bluuebunny/crossref_metadata_2025 huggingface dataset:
Autonomous Movement of Silica and Glass Micro‐Objects Based on a Catalytic Molecular Propulsion System
Authors: Stock Christoph , Heureux Nicolas , Browne Wesley R. , Feringa Ben L.
Published: February 2008

A general approach for the easy functionalization of bare silica and glass surfaces with a synthetic manganese catalyst is reported. Decomposition of H2O2 by this dinuclear metallic center into H2O and O2 induced autonomous movement of silica microparticles and glass micro‐sized fibers. Although several mechanisms have been proposed to rationalise movement of particles driven by H2O2 decomposition to O2 and water (recoil from O2 bubbles,36, 45 interfacial tension gradient37–42), it is apparent in the present system that ballistic movement is due to the growth of O2 bubbles.
Muscle bioenergetics of speeding fish: In vivo 31P‐NMR studies in a 4.7 T MR scanner with an integrated swim tunnel
Authors: Bock Christian , Lurman Glenn J. , Wittig Rolf‐M. , Webber Dale M. , Pörtner Hans‐O.
Published: February 2008

Energetic studies on exercising animals are usually limited to oxygen consumption measurements in respirometers followed by invasive tissue sampling and analysis of metabolites. Noninvasive studies of exercising animals like through the use of 31P NMR are typically restricted to “stop and go” measurements. Furthermore, magnetic resonance studies of marine animals are hampered by sea water, a highly electric conductive and dielectric medium, resulting in heavy loading and strong RF loss. In this work, we present a set‐up for online determination of muscle bioenergetics in swimming marine fish, Atlantic cod (Gadus morhua), using in vivo 31P NMR spectroscopy, which overcome these limitations. Special hardware and RF coils were developed for this purpose. A birdcage resonator adapted to high loadings was used for signal excitation. An insulated inductive coil (2 cm diameter) was fixed onto the surface of the fish tail and placed opposite a watertight, passively decoupled 9 × 6 cm2 elliptic and curved surface coil for signal recordings. This arrangement led to enhanced penetration of the RF signal and an almost 10‐fold increase in S/N ratio compared to the exclusive use of the elliptic surface coil. Monitoring of tail beat allowed to set trigger values resulted in an improved quality of in vivo 31P NMR spectra of swimming fish. We report the first successful NMR experiments recording simultaneously tissue energetic and acid–base parameters on swimming cod depending on tail beat frequency and amplitude to determine critical swimming speeds. © 2008 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 33B: 62–73, 2008
Numerical studies of the influence of textural gradients on the local stress concentrations around fibers in carbon/carbon composites
Authors: Piat Romana , Tsukrov Igor , Böhlke Thomas , Bronzel Norbert , Shrinivasa Tilottama , Reznik Boris , Gerthsen Dagmar
Published: February 2008

Carbon/carbon composites produced by chemical vapor infiltration consist of carbon fibers embedded in a matrix of pyrolytic carbon with anisotropic mechanical properties. The matrix around fibers consists of cylindrically shaped pyrolytic carbon layers of coating, which may have different textures with different mechanical properties in the axial, radial and circumferential directions. The goal of the present numerical study is to investigate the influence of the coating microstructure on stress concentrations and possible modes of failure in the carbon composite.

Numerical modeling was performed on two length scales. First, the material properties of the differently textured pyrolytic carbon layers were determined on the nanometer scale using methodology based on the Eshelby theory for continuously distributed inclusions. Then, the obtained material parameters for each layer were used as input for the finite element models on the micrometer scale. The numerical simulations were conducted for three basic loading scenarios: uniaxial tension, shear loading and hydrostatic compression. The calculated stress distributions show zones of maximum stress concentrations and provide information on the possible failure regions for each material under all considered loading cases. The numerical results demonstrate good correspondence with experimentally identified failure regions. Copyright © 2008 John Wiley & Sons, Ltd.
Subharmonic injection‐locking and self‐oscillating mixing
Authors: Plessas F. , Papalambrou A. , Kalivas G.
Published: February 2008

Subharmonic injection‐locking and self‐oscillating mixing functions of a modified Colpitts oscillator operating at 1 GHz are reported. The injection‐locking circuit, using a GaAs FET, is described theoretically and experimentally. Phase noise, power consumption and conversion gain measurements indicate that the proposed design is attractive for low‐cost, low‐power consumption front‐ends. Copyright © 2008 John Wiley & Sons, Ltd.
Cytochrome P450 2E1 contributes to ethanol-induced fatty liver in mice
Authors: Lu Yongke , Zhuge Jian , Wang Xiaodong , Bai Jingxiang , Cederbaum Arthur I.
Published: February 2008

