bluuebunny/crossref_metadata_2025 huggingface dataset:
Retinal horizontal cell‐specific promoter activity and protein expression of zebrafish connexin 52.6 and connexin 55.5
Authors: Shields Colleen R. , Klooster Jan , Claassen Yvonne , Ul‐Hussain Mahboob , Zoidl Georg , Dermietzel Rolf , Kamermans Maarten
Published: February 2007

Connexins in retinal horizontal cells (HC) function in the processing of visual information. For example, gap junction‐forming connexins may contribute to the spatial integration of visual stimuli. Additionally, connexin hemichannels have been hypothesized to participate in the feedback pathway from HCs to cones. To verify the identities of the zebrafish HC connexins, we performed promoter expression and immunohistochemical studies of connexin 52.6 (Cx52.6) and Cx55.5. Zebrafish embryos were microinjected with Cx52.6 or Cx55.5 promoter sequences and a green fluorescent protein reporter construct. Light and electron microscopic (EM) analysis showed green fluorescent protein expression exclusively in retinal HCs. Immunohistochemistry confirmed that HCs express Cx52.6 and Cx55.5 proteins. Light microscopy revealed Cx52.6 and Cx55.5 in the retinal inner nuclear and outer plexiform layers. Double labeling for Cx55.5 or Cx52.6 and cell‐specific markers (tyrosine hydroxylase, protein kinase C‐α, or GluR2) demonstrated that these connexins do not localize to interplexiform or ON bipolar cells, but most likely are present in HCs. Preembedding immuno‐EM confirmed the HC‐specific expression of Cx52.6 and Cx55.5 and illustrated the presence of these two connexins in gap junctions between HCs. The EM data also revealed robust labeling for Cx55.5 in hemichannels on HC dendrites in photoreceptor synaptic terminals. Voltage‐clamp experiments in cultured cells demonstrated that Cx55.5‐containing hemichannels can open at physiological membrane potentials. These results offer the first in vivo demonstration of the HC‐specific activities of the Cx52.6 and Cx55.5 promoters. Furthermore, these data provide the first proof at the protein level for retinal HC‐specific connexins in the zebrafish. J. Comp. Neurol. 501:765–779, 2007. © 2007 Wiley‐Liss, Inc.
Effect of Branching on Two‐Photon Absorption in Triphenylbenzene Derivatives
Authors: Terenziani Francesca , Le Droumaguet Céline , Katan Claudine , Mongin Olivier , Blanchard‐Desce Mireille
Published: February 2007

The photophysical and linear and nonlinear spectral properties of octupolar compounds with a triphenylbenzene core are investigated and compared with properties of corresponding dipolar branches. A correlation is found between the solvatochromic behavior and the two‐photon absorption cross section. Moreover, the nature of the core is found to be responsible for the nature of the coupling between branches; in the studied case only (weak) electrostatic interactions are effective, while other cores, like the triphenylamine moiety, are able to promote coherent coupling between the branches, leading to strongly nonadditive properties.
The Shape of Leucine in the Gas Phase
Authors: Cocinero Emilio J. , Lesarri Alberto , Grabow Jens‐Uwe , López Juan C. , Alonso José L.
Published: February 2007

Two structures of neutral leucine are detected in the jet‐cooled rotational spectrum of a laser‐ablation molecular‐beam Fourier transform microwave (LA‐MB‐FTMW) experiment. The comparison between the experimental rotational and 14N nuclear quadrupole coupling constants and those calculated ab initio provides conclusive evidence for the identification of the conformers. The most stable species is stabilized by a NH⋅⋅⋅O=C intramolecular hydrogen bond and a cis‐COOH interaction, while a higher‐energy conformer exhibits a N⋅⋅⋅HO intramolecular hydrogen bond and trans‐COOH, as in lower aliphatic amino acids. The isobutyl side chain adopts the same configuration in the two conformers of leucine, characterized by a trans arrangement of the C′CαCβCγCδ chain. The differences with the preferred side chain configurations observed in valine and isoleucine are discussed.
Neuronal control of myogenic regulatory factor accumulation in fetal muscle
Authors: Washabaugh Charles H. , Ontell Martin P. , Shand Stuart H. , Bradbury Neil , Kant Jeffrey A. , Ontell Marcia
Published: February 2007

The lumbosacral spinal cords of 14.5‐day gestation mice (E14.5) were ablated. The number of molecules of each of the four myogenic regulatory factor (MRF) mRNAs per nanogram of total RNA were evaluated in innervated and aneural fetal crural muscles. Accumulation of all four MRF mRNAs was affected in aneural muscle, but was never more than threefold different than in innervated muscles, considerably less than after adult denervation. The effect of the nerve varied with the MRF, the fetal age, and with the muscle (extensor digitorum longus muscle [EDL] vs. soleus muscle), with the nerve having multiple effects including down‐regulation of certain MRF genes at specific periods (e.g., myoD and myogenin [E16.5–E18.5] and MRF4 in the EDL only [E18.5–E19.5]); limiting the up‐regulation of certain genes, which occurred in the absence of innervation (e.g., myf‐5 [E18.5–E19.5] and myogenin [E14.5–E16.5]); and even enhancing the accumulation of MRF4 mRNA (E14.5–E16.5). We hypothesize that factors other than nerve contribute to the down‐regulation of myf‐5 and myogenin mRNAs to adult levels. Innervation was required for the emergence of the slow, but not the fast, MRF mRNA profile at birth. MyoD, found in both the nuclear and cytoplasmic protein extracts of innervated fetal muscle, increased by ∼5‐fold in the nuclear extracts (∼2.5‐fold in the cytoplasmic) of E19.5 aneural muscles, significantly less than the 12‐fold increase found in the nuclear extract of 4‐day denervated adult muscle. This increase in aneural fetal muscle was due primarily to an increased concentration of myoD in muscle lineage nuclei, rather than to the presence of additional myoD+ muscle lineage nuclei. Developmental Dynamics 236:732–745, 2007. © 2007 Wiley‐Liss, Inc.
Expression of Cre recombinase in early diploid trophoblast cells of the mouse placenta
Authors: Wenzel Pamela L. , Leone Gustavo
Published: February 2007

