bluuebunny/crossref_metadata_2025 huggingface dataset:
In vitro effects of fat, FA, and cholesterol on sphingomyelin hydrolysis induced by rat intestinal alkaline sphingomyelinase
Authors: Liu Jian‐Jun , Nilsson Åke , Duan Rui‐Dong
Published: November 2006

Dietary sphingomyelin (SM) may have regulatory effects on cell proliferation and tumorigenesis in the colon. Alkaline sphingomyelinase (SMase) is the major enzyme responsible for hydrolysis of SM in the gut. Previously we purified the enzyme and showed that the presence of glycerophospholipids inhibited SM hydrolysis induced by alkaline SMase in vitro. In the present work, we studied the effects of TG, DG, FA, ceramide, and cholesterol on SM hydrolysis catalyzed by purified alkaline SMase. The results showed that both TG (triolein and tristearin) and DG (1,2‐dioleoyl‐sn‐glycerol and 1,2‐distearoyl‐rac‐glycerol) inhibited the activity of alkaline SMase. 1‐Mono‐oleoyl‐rac‐glycerol, 1‐monostearoyl‐rac‐glycerol, stearic acid, oleic acid, linoleic acid, linolenic acid, and arachidonic acid stimulated the activity of alkaline SMase at 0.4–0.8 mM concentrations but inhibited the enzyme at higher concentrations. There was no difference between the effects induced by saturated and unsaturated FA. A short‐chain FA such as lauric acid had a stronger stimulatory effect at low concentrations and weaker inhibitory effect at high concentrations than long‐chain FA. Choosing linoleic acid as an example, we found that FA had similar effects on both alkaline SMase and neutral SMase. Cholesterol and ceramide when mixed with FA to increase its solubility in bile salt micelles inhibited SMase activity. In conclusion, glycerides, FA, ceramide, and cholesterol influence SM hydrolysis catalyzed by intestinal alkaline SMase. The presence of lipids in the diet may thus influence the course of SM digestion in the gut and thereby the exposure of colon to SM metabolites.
Impact of Dietary FA and Energy Restriction on Plasma Leptin and ob Gene Expression in Mice
Authors: Gregersen Søren , Thomsen Janus L. , Jeppesen Per B. , Alstrup Kirsten K. , Brock Birgitte , Pedersen Steen B. , Kristensen Kurt , Hermansen Kjeld
Published: November 2006

The aim of the present study was to elucidate whether the qualitative compositiion of dietary fat influences plasma leptin and adipose tissue ob gene expression differentially. Two high‐fat diets and a diet rich in carbohydrate were each administered both ad libitum and with a 25% energy restriction. The high‐fat diets contained 58 energy percent as either monounsaturated FA (MUFA) or saturated FA (SAFA), whereas the carbohydrate‐rich diet (CH) contained 7 energy percent as fat. We aimed at obtaining the same final weight for the animals in the ad libitum group as in the energy‐restricted groups. This goal was reached at he same time (days 22–24) for all groups except for the ad libitum animals fed on saturated fat (day 36). The plasma leptin concentrations on ad libitum CH and MUFA diets did not differ significantly (24.3 ± 2.1 and 34.7 ± 6.7 ng/mL, respectively) whereas the saturated fat diet caused a lower concentration (13.9 ± 1.9 ng/mL; P < 0.05). Interestingly, no differences in plasma leptin levels between groups were seen in the energy‐restricted groups (mean 8.0 + 1.0 ng/mL). The type of diet did not alter the ob gene expression in intraabdominal white adipose tissue; however, a lower expression level was found in the energy‐restricted groups. The percentage of body fat in the three ad libitum fed groups did not differ (23 ± 1%). Thus, short‐term administration of a diet rich in SAFA suppresses circulating leptin levels without altering the adipose tissue ob gene expression. This indicates that saturated fat may alter protein handling by adipose tissue or the whole body clearance of leptin.
A comparison of the effect of medium‐ vs. long‐chain triglycerides on the in vitro solubilization of cholesterol and/or phytosterol into mixed micelles
Authors: von Bonsdorff‐Nikander Anna , Christiansen Leena , Huikko Laura , Lampi Anna‐Maija , Piironen Vieno , Yliruusi Jouko , Kaukonen Ann Marie
Published: November 2006

Despite clinical evidence of the cholesterol‐lowering effects of phytosterols, the exact mechanisms involved are still unclear. Displacement of cholesterol by phytosterols from mixed micelles, which is due to their greater hydrophobicity, is one of the hypotheses for the lumenal effects contributing to the reduction of intestinal cholesterol absorption. In this study a dynamic in vitro lipolysis method was used to examine the solubilization behavior of cholesterol and/or phytosterols during lipolysis to probe the efficacy of cholesterol displacement from mixed micelles by phytosterols. The effects of lipid chain length on sterol solubilization were studied by using microcrystalline suspensions containing 17% phytosterol or cholesterol, formulated in long‐chain TG (LCT) and medium‐chain TG (MCT). When digesting cholesterol suspended in LCT, the entire cholesterol dose was incorporated into the micellar phase. For the cholesterol formulation suspended in MCT, 50.3% of the initial dose was recovered in the micelles. Under the respective conditions, we observed lower solubilization of phytosterols than of cholesterol (roughly fourfold). Only 25% of the initial phytosterol dose was solubilized from suspensions formulated with LCT, and 13% was solubilized from MCT formulations. Co‐administration of phytosterol and cholesterol suspensions showed a significant reduction of cholesterol solubilization, particularly when dosed in MCT, with ≈25% of the cholesterol dose solubilized. Insignificant amounts of cholesterol were displaced by phytosterols when cholesterol was presolubilized in the mixed micelles. The results show that, compared with LCT, mixed micelles containing MCT lipolysis products have a reduced solubilizing capacity for cholesterol, which adds to the effectiveness of the phytosterols in displacing cholesterol. This suggests potential benefits of using medium chain length lipids in cholesterol‐lowering phytosterol products.
Fatty acid composition of wild and farmed Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss)
Authors: Blanchet Carole , Lucas Michel , Julien Pierre , Morin Richard , Gingras Suzanne , Dewailly Éric
Published: November 2006

