bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of RRR‐α‐ and all‐rac‐α‐tocopherol uptake by permanent rat skeletal muscle myoblasts (L6 cells): Effects of exogenous lipoprotein lipase
Authors: Nakamura Tetsuya , Reicher Helga , Sattler Wolfgang
Published: November 2006

The purpose of the present investigation was to test whether permanent skeletal muscle cells (rat L6 cells) could serve as an in vitro model for α‐tocopherol (αTocH) biodiscrimination studies. L6 cells were incubated in the presence of high density lipoprotein (HDL), low density lipoprotein (LDL), and very low density lipoprotein (VLDL) labeled in the lipid moiety with either all‐rac‐or RRR‐[14C]αTocH. These incubations were performed either in the absence or in the presence of exogenously added bovine lipoprotein lipase (LPL) since skeletal muscle is one of the major expression sites of LPL in vivo. Time‐dependent uptake studies (up to 24 h) in the absence of LPL have shown that equipotent doses of all‐rac‐ and RRR‐[14C]αTocH (1.36∶1) led to almost identical accumulation of the tracer, independent of the lipoprotein class used as αTocH carrier. With regard to αTocH donor capacity, it appeared that HDL is the most potent αTocH donor, followed by LDL and VLDL. In the presence of LPL, all‐rac‐ and RRR‐[14C]αTocH uptake was significantly enhanced (between two‐ and tenfold). Biodiscrimination studies using chiral high‐performance liquid chromatographic analysis with radiometric detection of the corresponding methyl ether derivatives on a Chiralcel OD column have demonstrated that the 2S‐and 2R‐isomers of αTocH were taken up in a 1∶1 ratio by L6 cells independent of the absence or presence of LPL. In addition, we have not observed biodiscrimination between the four 2R‐isomers, i.e., there was no preferential accumulation of the RRR‐isomer. These data suggest that L6 cells do not discriminate between different αTocH isomers and that the addition of endogenous LPL significantly enhances the uptake of RRR‐ and all‐rac‐αTocH.
Alterations in heart and kidney membrane phospholipids in hypertension as observed by 31P nuclear magnetic resonance
Authors: Chi Yuling , Gupta Raj K.
Published: November 2006

Abnormalities of phospholipids in hypertension have previously been described in human erythrocyte, platelet, and plasma lipoproteins. Since the heart and kidney are adversely affected by hypertension, we investigated possible alterations in their membrane phospholipids, which could play a role in the derangement of intracellular ion balance widely observed in hypertension. The phospholipid compositions of heart and kidney from spontaneously hypertensive rats (SHR) and Wistar‐Kyoto (WKY) rats were determined by using 31P nuclear magnetic resonance (NMR) spectroscopy. Absolute contents of all phospholipids in hypertensive hearts and kidneys were significantly higher than in normotensive hearts and kidneys. Expressed as a fraction of total phospholipid, cardiolipin (CL) and phosphatidylethanolamine plasmalogen (PEp) were significantly increased in SHR hearts compared to WKY hearts (CL and PEp were 7.95±0.22% and 13.16±0.35% in SHR vs. 7.01±0.20% and 11.19±0.42% in WKY rats, P<‐0.05), but phosphatidylethanolamine (PE) and phosphatidylcholine (PC) were significantly decreased in SHR (PE and PC were 22.46±0.37% and 44.81±0.43% in SHR vs. 24.02±0.44% and 46.01±0.50% in WKY rats, p≤0.05). In the phospholipids extracted from rat kidneys, the percentage of PE was significantly higher for SHR than for WKY rats (20.37±0.60% vs. 18.43±0.37%, P≤0.05), while PEp and phosphatidylserine (PS) were significantly lower for SHR (PEp and PS were 10.22±0.36% and 8.42 ±0.28% in SHRs vs. 11.29±0.36% and 9.71±0.40% in WKY rats, P≤0.05). The above alterations in phospholipid composition might contribute to the higher oxygen consumption in the hypertensive heart and abnormal intracellular ion concentrations and ion transport in the heart and the kidney in hypertension.
Apoptosis in raloxifene‐treated postmenopausal women
Authors: Biri A. , Yurtcu E. , Ciftci B. , Korucuoğlu Ü. , İlhan M.N. , Ergun M.A. , Gursoy R. , Biberoglu K.
Published: November 2006

As raloxifene is a mixed estrogen receptor agonist and antagonist, it exerts different effects on apoptosis in different tissues. In this study, we aimed to evaluate apoptosis in the peripheral lymphocytes of postmenopausal women treated with raloxifene and compare it with untreated control subjects. In this way, we expected to deduce some results about the effect of raloxifene on the immune system and to serve as a guide for future studies on this newly proposed effect of a well‐known agent. Twenty osteoporotic postmenopausal women treated with raloxifene for 12 months were included in this study. Another 20 osteoporotic postmenopausal women matched for age and postmenopausal years, but without any medication, were chosen as the control group. Apoptosis was evaluated using a morphological and DNA fragmentation assay, in the peripheral lymphocytes of these women. Our results revealed a decrease in the apoptosis percentages of the patients treated with raloxifene (14.6%) with respect to the control subjects (15.8%), but the difference was not statistically significant (p = 0.467). This study indicated that raloxifene treatment had no apoptotic effect on peripheral human lymphocytes compared to controls.
Nurses' Guide to the Internet
Authors: Hickey Pat
Published: November 2006

NURSES' GUIDE TO THE INTERNET, By Leslie H. Nicoll, Teena H. Ouellette 1997, 178 pp $32 paperback
Gemeinsame Manifestation von Blue-Rubber-Bleb-Naevus-Syndrom und malignem Melanom
Authors: Kinner  , Herborn  , Kroeger
Published: November 2006

