bluuebunny/crossref_metadata_2025 huggingface dataset:
Adsorption behavior of surfactant‐polyacrylamide mixtures with kaolin
Authors: Sastry N. V. , Dave P. N.
Published: November 2006

The adsorption behavior of three surfactants—hexadecylpyridinium bromide (HPyBr), sodium dodecylbenzene sulfonate (SDBS), and Triton X‐100 (TX‐100)—on kaolin from aqueous solution is monitored as a function of pH. The nature and shape of the adsorption isotherms are typical and highly dependent on the surfactant structure. All three surfactants adsorb on kaolin beyond the limits of monolayer coverage. Isotherms for HPyBr fit the Langmuir equation well. SDBS isotherms are typical of a two‐stage process, and TX‐100 adsorption isotherms are S‐shaped. The pH‐sensitive adsorption of each surfactant and the models used to represent the isotherms are considered together in explaining the mechanism of adsorption in each case. The complex mixture adsorption behavior from polyacrylamide‐surfactant mixtures is also determined in acidic and basic pH media. Three polyacrylamides, catam1, anam1 and nonam1, are chosen to represent cationic, anionic, and nonionic polymers, respectively. Both competitive and synergistic effects are noted in the mixture adsorption depending upon the polymer‐surfactant pair and the mode of introduction of a second component in the presence of another. The results are explained by considering various factors such as changes in the nature of solvent power of the media, interaction between the polymer and surfactant in the bulk solution as well as at the kaolin surface, blocking of surface sites by a preadsorbed component, and the change in the conformation state of polymer chains
Metabolism of very long chain polyunsaturated fatty acids in isolated rat germ cells
Authors: Retterstøl Kjetil , Tran Thien N. , Haugen Trine B. , Christophersen Bjørn O.
Published: November 2006

Which cell type is responsible for the high levels of very long chain polyunsaturated fatty acids in testis and whether this fatty acid pattern is a result of a local synthesis are not presently known. In this study, fatty acid conversion from 20∶4n−6 to 22∶5n−6 and from 20∶5n−3 to 22∶6n−3 was investigated in isolated rat germ cells incubated with [1‐14C]‐labeled fatty acids. The germ cells elongated the fatty acids from 20‐ to 22‐carbon atoms and from 22‐ to 24‐carbon atoms but had a low Δ6 desaturation activity. Thus, little [14C]22∶5n−6 and [14C]22∶6n−3 were synthesized. When Sertoli cells were incubated with [1‐14C]20∶5n−3 for 24 h, an active fatty acid elongation and desaturation were observed. In vivo germ cells normally have a higher content of 22∶5n−6 or 22∶6n−3 than Sertoli cells. An eventual transport of essential fatty acids from Sertoli cells to germ cells was thus studied. Different co‐culture systems were used in which germ cells were on one side of a filter and Sertoli cells on the opposite side. When isolated pachytene spermatocytes or round spermatids were added to the opposite side of a semipermeable filter, approximately 1 nmol [14C]‐22∶6n−3 crossed the filter. Little of this was esterified in the germ cells. Similarly, in using [1‐14C]20∶4n−6 in identical experiments, very little [14C]22∶5n−6 was esterified in germ cells on the opposite side of the filter. Although the very active synthesis of 22∶5n−6 and 22∶6n−3 observed in Sertoli cells suggests a transport of these compounds to germ cells, this was not experimentally determined.
Composition of the silk lipids of the spider Nephila clavipes
Authors: Schulz Stefan
Published: November 2006

A detailed analysis of the lipids of spider silk is given for the first time. Extracts of the silk from the golden orb weaver, Nephila clavipes, were studied by gas chromatography, mass spectrometry, and chemical derivatizations. The major group of the lipids consisted of methyl‐branched 1‐methoxyalkanes (methyl ethers) with up to four methyl groups in the chain (chain length between C28 and C34), which are unique to spiders. The position of the methyl branches was determined by conversion into cyanides, which allowed easy location of methyl branches. The second‐largest group included alkanes with a wide structural variety; 2‐methyl‐branched, even‐numbered hydrocarbons predominated. A general numerical method for the estimation of retention indices of alkanes and their derivatives is presented. Further components of the web included alkanols and alkanediols, fatty acids, and glyceryl ethers. Some comments on the biosynthesis of these compounds are also given.
Intestinal apolipoprotein B secretion is inhibited by the flavonoid quercetin: Potential role of microsomal triglyceride transfer protein and diacylglycerol acyltransferase
Authors: Casaschi Adele , Wang Qi , Dang Ka'ohimanu , Richards Alison , Theriault Andre
Published: November 2006

Recent studies have yielded evidence that plant flavonoids reduce hepatic lipid and apolipoprotein B (apoB) secretion. However, the possible role of flavonoids in regulating lipid and apoB secretion by the intestine has not been studied. The purpose of our study was to examine the effects of quercetin, a common dietary flavonoid, on TAG and apoB secretion in a human intestinal cell‐line, CaCo‐2. Differentiated postconfluent CaCo‐2 cells grown on filters and pretreated with quercetin for 8 h were shown by ELISA to inhibit basolateral apoB secretion in a dose‐dependent manner. At 15 μM, the secretion of both apoB‐100 and apoB‐48 were inhibited similarly. This effect was shown to be specific, as quercetin did not affect the incorporation of [35S]methionine/cysteine into secreted TCA‐precipitable proteins. To determine the mechanism underlying this inhibitory effect, we examined two regulatory points: IAG availability and lipid transfer to the lipoprotein particle. Quercetin inhibited TAG synthesis under both basal and lipid‐rich conditions, indicating that lipid availability is a determining factor in the regulation of apoB secretion by quercetin. The reduction was due at least in part to a decrease in diacylglycerol acyltransferase activity. We next examined lipid transfer or lipidation of the lipoprotein particle by analyzing microsomal IAG transfer protein (MTP) activity. Quercetin decreased MTP activity moderately. In summary, the data demonstrated that pharmacological concentrations of quercetin are a potent inhibitor of intestinal apoB secretion and that reduced lipid availability and lipidation in the lipoprotein assembly step are the mechanism for the suppression of apoB‐containing lipoprotein secretion by quercetin in CaCo‐2 cells.
Comparative effects of palm vitamin E and α‐tocopherol on healing and wound tissue antioxidant enzyme levels in diabetic rats
Authors: Musalmah M. , Nizrana M. Y. , Fairuz A. H. , NoorAini A. H. , Azian A. L. , Gapor M. T. , Wan Ngah W. Z.
Published: November 2006