An increasing number of genes known to be critical for cell cycle control, differentiation, and tumor suppression have been found to impact development of the placenta. To elucidate how these genes contribute to development of embryonic and extra‐embryonic lineages, we generated a transgenic mouse in which the Cre transgene is driven by placenta‐specific regulatory sequences from the human CYP19 gene. Using ROSA26 conditional reporter mice, we could detect expression of the CYP19‐Cre transgene throughout the extra‐embryonic ectoderm and in the ectoplacental cone at embryonic day 6.5 (E6.5). By E11.5, recombination of LoxP reporter sites was detected in all derivatives of trophoblast stem cells, including spongiotrophoblast, giant cells, and labyrinth trophoblasts. We conclude that the CYP19‐Cre transgenic mouse developed here can be used in combination with conditional alleles to distinguish between embryonic and extra‐embryonic gene function, and to begin to map the period of time when gene function is critical during development. genesis 45:129–134, 2007. © 2007 Wiley‐Liss, Inc.
The B lineage potential of thymus settling progenitors is critically dependent on mouse age
Authors: Ceredig Rhodri , Bosco Nabil , Rolink Antonius G.
Published: February 2007

The nature and lineage potential, particularly that for B cells, of thymus settling progenitors (TSP) in the adult mouse has been the subject of considerable debate. Lack of B cell potential would suggest pre‐thymic, whereas its presence would suggest intra‐thymic loss of B cell potential. Using limiting dilution analysis (LDA) in vitro and transfer experiments in vivo, we show that the B cell potential of TSP is critically dependent on mouse age, reaching a maximum of about 1 in 20 cells at birth, decreasing 50‐fold in adult mice. Cells with a TSP phenotype can be found in the neonatal blood. Furthermore, using LDA, we show that Notch ligand signaling of TSP results in the loss of B cell potential with a half‐life of approximately 12 h. Taken together, these results indicate that loss of B cell potential by TSP is an intra‐thymic event and highlight the developmental pressure acting on the immune system to rapidly colonize primary lymphoid organs with functional progenitors. This critical time coincides with birth in the mouse. In the adult mouse, we estimate than only about 5 TSP cells/day would be required to maintain steady‐state thymopoiesis.
Potent T cell agonism mediated by a very rapid TCR/pMHC interaction
Authors: Boulter Jonathan M. , Schmitz Nicole , Sewell Andrew K. , Godkin Andrew J. , Bachmann Martin F. , Gallimore Awen M.
Published: February 2007

The interaction between T cell receptors (TCR) and peptide‐major histocompatibility complex (pMHC) antigens can lead to varying degrees of agonism (T cell activation), or antagonism. The P14 TCR recognises the lymphocytic choriomeningitis virus (LCMV)‐derived peptide, gp33 residues 33–41 (KAVYNFATC), presented in the context of H‐2Db. The cellular responses to various related H‐2Db peptide ligands are very well characterised, and P14 TCR‐transgenic mice have been used extensively in models of virus infection, autoimmunity and tumour rejection. Here, we analyse the binding of the P14 soluble TCR to a broad panel of related H‐2Db‐peptide complexes by surface plasmon resonance, and compare this with their diverse cellular responses. P14 TCR binds H‐2Db‐gp33 with a KD of 3 µM (±0.5 µM), typical of an immunodominant antiviral TCR, but with unusually fast kinetics (koff = 1 s–1), corresponding to a half‐life of 0.7 s at 25°C, outside the range previously observed for murine agonist TCR/pMHC interactions. The most striking feature of these data is that a very short half‐life does not preclude the ability of a TCR/pMHC interaction to induce antiviral immunity, autoimmune disease and tumour rejection.
Intra‐ and Intermolecular H···Cl–Ni Bonding Patterns in a Series of Highly Preorganized Dinuclear Nickel(II) Complexes
Authors: Nie Feng‐Mei , Leibeling Guido , Demeshko Serhiy , Dechert Sebastian , Meyer Franc
Published: February 2007

Four dinickel complexes [L1Ni2(μ‐Cl)(Cl)2]·2CH3OH (1a), [L1Ni2(μ‐Cl)(CH3OH)](ClO4)2 (1b), [L2Ni2(μ‐Cl)Cl2(H2O)2]·H2O (2) and [L3Ni2Cl2(CH3OH)2]Cl·2CH3OH (3) were synthesized and structurally characterized. The ligand scaffolds have a central pyrazolato bridge and N‐donor chelate arms that provide two proximate binding pockets for the nickel ions. While the longer ligand side arms in 1a, 1b and 2 induce Ni···Ni distances of around 4.0 Å and favour incorporation of a chlorido bridge within the dimetallic pocket, a stretched Ni···Ni separation of 4.6 Å with an unusual intramolecular Cl···H–O linkage is observed in 3. Various Cl···H–O hydrogen‐bonding motifs are identified in the solid‐state structures of 1–3, where either the H‐donor (MeOH or H2O) or the H‐acceptor (chlorido) or both are bound to a nickel ion, and their relative donor–acceptor distances are discussed. Magnetic coupling mediated through the pyrazolato and chlorido bridges is rather weak and antiferromagnetic, but it is even weaker for the Cl···H–O linkage. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Octahedral Metal Clusters [Nb6Cl12(CN)6]4– as Molecular Building Blocks: From Supramolecular Assemblies to Coordination Polymers
Authors: Zhou Huajun , Lachgar Abdessadek
Published: February 2007

