bluuebunny/crossref_metadata_2025 huggingface dataset:
Tephra from Ice—A Simple Method to Routinely Mount, Polish, and Quantitatively Analyze Sparse Fine Particles
Authors: Kuehn Stephen C. , Froese Duane G.
Published: January 2010

A method involving a graphite substrate has been developed for the mounting and analysis of sparse, fine particles from a liquid suspension to enable improved study of volcanic ash (tephra) and atmospheric dust preserved in glacial ice. Unpolished grains may be studied by scanning electron microscope–energy dispersive spectrometry (SEM-EDS) at full vacuum without the need for a conductive coating due to the close proximity of the underlying graphite. The same grains in the same relative positions may be subsequently examined in polished mounts by a variety of methods including SEM-EDS, electron probe microanalysis, laser ablation–inductively coupled plasma–mass spectroscopy, secondary ion mass spectrometry, and optical microscopy. Particles as small as 3–5 μm may be routinely and easily prepared for analysis as polished grains, and particles of significantly different sizes may be exposed simultaneously. The general approach also offers significant flexibility, including both single- and multiple-sample mounts, and may be adjusted to suit a variety of samples and analytical methods.
Collagen-Chondroitin Sulphate-Hydroxyapatite Porous Composites: A Histochemical and Electron Microscopy Approach
Authors: Zarnescu Otilia , Craciunescu Oana , Moldovan Lucia
Published: January 2010

In this study the structure of collagen-chondroitin sulphate-hydroxyapatite porous composites is investigated by histochemical (Von Kossa staining), immunohistochemical, and transmission electron microscopy. Examination of composites on picrosirius red stained sections showed that polarization colors of collagen were generally in the range of orange-red. Immunofluorescence data indicate that chondroitin sulphate was either chemically incorporated into the bulk structure of collagen scaffolds or attached on surfaces of collagen bundles. Depending on the ratio between collagen:chondroitin sulphate:hydroxyapatite, von Kossa histochemical staining showed a progressive loading of collagen-chondroitin sulphate bundles with hydroxyapatite. Transmission electron microscopy studies have shown that composites contain mostly collagen fibrils aggregated with random orientation with very few collagen fibers showing the 67-nm banding pattern. Hydroxyapatite deposits of various sizes occurred among the collagen fibrils.
RANKIN’S METHOD AND JACOBI FORMS OF SEVERAL VARIABLES
Authors: RAMAKRISHNAN B. , SAHU BRUNDABAN
Published: January 2010

Following R. A. Rankin’s method, D. Zagier computed the nth Rankin–Cohen bracket of a modular form g of weight k1 with the Eisenstein series of weight k2, computed the inner product of this Rankin–Cohen bracket with a cusp form f of weight k=k1+k2+2n and showed that this inner product gives, up to a constant, the special value of the Rankin–Selberg convolution of f and g. This result was generalized to Jacobi forms of degree 1 by Y. Choie and W. Kohnen. In this paper, we generalize this result to Jacobi forms defined over ℋ×ℂ(g,1).
Testing the utility of paleonutrient proxies Cd/Ca and Zn/Ca in benthic foraminifera from thermocline waters
Authors: Bryan Sean P. , Marchitto Thomas M.
Published: January 2010

Reconstruction of oceanic nutrient concentrations in the past provides information about nutrient cycling and physical circulation and the role these processes have played in past climate changes. The Cd/Ca and Zn/Ca of benthic foraminifera have been used successfully to reconstruct past deep ocean nutrient concentrations. In this study we test the ability of benthic foraminiferal Cd/Ca and Zn/Ca to detect changes in thermocline nutrient concentrations using a set of 31 multicores collected in the Florida Straits. Multicore sites span depths of 173–751 m, estimated seawater Cd concentrations of 0.02–0.42 nmol kg−1, and estimated seawater Zn concentrations of 0.3–3.1 nmol kg−1. Cd/Ca in several taxa of benthic foraminifera captures the regional differences and general shape of the nutricline on either side of the Florida Straits, indicating that it is capable of resolving small changes in upper ocean nutrient concentrations in the past. We estimate that the upper ocean partition coefficient for calcitic Cd/Ca may be slightly higher than the established value. Low seawater Zn concentrations combined with low partition coefficients and slight laboratory contamination severely complicated the evaluation of benthic foraminiferal Zn/Ca. However, at least one species, C. pachyderma, incorporates Zn with a relatively high partition coefficient (∼22), minimizing these complications. C. pachyderma Zn/Ca reflects the regional differences and general shape of the nutricline on either side of the Florida Straits and demonstrates potential for thermocline paleoceanography.
Aerosol climate feedback due to decadal increases in Southern Hemisphere wind speeds
Authors: Korhonen Hannele , Carslaw Kenneth S. , Forster Piers M. , Mikkonen Santtu , Gordon Neil D. , Kokkola Harri
Published: January 2010

