bluuebunny/crossref_metadata_2025 huggingface dataset:
Enantiopure Mono‐ and Mixed‐Valence Multinuclear Cobalt Complexes from Amino Alcohol Based Ligands
Authors: Pradeep Chullikkattil P. , Zacharias Panthapally S. , Das Samar K.
Published: October 2007

Chiral amino alcohol based tridentate Schiff bases, derived from 5‐OMe‐, 5‐H‐, and 5‐NO2‐substituted salicylaldehydes and (S)‐(+)‐2‐phenylglycinol and (S)‐(–)‐2‐amino‐3‐phenyl‐1‐propanol, were found to act as versatile ligands in their coordination behavior towards cobalt and gave a range of complexes like mononuclear low‐spin CoIII complexes, mixed‐valence trinuclear CoIII–CoII–CoIII complexes, and a mixed‐valence tetranuclear (CoIII)3CoII complex on 1:1 molar ratio reaction with Co(CH3COO)2·4H2O in methanol at room temperature. The steric and electronic properties of these ligands are found to control the overall geometry and nuclearity of the resulting complexes. 5‐OMe‐Substituted ligands (H2L1 and H2L2) gave mononuclear low‐spin CoIII complexes [CoL1(HL1)]·0.25DMF (1) and [CoL2(HL2)]·0.25DMF (2). Single‐crystal X‐ray structure analysis of complex 2 revealed that the relevant complex crystallizes with four mononuclear units in the asymmetric unit (Z′ = 4), and these units self‐assemble through O–H···O hydrogen‐bonding interactions resulting in the formation of homochiral supramolecular helices in the crystal lattice. The 5‐H‐ and 5‐NO2‐substituted ligands (H2L3, H2L4, H2L5) afforded mixed‐valence trinuclear CoIII–CoII–CoIII complexes [Co(CoL32)2·H2O]·2DMF·2H2O (3), [Co(CoL42)2·H2O]·2DMF·H2O (4), and [Co(CoL52)2·DMF]·2DMF·H2O (5), respectively. Crystal structure analyses of complexes 3 and 5 revealed rare trinuclear geometries of these complexes, in which two terminal octahedral low‐spin CoIII complexes act as chelating ligands for a central high‐spin CoII center through alkoxide bridging. For steric reasons, the central cobalt adopts a highly distorted geometry in these complexes viz. distorted trigonal bipyramidal in complex 3 and distorted square planar in complex 5. The ligand H2L6 gave an interesting tetranuclear mixed‐valence complex, H[Co(CoL62)3]·H2O (6), in which three octahedral low‐spin CoIII complexes act as ligands for a central high‐spin CoII center in distorted trigonal prismatic geometry. Interestingly, the three types (mononuclear: 1, 2; trinuclear: 3, 4, 5; tetranuclear: 6) of complexes showed large variations in their nuclearity and overall geometry despite the fact that the experimental conditions for all these complexes were identical. This fact highlights the influence of different substitutions on ligands in determining the final geometry of the resulting complexes in these reactions. Complexes 1–6 were characterized by elemental and routine spectral analyses. Compounds 2, 3, 5, and 6 have been unequivocally characterized by single‐crystal X‐ray structure determinations as well. Chiral properties of these complexes were confirmed by circular dichroism (CD) spectral studies.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Critical Effect of Phosphane Ligands on the Mechanism of Carbon–Carbon Bond Formation Involving Palladium(II) Complexes: A Theoretical Investigation of Reductive Elimination from Square‐Planar and T‐Shaped Species
Authors: Ananikov Valentine P. , Musaev Djamaladdin G. , Morokuma Keiji
Published: October 2007

A theoretical ONIOM study has been carried out to understand the influence of phosphane ligands on the structure of Pd complexes and their reactivity in C–C bond formation. The calculations were performed for Me–Me reductive elimination with the ligands L = PPh3, PCy3, PMe3, PH3, and vinyl–vinyl, Ph–Ph, ethynyl–ethynyl, vinyl–Me, vinyl–Ph and vinyl–ethynyl couplings with L = PPh3 for [PdR2Ln] complexes (n = 1, 2). The calculations revealed critical changes in the reactivity of palladium complexes depending on the mechanism and ligand type. In the case of the standard four‐coordinate pathway (n = 2) the relative reactivity in carbon–carbon bond formation follows the order: L = PPh3 > PH3 > PCy3 > PMe3. However, for reductive elimination involving T‐shaped complexes by the ligand predissociation pathway (n = 1), the relative reactivity changes in the order: L = PCy3 > PPh3 > PH3 > PMe3. The theoretical study suggested that the steric effect of phosphane ligands has the largest impact on the structure of the initial palladium complexes, while the electronic effect is most influential on the transition states of C–C coupling in these complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Selenium‐Containing Tetrachalcogenins and Pentachalcogenepins Fused to Aromatic Systems
Authors: Alam Ashraful , Ogawa Satoshi , Muraoka Hiroki , Kon‐no Masaru , Nakajo Shiduko , Sato Ryu
Published: October 2007