The goal of this study was to examine the FA composition of wild and farmed Atlantic salmon (AS) and rainbow trout (RT). FA profiles were obtained by GC/FID. Results showed that lipid and n−3 highly unsaturated FA contents of farmed and wild AS were similar. Total n−3 and n−6 PUFA were significantly higher in farmed AS than in wild AS. Farmed RT contained more fat and less n−3 PUFA than wild RT. Our results show that farmed salmonids provide high levels of n−3 HUFA to consumers.
Trans fatty acids and atopic eczema/dermatitis syndrome: The relationship with a free radical cis‐trans isomerization of membrane lipids
Authors: Ferreri Carla , Angelini Federica , Chatgilialoglu Chryssostomos , Dellonte Sergio , Moschese Viviana , Rossi Paolo , Chini Loredana
Published: November 2006

The formation of trans FA residues in membrane phospholipids may be due to a free radical‐catalyzed isomerization process occurring to the cis unsaturated FA moieties. Radical stress is well documented in inflammatory processes of atopic diseases, but no data are yet available about a possible association with trans FA detected in these patients. We investigated the presence of trans lipid isomers in the erythrocyte and T‐lymphocyte membranes of 26 children affected by atopic eczema/dermatitis syndrome (AEDS). Trans lipid isomers were found in both cell membranes, up to a total content of 2.7 and 4.9% of the FA composition, respectively. By using the geometrical trans lipid library derived from in vitro models of thiyl radical‐catalyzed isomerization, oleic and arachidonic acid isomers were detected. The statistical significance was evaluated by comparison with an age‐matched control group. These results suggest the role of an endogenous free radical isomerization path occurring to membrane unsaturated lipids, complementary to the dietary contribution, which can be involved in the lipid impairment in AEDS. This study contributes to lipidomic research regarding the double bond structure and the influence of a geometrical change of membrane lipids in physiology and diseases.
Fish oil supplementation of lactating mothers affects cytokine production in 2 1/2‐year‐old children
Authors: Lauritzen Lotte , Kjær Tanja M. R. , Fruekilde Maj‐Britt , Michaelsen Kim F. , Frøkiær Hanne
Published: November 2006

n−3 PUFA influence immune functioning and may affect the cytokine phenotype during development. To examine whether maternal fish oil supplementation during lactation could modify later immune responses in children, 122 lactating Danish mothers with a fish intake below the population median were randomized to groups supplemented for the first 4 mon of lactation with 4.5 g/d of fish oil (equivalent to 1.5 g/d of n−3 long‐chain PUFA) or olive oil. Fifty‐three mothers with a fish intake in the highest quartile of the population were also included. The FA composition of erythrocyte membranes was measured at 4 mon and at 2 1/2 yr. Plasma immunoglobulin E (IgE) levels and cytokine production in lipopolysaccharide‐stimulated whole‐blood cultures were determined at 2 1/2 yr. Erythrocyte n−3 PUFA at 4 mon were higher in infants from the fish oil group compared with the olive oil group (P<0.001) but were no longer different at 2 1/2 yr. The median production of lipopolysaccharide‐induced interferon γ(IFN‐γ) in the fish oil group was fourfold higher than that in the olive oil group (P=0.034), whereas interleukin‐10 (IL‐10) production was similar. The IFN‐γ/IL‐10 ratio was twofold higher in the fish oil group (P=0.019) and was positively correlated with 20∶5n−3/20∶4n−6 in erythrocytes at 4 mon (P=0.050). The percentages of atopic children and plasma IgE were not different in the two groups, but the study was not designed to look at atopy. Cytokine responses and erythrocyte FA composition in children of mothers with a high fish intake were intermediate in comparison with those in the randomized groups. Fish oil supplementation during lactation resulted in increasedin vitroIFN‐γ production in the children 2 yr after the supplementation was given, which may reflect a faster maturation of the immune system.
Plasma kinetic behavior in hyperlipidemic subjects of a lipidic microemulsion that binds to low density lipoprotein receptors
Authors: Maranhão Raul C. , Roland Ivete A. , Toffoletto Odaly , Antonio Ramires José , Gonçalves Romélia P. , Mesquita Carlos H. , Pileggi Fulvio
Published: November 2006