Blue rubber bleb Nävi (BRBN) sind seltene, vaskuläre Malformationen, die sich an Haut und Schleimhäuten manifestieren. Über einen Zusammenhang dieser Nävi mit malignen Erkrankungen ist bislang wenig bekannt. Wir berichten über einen jungen Patienten mit BRBN Syndrom, bei dem neben einer Progredienz der Nävi ein malignes Melanom gefunden wurde.
Gastric predominant hereditary hemorrhagic telangiectasia
Authors: Katsinelos  , Chatzimavroudis  , Zavos  , Kamperis  , Triantafillidis  , Pilpilidis  , Katsinelos  , Papaziogas
Published: November 2006

Hereditary hemorrhagic telangiectasia (HHT) or Rendu-Osler-Weber disease is an autosomal-dominant disorder that frequently presents with epistaxis and gastrointestinal bleeding which may be a diagnostic and therapeutic challenge. We describe a 48-year-old monk with familiar history of HHT, who presented with frequent epistaxes and symptoms of ferropenic anemia. Upper gastrointestinal endoscopy revealed innumerable telangiectasias in the stomach. The patient underwent three sessions with argon plasma coagulation treatment but the results were poor. We also review the literature on the pathophysiology of the disease and discuss the suggested treatment.
Expected impact of an aged biomass burning aerosol on cloud condensation nuclei and cloud droplet concentrations
Authors: Lee Yong Seob , Collins Don R. , Li Runjun , Bowman Kenneth P. , Feingold Graham
Published: November 2006

During May of 2003, smoke from fires on the Yucatan Peninsula was transported across the Gulf of Mexico and into Texas where it caused a significant enhancement in measured aerosol concentrations. The 24‐hour average PM2.5 concentration measured in Austin on 10 May was 50.1 μg/m3, which was more than twice that of the highest daily average concentration measured during any other month in 2003. During this event, a differential mobility analyzer/tandem differential mobility analyzer (DMA/TDMA) system was used to characterize the size distribution and size‐resolved hygroscopicity and volatility of the aerosol. The hygroscopicity data were used to isolate the less hygroscopic biomass burning particles from other aerosol types. Biomass burning aerosol‐only size distributions were then constructed by coupling the size‐resolved fraction of particles attributed to the fires with the overall size distribution. These distributions, and the aerosol properties derived from the TDMA data, were used to examine the impact of the smoke on predicted cloud condensation nuclei (CCN) spectra. The influence of the smoke on cloud droplet concentrations and the influence of other aerosol types present on the activation efficiency of the smoke were evaluated using a cloud parcel model. For a subset of the updraft speeds considered, the model predicted that the cloud droplet concentration would sometimes be lower when both smoke and pollution aerosols entered cloud relative to that when only smoke was present. Whereas these cases in which an increased aerosol concentration resulted in a decreased cloud droplet concentration were rare, the inclusion of the pollution aerosol in the model always reduced the activation efficiency of the smoke aerosol, which would influence both its evolution during transport and its atmospheric removal rate.
Reproduction of time derivative of electromagnetic field associated with rocket‐triggered lightning in submicrosecond range
Authors: Miyazaki S. , Ishii M.
Published: November 2006

The time derivatives of the magnetic flux density and the electric field intensity associated with two rocket‐triggered lightning return strokes are reproduced in the submicrosecond range by using a transmission line type model. The proposed model is based on the detailed optical observation of the attachment process. In the proposed model, return stroke current waves propagate from the junction point of a connecting leader and a dart leader in the both upward and downward directions, respectively. Furthermore, reflections at ground and at the top of the strike rod are taken into account. The model incorporating the observed attachment process and the typical return stroke speed reproduces measured time derivatives of magnetic flux density and electric field intensity better than the models proposed so far.
Evaluation of the first‐order approximations for transport in heterogeneous media
Authors: Suciu N. , Vamoş C. , Eberhard J.
Published: November 2006

Longitudinal dispersion coefficients in given realizations of the transport computed by two currently used approximations of the first‐order in velocity variance are compared with accurate global random walk simulations. The comparisons are performed for the same ensemble of realizations of the Darcy velocity field, approximated by a quasiperiodic random field, for lognormal hydraulic conductivity with small variance and finite correlation lengths. The results show that at finite times of about one dispersion timescale, the mean coefficient is underestimated by ≈20%, and the fluctuations are overestimated by ≈80%. At larger times the errors decrease monotonously, and the first‐order approximations yield fairly good predictions for the mean and the fluctuations of the dispersion coefficient.
Shear wave splitting beneath the central Tien Shan and tectonic implications
Authors: Li Aibing , Chen Chizheng
Published: November 2006

Shear‐wave splitting analyses were performed at 30 seismic stations in the central Tien Shan and its vicinity. Fast orientation at most of the stations on the Tien Shan range is ENE‐WSW, parallel to the strike of the Tien Shan. It largely reflects a coherent deformation of the lithosphere in response to the NS shortening. Anisotropy with NNE‐SSW fast axes is observed within adjacent basins, around the Issyk Kul and near the northwestern Tarim, where the lithosphere is presumably strong, less deformed. The NNE‐SSW orientation, which coincides with the surface velocity of the central Tien Shan, can be best explained by shear between the lithosphere and asthenosphere on a regional scale rather than small‐scale convection as proposed in previous studies. The dextral Talasso‐Fergana fault seems to have little effect on anisotropy at its nearby stations, suggesting this fault is probably confined to the shallow part of the lithosphere.
Variation of tropical cyclone activity in the South Indian Ocean: El Niño–Southern Oscillation and Madden‐Julian Oscillation effects
Authors: Ho Chang‐Hoi , Kim Joo‐Hong , Jeong Jee‐Hoon , Kim Hyeong‐Seog , Chen Deliang
Published: November 2006