Various ring‐sized cyclic polychalcogenides fused to aromatic systems were synthesized, and the structures were sufficiently characterized. Stabilities of the rings were examined in terms of the existence of selenium atoms. Benzopolychalcogenides are unstable molecules. However, benzo[1,2,3,4,5]tetrathiaselenepins with an isopropyl group or two methoxy groups on the ring were found to be stable. Similarly, the novel benzo[2,3,4,1,5]trithiadiselenepin ring was also stabilized by two methoxy groups. Benzo[1,2,3,4]trithiaselenin and benzo[2,3,1,4]dithiadiselenin were also synthesized by a controlled reaction with S2Cl2 at –78 °C. The ring systems were sensitive to air, moisture, light, and polar solvents. Extended π‐systems such as naphthalene and phenanthrene showed remarkable thermodynamic stability toward unstable rings. The unprecedented stabilities possessed by the polyaromatics are yet unclear. Phenanthro[9,10‐d][1,2,3]dithiaselenole was also successfully isolated as a novel molecule. It is the first isolated trichalcogenole having one selenium atom, which is stabilized by an extended π system. Phenanthro[9,10‐f][1,2,3,4,5]tetrathiaselenepin is stable in the solid state. The use of polar solvents under ambient conditions resulted in the extrusion of selenium from the ring to generate more stable trithiole rings. The structures of the five‐, six‐, and seven‐membered cyclic polychalcogenides were extensively established in this report.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
A Penicillamine Biosensor Based on Tyrosinase Immobilized on Nano‐Au/ PAMAM Dendrimer Modified Gold Electrode
Authors: Li Nian Bing , Kwak Juhyoun
Published: October 2007

Gold electrodes were modified with submonolayers of 3‐mercaptopropionic acid and further reacted with poly(amidoamine) (PAMAM) dendrimers to obtain thin films. The high affinity of PAMAM dendrimer for nano‐Au with its amine groups was used to realize the role of nano‐Au as an intermediator to immobilize the enzyme of tyrosinase. The characterization of the modified electrode was investigated by cyclic voltammetry, electrochemical impedance spectroscopy and atomic force microscopy (AFM). Tyrosinase can catalyze the oxidation of catechol to o‐benzoquinone. When penicillamine was added to the solution, it reacted with o‐benzoquinone to form the corresponding thioquinone derivatives, which resulted in decrease of the reduction current of o‐benzoquinone. Based on this, a new electrochemical sensor for determination of penicillamine has been developed.
Kinetics and Mechanism of Ni(II) Chelation in Model and Real Solutions of Xylem Sap of Quercus ilex
Authors: Correia dos Santos Margarida Maria , Alves Sheila , de Lurdes Simões Gonçalves Maria
Published: October 2007

The kinetics of formation and dissociation of Ni(II) complexes with oxalic and citric acids was studied by cyclic voltammetry in model solutions of xylem sap of Q. ilex (the dominant tree growing on serpentine soils of Northeast Portugal) using representative concentrations, pH and ionic strength. The role of magnesium on complex formation was analyzed from solutions where Mg is present at concentration levels found in the xylem sap of Q. ilex growing on both nonserpentine and serpentine soils. Kinetics studies were also done in diluted solutions of real xylem sap samples, spiked with increasing amounts of magnesium. The values obtained for the apparent rate constants were those anticipated by the proposed model. To test the validity of the methodology and mechanisms, formation rate constants, kf (M−1 s−1) of Ni(II) complexes with citrate and oxalate were evaluated that compare with the values from Eigen mechanism.
DNA Assisted Assembly of Multisegmented Nanowires
Authors: Lee Joun , Wang Aijun A. , Rheem Youngwoo , Yoo Bongyoung , Mulchandani Ashok , Chen Wilfred , Myung Nosang V.
Published: October 2007

This work demonstrates a highly specific and selective assembly of multisegmented nanowires on prepatterned gold electrodes using DNA hybridization. Multisegmented Au/Pd/Au nanowires were synthesized using template‐directed electrodeposition. Two complementary single‐stranded DNAs modified with thiol tags adsorb on gold electrodes and gold segments of nanowires, and enable the nanowires to assemble across electrodes. The assembled nanowires show ohmic contact with minimum contact resistance. Using these nanowires, the temperature dependent electrical resistance and the sensing performance toward hydrogen were investigated. The temperature coefficient of resistance of nanowires was lower than bulk polycrystalline counterpart, because of higher electron scattering at the surface and grain boundaries of nanowires. The nanowires were sensitive toward hydrogen gas at room temperature with a detection limit of 0.5%.
Direct Electrochemical Sensing and Detection of Natural Antioxidants and Antioxidant Capacity in Vitro Systems
Authors: Blasco Antonio Javier , González Crevillén Agustín , González María Cristina , Escarpa Alberto
Published: October 2007

This review highlights the role of electrochemical approaches in the sensing of antioxidants and their antioxidant capacity with especial attention to the analytical possibilities of electrochemistry in the direct evaluation of antioxidant capacity exhibited by food and biological samples due to the termed dietary, natural or biological antioxidants (mainly polyphenols, and vitamins C and E). The analytical potency of the electrochemistry is comprehensively stated and the selected results found in the literature are summarized and discussed critically. The main electrochemical approaches used have been cyclic voltammetry (CV) and flow injection analysis with amperometric detection (FIA‐ED). In addition, miniaturization is going to break new frontiers in the evaluation of antioxidant activity.
Direct Electrochemistry of Cytochrome P450 Reductases in Surfactant and Polyion Films
Authors: Sultana Nasreen , Schenkman John B. , Rusling James F.
Published: October 2007