Cytochrome P450 2E1 (CYP2E1) is suggested to play a role in alcoholic liver disease, which includes alcoholic fatty liver, alcoholic hepatitis, and alcoholic cirrhosis. In this study, we investigated whether CYP2E1 plays a role in experimental alcoholic fatty liver in an oral ethanol-feeding model. After 4 weeks of ethanol feeding, macrovesicular fat accumulation and accumulation of triglyceride in liver were observed in wild-type mice but not in CYP2E1-knockout mice. In contrast, free fatty acids (FFAs) were increased in CYP2E1-knockout mice but not in wild-type mice. CYP2E1 was induced by ethanol in wild-type mice, and oxidative stress induced by ethanol was higher in wild-type mice than in CYP2E1-knockout mice. Peroxisome proliferator-activated receptor α (PPARα), a regulator of fatty acid oxidation, was up-regulated in CYP2E1-knockout mice fed ethanol but not in wild-type mice. A PPARα target gene, acyl CoA oxidase, was decreased by ethanol in wild-type but not in CYP2E1-knockout mice. Chlormethiazole, an inhibitor of CYP2E1, lowered macrovesicular fat accumulation, inhibited oxidative stress, and up-regulated PPARα protein level in wild-type mice fed ethanol. The introduction of CYP2E1 to CYP2E1-knockout mice via an adenovirus restored macrovesicular fat accumulation. These results indicate that CYP2E1 contributes to experimental alcoholic fatty liver in this model and suggest that CYP2E1-derived oxidative stress may inhibit oxidation of fatty acids by preventing up-regulation of PPARα by ethanol, resulting in fatty liver.
Lymphoid neogenesis and immune infiltration in aged liver
Authors: Singh Pallavi , Coskun Zeynep Z. , Goode Catriona , Dean Adam , Thompson-Snipes LuAnn , Darlington Gretchen
Published: February 2008

Immune dysregulation and inflammation play a major role in the pathology of age-related disorders. In an earlier study, the microarray data from our laboratory indicated an increase in inflammation-related gene expression in the liver with age. We further investigated immune-related changes in the aged liver and found that the levels of inflammatory cytokines, chemokines, and inflammatory genes were higher in aged animals. Immunohistochemical studies showed that immune cells formed clusters or foci in the livers of old mice, preferentially near the perivascular regions. Further analysis revealed an enrichment of macrophages, T cells, B cells, natural killer cells, and neutrophils in old liver. Characterization of the immune clusters showed the presence of shared markers of tertiary lymphoid neogenesis. Levels of lymph node homing cytokines were elevated. Expression of immunoglobulin and recombinase gene transcripts was also higher, indicating the presence of ectopic lymphoid structures in the aged liver.

Conclusion:

Aged liver exhibits a marked inflammatory status accompanied by increased immune cell infiltration. Inflammation and ectopic lymphoid structures have previously been shown to be associated with carcinogenesis, a condition that becomes more prevalent with age. Thus, further study of inflammation-related changes in the microenvironment of the aged liver could provide insights into these disorders.
Mesenchymal stem cell–derived molecules directly modulate hepatocellular death and regeneration in vitro and in vivo
Authors: van Poll Daan , Parekkadan Biju , Cho Cheul H. , Berthiaume François , Nahmias Yaakov , Tilles Arno W. , Yarmush Martin L.
Published: February 2008

Orthotopic liver transplantation is the only proven effective treatment for fulminant hepatic failure (FHF), but its use is limited because of organ donor shortage, associated high costs, and the requirement for lifelong immunosuppression. FHF is usually accompanied by massive hepatocellular death with compensatory liver regeneration that fails to meet the cellular losses. Therefore, therapy aimed at inhibiting cell death and stimulating endogenous repair pathways could offer major benefits in the treatment of FHF. Recent studies have demonstrated that mesenchymal stem cell (MSC) therapy can prevent parenchymal cell loss and promote tissue repair in models of myocardial infarction, acute kidney failure, and stroke through the action of trophic secreted molecules. In this study, we investigated whether MSC therapy can protect the acutely injured liver and stimulate regeneration. In a D-galactosamine–induced rat model of acute liver injury, we show that systemic infusion of MSC-conditioned medium (MSC-CM) provides a significant survival benefit and prevents the release of liver injury biomarkers. Furthermore, MSC-CM therapy resulted in a 90% reduction of apoptotic hepatocellular death and a three-fold increment in the number of proliferating hepatocytes. This was accompanied by a dramatic increase in the expression levels of 10 genes known to be up-regulated during hepatocyte replication. Direct antiapoptotic and promitotic effects of MSC-CM on hepatocytes were demonstrated using

in vitro

assays.

Conclusion:

These data provide the first clear evidence that MSC-CM therapy provides trophic support to the injured liver by inhibiting hepatocellular death and stimulating regeneration, potentially creating new avenues for the treatment of FHF.
Acellular matrices derived from differentiating embryonic stem cells
Authors: Nair Rekha , Shukla Shreya , McDevitt Todd C.
Published: February 2008

Embryonic stem cells (ESCs) can differentiate into all somatic cell types, thereby providing a robust cell source for regenerative medicine therapies. ESCs are commonly induced to differentiate via three‐dimensional cell aggregates called embryoid bodies (EBs), which recapitulate cellular and molecular aspects of early tissue morphogenesis. Recent studies suggest that biomolecules synthesized by transplanted ESCs may provide instructive cues for tissue regeneration in vivo. Thus, the objective of this study was to acellularize EBs at different stages of differentiation in order to extract extracellular matrices containing ESC‐derived biomolecules. Successive treatment with Triton X‐100 and DNase significantly reduced the cellularity and completely inhibited the viability of EBs at various stages of differentiation. In addition, most DNA content (69–75%) was removed, while a portion of the original protein content (15–25%) was retained. Most importantly, extracellular matrix components produced by EBs were retained after acellularization. These results indicate that successful acellularization of EBs can be performed at various stages of differentiation to enable temporal modulation of acellular ECM composition. In addition, acellular matrices derived from EBs represent a novel route of obtaining molecular cues produced by ESCs actively undergoing morphogenesis, thus this technology may be relevant to the development of future regenerative medicine therapies. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Preparation and antioxidant activity of wheat gluten hydrolysates (WGHs) using ultrafiltration membranes
Authors: Kong Xiangzhen , Zhou Huiming , Hua Yufei
Published: February 2008

BACKGROUD: Many hydrolysates from animal and plant proteins have been found to possess physiological activities. Wheat gluten, an important by‐product of the wheat starch industry, is produced worldwide in enormous quantities. In this study, wheat gluten hydrolysates (WGHs) were obtained by enzymatic hydrolysis and fractionated using ultrafiltration membranes. The antioxidant activities of the hydrolysates were investigated by various antioxidant assays, including the ability to inhibit the autoxidation of linoleic acid and the scavenging effect on free radicals. Amino acid composition and molecular weight distribution were also evaluated to determine their relationship with antioxidant activity.

