bluuebunny/crossref_metadata_2025 huggingface dataset:
Heme Oxygenase–1 and Its Reaction Product, Carbon Monoxide, Prevent Inflammation–Related Apoptotic Liver Damage in Mice
Authors: Sass Gabriele , Soares Miguel Che Parreira , Yamashita Kenichiro , Seyfried Stefan , Zimmermann Wolfram-Hubertus , Eschenhagen Thomas , Kaczmarek Elzbieta , Ritter Thomas , Volk Hans-Dieter , Tiegs Gisa
Published: March 2007

Heme oxygenase–1 (HO–1), a stress–responsive enzyme that catabolizes heme into carbon monoxide (CO), biliverdin, and iron, has previously been shown to protect grafts from ischemia/reperfusion injury and rejection. Here we investigated the protective potential of HO–1 in 5 models of immune–mediated liver injury. We found that up–regulation of endogenous HO–1 by cobalt–protoporphyrin–IX (CoPP) protected mice from apoptotic liver damage induced by anti–CD95 antibody (Ab) or D–galactosamine in combination with either anti–CD3 Ab, lipopolysaccharide (LPS), or tumor necrosis factor α (TNF–α). HO–1 induction prevented apoptotic liver injury, measured by inhibition of caspase 3 activation, although it did not protect mice from caspase–3—independent necrotic liver damage caused by concanavalin A (Con A) administration. In addition, overexpression of HO–1 by adenoviral gene transfer resulted in protection from apoptotic liver injury, whereas inhibition of HO–1 enzymatic activity by tin–protoporphyrin–IX (SnPP) abrogated the protective effect. HO–1—mediated protection seems to target parenchymal liver cells directly because CoPP treatment protected isolated primary hepatocytes from anti–CD95—induced apoptosis in vitro. Furthermore, depletion of Kupffer cells (KCs) did not interfere with the protective effect in vivo. Exogenous CO administration or treatment with the CO–releasing agent methylene chloride mimicked the protective effect of HO–1, whereas treatment with exogenous biliverdin or overexpression of ferritin by recombinant adenoviral gene transfer did not. In conclusion, HO–1 is a potent protective factor for cytokine– and CD95–mediated apoptotic liver damage. Induction of HO–1 might be of a therapeutic modality for inflammatory liver diseases. (Hepatology 2003;38:909-918).
Ontogeny, Distribution, and Possible Functional Implications of An Unusual Aquaporin, Aqp8, in Mouse Liver
Authors: Ferri Domenico , Mazzone Amelia , Liquori Giuseppa Esterina , Cassano Grazia , Svelto Maria , Calamita Giuseppe
Published: March 2007

Aquaporins are channel proteins widely expressed in nature and known to facilitate the rapid movement of water across numerous cell membranes. A mammalian aquaporin, AQP8, was recently discovered and found to have a very distinct evolutionary pathway. To understand the reason for this divergence, here we define the ontogeny and exact subcellular localization of AQP8 in mouse liver, a representative organ transporting large volumes of water for secretion of bile. Northern blotting showed strong AQP8 expression between fetal day 17 and birth as well as at weaning and thereafter. Interestingly, this pattern was confirmed by immunohistochemistry and coincided both temporally and spatially with that of hepatic glycogen accumulation. As seen by reverse–transcription polymerase chain reaction (RT–PCR) and immunohistochemistry, fasting was accompanied by remarkable down–regulation of hepatic AQP8 that paralleled the expected depletion of glycogen content. The level of hepatic AQP8 returned to be considerable after refeeding. Immunoelectron microscopy confirmed AQP8 in hepatocytes where labeling was over smooth endoplasmic reticulum (SER) membranes adjacent to glycogen granules and in canalicular membranes, subapical vesicles, and some mitochondria. In conclusion, in addition to supporting a role for AQP8 in canalicular water secretion, these findings also suggest an intracellular involvement of AQP8 in preserving cytoplasmic osmolality during glycogen metabolism and in maintaining mitochondrial volume. AQP8 may have evolved separately to feature these intracellular roles as no other known aquaporin shows this specialization. (Hepatology 2003;38:947-957).
Characterization of Premature Liver Polyploidy in Dna Repair ( Ercc1 )–Deficient Mice
Authors: Chipchase Michael D. , O'Neill Mary , Melton David W.
Published: March 2007

ERCC1–XPF is the endonuclease that cuts 5′ of the damage in nucleotide excision repair (NER). Unlike other NER proteins, ERCC1–XPF is also involved in recombination and the repair of DNA interstrand cross–links. Unique among the NER gene knockouts, Ercc1 null mice are severely runted with high levels of hepatocyte polyploidy. To understand the link between DNA repair deficiency and polyploidy we have compared the premature polyploidy in Ercc1 null liver with the normal development of polyploidy in aging control mice. Polyploidy was accelerated dramatically in Ercc1 null hepatocytes, such that ploidy levels were equivalent in 3–week–old Ercc1 null and 1– to 2–year–old wild–type mouse liver. Levels of the cyclin–dependent kinase inhibitor, p21, were increased in the nuclei of Ercc1 null hepatocytes, and this increase was concentrated in, but not confined to, the polyploid hepatocytes. Much lower levels of p21 messenger RNA (mRNA) were found in old wild–type liver with equivalent levels of ploidy. We suggest that the more rapid accumulation of DNA damage in Ercc1 null liver leads to an increase in p21 levels, but that there is not a simple direct link between p21 levels and premature polyploidy. The failure to observe any link between p21 levels and polyploidy in aged wild–type liver may be attributable to the much lower levels of accumulated DNA damage, the much greater timescale involved, or the existence of a p21–independent mechanism for polyploidy. In conclusion, the premature polyploidy in Ercc1–deficient liver differs from the normal aging–related process. (Hepatology 2003;38:958-966).
Sex Is A Major Determinant of Cyp3a4 Expression in Human Liver
Authors: Wolbold Renzo , Klein Kathrin , Burk Oliver , Nüssler Andreas K. , Neuhaus Peter , Eichelbaum Michel , Schwab Matthias , Zanger Ulrich M.
Published: March 2007