The present study examines variation of tropical cyclone (TC) activity in the South Indian Ocean (SIO) during TC seasons (December–March) for the period 1979–2004. The impact of the El Niño–Southern Oscillation and the Madden‐Julian Oscillation (MJO) on the variation is revealed through a composite analysis. During El Niño periods TC genesis was shifted westward, enhancing the formation west of 75°E and reducing it east of 75°E. These changes in the genesis correspond to a westward shift of convection. It may be explained by a remote effect on the SIO; that is, the increase in sea surface temperature in the central eastern Pacific alters the Walker circulation and forms an anomalous anticyclonic circulation in the east SIO during El Niño. The spatial difference in TC passages between El Niño and La Niña shows a significant decrease to the southeast of Madagascar but a moderate increase in the central midlatitude SIO, indicating that TCs move farther east during El Niño. This change is possibly due to the anomalous southwesterlies east of Madagascar. Variation of TC activity also depends on various MJO phases: frequent TC passages for phases 2–4 (strong convective activity straddles along the equatorial Indian Ocean) versus infrequent TC passages for other phases. TC tracks tend to be more south oriented in phase 3 compared with those in phases 2 and 4. This is possibly caused by the increased steering northerlies which are a part of the anticyclonic Rossby wave of Gill type in response to the suppressed MJO‐related convection in the maritime continent.
Woody encroachment effects on the calcareous prairie soils of Louisiana
Authors: Bekele Asfaw , Hudnall Wayne H. , Downer Robert G.
Published: November 2006

The calcareous prairies of Louisiana have been threatened by the encroachment of woody plants, primarily eastern red cedar (Juniperus virginiana). The knowledge of whether eastern red cedar encroachment has altered the soil chemical characteristics is of interest in light of the restoration and management of these rare plant communities. The objectives of this study were to investigate differences in soil nutrient levels among prairie, transition and forest soils and to determine which soil properties could be used to differentiate prairie soils from soils impacted by woody vegetation. We collected soil samples along transects traversing prairie, transition, and forest from three remnant calcareous prairies in Louisiana. We also measured relative elevation (RE) at the points where soil samples were taken. The transition was the area heavily encroached by red cedar. The soil samples were analyzed for pH, electrical conductivity (EC), and Mehlich III extractable nutrients. Factor analysis and stepwise discriminant analysis were used to determine differences in these soil properties among the vegetation types and to identify the soil properties that could be used to discriminate the soil types (prairie soil, transition soil and forest soil). The prairie soil was distinctly different from the forest soil in nutrient levels while the transition soil shared the properties of both the forest soil and the prairie soil but with a change toward the forest soil, indicating that eastern red cedar impacted the prairie soil. The discriminating soil and topographical attributes were pH, nutrients (Ca, Mg, Fe, and Mn) and RE. The discriminant functions derived from these attributes reasonably predicted the soil types and may be used as a predictive and classification tool in the effort to delineate similar prairie‐forest associations encroached upon by eastern red cedar. In addition, these findings provide land managers of natural areas, especially of humid regions, a better perspective on eastern red cedar impact on prairie soil nutrient levels.
Nonadiabatic effects in C–Br bond scission in the photodissociation of bromoacetyl chloride
Authors: Valero Rosendo , Truhlar Donald G.
Published: November 2006

Bromoacetyl chloride photodissociation has been interpreted as a paradigmatic example of a process in which nonadiabatic effects play a major role. In molecular beam experiments by Butler and co-workers [J. Chem. Phys. 95, 3848 (1991); J. Chem. Phys. 97, 355 (1992)], BrCH2C(O)Cl was prepared in its ground electronic state (S0) and excited with a laser at 248nm to its first excited singlet state (S1). The two main ensuing photoreactions are the ruptures of the C–Cl bond and of the C–Br bond. A nonadiabatic model was proposed in which the C–Br scission is strongly suppressed due to nonadiabatic recrossing at the barrier formed by the avoided crossing between the S1 and S2 states. Recent reduced-dimensional dynamical studies lend support to this model. However, another interpretation that has been given for the experimental results is that the reduced probability of C–Br scission is a consequence of incomplete intramolecular energy redistribution. To provide further insight into this problem, we have studied the energetically lowest six singlet electronic states of bromoacetyl chloride by using an ab initio multiconfigurational perturbative electronic structure method. Stationary points (minima and saddle points) and minimum energy paths have been characterized on the S0 and S1 potential energy surfaces. The fourfold way diabatization method has been applied to transform five adiabatic excited electronic states to a diabatic representation. The diabatic potential energy matrix of the first five excited singlet states has been constructed along several cuts of the potential energy hypersurfaces. The thermochemistry of the photodissociation reactions and a comparison with experimental translational energy distributions strongly suggest that nonadiabatic effects dominate the C–Br scission, but that the reaction proceeds along the energetically allowed diabatic pathway to excited-state products instead of being nonadiabatically suppressed. This conclusion is also supported by the low values of the diabatic couplings on the C–Br scission reaction path. The methodology established in the present study will be used for the construction of global potential energy surfaces suitable for multidimensional dynamics simulations to test these preliminary interpretations.
Quantum control mechanism analysis through field based Hamiltonian encoding
Authors: Mitra Abhra , Rabitz Herschel
Published: November 2006