RESULTS: The pepsin hydrolysate (PeWGH) had the highest activity and was ultrafiltrated into three major types, PeWGH I (5–10 kDa), PeWGH II (3–5 kDa) and PeWGH III (<3 kDa). PeWGH III showed stronger inhibition of the autoxidation of linoleic acid and higher scavenging activity against 2,2‐diphenyl‐1‐picrylhydrazyl, superoxide and hydroxyl free radicals. Furthermore, PeWGH III had the highest total hydrophobic amino acid content (45.11 g per 100 g protein), and its molecular weight distribution ranged from 1700 to 100 Da.

CONCLUSION: The low molecular weight and amino acid composition of PeWGHs were found to be strongly correlated with their antioxidant activity. PeWGH could be used as a natural antioxidant in the pharmaceutical and food industries in the future. Copyright © 2008 Society of Chemical Industry
Cyanogenicity of cassava varieties and risk of exposure to cyanide from cassava food in Nigerian communities
Authors: Oluwole O Steven A
Published: February 2008

BACKGROUND: High‐cyanogenic cassava varieties are cultivated in many tropical communities that are free of neurological syndromes attributed to consumption of cassava foods. This study was done in four geographical areas of Nigeria (northern, southwestern, southeastern and an area endemic for ataxic polyneuropathy) to determine if cyanogenicity of cassava is associated with geographical area, altitude or level of cyanogenic compounds in gari, a popular cassava food in West Africa.

RESULTS: Mean levels of cassava cyanogens were 153, 127, 68 and 65 mg HCN equivalents (eq.) kg−1 dry weight (DW) in the endemic, southeastern, southwestern and northern areas respectively (P < 0.0001), while mean levels of gari cyanogens were 9, 4, 7 and 13 mg HCN eq. kg−1 DW in the respective areas (P < 0.0001). The mean altitude was 35 m in the endemic area, 55 m in the southeastern area, 220 m in the southwestern area and 273 m in the northern area (P < 0.0001). Altitude was associated with cyanogenicity of cassava in univariate and multivariate models (P < 0.0001). One hundred and twenty‐six (93%) farmers and 255 (77%) processors did not perceive cassava or its food products as toxic.

CONCLUSION: The findings indicate that cyanogenicity of cassava is determined by environmental factors rather than by conscious selection of varieties by farmers. Farming high‐cyanogenic cassava is not associated with high levels of residual cyanogens in gari. Cassava is not perceived as toxic by farmers and processors. Copyright © 2008 Society of Chemical Industry
Thermal stabilization of the protozoan Entamoeba histolytica alcohol dehydrogenase by a single proline substitution
Authors: Goihberg Edi , Dym Orly , Tel‐Or Shoshana , Shimon Linda , Frolow Felix , Peretz Moshe , Burstein Yigal
Published: February 2008

Analysis of the three‐dimensional structures of two closely related thermophilic and hyperthermophilic alcohol dehydrogenases (ADHs) from the respective microorganisms Entamoeba histolytica (EhADH1) and Thermoanaerobacter brockii (TbADH) suggested that a unique, strategically located proline residue (Pro275) at the center of the dimerization interface might be crucial for maintaining the thermal stability of TbADH. To assess the contribution of Pro275 to the thermal stability of the ADHs, we applied site‐directed mutagenesis to replace Asp275 of EhADH1 with Pro (D275P‐EhADH1) and conversely Pro275 of TbADH with Asp (P275D‐TbADH). The results indicate that replacing Asp275 with Pro significantly enhances the thermal stability of EhADH1 (ΔT1/2 ≤ +10°C), whereas the reverse mutation in the thermophilic TbADH (P275D‐TbADH) reduces the thermostability of the enzyme (ΔT1/2 ≤ −18.8°C). Analysis of the crystal structures of the thermostabilized mutant D275P‐EhADH1 and the thermocompromised mutant P275D‐TbADH suggest that a proline residue at position 275 thermostabilized the enzymes by reducing flexibility and by reinforcing hydrophobic interactions at the dimer–dimer interface of the tetrameric ADHs. Proteins 2008. © 2008 Wiley‐Liss, Inc.
The effect of thermal treatments on the magnetic susceptibility of Czochralski‐grown n‐Si monocrystals
Authors: Tsmots V. M. , Litovchenko P. G. , Novikov N. N. , Pavlovskyy Yu. V. , Khlyap H. M. , Luchkevych M. M. , Salan V. P. , Patsai B. D.
Published: February 2008

The nature of paramagnetic centers formed in Cz‐Si monocrystals after their high‐temperature treatment in the temperature range of 650–1100 °C and repeated high‐temperature treatment at 1150 °C are studied. The regions of increase and decrease of paramagnetic center concentration are determined by means of the measurements of magnetic susceptibility (MS). It is found that the MS changes observed experimentally are attributed to the generation of oxygen‐related clusters and dislocation loops. The amount of impurity‐structural complexes in these crystals is investigated by the XRD method. The radii and concentration of clusters and dislocation loops are determined. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
TiO2 nanostructures prepared by ferrocene/cobalt catalyst agents
Authors: Lazar A.‐M. , Chaumont D. , Lacroute Y. , Gómez M. E. , Caicedo J. C. , Zambrano G. , Sacilotti M.
Published: February 2008