There are considerable advantages for using metal clusters as building units of supramolecular materials because of their unique structural, chemical, and physical properties, all of which fall in between normal valence compounds and the metals. In this microreview, we describe the synthetic methodology and structural properties of recent findings in the use of octahedral niobium hexacyanochloride anions as building units of assemblies of different size, charge, and dimensionality. We focus on the use of a metal‐directed approach to prepare cluster‐based supramolecular assemblies and coordination polymers with one‐, two‐, and three‐dimensional frameworks. The materials described herein are all built from diamagnetic cyanochloride cluster anions [Nb6Cl12(CN)6]4– and coordinatively unsaturated metal complexes such as [Mn(salen)]+ and their derivatives. The overall structures are largely determined by the number of coordination sites available for linkage to the cluster unit and coordination preferences of the metal complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Suitable cooling program for chicken fat dry fractionation
Authors: Arnaud Elodie , Pina Michel , Collignan Antoine
Published: February 2007

The impacts of the cooling program on crystal morphology, crystal suspension filtration properties and the characteristics of fractions resulting from chicken fat dry fractionation were assessed. The quality of the fractions was found to depend on the nature of the crystallized material and was also closely related to the filtration properties of the crystal suspension, which in turn were controlled by the cooling conditions. A slow cooling rate during the nucleation step was necessary to enhance process selectivity, and this rate could be accelerated once the first crystals had formed. These findings enhanced our understanding of the mechanisms involved during dry fractionation and highlighted the efficacy of a three‐phase cooling program, including (1) cooling from 70 to 26 °C, (2) slowdown in the cooling rate, and (3) a second rapid cooling down to the final temperature at which the fat is held for a specified time.
Effect of chemical interesterification on triacylglycerol and solid fat contents of palm stearin, sunflower oil and palm kernel olein blends
Authors: Dian Noor Lida Habi Mat , Sundram Kalyana , Idris Nor Aini
Published: February 2007

Palm stearin (POs) with an iodine value of 41.4, sunflower oil (SFO) and palm kernel olein (PKOo) were blended in various ratios according to a three‐component mixture design and subjected to chemical interesterification (CIE). Triacylglycerol (TAG) and solid fat content (SFC) profiles of the chemically interesterified (CIEed) blends were analyzed and compared with those of the corresponding non‐CIEed blends. Upon CIE, extensive rearrangement of fatty acids (FA) among TAG was evident. The concentrations of several TAG were increased, some decreased and several new TAG might also have been formed. The changes in the TAG profiles were reflected in the SFC profiles of the blends. The SFC of the CIEed blends, except the binary blends of POs/PKOo which experienced an increase in SFC following CIE, revealed that they were softer than their respective starting blends. Randomization of FA distribution within and among TAG molecules of POs and PKOo led to a modification in TAG composition of the POs/PKOo blends and improved miscibility between the two fats, and consequently diminished the eutectic interaction that occurred between POs and PKOo.
Lipid extraction from the microalga Phaeodactylum tricornutum
Authors: Fajardo Antonio Ramírez , Cerdán Luis Esteban , Medina Alfonso Robles , Fernández Fracisco Gabriel Acién , Moreno Pedro A. González , Grima Emilio Molina
Published: February 2007

Ethanol was used for the extraction and purification of lipids from the biomass of the microalga Phaeodactylum tricornutum. This microalga is an oil‐rich substrate with a high proportion of eicosapentaenoic acid (EPA). The process consisted of two steps. First, ethanol (96% vol/vol) was used to extract the lipids from the lyophilized biomass. Second, a biphasic system was formed by adding water and hexane to the extracted crude oil. In this way, most of the lipids were transferred to the hexanic phase while most impurities remained in the hydroalcoholic phase. The first step was carried out by two consecutive extractions at room temperature, each with 5 mL ethanol per gram of biomass, for 10 and 1.25 h, respectively. Under these conditions, over 90% of the saponifiable lipids in the biomass were extracted. In the second step, the percentage of water in the hydroalcoholic phase, the hexane/hydroalcoholic phase ratio and the number of extraction steps were optimized. A water content of 40% vol/vol in the hydroalcoholic phase provided the highest lipid recovery. A recovery yield of 80% was obtained by four consecutive extractions with a hexane/hydroalcoholic phase ratio of 0.2 (vol/vol). Equilibrium distribution data of the lipids between the hydroethanolic and the hexanic phases were also obtained in order to predict the lipid recovery yield of the extraction. This process is an alternative to the traditional methods of lipid extraction, which uses less toxic solvents and reduces the total amount of solvents used.
Dual‐Amplification of Antigen–Antibody Interactions via Backfilling Gold Nanoparticles on (3‐Mercaptopropyl) Trimethoxysilane Sol‐Gel Functionalized Interface
Authors: An Haizhen , Yuan Ruo , Tang Dianping , Chai Yaqin , Li Na
Published: February 2007