The effect of supplementing 200 mg/kg body weight palm vitamin E (PVE) and 200 mg/kg body weight α‐tocopherol (α‐loc) on the healing of wounds in streptozotocin‐induced diabetic rats was evaluated. The antioxidant potencies of these two preparations of vitamin E were also evaluated by determining the antioxidant enzyme activities, namely, glutathione peroxidase (GPx) and superoxide dismutase (SOD), and malondialdehyde (MDA) levels in the healing of dermal wounds. Healing was evaluated by measuring wound contractions and protein contents in the healing wounds. Cellular redistribution and collagen deposition were assessed morphologically using cross‐sections of paraffin‐embedded day‐10 wounds stained according to the Van Gieson method. GPx and SOD activities as well as MDA levels were determined in homogenates of day‐10 dermal wounds. Results showed that PVE had a greater potency to enhance wound repair and induce the increase in free radical‐scavenging enzyme activities than α‐Toc. Both PVE and α‐Toc, however, were potent antioxidants and significantly reduced the lipid peroxidation levels in the wounds as measured by the reduction in MDA levels.
9‐trans,11‐trans‐CLA: Antiproliferative and proapoptotic effects on bovine endothelial cells
Authors: Lai Kuan‐Lin , Torres‐Duarte Armida P. , Vanderhoek Jack Y.
Published: November 2006

Endothelial cell function can be influenced by nutrition, especially dietary FA and antioxidants. One class of dietary FA that is found in meat and dairy products derived from ruminant animals is conjugated linoleic acids (CLA). We have examined the effects of several CLA isomers on endothelial cell proliferation. 9t,11t‐CLA was the only isomer that inhibited bovine arotic endothelial cell (BAEC) [3H]methylthymidine incorporation (I50=35 μM), and this antiproliferative effect was time‐dependent. A small decrease (20%) in cell number was observed only at the highest concentration (60 μM) tested. The 9c,11t‐, 9c,11c‐, 10t 12c‐, and 11c,13t‐CLA isomers did not exhibit any antiproliferative effects over a 5–60 μM concentration range. α‐Tocopherol and BHT decreased BAEC proliferation, but pretreatment of cells with either of these antioxidants substantially attenuated the antiproliferative effect of 9t,11t‐CLA. No difference in lipid peroxidation, as measured by the thiobarbituric acid assay for malondialdehyde, was observed on treatment of endothelial cells with either 9t,11t‐ or 9c,11t‐CLA. However, a 43% increase in caspase‐3 activity was observed after incubating BAEC with 9t,11t‐CLA, suggesting that the antiproliferative effect of this isomer is partially due to an apoptotic pathway. In contrast to the above results with normal endothelial cells, these five CLA isomers all inhibited proliferation of the human leukemic cell line THP‐1, with the 9t,11t isomer again being the most (I50=60 μM) effective. These results confirm that different CLA isomers have different inhibitory potencies on the proliferation of normal and leukemic cells.
Parathyroid hormone stimulates phosphatidylethanolamine hydrolysis by phospholipase D in osteoblastic cells
Authors: Singh Amareshwar T. K. , Frohman Michael A. , Stern Paula H.
Published: November 2006

Parathyroid hormone (PTH) and phorbol‐12,13‐dibutyrate (PDBu) stimulate phospholipase D (PLD) activity and PC hydrolysis in UMR‐106 osteoblastic cells {Singh, A.T., Kunnel, J.G., Strieleman, P.J., and Stern, P.H. (1999) Parathyroid Hormone (PTH)‐(1–34), [Nle8, 18, Tyr34]PTH‐(3–34) Amide, PTH‐(1–31) Amide, and PTH‐Related Peptide‐(1–34) Stimulate Phosphatidylcholine Hydrolysis in UMR‐106 Osteoblastic Cells: Comparison with Effects of Phorbol 12,13‐Dibutyrate, Endocrinology 140, 131–137}. The current studies were designed to determine whether ethanolamine‐containing phospholipids, and specifically PE, could also be substrates. In cells labeled with 14C‐ethanolamine, PTH and PDBu treatment decreased 14C‐PE. In cells co‐labeled with 3H‐choline and 14C‐ethanolamine, PTH and PDBu treatment increased both 3H‐choline and 14C‐ethanolamine release from the cells. Choline and ethanolamine phospholipid hydrolysis was increased within 5 min, and responses were sustained for at least 60 min. Maximal effects were obtained with 10 nM PTH and 50 nM PDBu. Dominant negative PLD1 and PLD2 constructs inhibited the effects of PTH on the phospholipid hydrolysis. The results suggest that both PC and PE are substrates for phospholipase D in UMR‐106 osteoblastic cells and could therefore be sources of phospholipid hydrolysis products for downstream signaling in osteoblasts.
Effect of exercise on FA profiles in n−3 FA‐supplemented and‐nonsupplemented premenopausal women
Authors: Conquer Julie A. , Roelfsema Heather , Zecevic Julie , Graham Terry E. , Holub Bruce J.
Published: November 2006