Many drugs that are substrates of CYP3A4, the major human drug–metabolizing cytochrome P450 (CYP), show higher clearance in women than in men. Although this effect is believed to be related to drug metabolism, the underlying cause has not been elucidated. We investigated CYP3A4 in a large collection (n = 94) of well–characterized surgical liver samples and found 2–fold higher CYP3A4 levels in female compared with male samples (P < .0001) and a corresponding 50% increase in the CYP3A–dependent N–dealkylation of verapamil (P < .01). This expression difference was not due to preferential induction in women following higher drug exposure because it was even larger in a subgroup not previously exposed to drugs. Higher expression in women was also found for CYP3A4 messenger RNA (mRNA) transcripts, suggesting a pretranslational mechanism. Expression of the pregnane X receptor (PXR), which is crucially involved in CYP3A4 induction by xenobiotics, was strongly correlated to CYP3A4 at the mRNA level in all individuals as well as in the subgroup not exposed to drugs (r = 0.81; P < .0001), but no sex–dependent expression of PXR mRNA was found. The ABC transporter P–glycoprotein, which has been proposed to be implicated in the mechanism of sex–dependent drug clearance, was also not differentially expressed. The influence of drug treatment on expression was examined from patient drug histories, and strong induction of CYP3A4 by carbamazepine and St. John's wort was found. In conclusion, sex, in addition to PXR and drug exposure, is a major factor for CYP3A4 expression in humans, thus explaining many of the previous observations of sex–dependent drug clearance. (Hepatology 2003;38:978-988).
Synthesis of polymeric core–shell particles using surface‐initiated living free‐radical polymerization
Authors: Jhaveri Sarav B. , Koylu Damla , Maschke Dominik , Carter Kenneth R.
Published: March 2007

An easy and novel approach to the synthesis of functionalized nanostructured polymeric particles is reported. The surfactant‐free emulsion polymerization of methyl methacrylate in the presence of the crosslinking reagent 2‐ethyl‐2‐(hydroxy methyl)‐1,3‐propanediol trimethacrylate was used to in situ crosslink colloid micelles to produce stable, crosslinked polymeric particles (diameter size ∼ 100–300 nm). A functionalized methacrylate monomer, 2‐methacryloxyethyl‐2′‐bromoisobutyrate, containing a dormant atom transfer radical polymerization (ATRP) living free‐radical initiator, which is termed an inimer (initiator/monomer), was added to the solution during the polymerization to functionalize the surface of the particles with ATRP initiator groups. The surface‐initiated ATRP of different monomers was then carried out to produce core–shell‐type polymeric nanostructures. This versatile technique can be easily employed for the design of a wide variety of polymeric shells surrounding a crosslinked core while keeping good control over the sizes of the nanostructures. The particles were characterized with scanning electron microscopy, transmission electron microscopy, optical microscopy, dynamic light scattering, and Raman spectroscopy. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1575–1584, 2007
Quantitative structural characterization of GaN quantum dot ripening using reflection high-energy electron diffraction
Authors: Coraux J. , Favre-Nicolin V. , Renevier H. , Proietti M. G. , Amstatt B. , Bellet-Amalric E. , Daudin B.
Published: March 2007

Reflection high-energy electron diffraction (RHEED) was used to monitor the strain of GaN/AlN quantum dots (QDs) grown by molecular beam epitaxy. Quantitative and absolute values of the in- and out-of-plane strains of the QDs were determined and compared to reference values, obtained by x-ray diffraction measurements. A very good agreement was found between RHEED and x-ray measurements. The growth and thermal ripening of the dots were analyzed. A progressive strain relaxation was observed during the ripening stage, suggesting a morphology evolution of the dots.
Probe particles alter dynamic heterogeneities in simple supercooled systems
Authors: Zangi Ronen , Mackowiak Stephan A. , Kaufman Laura J.
Published: March 2007

The authors present results from molecular dynamics simulations on the effect of smooth and rough probes on the dynamics of a supercooled Lennard-Jones (LJ) mixture. The probe diameter was systematically varied from one to seven times the diameter of the large particles of the LJ mixture. Mean square displacements show that in the presence of a large smooth probe the supercooled liquid speeds up, while in the presence of a large rough probe, the supercooled liquid slows down. Non-Gaussian parameters indicate that with both smooth and rough probes, the heterogeneity of the supercooled system increases. From the analysis of local Debye-Waller factors, it is evident that the change in the dynamics of the LJ system is heterogeneous, with the largest perturbations close to the probes. Large smooth and rough probes appear to set up heterogeneities in these supercooled systems that would otherwise not occur, and these heterogeneities persist for long times.
The influence of the H2∕Ar ratio on surface morphology and structural defects in homoepitaxial 4H-SiC films grown with methyltrichlorosilane
Authors: Lu P. , Edgar J. H.
Published: March 2007