It was previously reported that a protein‐free microemulsion (LDE) with structure roughly resembling that of the lipid portion of low density lipoprotein (LDL) was presumably taken up by LDL receptors when injected into the bloodstream. In contact with plasma, LDE acquires apolipoproteins (apo) including apo E that would be the ligand for receptor binding. Currently, apo were associated to LDE by incubation with high density lipoprotein (HDL). LDE‐apo uptake by mononuclear cells showed a saturation kinetics, with an apparent Km of 13.1 ng protein/mL. LDE‐apo is able to displace LDL uptake by mononuclear cells with a Ki of 11.5 ng protein/mL. LDE without apo is, however, unable to displace LDL. The uptake of 14C‐HDL is not dislocated by increasing amounts of LDE‐apo, indicating that HDL and LDE‐apo do not bind to the same receptor sites. In human hyperlipidemias, LDE labeled with 14C‐cholesteryl ester behaved kinetically as expected for native LDL. LDE plasma disappearance curve obtained from eight hypercholesterolemic patients was markedly slower than that from 10 control normolipidemic subjects [fractional clearance rate (FCR)=0.02±0.01 and 0.12±0.04 h−1, respectively; P<0.0001]. On the other hand, in four severely hypertriglyceridemic patients, LDE FCR was not significantly different from the controls (0.07±0.03 h−1). These results suggest that LDE can be a useful device to study lipoprotein metabolism.
Development and application of an ethically and epidemiologically advantageous assay for the multi-locus microsatellite analysis of Schistosoma mansoni
Authors: GOWER C. M. , SHRIVASTAVA J. , LAMBERTON P. H. L. , ROLLINSON D. , WEBSTER B. L. , EMERY A. , KABATEREINE N. B. , WEBSTER J. P.
Published: November 2006

Non-availability of adult worms from living hosts remains a key problem in population genetic studies of schistosomes. Indirect sampling involving passage through laboratory animals presents significant ethical and practical drawbacks, and may result in sampling biases such as bottlenecking processes and/or host-induced selection pressures. The novel techniques reported here for sampling, storage and multi-locus microsatellite analysis of larval Schistosoma mansoni, allowing genotyping of up to 7 microsatellite loci from a single larva, circumvent these problems. The utility of these assays and the potential problems of laboratory passage, were evaluated using 7 S. mansoni population isolates collected from school-children in the Hoima district of Uganda, by comparing the associated field-collected miracidia with adult worms and miracidia obtained from a single generation in laboratory mice. Analyses of laboratory-passaged material erroneously indicated the presence of geographical structuring in the population, emphasizing the dangers of indirect sampling for population genetic studies. Bottlenecking and/or other sampling effects were demonstrated by reduced variability of adult worms compared to their parent field-collected larval samples. Patterns of heterozygote deficiency were apparent in the field-collected samples, which were not evident in laboratory-derived samples, potentially indicative of heterozygote advantage in establishment within laboratory hosts. Genetic distance between life-cycle stages in the majority of isolates revealed that adult worms and laboratory-passaged miracidia clustered together whilst segregating from field miracidia, thereby further highlighting the utility of this assay.
Active learning and logarithmic opinion pools for HPSG parse selection
Authors: BALDRIDGE JASON , OSBORNE MILES
Published: November 2006

For complex tasks such as parse selection, the creation of labelled training sets can be extremely costly. Resource-efficient schemes for creating informative labelled material must therefore be considered. We investigate the relationship between two broad strategies for reducing the amount of manual labelling necessary to train accurate parse selection models: ensemble models and active learning. We show that popular active learning methods for reducing annotation costs can be outperformed by instead using a model class which uses the available labelled data more efficiently. For this, we use a simple type of ensemble model called theLogarithmic Opinion Pool(LOP). We furthermore show that LOPs themselves can benefit from active learning. As predicted by a theoretical explanation of the predictive power of LOPs, a detailed analysis of active learning using LOPs shows that component model diversity is a strong predictor of successful LOP performance. Other contributions include a novel active learning method, a justification of our simulation studies using timing information, and cross-domain verification of our main ideas using text classification.
Marked Prevention of Ischemic Brain Injury by Neu2000, an NMDA Antagonist and Antioxidant Derived from Aspirin and Sulfasalazine
Authors: Gwag Byoung Joo , Lee Young Ae , Ko Sun Young , Lee Moon Jung , Im Doo Soon , Yun Bok Sun , Lim Hyang Ran , Park Sun Mi , Byun Han Yeol , Son Sun Ju , Kwon Hye Jin , Lee Ji Yoon , Cho Jae-Young , Won Seok Joon , Kim Kee-Won , Ahn Young Min , Moon Ho Sang , Lee Hae Un , Yoon Sung Hwa , Noh Ji-Hyun , Chung Jun-Mo , Cho Sung Ig
Published: November 2006

Excitotoxicity and oxidative stress mediate neuronal death after hypoxic—ischemic brain injury. We examined the possibility that targeting both N-methyl-d-aspartate (NMDA) receptor-mediated excitotoxicity and oxidative stress would result in enhanced neuroprotection against hypoxic—ischemia. 2-Hydroxy-5-(2,3,5,6-tetrafluoro-4-trifluoromethyl-benzylamino)-benzoic acid (Neu2000) was derived from aspirin and sulfasalazine to prevent both NMDA neurotoxicity and oxidative stress. In cortical cell cultures, Neu2000 was shown to be an uncompetitive NMDA receptor antagonist and completely blocked free radical toxicity at doses as low as 0.3 μmol/L. Neu2000 showed marked neuroprotection in a masked fashion using histology and behavioral testing in two rodent models of focal cerebral ischemia without causing neurotoxic side effects. Neu2000 protected against the effects of middle cerebral artery occlusion, even when delivered 8 h after reperfusion. Single bolus administration of the drug prevented gray and white matter degeneration and spared neurologic function for over 28 days after MACO. Neu2000 may be a novel therapy for combating both NMDA receptor-mediated excitotoxicity and oxidative stress, the two major routes of neuronal death in ischemia, offering profound neuroprotection and an extended therapeutic window.
Swift-heavy-ion-irradiation-induced enhancement in electrical conductivity of chemical solution deposited La0.7Ba0.3MnO3 thin films
Authors: Parmar R. N. , Markna J. H. , Kuberkar D. G. , Kumar Ravi , Rana D. S. , Bagve Vivas C. , Malik S. K.
Published: November 2006

