the analysis of basic and acidic proteins in the same capillary. The effects of pH on suppressing EOF and protein separation were investigated in detail. The results demonstrated that the hydroxyethylcellulose‐graft‐poly (4‐vinylpyridine) copolymer coatings have great potential in the diagnosis and proteomics.
Rayleigh time‐varying channel complex gains estimation and ICI cancellation in OFDM systems
Authors: Hijazi Hussein , Ros Laurent 
Published: June 2009

AbstractIn this paper, we consider an orthogonal frequency division multiplexing (OFDM) mobile communication system operating in downlink mode in a time‐varying multipath Rayleigh channel scenario. We present a mean square error (MSE) theoretical analysis for a multipath channel complex gains estimation algorithm with inter‐sub‐carrier interference (ICI) reduction using a comb‐type pilot. Assuming the presence of delay‐related information, the time average of the multipath complex gains, over the effective duration of each OFDM symbol, are estimated using LS criterion. After that, the time‐variation of the multipath complex gains within one OFDM symbol are obtained by interpolating the time‐averaged symbol values using low‐pass interpolation. Hence, the channel matrix, which contains the channel frequency response and the coefficients of ICI, can be computed and the ICI can be reduced by using successive interference suppression (SIS) in data symbol detection. The algorithm's performance is further enhanced by an iterative procedure, performing channel estimation and ICI suppression at each iteration. Theoretical analysis and simulation results show a significant performance improvement for high normalised Doppler spread (especially after the first iteration) in comparison to conventional methods. Copyright © 2009 John Wiley & Sons, Ltd.
The variance ratio and trend stationary model as extensions of a constrained autoregressive model
Authors: Zilca Shlomo 
Published: June 2009

AbstractThis paper shows that a constrained autoregressive model that assigns linearly decreasing weights to past observations of a stationary time series has important links to the variance ratio methodology and trend stationary model. It is demonstrated that the proposed autoregressive model is asymptotically related to the variance ratio through the weighting schedules that these two tools use. It is also demonstrated that under a trend stationary time series process the proposed autoregressive model approaches a trend stationary model when the memory of the autoregressive model is increased. These links create a theoretical foundation for tests that confront the random walk model simultaneously against a trend stationary and a variety of short‐ and long‐memory autoregressive alternatives. Copyright © 2009 John Wiley & Sons, Ltd.
The geochemical characterization and correlation of Late Holocene tephra layers at Ambra Crater and Kuk Swamp, Papua New Guinea
Authors: Coulter Sarah E. , Denham Tim P. , Turney Chris S. M. , Hall Valerie A. 
Published: June 2009

AbstractMajor element geochemical analyses of volcanic glass shards from visible, macroscopic tephra layers in Papua New Guinea were used to test field‐based correlations between local Late Holocene sequences. Previously, synchronization of sediment records at archaeological and palaeoecological sites across the Papua New Guinea highlands had been based largely on the physical properties and stratigraphic relationships of visible volcanic layers. The geochemical analysis of tephra‐derived glass demonstrates miscorrelations and enables more robust tephrostratigraphic links to be made between a globally significant archaeological site, Kuk Swamp, and a nearby volcanic cone, Ambra Crater. The results indicate that field‐based correlations of tephras can be problematic, especially given variable post‐depositional changes in colour and texture of relatively thin tephra layers in different depositional environments. Additionally, the findings call into question some previous tephrochronological associations at archaeological and palaeoecological sites in the Papua New Guinea highlands, and demonstrate the necessity of grain‐discrete geochemical analysis of glass shards as a basis for future tephrochronological studies in this region. Copyright © 2009 John Wiley & Sons, Ltd.
Functional and anatomical connectivity abnormalities in left inferior frontal gyrus in schizophrenia
Authors: Jeong Bumseok , Wible Cynthia G. , Hashimoto Ryu‐Ichiro , Kubicki Marek 
Published: June 2009