Characterization of surface morphology and crystal defects is reported for homoepitaxial 4H-SiC films grown at high rates (35–40μm∕h) using methyltrichlorosilane (CH3SiCl3), as single precursor. The ratio of hydrogen to argon (H2∕Ar) in the carrier gas was varied to determine the effect of hydrogen on the surface morphology and the crystalline defects. Due to hydrogen’s reaction with the graphite heater, adjusting the H2∕Ar ratio effectively changed the C∕Si ratio in the gas phase; thereby, influencing surface roughness and dislocation density. Low H2∕Ar ratios of 0.1 and 0.125 produced smooth surfaces without step bunching. Higher H2∕Ar ratios of 0.2 and 0.33 enhanced the conversion of basal plane dislocations into threading edge dislocations and reduced the density of basal plane dislocations to approximately 600cm−2. However, at these H2∕Ar ratios, macrosteps formed on the surface and the roughness increased. Micropipes from substrate dissociated into closed-core threading screw dislocations in the films grown with H2∕Ar ratio in the range of 0.1–0.2. At H2∕Ar ratio of 0.33, micropipes propagated into the film, generating hollow-core threading screw dislocations.
Magnetic phase diagram and structural separation of La0.7(Ca1−ySry)0.3MnO3 thin films
Authors: Lee Y. P. , Park S. Y. , Park J. S. , Prokhorov V. G. , Komashko V. A. , Svetchnikov V. L. , Kang J.-H.
Published: March 2007

The structural, magnetic, and transport properties of La0.7(Ca1−ySry)0.3MnO3 films, deposited on a LaAlO3 (001) single crystalline substrate by rf-magnetron sputtering using “soft” (or powder) targets, have been investigated. It was found that at 0.3≤y≤0.5 both the rhombohedral (R3¯c) and the orthorhombic (Pnma) crystal phases in the form of nanoscale clusters are coexistent at room temperature. The observed structural clustering is accompanied by two-stage magnetic and electronic transitions, and governed by a nonuniform distribution of the lattice strain through the film. It was shown that for the films with 0≤y≤0.5 the nonlinear (almost parabolic) MR(H) dependence is typical while, for 0.65≤y≤1.0, the linear MR(H) behavior is observed at room temperature. The magnetotransport properties of films are explained within the framework of field-dependent activation-energy model. The magnetic phase diagram for La0.7(Ca1−ySry)0.3MnO3 thin-film system is also presented.
Morphology of basal plane dislocations in 4H-SiC homoepitaxial layers grown by chemical vapor deposition
Authors: Zhang X. , Ha S. , Hanlumnyang Y. , Chou C. H. , Rodriguez V. , Skowronski M. , Sumakeris J. J. , Paisley M. J. , O’Loughlin M. J.
Published: March 2007

The morphology of basal plane dislocations (BPDs) in 4H-SiC homoepitaxial layers has been investigated by plan-view transmission x-ray topography and molten KOH etching. Three types of BPDs are distinguished based on their morphologies. These include interfacial dislocations, curved dislocations, and circular loop dislocations around micropipes. Their characteristics are studied in detail and possible sources of their formation during epitaxy are discussed.
Interpreting magnetization from Faraday rotation in birefringent magnetic media
Authors: Woodford S. R. , Bringer A. , Blügel S.
Published: March 2007

The Faraday effect is an extremely useful probe of magnetization dynamics on an ultrafast scale. However, the measured Faraday rotation is difficult to interpret in birefringent media. We investigate the link between magnetization and Faraday rotation by solving Maxwell’s equations in a magnetically ordered, birefringent material. We find that the Faraday rotation can depend nonlinearly on the magnetization, meaning that symmetric magnetic oscillations may lead to asymmetric Faraday measurements. Furthermore, sample alignment becomes important—if the incident light is not polarized along a birefringence axis of the sample, the Faraday rotation may be strongly enhanced or weakened, and the interpretation of the magnetization amplitude may be wrong by an order of magnitude.
Impacts of growth parameters on deep levels in n-type 4H-SiC
Authors: Danno Katsunori , Hori Tsutomu , Kimoto Tsunenobu
Published: March 2007

Deep levels in n-type 4H-SiC epilayers have been investigated by deep level transient spectroscopy. The Z1/2 and EH6/7 centers are dominant in epilayers grown with low C/Si ratios during chemical vapor deposition. By increasing the C/Si ratio, the Z1/2 and EH6/7 concentrations are decreased, while an unknown trap (the UT1 center, Ec−1.45 eV) is introduced. The Z1/2 and EH6/7 concentrations are not changed by increasing the growth rate from 14 to 23 μm/h at a fixed C/Si ratio. By increasing growth temperature from 1550 to 1750 °C, however, the Z1/2 and EH6/7 concentrations are significantly increased. From these results, the formation of Z1/2 and EH6/7 centers are mainly affected by the C/Si ratio and growth temperature rather than the growth rate. These phenomena can be explained with a model that both Z1/2 and EH6/7 centers are related to a carbon vacancy, which has been recently proposed by the authors.
Monocrystalline hexagonal-close-packed and polycrystalline face-centered-cubic Co nanowire arrays fabricated by pulse dc electrodeposition
Authors: Zhang Jun , Jones Grenville A. , Shen Tiehan H. , Donnelly Steve E. , Li Guanghai
Published: March 2007