Optimal control of quantum dynamics in the laboratory is proving to be increasingly successful. The control fields can be complex, and the mechanisms by which they operate have often remained obscure. Hamiltonian encoding (HE) has been proposed as a method for understanding mechanisms in quantum dynamics. In this context mechanism is defined in terms of the dominant quantum pathways leading to the final state of the controlled system. HE operates by encoding a special modulation into the Hamiltonian and decoding its signature in the dynamics to determine the dominant pathway amplitudes. Earlier work encoded the modulation directly into the Hamiltonian operators. This present work introduces the alternative scheme of field based HE, where the modulation is encoded into the control field and not directly into the Hamiltonian operators. This distinct form of modulation yields a new perspective on mechanism and is computationally faster than the earlier approach. Field based encoding is also an important step towards a laboratory based algorithm for HE as it is the only form of encoding that may be experimentally executed. HE is also extended to cover systems with noise and uncertainty and finally, a hierarchical algorithm is introduced to reveal mechanism in a stepwise fashion of ever increasing detail as desired. This new hierarchical algorithm is an improvement over earlier approaches to HE where the entire mechanism was determined in one stroke. The improvement comes from the use of less complex modulation schemes, which leads to fewer evaluations of Schrödinger’s equation. A number of simulations are presented on simple systems to illustrate the new field based encoding technique for mechanism assessment.
Enzymatic catalysis and transfers in solution. I. Theory and computations, a unified view
Authors: Marcus R. A.
Published: November 2006

The transfer of hydride, proton, or H atom between substrate and cofactor in enzymes has been extensively studied for many systems, both experimentally and computationally. A simple equation for the reaction rate, an analog of an equation obtained earlier for electron transfer rates, is obtained, but now containing an approximate analytic expression for the bond rupture-bond forming feature of these H transfers. A “symmetrization,” of the potential energy surfaces is again introduced [R. A. Marcus, J. Chem. Phys. 43, 679 (1965); J. Phys. Chem. 72, 891 (1968)], together with Gaussian fluctuations of the remaining coordinates of the enzyme and solution needed for reaching the transition state. Combining the two expressions for the changes in the difference of the two bond lengths of the substrate-cofactor subsystem and in the fluctuation coordinates of the protein leading to the transition state, an expression is obtained for the free energy barrier. To this end a two-dimensional reaction space (m,n) is used that contains the relative coordinates of the H in the reactants, the heavy atoms to which it is bonded, and the protein/solution reorganization coordinate, all leading to the transition state. The resulting expression may serve to characterize in terms of specific parameters (two “reorganization” terms, thermodynamics, and work terms), experimental and computational data for different enzymes, and different cofactor-substrate systems. A related characterization was used for electron transfers. To isolate these factors from nuclear tunneling, when the H-tunneling effect is large, use of deuterium and tritium transfers is of course helpful, although tunneling has frequently and understandably dominated the discussions. A functional form is suggested for the dependence of the deuterium kinetic isotope effect (KIE) on ΔG° and a different form for the C13 KIE. Pressure effects on deuterium and C13 KIEs are also discussed. Although formulated for a one-step transfer of a light particle in an enzyme, the results would also apply to single-step transfers of other atoms and groups in enzymes and in solution.
Size-dependent photoluminescence of hexagonal nanopillars with single InGaAs∕GaAs quantum wells fabricated by selective-area metal organic vapor phase epitaxy
Authors: Yang L. , Motohisa J. , Takeda J. , Tomioka K. , Fukui T.
Published: November 2006

The authors report the fabrication of the nanopillars with single InGaAs∕GaAs quantum well by selective-area metal organic vapor phase epitaxy. The standard diameter deviation of the nanopillars is about 8% and the standard deviation in their height about 5%. Their photoluminescence peak positions shift to the longer wavelength with an increase in the diameter of the nanopillars, which is not due to the quantum confinement effect in the radial or axial direction but due to the stoichiometry difference of the indium content in the nanopillars with different diameters.
Charging-delay induced dust acoustic collisionless shock wave: Roles of negative ions
Authors: Ghosh Samiran , Bharuthram R. , Khan Manoranjan , Gupta M. R.
Published: November 2006

The effects of charging-delay and negative ions on nonlinear dust acoustic waves are investigated. It has been found that the charging-delay induced anomalous dissipation causes generation of dust acoustic collisionless shock waves in an electronegative dusty plasma. The small but finite amplitude wave is governed by a Korteweg-de Vries Burger equation in which the Burger term arises due to the charging-delay. Numerical investigations reveal that the charging-delay induced dissipation and shock strength decreases (increases) with the increase of negative ion concentration (temperature).
Metal electrode effects on spin-orbital coupling and magnetoresistance in organic semiconductor devices
Authors: Wu Yue , Hu Bin
Published: November 2006

This letter reports the modifications of spin-orbital coupling and magnetoresistance of conjugated polymer upon deposition of metal electrode based on organic light-emitting diodes of poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene]. We find that the reverse bias yields a largely increased magnetoresistance when the electron-hole capture zone is away from the metal electrode as compared to the forward bias with the electron-hole capture zone close to the metal electrode. The electroluminescence suggests that the deposited metal atoms enhance the spin-orbital coupling at the polymer/metal interface and consequently lead to electron-hole capture zone dependent magnetic field effects in organic semiconductor devices.
Stoichiometric polyelectrolyte complexes of ionic block copolymers and oppositely charged polyions
Authors: Kramarenko E. Yu. , Khokhlov A. R. , Reineker P.
Published: November 2006

