bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unexpected Differences in the Coordination Behaviour of 1,2,4‐Triphosphaferrocenes towards CuIChloride
Authors: Deng Shining , Schwarzmaier Christoph , Vogel Ulf , Zabel Manfred , Nixon John F. , Scheer Manfred 
Published: September 2008

AbstractThe coordination behaviour of 1,2,4‐triphosphaferrocenes [FeCpR(η5‐P3C2tBu2)] [CpR= Cp (1), Cp″′ (2)] towards CuIchloride is significantly influenced by the substitution pattern of the cyclopentadienyl ring attached to iron. The dimeric copper complexes [{FeCp(η5:η1:η1‐P3tBu2C2)}{μ‐CuCl(MeCN)}]2(3) and [{FeCp″′ (η5:η1:η1‐P3tBu2C2)}(μ‐CuCl)]2(4), in which two 1,2,4‐triphosphaferrocenes are linked by two CuCl centres to form dimeric complexes were obtained in reactions using a 1:1 stoichiometry. Whereas in3a tetra‐coordinated Cu atom is revealed,4possesses a threefold‐coordinated Cu atom due to the steric influence of the bulkier Cp″′ ligand. However, if the reaction is carried out with an excess of CuCl in a 1:2 stoichiometry for the Cp derivative1the same product3is obtained, whereas in the case of a tri‐tert‐butyl‐substituted Cp″′ ligand complex2the triphospholyl ring is fragmented under mild conditions to a tetraphosphabutadiene moiety within an iron triple‐decker sandwich complex [{(FeCp″′)2(μ,η4:η4:η1:η1‐P4)}{μ‐CuCl(MeCN)}]∞(5) embedded in a CuCl polymer matrix.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Alcoholysis of Phosphaisocoumarins and Synthesis of 2‐(2‐Oxoalkyl)phenylphosphonates
Authors: Peng Ai‐Yun , Guo Yu‐Juan , Ke Zhi‐Hai , Zhu Shizheng 
Published: September 2008

AbstractPhosphaisocoumarins do not undergo aminolysis, but instead they were found to be susceptible to alcoholysis in the presence of alcohols and primary amines. This paper examined this unexpected alcoholysis reaction and found that in the presence of Et3N or K2CO3, 4‐unsubstituted‐ and 4‐chlorophosphaisocoumarins underwent the alcoholysis reaction smoothly to give a series of 2‐(2‐oxoalkyl)phenylphosphonates in good yields, whereas 4‐iodo‐ and 4‐bromophosphaisocoumarins underwent a dehalogenation–alcoholysis tandem reaction. The possible mechanism for the alcoholysis reaction was discussed. In addition, direct access to 2‐(2‐oxoalkyl)phenylphosphonates was developed by the mercury(II)‐catalyzed hydration of 2‐(1‐alkynly)phenylphosphonates with high regioselectivity. In a preliminary study, the obtained novel keto phosphonates showed medium inhibitory activity towards α‐chymotrypsin. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Real‐time or current vintage: does the type of data matter for forecasting and model selection?
Authors: Feng Hui 
Published: September 2008

AbstractIn this paper we investigate the impact of data revisions on forecasting and model selection procedures. A linear ARMA model and nonlinear SETAR model are considered in this study. Two Canadian macroeconomic time series have been analyzed: the real‐time monetary aggregate M3 (1977–2000) and residential mortgage credit (1975–1998). The forecasting method we use is multi‐step‐ahead non‐adaptive forecasting. Copyright © 2008 John Wiley & Sons, Ltd.
Topographic analysis of individual activation patterns in medial frontal cortex in schizophrenia
Authors: Stern Emily R. , Welsh Robert C. , Fitzgerald Kate D. , Taylor Stephan F. 
Published: September 2008