The purpose of this double‐blind study was to investigate the influence of exercise on the FA profile of the nonesterified FA (NEFA) and phospholipid fractions in plasma of sedentary women supplemented with n−3 FA vs. women supplemented with oil containing no n−3 FA. Twenty sedentary, premenopausal women were randomly assigned to receive 12 capsules daily of either fish oil (3.5 g FPA and 2.4 g DHA per day, each as the ethyl ester) or evening primrose oil capsules (no detectable EPA or DHA). Each subject consumed the capsules for one menstrual cycle. At the end of the supplementation period, the sedentary subjects underwent an acute exercise trial [55% maximal oxygen consumption (VO2 max), 45 min] on a cycle ergometer. Two subjects in the fish oil group were removed from all calculations owing to noncompliance for reasons not related to side effects. There were no changes in the phospholipid composition of either group of women after exercise. In both control and fish oil‐supplemented women, NEFA levels in general rose after exercise. There were no changes in the percentage of any given individual NEFA in either supplementation group. However, absolute levels of certain individual NEFA (16∶0, 18∶0, 18∶1, and 18∶3n−3) increased with exercise. Women supplemented with fish oil had increased levels of n−3 NEFA [EPA, DHA, and docosapentaenoic acid (DPA)] prior to exercise. Exercise did not, however, increase the absolute levels of n−3 NEFA in the blood.
Ozonation of PC in ethanol: Separation and identification of a novel ethoxyhydroperoxide
Authors: Tagiri‐Endo Misako , Ono Kaori , Nakagawa Kiyotaka , Yotsu‐Yamashita Mari , Miyazawa Teruo
Published: November 2006

The product of the ozonolysis of 1‐palmitoyl‐2‐oleoyl‐sn‐glycero‐3‐phosphocholine in ethanol‐containing solvent was analyzed by chemiluminescence detection‐HPLC with on‐line electrospray MS, and characterized on the basis of NMR spectroscopy and MS in high‐resolution fast atom bombardment mode. The reaction yielded a large amount of a novel ethoxyhydroperoxide compound [1‐palmitoyl‐2‐(9‐ethoxy‐9‐hydroperoxynonanoyl)‐sn‐glycero‐3‐phosphocholine]. In addition to a structural analysis, we speculate on the reaction pathway and discuss the possibility of ethoxyhydroperoxide as a potentially reactive ozonized lipid in food and biological materials.
Triacylglycerol hydroperoxides not detected in pig small intestinal epithelial cells after a diet rich in oxidized triacylglycerols
Authors: Suomela Jukka‐Pekka , Ahotupa Markku , Kallio Heikki
Published: November 2006

The presence of TAG hydroperoxides in the epithelial cells of the small intestines in growing pigs was studied after they had consumed a diet rich in either nonoxidized or oxidized sunflower seed oil (PV in oils, 1 and 190 mequiv O2/kg, respectively). To obtain molecular‐level information on the oxidized TAG structures, a new approach based on TLC and HPLC‐electrospray ionization‐MS was used in the analysis of the samples. TAG hydroperoxides were not detected in the small intestinal mucosa or adipose tissue of either group, whereas TAG hydroxides, ketones, and epoxides were detected in all samples. The results suggest that dietary TAG hydroperoxides do not lead to the appearance of these molecules in the tissues.
S‐methyl derivatives from thiol compounds by the pyrolytic reaction with trimethylsulfonium hydroxide
Authors: Vosmann Klaus , Klein Erika , Weber Nikolaus
Published: November 2006

Base‐catalyzed transesterification of acyl lipids with methanol in the presence of trimethylsulfonium hydroxide (TMSH) is an easy and convenient method for the preparation of fatty acid methyl esters for gas chromatography (GC) analyses. Free fatty acids are converted to fatty acid methyl esters by the pyrolytic reaction with TMSH as well. We have found that lipids and other compounds containing thiol groups are also converted easily to the corresponding methyl sulfides (methyl thioethers) by the pyrolytic reaction with TMSH occurring in the injector of the gas chromatograph. For example, alkane thiols such as dodecane thiol and octadecane thiol are converted to the corresponding alkyl methyl sulfides, whereas bis(methylthio) derivatives are formed from α,ω‐alkane dithiols, e.g., 1,8‐octanedithiol, and from 2,3‐dimercaptopropan‐1‐ol (dimercaprol). Furthermore, 3β‐mercaptocholest‐5‐ene (thiocholesterol) is converted to 3‐methylthiocholest‐5‐ene by the same reaction. The S‐methylation reactions which finally lead to the corresponding methylthio derivatives of lipids and other compounds with thiol groups may be of diagnostic value for the structural analysis of such compounds by GC and GC/mass spectrometry.
Lipid and fatty acid composition of brush border membrane of rat intestine during starvation
Authors: Waheed A. A. , Yasuzumi F. , Gupta P. D.
Published: November 2006

Alterations in the lipid and fatty acid composition of brush border membrane (BBM) of small intestine were studied in well‐fed, starved, and refed rats. The ratios of cholesterol/phospholipid (mol/mol), sphingomyelin/phosphatidylcholine (mol/mol), protein/lipid (w/w), and free fatty acids (w/w) decreased whereas the total phospholipid (w/w) ratio and the double‐bond index increased in BBM of the intestine of the starved rat compared to that of the well‐fed rat. Analyses of fatty acids showed higher percentage of stearic and arachidonic acids whereas oleic and linoleic acids decreased under starvation. The acyl chain of starved rat BBM was less ordered compared with that of well‐fed rat BBM. On refeeding, these changes were restored to well‐fed levels. The change in membrane state under starvation is associated with alterations in the lipid and fatty acid composition of BBM and may be responsible for functional changes that occur under nutritional stress.
Large investor trading impacts on volatility
Authors: Lions Pierre-Louis , Lasry Jean-Michel
Published: November 2006