Micellization in dilute solutions of diblock copolymers with a polyelectrolyte and a hydrophilic nonionic blocks and oppositely charged polyions is studied using mean-field theory. In aqueous solutions the micelle core consists of the polyelectrolyte complex (PEC) while the corona is formed by hydrophilic blocks of the block copolymers. Describing PEC as a globule in the framework of the Lifshitz [Zh. Eksp. Teor. Fiz. 55, 2408 (1968)] globule theory we calculate the surface tension of the micellar core/solvent interface as a function of the polyion degree of ionization, solvent quality, and concentration of low-molecular-mass salt. The equilibrium aggregation number of starlike micelles formed by block copolymers and homopolymers of opposite charge at stoichiometric mixture compositions is found as a function of the system parameters. It is shown that micelles disintegrate upon addition of salt.
Low leakage current—stacked MgO∕Bi1.5Zn1.0Nb1.5O7 gate insulator— for low voltage ZnO thin film transistors
Authors: Lim Mi-Hwa , Kang KyongTae , Kim Ho-Gi , Kim Il-Doo , Choi YongWoo , Tuller Harry L.
Published: November 2006

The authors report on the role of MgO capping layers in notably reducing leakage currents and improving mobility in ZnO thin film transistors (TFTs) utilizing compatible high-k Bi1.5Zn1.0Nb1.5O7 (BZN) gate insulators. All room temperature processed ZnO based TFTs with stacked MgO/BZN gate insulator exhibited a much enhanced field effect mobility of 5.4cm2∕Vs with excellent saturation characteristics as compared to that (μFE=1.13cm2∕Vs) of ZnO based TFTs with BZN gate insulator. This work demonstrates the suitability of MgO/BZN stacked gate insulators in the fabrication of low voltage ZnO based TFTs on plastic substrates.
Mechanism for Ohmic contact formation on Si3N4 passivated AlGaN∕GaN high-electron-mobility transistors
Authors: Van Daele B. , Van Tendeloo G. , Derluyn J. , Shrivastava P. , Lorenz A. , Leys M. R. , Germain M.
Published: November 2006

Recent experiments have shown that in situ passivation by Si3N4 of AlGaN∕GaN high-electron-mobility transistors results in improved electrical characteristics. Transmission electron microscopy techniques have been applied to study the metal contact formation on top of passivated AlGaN∕GaN structures. Contrary to unpassivated AlGaN∕GaN, the AlGaN top layer is not consumed by a typical Au∕Mo∕Al∕Ti metal stack. Instead, a thin AlN interface layer is formed, being the key factor in the Ohmic contact formation. The formation of this AlN is believed to be due to extraction of N atoms out of the AlGaN. The resulting N vacancies, electrical donors, create a conducting channel through the AlGaN.
A finite-volume variational multiscale method coupled with a discrete interpolation filter for large-eddy simulation of isotropic turbulence and fully developed channel flow
Authors: Sagaut P. , Ciardi M.
Published: November 2006

The variational multiscale (VMS) approach proposed by Hughes et al. is applied to the Smagorinsky model and developed within the context of a physical-space unstructured finite-volume solver. A specific explicit filtering procedure is also developed, based on the idea of the discrete interpolation filters, originally proposed by Marsden et al. Tests on decaying isotropic turbulence at infinite Reynolds number and fully developed channel flow at friction Reynolds number Reτ=395 are performed, using the dynamic Smagorinsky model for comparison. For the VMS version of the Smagorinsky model, the conservative choice of not adapting the model’s constant is made, giving good indications on the required adjustment directions in both isotropic flows and nonisotropic flows. Promising results are obtained in general by the VMS approach with the two test cases. An overdissipative behavior is observed in the isotropic turbulence test case, which does not have a strong spectral connotation and could probably be cured adjusting the model’s constant. A very good prediction of the levels of unsteadiness is produced by VMS in the channel flow test case, showing the potential of this approach for nonisotropic flows. In both of the test cases the VMS approach gives performances of the same order of accuracy of the dynamic Smagorinsky model used for comparison, being at the same time less computationally expensive.
Density functional theory reveals an increase in the amino H1 chemical shift in guanine due to hydrogen bonding with water
Authors: van Mourik Tanja
Published: November 2006

Electronic structure calculations underestimate the chemical shift of the non H-bonded amino proton H221 in isolated G-quartet structures. The current work shows that this underestimation is due to the absence of a water environment in the calculations: coordination of at least two water molecules is required to obtain good agreement with experiment. The results indicate how improved agreement between calculated and experimental (solution-phase) NMR data can be obtained.
The Structures of Higher Rare Earth Oxides: Role of the Coordination Defect
Authors: Hoskins BF , Martin RL
Published: November 2006

A milestone in our understanding of the chemistry of the defect solid state has been achieved through new insights provided by recently published neutron diffraction studies of five rare earth oxides with compositions in the range M2O3-MO2. For more than four decades the exact way by which gross concentrations (i.e., up to 25%) of vacant sites can be accommodated in the fluorite MO2 lattice has remained largely unresolved. There is now compelling evidence that the vacancies do not exist in isolation but as octahedral 'coordination defects' of composition {MIII/2MIV/1.5□O6}. It is now clear that the intricate planar patterns formed by anion vacancies in the fluorite lattice arise from the unique and structure-determining topology of these coordination defects. The decisive role played by the coordination defect in generating extended defects in these fluorite-related oxides is highlighted in this paper.
Decaphenylferrocene
Authors: Field LD , Hambley TW , Humphrey PA , Lindall CM , Gainsford GJ , Masters AF , Stpierre TG , Webb J
Published: November 2006