Cobalt nanowire arrays have been grown onto anodic aluminum oxide templates by using a pulse dc electrodeposition technique. We demonstrate that the crystal structure, grain size, and related magnetic properties can be controlled by applying different pulse frequencies. For a pulse frequency of 25Hz, monocrystalline hexagonal-close-packed Co nanowires are formed with a well defined [101¯0] growth axis along the wire length. At a higher pulse frequency of 1000Hz, face-centered-cubic Co nanowires are deposited with a small grain size and a preferred [111] texture directed along the length of the wire. Possible mechanisms for the observed growth characterization are discussed. An investigation of the corresponding magnetic properties indicates that the fcc Co nanowire arrays have the larger coercivity and squareness values: reasons for this behavior are explored.
Coalescence aspects of III-nitride epitaxy
Authors: Lebedev V. , Tonisch K. , Niebelschütz F. , Cimalla V. , Cengher D. , Cimalla I. , Mauder Ch. , Hauguth S. , Ambacher O. , Morales F. M. , Lozano J. G. , González D.
Published: March 2007

In this work, coalescence aspects of wurtzite-III-nitride epitaxy are addressed. The coalescence phenomena have been studied in thin epilayers by means of electron and atomic force microscopies, and electron and x-ray diffractions. This study generalizes the growth parameters responsible for the rapid coalescence of III-nitride films, and describes the coalescence qualitatively and, partly, analytically for the case of heteroepitaxy in nonequilibrium conditions. Coalescence time and the corresponding diffusion coefficients at elevated temperatures were estimated for GaN and InN depositions. The rate of coalescence has been found to impact on the structure and morphology of III-nitride epilayers. A simple growth model was suggested to explain the formation of domain boundaries and (0001) stacking faults formed during the coalescence. In particular, it is shown that two adjacent and tilted, hexagonal-shaped 2H domains may form a noncoherent boundary explicitly along a {11¯00} plane. We also suggest that the interaction between tilted domains induces the localized lateral growth of the most epitaxially oriented domain forming a basal (0001) stacking fault followed by the formation of surface macrosteps, and consequently the termination of a threading dislocation by its dissociation and propagation under the formed (0001) stacking fault.
Improving the stability of organic light-emitting devices by using a hole-injection-tunable-anode-buffer-layer
Authors: Luo Yichun , Aziz Hany , Xu Gu , Popovic Zoran D.
Published: March 2007

Introducing a hole-injection-tunable-anode-buffer-layer (HITABL) at the indium tin oxide anode contact of an organic light-emitting device can finely tune hole injection to establish proper charge balance, thus remarkably improves its operational stability. The HITABL consists of two sublayers: (i) an ∼2.5nm thick metal (e.g., Ca, Mg, or Ag) sublayer and (ii) an ∼10nm thick tetrafluorotetracyanoquinodimethane (F4TCNQ) doped N′-di(naphthalene-1-yl)-N,N′-diphenyl-benzidine sublayer. Hole injection can be tuned by changing (i) the metal in the first sublayer and/or (ii) the concentration of the F4TCNQ dopant in the second sublayer. The choice of the metal used in the first sublayer and/or the concentration of F4TCNQ in the second sublayer affect the hole-injection efficiency. Therefore, by using the HITABL, one can make the necessary diminutive adjustments to the hole injection of a device and achieve proper charge balance, resulting in a significant improvement in operational stability.
Plasma window characterization
Authors: Krasik Ya. E. , Gleizer S. , Gurovich V. , Kronhaus I. , Hershcovitch A. , Nozar P. , Taliani C.
Published: March 2007

Parameters of an arc Ar plasma discharge used as a plasma window with a discharge current of ∼50A and a voltage of ∼58V are presented. It is shown that this arc discharge allows one to decrease the pressure at the low pressure end of the plasma window almost 380 times using relatively low pumping at the low pressure end of the plasma window. Calculations of the plasma parameters and their spatial distribution using a simple wall-stabilized arc model showed a satisfactory agreement with the experimentally obtained data. It is shown that a significant decrease in gas flow through the plasma window occurs due to the increase in plasma viscosity. An improvement of the plasma window ignition and some of its design aspects are described as well.
Electric deflection studies of rhodium clusters
Authors: Beyer Martin K. , Knickelbein Mark B.
Published: March 2007

The static electric dipole polarizabilities of rhodium clusters Rhn, n=5–28, have been measured via a molecular beam deflection method. Uniform high-field beam deflections, indicative of induced polarization, were observed for all Rhn except Rh7 and Rh10 which by contrast exhibited beam broadening and anomalously high effective polarizabilities. Analysis of the beam deflection profile of Rh7 indicates that it possesses a permanent dipole moment of 0.24±0.02D. Unlike the other clusters in the n=5–28 size range, the polarizability of Rh10 is observed to decrease with increasing source temperature. We attribute this temperature dependence to paraelectric behavior, suggesting that Rh10 is a fluxional molecule possessing a dipole moment that spatially fluctuates, uncorrelated with overall rotation.
Density functional study of the charge on Aun clusters (n=1–7) supported on a partially reduced rutile TiO2(110): Are all clusters negatively charged?
Authors: Chrétien Steeve , Metiu Horia
Published: March 2007