We present the growth and characterization of TiO2 nanocrystals. Nanostructured growth is obtained in a low‐pressure CVD system by using an organometallic precursor Ti(OC3H7)4 as both the Ti and O source catalyzed by both ferrocene (an organometallic precursor) and cobalt metallic clusters prepared by the microwave‐assisted polyol method. Two kinds of TiO2 structures were obtained in the cobalt clusters: a) pine‐tree like (with short‐leaf structure) and b) long‐leaf structures as large as a few micrometers in size and both under 10 nm in thickness. Long‐leaf TiO2 structures were grown at cobalt grain boundaries. For the growth conditions utilized, the TiO2 structures are composed of both anatase and rutile crystallographic phases. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Processing and thin film formation of TiO2–Pt nanocomposites
Authors: Es‐Souni M. , Kartopu G. , Habouti S. , Piorra A. , Es‐Souni Mar. , Solterbeck C.‐H. , Brandies H. Fischer
Published: February 2008

Thin films of TiO2‐Pt nanocomposites containing 4 at% Pt have been processed via spin‐coating. Film characterization involved XRD, Raman as well as XPS and scanning surface potential microscopy (SSPM). After annealing at 500 °C the thin films consisted of nanocrystalline anatase and a few nm Pt nanoclusters. Annealing at 600 °C resulted in the formation of a high volume fraction of rutile, ∼70%, and a coarsening of the microstructure, including Pt nanoparticles which attained a mean particle size of up to 11 nm. These results contrasted with those of pure TiO2 films obtained at 600 °C which showed only a limited amount of rutile formation, namely 9%. Raman spectra of Pt‐containing samples exhibited a fluorescence emission, as background to the Raman features, which was attributed to photoinduced luminescence from Pt nanoparticles supported by their surface plasmon resonance. Emission intensity being much higher in 600 °C film indicated a difference between the two films in terms of the (Pt) particle size and crystallinity, in agreement with the XRD results. XPS investigations revealed different oxidation states of Pt at the surface and in the film interior. The spectra suggested a slight oxidation of Pt at the surface while mainly metallic Pt was revealed in the film interior. The morphology and distribution of the Pt nanoparticles in the films annealed at 600 °C were investigated using SSPM. Discrete Pt nanoparticles, mainly distributed in the vicinity of TiO2 grain boundaries were revealed. Nanocomposite film formation, Pt distribution and morphology are explained in terms of the limited solubility of Pt in the TiO2 lattice and its higher surface energy in comparison to that of TiO2. Both effects are believed to lead to the formation of Pt nanoparticles at the (anatase or rutile) grain boundaries. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The neurobiology of benzodiazepine receptors in panic disorder and post‐traumatic stress disorder
Authors: Ellen Steven , Olver James , Norman Trevor , Burrows Graham D.
Published: February 2008

Gamma‐aminobutyric acid (GABA) is quantitatively the most important inhibitory neurotransmitter in the central nervous system, and benzodiazepines (BZs) act via a binding site on the GABA receptor complex. The neurobiology of the GABA‐BZ receptor complex is being increasingly understood as imaging and pharmacological techniques to study the receptor complex both indirectly and directly improve. This paper outlines the evidence for BZ receptor abnormalities in panic disorder and post‐traumatic stress disorder. Copyright © 2008 John Wiley & Sons, Ltd.
Crystallographic analysis of the intact metal centres [3Fe–4S]1+/0 and [4Fe–4S]2+/1+ in a Zn2+‐containing ferredoxin
Authors: Frazão Carlos , Aragão David , Coelho Ricardo , Leal Sónia S. , Gomes Cláudio M. , Teixeira Miguel , Carrondo Maria Arménia
Published: February 2008

Detailed structural models of di‐cluster seven‐iron ferredoxins constitute a valuable resource for folding and stability studies relating the metal cofactors’ role in protein stability. The here reported, hemihedric twinned crystal structure at 2.0 Å resolution from Acidianus ambivalens ferredoxin, shows an integral 103 residues, physiologically relevant native form composed by a N‐terminal extension comprising a His/Asp Zn2+ site and the ferredoxin (βαβ)2 core, which harbours intact clusters I and II, a [3Fe–4S]1+/0 and a [4Fe–4S]2+/1+ centres. This is in contrast with the previously available ferredoxin structure from Sulfolofus tokodai, which was obtained from an artificial oxidative conversion with two [3Fe–4S]1+/0 centres and poor definition around cluster II.
Overexpression of frataxin in the mitochondria increases resistance to oxidative stress and extends lifespan in Drosophila
Authors: Runko Alexander P. , Griswold Anthony J. , Min Kyung-Tai
Published: February 2008

In Friedreich's ataxia, reduction of the mitochondria protein frataxin results in the accumulation of iron and reactive oxygen species, which leads to oxidative damage, neurodegeneration and a diminished lifespan. Recent studies propose that frataxin might play a role in the antioxidative process. Here we show that overexpression of Drosophila frataxin in the mitochondria of female transgenic animals increases antioxidant capability, resistance to oxidative stress insults, and longevity. This suggests that Drosophila frataxin may function to protect the mitochondria from oxidative stresses and the ensuing cellular damage.
Structural features of protein folding nuclei
Authors: Garbuzynskiy S.O. , Kondratova M.S.
Published: February 2008