Observations indicate that the westerly jet in the Southern Hemisphere troposphere is accelerating. Using a global aerosol model we estimate that the increase in wind speed of 0.45 ± 0.2 m s−1decade−1 at 50–65°S since the early 1980s caused a higher sea spray flux, resulting in an increase of cloud condensation nucleus concentrations of more than 85% in some regions, and of 22% on average between 50 and 65°S. These fractional increases are similar in magnitude to the decreases over many northern hemisphere land areas due to changes in air pollution over the same period. The change in cloud drop concentrations causes an increase in cloud reflectivity and a summertime radiative forcing between at 50 and 65°S comparable in magnitude but acting against that from greenhouse gas forcing over the same time period, and thus represents a substantial negative climate feedback. However, recovery of Antarctic ozone depletion in the next two decades will likely cause a fall in wind speeds, a decrease in cloud drop concentration and a correspondingly weaker cloud feedback.
Global mass flux solutions from GRACE: A comparison of parameter estimation strategies—Mass concentrations versus Stokes coefficients
Authors: Rowlands D. D. , Luthcke S. B. , McCarthy J. J. , Klosko S. M. , Chinn D. S. , Lemoine F. G. , Boy J.‐P. , Sabaka T. J.
Published: January 2010

The differences between mass concentration (mascon) parameters and standard Stokes coefficient parameters in the recovery of gravity information from gravity recovery and climate experiment (GRACE) intersatellite K‐band range rate data are investigated. First, mascons are decomposed into their Stokes coefficient representations to gauge the range of solutions available using each of the two types of parameters. Next, a direct comparison is made between two time series of unconstrained gravity solutions, one based on a set of global equal area mascon parameters (equivalent to 4° × 4° at the equator), and the other based on standard Stokes coefficients with each time series using the same fundamental processing of the GRACE tracking data. It is shown that in unconstrained solutions, the type of gravity parameter being estimated does not qualitatively affect the estimated gravity field. It is also shown that many of the differences in mass flux derivations from GRACE gravity solutions arise from the type of smoothing being used and that the type of smoothing that can be embedded in mascon solutions has distinct advantages over postsolution smoothing. Finally, a 1 year time series based on global 2° equal area mascons estimated every 10 days is presented.
Balanced approach of γδ T cells to type 2 immunity
Authors: Born Willi K , Huang Yafei , Jin Niyun , Huang Hua , O'Brien Rebecca L
Published: January 2010

Substantial evidence has been accumulated to indicate that γδ T cells take part in type 2 immune responses. It is not yet clear, however, in what capacity. Apparently, γδ T cells themselves can not only take the function of follicular T helper (TH) cells in certain responses, but also can support responses that are dependent on classical help provided by αβ T cells. Furthermore, the γδ T cells engage as regulators of TH2 immunity. Here, we consider two mouse models that depend on type 2 immunity, non‐specific airway hyperresponsiveness to methacholine after allergen inhalation challenge and the primary IgE response induced by alum‐aided immunization, and examine the function of γδ T cells. In either case, γδ T cells regulate type 2 immunity through balanced enhancing and inhibitory influences. However, after airway allergen exposure, suppressive γδ T cells become dominant. The underlying mechanisms are discussed.
Transcriptional regulation of the human acetoacetyl-CoA synthetase gene by PPARγ
Authors: Aguiló Francesca , Camarero Nuria , Relat Joana , Marrero Pedro F. , Haro Diego
Published: January 2010