AbstractFunctional studies in schizophrenia demonstrate prominent abnormalities within the left inferior frontal gyrus (IFG) and also suggest the functional connectivity abnormalities in language network including left IFG and superior temporal gyrus during semantic processing. White matter connections between regions involved in the semantic network have also been indicated in schizophrenia. However, an association between functional and anatomical connectivity disruptions within the semantic network in schizophrenia has not been established. Functional (using levels of processing paradigm) as well as diffusion tensor imaging data from 10 controls and 10 chronic schizophrenics were acquired and analyzed. First, semantic encoding specific activation was estimated, showing decreased activation within the left IFG in schizophrenia. Second, functional time series were extracted from this area, and left IFG specific functional connectivity maps were produced for each subject. In an independent analysis, tract‐based spatial statistics (TBSS) was used to compare fractional anisotropy (FA) values between groups, and to correlate these values with functional connectivity maps. Schizophrenia patients showed weaker functional connectivity within the language network that includes left IFG and left superior temporal sulcus/middle temporal gyrus. FA was reduced in several white matter regions including left inferior frontal and left internal capsule. Finally, left inferior frontal white matter FA was positively correlated with connectivity measures of the semantic network in schizophrenics, but not in controls. Our results indicate an association between anatomical and functional connectivity abnormalities within the semantic network in schizophrenia, suggesting further that the functional abnormalities observed in this disorder might be directly related to white matter disruptions. Hum Brain Mapp, 2009. © 2009 Wiley‐Liss, Inc.
Mapping the pathways of information processing from sensation to action in four distinct sensorimotor tasks
Authors: Ivanoff Jason , Branning Philip , Marois René 
Published: June 2009

AbstractTwo sensorimotor tasks that share neither sensory nor motor modality can interfere with one another when they are performed simultaneously. A possible cause for this interference is the recruitment of common brain regions by these two tasks, thereby creating a bottleneck of information processing. This hypothesis predicts that such “bottleneck” regions would be activated by each task even when they are performed separately. To test this prediction, we sought to identify, with fMRI, brain regions commonly activated by sensorimotor tasks that share neither sensory input nor motor output. One group of subjects was scanned while they performed in separate runs an auditory‐vocal (AVo) task and a visuo‐manual (ViM) task, while a second group of subjects performed the reversed sensorimotor mapping tasks (AM and ViVo). The results revealed strong activation preferences in specific sensory and motor cortical areas for each sensory and motor modality. By contrast, the posterior portion of the lateral prefrontal cortex (pLPFC), anterior insula, and, less consistently, the anterior cingulate, presupplementary and supplementary motor areas, and subcortical areas were commonly activated across all four sensorimotor tasks. These results were observed in both blocked and event‐related fMRI designs, in both 3D‐group averaged and 2D‐individual subject analyses, and were replicated within individuals across scanning sessions. These findings not only suggest that these brain regions serve a common amodal function in sensorimotor tasks, they also point to these regions—particularly, the pLPFC and anterior insula—as candidate neural substrates underlying a central hub of information processing in the human brain. Hum Brain Mapp, 2009. © 2009 Wiley‐Liss, Inc.
Neither one‐time negative screening tests nor negative colposcopy provides absolute reassurance against cervical cancer
Authors: Castle Philip E. , Rodríguez Ana C. , Burk Robert D. , Herrero Rolando , Hildesheim Allan , Solomon Diane , Sherman Mark E. , Jeronimo Jose , Alfaro Mario , Morales Jorge , Guillén Diego , Hutchinson Martha L. , Wacholder Sholom , Schiffman Mark 
Published: June 2009

AbstractA population sample of 10,049 women living in Guanacaste, Costa Rica, was recruited into a natural history of human papillomavirus (HPV) and cervical neoplasia study in 1993–1994. At the enrollment visit, we applied multiple state‐of‐the‐art cervical cancer screening methods to detect prevalent cervical cancer and to prevent subsequent cervical cancers by the timely detection and treatment of precancerous lesions. Women were screened at enrollment with 3 kinds of cytology (often reviewed by more than one pathologist), visual inspection and cervicography. Any positive screening test led to colposcopic referral and biopsy and/or excisional treatment of CIN2 or worse. We retrospectively tested stored specimens with an early HPV test (hybrid capture tube test) and for >40 HPV genotypes using a research PCR assay. We followed women typically 5–7 years and some up to 11 years. Nonetheless, 16 cases of invasive cervical cancer were diagnosed during follow‐up. Six cancer cases were failures at enrollment to detect abnormalities by cytology screening; 3 of the 6 were also negative at enrollment by sensitive HPV DNA testing. Seven cancers represent failures of colposcopy to diagnose cancer or a precancerous lesion in screen‐positive women. Finally, 3 cases arose despite attempted excisional treatment of precancerous lesions. Based on this evidence, we suggest that no current secondary cervical cancer prevention technologies applied once in a previously under‐screened population is likely to be 100% efficacious in preventing incident diagnoses of invasive cervical cancer. © 2009 UICC