Epitaxial thin films of La0.7Ba0.3MnO3 manganite, deposited using chemical solution deposition technique, were irradiated by 200MeV Ag+15 ions with a maximum ion dose up to 1×1012ions∕cm2. Temperature and magnetic-field-dependent resistivity measurements on all the films (before and after irradiation) reveal a sustained decrease in resistivity with increasing ion dose. A maximum dose of 1×1012ions∕cm2 suppresses resistivity by factors of 3 and 10 at 330K [insulator-metal (I-M) transition] and at 10K, respectively. On the other hand, with increasing ion dose, the magnetoresistance enhances in the vicinity of I-M transition but decreases at low temperatures. These results, corroborated by surface morphology of films, suggest that the origin of such properties lies in the irradiation induced improved crystallinity and epitaxial orientation, enhanced connectivity between grains and conglomeration of grains, which result in better conductivity at grain boundaries.
Dielectric behavior and ac conductivity study of NiO∕Al2O3 nanocomposites in humid atmosphere
Authors: Ahmad Mohamad M. , Makhlouf Salah A. , Khalil Kamal M. S.
Published: November 2006

Humidity sensing characteristics of NiO∕Al2O3 nanocomposites, prepared by sol-gel method, are studied by impedance spectroscopy. Modeling of the obtained impedance spectra with an appropriate equivalent circuit enables us to separate the electrical responses of the tightly bound chemisorbed water molecules on the grain surfaces and the loosely associated physisorbed water layers. Dependence of the dielectric properties and ac conductivity of the nanocomposites on relative humidity (RH) were studied as a function of the frequency of the applied ac signal in the frequency range of 0.1–105Hz. The electrical relaxation behavior of the investigated materials is presented in the conductivity formalism, where the conductivity spectra at different RHs are analyzed by the Almond-West formalism [D. P. Almond et al., Solid State Ionics 8, 159 (1983)]. The dc conductivity and the hopping rate of charge carriers, determined from this analysis, show similar dependences on RH, indicating that the concentration of mobile ions is independent of RH and is primarily determined by the chemisorption process of water molecules. Finally, the results are discussed in view of a percolation-type conduction mechanism, where mobile ions are provided by the chemisorbed water molecules and the percolation network is formed by the physisorbed water layers.
Optical coatings for improved contrast in longitudinal magneto-optic Kerr effect measurements
Authors: Cantwell P. R. , Gibson U. J. , Allwood D. A. , Macleod H. A. M.
Published: November 2006

We have studied the increases in the longitudinal magneto-optic Kerr effect signal contrast that can be achieved by the application of optical overlayers on magnetic films. For simple coatings, a factor of ∼3 improvement in signal contrast is possible. Matching the optical impedance of the magnetic material improves the raw Kerr signal and also reduces the sample reflectivity, yielding a large Kerr angle. The contrast can be optimized by increasing the rotated Kerr reflectivity component while maintaining enough of the base reflectivity Fresnel component to produce a strong signal. Calculations and experimental results are presented for single layer ZrO2 dielectric coatings on Ni along with calculations for a three-layer Au–ZrO2–Ni structure. Incidence angle effects are also presented.
Dimer statistics on a Bethe lattice
Authors: Harris A. B. , Cohen Michael
Published: November 2006

We discuss the exact solutions of various models of the statistics of dimer coverings of a Bethe lattice. We reproduce the well-known exact result for noninteracting hard-core dimers by both a very simple geometrical argument and a general algebraic formulation for lattice statistical problems. The algebraic formulation enables us to discuss loop corrections for finite dimensional lattices. For the Bethe lattice we also obtain the exact solution when either (a) the dimers interact via a short-range interaction or (b) the underlying lattice is anisotropic. We give the exact solution for a special limit of dimers on a Bethe lattice in a quenched random potential in which we consider the maximal covering of dimers on random clusters at site occupation probability p. Surprisingly the partition function for “maximal coverage” on the Bethe lattice is identical to that for the statistics of branched polymers when the activity for a monomer unit is set equal to −p. Finally we give an exact solution for the number of residual vacancies when hard-core dimers are randomly deposited on a one dimensional lattice.
Single chain in mean field simulations: Quasi-instantaneous field approximation and quantitative comparison with Monte Carlo simulations
Authors: Daoulas Kostas Ch. , Müller Marcus
Published: November 2006

The description of fluctuations by single chain in mean field (SCMF) simulations is discussed and the results of this particle-based self-consistent field technique are quantitatively compared to Monte Carlo simulations of the same discretized Edwards-Hamiltonian providing exact reference data. In SCMF simulations one studies a large ensemble of noninteracting molecules subjected to real, external fields by Monte Carlo simulations. The external fields approximate nonbonded, instantaneous interactions between molecules. In the self-consistent mean field theory the external fields are static and fluctuation effects are ignored. In SCMF simulations, the external fields fluctuate since they are frequently recalculated from the instantaneous density distribution of the ensemble of molecules. In the limit of infinitely high density or instantaneous update of the external fields, the SCMF simulation method accurately describes long-wavelength fluctuations. At high but finite updating frequency the accuracy depends on the discretization of the model. The accuracy is illustrated by studying the single chain structure and intermolecular correlations in polymer melts, and fluctuation effects on the order-disorder transition of symmetric diblock copolymers.
Three-dimensional displacement analysis of a piezoelectric tube scanner through finite element simulations of a tube assembly
Authors: Sun Qiao , Wolkow Robert A.
Published: November 2006