A new dual‐amplification strategy of electrochemical signaling from antigen–antibody interactions was proposed via backfilling gold nanoparticles on (3‐mercaptopropyl) trimethoxysilane sol‐gel (MPTS) functionalized interface. The MPTS was employed not only as a building block for the electrode surface modification but also as a matrix for ligand functionalization with first amplification. The second signal amplification strategy introduced in this study was based on the backfilling immobilization of nanogold particles to the immunosensor surface. Several coupling techniques, such as with nanogold but not MPTS or with MPTS but not nanogold, were investigated for the determination of carcinoembryonic antigen (CEA) as a model, and a very good result was obtained with nanogold and MPTS coupling immunosensor. With the noncompetitive format, the formation of the antigen–antibody complex by a simple one‐step immunoreaction between the immobilized anti‐CEA and CEA in sample solution introduced membrane potential change before and after the antigen–antibody interaction. Under optimal conditions, the proposed immunosensor exhibited a good electrochemical behavior to CEA in a dynamic concentration range of 4.4 to 85.7 ng/mL with a detection limit of 1.2 ng/mL (at 3 δ). Moreover, the precision, reproducibility and stability of the as‐prepared immunosensor were acceptable. Importantly, the proposed methodology would be valuable for diagnosis and monitoring of carcinoma and its metastasis.
Stereoselective determination of hydroxychloroquine and its metabolites in human urine by liquid‐phase microextraction and CE
Authors: de Oliveira Anderson Rodrigo Moraes , Cardoso Carmen Dickow , Bonato Pierina Sueli
Published: February 2007

Liquid‐phase microextraction based on polypropylene hollow fibers and CE were applied for the chiral determination of hydroxychloroquine (HCQ) and its metabolites (desethylchloroquine, DCQ; desethylhydroxychloroquine, DHCQ; bisdesethylchloroquine, BDCQ) in human urine. The analytes were extracted from 3 mL of urine spiked with the internal standard (metoprolol) and alkalinized with 250 μL of 2 M NaOH. The analytes were extracted into 1‐octanol impregnated in the pores of the hollow fiber, and into an acid acceptor solution inside the hollow fiber. The electrophoretic separations were carried out in 100 mmol/L Tris buffer (pH adjusted to 9.0 with phosphoric acid) containing 1% w/v S‐β‐CD and 30 mg/mL HP‐β‐CD with a constant voltage of +18 kV. The method was linear over the concentration range of 10–1000 ng/mL for each HCQ stereoisomer and 21–333 ng/mL for each metabolite stereoisomer. Within‐day and between‐day assay precision and accuracy for the analytes were studied at three concentration levels for each stereoisomer and were lower than 15%. The developed method was applied for the determination of the cumulative urinary excretion of HCQ, DCQ, and DHCQ after oral administration of rac‐HCQ to a health volunteer. The results obtained are in agreement with previous literature data.
Pseudodynamic response of torsionally unbalanced two‐storey test structure
Authors: Bousias S. N. , Fardis M. N. , Spathis A.‐L. , Kosmopoulos A. J.
Published: February 2007

Two one‐way eccentric, two‐storey, one‐by‐one‐bay reinforced concrete (RC) structures are pseudodynamically tested under unidirectional ground motions. Theoretical considerations about the effect of torsional coupling on modal periods and shapes agree with modal results of the test structure, considering member stiffness is equal to the secant stiffness to yielding in skew‐symmetric bending. Modal periods of such an elastic structure are in fair agreement with effective periods inferred from the measured response at the beginning of a test of a thoroughly cracked structure and at the end of the test. A time‐varying stiffness matrix and a non‐proportional damping matrix fitted to the test results may be used to reproduce the measured response approximately by modal superposition and identify the role of the four time‐varying modes. Flexible side columns sustained very large drift demands simultaneously in the two transverse directions and suffered significant but not heavy, damage at lap‐splices. RC‐jacketing of the flexible side columns practically eliminated the static eccentricity between the floor centres of twist and mass as well as the torsional response. Inelastic time‐history analysis with point‐hinge member models, using as elastic stiffness the secant stiffness to yielding and neglecting post‐ultimate‐strength cyclic degradation of resistance in members with plain bars and poor detailing, predicted fairly well the response until the peak displacements and member deformations occurred. After that, it underestimated displacement peaks and the lengthening of the apparent period and missed the gradual drifting of the response towards a permanent offset. Copyright © 2007 John Wiley & Sons, Ltd.
Equivalent force control method for generalized real‐time substructure testing with implicit integration
Authors: Wu Bin , Wang Qianying , Benson Shing P. , Ou Jinping
Published: February 2007

This paper presents a new method, called the equivalent force control method, for solving the nonlinear equations of motion in a real‐time substructure test using an implicit time integration algorithm. The method replaces the numerical iteration in implicit integration with a force‐feedback control loop, while displacement control is retained to control the motion of an actuator. The method is formulated in such a way that it represents a unified approach that also encompasses the effective force test method. The accuracy and effectiveness of the method have been demonstrated with numerical simulations of real‐time substructure tests with physical substructures represented by spring and damper elements, respectively. The method has also been validated with actual tests in which a Magnetorheological damper was used as the physical substructure. Copyright © 2007 John Wiley & Sons, Ltd.
Mobile radio bi‐dimensional large‐scale fading modelling with site‐to‐site cross‐correlation
Authors: Fraile Rubén , Monserrat José F. , Gozálvez Javier , Cardona Narcís
Published: February 2007