We begin with this paper a series devoted to a tentative model for the influence of hedging on the dynamics of an asset. We study here the case of a “large” investor and solve two problems in the context of such a model namely the question of the fair value (or liquidative value) of a “large” position and the question of pricing or hedging an option. In order to do so, we use a utility maximization approach and some new results in stochastic control theory.
CHILDREN OF HOMOSEXUALS AND TRANSSEXUALS MORE APT TO BE HOMOSEXUAL: A REPLY TO CAMERON
Authors: MORRISON TODD G.
Published: November 2006

Paul Cameron, author of ‘Children of Homosexuals and Transsexuals More Apt to be Homosexual’ (Cameron, 2006) is chairman of the Family Research Institute (FRI), a conservative organization whose mandate is to preserve ‘America’s historic moral framework and the traditional family’ (http://www.familyresearchinst.org/; accessed 18th June 2006). The FRI states that research in scientific journals is needed to prove that ‘homosexuality is a public health threat and a clear and present danger to our civilization’ (http://www.familyresearchinst.org/Default.aspx?tabid = 145; accessed 18th June 2006).
Open and informal online communities as forums of collaborative musical activities and learning
Authors: Salavuo Miikka
Published: November 2006

Distributing one's music and discussing music-related topics at dedicated web sites have become a common practice for today's young musicians. Technological advances allow both easy production of music at computer-based home studios and free distribution even at a global level. An online survey was conducted to shed light on the reasons for participating in an online music community. The results indicate that although social reasons existed, musical reasons were the most important motives for taking part in the community. The participants were on average fairly active musicians, but only a minority of them had formal musical training.
Internal structure of Rhea
Authors: Castillo‐Rogez Julie
Published: November 2006

We model the interior of Rhea on the basis of observational constraints and the results from geodynamical models available in the literature. Ten main types of models are defined, depending on the presence or absence of a high‐pressure ice layer (ice II), and the extent of separation of the rock component from the volatiles. The degree‐two gravity coefficients are computed for each of these models in order to assess which properties of the interior are likely to be inferred from Cassini radio science measurements scheduled on 26 November 2005. C22 greater than 2.5 × 10−4 indicates that the satellite is undifferentiated, except for a slight increase in density with depth resulting from material self‐compression. C22 between 1.67 × 10−4 (lower bound) and 1.90 × 10−4 indicates the presence of a rocky core, whose radius can be determined from the satellite's mass and ices densities, for a given temperature profile. For other values, most of the ten models cannot be distinguished from each other. However, assumptions on the density of the rock phase, presence or absence of ice II, and the degree of differentiation could allow a unique model to be determined in many cases. While the calculation presented in this work assumes that Rhea is in hydrostatic equilibrium, it is likely that Rhea' gravity field is partly affected by nonhydrostatic anomalies.
Optimization and sensitivity study of a biogeochemistry ocean model using an implicit solver and in situ phosphate data
Authors: Kwon Eun Young , Primeau Francois
Published: November 2006

A new implicit method for obtaining equilibrium solutions and their sensitivity to changes in parameters is described and applied to an OCMIP‐2 type ocean‐biogeochemistry model. The method is used to optimize model parameters by minimizing the difference between the observed and simulated PO4 distribution. The optimized parameters include (1) the exponent α in the power law vertical profile for particulate organic matter (POM) fluxes, (2) the fraction σ of biological production allocated to dissolved organic matter (DOM) and (3) the rate constant κ for the remineralization of DOM. Global PO4 observations constrain σ and κ but not independently because their sensitivity patterns are highly correlated. In contrast, the sensitivity pattern for α is uncorrelated to those of the other parameters, allowing it to be independently constrained. We show that export production from POC is well constrained by the distribution of PO4 in an OCMIP‐2 type model, but that new production and export production from DOC are not well constrained. With the optimal parameter set (α = −1.0, σ = 0.74, and κ = 1.0 yrs−1) the fraction of the spatial PO4 variance captured by our model increases from 60% with the reference OCMIP‐2 parameters to 70%. Combined changes in σ and κ account for most of the improvements by reducing but not completely eliminating the nutrient trapping effect in the Eastern Equatorial Pacific and northern Indian Ocean that causes the model to over‐predict PO4 concentrations. Important remaining model‐data misfits in the deep North Atlantic where PO4 is over predicted and in the North Pacific where the model does not produce the observed sharp nutricline are likely attributable to deficiencies in ocean transport. The fact that the fraction of unexplained variance is large at the optimal parameter values highlights the importance of properly simulating physical transport for ocean biogeochemical modeling.
Ballooning instability at the plasma sheet–lobe interface and its implications for polar arc formation
Authors: Golovchanskaya I. V. , Kullen A. , Maltsev Y. P. , Biernat H.
Published: November 2006