NADPH‐cytochrome P450 reductase (CPR) serves as electron donor for cytochrome P450 catalyzed monooxygenase reactions utilizing flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) as electron transfer cofactors. Here, stable films of human and rabbit CPRs with didodecyldimethylammonium bromide (DDAB), dimyristoylphosphatidyl choline (DMPC), and poly(diallyldimethylammonium) (PDDA) were made on pyrolytic graphite (PG) electrodes for comparative structural and electrochemical studies. CD and UV‐VIS absorbance spectra suggested that near native CPR conformation is retained in PDDA films, and some conformational changes occur in DMPC or DDAB films. Cyclic voltammetry of these films gave quasireversible pairs of peaks at average formal potential −0.246±0.008 V vs. NHE. In human CPR‐DDAB (H‐CPR‐DDAB), a second pair of peaks at +0.317 V vs. NHE was found that depended strongly on identity of buffer and salt. Excepting H‐CPR in DDAB, films showed similar voltammetry, formal potentials, and ks values. While CPR‐PDDA films had near native CPR structures, electrochemical parameters did not differ significantly from CPR‐DMPC films. The relative independence of film voltammetry from the influence of film materials for CPRs is in contrast with heme iron proteins that, while retaining near native structures, have formal potentials that depend significantly on identity of the film material.
Comparison of Boron‐Doped Diamond and Glassy Carbon Electrodes for Determination of Procaine Hydrochloride
Authors: Wei Min , Zhou Yanli , Zhi Jinfang , Fu Degang , Einaga Yasuaki , Fujishima Akira , Wang Xuemei , Gu Zhongze
Published: October 2007

The electrochemical oxidation of procaine hydrochloride (PC⋅HCL, 2‐diethylaminoethyl 4‐aminobenzoate hydrochloride) was investigated at as‐deposited boron‐doped diamond (ad‐BDD) electrode, anodically oxidized BDD (ao‐BDD) electrode and glassy carbon (GC) electrode using cyclic voltammetry (CV). Well‐defined cyclic voltammograms were obtained for PC⋅HCL oxidation with high signal‐to‐background (S/B) ratio, low tendency for adsorption, good reproducibility and long‐term stability at ad‐BDD electrode, demonstrating its superior electrochemical behavior and significant advantages in contrast to ao‐BDD and GC electrode. At 100 μM PC⋅HCL, the voltammetric S/B ratio was nearly one order of magnitude higher at an ad‐BDD electrode than that at a GC electrode. In a separate set of experiments for oxidation of 100 μM PC⋅HCL, 96%, 92% and 84% of the initial oxidation peak current was retained at the ad‐BDD, ao‐BDD and GC electrode, respectively, by stirring the solution after the tenth cycle. The current response was linearly proportional to the square root of the scan rate within the range 10–1000 mV s−1 in 10 μM PC⋅HCL solutions, indicating that the oxidation process was diffusion‐controlled with negligible adsorption at an ad‐BDD surface. The good linearity was observed for a concentration range from 5 to 200 μM with a linear equation of y=0.03517x+0.65346 (r=0.999), and the detection limit was 0.5 μM for oxidation of PC⋅HCL at the ad‐BDD electrode. The ad‐BDD electrode could maintain 100% of its original activity after intermittent use for 3 months.
Properties of the Contactless Impedance Detector with Insulated Wire Electrodes Placed Inside the Flowing Liquid Stream
Authors: Nádherná Martina , Opekar František , Štulík Karel
Published: October 2007

The behavior of a flow cell, in which the impedance is measured between two insulated wire electrodes located within the stream of the test liquid, is described and compared with that of a semi‐quantitative theoretical model. A new approach is used to the monitoring of the impedance signal, based on connecting the cell as the input impedance of an operational amplifier in the differentiating circuit. A triangular AC voltage is fed to one of the electrodes and the other electrode is connected to the amplifier input. The square‐wave voltage at the amplifier output depends at low frequencies (from hundreds of Hz to several kHz) on the capacitive component of the overall impedance. The basic analytical parameters are in satisfactory agreement with the model and are comparable to those obtained with common contactless impedance detectors operating at higher frequencies of hundreds of kHz to a few MHz and monitoring primarily the conductance component of the impedance. The system described offers new detection possibilities, mainly for nonionic analytes of varying polarities.
Voltammetric Detection of Ofloxacin in Human Urine at a Congo Red Functionalized Water‐Soluble Carbon Nanotube Film Electrode
Authors: Yang Chunhai , Xu Yanxia , Hu Chengguo , Hu Shengshui
Published: October 2007

A simple physical method was developed for the surface modification and the solubilization of MWNTs in water by Congo red. The resulting water‐soluble MWNTs (MWNTs‐CR) can form stable and uniform films on solid supports when dried, which was used to fabricate MWNTs‐CR modified glassy carbon electrodes (MWNTs‐CR/GCE). Voltammetric studies showed that MWNTs‐CR/GCE exhibited a strong enhancement effect on the electrooxidation of ofloxacin. MWNTs‐CR films were also proved to possess overwhelming advantages as electrochemical sensing films over other commonly used MWNTs composite films (e.g., MWNTs‐DHP and MWNTs‐Nafion), reflected by the higher oxidation current, lower background and stronger accumulation capacity towards less soluble species. The sensitive oxidation of ofloxacin at MWNTs‐CR/GCE was used for the determination of ofloxacin. Under optimal conditions, the oxidation current was proportional to ofloxacin concentration in the ranges of 5×10−8–3.0×10−5 M. The detection limit of 9×10−9 M was obtained for 350 s accumulation at open circuit (S/N=3). This method was applied to the determination of ofloxacin in human urine and the result was satisfying.
Amperometric Glucose Biosensor on Layer by Layer Assembled Carbon Nanotube and Polypyrrole Multilayer Film
Authors: Shirsat Mahendra D. , Too Chee O. , Wallace Gordon G.
Published: October 2007