In the cytosol of lipogenic tissue, ketone bodies are activated by AACS (acetoacetyl-CoA synthetase) and incorporated into cholesterol and fatty acids. AACS gene expression is particularly abundant in white adipose tissue, as it is induced during adipocyte differentiation. In order to elucidate the mechanism controlling the gene expression of human AACS and to clarify its physiological role, we isolated the human promoter, characterized the elements required to initiate transcription and analysed the expression of the gene in response to PPARγ (peroxisome-proliferator-activated receptor γ), an inducer of adipogenesis. We show that the human AACS promoter is a PPARγ target gene and that this nuclear receptor is recruited to the AACS promoter by direct interaction with Sp1 (stimulating protein-1).
Glucocorticoids inhibit IL-1β-induced GM-CSF expression at multiple levels: roles for the ERK pathway and repression by MKP-1
Authors: Newton Robert , King Elizabeth M. , Gong Wei , Rider Christopher F. , Staples Karl J. , Holden Neil S. , Bergmann Martin W.
Published: January 2010

In the present study, IL (interleukin)-1β increased GM-CSF (granulocyte/macrophage colony-stimulating factor) expression from pulmonary A549 cells and primary HBE (human bronchial epithelial) cells. These responses were repressed by the glucocorticoid dexamethasone, allowing the use of A549 cells as a relevant model. IL-1β induced GM-CSF release into the culture medium by 6 h and in cell lysates (cytosolic) at 2 h. These effects were profoundly inhibited by dexamethasone, yet IL-1β-induced GM-CSF mRNA and unspliced nRNA (nuclear RNA; a surrogate of transcription rate) were modestly inhibited by dexamethasone at times up to 2 h. Although this indicates an effect on protein synthesis, actinomycin D chase experiments also indicated post-transcriptional repression by dexamethasone. Dexamethasone-dependent mRNA repression increased with time and was prevented by translational blockade. In addition, dexamethasone and the dissociated steroid RU24858 repressed GM-CSF release in an actinomycin D-sensitive manner, thereby implicating glucocorticoid-induced gene expression. At 2 h, IL-1β-induced expression of GM-CSF protein, but not mRNA, was sensitive to the MEK [MAPK (mitogen-activated protein kinase)/ERK (extracellular-signal-regulated kinase) kinase] inhibitors PD098059 and U0126. Although this indicates a role for the MEK/ERK pathway in GM-CSF translation, PD098059 subsequently destabilized GM-CSF mRNA. Dexamethasone and RU24858 both reduced IL-1β-induced ERK phosphorylation and increased MKP-1 (MAPK phosphatase-1) expression. Inhibition of ERK phosphorylation was reproduced by MKP-1 overexpression and prevented by MKP-1-targeting siRNA (small interfering RNA). Since MKP-1 prevented GM-CSF expression by transcriptional, post-transcriptional and translational processes, we propose that glucocorticoids induce MKP-1 expression to reduce both MEK/ERK activation and GM-CSF protein synthesis. Thus de novo gene expression, particularly of MKP-1, is involved in the repressive effects of glucocorticoids.
Effect of timing of development on total cell number and expression profile of HSP‐70.1 and GLUT‐1 in buffalo (Bubalus bubalis) oocytes and preimplantation embryos produced in vitro
Authors: Rajhans Rajib , Kumar Sai G. , Dubey Pawan K. , Sharma Taru G.
Published: January 2010

The present study was designed to compare the expression profile of two developmentally important genes (HSP‐70.1 and GLUT‐1) and TCN (total cell number) count in fast (group A) and slow (group B) cleaved buffalo embryos to access their in vitro developmental competence. Buffalo COCs (cumulus oocyte complexes) were collected from local abattoir ovaries and subjected to in vitro maturation in: TCM‐199 supplemented with 10% FBS (fetal bovine serum), BSA (3 mg/ml), sodium pyruvate (0.25 mM) and 20 ng/ml EGF (epidermal growth factor) at 38.5°C under 5% CO2. In vitro derived embryos were collected at 4–8, 8–16 cell, morula and blastocyst stages at specific time points for gene expression analysis and total cell count. A semiquantitative RT‐PCR (reverse transcriptase‐PCR) assay was used to determine the HSP‐70.1 and GLUT‐1 transcripts. Results showed that developmental competence and TCN count in fast (group A)‐cleaving embryos was significantly (P<0.05) higher than in the slow group (group B). The gene transcript of HSP‐70.1 and GLUT‐1 was expressed in oocytes (immature and mature) and throughout the embryonic developmental stages in the fast group (group A), while in the slow (group B) cleaving embryos, the expression of HSP‐70.1 was absent in all the embryonic developmental stages, and expression of GLUT‐1 was absent after 8–16 cell stage. In conclusion, TCN count and expression profile of HSP‐70.1 and GLUT‐1 genes in buffalo embryos are different taking into account the cleavage rate. Quality of such embryos for research purposes, TCN and expression profiling of developmentally important genes should be employed to optimize the in vitro culture system to produce superior quality of embryos.
AMPK-mediated regulation of transcription in skeletal muscle
Authors: McGee Sean L. , Hargreaves Mark
Published: January 2010