Decaphenylferrocene was obtained as an extremely insoluble, maroon microcrystalline solid by heating [(η5-C5Ph5)((η6-C6H5)C5Ph4)Fe], and was characterized by 57Fe Mossbauer spectroscopy, X-ray photoelectron spectroscopy, mass, electronic and vibrational spectroscopy, solid-state 13C n.m.r. spectroscopy and high-resolution X-ray powder diffraction, which showed it to be isostructural with decaphenylnickelocene.
Cylindricines H-K, Novel Alkaloids From the Ascidian Clavelina cylindrica
Authors: Li CP , Blackman AJ
Published: November 2006

Three novel reduced pyrrolo [2,1-j] quinolines (cylindricines H, I and K) and one novel pyrido [2,1-j] quinoline ( cylindricine J) have been isolated from two further Tasmanian collections of the ascidian Clavelina cylindrica. These alkaloids are all related in structure to cylindricines A-G which have been obtained previously from the same ascidian. Cylindricines H-J are the first acetoxycylindricines obtained. Furthermore cylindricines I and J are isothiocyanates, the first such compounds identified from an ascidian, while cylindricine H is a thiocyanate which, together with cylindricines F and G, are the only ascidian thiocyanates known. Cylindricine K is an α,β -unsaturated ketone with the carbonyl group in the 8-position rather than the more usual 4-position as found in cylindricines A-G. Identification of the new alkaloids was by 1H n.m.r., 13C n.m.r., XHCORR, COSY and Fourier-transform i.r . Spectroscopy as well as high resolution e.i. mass spectrometry. Molecular modelling was used to assign relative stereochemistry. The geographical variation of the cylindricines is also reviewed.
Aluminum(III)-Isocitrate Solution Chemistry. A Potentiometric Study
Authors: Powell KJ , Town RM
Published: November 2006

The equilibrium reactions of isocitrate with protons and Al3+ have been
studied by potentiometric titration in aqueous 0.10 M KCl at 25°C. The protonation constants, corrected for K+-isocitrate complexing , were logβ0,1,1 = 5.838, logβ0,2,1 = 10.126 and logβ0,3,1 = 13.219. The stabilities and stoichiometries of the complexes, AlpHqLr, were defined by the constants logβ1,1,1 = 9.55(05), logβ1,0,1 = 6.90(02), logβ1,-1,1 = 3.06(04) and logβ2,-3,2 = 4.08(04) or logβ3,-4,3 = 10.36(06). Compared with the Al3+-citrate system, complexes are of lower thermodynamic stability, but equilibrate more rapidly.
Suppression of the Wolff Rearrangement of an Unstrained α-Carbonyl Carbene by CO and O2 in Low-Temperature Matrices
Authors: Mccluskey A , Dunkin IR
Published: November 2006

Photolysis of matrix-isolated dimethyl diazomalonate (1) in low-temperature argon matrices resulted in a rapid photoinduced Wolff rearrangement to methoxy(methoxycarbonyl)ketene (3). When the photolysis was carried out in pure CO matrices or argon matrices containing carbon monoxide or dioxygen, the reaction pathway was diverted by trapping of the intermediate carbene (2). With dioxygen, a carbonyl oxide intermediate was detected by u.v.-visible spectroscopy. The relative reactivity of carbene (2) with CO and O2 suggests that it was generated and trapped in a singlet state.
Molecular Cocrystals of Carboxylic Acids. XX. The Crystal Structures of 3,5-Dinitrosalicylic Acid and Its Adducts With the Isomeric Monoaminobenzoic Acids
Authors: Smith G , Lynch DE , Byriel KA , Kennard CHL
Published: November 2006

The crystal structure of 3,5-dinitrosalicylic acid monohydrate (1) and its adducts with 2- aminobenzoic acid (2-aba) [( dnsa )(2-aba)] (2), 3-aminobenzoic acid (3-aba) [( dnsa )(3-aba)] (3), and 4-aminobenzoic acid (4-aba) [( dnsa )(4-aba)2] (4), have been determined and the hydrogen bonding associations in each analysed . The acid (1), which is essentially planar, forms strong hydrogen-bonding network associations involving the carboxylic, nitro and phenolic oxygens as well as the lattice water. In all adducts, protonation of the amino group of the second acid occurs, with subsequent hydrogen bonding via all three alkyl ammonium hydrogens to the carboxylic, nitro and phenolic oxygens of dnsa. With the 1:2 adduct (4), only one of the two 4-aba molecules is protonated, these forming a secondary hydrogen-bonded cyclic dimer. A strong intramolecular hydrogen bond between the phenolic proton and the carboxylate group is found in all adducts.
The Synthesis and N.M.R. Investigation of a Methyloxime Derivative of N-Acetylneuraminic Acid
Authors: Groves DR , Wilson JC , Vonitzstein M
Published: November 2006

The synthesis of a novel 4-modified N-acetylneuraminic acid analogue and its structural characterization by n.m.r. spectroscopy are reported.
Structural Studies of Alkaline Earth Metal Picrates
Authors: Harrowfield JM , Skelton BW , White AH
Published: November 2006