A crucial event of protein folding is the formation of a folding nucleus. We demonstrate the presence of a considerable coincidence between the location of folding nuclei and the location of so‐called “root structural motifs”, which have unique overall folds and handedness. In the case of proteins with a single root structural motif, the involvement in the formation of a folding nucleus is in average significantly higher for amino acids residues that are in root structural motifs, compared to residues in other parts of the protein. The tests carried out revealed that the observed difference is statistically reliable. Thus, a structural feature that corresponds to the protein folding nucleus is now found.
Human CyP33 binds specifically to mRNA and binding stimulates PPIase activity of hCyP33
Authors: Wang Ying , Han Ruifang , Zhang Wanqi , Yuan Yunfeng , Zhang Xiaobin , Long Yi , Mi Huaifeng
Published: February 2008

Human nuclear cyclophilin 33 (hCyP33) was the first protein which was found to contain an RNA‐binding motif and a PPIase domain. It was not known what cellular and physiological roles are played by the RNA‐binding activity as well as the PPIase activity of hCyP33. In this paper, we investigated the binding specificity of hCyP33 to different cellular RNA using ion‐exchange chromatography and affinity adsorption. Furthermore, the influence of different cellular RNAs to the PPIase activity of hCyP33 was investigated using a protease‐coupled method. The results show that hCyP33 binds specifically to mRNA, namely poly(A)+RNA, and that binding stimulates the PPIase activity of hCyP33.
Genotypic diversity of the cotton-melon aphidAphis gossypii(Glover) in Tunisia is structured by host plants
Authors: Charaabi K. , Carletto J. , Chavigny P. , Marrakchi M. , Makni M. , Vanlerberghe-Masutti F.
Published: February 2008

The study of intraspecific variation with respect to host plant utilization in polyphagous insects is crucial for understanding evolutionary patterns of insect-plant interactions.Aphis gossypii(Glover) is a cosmopolitan and extremely polyphagous aphid species. If host plant species or families constitute selective regimes to these aphids, genetic differentiation and host associated adaptation may occur. In this study, we describe the genetic structure ofA. gossypiicollected in six localities in Tunisia on different vegetable crops, on citrus trees and onHibiscus. The aim was to determine if the aphid populations are structured in relation to the host plants and if such differentiation is consistent among localities. The genetic variability ofA. gossypiisamples was examined at eight microsatellite loci. We identified only 11 multilocus genotypes among 559 individuals. Significant deviations from Hardy-Weinberg equilibrium, linkage disequilibria and absence of recombinant genotypes, confirmed thatA. gossypiireproduces by continuous apomictic parthenogenesis. Genetic differentiation between localities was not significant, whereas a strong differentiation was observed between host plant families (0.175<FST<0.691). The great majority of aphids exhibited one of three predominant multilocus genotypes that were repeatedly and respectively associated to the three plant families, Cucurbitaceae, Solanaceae and Rutaceae, demonstrating host specialization inA. gossypii. These specialized genotypes were simultaneously found with other clones onHibiscus, suggesting that this perennial host could act as a refuge plant between two vegetable crop seasons.
Additive structures in sumsets
Authors: SANDERS TOM
Published: February 2008

Suppose that A and A′ are subsets of ℤ/Nℤ. We write A+A′ for the set {a+a′:a ∈ A and a′ ∈ A′} and call it the sumset of A and A′. In this paper we address the following question. Suppose that A1,. . .,Am are subsets of ℤ/Nℤ. Does A1+· · ·+Am contain a long arithmetic progression?

The situation for m=2 is rather different from that for m ≥ 3. In the former case we provide a new proof of a result due to Green. He proved that A1+A2 contains an arithmetic progression of length roughly $\exp (c\sqrt{\alpha_1\alpha_2 \log N})$ where α1 and α2 are the respective densities of A1 and A2. In the latter case we improve the existing estimates. For example we show that if A ⊂ ℤ/Nℤ has density $\alpha \gg \sqrt{\log \log N/\log N}$ then A+A+A contains an arithmetic progression of length Ncα. This compares with the previous best of Ncα2+ϵ.

Two main ingredients have gone into the paper. The first is the observation that one can apply the iterative method to these problems using some machinery of Bourgain. The second is that we can localize a result due to Chang regarding the large spectrum of L2-functions. This localization seems to be of interest in its own right and has already found one application elsewhere.
The multifractal nature of heterogeneous sums of Dirac masses
Authors: BARRAL JULIEN , SEURET STÉPHANE
Published: February 2008

This paper investigates the natural problem of performing the multifractal analysis of heterogeneous sums of Dirac masses

where (xn)n≥0 is a sequence of points in [0, 1]d and (wn)n≥0 is a positive sequence of weights such that Σn≥0wn < ∞. We consider the case where the points xn are roughly uniformly distributed in [0, 1]d, and the weights wn depend on a random self-similar measure μ, a parameter ρ ∈ (0, 1], and a sequence of positive radii (λn)n≥1 converging to 0 in the following way

The measure ν has a rich multiscale structure. The computation of its multifractal spectrum is related to heterogeneous ubiquity properties of the system {(xn,λn)n with respect to μ.
Pacific offshore record of plinian arc volcanism in Central America: 3. Application to forearc geology
Authors: Kutterolf S. , Freundt A. , Schacht U. , Bürk D. , Harders R. , Mörz T. , Peréz W.
Published: February 2008