Wireless communication simulations are generally conducted using one‐dimensional models for large‐scale fading. While simple and with low computational costs, these models cannot produce correlated fading values for mobiles that are in nearby positions. To overcome this limitation, this paper presents a novel bi‐dimensional large‐scale fading model which introduces the spatial correlation present in real systems. Besides, it is also able to model the non‐negligible cross‐correlation among signals coming from different sites. Copyright © 2007 John Wiley & Sons, Ltd.
A simplified v2–f model for near‐wall turbulence
Authors: Rahman M. M. , Siikonen T.
Published: February 2007

A simplified version of the v2–f model is proposed that accounts for the distinct effects of low‐Reynolds number and near‐wall turbulence. It incorporates modified Cε(1,2) coefficients to amplify the level of dissipation in non‐equilibrium flow regions, thus reducing the kinetic energy and length scale magnitudes to improve prediction of adverse pressure gradient flows, involving flow separation and reattachment. Unlike the conventional v2–f, it requires one additional equation (i.e. the elliptic equation for the elliptic relaxation parameter fµ) to be solved in conjunction with the k–ε model. The ${\bar{v}}^2$ scaling is evaluated from k in collaboration with an anisotropic coefficient Cv and fµ. Consequently, the model needs no boundary condition on ${\bar{v}}^2$ and avoids free stream sensitivity. The model is validated against a few flow cases, yielding predictions in good agreement with the direct numerical simulation (DNS) and experimental data. Copyright © 2007 John Wiley & Sons, Ltd.
Acoustic upwinding for sub‐ and super‐sonic turbulent channel flow at low Reynolds number
Authors: de Lange H. C.
Published: February 2007

A recently developed asymmetric implicit fifth‐order scheme with acoustic upwinding for the spatial discretization for the characteristic waves is applied to the fully compressible, viscous and non‐stationary Navier–Stokes equations for sub‐ and super‐sonic, mildly turbulent, channel flow (Reτ=360). For a Mach number of 0.1, results are presented for uniform (323, 643 and 1283) and non‐uniform (expanding wall‐normal, 323 and 643) grids and compared to the (incompressible) reference solution found in (J. Fluid. Mech. 1987; 177:133–166). The results for uniform grids on 1283 and 643 nodes show high resemblance with the reference solution. Expanding grids are applied on 643‐ and 323‐node grids. The capability of the proposed technique to solve compressible flow is first demonstrated by increasing the Mach number to 0.3, 0.6 and 0.9 for isentropic flow on the uniform 643‐grid. Next, the flow speed is increased to Ma=2. The results for the isothermal‐wall supersonic flows give very good agreement with known literature results. The velocity field, the temperature and their fluctuations are well resolved. This means that in all presented (sub‐ and super‐sonic) cases, the combination of acoustic upwinding and the asymmetric high‐order scheme provides sufficient high wave‐number damping and low wave‐number accuracy to give numerically stable and accurate results. Copyright © 2007 John Wiley & Sons, Ltd.
The pricing of electricity futures: Evidence from the European energy exchange
Authors: Wilkens Sascha , Wimschulte Jens
Published: February 2007

This study investigates the pricing of electricity futures at the European Energy Exchange (EEX) over the period 2002 through 2004. To calculate theoretical contract values, the reduced‐form models of J. J. Lucia and E. S. Schwartz (2002) are used, and a thorough empirical analysis by means of an out‐of‐sample test is conducted for both one‐ and two‐factor models, incorporating a constant non‐zero price of risk. Although the models are proven to capture all basic spot market characteristics and provide an accurate in‐the‐sample fit to observed futures prices, the forecasting performance is subject to biases. For instance, it was found that the relative mispricing depends on both the spot price level and the remaining time‐to‐maturity of the futures contracts. © 2007 Wiley Periodicals, Inc. Jrl Fut Mark 27:387–410, 2007
The information content of implied volatility in light of the jump/continuous decomposition of realized volatility
Authors: Giot Pierre , Laurent Sébastien
Published: February 2007

In the framework of encompassing regressions, the information content of the jump/continuous components of historical volatility is assessed when implied volatility is included as an additional regressor. The authors' empirical application focuses on daily and intradaily data for the S&P100 and S&P500 indexes, and daily data for the associated VXO and VIX implied volatility indexes. The results show that the total explanatory power of the encompassing regressions barely changes when the jump/continuous components are included, although the weekly and monthly continuous components are usually significant. This evidence supports the view that implied volatility has very high information content, even when extended decompositions of past realized volatility are used. Moreover, adding GARCH‐type volatility forecasts in the regressions confirms these results. © 2007 Wiley Periodicals, Inc. Jrl Fut Mark 27:337–359, 2007
Involvement of P2X4and P2Y12receptors in ATP‐induced microglial chemotaxis
Authors: Ohsawa Keiko , Irino Yasuhiro , Nakamura Yasuko , Akazawa Chihiro , Inoue Kazuhide , Kohsaka Shinichi
Published: February 2007