An amperometric glucose biosensor on layer by layer assembled carbon nanotube and polypyrrole multilayer film has been reported in the present investigation. Homogeneous and stable single wall carbon nanotubes (SWNTs) and polypyrrole (PPy) multilayer films were alternately assembled on platinum coated Polyvinylidene fluoride (PVDF) membrane. Since conducting polypyrrole has excellent anti‐interference ability, protection ability in favor of increasing the amount of the SWNTs on platinum coated PVDF membrane and superior transducing ability, a layer by layer approach of polypyrrole and carbon nanotubes has provided an excellent matrix for the immobilization of enzyme. The layer‐by‐layer assembled SWNTs and PPy‐modified platinum coated PVDF membrane is shown to be an excellent amperometric sensor over a wide range of concentrations of glucose. The glucose oxidase (GOx) was immobilized on layer by layer assembled film by a physical adsorption method by cross linking through Glutaraldehyde. The glucose biosensor exhibited a linear response range from 1 mM to 50 mM of glucose concentration with excellent sensitivity of 7.06 μA/mM.
Least action principle, equilibrium states, iterative adjustment and the stability of alluvial channels
Authors: Nanson Gerald C. , Huang He Qing
Published: October 2007

The energy based least action principle (LAP) has proven to be very successful for explaining natural phenomena in both classical and modern physics. This paper briefly reviews its historical development and details how, in three ways, it governs the behaviour and stability of alluvial rivers. First, the LAP embodies the special stationary equilibrium state of motion and so its incorporation with the principle of energy conservation explains why so many optimizing hypotheses have been proposed in fluvial geomorphology. Second, the variational approach underlying the LAP provides a more straightforward and simpler fuzzy‐object orientated method for solving river regime problems than do the various complex Newtonian formulations. Third, it is shown that in fluvial systems with surplus energy the surplus can be expended with slope and/or channel geometry adjustments, with the degree of channel geometry adjustment quantified by the dimensionless numbers F for depth dominated adjustment and H for width/depth dominated adjustment. Different planforms are preferred at different energy levels, with H providing a quantitative measure of the flow's efficiency for moving sediment. In rivers with insufficient energy, the interactions of endogenous and exogenous factors are shown to be capable, in certain circumstances, of achieving a stationary equilibrium condition which acts as the attractor state. Importantly, this study describes how iterative changes enable systems to achieve such a stable equilibrium. Copyright © 2007 John Wiley & Sons, Ltd.
The measurement and modelling of rill erosion at angle of repose slopes in mine spoil
Authors: Hancock G. R. , Crawter D. , Fityus S. G. , Chandler J. , Wells T.
Published: October 2007

The process of rill erosion causes significant amounts of sediment to be moved in both undisturbed and disturbed environments and can be a significant issue for agriculture as well as mining lands. Rills also often develop very quickly (from a single rainfall event to a season) and can develop into gullies if sufficient runoff is available to continue their development. This study examines the ability of a terrestrial laser scanner to quantify rills that have developed on fresh and homogeneous mine spoil on an angle of repose slope. It also examines the ability of the SIBERIA erosion model to simulate the rill's spatial and temporal behaviour. While there has been considerable work done examining rill erosion on rehabilitated mine sites and agricultural fields, little work has been done to examine rill development at angle of repose sites. Results show that while the overall hillslope morphology was captured by the laser scanner, with the morphology of the rills being broadly captured, the characteristics of the rills were not well defined. The digital elevation model created by the laser scanner failed to capture the rill thalwegs and tops of the banks, therefore delineating a series of ill defined longitudinal downslope depressions. These results demonstrate that an even greater density of points is needed to capture sufficient rill morphology. Nevertheless, SIBERIA simulations of the hillslope demonstrated that the model was able to capture rill behaviour in both space and time when correct model parameters were used. This result provides confidence in the SIBERIA model and its parameterization. The results demonstrate the sensitivity of the model to changes in parameters and the importance of the calibration process. Copyright © 2007 John Wiley & Sons, Ltd.
Relation between flow, surface‐layer armoring and sediment transport in gravel‐bed rivers
Authors: Pitlick John , Mueller Erich R. , Segura Catalina , Cress Robert , Torizzo Margaret
Published: October 2007

This study investigates trends in bed surface and substrate grain sizes in relation to reach‐scale hydraulics using data from more than 100 gravel‐bed stream reaches in Colorado and Utah. Collocated measurements of surface and substrate sediment, bankfull channel geometry and channel slope are used to examine relations between reach‐average shear stress and bed sediment grain size. Slopes at the study sites range from 0·0003 to 0·07; bankfull depths range from 0·2 to 5 m and bankfull widths range from 2 to 200 m. The data show that there is much less variation in the median grain size of the substrate, D50s, than there is in the median grain size of the surface, D50; the ratio of D50 to D50s thus decreases from about four in headwater reaches with high shear stress to less than two in downstream reaches with low shear stress. Similar trends are observed in an independent data set obtained from measurements in gravel‐bed streams in Idaho. A conceptual quantitative model is developed on the basis of these observations to track differences in bed load transport through an idealized stream system. The results of the transport model suggest that downstream trends in total bed load flux may vary appreciably, depending on the assumed relation between surface and substrate grain sizes. Copyright © 2007 John Wiley & Sons, Ltd.
Measuring river velocities using GPS River Flow Tracers (GRiFTers)
Authors: Stockdale R. J. , McLelland S. J. , Middleton R. , Coulthard T. J.
Published: October 2007