Sediment gravity cores collected on the Pacific slope and incoming plate offshore Central America reach up to 400 ka back in time and contain numerous ash layers from plinian eruptions at the Central American Volcanic Arc. The compositionally distinct widespread ash layers form a framework of marker horizons that allow us to stratigraphically correlate the sediment successions along and across the Middle America Trench. Moreover, ash layers correlated with 26 known eruptions on land provide absolute time lines through these successions. Having demonstrated the correlations in part 1, we here investigate implications for submarine sedimentary processes. Average accumulation rates of pelagic sediment packages constrained by bracketing tephras of known age range from ∼1–6 cm/ka on the incoming plate to 30–40 cm/ka on the continental slope. There are time intervals in which the apparent pelagic sedimentation rates significantly vary laterally both on the forearc and on the incoming plate where steady conditions are usually expected. A period of unsteadiness at 17–25 ka on the forearc coincides with a period of intense erosion on land probably triggered by tectonic processes. Unsteady conditions on the incoming plate are attributed to bend faulting across the outer rise triggering erosion and resedimentation. Extremely low apparent sedimentation rates at time intervals >50–80 ka suggest stronger tectonic activity than during younger times and indicate bend faulting is unsteady on a longer timescale. Submarine landslides are often associated with ash layers forming structurally weak zones used for detachment. Ash beds constrain ages of >60 ka, ∼19 ka, and <6 ka for three landslides offshore Nicaragua. Phases of intense fluid venting at mud mounds produce typical sediments around the mound that become covered by normal pelagic sediment during phases of weak or no activity. Using intercalated ash layers, we determine for the first time the durations (several hundred to 9000 years) of highly active periods in the multistage growth history of mud mounds offshore Central America, which is essential to understand general mud‐mound dynamics.
Trivariate statistical analysis of extreme rainfall events via the Plackett family of copulas
Authors: Kao Shih‐Chieh , Govindaraju Rao S.
Published: February 2008

Recent hydrologic studies on multivariate stochastic analysis have indicated that copulas perform well for bivariate problems. In particular, the Frank family of Archimedean copulas has been a popular choice for a dependence model. However, there are limitations to extending such Archimedean copulas to trivariate and higher dimensions, with very specific restrictions on the kinds of dependencies that can be modeled. In this study, we examine a non‐Archimedean copula from the Plackett family that is founded on the theory of constant cross‐product ratio. It is shown that the Plackett family not only performs well at the bivariate level, but also allows a trivariate stochastic analysis where the lower‐level dependencies between variables can be fully preserved while allowing for specificity at the trivariate level as well. The feasible range of Plackett parameters that would result in valid 3‐copulas is determined numerically. The trivariate Plackett family of copulas is then applied to the study of temporal distribution of extreme rainfall events for several stations in Indiana where the estimated parameters lie in the feasible region. On the basis of a given rainfall depth and duration, conditional expectations of rainfall features such as expected peak intensity, time to peak, and percentage cumulative rainfall at 10% cumulative time increments are evaluated. The results of this study suggest that while the constant cross‐product ratio theory was conventionally applied to discrete type random variables, it is also applicable to continuous random variables, and that it provides further flexibility for multivariate stochastic analyses of rainfall.
Evolutionary loss of the rdar morphotype in Salmonella as a result of high mutation rates during laboratory passage
Authors: Davidson Carla J , White Aaron P , Surette Michael G
Published: February 2008

Rapid evolution of microbes under laboratory conditions can lead to domestication of environmental or clinical strains. In this work, we show that domestication due to laboratory passage in rich medium is extremely rapid. Passaging of wild-type Salmonella in rich medium led to diversification of genotypes contributing to the loss of a spatial phenotype, called the rdar morphotype, within days. Gene expression analysis of the rdar regulatory network demonstrated that mutations were primarily within rpoS, indicating that the selection pressure for scavenging during stationary phase had the secondary effect of impairing this highly conserved phenotype. If stationary phase was omitted from the experiment, radiation of genotypes and loss of the rdar morphotype was also demonstrated, but due to mutations within the cellulose biosynthesis pathway and also in an unknown upstream regulator. Thus regardless of the selection pressure, rapid regulatory changes can be observed on laboratory timescales. The speed of accumulation of rpoS mutations during daily passaging could not be explained by measured fitness and mutation rates. A model of mutation accumulation suggests that to generate the observed accumulation of σ38 mutations, this locus must experience a mutation rate of approximately 10−4 mutations/gene/generation. Sequencing and gene expression of population isolates indicated that there were a wide variety of σ38 phenotypes within each population. This suggests that the rpoS locus is highly mutable by an unknown pathway, and that these mutations accumulate rapidly under common laboratory conditions.
Protein kinase and protein phosphatase expression in the central nervous system of G93A mSOD over‐expressing mice
Authors: Hu Jie Hong , Chernoff Ken , Pelech Steven , Krieger Charles
Published: February 2008