We previously reported that extracellular ATP induces membrane ruffling and chemotaxis of microglia and suggested that their induction is mediated by the Gi/o‐protein coupled P2Y12receptor (P2Y12R). Here we report discovering that the P2X4receptor (P2X4R) is also involved in ATP‐induced microglial chemotaxis. To understand the intracellular signaling pathway downstream of P2Y12R that underlies microglial chemotaxis, we examined the effect of two phosphatidylinositol 3′‐kinase (PI3K) inhibitors, wortmannin, and LY294002, on chemotaxis in a Dunn chemotaxis chamber. The PI3K inhibitors significantly suppressed chemotaxis without affecting ATP‐induced membrane ruffling. ATP stimulation increased Akt phosphorylation in the microglia, and the increase was reduced by the PI3K inhibitors and a P2Y12R antagonist. These results indicate that P2Y12R‐mediated activation of the PI3K pathway is required for microglial chemotaxis in response to ATP. We also found that the Akt phosphorylation was reduced when extracellular calcium was chelated, suggesting that ionotropic P2X receptors are involved in microglial chemotaxis by affecting the PI3K pathway. We therefore tested the effect of various P2X4R antagonists on the chemotaxis, and the results showed that pharmacological blockade of P2X4R significantly inhibited it. Knockdown of the P2X4receptor in microglia by RNA interference through the lentivirus vector system also suppressed the microglial chemotaxis. These results indicate that P2X4R as well as P2Y12R is involved in ATP‐induced microglial chemotaxis. © 2007 Wiley‐Liss, Inc.
Variations in sediment sources and yields in the Finger Lakes and Catskills regions of New York
Authors: Nagle Gregory N. , Fahey Timothy J. , Ritchie Jerry C. , Woodbury Peter B.
Published: February 2007

The proportional contributions of stream bank and surface sources to fine sediment loads in watersheds in New York State were quantified with uncertainty analysis. Eroding streamside glacial drift, including glaciolacustrine deposits, were examined to help explain variations in the proportional contributions made by bank erosion. Sediment sources were quantified by comparing concentrations of the bomb‐derived radionuclide 137Cs in fluvial sediment with sediment from potential source areas such as agricultural soils, forest soils and stream banks.

To compare sediment sources in streams containing abundant deposits of fine‐grained glacial drift with watersheds that lacked moderate or extensive streamside deposits, samples were taken from 15 watersheds in the region. The mean contribution of bank erosion to sediment loads in the six streams with glaciolacustrine deposits was 60% (range 46–76%). The proportional contribution of bank erosion was also important in one stream lacking glaciolacustrine deposits (57%) but was less important in the remainder, with contributions ranging from 0 to 46%. Data from this study on the varying contributions of bank erosion and data from past studies of sediment yield in 15 watersheds of New York State suggest that eroding streamside glacial deposits dominate sediment yield in many watersheds. In other watersheds, past impacts to streams, such as channelization, have also resulted in high levels of bank erosion. Copyright © 2007 John Wiley & Sons, Ltd.
Gaussian induced dipole polarization model
Authors: Elking Dennis , Darden Tom , Woods Robert J.
Published: February 2007

A new induced dipole polarization model based on interacting Gaussian charge densities is presented. In contrast to the original induced point dipole model, the Gaussian polarization model is capable of finite interactions at short distances. Aspects of convergence related to the Gaussian model will be explored. The Gaussian polarization model is compared with the damped Thole‐induced dipole model and the point dipole model. It will be shown that the Gaussian polarization model performs slightly better than the Thole model in terms of fitting to molecular polarizability tensors. An advantage of the model based on Gaussian charge distribution is that it can be easily generalized to other multipole moments and provide effective damping for both permanent electrostatic and polarization models. Finally, a method of parameterizing polarizabilities is presented. This method is based on probing a molecule with point charges and fitting polarizabilities to electrostatic potential. In contrast to the generic atom type polarizabilities fit to molecular polarizability tensors, probed polarizabilities are significantly more accurate in terms of reproducing molecular polarizability tensors and electrostatic potential, while retaining conformational transferability. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
Wavelet transform analysis of ab initio molecular dynamics simulation: Application to core‐excitation dynamics of BF3
Authors: Otsuka Takao , Nakai Hiromi
Published: February 2007

We propose a novel analysis method of ab initio molecular dynamics (AIMD) simulation using a continuous wavelet transform (c‐WT) technique. The c‐WT technique, one of the time‐frequency signal analysis methods, provides a clear view of the dynamical information in time developments. Combined with the auto‐correlation function of velocity by AIMD simulation, c‐WT analysis enables us to well understand dynamical distribution, such as the vibrational properties following a change of electronic structure in a molecular system. As a practical application, AIMD simulation of core‐excited BF3 (B1s → 2a) is illustrated. AIMD simulation leads to the change of vibrational motion as well as structural deformation by core‐excitation. The c‐WT analysis clarifies the relationship between structural deformation and the related significant vibrational modes in core‐excitation within 50 fs. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
Combined DFT, QCISD(T), and G2 mechanism investigation for the reactions of carbon monophosphide CP with unsaturated hydrocarbons allene CH2CCH2 and methylacetylene CH3CCH
Authors: Zhao YAn‐Li , Kan Wei , Zhong Hua , Yu Hai‐Tao , Fu Hong‐Gang
Published: February 2007

The possible reaction product distribution and mechanism of carbon monophosphide CP with unsaturated hydrocarbons allene CH2CCH2 and methylacetylene CH3CCH are investigated at the B3LYP/6‐311+G(d,p), QCISD(T)/6‐311++G(2df,2p), and G2 levels of theory. Corresponding reactants, products, intermediates, and interconversion and dissociation transition states are located on the reaction potential energy profiles. Computation results show that in the reaction of CP with CH2CCH2 the dominant reaction product should be species CH2CCHCP. Also, we can suggest species HCCCH2CP as a secondary reaction product despite of only minor contribution to reaction products. In the reaction of CP with CH3CCH, the primary and secondary products are suggested to be two important molecules HCCCP and CH3CCCP, respectively. The predicted mechanisms for the two reactions are not in parallel with the reactions of CN with allene CH2CCH2 and methylacetylene CH3CCH given in previous studies. The present calculations provide some useful information for future possible experimental isolation and observation for some interesting unsaturated carbon–phosphorus‐bearing species. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
Global minimum structure searches via particle swarm optimization
Authors: Call Seth T. , Zubarev Dmitry Yu. , Boldyrev Alexander I.
Published: February 2007