Room-temperature, single-crystal X-ray structure determinations are recorded for alkaline earth metal
picrates , M( pic )2.nH2O(M = Mg, Sr , Ba ; Hpic = 2,4,6-trinitrophenol, HOC6H2(NO2)3),
all crystallized from aqueous solution. Magnesium picrate ,shown to be the nonahydrate,
Mg( pic )2.9H2O, forms monoclinic crystals, space group P21/c, a 15.023(3), b
6.718(4), c 26.516(2) Ǻ, β 109.55(1)°, Z = 4 f.u .,conventional R on |F| was 0.049
for No = 4062 'observed' (I > 3σ(I)) reflections. The structure, unusually among the main group metal picrates
studied so far, has no coordinative interaction between the metal and the picrate anion; the complex may be formulated as [Mg(OH2)6]
( pic )2.3H2O, with the metal present as the hexaaqua species (Mg-O
2.043(2)-2.077(2)Ǻ). The picrate ions are stacked end to end, presumably as a result of charge-transfer interactions,
parallel to b, with side-by-side stacks forming a sheet along ab, and successive sheets are interleaved by layers of cations and water molecules. The strontium salt is a pentahydrate , monoclinic, C2/c, a 24.515(6), b 10.142(6), c
17.932(4) Ǻ, β 98.76(2)°, Z = 8 f.u .; R was 0.046 for No 2731.
The complex is a linear polymer, [(H2O)3Sr(O,O′- pic )2(μ-OH2)](∞|∞).H2O,
with eight-coordinate (SrO8) strontium. The barium salt is a hexahydrate , also a linear polymer [(H2O)5Ba(O,O′-pic )( O,O′,μ-O″-pic )]∞|∞).H2O,
the ten-coordinate (BaO10) barium environment comprising the five
water molecules, a pair of picrates, bidentate /chelating via the phenolic
oxygen and a 2-nitro group oxygen, with one of the picrates
from an adjacent metal atom offering an additional 4-nitro group oxygen, this
bridging successive barium atoms. The complex is triclinic, Pī ,
a 15.120(5), b 11.633(3), c 6.766(3) Ǻ, α 87.24(3), β 79.16(3),
γ 84.88(2)°, Z = 2 f.u .; R was 0.027 for No
3904. Repeated attempts to obtain crystals of beryllium picrate suitable for an X-ray structure determination were unsuccessful.
The Optical Rotation of Some C15-Oxygenated Labda-8(17),13-dienes
Authors: Carman RM , Duffield AR
Published: November 2006

A range of C15-oxygenated labda-8(17),13-dienes has been synthesized optically pure to provide reference data for comparisons with naturally occurring compounds.
Synthesis and X-Ray Crystal Structure of 8,9-Dimethoxy-4-methyl-3-phenyl-2,3,5,6-tetrahydropyrrolo[2,1-α]isoquinolinium Iodide
Authors: Bailey TS , Bremner JB , Pelosi L , Skelton BW , White AH
Published: November 2006

N-Methylation of 6,7-dimethoxy-1-(2�-phenylcyclopropyl)-3,4-dihydroisoquinoline (3b) with iodomethane in refluxing acetone gave the modified Cloke rearrangement product, 8,9-dimethoxy-4-methyl-3-phenyl-2,3,5,6-tetrahyropyrrolo[2,1-a] isoquinolinium iodide (5b), a new derivative of the pyrrolo [2,1-a] isoquinoline skeleton, together with the methiodide salt (4b) of (3b). The structure of (5b) was confirmed by X-ray crystallographic analysis.
The Stereochemistry of the Tetrabromides From Linoleic Acid
Authors: Garman RM , Duffield AR , Edwards RA , Robinson WT
Published: November 2006

The stereochemistry of the crystalline 9,10,12,13-tetrabromostearic acid obtained by bromination of linoleic acid has been established by X-ray crystallograpic analysis. The structures of the corresponding oily tetrabromide , and of the two derived 1,8,9,11,12-pentabromoheptadecanes, follow.
Developments in Microwave-Assisted Organic Chemistry
Authors: Strauss CR , Trainor RW
Published: November 2006

Microwave-assisted organic chemistry is reviewed in the context of the methods employed. A range of technical difficulties indicated that specifically designed reactors were required. Hence, the CSIRO continuous microwave reactor (CMR) and microwave batch reactor (MBR) were developed for organic synthesis. On the laboratory scale, they operated at temperatures (pressures) up to 200°C (1400 kPa) and 260°C (10 MPa), respectively. Advantages and applications of the units are discussed, along with safety issues. Features include the capability for rapid, controlled heating and cooling of reaction mixtures, and elimination of wall effects. Concurrent heating and cooling, and differential heating were unique methodologies introduced to organic synthesis through the MBR. Applications of the microwave reactors for optimizing high-temperature preparations, e.g, the Willgerodt reaction and the Fischer indole synthesis, were demonstrated. Water was a useful pseudo-organic solvent, applicable to environmentally benign synthetic chemistry.
Synthesis of Helical Molecules Based on 5,6,6a,7,8,12b-Hexahydrobenzo[c]phenanthrene-5,8-dione
Authors: Cheung J , Field LD , Regaglia F , Sternhell S
Published: November 2006

Synthetic routes based on Newman's1-7 synthesis of a number of polycyclic aromatic hydrocarbons were modified and developed to give a convenient preparation (Scheme 1) of 11 helical molecules formally based on hexalindione (1). In contrast to Newman's work determined the stereochemistry at C6a-C12b in (1a-k) and in some cases, were able to control it. We also investigated the competitive formation of six- and seven- membered rings in the reaction yielding the hexacyclic derivatives (1d, e). In addition, we report an unusual fragmentation (Scheme 2) leading to the unexpected by-product 4-methoxyacetophenone (16) in the synthesis of (1h).
2″-O-Methylgyrophoric Acid, a New Lichen Tridepside
Authors: Elix JA , Elix JA , Barbero M , Barbero M , Giralt M , Giralt M , Lumbsch HT , Lumbsch HT , Mccaffery LF , Mccaffery LF
Published: November 2006

A new metabolite has been detected in the lichens Diploschistes gyrophoricus and Rinodina alba, and its chromatographic behaviour shown to be identical with that of 2″-O-methylgyrophoric acid (6), the total synthesis of which is described.
Solid-State 31P Nuclear Magnetic Resonance Spectroscopic Study of Phosphorylated Peptide-Resins and Phosphorylated Wool Keratin
Authors: Perich JW , Johns RB , Thompson AR , Botto RB
Published: November 2006