Skeletal muscle phenotype plays a critical role in human performance and health, and skeletal muscle oxidative capacity is a key determinant of exercise tolerance. More recently, defective muscle oxidative metabolism has been implicated in a number of conditions associated with the metabolic syndrome, cardiovascular disease and muscle-wasting disorders. AMPK (AMP-activated protein kinase) is a critical regulator of cellular and organismal energy balance. AMPK has also emerged as a key regulator of skeletal muscle oxidative function, including metabolic enzyme expression, mitochondrial biogenesis and angiogenesis. AMPK mediates these processes primarily through alterations in gene expression. The present review examines the role of AMPK in skeletal muscle transcription and provides an overview of the known transcriptional substrates mediating the effects of AMPK on skeletal muscle phenotype.
Device physics of highly sensitive thin film polyfluorene copolymer organic phototransistors
Authors: Wang Xuhua , Wasapinyokul Kamol , De Tan Wei , Rawcliffe Ruth , Campbell Alasdair J. , Bradley Donal D. C.
Published: January 2010

We report on solution processed, highly light sensitive thin film transistors (TFTs) based on poly(9,9-dioctylfluorene-co-bithiophene) (F8T2). Transistors without heat treatment showed the highest saturation mobility, while devices annealed at 280°C showed the highest drain current. The latter annealed transistors were found to give highly stable and reproducible performance over many light cycles. Measurements were carried out using an inorganic light emitting diode (LED) light source with a peak wavelength of 465nm and 19nm bandwidth from 0to400μW∕cm2 light intensity on TFTs with an F8T2 film thickness of 30nm. The TFT OFF current was found to increase both with light intensity and gate bias. The bulk photogenerated carrier density was calculated to change from 5×1011to1×1013cm−3 over the measured light intensity range. The TFT saturation mobility did not change with light intensity, remaining constant at 1.2×10−4cm2∕Vs. The TFT ON current instead increased due to a shift in the turn-on voltage VT. This changed from −27to−20V over the measured light intensity range, initially changing rapidly but then saturating at higher intensity values. Contact resistance RC measurements showed large values in the dark. RC rapidly decreases with increasing light intensity, again saturating at higher values. From these results, we propose a phototransistor model in which illumination varies the device performance by effecting injection. By considering this shift in RC as photoassisted barrier lowering which additionally varies the width of the region depleted of carriers between the injecting interface and the channel, it is possible to explain the observed shift in VT as a change in the fraction of the gate bias dropped across the contact capacitance CC. By operating the phototransistor at a value of Vg=−5V (below VT), it was possible to achieve a highly linear response of the photocurrent with light intensity. Alternatively, by operating at a value of Vg=−40V (above VT), it was possible to maximize the photoresponsivity within the measured range. A photoresponsivity of 18.5A∕W at 5μW∕cm2 light intensity was achieved.
Coupling of Alfvén and sound waves in stellarator plasmas
Authors: Könies Axel , Eremin Denis
Published: January 2010

Recently, a low frequency mode possibly driven unstable by hot electrons [J. M. Canik et al., 21st IAEA Fusion Energy Conference, Chengdu (China) (IAEA, Vienna, 2006), CN-149EX/5-2] has been observed in the Helically Symmetric Experiment [F. S. B. Anderson et al., Fusion Technol. 27, 273 (1995)]. The emergence of such a mode has been investigated within the framework of computational three-dimensional magnetohydrodynamics (MHD). A three-dimensional MHD continuum code CONTI has been developed for a fast computation of the continuous Alfvén and sound spectrum. The global modes have been calculated using the CAS3D code. A possibly new class of modes has been identified which is generated by the interaction between sound and Alfvén waves. The respective gap still contains a continuum branch, so that because of the continuum interaction, a conclusive answer if these modes really exist cannot be achieved within the computational ideal MHD picture. Additionally, continuum gaps of similar type have been investigated also for other stellarators.
Electromagnetic effects on trace impurity transport in tokamak plasmas
Authors: Hein T. , Angioni C.
Published: January 2010