Novel implementation of the evolutionary approach known as particle swarm optimization (PSO) capable of finding the global minimum of the potential energy surface of atomic assemblies is reported. This is the first time the PSO technique has been used to perform global optimization of minimum structure search for chemical systems. Significant improvements have been introduced to the original PSO algorithm to increase its efficiency and reliability and adapt it to chemical systems. The developed software has successfully found the lowest‐energy structures of the LJ26 Lennard‐Jones cluster, anionic silicon hydride Si2H, and triply hydrated hydroxide ion OH− (H2O)3. It requires relatively small population sizes and demonstrates fast convergence. Efficiency of PSO has been compared with simulated annealing, and the gradient embedded genetic algorithm. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
A semiempirical approach to the intra‐phycocyanin and inter‐phycocyanin fluorescence resonance energy‐transfer pathways in phycobilisomes
Authors: Matamala Adelio R. , Almonacid Daniel E. , Figueroa Maximiliano F. , Martínez‐oyanedel JosÉ , Bunster Marta C.
Published: February 2007

A semiempirical methodology to model the intra‐phycocyanin and inter‐phycocyanin fluorescence resonance energy‐transfer (FRET) pathways in the rods of the phycobilisomes (PBSs) from Fremyella diplosiphon is presented. Using the Förster formulation of FRET and combining experimental data and PM3 calculation of the dipole moments of the aromatic portions of the chromophores, transfer constants between pairs of chromophores in the phycocyanin (PC) structure were obtained. Protein docking of two PC hexamers was used to predict the optimal distance and axial rotation angle for the staked PCs in the PBSs' rods. Using the distance obtained by the docking process, transfer constants between pairs of chromophores belonging to different PC hexamers were calculated as a function of the angle of rotation. We show that six preferential FRET pathways within the PC hexameric ring and 15 pathways between hexamers exist, with transfer constants consistent with experimental results. Protein docking predicted the quaternary structure for PCs in rods with inter‐phycocyanin distance of 55.6 Å and rotation angle of 20.5°. The inter‐phycocyanin FRET constant between chromophores at positions β155 is maximized at the rotation angle predicted by docking revealing the crucial role of this specific inter‐phycocyanin channel in defining the complete set of FRET pathways in the system. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
Array files for computational chemistry: MP2 energies
Authors: Ford Alan R. , Janowski Tomasz , Pulay Peter
Published: February 2007

A simple message‐passing implementation for distributed disk storage, called array files (AF), is described. It is designed primarily for parallelizing computational chemistry applications but it should be useful for any application that handles large amounts of data stored on disk. AF allows transparent distributed storage and access of large data files. An AF consists of a set of logically related records, i.e., blocks of data. It is assumed that the records have the typical dimension of matrices in quantum chemical calculations, i.e., they range from 0.1 to ∼32 MB in size. The individual records are not striped over nodes; each record is stored on a single node. As a simple application, second‐order Møller‐Plesset (MP2) energies have been implemented using AF. The AF implementation approaches the efficiency of the hand‐coded program. MP2 is relatively simple to parallelize but for more complex applications, such as Coupled Cluster energies, the AF system greatly simplifies the programming effort. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007.
Effect of surrounding point charges on the density functional calculations of NixOx clusters (x = 4–12)
Authors: Kadossov Evgueni B. , Gaskell Karen J. , Langell Marjorie A.
Published: February 2007

Embedded NixOx clusters (x = 4–12) have been studied by the density‐functional method using compensating point charges of variable magnitude to calculate the ionic charge, bulk modulus, and lattice binding energy. The computations were found to be strongly dependent on the value of the surrounding point charge array and an optimum value could be found by choosing the point charge to reproduce the experimentally observed NiO lattice parameter. This simple, empirical method yields a good match between computed and experimental data, and even small variation from the optimum point charge value produces significant deviation between computed and measured bulk physical parameters. The optimum point charge value depends on the cluster size, but in all cases is significantly less than ±2.0, the formal oxidation state typically employed in cluster modeling of NiO bulk and surface properties. The electronic structure calculated with the optimized point charge magnitude is in general agreement with literature photoemission and XPS data and agrees with the presently accepted picture of the valence band as containing charge‐transfer insulator characteristics. The orbital population near the Fermi level does not depend on the cluster size and is characterized by hybridized Ni 3d and O 2p orbitals with relative oxygen contribution of about 70%. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
Agonist‐induced calcium entry correlates with STIM1 translocation
Authors: Ross Kehinde , Whitaker Michael , Reynolds Nick J.
Published: February 2007