It is widely believed that small gold clusters supported on an oxide surface and adsorbed at the site of an oxygen vacancy are negatively charged. It has been suggested that this negative charge helps a gold cluster adsorb oxygen and weakens the O–O bond to make oxidation reactions more efficient. Given the fact that an oxygen vacancy is electron rich and that Au is a very electronegative element, the assumption that the Au cluster will take electron density from the vacancy is plausible. However, the density functional calculations presented here show that the situation is more complicated. The authors have used the Bader method to examine the charge redistribution when a Aun cluster (n=1–7) binds next to or at an oxygen vacancy on rutile TiO2(110). For the lowest energy isomers they find that Au1 and Au3 are negatively charged, Au5 and Au7 are positively charged, and Au2, Au4, and Au6 exchange practically no charge. The behavior of the Aun isomers having the second-lowest energy is also unexpected. Au2, Au3, Au5, and Au7 are negatively charged upon adsorption and very little charge is transferred when Au4 and Au6 are adsorbed. These observations can be explained in terms of the overlap between the frontier molecular orbitals of the gold cluster and the eigenstates of the support. Aun with even n becomes negatively charged when the lowest unoccupied molecular orbital has a lobe pointing in the direction of the oxygen vacancy or towards a fivefold coordinated Ti (5c-Ti) located in the surface layer; otherwise it stays neutral. Aun with odd n becomes negatively charged when the singly occupied molecular orbital has a lobe pointing in the direction of a 5c-Ti located at the vacancy site or in the surface layer, otherwise it donates electron density into the conduction band of rutile TiO2(110) becoming positively charged.
Controlled resonant tunneling in a coupled double-quantum-dot system
Authors: Shinkai Gou , Hayashi Toshiaki , Hirayama Yoshiro , Fujisawa Toshimasa
Published: March 2007

The authors investigate electrostatic coupling between two double quantum dots (DQDs) defined in an AlGaAs∕GaAs heterostructure by measuring the correlation between resonant tunneling currents through the DQDs. Resonant tunneling in one DQD can be controlled by the charge state of the other DQD. This controlled resonant tunneling is consistent with the capacitance model for the geometry and can be used to investigate the statistics of single-electron charge states in the DQD. The observed electrostatic coupling is strong enough to perform two-qubit quantum gates both for charge- and electron-spin-based qubit schemes.
Linear stability analysis of Poiseuille-Rayleigh-Bénard flows in binary fluids with Soret effect
Authors: Hu J. , Ben Hadid H. , Henry D.
Published: March 2007

Temporal and spatiotemporal instabilities of Poiseuille-Rayleigh-Bénard flows in binary fluids with Soret effect have been investigated by a Chebyshev collocation method. Both situations corresponding to the fluid layer heated from below or from above have been studied. When heating is from below and for positive separation factors, the critical thresholds strongly increase when the throughflow is applied, and the boundary curves between absolute and convective instabilities (AI∕CI) increase as well, but more steeply. For large enough positive separation factors, there exist three local minima in the neutral curves Ra(k) (Rayleigh number against wavenumber) for moderate Reynolds numbers (Re), which results in the discontinuity of the critical wavenumber curve and the nonsmoothness of the critical Rayleigh number curve when the Reynolds number is varied. For negative separation factors, there exists a contact point between the critical Rayleigh number curve and the AI∕CI boundary curve at which the fluid system is directly changed from stable to absolutely unstable without crossing the convectively unstable region. This contact point has been characterized and localized for different negative separation factors. When heating is from above, the main observation is that the stationary curve obtained at Re=0 is replaced by two critical curves, one stationary and the other oscillatory, when a throughflow is applied. An energy budget analysis for the binary fluid system is also performed. A better insight into the role played by the solutal buoyancy contribution in the different situations is thus obtained.
A mathematical model for the partition function
Authors: Guerra Ediel , Rojas Jacqueline , Mendoza Ramón
Published: March 2007

In this work we get the formula (5) that it allows the explicit computation of the renormalized partition function associated with a physical system, whose states belong to a differentiable manifold of finite dimension, and whose energy function is invariant under the action of a compact Lie group. Furthermore, we extend the formula above to the infinite dimensional case using ζ-regularization technique.
ZnS nanowires and their coaxial lateral nanowire heterostructures with BN
Authors: Chen Z. G. , Zou J. , Lu G. Q. , Liu G. , Li F. , Cheng H. M.
Published: March 2007

ZnS nanowires and their coaxial lateral BN nanowire heterostructures with a length of hundreds of micrometers and an average diameter of ∼300nm were fabricated via one-step chemical vapor deposition method. Wurtzite ZnS nanowires were coated by a shell of fluffylike hexagonal BN sheets distributed randomly. Thermogravimetric analysis indicates that the heterostructures have a much better oxidation resistance compared with ZnS nanowires. Their similar optical property suggests that the ZnS∕BN heterostructures would have potential applications in thermally and chemically rigorous environments.
Very high-mobility organic single-crystal transistors with in-crystal conduction channels
Authors: Takeya J. , Yamagishi M. , Tominari Y. , Hirahara R. , Nakazawa Y. , Nishikawa T. , Kawase T. , Shimoda T. , Ogawa S.
Published: March 2007

Very high-mobility organic transistors are fabricated with purified rubrene single crystals and high-density organosilane self-assembled monolayers. The interface with minimized surface levels allows carriers to distribute deep into the crystals by more than a few molecular layers under weak gate electric fields, so that the inner channel plays a significant part in the transfer performance. With the in-crystal carriers less affected by scattering mechanisms at the interface, the maximum transistor mobility reaches 18cm2∕Vs and the contact-free intrinsic mobility turned out to be 40cm2∕Vs as the result of four-terminal measurement. These are the highest values ever reported for organic transistors.
Effect of substrate misorientation on the InAs∕InAlAs∕InP nanostructure morphology and lateral composition modulation in the InAlAs matrix
Authors: Lei W. , Wang Y. L. , Chen Y. H. , Jin P. , Ye X. L. , Xu B. , Wang Z. G.
Published: March 2007