The impact of electromagnetic effects on the transport of light and heavy impurities in tokamak plasmas is investigated by means of an extensive set of linear gyrokinetic numerical calculations with the code GYRO [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] and of analytical derivations with a fluid model. The impurity transport is studied by appropriately separating diffusive and convective contributions, and conditions of background microturbulence dominated by both ion temperature gradient (ITG) and trapped electron modes (TEMs) are analyzed. The dominant contribution from magnetic flutter transport turns out to be of pure convective type. However it remains small, below 10% with respect to the E×B transport. A significant impact on the impurity transport due to an increase in the plasma normalized pressure parameter β is observed in the case of ITG modes, while for TEM the overall effect remains weak. In realistic conditions of high β plasmas in the high confinement (H-) mode with dominant ITG turbulence, the impurity diffusivity is found to decrease with increasing β in qualitative agreement with recent observations in tokamaks. In contrast, in these conditions, the ratio of the total off-diagonal convective velocity to the diagonal diffusivity is not strongly affected by an increase in β, particularly at low impurity charge, due to a compensation between the different off-diagonal contributions.
Low hole effective mass in thin InAs nanowires
Authors: dos Santos Cláudia L. , Piquini Paulo , Lima Erika N. , Schmidt Tome M.
Published: January 2010

The efficiency of nanoscale electronic devices usually is limited by the decrease in the carrier mobilities when the dimensionality is reduced. Using first principles calculations our results reveal that the hole effective masses of InAs nanowires decrease significantly below a threshold diameter. The mobilities have been estimated, and it is shown that for an optimal range of diameters, the hole mobilities exceeds the bulk value by up to five times, whereas the electron mobilities remain comparable to the bulk one. These results indicate that there exists a diameter window where p-type InAs based high-speed nanodevices can be fabricated.
Parametric study of laser-induced surface damage density measurements: Toward reproducibility
Authors: Lamaignère L. , Balas M. , Courchinoux R. , Donval T. , Poncetta J. C. , Reyné S. , Bertussi B. , Bercegol H.
Published: January 2010

In the range of nanosecond pulse lengths, the mechanisms of surface laser damage to dielectric materials are still unclear. A large amount of experimental and theoretical work has been performed over recent years. In order to test theoretical predictions and compare experimental results, reproducibility is essential whatever the beam parameters and experimental conditions. The rasterscan procedure, previously developed to test large components, is an efficient method that allows measuring extremely low surface damage site density (until 0.01 site/cm2 for large optics). In this paper, we show that by suitable data reduction, error bar calculation, and attention paid to beam analysis, laser-induced surface damage density of fused silica optics can be measured with high accuracy and repeatability in the range of pulse durations from 2 to 16 ns. This procedure provides a straightforward means of comparing the experimental results obtained from several facilities using different lasers.
Silicon nanowires synthesis on a submicronic terminal: Structural and electrical characterization
Authors: Abed Hichem , Sahaf Houda , Reguer Alan , Rochdi Nabil , Tonneau Didier , Bedu Frederic , Dallaporta Hervé , Jamgotchian Haik
Published: January 2010

In this work, we investigate localized silicon nanowires synthesis in a room temperature-controlled silane filled chamber using submicronic resistors as heating devices. These resistors consist in circuit-connected W wires obtained, on silicon oxide substrates, by focused ion beam induced deposition (FIBID) technology. Our study demonstrates that the morphology of the synthesized nanowires is temperature and time dependent revealing a thermal gradient but also both vapor-liquid-solid and vapor-solid growth effects. Typical silicon nanowires dimensions are a length of 1–2 μm and diameters of 30–40 nm. Structural characterization is performed by high resolution transmission electron microscopy using high energy electron transparent self-supported silicon nitride membranes. Electrical characteristics of FIBID- and self-connected nanowires are obtained. In both cases, they exhibit rectifying behavior.
Mapping of polymer melts onto liquids of soft-colloidal chains
Authors: Clark A. J. , Guenza M. G.
Published: January 2010