AbstractIndividual variability in the location of neural activations poses a unique problem for neuroimaging studies employing group averaging techniques to investigate the neural bases of cognitive and emotional functions. This may be especially challenging for studies examining patient groups, which often have limited sample sizes and increased intersubject variability. In particular, medial frontal cortex (MFC) dysfunction is thought to underlie performance monitoring dysfunction among patients with schizophrenia, yet previous studies using group averaging to compare schizophrenic patients to controls have yielded conflicting results. To examine individual activations in MFC associated with two aspects of performance monitoring, interference and error processing, functional magnetic resonance imaging data were acquired while 17 patients with schizophrenia and 21 healthy controls (HCs) performed an event‐related version of the multisource interference task. Comparisons of averaged data revealed few differences between the groups. By contrast, topographic analysis of individual activations for errors showed that control subjects exhibited activations spanning across both posterior and anterior regions of MFC while patients primarily activated posterior MFC, possibly reflecting an impaired emotional response to errors in schizophrenia. This discrepancy between topographic and group‐averaged results may be due to the significant dispersion among individual activations, particularly in HCs, highlighting the importance of considering intersubject variability when interpreting the medial frontal response to error commission. Hum Brain Mapp, 2009. © 2008 Wiley‐Liss, Inc.
Brain activity during visual versus kinesthetic imagery: An fMRI study
Authors: Guillot Aymeric , Collet Christian , Nguyen Vo An , Malouin Francine , Richards Carol , Doyon Julien 
Published: September 2008

AbstractAlthough there is ample evidence that motor imagery activates similar cerebral regions to those solicited during actual movements, it is still unknown whether visual (VI) and kinesthetic imagery (KI) recruit comparable or distinct neural networks. The present study was thus designed to identify, through functional magnetic resonance imaging at 3.0 Tesla in 13 skilled imagers, the cerebral structures implicated in VI and KI. Participants were scanned in a perceptual control condition and while physically executing or focusing during motor imagery on either the visual or kinesthetic components of an explicitly known sequence of finger movements. Subjects' imagery abilities were assessed using well‐established psychological, chronometric, and new physiological measures from the autonomic nervous system. Compared with the perceptual condition, physical executing, VI, and KI resulted in overlapping (albeit non‐identical) brain activations, including motor‐related regions and the inferior and superior parietal lobules. By contrast, a divergent pattern of increased activity was observed when VI and KI were compared directly: VI activated predominantly the occipital regions and the superior parietal lobules, whereas KI yielded more activity in motor‐associated structures and the inferior parietal lobule. These results suggest that VI and KI are mediated through separate neural systems, which contribute differently during processes of motor learning and neurological rehabilitation. Hum Brain Mapp, 2009. © 2008 Wiley‐Liss, Inc.
Time to stop ovarian cancer screening in BRCA1/2 mutation carriers?
Authors: van der Velde Nienke M. , Mourits Marian J.E. , Arts Henriëtte J.G. , de Vries Jacob , Leegte Beike K. , Dijkhuis Grieteke , Oosterwijk Jan C. , de Bock Geertruida H. 
Published: September 2008

AbstractWomen at high risk of ovarian cancer due to a genetic predisposition may opt for either surveillance or prophylactic bilateral salpingo‐oophorectomy (pBSO). Main objective of our study was to determine the effectiveness of ovarian cancer screening in women with a BRCA1/2 mutation. We evaluated 241 consecutive women with a BRCA1 or BRCA2 mutation who were enrolled in the surveillance program for hereditary ovarian cancer from September 1995 until May 2006 at the University Medical Center Groningen (UMCG), The Netherlands. The ovarian cancer screening included annual pelvic examination, transvaginal ultrasound (TVU) and serum CA125 measurement. To evaluate the effectiveness of screening in diagnosing (early stage) ovarian cancer sensitivity, specificity, positive and negative predictive values (PPV and NPV) of pelvic examination, TVU and CA125 were calculated. Three ovarian cancers were detected during the surveillance period; 1 prevalent cancer, 1 interval cancer and 1 screen‐detected cancer, all in an advanced stage (FIGO stage IIIc). A PPV of 20% was achieved for pelvic examination, 33% for TVU and 6% for CA125 estimation alone. The NPV were 99.4% for pelvic examination, 99.5% for TVU and 99.4% for CA125. All detected ovarian cancers were in an advanced stage, and sensitivities and positive predictive values of the screening modalities are low. Restricting the analyses to incident contacts that contained all 3 screening modalities did not substantially change the outcomes. Annual gynecological screening of women with a BRCA1/2 mutation to prevent advanced stage ovarian cancer is not effective. © 2008 Wiley‐Liss, Inc.
Endothelial function in patients with and without diabetes mellitus with different degrees of coronary artery stenosis
Authors: Simova Iana I. , Denchev Stefan V. , Dimitrov Simeon I. , Ivanova Raia 
Published: September 2008