The authors report the self-organized growth of InAs∕InAlAs quantum wires on nominal (001) InP substrate and (001) InP substrates misoriented by 2°, 4°, and 8° towards both [−110] and [110]. The influence of substrate misorientation on the structural and optical properties of these InAs∕InAlAs quantum wires is studied by transmission electron microscopy and photoluminescence measurements. Compared with that grown on nominal (001) InP substrate, the density of InAs∕InAlAs quantum wires grown on misoriented InP(001) substrates is enhanced. A strong lateral composition modulation effect take place in the InAlAs buffer layers grown on misoriented InP substrates with large off-cut angles (4° and 8°), which induces a nucleation template for the first-period InAs quantum wires and greatly improve the size distribution of InAs quantum wires. InAs∕InAlAs quantum wires grown on InP (001) substrate 8° off cut towards [−110] show the best size homogeneity and photoluminescence intensity.
Observation of strain and temperature induced changes in the band structure of thin La0.8MnO3−δ films
Authors: Tyson T. A. , Qian Q. , DeLeon M. A. , Dubourdieu C. , Fratila L. , Cai Y. Q. , Ahn K. H.
Published: March 2007

Mn K-edge resonant inelastic x-ray scattering measurements were performed on films of La0.8MnO3−δ. The measurements reveal that strain causes large shifts of the bands above the Fermi level. The Mn 3d band switches from a narrow upshifted peak at high temperature to a broad bulklike band at low temperature in ultrathin films. The strain induced switching behavior opens the possibility of tuning the transition to higher temperatures for device applications in this class of manganite materials.
Nanostructured vanadium dioxide thin films with low phase transition temperature
Authors: Chen Sihai , Ma Hong , Dai Jun , Yi Xinjian
Published: March 2007

A low phase turning temperature of 35°C has been observed in the semiconductor-to-metal transition of nanoscale vanadium dioxide (VO2) thin films. The thin films are prepared by reactive ion beam sputtering deposition and subsequent thermal annealing. Both scanning electron microscopy and transmission electron microscopy measurements show that the grain size of the fabricated VO2 thin films are several tens of nanometers. The average height of the crystallite is 20nm and the grain diameter is between 20 and 100nm. The low-temperature phase transition is accompanied by a significant change in the thin film’s infrared transmission property.
Investigation of CdZnTe crystal defects using scanning probe microscopy
Authors: Koley G. , Liu J. , Mandal Krishna C.
Published: March 2007

Surface electronic properties of Cd0.9Zn0.1Te (CZT) crystals have been characterized using scanning spreading resistance microscopy (SSRM) and correlated with IR transmittance maps. SSRM performed on CZT samples showed excellent correlation with Te precipitates determined from infrared images. The average probe current was observed to be more than two orders of magnitude higher for the sample with higher Te precipitates. Stationary probe current-voltage relationship was found to be exponential and was modeled based on thermionic emission theory. Based on this model, the surface barriers of the CZT samples were found to be significantly different, which was confirmed independently from Kelvin probe measurements.
Nonlinear and bistable behavior of an ultrahigh-Q GaAs photonic crystal nanocavity
Authors: Weidner Evelin , Combrié Sylvain , de Rossi Alfredo , Tran Nguyen-Vi-Quynh , Cassette Simone
Published: March 2007

The authors investigate the nonlinear and bistable behavior of a high-Q GaAs photonic crystal heterostructure nanocavity, side coupled to a line-defect slab waveguide. The observations agree well with a model incorporating the relevant nonlinearities. The power threshold for bistable behavior is at least one order of magnitude lower than what is reported so far.
Effect of transparent film desiccant on the lifetime of top-emitting active matrix organic light emitting diodes
Authors: Lee Byoung Duk , Cho Yoon-Hyung , Kim Won-Jong , Oh Min Ho , Lee Jong Hyuk , Zang Dong Sik
Published: March 2007

The effects of a transparent film desiccant on the lifetime of top-emitting active matrix organic light emitting diodes (AMOLEDs) were investigated. The transparent film desiccants were prepared by mixing solutions dispersed with calcium oxide powders and ultraviolet-curable resins. As the solid content in the solutions increased from 15to30wt%, the average particle size increased from 107to240nm, whereas the transmittance of the films decreased from 98% to 80% in the visible range. The devices encapsulated with the transparent film desiccants which contained 20wt% CaO exhibited no dark spots and 97% of the initial luminance, even after being stored for over 500h at 70°C and 90% relative humidity. Also, the operational lifetime of these devices was 1850h, ten times longer than that of a device without desiccant. These results confirmed that the transparent film desiccants, which absorbed the moisture that penetrated into the devices, could be applied to the encapsulation of top-emitting AMOLEDs.
Use of quantum-point-contact high-electron-mobility-transistors for time domain multiplexing of large arrays of high impedance low temperature bolometers
Authors: Yates S. J. C. , Benoit A. , Grémion E. , Ulysse Ch. , Camus Ph. , Cavanna A. , Durand T. , Etienne B. , Gennser U. , Hoffmann C. , Leclercq S. , Jin Y.
Published: March 2007

The use of a multiplexing readout for an array of bolometers simplifies the electronics and wiring, so making the readout of large arrays of bolometers (>100) feasible. Here we describe a time domain multiplexing technique and its performance based on the use of quantum-point-contact high-electron-mobility-transistors as low temperature (to ∼100 mK) switches for measuring high impedance (5…70 MΩ) resistances and sensors. The presented system is well matched to ground based millimetric astronomy demands.
Phase relations in the Ba–Y–Cu–O films on SrTiO3 for the ex situ BaF2 process
Authors: Wong-Ng W. , Levin I. , Otani M. , Vaudin M. D. , Cook L. P. , Cline J. , Feenstra R. , Holesinger T.
Published: March 2007