Existing methods of measuring flow velocities in natural rivers are largely based on series of point measurements. Acquisition of these data can be time consuming and difficult, especially in high flow conditions. This paper introduces the use of GPS drifters (termed GRiFTers) to measure surface flow velocities in a 400 m reach of the River Swale, UK. Over 10 000 measurements were made in a 3 hour period and aggregated over a 2 m grid to generate a genuine distributed representation of flow across the reach. The technique shows great promise to provide new insights into flow patterns over long reaches of rivers, over a range of flow conditions, and may also provide valuable data for numerical model validation. Copyright © 2007 John Wiley & Sons, Ltd.
Developing an intervention for depressed, chronically medically ill elders: a model from COPD
Authors: Alexopoulos George S. , Raue Patrick J. , Sirey Jo Anne , Arean Patricia A.
Published: October 2007

Background

Geriatric depression preferentially afflicts individuals with chronic medical illnesses. Disability, hopelessness, lack of acceptance of antidepressant treatment, and limited problem‐solving skills contribute to poor treatment adherence, compromised outcomes, and chronically experienced adversity.

Methods

This paper uses depression comorbid with chronic obstructive pulmonary disease (COPD) as a model entity to develop an approach for integrating treatment components essential for improving treatment adherence and outcomes.

Results

The behavioral inertia of depression and its coexisting cognitive problems reduce adherence to the sustained and complex demands of the COPD rehabilitation regimen and antidepressant treatment. An intervention identifying reasons for poor treatment adherence and offering direct instructions for addressing them can be combined with problem‐solving therapy to target treatment adherence, depressive symptoms, and disability.

Conclusions

An intervention focusing on treatment adherence and problem‐solving skills development may serve as the platform for administering specific treatments to address the interacting problems of depressed medically ill patients. Copyright © 2007 John Wiley & Sons, Ltd.
Functional connectivity estimation in fMRI data: Influence of preprocessing and time course selection
Authors: Gavrilescu Maria , Stuart Geoffrey W. , Rossell Susan , Henshall Katherine , McKay Colette , Sergejew Alex A. , Copolov David , Egan Gary F.
Published: October 2007

A number of techniques have been used to provide functional connectivity estimates for a given fMRI data set. In this study we compared two methods: a ‘rest‐like’ method where the functional connectivity was estimated for the whitened residuals after regressing out the task‐induced effects, and a within‐condition method where the functional connectivity was estimated separately for each experimental condition. In both cases four pre‐processing strategies were used: 1) time courses extracted from standard pre‐processed data (standard); 2) adjusted time courses extracted using the volume of interest routines in SPM2 from standard pre‐processed data (spm); 3) time courses extracted from ICA denoised data (standard denoised); and 4) adjusted time courses extracted from ICA denoised data (spm denoised). The temporal correlation between time series extracted from two cortical regions were statistically compared with the temporal correlation between a time series extracted from a cortical region and a time series extracted form a region placed in CSF. Since the later correlation is due to physiological noise and other artifacts, we used this comparison to investigate whether rest‐like and task modulated connectivity could be estimated from the same data set. The pre‐processing strategy had a significant effect on the connectivity estimates with the standard time courses providing larger connectivity values than the spm time courses for both estimation methods. The CSF comparison indicated that for our data set only rest‐like connectivity could be estimated. The rest‐like connectivity values were similar with connectivity estimated from resting state data. Hum Brain Mapp 2008. © 2007 Wiley‐Liss, Inc.
Latent volumetric structure of the human brain: Exploratory factor analysis and structural equation modeling of gray matter volumes in healthy children and adults
Authors: Colibazzi Tiziano , Zhu Hongtu , Bansal Ravi , Schultz Robert T. , Wang Zhishun , Peterson Bradley S.
Published: October 2007

Previous studies have investigated patterns of volumetric covariance (i.e. intercorrelation) among brain regions. Methodological issues, however, have limited the validity and generalizability of findings from these prior studies. Additionally, patterns of volumetric covariance have often been assumed to reflect the presence of structural networks, but this assumption has never been tested formally. We identified patterns of volumetric covariance, correlated these patterns with behavioral measures, and tested the hypothesis that the observed patterns of covariance reflect the presence of underlying networks. Specifically, we performed factor analysis on regional brain volumes of 99 healthy children and adults, and we correlated factor scores with scores on the Stroop Word‐Color Interference Test. We identified four latent volumetric systems in each hemisphere: dorsal cortical, limbic, posterior, and basal ganglia. The positive correlation of the right posterior system with Stroop scores suggested that larger latent volumes are detrimental to inhibitory control. We also applied Structural Equation Modeling (SEM) to our dataset (n = 107) to test whether a model based on the anatomical pathways within cortico‐striatal‐thalamic‐cortical (CSTC) circuits accounts for the covariances observed in our sample. The degree to which SEM predicted volumetric covariance in the CSTC circuit depended on whether we controlled for age and whole brain volume in the analyses. Removing the effects of age worsened the fit of the model, pointing to a possible developmental component in establishing connections within CSTC circuits. These modeling techniques may prove useful in the future for the study of structural networks in disease populations. Hum Brain Mapp 2008. © 2007 Wiley‐Liss, Inc.
Health and labour force participation of older people in Europe: What do objective health indicators add to the analysis?
Authors: Kalwij Adriaan , Vermeulen Frederic
Published: October 2007