AbstractPurpose.To evaluate endothelial function using flow‐mediated dilatation (FMD) of the brachial artery in patients with and without diabetes mellitus (DM) with different degrees of coronary artery stenosis.Method.We investigated 293 patients, 69 (23.6%) of whom had DM. FMD and coronary arteriography were performed.Results.Patients with DM had a significantly lower FMD (mean ± SD, 3.7 ± 3.8%) compared with patients without DM (mean ± SD, 5.2 ± 5.3%) (p < 0.05). When the results were broken down by the severity of coronary artery disease (CAD) (no significant coronary artery stenosis, 1‐vessel disease, 2‐vessel disease, and 3‐vessel disease) the only statistically significant difference between diabetics and nondiabetics was found in patients without significant coronary stenosis (mean FMD ± SD: 5.2 ± 4.4% in diabetics, 7.6 ± 5.4% in nondiabetics [p < 0.05]).Conclusion.In CAD patients, the presence of DM was associated with endothelial dysfunction. The difference in the FMD was clearly expressed between patients with and without DM in the subgroup without significant coronary stenosis, and was no longer present with advanced coronary atherosclerosis. © 2008 Wiley Periodicals, Inc. J Clin Ultrasound, 2009
A local structure theorem on 5‐connected graphs
Authors: Ando Kiyoshi 
Published: September 2008

AbstractAn edge of a 5‐connected graph is said to be contractible if the contraction of the edge results in a 5‐connected graph. Let x be a vertex of a 5‐connected graph. We prove that if there are no contractible edges whose distance from x is two or less, then either there are two triangles with x in common each of which has a distinct degree five vertex other than x, or there is a specified structure called a K4−‐configuration with center x. As a corollary, we show that if a 5‐connected graph on n vertices has no contractible edges, then it has 2n/5 vertices of degree 5. © 2008 Wiley Periodicals, Inc. J Graph Theory 60: 99–129, 2009
Terminal Modification with 1‐Adamantylamine to Endow Hyperbranched Polyamidoamine with Thermo‐/pH‐Responsive Properties
Authors: Guo Zhe , Zhang Yongwen , Huang Wei , Zhou Yongfeng , Yan Deyue 
Published: September 2008

AbstractA novel terminal modification agent to endow hyperbranched polyamidoamine (HPAMAM) with thermo‐/pH‐responsive properties is reported. HPAMAM with terminal vinyl groups is first synthesized and then end‐capped by 1‐adamantylamine (ADA). The resulting hyperbranched polymer (HPAMAM‐ADA) shows interesting thermo‐responsive properties in aqueous solution, which have been investigated by UV‐vis spectroscopy, optical microscopy, and 1H NMR spectroscopy. The lower critical solution temperature can be controlled by adjusting the end‐capping ratio of ADA. In addition, HPAMAM‐ADA exhibits a pH‐dependent water solubility. This pH‐responsive behavior is also studied.magnified image
Effects of MgCl2 Crystallographic Structure on Active Centre Formation in Immobilized Single‐Centre and Ziegler–Natta Catalysts for Ethylene Polymerization
Authors: Huang Rubin , Malizia Federica , Pennini Gianni , Koning Cor E. , Chadwick John C. 
Published: September 2008