In this article, we focus on analyzing the tip displacement relation for a piezoelectric tube scanner used in scanning probe microscopes. In particular, the finite element model consists of a piezoelectric tube, a tip holder, and a tip in an effort to include the boundary effect on tube deflection. A large number of simulations are conducted for model validation and comparisons with results in the literature. Design formulas commonly suggested by piezotube manufacturers are also used to compare with our simulations. We show that the design formulas provide a good approximation of the tip displacement when tube’s aspect ratio is well above 2. In addition, the axial displacement of the tip in tube bending, also known as the coupling term, is analyzed through simulations. A ratio of 4 exists between the axial displacement in tube elongation and that in tube bending caused by energizing single quadrant electrode. The result is shown to be convenient to use to decouple motion in the orthogonal directions.
Six-circle diffractometer with atmosphere- and temperature-controlled sample stage and area and line detectors for use in the G2 experimental station at CHESS
Authors: Nowak D. E. , Blasini D. R. , Vodnick A. M. , Blank B. , Tate M. W. , Deyhim A. , Smilgies D.-M. , Abruña H. , Gruner S. M. , Baker S. P.
Published: November 2006

A new diffractometer system was designed and built for the G2 experimental station at the Cornell High Energy Synchrotron Source (CHESS). A six-circle κ goniometer, which provides better access to reciprocal space compared to Eulerian cradles, was chosen primarily to perform large angle Bragg diffraction on samples with preferred crystallographic orientations, and can access both horizontal and vertical diffraction planes. A new atmosphere- and temperature-controlled sample stage was designed for thin film thermomechanical experiments. The stage can be operated in ultrahigh vacuum and uses a Be dome x-ray window to provide access to all scattering vectors above a sample’s horizon. A novel design minimizes sample displacements during thermal cycling to less than 160μm over 900°C and the stage is motorized for easy height adjustments, which can be used to compensate for displacements from thermal expansion. A new area detector was built and a new line detector was purchased. Both detectors cover a large region in reciprocal space, providing the ability to measure time-resolved phenomena. A detailed description of the design and technical characteristics is given. Some capabilities of the diffractometer system are illustrated by a strain analysis on a thin metal film and characterization of organic thin films with grazing incidence diffraction. The G2 experimental station, as part of CHESS, is a national user facility and is available to external users by application.
SAXES, a high resolution spectrometer for resonant x-ray emission in the 400–1600eV energy range
Authors: Ghiringhelli G. , Piazzalunga A. , Dallera C. , Trezzi G. , Braicovich L. , Schmitt T. , Strocov V. N. , Betemps R. , Patthey L. , Wang X. , Grioni M.
Published: November 2006

We present a 5m long spectrometer for soft x rays to be used at a synchrotron radiation beamline for resonant x-ray emission spectroscopy and resonant inelastic x-ray scattering in the 400–1600eV energy range. It is based on a variable line spacing spherical grating (average groove density of 3200mm−1, R=58.55m) and a charge coupled device two dimensional detector. With an x-ray spot on the sample of 10μm, the targeted resolving power is higher than 10 000 at all energies below 1100eV and better than 7000 at 1500eV. The off-line tests made with Al and MgKα1,2 fluorescence emissions indicate that the spectrometer can actually work at 12 000 and 17 000 resolving power at the L3 edges of Cu (930eV) and of Ti (470eV), respectively. SAXES (superadvanced x-ray emission spectrometer) is mounted on a rotating platform allowing to vary the scattering angle from 25° to 130°. The spectrometer will be operational at the ADRESS (advanced resonant spectroscopies) beamline of the Swiss Light Source from 2007.
Ferromagnetic interlayer coupling and switching process of exchange coupled composite media
Authors: Shen W. K. , Wang Jian-Ping
Published: November 2006

The ferromagnetic coupling effects in the exchange coupled composite (ECC) magnetic recording media were studied by varying the interlayer thickness and the saturation magnetization (Ms) of the soft layer. A minimum coercivity was observed at a certain interlayer thickness for the ECC media with a low Ms soft layer. When the Ms of the soft layer was increased (700emu∕cm3 in this work), no interlayer was needed to get the lowest coercivity for the ECC media, which makes the ECC media practical for a manufacturing process. A method to characterize the ferromagnetic coupling strength for the ECC media was quantitatively proposed. The switching process of the ECC media was observed to consist of the reversible switching of the soft layer and the irreversible switching of the hard layer.
Phase separation and percolation of reversibly aggregating spheres with a square-well attraction potential
Authors: Babu Sujin , Gimel Jean Christophe , Nicolai Taco
Published: November 2006

Reversible aggregation of spheres is simulated using a novel method in which clusters of bound spheres diffuse collectively with a diffusion coefficient proportional to their radius. It is shown that the equilibrium state is the same as with other simulation techniques, but with the present method more realistic kinetics are obtained. The behavior as a function of volume fraction and interaction strength was tested for two different attraction ranges. The binodal and the percolation threshold were determined. The cluster structure and size distribution close to the percolation threshold were found to be consistent with the percolation model. Close to the binodal phase separation occurred through the growth of spherical dense domains, while for deep quenches a system spanning network is formed that coarsens with a rate that decreases with increasing attraction. We found no indication for arrest of the coarsening.
Transition from electron accumulation to depletion at InGaN surfaces
Authors: Veal T. D. , Jefferson P. H. , Piper L. F. J. , McConville C. F. , Joyce T. B. , Chalker P. R. , Considine L. , Lu Hai , Schaff W. J.
Published: November 2006