This paper studies labour force participation of older individuals in 11 European countries. The data are drawn from the new Survey of Health, Ageing and Retirement in Europe (SHARE). We examine the value added of objective health indicators in relation to potentially endogenous self‐reported health. We approach the endogeneity of self‐reported health as an omitted variables problem. In line with the literature on the reliability of self‐reported health ambiguous results are obtained. In some countries self‐reported health does a fairly good job and controlling for objective health indicators does not add much to the analysis. In other countries, however, the results show that objective health indicators add significantly to the analysis and that self‐reported health is endogenous due to omitted objective health indicators. These latter results illustrate the multi‐dimensional nature of health and the need to control for objective health indicators when analysing the relation between health status and labour force participation. This makes an instrumental variables approach to deal with the endogeneity of self‐reported health less appropriate. Copyright © 2007 John Wiley & Sons, Ltd.
Explaining trends in concentration of healthcare commissioning in the English NHS
Authors: Dusheiko Mark , Goddard Maria , Gravelle Hugh , Jacobs Rowena
Published: October 2007

In recent years there have been marked changes in organisational structures and budgetary arrangements in the English National Health Service, potentially altering the relationships between purchasers (primary care organisations (PCOs) and general practices) and hospitals. We show that elective admissions from PCOs and practices became significantly more concentrated across hospitals between 1997/98 and 2002/03. There was a reduction in the average number of hospitals used by PCOs (16.7–14.2), an increase in the average share of admissions accounted for by the main hospital (49–69%), and an increase in the average Herfindahl index (0.35–0.55). About half the increase in concentration arose from the increase in the number of purchasing organisations as 100 health authorities were replaced by 303 primary care trusts. Most of the remainder was probably due to hospital mergers. Fundholding general practices that held budgets for elective admissions had less concentrated admission patterns than non‐fundholders whose admissions were paid for by their PCO. Around 1/10th of the increase in concentration at practice level was due to the abolition of fundholding in April 1999. Our results have implications for the effects of the recent reintroduction of fundholding and the halving of the number of PCOs. Copyright © 2007 John Wiley & Sons, Ltd.
Attribute substitution in early enrollment decisions into Medicare prescription drug plans
Authors: Frakt Austin B. , Pizer Steven D.
Published: October 2007

Stand‐alone outpatient prescription drug plans (PDPs), introduced in January 2006, have become the most popular source for coverage of outpatient prescription drugs under Medicare relative to other available Medicare plan types (e.g. Medicare Advantage drug plans). Using county‐level enrollment figures from the Centers for Medicare & Medicaid Services linked to other public sources, we study attribute substitution in beneficiary decision‐making with respect to PDP enrollment. To do so, we relate county‐level PDP market share to county‐level political support for the administration implementing the new benefit (the Bush Administration), controlling for socio‐demographic and market characteristics. We find statistically significant evidence that greater support for the Bush administration is associated with increased PDP market share. Copyright © 2007 John Wiley & Sons, Ltd.
Randomized, double-blind, placebo-controlled trial of corticosteroids after Kasai portoenterostomy for biliary atresia
Authors: Davenport Mark , Stringer Mark D. , Tizzard Sarah A. , McClean Patricia , Mieli-Vergani Giorgina , Hadzic Nedim
Published: October 2007

The objective of this study was to evaluate adjuvant corticosteroids after Kasai portoenterostomy for biliary atresia. The study consisted of a prospective, 2-center, double-blind, randomized, placebo-controlled trial of post–Kasai portoenterostomy corticosteroids (oral prednisolone: 2 mg/kg/day from day 7 to day 21 and 1 mg/kg/day from day 22 to day 28). The data were compared with χ2 or Mann-Whitney tests, as appropriate. Seventy-one postoperative infants with type 3 biliary atresia were randomized to receive either oral prednisolone (n = 36) or a placebo (n = 37). At 1 month, the median bilirubin level was lower in the steroid group (66 versus 92 μmol/L,

P

= 0.06), but no difference was evident at 6 (

P

= 0.56) or 12 (

P

= 0.3) months. The proportion of infants with a normal bilirubin level (<20 μmol/L) at 6 (47% versus 49%,

P

= 0.89) and 12 months (50% versus 40%,

P

= 0.35) was not significantly different. The need for transplantation by 6 (12% versus 13%,

P

= 0.99) and 12 months (26% versus 35%,

P

= 0.47) was not significantly different. The steroid effect was more pronounced in younger infants (less than 70 days at Kasai portoenterostomy, n = 51), with a reduced bilirubin level at 1 month (64 versus 117 μmol/L,

P

= 0.01) and with a greater proportion with a normal bilirubin level at 12 months (54% versus 37%,

P

= 0.22).