AbstractThe ability of a MgCl2 support to activate a transition metal catalyst has been found to depend both on the crystallographic structure of the support and on the nature of the catalyst. A high degree of crystallographic disorder can be very effective for the immobilization and activation of titanium and vanadium complexes, but is not necessarily effective for zirconocene activation. A highly disordered support prepared by the reaction of MgBu2 with HCl gave high activity with TiCl4 but low activity with (n‐PrCp)2ZrCl2. High polymerization activities with the zirconocene were only obtained with supports of type MgCl2/AlRn(OEt)3−n prepared from the reaction of AlR3 with MgCl2 · 1.1EtOH. These supports are characterized by additional peaks in the X‐ray diffraction pattern, indicating the presence of a crystalline structure which is absent in the other supports and contains highly Lewis acidic sites able to generate the active metallocenium species.magnified image
Novel Luminescent Electrospun Fibers Prepared From Conjugated Rod–Coil Block Copolymer of Poly[2,7‐(9,9‐dihexylfluorene)]‐block‐Poly(methyl methacrylate)
Authors: Kuo Chi‐Ching , Tung Yi‐Chih , Lin Chia‐Hung , Chen Wen‐Chang 
Published: September 2008

AbstractNovel luminescent electrospun (ES) fibers have been successfully prepared from a conjugated rod–coil block copolymer, poly[2,7‐(9,9‐dihexylfluorene)]‐block‐poly(methyl methacrylate) (PF‐b‐PMMA) using a single‐capillary spinneret. Experiment results indicate that PF‐b‐PMMA ES fibers prepared from THF, THF/DMF (50/50), and DMF contain PF block aggregated structures of dot‐like (5–10 nm), line‐like (10–20 nm), and ellipse‐like structure (25–50 nm), respectively. Such variation of aggregation size leads to a red‐shift of the absorption or luminescence spectra. In addition, the fiber diameters decrease upon enhancing the DMF content. The present study demonstrates that blue light‐emitting ES fibers are successfully prepared from conjugated rod–coil diblock copolymers and their aggregate morphology and photophysical properties could be tuned through use of selective solvent.magnified image
An Original Calix[4]arene‐Containing Oligomer/Polymer Catalyst for Homogeneous Hydroformylation
Authors: Mongrain Pascal , Harvey Pierre D. 
Published: September 2008

AbstractThe title compound (10) was prepared from the calix[4]arene precursor (11) to form the ligand 5,11‐bis(methyl(diphenylphosphino))‐25,26,27,28‐tetra‐n‐propoxy calix[4]arene (12), which was reacted with [Rh(COD)Cl]2 (COD = 1,5‐cyclooctadienyl) and TlPF6 as chloride scavenger, in 31% overall chemical yield. The dimer structure in solution was demonstrated by the measurements of the 31P NMR spin‐lattice relaxation time (T1) in comparison with the ligand itself. Computer modeling shows that the dimer macrocycle exhibits many possible conformers, including some with obvious steric hindrance about the Rh atom, but no apparent ring stress. 10 was tested for the catalytic homogeneous hydroformylation of hex‐1‐ene and compared with other closely related analogue systems recently reported in the literature.magnified image
Comparative reliability of proton spectroscopy techniques designed to improve detection of J‐coupled metabolites
Authors: Mullins Paul Gerald , Chen Hongji , Xu Jing , Caprihan Arvind , Gasparovic Charles 
Published: September 2008