The composition dependence of the Fermi-level pinning at the oxidized (0001) surfaces of n-type InxGa1−xN films (0⩽x⩽1) is investigated using x-ray photoemission spectroscopy. The surface Fermi-level position varies from high above the conduction band minimum (CBM) at InN surfaces to significantly below the CBM at GaN surfaces, with the transition from electron accumulation to depletion occurring at approximately x=0.3. The results are consistent with the composition dependence of the band edges with respect to the charge neutrality level.
Magnetic field processing to enhance critical current densities of MgB2 superconductors
Authors: Dou S. X. , Yeoh W. K. , Shcherbakova O. , Horvat J. , Kim J. H. , Pan A. V. , Wexler D. , Li Y. , Li W. X. , Ren Z. M. , Munroe P. , Cui J. Z.
Published: November 2006

A magnetic field of up to 12T was applied during the sintering process of pure MgB2 and carbon nanotube (CNT) doped MgB2 wires. The authors have demonstrated that magnetic field processing results in grain refinement, homogeneity, and enhancement in Jc(H) and Hirr. The extent of improvement in Jc increases with increasing field. The Jc for a 10T field processed CNT doped sample increases by a factor of 3 at 10K and 8T and at 20K and 5T, respectively. Hirr for the 10T field processed CNT doped sample reached 9T at 20K, which exceeded the best value of SiC doped MgB2 at 20K. Magnetic field processing reduces the resistivity in CNT doped MgB2, straightens the entangled CNTs, and improves the adherence between CNTs and the MgB2 matrix.
High-performance microscale single-crystal transistors by lithography on an elastomer dielectric
Authors: Reese Colin , Chung Wook-Jin , Ling Mang-mang , Roberts Mark , Bao Zhenan
Published: November 2006

Organic single crystals have emerged as powerful tools for the exploration of the intrinsic charge transport properties of organic materials. To date, however, the limited number of fabrication techniques has forced a steep compromise between performance, reproducibility, range of feature sizes, gentle treatment of the single crystal, and facility of construction. Here the authors present a materials-general technique for the fabrication of single-crystal field-effect transistors with the use of a spin-coated elastomer gate dielectric and photolithographically defined source and drain electrodes. This allows the production of feature sizes and patterns previously impossible with reported elastomeric techniques yet yields devices with performance far superior to those fabricated on nonconformal dielectrics. The authors measure saturation-regime mobilities of 19.0 and 1.9cm2∕Vs for the semiconductors rubrene and pentacene, comparable to the best published values, and 2.4cm2∕Vs for tetracene, nearly double that previously reported. Device characteristics are indicative of good contact, with negligible hysteresis and exceptionally low normalized subthreshold swings.
Area-tunable micromirror based on electrowetting actuation of liquid-metal droplets
Authors: Wan Zhiliang , Zeng Hongjun , Feinerman Alan
Published: November 2006

The authors report a micromirror device actuated by electrowetting effect. The micromirror surface is formed by a liquid-metal droplet jetted on a substrate and then topped with a parylene/Teflon coated indium tin oxide glass slide. The droplet is deformed by a voltage applied across the parylene/Teflon film. The radius of micromirror is tuned from 13μm (0V) to 88μm (90V), and the normalized area increases from 0.2 to 0.94 accordingly. The switching time ranges from 1ms for a 350μm diameter droplet to 0.2ms for a 50μm one. A 4×1 micromirror array is demonstrated and switched simultaneously.
The Reaction of Organophosphorus Radicals With Vinyl Acetate and Acrylonitrile in the Presence of an Aminoxyl Radical Scavenger
Authors: Busfield WK , Grice ID , Jenkins ID
Published: November 2006

The radical-trapping technique employing 1,1,3,3-tetramethyl-1,3-dihydro-2H-isoindol-2-yloxyl (1) as a radical scavenger has been used to study the reaction of diphenylphosphinoyl (2) and dimethoxyphosphinoyl (3) radicals with vinyl acetate and acrylonitrile. The phosphorus- centred radicals were generated by hydrogen abstraction from diphenylphosphine oxide and dimethyl phosphite respectively. Diphenylphosphine oxide was approximately three times as reactive as dimethyl phosphite towards hydrogen abstraction by t- butoxyl radicals and four times as reactive as tetrahydrofuran (towards abstraction of an α-hydrogen). Diphenylphosphinoyl radicals were found to be relatively nucleophilic and, in competition experiments, reacted about an order of magnitude faster with acrylonitrile than with vinyl acetate. Dimethoxyphosphinoyl radicals were rather less nucleophilic and reacted only twice as fast with acrylonitrile as they did with vinyl acetate. In the presence of excess aminoxyl (1), both diphenylphosphinoyl and dimethoxyphosphinoyl radicals were efficiently scavenged to produce stable phosphinic and phosphate esters respectively. The rate of scavenging was close to diffusion-controlled (c. 1.8×109 1. mol-1 s-1).
Model Studies on the Construction of Side Chains for CD Intermediates of Vitamin D
Authors: Loughlin WA , Haynes RK
Published: November 2006

Application of Horner- Wittig methodology for the synthesis of vitamin D side chains was examined through selected model studies. A requirement for syn or threo α- hydroxy diphenylphosphine oxide intermediates was established. The successful conversion of the model phosphine oxide (7) into the alkene (13), which demonstrates the potential of this method, is described.
Crystal Structures of and Polarized Absorption-Spectroscopy in Racemic and Resolved [Ru(bpy)3] (ClO4)2 and [Zn(bpy)3] (ClO4)2Bpy=2,2'-Bipyridine
Authors: Krausz E , Riesen H , Rae AD
Published: November 2006