Huang et al. (1987, 1989) reported hot filaments of plasma sheet origin filling the magnetospheric lobes during northward interplanetary magnetic field (IMF). On the other hand, cold plasma transients of presumably lobe origin are often observed in the plasma sheet. These features can be interpreted in terms of plasma exchange at the plasma sheet–lobe interface (PSLI) proceeding in a filamentary manner. We present a description of this process within ballooning destabilizing of the near‐Earth curved segment of the PSLI. Although the basic ballooning instability condition is not typically met inside the plasma sheet, it is satisfied at this segment. The PSLI always separates the cold lobe population from the hot plasma sheet, thus providing a pressure gradient favorable for the instability; its near‐Earth part has a nonnegligible magnetic curvature. A solution for the least stable ballooning harmonics is found, which satisfies the finite conductivity boundary condition in the ionosphere and the outgoing Alfvén wave condition at the tailward end of the near‐Earth curved segment of the plasma sheet boundary. We show that this part of the PSLI may be a generator region launching filamentation. The background convection is imposed on the ballooning motions. The large‐scale convection associated with southward IMF Bz suppresses hot filament progression into the lobes, while promoting penetration of lobe transients into the plasma sheet. However, during northward IMF, the convection favors at certain magnetic local times the extension of plasma sheet filaments into the lobes and their subsequent protrusion toward noon. This process is signified in the ionosphere by the occurrence of nightside originating polar arcs. Several polar arc events are shown that develop from the nightside oval boundary into the polar cap on timescales of approximately 10–15 min, consistent with the growth rates of the studied instability.
SiGe quantum dot single-hole transistor fabricated by atomic force microscope nanolithography and silicon epitaxial-regrowth
Authors: Bo Xiang-Zheng , Rokhinson L. P. , Yao N. , Tsui D. C. , Sturm J. C.
Published: November 2006

A SiGe quantum dot single-hole transistor passivated by silicon epitaxial regrowth with extremely stable Coulomb blockade oscillations has been demonstrated. The quantum dot was defined by atomic force microscopy nanopatterning technique and subsequently passivated by the epitaxial regrowth of silicon. Such passivation of the dot avoids any potential defect states on the dot associated with the Si∕SiO2 interface. Coulomb blockade oscillations controlled by side planar gating at ∼0.3K are reproducible, in sharp contrast with the noisy and irreproducible I-V characteristics of unpassivated SiGe quantum dot devices. An additional top gate was used to further tune the Coulomb blockade oscillations, enabling a shift in side-gate voltage of up to three periods.
Microstructure and electrical property correlations in Ga:ZnO transparent conducting thin films
Authors: Bhosle V. , Narayan J.
Published: November 2006

In this paper, we report correlations between processing, microstructure, and electrical properties of Ga doped ZnO films. Films with different grain sizes were grown on amorphous glass substrate by changing the substrate and pulsed laser deposition variables. The results corresponding to these films were compared with those from epitaxial single crystal films grown on (0001) sapphire. Microstructural characteristics were analyzed in detail by using x-ray diffraction and transmission electron microscopy. Electrical properties were evaluated by resistivity measurements in the temperature range of 15–300K and Hall measurements at room temperature. It was observed that the grain boundaries and orientation of grains (texture characteristics) affected the carrier concentration and the mobility considerably in nanocrystalline films deposited on glass substrates. This effect is envisaged to occur as a result of trapping of electrons and buildup of a potential barrier across the grain boundaries. However, the resistivity in nanocrystalline films could be decreased significantly by carefully controlling the deposition conditions. For a film deposited on glass at 200°C and 1mtorr of oxygen partial pressure, we attained a minimum resistivity value of 1.8×10−4Ωcm. The epitaxial films on sapphire substrates showed a resistivity of 1.4×10−4Ωcm, deposited at 400°C and pressure of 2.4×10−2torr. The role of grain boundaries and defects in controlling the carrier generation and transport has been discussed in detail and the possible mechanisms limiting the electrical conductivity in films with different microstructures have also been identified.
Concentration and penetration depth of H introduced into crystalline Si by hydrogenation methods used to fabricate solar cells
Authors: Kleekajai S. , Jiang F. , Stavola Michael , Yelundur V. , Nakayashiki K. , Rohatgi A. , Hahn G. , Seren S. , Kalejs J.
Published: November 2006

The hydrogenation of crystalline Si by methods used to passivate defects in Si solar cells has been studied by infrared spectroscopy. For these experiments, floating-zone Si that contained Pt impurities that act as traps for H was used as a model system in which H could be directly detected. In this model system, the concentration and indiffusion depth of H were determined for different hydrogenation treatments so that their effectiveness could be compared. The postdeposition annealing of a hydrogen-rich SiNx surface layer was found to introduce H into the Si bulk with a concentration of ∼1015cm−3 under the best conditions investigated here.
Thiol and thiolate bond formation of ferrocene-1,1-dithiol to a Ag(111) surface
Authors: Meyer J. , Bredow T. , Tegenkamp C. , Pfnür H.
Published: November 2006

Using density functional calculations, we show that the adsorption of ferrocene dithiol on the Ag(111) surface is remarkably flexible, i.e., a large number of different configurations have binding energies that differ by less than 0.1eV per molecule. The thiolate bond is slightly favored over the thiol bond (by less than 0.1eV) but may not be formed due to considerable activation barriers. Electronically, we found that the thiolate bound molecule is conducting, whereas thiol bonds turn it into semiconducting.
Dissociative recombination of ammonia clusters studied by storage ring experiments
Authors: Öjekull J. , Andersson P. U. , Någård M. B. , Pettersson J. B. C. , Neau A. , Rosén S. , Thomas R. D. , Larsson M. , Semaniak J. , Österdahl F. , Danared H. , Källberg A. , Ugglas M. af.
Published: November 2006