Microscopic computer simulations of fluids of long polymers are greatly restricted by the limits of current computational power, and so course-grained descriptions, accurate on molecular length scales, are essential to extending the range of accessible systems. For some phenomena, particularly dynamical entanglement, descriptions that eliminate all internal degrees of freedom from the polymers are too drastic, as intermediate wavelength degrees of freedom are essential to the effect. Employing first-principles liquid-state theory, we have developed a course-grained model for the intermolecular structure of melts of long homopolymer chains that maps each chain of hard-sphere monomers onto a chain of connected soft colloids. All dependence on system parameters is analytically expressed so the results may be immediately applied to melts with different polymer and thermodynamic properties to calculate effective potentials between the soft colloids on the chains, which can then be used to perform molecular dynamics simulations. These simulations will be able to capture the large wavelength structure of the system at greatly reduced computational cost, while still retaining enough internal degrees of freedom explicitly to describe the phenomena that occur on length scales much larger than the monomeric units that comprise the chain, but shorter than the size of the molecule.
Effect of magnetic field on temporal development of Rayleigh–Taylor instability induced interfacial nonlinear structure
Authors: Gupta M. R. , Mandal Labakanta , Roy Sourav , Khan Manoranjan
Published: January 2010

The effect of magnetic field on the nonlinear growth rate of Rayleigh–Taylor instability induced two fluid interfacial structures has been investigated. The magnetic field is assumed to be parallel to the plane of the two fluid interface and acts in a direction perpendicular to the wave vector. If the magnetic field is restricted only to either side of the interface, the growth rate may be depressed (may almost disappear) or be enhanced depending on whether the magnetic pressure on the interface opposes the instability driving pressure difference g(ρh−ρl)y or acts in the same direction. If magnetic field is present on both sides of the two fluid interface, stabilization may also take place in the sense that the surface of separation undulates periodically when the force due to magnetic pressure on two sides is such as to act in opposite direction. This result differs from the classical linear theory result which predicts that the magnetic field parallel to the surface has no influence on the growth rate when the wave vector is perpendicular to its direction.
Measurement of correlation-enhanced collision rates using pure ion plasmas
Authors: Anderegg F. , Driscoll C. F. , Dubin D. H. E. , O’Neil T. M.
Published: January 2010

This paper presents the first direct experimental measurements of the Salpeter enhancement of collisions due to particle correlations. The perpendicular-to-parallel collision rate ν⊥∥ is measured in laser-cooled pure ion plasmas, spanning the regimes from weak to strong magnetization, and from weak to strong particle correlations. The abrupt suppression of collisions in the strongly magnetized regime of T≲10−3 eV is observed, mitigated by the Salpeter enhancement when correlation effects become significant. This ν⊥∥ enhancement due to correlations is directly analogous to the enhancement of fusion collisions in hot dense stellar plasmas. The measured collisional enhancement is approximately exp(Γ), where Γ is the correlation parameter, and this is quantitatively consistent with analytical estimates based on thermal equilibrium shielding and correlations.
Experimental verification of light induced field emission
Authors: Kher S. , Dixit A. , Rawat D. N. , Sodha M. S.
Published: January 2010

This letter reports the experimental verification of the recently predicted phenomenon that the electric field emission current from a negatively charged surface gets enhanced by incidence of light (even of frequency below the photoelectric threshold) on the cathode.
Magnetic anisotropies in Ni–Mn–Ga films on MgO(001) substrates
Authors: Chernenko V. A. , Golub V. , Barandiarán J. M. , Salyuk O. Y. , Albertini F. , Righi L. , Fabbrici S. , Ohtsuka M.
Published: January 2010

Ferromagnetic resonance was used to study the influence of temperature and film thickness on magnetic properties of Ni–Mn–Ga films deposited on single crystal MgO(001) substrates. It has been shown that depending on the film thickness and preparation condition, three configurations of magnetic anisotropy can be realized in these films. The temperature dependence of the anisotropy field is determined.
Effect of channel width on the primary instability of inclined film flow
Authors: Vlachogiannis M. , Samandas A. , Leontidis V. , Bontozoglou V.
Published: January 2010

A procedure is developed to detect the onset of interfacial instability in inclined film flows (with estimated accuracy better than 5%) and is used to show that the finite width of experimental channels stabilizes the undisturbed liquid film. Deviation from the classical prediction scales inversely with the product of channel width and sine of inclination angle, and for small inclinations and/or narrow channels is of the order of 100%. The effect is tentatively attributed to the influence of sidewalls on the traveling disturbances, which results in curved crestlines and transverse variation of wave characteristics.
Influence of carbon content on the lattice variation, magnetic and electronic transport properties in Mn3SnCx
Authors: Wen Yongchun , Wang Cong , Nie Man , Sun Ying , Chu Lihua , Dong Cheng
Published: January 2010