Solid-state 31P n.m.r. spectroscopy was found to be a useful method for the analysis of phosphorylated peptide-polystyrene resins and permitted the monitoring of chemical modifications of the phosphate moiety whilst the phosphorylated peptide was bound to the polystyrene support. Solid-state 31P n.m.r. spectroscopy was also applied to the analysis of phosphorylated wool keratin samples and showed that (A) different phosphate functionalities could be identified from the use of particular phosphorylation treatments, and (B) the majority of the phosphorylative modifications was located on the surface of wool keratin. This technique was found to be useful for monitoring the effectiveness of secondary chemical modification treatments on phosphorus trichloride-treated wool fabric samples.
Photochemical Nitration by Tetranitromethane. XXIX. Adduct Formation in the Photochemical Reaction of Tetranitromethane and 1,5-Dimethylnaphthalene; Allylic Rearrangements of Adducts
Authors: Butts CP , Eberson L , Hartshorn MP , Robinson WT
Published: November 2006

Photolysis of the 1,5-dimethylnaphthalene/tetranitromethane charge-transfer complex yields the triad of 1,5-dimethylnaphthalene radical cation, nitrogen dioxide and trinitromethanide ion. Recombination of this triad gives predominantly the epimeric 4,8-dimethyl-1-nitro-4-trinitromethyl-1,4-dihydronaphthalenes (18) and (27), the epimeric 1,5-dimethyl-1-nitro-4-trinitromethyl-1,4-dihydronaphthalenes (20) and (21), 4,8-dimethyl-r-1-nitro-t-2-trinitromethyl-1,2-dihydronaphthalene (19), 4,8-dimethyl-t-2-trinitromethyl-1,2-dihydronaph-thalen-r-1-ol (23), nitro cycloadduct (22), hydroxy cycloadduct (24), nitronic ester (25) and 4,8-dimethyl-1-nitronaphthalene (26). Adduct (19) is formed substantially by allylic rearrangement of 4,8-dimethyl-1-nitro-4-trinitromethyl-1,4-dihydronaphthalene (18), and adduct (23) and indirectly nitronic ester (25) by allylic rearrangement of a postulated intermediate 4,8-dimethyl-t-4-trinitromethyl-1,4-dihydronaphthalen-r-1-ol (32). Adducts (18), (19), (23), (25) and (27) are formed by attack of trinitromethanide ion at C 1 of the 1,5-dimethylnaphthalene radical cation, while adducts (20)-(22) and (24) are formed by the corresponding attack at C4, the reaction pathways being determined by the relative energies of the intermediate delocalized carbon radicals. Adduct formation is substantially suppressed for a photolysis when trifluoroacetic acid (0.7 M) is added to the dichloromethane solvent at 20°, 1,5-dimethyl-4-nitronaphthalene (26) being formed close to quantitatively. In contrast, photolysis of the 1,5-dimethylnaphthalene/tetranitromethane charge-transfer complex in 1,1,1,3,3,3-hexafluoropropan-2-ol gave substantial amounts of adduct (19), together with 1,5-dimethyl-4-nitronaphthalene (26) as the major product. Allylic rearrangements of 1-methoxy-4-nitro-1-trinitromethyl-1,4-dihydronaphthalene (34) and the epimeric 1,4,5,8-tetramethyl-1-nitro-4-trinitromethyl-1,4-dihydronaphthalenes (38) are seen as the mode of formation of 4-methoxy-r-1-nitro-t-2-trinitromethyl-1,2-dihydronaphthalene (33) and the epimeric 1,4,5,8-tetramethyl-1-nitro-2-trinitromethyl-1,2-dihydronaphthalenes (36), respectively. X-Ray crystal structure determinations are reported for adducts (19), (20), (22), (24) and (28), the last compound being formed only on chromatography of reaction mixtures.
Mechanisms of Nucleophilic Attack at Carbon-Nitrogen Double Bonds. The Reaction of Benzohydrazonoyl Compounds With Methoxide Ion
Authors: Rowe JE , Papanelopoulos DA
Published: November 2006

Rate data for the reaction of a number of benzohydrazonoyl compounds with methoxide ion are reported. The stereochemistry of the products was determined by h.p.l.c. The mechanism of the reactions and the stereochemistry of the products resulting from an addition-elimination mechanism are discussed.
The Extracellular Linker of pro-Neuregulin-α2c Is Required for Efficient Sorting and Juxtacrine Function
Authors: Montero Juan C. , Rodríguez-Barrueco Ruth , Yuste Laura , Juanes Pedro P. , Borges Joana , Esparís-Ogando Azucena , Pandiella Atanasio
Published: November 2006

The neuregulins (NRGs) play important roles in animal physiology, and their disregulation has been linked to diseases such as cancer or schizophrenia. The NRGs may be produced as transmembrane proteins (proNRGs), even though they lack an N-terminal signal sequence. This raises the question of how NRGs are sorted to the plasma membrane. It is also unclear whether in their transmembrane state, the NRGs are biologically active. During studies aimed at solving these questions, we found that deletion of the extracellular juxtamembrane region termed the linker, decreased cell surface exposure of the mutant proNRGΔLinker, and caused its entrapment at the cis-Golgi. We also found that cell surface–exposed transmembrane NRG forms retain biological activity. Thus, a mutant whose cleavage is impaired but is correctly sorted to the plasma membrane activated ErbB receptors in trans and also stimulated proliferation. Because the linker is implicated in surface sorting and the regulation of the cleavage of transmembrane NRGs, our data indicate that this region exerts multiple important roles in the physiology of NRGs.