Dissociative recombination of ammonia cluster ions with free electrons has been studied at the heavy-ion storage ring CRYRING (Manne Siegbahn Laboratory, Stockholm University). The absolute cross sections for dissociative recombination of H+(NH3)2, H+(NH3)3, D+(ND3)2, and D+(ND3)3 in the collision energy range of 0.001–27eV are reported, and thermal rate coefficients for the temperature interval from 10to1000K are calculated from the experimental data and compared with earlier results. The fragmentation patterns for the two ions H+(NH3)2 and D+(ND3)2 show no clear isotope effect. Dissociative recombination of X+(NX3)2 (X=H or D) is dominated by the product channels 2NX3+X [0.95±0.02 for H+(NH3)2 and 1.00±0.02 for D+(ND3)2]. Dissociative recombination of D+(ND3)3 is dominated by the channels yielding three N-containing fragments (0.95±0.05).
Inner-shell excitation spectroscopy and fragmentation of small hydrogen-bonded clusters of formic acid after core excitations at the oxygen K edge
Authors: Tabayashi Kiyohiko , Yamamoto Keisuke , Takahashi Osamu , Tamenori Yusuke , Harries James R. , Gejo Tatsuo , Iseda Mitsuhiro , Tamura Takashi , Honma Kenji , Suzuki Isao H. , Nagaoka Shin-ichi , Ibuki Toshio
Published: November 2006

Inner-shell excitation spectra and fragmentation of small clusters of formic acid have been studied in the oxygen K-edge region by time-of-flight fragment mass spectroscopy. In addition to several fragment cations smaller than the parent molecule, we have identified the production of HCOOH∙H+ and H3O+ cations characteristic of proton transfer reactions within the clusters. Cluster-specific excitation spectra have been generated by monitoring the partial ion yields of the product cations. Resonance transitions of O1s(CO∕OH) electrons into πCO* orbital in the preedge region were found to shift in energy upon clusterization. A blueshift of the O1s(CO)→πCO* transition by ∼0.2eV and a redshift of the O1s(OH)→πCO* by ∼0.6eV were observed, indicative of strong hydrogen-bond formation within the clusters. The results have been compared with a recent theoretical calculation, which supports the conclusion that the formic-acid clusters consist of the most stable cyclic dimer and∕or trimer units. Specifically labeled formic acid-d, HCOOD, was also used to examine the core-excited fragmentation mechanisms. These deuterium-labeled experiments showed that HDO+ was formed via site-specific migration of a formyl hydrogen within an individual molecule, and that HD2O+ was produced via the subsequent transfer of a deuterium atom from the hydroxyl group of a nearest-neighbor molecule within a cationic cluster. Deuteron (proton) transfer from the hydroxyl site of a hydrogen-bond partner was also found to take place, producing deuteronated HCOOD∙D+ (protonated HCOOH∙H+) cations within the clusters.
Organic tandem solar cells comprising polymer and small-molecule subcells
Authors: Colsmann Alexander , Junge Johannes , Kayser Christian , Lemmer Uli
Published: November 2006

In this work the authors report monolithic organic tandem solar cells. The front cell is fabricated from a blend of poly(3-hexylthiophene-2,5-diyl) and [6,6]-phenyl C61-butyric acid methyl ester while a copper phthalocyanine/fullerene (CuPc∕C60) bilayer is used for the back cell. An intermediate recombination zone is realized using two doped organic semiconductor layers and a thin noble metal interlayer. The active polymer layer thickness is optimized to ensure matching of the subcell currents. The open circuit voltage Voc=1V nearly reaches the sum of the open circuit voltages of each contributing cell.
Method to determine argon metastable number density and plasma electron temperature from spectral emission originating from four 4p argon levels
Authors: Mariotti Davide , Shimizu Yoshiki , Sasaki Takeshi , Koshizaki Naoto
Published: November 2006

A simple model and method is proposed here to determine argon metastable number densities and electron temperature with the assumption of a Maxwell-Boltzmann electron energy distribution. This method is based on the availability of experimental relative emission intensities of only four argon lines that originate from any of the 4p argon levels. The proposed model has a relatively wide range of validity for laboratory plasmas that contain argon gas and can be a valuable tool for the emerging field of atmospheric microplasmas, for which diagnostics is still limited.
Dependence of resonant coupling between surface plasmons and an InGaN quantum well on metallic structure
Authors: Chen Cheng-Yen , Yeh Dong-Ming , Lu Yen-Cheng , Yang C. C.
Published: November 2006

The authors demonstrate the metallic-structure dependent surface plasmon (SP) coupling behaviors with a blue-emitting InGaN∕GaN quantum well (QW), which is 10nm away from the metallic structures. The SP-QW coupling behaviors in the areas of semiconductor surface coated with silver thin film and silver nanoparticles are compared. It is found that both the suppression of photoluminescence (PL) intensity and the reduction of time-resolved PL (TRPL) decay time strongly depend on the metallic morphology. A phenomenological model of carrier relaxation in the SP-QW coupling process is built to fit the TRPL decay profiles for calibrating the reasonable decay time constants of carrier and SP.
Alan M. Sargeson
Authors: Harrowfield J
Published: November 2006

No Abstract Available.
13C N.M.R. Spectroscopic Studies on the Reactions of Vanadium(V) With 13C2-Labeled Oxalate in Aqueous and 50% v/v Aqueous Acetic Acid Solutions
Authors: Farrell RP , Lay PA
Published: November 2006