The expressions of 78 protein kinases, 24 protein phosphatases and 31 phosphoproteins were investigated by Kinetworks™ analysis in brain and spinal cord tissue of transgenic mice over‐expressing G93A mutant superoxide dismutase (mSOD), a murine model of amyotrophic lateral sclerosis (ALS). In the brains of affected mSOD mice, we observed increased expression of cAMP‐dependent protein kinase (PKA, 111% increase compared with control), and protein phosphatase 2B Aα‐catalytic subunit (calcineurin, 109% increase), and reductions in the levels of PAK3 (76% decrease) and protein phosphatase 2C Cβ‐subunit (32% decrease). Increased Ser259 phosphorylation of Raf1 (126% increase) in mSOD mice correlated with higher expression of p73 Raf1 (147% increase). There was also increased p73 Raf1 (69% increase) and Ser259 phosphorylation (45% increase) in the spinal cords of mSOD mice. While adducin underwent enhanced phosphorylation (αS724, 90% increase; γS662, 290% increase) in mSOD brain, its phosphorylation was lower in the mSOD spinal cord (αS724, 53% decrease; γS662, 46% decrease). In spinal cords of affected mSOD mice, we also observed elevated expression of casein kinase 1δ (CK1δ, 157% increase), JAK2 (84% increase), PKA (183% increase), protein kinase C (PKC) δ (123% increase), p124 PKCµ (142% increase), and RhoA kinase (221% increase), and enhanced phosphorylation of extracellular regulated kinases 1 (ERK1, T202/Y204, 90% increase), and 2 (ERK2, T185/Y187, 73% increase), p38 MAP kinase (T180/Y182, 1570% increase), and PKBα (T308, 154% increase; S473, 61% increase). There was also reduced phosphorylation of RB (S780, 45% decrease; S807/S811, 65% decrease), Src (Y418, 63% decrease) and p40 SAPK/JNKβ (T183/Y185, 43% decrease). Variability in the expression of kinases, phosphatases and phosphorylation of their substrates was observed even in mutant animals having a similar phenotype. The expression and phosphorylation differences between mSOD and control mice were dissimilar to those between ALS patients and controls. This finding indicates that the activation of protein kinases and phosphoproteins is different with neuron loss in the mSOD mouse compared with that seen in patients with the sporadic form of ALS.
Quantitative on‐line monitoring of hippocampus glucose and lactate metabolism in organotypic cultures using biosensor technology
Authors: Gramsbergen Jan Bert , Leegsma‐Vogt Gea , Venema Kor , Noraberg Jens , Korf Jakob
Published: February 2008

Quantitative glucose and lactate metabolism was assessed in continuously perfused organotypic hippocampal slices under control conditions and during exposure to glutamate and drugs that interfere with aerobic and anaerobic metabolism. On‐line detection was possible with a system based on slow perfusion rates, a half‐open (medium/air interface) tissue chamber and a flow injection analytic system equipped with biosensors for glucose and lactate. Under basal conditions about 50% of consumed glucose was converted to lactate in hippocampal slice cultures. Using medium containing lactate (5 mm) instead of glucose (5 mm) significant lactate uptake was observed, but this uptake was less than the net uptake of lactate equivalents in glucose‐containing medium. Glucose deprivation experiments suggested lactate efflux from glycogen stores. The effects of drugs compromising or stimulating energy metabolism, i.e. 2‐deoxyglucose, 3‐nitropropionic acid, α‐cyano‐4‐hydroxycinnamate, l‐glutamate, d‐asparate, ouabain and monensin, were tested in this flow system. The data show that maintaining Na+ and K+ gradients consumed much of the energy but do not support the hypothesis that l‐glutamate stimulates glycolysis in hippocampal slice cultures.
Taipoxin induces F‐actin fragmentation and enhances release of catecholamines in bovine chromaffin cells
Authors: Ñeco Patricia , Rossetto Ornella , Gil Anabel , Montecucco Cesare , Gutiérrez Luis M.
Published: February 2008

Adrenomedullary bovine chromaffin cells were used to study the uptake and cellular effects of the phospholipase type A2 (PLA2) neurotoxin taipoxin in a neuroendocrine model. This toxin entered rapidly inside cultured cells. Within 1 h, taipoxin accumulated on the plasma membrane, independently of calcium presence, and caused fragmentation of the F‐actin cytoskeleton. Toxin‐induced cell death occurred after 24 h of incubation with the appearance of toxin containing large vesicles. Secretory experiments performed in cell populations showed an increased exocytosis in taipoxin‐treated cells stimulated by depolarization or by incubation with the calcium‐ionophore A23187. Like F‐actin fragmentation, this effect is abolished by replacement of Ca2+ with Sr2+ during toxin incubation. The effect of taipoxin on exocytosis is not enhanced by latrunculin A, a F‐actin disassembling drug altering secretion. Secretory studies in single taipoxin‐treated cells using amperometry, showed an increase in the number of released vesicles without modification of the kinetic parameters of individual vesicle fusions. Taken together, these results suggest that taipoxin causes F‐actin fragmentation and enhances secretion by redistribution of vesicles among secretory pools.
Regulation of tyrosine hydroxylase promoter activity by the von Hippel–Lindau tumor suppressor protein and hypoxia‐inducible transcription factors
Authors: Schnell Phillip O. , Ignacak Monika L. , Bauer Amy L. , Striet Justin B. , Paulding Waltke R. , Czyzyk‐Krzeska Maria F.
Published: February 2008