AbstractImproved detection of J‐coupled neurometabolites through the use of modified proton magnetic resonance spectroscopy (1H‐MRS) techniques has recently been reported. TE‐averaged point‐resolved spectroscopy (PRESS) uses the J modulation effects by averaging FIDs with differing echo times to improve detection of glutamate, while standard PRESS detection of glutamate can be improved by using an appropriate single echo determined from J‐modulation simulations. In the present study, the reliabilities of TE‐averaged PRESS, standard PRESS with TE = 40 ms, and standard PRESS with TE = 30 ms in detecting metabolite levels in the cingulate gyrus of the human brain at 3T were compared in six subjects. TE‐averaged PRESS measures showed a mean variability of 9% for N‐acetyl aspartate, choline, and creatine, compared with < 4% for the 30‐ and 40‐ms PRESS techniques. The coefficients of variation for glutamate were 10%, 7%, and 5% for TE‐averaged, 30‐ms, and 40‐ms PRESS, respectively. PRESS with a TE of 40 ms also demonstrated improved reliability for GABA and glutamine concentrations. These results show that with the appropriate selection of echo time standard PRESS can be a reliable 1H‐MRS technique for the measurement of J‐coupled neurometabolites in the human brain and, moreover, compares favorably with at least one J‐edited technique. Magn Reson Med 60:964–969, 2008. © 2008 Wiley‐Liss, Inc.
Three‐frequency RF coil designed for optimized imaging of hyperpolarized, 13C‐labeled compounds
Authors: Hancu Ileana , Wood S. James , Piel Joseph , Whitt David B. , Fish Kenneth M. , Rutt Brian K. , Tropp James , Dixon W. Thomas 
Published: September 2008

AbstractImaging exams involving hyperpolarized, 13C‐labeled compounds require novel RF coils for efficient signal utilization. While 13C coils are required for mapping the spatial distribution of the hyperpolarized compounds, imaging/pulsing at different frequencies is also needed for scan setup steps prior to the image acquisition. Imaging/pulsing at the 1H frequency is typically used for anatomical localization and shimming. Flip angle (FA) calibration, which is difficult or impossible to achieve at the 13C frequency, can be accurately performed at the 23Na frequency using the natural abundance signal that exists in any living tissue. We demonstrate here a single RF resonant structure that is capable of operating linearly at the 1H and 23Na frequencies for scan setup steps, and in quadrature at the 13C frequency for imaging. Images at the three resonant frequencies of this coil are presented from an exam involving hyperpolarized 13C compounds in vivo. Magn Reson Med 60:928–933, 2008. © 2008 Wiley‐Liss, Inc.
Effects of image noise in muscle diffusion tensor (DT)‐MRI assessed using numerical simulations
Authors: Damon Bruce M. 
Published: September 2008

AbstractDiffusion tensor (DT)‐MRI studies of skeletal muscle provide information about muscle architecture, microstructure, and damage. However, the effects of noise, the diffusion weighting (b)‐value, and partial volume artifacts on the estimation of the diffusion tensor (D) are unknown. This study investigated these issues using Monte Carlo simulations of 3 × 9 voxel regions of interest (ROIs) containing muscle, adipose tissue, and intermediate degrees of muscle volume fractions (fM). A total of 1000 simulations were performed for each of eight b‐values and 11 SNR levels. The dependencies of the eigenvalues (λ1–3), mean diffusivity (λ), and fractional anisotropy (FA), and the angular deviation of the first eigenvector from its true value (α) were observed. For moderate b‐values (b = 435–725 s/mm2) and fM = 1, an accuracy of 5% was obtained for λ1–3, λ, and FA with an SNR of 25. An accuracy of 1% was obtained for λ1–3, λ, and FA with fM = 1 and SNR = 50. For regions with fM = 8/9, 5% accuracy was obtained with SNR = 40. For α, SNRs of ≥25 and ≥45 were required for ±4.5° uncertainty with fM = 1 and fM = 0.5, respectively; SNR ≥ 60 was required for ±9° uncertainty in single muscle voxels. These findings may influence the design and interpretation of DT‐MRI studies of muscle microstructure, damage, and architecture. Magn Reson Med 60:934–944, 2008. © 2008 Wiley‐Liss, Inc.
Myoinositol content in the human brain is modified by transcranial direct current stimulation in a matter of minutes: A 1H‐MRS study
Authors: Rango M. , Cogiamanian F. , Marceglia S. , Barberis B. , Arighi A. , Biondetti P. , Priori A. 
Published: September 2008