Conclusion:

There was a beneficial effect on the rate of reduction of bilirubin in the early postoperative period (specifically in infants less than 70 days old at surgery), but this steroid regimen did not reduce the need for liver transplantation. (Hepatology 2007;46:1821–1827.)
Evidence for human leukocyte antigen heterozygote advantage against hepatitis C virus infection
Authors: Hraber Peter , Kuiken Carla , Yusim Karina
Published: October 2007

Outcomes of infection with hepatitis C virus (HCV) vary widely, from asymptomatic clearance to chronic infection, leading to complications that include fibrosis, cirrhosis, hepatocellular carcinoma, and liver failure. Previous studies have reported statistical associations between human leukocyte antigen (HLA) heterozygosity and favorable outcomes of infection with either hepatitis B virus (HBV) or human immunodeficiency virus (HIV) (the “heterozygote advantage”). To investigate whether HLA zygosity is associated with outcome of HCV infection, we used data from the United States Organ Procurement and Transplantation Network database of 52,435 liver transplant recipients from 1995 through 2005. Of these, 30,397 were excluded for lack of HLA data, retransplantation, known HIV infection, or insufficient information regarding HBV infection. The remaining cases were analyzed for associations between HCV infection and HLA zygosity with 1-sided Fisher's exact tests. Results show significantly lower proportions of HLA-DRB1 heterozygosity among HCV-infected than uninfected cases. The differences were more pronounced with alleles represented as functional supertypes (

P

= 1.05 × 10−6) than as low-resolution genotypes (

P

= 1.99 × 10−3). No significant associations between zygosity and HCV infection were found for other HLA loci.

Conclusion:

These findings constitute evidence for an advantage among carriers of different supertype HLA-DRB1 alleles against HCV infection progression to end-stage liver disease in a large-scale, long-term study population. Considering HLA polymorphism in terms of supertype diversity is recommended in strategies to design association studies for robust results across populations and in trials to improve treatment options for patients with chronic viral infection. Access to deidentified clinical information relating genetic variation to viral infection improves understanding of variation in infection outcomes and might help to personalize medicine with treatment options informed in part by human genetic variation. (Hepatology 2007.)
Clonal, cultured, murine fetal liver hepatoblasts maintain liver specification in chimeric mice
Authors: Rogler Charles E. , Zhou Hong Chou , LeVoci Lauretta , Rogler Leslie E.
Published: October 2007

Recent studies have shown a pluripotential nature of stem cells that were previously thought to be committed to specific lineages. HBC-3 cells are a clonal fetal murine hepatoblast cell line derived from an e9.5 murine embryo, and these cells can be induced to form hepatocytes and bile ducts

in vitro

and when transplanted into adult mouse livers. To determine whether HBC-3 cells can exhibit a pluripotential phenotype, we created chimeric mice by injection of enhanced green fluorescent protein (EGFP)–marked HBC-3 cells into wild-type or dipeptidyl dipeptidase IV (DPPIV) knockout blastocysts. Genetically labeled HBC-3 cells were identified by EGFP polymerase chain reaction (PCR) in all the major organs of many chimeric mice and visualized in chimeras as bright red DPPIV-positive cells in the DPPIV knockout chimeric mice. Strikingly, the HBC-3 cells maintained phenotypic and biochemical features of liver specification in every case in which they were identified in nonliver organs, such as brain, mesenchyme, and bone. In adult liver they were present as small foci of hepatocytes and bile ducts in the chimeras. Additional major histocompatibility complex (MHC) marker analysis and X and Y chromosome content analysis further demonstrated that HBC-3 cells did not acquire the phenotype of the organs in which they resided and that they were not present because of fusion with host cells.

Conclusion:

In contrast to other stem cell types, these data demonstrate that cultured murine fetal liver stem cells appear to maintain their liver specification in the context of nonliver organs in chimeric mice. (Hepatology 2007.)
Distinct hepatitis C virus core and F protein quasispecies in tumoral and nontumoral hepatocytes isolated via microdissection
Authors: Sobesky Rodolphe , Feray Cyrille , Rimlinger François , Derian Nicolas , Dos Santos Alexandre , Roque-Afonso Anne-Marie , Samuel Didier , Bréchot Christian , Thiers Valérie
Published: October 2007

Hepatitis C virus (HCV) genetic variability may be involved in liver carcinogenesis. We investigated HCV core and corresponding putative F protein genetic variability in hepatocellular carcinoma (HCC) and cirrhotic nodules. Hepatocyte clusters from 7 patients with HCC and HCV1b-related cirrhosis were isolated via microdissection of HCC tissues and 2 nontumoral cirrhotic nodules. The HCV core complementary DNA was cloned and sequenced from each liver compartment and from the serum of 2 patients. Nucleotide diversity and synonymous and nonsynonymous substitutions were analyzed within and between compartments via phylogenetic analysis and Mantel's test. Liver HCV RNA accumulation was lower in HCC. Increased quasispecies diversity and complexity was observed with HCC in 6 of 7 patients. Mantel's test demonstrated marked compartmentalization of quasispecies between HCC and cirrhotic nodules in all 7 patients and also between the 2 nontumoral nodules in 5 of them. Synonymous–nonsynonymous substitution analysis indicated low selection against tumoral core quasispecies in all patients and a more selective pressure against F protein quasispecies in all compartments. In the 2 subjects analyzed, HCC and nontumoral hepatocyte quasispecies were only minor or undetected in serum.

Conclusion:

In tumoral hepatocytes, low-replicating hepatitis C quasispecies are compartmentalized and more diversified and are subjected to low selective pressure. Our study supports the importance of core genetic variability in hepatocellular carcinogenesis. (Hepatology 2007.)