[Zn( bpy )3] (ClO4)2 and [ Ru ( bpy )3] (ClO4)2 are isomorphous in both their racemic and resolved crystal forms. The resolved materials are monohydrates and have a C 2, Z = 8, structure with two independent formula units on general sites in the asymmetric unit. The cations have the same chirality. The inherent threefold axis of each cation lies approximately parallel to the c axis. The unrelated racemic form has a C2/c, Z = 4, structure which is a commensurate modulation of a P3c1, Z = 2, parent structure, typified by the room-temperature structure of [ Ru ( bpy )3] (PF6)2. A primary, secondary and tertiary axis of P3c1 become the c, b and a axes respectively of C2/c, retaining a third of the symmetry elements of P3c1. The crystals grow as multiply contacted twins. This structure bas just one spectroscopic site with the cation lying on a twofold axis that passes through the metal and one of the bidendate ligands and relates the other two ligands to each other. This feature is particularly useful in the study of the optical spectroscopy of the metal-to- ligand charge transfer excitations of [ Ru ( bpy )3]2+ and related systems. A comparison of structural and spectral data indicates that the positions of the anions have a dominant influence on the relative energies of the metal-to- ligand excitations. An energy difference between excitations involving the two (lower-energy) equivalent ligands and the third ligand of the order of 800 cm-1 is indicated in both singlet and triplet regions for the racemic perchlorate. The absorption spectra of [ Ru ( bpy )3]2+and [Os( bpy )3]2+ in a number of crystalline hosts are compared and discussed.
Rates of Reaction of the Sulfoxides and Sulfones of Sulfur Mustard and 2-Chloroethyl Ethyl Sulfide With Hydroxide Ion in Water
Authors: Tilley RI , Leslie DR
Published: November 2006

The reactions of the sulfoxides and sulfones of sulfur mustard and an analogue, 2-chloroethyl ethyl sulfide, with hydroxide ion in aqueous solution at 25° have been studied. In contrast with the behaviour of the parent sulfides, for which exclusive substitution of chlorine is observed under comparable conditions, the oxidized compounds react through base-catalysed elimination of HCl to give the corresponding alkenes. Second-order rate constants for these reactions are reported and implications for the metabolism of sulfur mustard are discussed.
New Macrocyclic Ligands. VI. 20- to 22-Membered Dibenzo-Substituted Rings Incorporating Mixed Nitrogen, Oxygen and/or Sulfur Donor Atoms
Authors: Davis CA , Duckworth PA , Lindoy LF , Moody WE
Published: November 2006

The syntheses and characterization of 10 dibenzo-substituted macrocycles incorporating mixed nitrogen, oxygen and/or sulfur donor sets are reported. The new systems, which incorporate six potential donor sites, extend the range of related (potentially tetradentate and pentadentate) macrocyclic systems reported previously.
Assessing detection probabilities for the endangered growling grass frog (Litoria raniformis) in southern Victoria
Authors: Heard Geoffrey W. , Robertson Peter , Scroggie Michael P.
Published: November 2006

Assessment of the efficacy of survey techniques for determining species occurrence is crucial for the validation of wildlife survey data. We analysed repeated site-survey data for adults and larvae of the growling grass frog (Litoria raniformis) in order to estimate probabilities of detection for the species using alternative survey techniques. The estimated probability of detecting adults of L. raniformis at occupied sites using diurnal searches was much less than 1.0 (0.107; 95% credible interval: 0.045, 0.192). The estimated probability of detecting adults using nocturnal spotlight searches was considerably higher, but still less than 1.0 (0.696; 95% credible interval: 0.585, 0.796). These results indicate that nocturnal searches are a much more efficient and reliable means of detecting the presence of adult L. raniformis than diurnal searches, but detection using either technique is less than certain. The probability of detecting tadpoles of L. raniformis using either funnel-trapping or dip-netting techniques was estimated at 0.350 (95% credible interval: 0.151, 0.567). Together, these results indicate that reliance on single-site visits during surveys for this species is likely to result in severe under-estimation of the proportion of sites that are actually occupied. We urge other workers to use repeated site-survey data and appropriate methods of data analysis to assess and report probabilities of detection when documenting the results of wildlife surveys.
Three-dimensional use of space by a tropical rainforest rodent, Melomys cervinipes, and its implications for foraging and home-range size
Authors: Rader Romina , Krockenberger Andrew
Published: November 2006

This study investigated the factors that influence the home-range size of a tropical Australian rodent, Melomys cervinipes, using radio-tagged individuals. Melomys cervinipes frequently used the canopy and, when measured according to height level, its home-range areas were much larger than calculated by traditional two-dimensional home-range calculations. Home-range size did not significantly differ between the sexes, with an average home range of 0.42 ± 0.06 ha and core area of activity of 0.091 ± 0.074 ha. M. cervinipes did not maintain exclusive home ranges and overlapped with both other focal individuals and individuals not fitted with tracking devices. There was a relationship between the core range of M. cervinipes and individual trees of the dominant canopy species at the site. Core ranges of M. cervinipes included 2 (1.96 ± 0.27) individual canopy trees independent of the area of that core range, whereas the number of individual trees within their total range was proportional to the size of that range. This suggests that M. cervinipes sets the core of its range to include a specific level of canopy resources regardless of the size required to achieve that level, but that its overall range is merely a representative sample of trees from the site.
RNA from the 5′ end of the R2 retrotransposon controls R2 protein binding to and cleavage of its DNA target site
Authors: Christensen Shawn M. , Ye Junqiang , Eickbush Thomas H.
Published: November 2006