AbstractBrain content of myoinositol (mI) has been shown to be altered in several neuropsychiatric conditions. Likewise, various forms of electric currents have been applied to the human brain for therapeutic purposes in neuropsychiatric diseases. In this study we aimed to depict the effects of low‐power transcranial direct current stimulation (tDCS) on brain mI by proton magnetic resonance spectroscopy (1H‐MRS). We studied two groups of five healthy subjects by 1H‐MRS: the first group was studied before and after both anodal and sham (placebo) tDCS over the right frontal lobe, and the second group was studied at the same intervals without undergoing either sham or anodal tDCS. Anodal tDCS induced a significant increase of mI content at 30 min after stimulation offset (141.5 ± 16.7%, P < 0.001) below the stimulating electrode but not in distant regions, such as the visual cortex, whereas sham tDCS failed to induce changes in mI. Neither N‐acetyl‐aspartate (NAA) nor the other metabolite contents changed after anodal or sham stimulation. 1H‐MRS represents a powerful tool to follow the regional effects of tDCS on brain mI and, possibly, on the related phosphoinositide system. Magn Reson Med 60:782–789, 2008. © 2008 Wiley‐Liss, Inc.
Quantitative MR susceptibility mapping using piece‐wise constant regularized inversion of the magnetic field
Authors: de Rochefort Ludovic , Brown Ryan , Prince Martin R. , Wang Yi 
Published: September 2008

AbstractMagnetic properties characterized by susceptibility and chemical shift linearly modify the local magnetic field experienced by spins. A piece‐wise constant solution using magnetic resonance imaging is found to the challenging inversion problem from field to magnetic properties. The magnetic field shifts were estimated from MR phase images. The MR magnitude images were segmented into many regions of uniform magnetic properties. Standard linear regression using the calculated magnetic field from each region allowed accurate susceptibility quantification. The technique was experimentally validated on a variety of samples including water, vegetable oil, air, Gadolinium, and superparamagnetic iron oxides. Susceptibility was measured with a precision better than 0.1 ppm, in a range of 10 ppm. In vivo feasibility was shown on the forearm for which soft‐tissue, cortical bone, and bone marrow susceptibility, and chemical shift values in good agreement with literature data were obtained. Magn Reson Med 60:1003–1009, 2008. © 2008 Wiley‐Liss, Inc.
Practical data acquisition method for human brain tumor amide proton transfer (APT) imaging
Authors: Zhou Jinyuan , Blakeley Jaishri O. , Hua Jun , Kim Mina , Laterra John , Pomper Martin G. , van Zijl Peter C.M. 
Published: September 2008

AbstractAmide proton transfer (APT) imaging is a type of chemical exchange–dependent saturation transfer (CEST) magnetic resonance imaging (MRI) in which amide protons of endogenous mobile proteins and peptides in tissue are detected. Initial studies have shown promising results for distinguishing tumor from surrounding brain in patients, but these data were hampered by magnetic field inhomogeneity and a low signal‐to‐noise ratio (SNR). Here a practical six‐offset APT data acquisition scheme is presented that, together with a separately acquired CEST spectrum, can provide B0‐inhomogeneity corrected human brain APT images of sufficient SNR within a clinically relevant time frame. Data from nine brain tumor patients at 3T shows that APT intensities were significantly higher in the tumor core, as assigned by gadolinium‐enhancement, than in contralateral normal‐appearing white matter (CNAWM) in patients with high‐grade tumors. Conversely, APT intensities in tumor were indistinguishable from CNAWM in patients with low‐grade tumors. In high‐grade tumors, regions of increased APT extended outside of the core into peripheral zones, indicating the potential of this technique for more accurate delineation of the heterogeneous areas of brain cancers. Magn Reson Med 60:842–849, 2008. © 2008 Wiley‐Liss, Inc.