This is a corrected version of the abstract first published online on 12 October 2007 — the corrected version appears in print.
Fish oil prevents sucrose-induced fatty liver but exacerbates high-safflower oil-induced fatty liver in ddy mice
Authors: Yamazaki Tomomi , Nakamori Akiko , Sasaki Eriko , Wada Satoshi , Ezaki Osamu
Published: October 2007

Diets high in sucrose/fructose or fat can result in hepatic steatosis (fatty liver). We analyzed the effects of dietary fish oil on fatty liver induced by sucrose, safflower oil, and butter in ddY mice. In experiment I, mice were fed a high-starch diet [70 energy% (en%) starch] plus 20% (wt/wt) sucrose in the drinking water or fed a high-safflower oil diet (60 en%) for 11 weeks. As a control, mice were fed a high-starch diet with drinking water. Fish oil (10 en%) was either supplemented or not. Mice supplemented with sucrose or fed safflower oil showed a 1.7-fold or 2.2-fold increased liver triglyceride content, respectively, compared with that of control mice. Fish oil completely prevented sucrose-induced fatty liver, whereas it exacerbated safflower oil-induced fatty liver. Sucrose increased SREBP-1c and target gene messenger RNAs (mRNAs), and fish oil completely inhibited these increases. In experiment II, mice were fed a high-safflower oil or a high-butter diet, with or without fish oil supplementation. Fish oil exacerbated safflower oil–induced fatty liver but did not affect butter-induced fatty liver. Fish oil increased expression of peroxisome proliferator-activated receptor gamma (PPARγ) and target CD36 mRNA in safflower oil-fed mice. These increases were not observed in sucrose-supplemented or butter-fed mice.

Conclusion:

The effects of dietary fish oil on fatty liver differ according to the cause of fatty liver; fish oil prevents sucrose-induced fatty liver but exacerbates safflower oil-induced fatty liver. The exacerbation of fatty liver may be due, at least in part, to increased expression of liver PPARγ. (Hepatology 2007.)
Hepatocyte transplantation and drug-induced perturbations in liver cell compartments
Authors: Wu Yao-Ming , Joseph Brigid , Berishvili Ekaterine , Kumaran Vinay , Gupta Sanjeev
Published: October 2007

The potential for organ damage after using drugs or chemicals is a critical issue in medicine. To delineate mechanisms of drug-induced hepatic injury, we used transplanted cells as reporters in dipeptidyl peptidase IV–deficient mice. These mice were given phenytoin and rifampicin for 3 days, after which monocrotaline was given followed 1 day later by intrasplenic transplantation of healthy C57BL/6 mouse hepatocytes. We examined endothelial and hepatic damage by serologic or tissue studies and assessed changes in transplanted cell engraftment and liver repopulation by histochemical staining for dipeptidyl peptidase IV. Monocrotaline caused denudation of the hepatic sinusoidal endothelium and increased serum hyaluronic acid levels, along with superior transplanted cell engraftment. Together, phenytoin, rifampicin, and monocrotaline caused further endothelial damage, reflected by greater improvement in cell engraftment. Phenytoin, rifampicin, and monocrotaline produced injury in hepatocytes that was not apparent after conventional tissue studies. This led to transplanted cell proliferation and extensive liver repopulation over several weeks, which was more efficient in males compared with females, including greater induction by phenytoin and rifampicin of cytochrome P450 3A4 isoform that converts monocrotaline to toxic intermediates. Through this and other possible mechanisms, monocrotaline-induced injury in the endothelial compartment was retargeted to simultaneously involve hepatocytes over the long term. Moreover, after this hepatic injury, native liver cells were more susceptible to additional pro-oxidant injury through thyroid hormone, which accelerated the kinetics of liver repopulation.

Conclusion:

Transplanted reporter cells will be useful for obtaining insights into homeostatic mechanisms involving liver cell compartments, whereas targeted injury in hepatic endothelial and parenchymal cells with suitable drugs will also help advance liver cell therapy. (Hepatology 2007.)
A pilot project examining the predicted preferences of patients and physicians in the primary prophylaxis of variceal hemorrhage
Authors: Longacre Anna V. , Imaeda Avlin , Garcia-Tsao Guadalupe , Fraenkel Liana
Published: October 2007

Endoscopic variceal ligation (EVL) and nonselective beta-blockers (hereafter just called beta-blockers) are both effective for primary prophylaxis for variceal hemorrhage; however, the route of administration and side effects of these treatments are distinct. The objective of this study was to examine predicted preferences of patients and physicians for the primary prevention of variceal hemorrhage. Untreated patients with newly diagnosed esophageal varices and practicing gastroenterologists were enrolled in this study. Patients with contraindications to either EVL or beta-blockers were excluded. Predicted preferences for treatment were evaluated with an interactive computer task designed to elicit subjects' trade-offs related to the route of administration, risk of fatigue, sexual dysfunction, dysphagia, shortness of breath and/or hypotension, procedure-related bleeding, and perforation. Fifty-three patients and 61 physicians were enrolled. Thirty-four (64%) patients and 35 (57%) physicians preferred EVL over beta-blockers. Patients' predicted preferences were most strongly influenced by the risks of shortness of breath or hypotension, fatigue, and procedure-related bleeding, whereas physicians placed greater importance on procedure-related bleeding, sexual dysfunction, and perforation. Forty-eight patients were prescribed beta-blockers, two were not given prophylaxis, and three were lost to follow-up.

Conclusion:

Predicted treatment preferences among both patients and physicians for primary prophylaxis of variceal hemorrhage vary significantly. Physicians in this study preferring EVL stated that they prescribe beta-blockers as first-line therapy in order to remain compliant with guidelines. Physicians should discuss both EVL and beta-blockers with patients requiring primary prophylaxis for variceal hemorrhage. Future guidelines should incorporate individual patient preferences. (Hepatology 2007.)