Non-LTR retrotransposons insert into eukaryotic genomes by target-primed reverse transcription (TPRT), a process in which cleaved DNA targets are used to prime reverse transcription of the element's RNA transcript. Many of the steps in the integration pathway of these elements can be characterized
in vitro
for the R2 element because of the rigid sequence specificity of R2 for both its DNA target and its RNA template. R2 retrotransposition involves identical subunits of the R2 protein bound to different DNA sequences upstream and downstream of the insertion site. The key determinant regulating which DNA-binding conformation the protein adopts was found to be a 320-nt RNA sequence from near the 5′ end of the R2 element. In the absence of this 5′ RNA the R2 protein binds DNA sequences upstream of the insertion site, cleaves the first DNA strand, and conducts TPRT when RNA containing the 3′ untranslated region of the R2 transcript is present. In the presence of the 320-nt 5′ RNA, the R2 protein binds DNA sequences downstream of the insertion site. Cleavage of the second DNA strand by the downstream subunit does not appear to occur until after the 5′ RNA is removed from this subunit. We postulate that the removal of the 5′ RNA normally occurs during reverse transcription, and thus provides a critical temporal link to first- and second-strand DNA cleavage in the R2 retrotransposition reaction.
Mitochondria-associated Yeast mRNAs and the Biogenesis of Molecular Complexes
Authors: Garcia M. , Darzacq X. , Delaveau T. , Jourdren L. , Singer R. H. , Jacq C.
Published: November 2006

The coherence of mitochondrial biogenesis relies on spatiotemporally coordinated associations of 800–1000 proteins mostly encoded in the nuclear genome. We report the development of new quantitative analyses to assess the role of local protein translation in the construction of molecular complexes. We used real-time PCR to determine the cellular location of 112 mRNAs involved in seven mitochondrial complexes. Five typical cases were examined by an improved FISH protocol. The proteins produced in the vicinity of mitochondria (MLR proteins) were, almost exclusively, of prokaryotic origin and are key elements of the core construction of the molecular complexes; the accessory proteins were translated on free cytoplasmic polysomes. These two classes of proteins correspond, at least as far as intermembrane space (IMS) proteins are concerned, to two different import pathways. Import of MLR proteins involves both TOM and TIM23 complexes whereas non-MLR proteins only interact with the TOM complex. Site-specific translation loci, both outside and inside mitochondria, may coordinate the construction of molecular complexes composed of both nuclearly and mitochondrially encoded subunits.
Interpretation of ANOVA models for microarray data using PCA
Authors: de Haan J. R. , Wehrens R. , Bauerschmidt S. , Piek E. , Schaik R. C. van , Buydens L. M. C.
Published: November 2006

Motivation: ANOVA is a technique, which is frequently used in the analysis of microarray data, e.g. to assess the significance of treatment effects, and to select interesting genes based on P-values. However, it does not give information about what exactly is causing the effect. Our purpose is to improve the interpretation of the results from ANOVA on large microarray datasets, by applying PCA on the individual variance components. Interaction effects can be visualized by biplots, showing genes and variables in one plot, providing insight in the effect of e.g. treatment or time on gene expression. Because ANOVA has removed uninteresting sources of variance, the results are much more interpretable than without ANOVA. Moreover, the combination of ANOVA and PCA provides a simple way to select genes, based on the interactions of interest.

Results: It is shown that the components from an ANOVA model can be summarized and visualized with PCA, which improves the interpretability of the models. The method is applied to a real time-course gene expression dataset of mesenchymal stem cells. The dataset was designed to investigate the effect of different treatments on osteogenesis. The biplots generated with the algorithm give specific information about the effects of specific treatments on genes over time. These results are in agreement with the literature. The biological validation with GO annotation from the genes present in the selections shows that biologically relevant groups of genes are selected.

Availability: R code with the implementation of the method for this dataset is available from under the heading “Software”.

Contact:  L.Buydens@science.ru.nl
Carcinogenesis and transcriptional regulation through Maf recognition elements
Authors: Motohashi Hozumi , Yamamoto Masayuki
Published: November 2006

Many studies on carcinogenesis carried out early in the last century are united on the consensus that cancer is a genetic disease. Cancer cells typically display gene dysfunction and endogenous or exogenous insults resulting in gene dysfunction are often carcinogenic. Recent advances in stem cell biology added the new concept that cancer originates from a single cancer‐initiating cell. To understand the molecular basis of carcinogenesis from the beginning to the full acquirement of malignancy, factors concerned with carcinogenesis were categorized into three groups: those guarding and stabilizing genomes, those regulating cell proliferation, and those conferring resistance to various micro‐environmental stresses. One example of particular interest is the Keap1‐Nrf2 system since, according to recent studies, it has turned out to be ambivalent. Nrf2 heterodimerizes with small Maf protein to strongly activate transcription through the Maf recognition element (MARE) and Keap1 is an inhibitory regulator of Nrf2. The genes regulated by Nrf2 are very important for cellular protection of the genome from xenobiotic and oxidative stresses and, consequently, for preventing carcinogenesis. This implies that enhancing Nrf2 activity is a promising method for thwarting cancer. On the contrary, the constitutive activation of Nrf2 due to mutations in the keap1 gene is characteristically observed in lung cancer cells, suggesting that induced expression of Nrf2 target genes favors the prevalence of cancer cells. (Cancer Sci 2007; 98: 135–139)