In situ x-ray diffraction was used to establish the phase relations in high-Tc superconductor Ba–Y–Cu–O films grown on SrTiO3 through the ex situ BaF2 process. These relations differ from bulk equilibrium phase assemblages in the BaO–Y2O3–CuOx system. In particular, BaY2CuO5 (the “green phase”), a common impurity phase in bulk processing, is absent in the films. Because of the absence of this green phase, the compositional stability field of Ba2YCu3O6+x expands considerably as compared to that of the bulk system, resulting in the tie lines Ba2YCu3O6+x–Y2O3 and Ba2YCu3O6+x–Y2Cu2O5.
Rapid evolution of smell and taste receptor genes during host specialization in
Drosophila sechellia
Authors: McBride Carolyn S.
Published: March 2007

Our understanding of the genetic basis of host specialization in insects is limited to basic information on the number and location of genetic factors underlying changes in conspicuous phenotypes. We know nothing about general patterns of molecular evolution that may accompany host specialization but are not traceable to a single prominent phenotypic change. Here, I describe changes in the entire repertoire of 136 olfactory receptor (
Or
) and gustatory receptor (
Gr
) genes of the recently specialized vinegar fly
Drosophila sechellia
. I find that
D. sechellia
is losing
Or
and
Gr
genes nearly 10 times faster than its generalist sibling
Drosophila simulans
. Moreover, those
D. sechellia
receptors that remain intact have fixed amino acid replacement mutations at a higher rate relative to silent mutations than have their
D. simulans
orthologs. Comparison of these patterns with those observed in a random sample of genes indicates that the changes at
Or
and
Gr
loci are likely to reflect positive selection and/or relaxed constraint associated with the altered ecological niche of this fly.
S
-adenosylmethionine directly inhibits binding of 30S ribosomal subunits to the S
MK
box translational riboswitch RNA
Authors: Fuchs Ryan T. , Grundy Frank J. , Henkin Tina M.
Published: March 2007

The S
MK
box is a conserved riboswitch motif found in the 5′ untranslated region of
metK
genes [encoding
S
-adenosylmethionine (SAM) synthetase] in lactic acid bacteria, including
Enterococcus, Streptococcus
, and
Lactococcus
sp. Previous studies showed that this RNA element binds SAM
in vitro
, and SAM binding causes a structural rearrangement that sequesters the Shine–Dalgarno (SD) sequence by pairing with an anti-SD (ASD) element. A model was proposed in which SAM binding inhibits
metK
translation by preventing binding of the ribosome to the SD region of the mRNA. In the current work, the addition of SAM was shown to inhibit binding of 30S ribosomal subunits to S
MK
box RNA; in contrast, the addition of
S
-adenosylhomocysteine (SAH) had no effect. A mutant RNA, which has a disrupted SD-ASD pairing, was defective in SAM binding and showed no reduction of ribosome binding in the presence of SAM, whereas a compensatory mutation that restored SD-ASD pairing restored the response to SAM. Primer extension inhibition assays provided further evidence for SD-ASD pairing in the presence of SAM. These results strongly support the model that S
MK
box translational repression operates through occlusion of the ribosome binding site and that SAM binding requires the SD-ASD pairing.
Prefrontal/accumbal catecholamine system determines motivational salience attribution to both reward- and aversion-related stimuli
Authors: Ventura Rossella , Morrone Cristina , Puglisi-Allegra Stefano
Published: March 2007

Recent evidence suggests that rewarding and aversive stimuli affect the same brain areas, including medial prefrontal cortex and nucleus accumbens. Although nucleus accumbens is known to respond to salient stimuli, regardless of their hedonic valence, with selective increased dopamine release, little is known about the role of prefrontal cortex in reward- and aversion-related motivation or about the neurotransmitters involved. Here we find that selective norepinephrine depletion in medial prefrontal cortex of mice abolished the increase in the release of norepinephrine by prefrontal cortex and of dopamine by nucleus accumbens that is induced by food, cocaine, or lithium chloride and impaired the place conditioning induced by both lithium chloride (aversion) and food or cocaine (preference). This is evidence that prefrontal cortical norepinephrine transmission is necessary for motivational salience attribution to both reward- and aversion-related stimuli through modulation of dopamine in nucleus accumbens, a brain area involved in all motivated behaviors.
First-spike latency information in single neurons increases when referenced to population onset
Authors: Chase Steven M. , Young Eric D.
Published: March 2007

It is well known that many stimulus parameters, such as sound location in the auditory system or contrast in the visual system, can modulate the timing of the first spike in sensory neurons. Could first-spike latency be a candidate neural code? Most studies measuring first-spike latency information assume that the brain has an independent reference for stimulus onset from which to extract latency. This assumption creates an obvious confound that casts doubt on the feasibility of first-spike latency codes. If latency is measured relative to an internal reference of stimulus onset calculated from the responses of the neural population, the information conveyed by the latency of single neurons might decrease because of correlated changes in latency across the population. Here we assess the effects of a realistic model of stimulus onset detection on the first-spike latency information conveyed by single neurons in the auditory system. Contrary to expectation, we find that on average, the information contained in single neurons does not decrease; in fact, the majority of neurons show a slight increase in the information conveyed by latency referenced to a population onset. Our results show that first-spike latency codes are a feasible mechanism for information transfer even when biologically plausible estimates of stimulus onset are taken into account.
A porphomethene inhibitor of uroporphyrinogen decarboxylase causes porphyria cutanea tarda
Authors: Phillips John D. , Bergonia Hector A. , Reilly Christopher A. , Franklin Michael R. , Kushner James P.
Published: March 2007