The structural, magnetic, lattice, and electronic transport properties of Mn3SnCx compounds were investigated. Variation in carbon content from 0.6 to 1.2 does not change the crystal structure. With the increasing of x, the magnetic order changes from antiferromagnetic to ferromagnetic, and the transition temperature increases. The lattice constant shrinks around magnetic transition temperature when temperature increases. The total behavior of Mn3SnCx in temperature dependence of resistivity is very complex. For some Mn3SnCx, the temperature coefficient of resistivity is negative in the scope of magnetic order temperature. For other Mn3SnCx, the total behavior is metallic-type, and the resistivity appears an abrupt change.
Mechanically tunable surface plasmon resonance based on gold nanoparticles and elastic membrane polydimethylsiloxane composite
Authors: Chiang Yu-Lun , Chen Chih-Wei , Wang Chun-Hsiung , Hsieh Chun-Yi , Chen Yung-Ting , Shih Han-Yu , Chen Yang-Fang
Published: January 2010

Surface plasmon in nanoscaled materials has recently attracted a great deal of attention due to its possibility in a wide range of application. From a practical standpoint, it is desirable for the devices having a tunability of surface plasmon frequency. To achieve this goal, in this study, a composite consisting of two-dimensional gold nanoparticles array embedded in elastic polydimethylsiloxane (PDMS) membrane has been synthesized. Because the elastic PDMS membrane has a high malleability, with an external stress, it is very easy to regulate the interparticle distance in the gold nanoparticle array. The change in the distance between each nanoparticle will alter the surface plasmon interaction, and hence surface plasmon frequency can be manipulated. It is found that when the interparticle distance increases, the enhanced surface plasma mutual coupling will cause the blueshift of surface plasmon resonance frequency. The observed result satisfies the forecast based on electromagnetic theory.
Computational investigation of the influence of organic-aqueous interfaces on NaCl dissociation dynamics
Authors: Wick Collin D. , Dang Liem X.
Published: January 2010

NaCl pairing and dissociation was investigated at the CCl4-water and 1,2-dichloroethane (DCE)-water interfaces, and compared with dissociation results in the bulk and at the air-water interface utilizing polarizable potentials. The transition path sampling methodology was used to calculate the rate constant for dissociation, while umbrella sampling was used to map out a free energy profile for NaCl dissociation. The results found that ion pairing was weakest at the organic-water interfaces, even weaker than in the water bulk. This is in contrast to what has been observed previously for the air-water interface, in which NaCl ion paring is stronger than in the bulk [C. D. Wick, J. Phys. Chem. C 113, 6356 (2009)]. A consequence of the weaker binding at the organic-water interfaces was that ion dissociation was faster than in the other systems studied. Interactions of the organic phase with the ions influenced the magnitude of the Cl− induced dipole moment, and at the organic-water interfaces, the average Cl− induced dipole was found to be lower than at the air-water interface, weakening interactions with Na+. These weaker interactions were found to be responsible for the weaker ion pairing found at the organic-water interfaces.
Comment on “Comparison between solutions of the general dynamic equation and the kinetic equation for nucleation and droplet growth” [J. Chem. Phys. 130, 014102 (2009)]
Authors: Shneidman Vitaly A.
Published: January 2010

Numerical results obtained by Holten and van Dongen for the transient nucleation problem at large sizes are compared to the matched asymptotic (singular perturbation) solution of the discrete Becker–Döring equation. For not too small times, the agreement is excellent. Comparison also clarifies the structure of the nucleation source in the growth equation and explains some of the observed scaling dependences.
Symplekin promotes tumorigenicity by up-regulating claudin-2 expression
Authors: Buchert Michael , Papin Marina , Bonnans Caroline , Darido Charbel , Raye Warren S. , Garambois Véronique , Pélegrin André , Bourgaux Jean-François , Pannequin Julie , Joubert Dominique , Hollande Frédéric
Published: January 2010