Tyrosine hydroxylase (TH), the rate‐limiting enzyme in catecholamine biosynthesis, is induced by hypoxia in oxygen‐sensitive cells of the carotid body and pheochromocytoma‐derived PC12 cells. TH is also regulated by the von Hippel–Lindau tumor suppressor protein (pVHL). Here, we report that induction of TH gene expression involves activation of the hypoxia‐inducible transcription factors (HIFs) that interact with a specific hypoxia‐responsive element (HRE) in the proximal region of the TH promoter. We also show that some of the effects of pVHL on activity of the TH promoter are mediated through HIFs. Low levels of pVHL are associated with decreased HIFα ubiquitination, increased accumulation of HIFα proteins, increased binding of HIFs to the HRE within the TH promoter, and increased activity of a TH promoter–reporter construct. In contrast, high levels of pVHL repress HIF accumulation and inhibit its activity in hypoxic cells. These results indicate that HIFs may play an important role in regulation of TH gene expression in oxygen‐sensitive cells and also in the development of hypercatecholaminemia in pheochromocytoma tumors.
Inhibition of glutamine transport depletes glutamate and GABA neurotransmitter pools: further evidence for metabolic compartmentation
Authors: Rae Caroline , Hare Nathan , Bubb William A. , McEwan Sally R. , Bröer Angelika , McQuillan James A. , Balcar Vladimir J. , Conigrave Arthur D. , Bröer Stefan
Published: February 2008

The role of glutamine and alanine transport in the recycling of neurotransmitter glutamate was investigated in Guinea pig brain cortical tissue slices and prisms, and in cultured neuroblastoma and astrocyte cell lines. The ability of exogenous (2 mm) glutamine to displace13C label supplied as [3‐13C]pyruvate, [2‐13C]acetate,l‐[3‐13C]lactate, ord‐[1‐13C]glucose was investigated using NMR spectroscopy. Glutamine transport was inhibited in slices under quiescent or depolarising conditions using histidine, which shares most transport routes with glutamine, or 2‐(methylamino)isobutyric acid (MeAIB), a specific inhibitor of the neuronal system A. Glutamine mainly entered a large, slow turnover pool, probably located in neurons, which did not interact with the glutamate/glutamine neurotransmitter cycle. This uptake was inhibited by MeAIB. When [1‐13C]glucose was used as substrate, glutamate/glutamine cycle turnover was inhibited by histidine but not MeAIB, suggesting that neuronal system A may not play a prominent role in neurotransmitter cycling. When transport was blocked by histidine under depolarising conditions, neurotransmitter pools were depleted, showing that glutamine transport is essential for maintenance of glutamate, GABA and alanine pools. Alanine labelling and release were decreased by histidine, showing that alanine was released from neurons and returned to astrocytes. The resultant implications for metabolic compartmentation and regulation of metabolism by transport processes are discussed.
Status of the ITER neutral beam injection system (invited)
Authors: Hemsworth R. S. , Tanga A. , Antoni V.
Published: February 2008

The ITER neutral beam injectors are the first injectors to be designed to operate under conditions and constraints similar to those that will be encountered with a fusion reactor. The injectors will use a single large ion source and accelerator that will produce 40A D− 1MeV beams for pulse lengths of up to 3600s. The accelerated ion beams will be neutralized in a gas (D2) neutralizer which is subdivided into four vertical channels to reduce the gas flow into the injectors that is needed to produce optimum target for neutralization. These injectors will have to operate in a hostile radiation environment and they will become highly radioactive due to the neutron flux from ITER. The design has been modified recently to have a rectangular vacuum vessel with a removable lid that allows vertical access to, and maintenance of, the beamline components, the incorporation of an absolute all metal valve at the exit of the injector, the choice of a rf driven ion source as the reference design of ion source, and to have a high voltage deck incorporating the various auxiliary power supplies in air rather that under high pressure SF6. A major development is that it has been agreed that a Neutral Beam Test Facility (NBTF) will be set up at Padua, Italy. The NBTF will consist of two test beds: one of which will be capable of operating a complete injector at full performance. The second will be an ion source test bed, which will be used for the development and testing, to full performance, of the large negative ion source.
Optical measurement of Cs distribution in the large negative ion source
Authors: Ikeda K. , Nagaoka K. , Takeiri Y. , Fantz U. , Kaneko O. , Osakabe M. , Oka Y. , Tsumori K.
Published: February 2008

To investigate a Cs behavior, optical diagnostic tools have been installed in the large negative ion source, an arc discharge used at large helical device neutral beam injector. A large Cs sputtering is observed during beam extraction due to the backstreaming H+ ions. Distribution of Cs+ light is uniform in the case of a balanced arc discharge, but large increase of Cs+ light during beam extraction is observed in a nonuniform arc discharge. Controlling of the discharge uniformity is effective to reduce the local heat loading from the backstreaming H+ ions at the backplate of ion source.
Thermodynamics and kinetics of a Gō proteinlike heteropolymer model with two-state folding characteristics
Authors: Kallias Anna , Bachmann Michael , Janke Wolfhard
Published: February 2008

We present results of Monte Carlo computer simulations of a coarse-grained hydrophobic-polar Gō-like heteropolymer model and discuss thermodynamic properties and kinetics of an exemplified heteropolymer, exhibiting two-state folding behavior. It turns out that general, characteristic folding features of realistic proteins with a single free-energy barrier can also be observed in this simplified model, where the folding transition is primarily driven by the hydrophobic force.
Cu addition effect on soft magnetic properties in Fe–Si–B alloy system
Authors: Ohta Motoki , Yoshizawa Yoshihito
Published: February 2008

The Cu content dependence of the magnetic properties in Fe84−xCuxSi2B14 and Fe82−xCuySi4B14 alloys prepared by melt spinning has been investigated. In the alloy with x=1.35, Bs increases and Hc decreases with annealing temperature TA up to 410°C, while in the alloys with x⩽1.0, Hc markedly increases at around TA=360°C. The values of Bs and Hc obtained in the annealed alloys are Bs⩽1.80T and Hc<7A∕m. With increasing Si content, the optimum Cu content for the appearance of excellent soft magnetic properties becomes higher and the optimum annealing temperature range expands.