13 C n.m.r, spectroscopy has been used to study the reactions of vanadate , H2VO4-, with 13C2-labelled oxalate in aqueous and 50% v/v aqueous acetic acid media. The results of the aqueous system corroborate the natural abundance oxalate 13C n.m.r. studies of Ehde and coworkers ( Ehde, P.M., Petterson , L., and Glaser, J., Acta Chem. Scand., 1991, 45, 998) who report the formation of both mono( oxalato )-, [VO2(ox)(OH2)] - , and bis(oxalato)-vanadium(V), cis-[VO2(ox)2]3-, complexes in solution. At 270 K, pH 3.3, and an n.m.r. operating frequency of 100.16 MHz, the former complex appears as a singlet (167.3 ppm ), while the latter resolves into an AB coupling pattern (169.6, 168.8, 166.6, 165.8 ppm ; Jc -c 85 Hz) owing to the inequivalence of carbons trans and cis to the oxo ligands . In 50% v/v aqueous acetic acid both the mono( oxalato ) singlet (166.8 ppm ) and the bis ( oxalato ) AB coupling pattern (169.2, 168.5, 166.2, 165.5 ppm ; Jc -c ≈ 75 Hz) are present but are somewhat broadened and shifted downfield, which is indicative of other species being present. There is also some resolution of new peaks within the broadened signals. These are believed to be due to the presence of the additional complexes, mainly [VO2(ox)( OAc )]2- and cis-[VO2(ox)( OAc )2]3-, generated in the acetic acid medium. At 298 K, the bis(oxalato) complex exhibits a single 13C peak for the inequivalent carbons at 167.6 ppm because of fluxional behaviour. The mono( oxalato ) complex is in rapid equilibrium with free oxalate, giving a second peak at lower value of 165.7 ppm that is pH-dependent. The mechanisms of the fluxionality of the different complexes are discussed.
Bridgehead Carbocations: Solvolysis of a Series of 5-Substituted Bicycle [3.1.1]heptyl Bromides. Nucleophilic Solvent Assistance to Ionization of 1-Bromobicyclo[3.1.1]heptane
Authors: Della EW , Elsey GM
Published: November 2006

The synthesis of a range of 5-substituted bicyclo [3.1.1] heptyl bromides for solvolytic studies is described. It is found that the substituent has a profound effect on the rate of solvolysis of the system and acts principally in accordance with the magnitude of its inductive/field constant σI. The most spectacular example of the effect of the substituent is provided by the COOMe group which leads to a retardation in the rate of methanolysis by a factor of 6.5°105. While a linear relationship in the plot of log k and σI is generally obeyed, as expected for a mechanism mediated by the bicyclo [3.1.1] heptyl bridgehead cation, two of the bromides, 1-bromobicyclo[3.1.1] heptane and its 5-methoxy derivative, show deviant behaviour and react more rapidly than predicted on the basis of the Hammett plot. Evidence is presented to show that the enhanced rate of the parent is the result of nucleophilic assistance by the solvent. Anchimeric assistance in the solvolysis of 5-methoxybicyclo[3.1.1] heptyl bromide is attributed to the powerful p-donor property of the methoxy substituent which stabilizes the transition state in a unique concerted ring-opening and ionization step.
Reaction of 2-Benzylseleno-N-trimethylsilylbenzamides With Phosgene: Preparation of Benzoselenazine-2,4-diones
Authors: Fong MC , Laws MJ , Schiesser CH
Published: November 2006

Treatment of N-alkyl-2-benzylseleno-N-trimethylsilylbenzamides, prepared from the N-substituted benzamide (3) or (8; R = primary alkyl, phenyl) by reaction with trimethylsilyl triflate, with phosgene in ether affords the benzoselenazine-2,4-dione ring system (7) or (9) in good yield.
Nitrate Selectivity of Ion-Exchange Resins and of Their Model Compounds. II. Viscosity and Density of Benzyltrialkylammonium Salts in Aqueous Solution and 14N N.M.R. Relaxation of the Nitrate Ion
Authors: Owens G , Guarilloff P , Kurucsev T
Published: November 2006

The densities and viscosities of benzyltrialkylammonium chlorides and nitrates were determined in aqueous solution; the alkyl substituents were methyl, ethyl, propyl , butyl and pentyl . The concentration dependence of the 14N nuclear spin relaxation of the nitrate ion was used to find ion pair association constants for comparison with those derived from conductivity measurements (Part I). Density measurements were used to determine partial molar volumes, and viscosity measurements to find hydrodynamic volumes of the solutes. With the assumption of additivity of ionic volumes, cationic volumes calculated from the two series of chloride and nitrate salts agreed well. The increase in the ratio of hydrodynamic to partial ionic volumes with increasing chain length of the alkyl substituent was interpreted as a corresponding increase in hydrophobic hydration.
A New Furanoditerpene From a Southern Australian Marine Sponge, Thorectandra choanoides
Authors: Urban S , Capon RJ
Published: November 2006

A specimen of the marine sponge Thorectandra choanoides from Bass Strait, Australia, has yielded the new furanoditerpene (7), the structure of which was secured by spectroscopic analysis.
A signature pattern of stress-responsive microRNAs that can evoke cardiac hypertrophy and heart failure
Authors: van Rooij Eva , Sutherland Lillian B. , Liu Ning , Williams Andrew H. , McAnally John , Gerard Robert D. , Richardson James A. , Olson Eric N.
Published: November 2006

Diverse forms of injury and stress evoke a hypertrophic growth response in adult cardiac myocytes, which is characterized by an increase in cell size, enhanced protein synthesis, assembly of sarcomeres, and reactivation of fetal genes, often culminating in heart failure and sudden death. Given the emerging roles of microRNAs (miRNAs) in modulation of cellular phenotypes, we searched for miRNAs that were regulated during cardiac hypertrophy and heart failure. We describe >12 miRNAs that are up- or down-regulated in cardiac tissue from mice in response to transverse aortic constriction or expression of activated calcineurin, stimuli that induce pathological cardiac remodeling. Many of these miRNAs were similarly regulated in failing human hearts. Forced overexpression of stress-inducible miRNAs was sufficient to induce hypertrophy in cultured cardiomyocytes. Similarly, cardiac overexpression of miR-195, which was up-regulated during cardiac hypertrophy, resulted in pathological cardiac growth and heart failure in transgenic mice. These findings reveal an important role for specific miRNAs in the control of hypertrophic growth and chamber remodeling of the heart in response to pathological signaling and point to miRNAs as potential therapeutic targets in heart disease.
Dynamic Pricing and Consumer Fairness Perceptions
Authors: Haws Kelly L. , Bearden William O.
Published: November 2006