The mechanisms of agonist‐induced calcium entry (ACE) following depletion of intracellular calcium stores have not been fully established. We report here that calcium‐independent phospholipase A (iPLA2) is required for robust Ca2+ entry in HaCaT keratinocytes following ATP or UTP stimulation. Lysophosphatidic acid (LPA), an unrelated agonist, evoked Ca2+ release without inducing robust Ca2+ entry. Both LPA and UTP induced the redistribution of STIM1 into puncta which localized to regions near or at the plasma membrane, as well as within the cytoplasm. Plasma membrane‐associated STIM1 remained high for up to 10 min after UTP stimulation, whereas it had returned almost to baseline by that time point in LPA‐stimulated cells. This correlated with faster reloading of the endoplasmic reticulum Ca2+ stores in LPA treated cells. Thus by differentially regulating store‐refilling after agonist‐mediated depletion, LPA and UTP may exert distinct effects on the duration of STIM1 localization at the plasma membrane, and thus, on the magnitude and duration of ACE. J. Cell. Physiol. 211: 569–576, 2007. © 2007 Wiley‐Liss, Inc.
Development of the osteocranium in the suckermouth armored catfish Ancistrus cf. triradiatus (Loricariidae, siluriformes)
Authors: Geerinckx Tom , Brunain Marleen , Adriaens Dominique
Published: February 2007

The development of the osteocranium of the suckermouth armored catfish Ancistrus cf. triradiatus is described based on specimens ranging from prehatching stages to juvenile stages where the osteocranium is more or less fully formed. The first bony elements that arise are the opercle, jaws, and lateralmost branchiostegal rays, as well as the basioccipital and parasphenoid in the skull floor. The supracleithrum and the membranous and perichondral pterotic components form one large, double‐layered skull bone during ontogeny, without clear evidence of the involvement of a supratemporal. The Baudelot's ligament ossifies from two sides, i.e., from the basioccipital medially and the supracleithrum laterally. The lower jaw consists of a dentary, mentomeckelian, and angulo‐articular, which all soon fuse. The parurohyal, formed by the fusion of a ventral sesamoid bone and a dorsal cartilage element associated with the first basibranchial, is pierced by a vein, unlike in some other siluriforms. The interhyal cartilage disappears during ontogeny; medially of it, a small sesamoid bone appears in a ligament. The largest, canal‐bearing cheek plate is not homologous to the interopercle. The results of the present research, with emphasis on bone formations and homologies, are compared with studies on related catfishes. J. Morphol., 2007. © 2007 Wiley‐Liss, Inc.
Complexes between some lysine‐containing peptides and crown ethers—electrospray ionization mass spectrometric study
Authors: Frański Rafał , Schroeder Grzegorz , Kamysz Wojciech , Niedzialkowski Pawel , Ossowski Tadeusz
Published: February 2007

The complexes between lysine‐containing peptides (M) and crown ethers (CEs, 18C6, 15C5, 12C4) have been studied by the electrospray ionization (ESI) mass spectrometry. The maximum number of CEs attached has been found to be the same as that of the alkyl‐amino side chains of lysine and as that of the protons attached. Examination of the breakdown plots of the abundances of the ions observed against the cone voltage (CV) has shown that mass spectrometric fragmentation pathways of [M + nH + (CE)n]+n may involve a loss of a neutral CE molecule as well as protonated one. The decrease in the CE cavity (the use of 12C4 or 15C5 instead of 18C6) leads to a dramatic lowering in the stability of the complexes in the gas phase but not in solution. Attachment of a CE to peptides increases their hydrophobicity, and therefore proceeds with lower efficiency in water than in methanol. Copyright © 2007 John Wiley & Sons, Ltd.
Characterization of a putative Xylella fastidiosa diffusible signal factor by HRGC‐EI‐MS
Authors: Colnaghi Simionato Ana Valéria , da Silva Denise Santos , Lambais Marcio Rodrigues , Carrilho Emanuel
Published: February 2007

Xylella fastidiosa (X.f.) is a plant pathogen with high levels of genomic similarity to Xanthomonas campestris pv. campestris (X.c.c.). It has been shown that X. fastidiosa synthesizes a putative diffusible signal factor (X.f.‐DSF) that activates regulation of pathogenicity factor (rpf) genes in a X.c.c. reporter system, which might be involved in the regulation of pathogenesis associated genes as in X.c.c., as well as in quorum‐sensing. The nature of the X.f.‐DSF is not known, whereas the X.c.c.‐DSF has been identified as cis‐11‐methyl‐2‐dodecenoic acid. In this work, the chemical nature of a putative X.f.‐DSF molecule, able to restore endoglucanase activity in a X.c.c. rpfF mutant, was investigated as if it was a fatty acid derivative. Bioassays with X.c.c. reporter bacterium and X.f. culture extracts, based on endoglucanase restoration activity, were also carried out in order to confirm the DSFs molecules similarities. For this reason, a gas chromatography–mass spectrometry method was developed with standard fatty acids methyl esters mixtures. The retention time, as well as the fragmentation patterns, of each standard was used to identify the DSF molecule synthesized by X.f. in the culture medium. Typical ester fragmentation patterns (the derivatized analyte) were observed, such as: McLafferty rearrangement and migration of the Hδ followed by 1,4‐hydrogen shift and cleavage of the bond CβCγ, confirming the nature of this molecule. This confirmation was corroborated by the common peaks in both spectra. Besides, the observed retention time reinforces our conclusion since it corresponds to a methyl ester with 15 carbons. Since the X.f.‐DSF molecule was tentatively identified as 12‐methyl‐tetradecanoic acid (by mass spectra library comparison), this standard compound was also analyzed, strongly suggesting that this is the identification of such a molecule. To our knowledge, this is the first time a DSF produced by X.f. has been characterized. Copyright © 2007 John Wiley & Sons, Ltd.