Porphyria cutanea tarda (PCT), the most common form of porphyria in humans, is due to reduced activity of uroporphyrinogen decarboxylase (URO-D) in the liver. Previous studies have demonstrated that protein levels of URO-D do not change when catalytic activity is reduced, suggesting that an inhibitor of URO-D is generated in hepatocytes. Here, we describe the identification and characterization of an inhibitor of URO-D in liver cytosolic extracts from two murine models of PCT: wild-type mice treated with iron, δ-aminolevulinic acid, and polychlorinated biphenyls; and mice with one null allele of
Uro-d
and two null alleles of the hemochromatosis gene (
Uro-d
+/−
,
Hfe
−/−
) that develop PCT with no treatments. In both models, we identified an inhibitor of recombinant human URO-D (rhURO-D). The inhibitor was characterized by solid-phase extraction, chromatography, UV-visible spectroscopy, and mass spectroscopy and proved to be uroporphomethene, a compound in which one bridge carbon in the uroporphyrinogen macrocycle is oxidized. We synthesized uroporphomethene by photooxidation of enzymatically generated uroporphyrinogen I or III. Both uroporphomethenes inhibited rhURO-D, but the III isomer porphomethene was a more potent inhibitor. Finally, we detected an inhibitor of rhURO-D in cytosolic extracts of liver biopsy samples of patients with PCT. These studies define the mechanism underlying clinical expression of the PCT phenotype, namely oxidation of uroporphyrinogen to uroporphomethene, a competitive inhibitor of URO-D. The oxidation reaction is iron-dependent.
Acupuncture Treatment of Dysmenorrhea Resistant to Conventional Medical Treatment
Authors: Iorno V. , Burani R. , Bianchini B. , Minelli E. , Martinelli F. , Ciatto S.
Published: March 2007

We evaluated the effect of acupuncture on NSAID resistant dysmenorrhea related pain [measured according to Visual Analogue Scale (VAS)] in 15 consecutive patients. Pain was measured at baseline (T1), mid treatment (T2), end of treatment (T3) and 3 (T4) and 6 months (T5) after the end of treatment. Substantial reduction of pain and NSAID assumption was observed in 13 of 15 patients (87%). Pain intensity was significantly reduced with respect to baseline (average VAS = 8.5), by 64, 72, 60 or 53% at T2, T3, T4 or T5. Greater reduction of pain was observed for primary as compared with secondary dysmenorrhea. Average pain duration at baseline (2.6 days) was significantly reduced by 62, 69, 54 or 54% at T2, T3, T4 or T5. Average NSAID use was significantly reduced by 63, 74, 58 or 58% at T2, T3, T4 or T5, respectively, and ceased totally in 7 patients, still asymptomatic 6 months after treatment. Our findings suggest that acupuncture may be indicated to treat dysmenorrhea related pain, in particular in those subjects in whom NSAID or oral contraceptives are contraindicated or refused.
Recent human effective population size estimated from linkage disequilibrium
Authors: Tenesa Albert , Navarro Pau , Hayes Ben J. , Duffy David L. , Clarke Geraldine M. , Goddard Mike E. , Visscher Peter M.
Published: March 2007

Effective population size (Ne) determines the amount of genetic variation, genetic drift, and linkage disequilibrium (LD) in populations. Here, we present the first genome-wide estimates of human effective population size from LD data. Chromosome-specific effective population size was estimated for all autosomes and the X chromosome from estimated LD between SNP pairs <100 kb apart. We account for variation in recombination rate by using coalescent-based estimates of fine-scale recombination rate from one sample and correlating these with LD in an independent sample. Phase I of the HapMap project produced between 18 and 22 million SNP pairs in samples from four populations: Yoruba from Ibadan (YRI), Nigeria; Japanese from Tokyo (JPT); Han Chinese from Beijing (HCB); and residents from Utah with ancestry from northern and western Europe (CEU). For CEU, JPT, and HCB, the estimate of effective population size, adjusted for SNP ascertainment bias, was ∼3100, whereas the estimate for the YRI was ∼7500, consistent with the out-of-Africa theory of ancestral human population expansion and concurrent bottlenecks. We show that the decay in LD over distance between SNPs is consistent with recent population growth. The estimates of Ne are lower than previously published estimates based on heterozygosity, possibly because they represent one or more bottlenecks in human population size that occurred ∼10,000 to 200,000 years ago.
Genome-wide identification of spliced introns using a tiling microarray
Authors: Zhang Zhihong , Hesselberth Jay R. , Fields Stanley
Published: March 2007

The prediction of gene models from genome sequence remains an unsolved problem. One hallmark of eukaryotic gene structure is the presence of introns, which are spliced out of pre-mRNAs prior to translation. The excised introns are released in the form of lariats, which must be debranched prior to their turnover. In the yeast Saccharomyces cerevisiae, the absence of the debranching enzyme causes these lariat RNAs to accumulate. This accumulation allows a comparison of tiling array signals of RNA from the debranching mutant to the wild-type parent strain, and thus the identification of lariats on a genome-wide scale. This approach identified 141 of 272 known introns, confirmed three previously predicted introns, predicted four novel introns (of which two were experimentally confirmed), and led to the reannotation of four others. In many instances, signals from the tiling array delineated the 5′ splice site and branchpoint site, confirming predicted gene structures. Nearly all introns that went undetected are present in mRNAs expressed at low levels. Overall, 97% of the significant probes could be attributed either to spliced introns or to genes up-regulated by deletion of the debranching enzyme. Because the debranching enzyme is conserved among eukaryotes, this approach could be generally applicable for the annotation of eukaryotic genes and the detection of novel and alternative splice forms.