Dynamic pricing practices by sellers in response to segment and individual-level differences have been made more feasible as internet buyer behavior increases. While benefits from these pricing practices can accrue to sellers and buyers, the potential for (un)fairness perceptions to mitigate these advantages is important. In an effort to investigate these issues, this article reports the results of three studies that examine the effects of seller-, consumer-, time-, and auction-based price differences on perceived price fairness and purchase satisfaction. The findings underscore the potential negative effects associated with price differences from dynamic pricing practices.
Pol I Transcription and Pre-rRNA Processing Are Coordinated in a Transcription-dependent Manner in Mammalian Cells
Authors: Kopp K. , Gasiorowski J. Z. , Chen D. , Gilmore R. , Norton J. T. , Wang C. , Leary D. J. , Chan E.K.L. , Dean D. A. , Huang S.
Published: November 2006

Pre-rRNA synthesis and processing are key steps in ribosome biogenesis. Although recent evidence in yeast suggests that these two processes are coupled, the nature of their association is unclear. In this report, we analyze the coordination between rDNA transcription and pre-rRNA processing in mammalian cells. We found that pol I transcription factor UBF interacts with pre-rRNA processing factors as analyzed by immunoprecipitations, and the association depends on active rRNA synthesis. In addition, injections of plasmids containing the human rDNA promoter and varying lengths of 18S rDNA into HeLa nuclei show that pol I transcription machinery can be recruited to rDNA promoters regardless of the product that is transcribed, whereas subgroups of pre-rRNA processing factors are recruited to plasmids only when specific pre-rRNA fragments are produced. Our observations suggest a model for sequential recruitment of pol I transcription factors and pre-rRNA processing factors to elongating pre-rRNA on an as-needed basis rather than corecruitment to sites of active transcription.
Internalization of Large Double-Membrane Intercellular Vesicles by a Clathrin-dependent Endocytic Process
Authors: Piehl Michelle , Lehmann Corinna , Gumpert Anna , Denizot Jean-Pierre , Segretain Dominique , Falk Matthias M.
Published: November 2006

Beyond its well-documented role in vesicle endocytosis, clathrin has also been implicated in the internalization of large particles such as viruses, pathogenic bacteria, and even latex beads. We have discovered an additional clathrin-dependent endocytic process that results in the internalization of large, double-membrane vesicles at lateral membranes of cells that are coupled by gap junctions (GJs). GJ channels bridge apposing cell membranes to mediate the direct transfer of electrical currents and signaling molecules from cell to cell. Here, we report that entire GJ plaques, clusters of GJ channels, can be internalized to form large, double-membrane vesicles previously termed annular gap junctions (AGJs). These internalized AGJ vesicles subdivide into smaller vesicles that are degraded by endo/lysosomal pathways. Mechanistic analyses revealed that clathrin-dependent endocytosis machinery-components, including clathrin itself, the alternative clathrin-adaptor Dab2, dynamin, myosin-VI, and actin are involved in the internalization, inward movement, and degradation of these large, intercellular double-membrane vesicles. These findings contribute to the understanding of clathrin's numerous emerging functions.
Misfolded Proteins Traffic from the Endoplasmic Reticulum (ER) Due to ER Export Signals
Authors: Kincaid Margaret M. , Cooper Antony A.
Published: November 2006

Most misfolded secretory proteins remain in the endoplasmic reticulum (ER) and are degraded by ER-associated degradation (ERAD). However, some misfolded proteins exit the ER and traffic to the Golgi before degradation. Using model misfolded substrates, with or without defined ER exit signals, we found misfolded proteins can depart the ER by continuing to exhibit the functional export signals present in the corresponding correctly folded proteins. Anterograde transport of misfolded proteins utilizes the same machinery responsible for exporting correctly folded proteins. Passive ER retention, in which misfolded proteins fail to exit the ER due to the absence of exit signals or the inability to functionally present them, likely contributes to the retention of nonnative proteins in the ER. Intriguingly, compromising ERAD resulted in increased anterograde trafficking of a misfolded protein with an ER exit signal, suggesting that ERAD and ER exit machinery can compete for binding of misfolded proteins. Disabling ERAD did not result in transport of an ERAD substrate lacking an export signal. This is an important distinction for those seeking possible therapeutic approaches involving inactivating ERAD in anticipation of exporting a partially active protein.
Characterization of AtNUC-L1 Reveals a Central Role of Nucleolin in Nucleolus Organization and Silencing of AtNUC-L2 Gene in Arabidopsis
Authors: Pontvianne Frederic , Matía Isabel , Douet Julien , Tourmente Sylvette , Medina Francisco J. , Echeverria Manuel , Sáez-Vásquez Julio
Published: November 2006

Nucleolin is one of the most abundant protein in the nucleolus and is a multifunctional protein involved in different steps of ribosome biogenesis. In contrast to animals and yeast, the genome of the model plant Arabidopsis thaliana encodes two nucleolin-like proteins, AtNUC-L1 and AtNUC-L2. However, only the AtNUC-L1 gene is ubiquitously expressed in normal growth conditions. Disruption of this AtNUC-L1 gene leads to severe plant growth and development defects. AtNUC-L1 is localized in the nucleolus, mainly in the dense fibrillar component. Absence of this protein in Atnuc-L1 plants induces nucleolar disorganization, nucleolus organizer region decondensation, and affects the accumulation levels of pre-rRNA precursors. Remarkably, in Atnuc-L1 plants the AtNUC-L2 gene is activated, suggesting that AtNUC-L2 might rescue, at least partially, the loss of AtNUC-L1. This work is the first description of a higher eukaryotic organism with a disrupted nucleolin-like gene and defines a new role for nucleolin in nucleolus structure and rDNA chromatin organization.