Symplekin is a ubiquitously expressed protein involved in cytoplasmic RNA polyadenylation and transcriptional regulation and is localized at tight junctions (TJs) in epithelial cells. Nuclear symplekin cooperates with the Y-box transcription factor zonula occludens 1-associated nucleic acid-binding protein (ZONAB) to increase the transcription of cell cycle-related genes and also inhibits differentiation of intestinal cells. We detected high levels of nuclear symplekin in 8 of 12 human colorectal cancer (CRC) samples. shRNA-mediated reduction of symplekin expression was sufficient to decrease significantly the anchorage-independent growth and proliferation of HT-29 CRC cells as well as their tumorigenicity when injected into immunodeficient animals. Symplekin down-regulation also was found to alter ion transport through TJs, to promote the localization of ZONAB in the membrane rather than the nucleus, and strongly to enhance cell polarization in a 3D matrix, leading to the formation of spheroids organized around a central lumen. Claudin-2 expression was reduced following symplekin down-regulation, an effect mimicked when ZONAB expression was down-regulated using selective siRNA. Virus-mediated restoration of claudin-2 expression was found to restore nuclear expression of ZONAB in HT29ΔSym cells and to rescue the phenotypic alterations induced by symplekin down-regulation of cell polarity, paracellular transport, ZONAB localization, cyclin D1 expression, proliferation, and anchorage-independent growth. Finally, siRNA-mediated claudin-2 down-regulation increased the transepithelial resistance and decreased cyclin D1 expression and ZONAB nuclear localization, similar to observations in symplekin-depleted cells. Our results suggest that nuclear overexpression of symplekin promotes tumorigenesis in the human colon and that the regulation of claudin-2 expression is instrumental in this effect.
Spatio-temporal correlations can drastically change the response of a MAPK pathway
Authors: Takahashi Koichi , Tănase-Nicola Sorin , ten Wolde Pieter Rein
Published: January 2010

Multisite covalent modification of proteins is omnipresent in eukaryotic cells. A well-known example is the mitogen-activated protein kinase (MAPK) cascade where, in each layer of the cascade, a protein is phosphorylated at two sites. It has long been known that the response of a MAPK pathway strongly depends on whether the enzymes that modify the protein act processively or distributively. A distributive mechanism, in which the enzyme molecules have to release the substrate molecules in between the modification of the two sites, can generate an ultrasensitive response and lead to hysteresis and bistability. We study by Green’s Function Reaction Dynamics (GFRD), a stochastic scheme that makes it possible to simulate biochemical networks at the particle level in time and space, a dual phosphorylation cycle in which the enzymes act according to a distributive mechanism. We find that the response of this network can differ dramatically from that predicted by a mean-field analysis based on the chemical rate equations. In particular, rapid rebindings of the enzyme molecules to the substrate molecules after modification of the first site can markedly speed up the response and lead to loss of ultrasensitivity and bistability. In essence, rapid enzyme-substrate rebindings can turn a distributive mechanism into a processive mechanism. We argue that slow ADP release by the enzymes can protect the system against these rapid rebindings, thus enabling ultrasensitivity and bistability.
Influence of lever structure on myosin 5a walking
Authors: Oke Olusola A. , Burgess Stan A. , Forgacs Eva , Knight Peter J. , Sakamoto Takeshi , Sellers James R. , White Howard , Trinick John
Published: January 2010

Using electron microscopy and image processing, we have observed myosin 5a modified with lever arms of different lengths (four, six, and eight calmodulin-binding IQ domains) and orientations walking along actin filaments. Step lengths were dependent on lever length: 8IQ > 6IQ > 4IQ, which is consistent with myosin 5a having evolved to walk straight along actin. Lead heads were mostly in the prepowerstroke state, tethered there by the trail head. However, improved image processing showed that in 5–10% of molecules the lead motor was in the postpowerstroke state. This is a unique attached state of myosin, where the motor domain has completed its powerstroke at the expense of severe lever distortion, but with little cargo movement. Postpowerstroke lead heads were seen in both wild-type and modified lever molecules, mostly where there was least strain. These data allow the strain dependence of the equilibrium between pre- and postpowerstroke conformations to be measured. Slow rates of ADP dissociation observed from lead heads of these molecules can be explained by the unfavorable equilibrium between the pre- and postpowerstroke conformations preceding ADP loss.
Accelerated carcinogenesis following liver regeneration is associated with chronic inflammation-induced double-strand DNA breaks
Authors: Barash Hila , R. Gross Eitan , Edrei Yifat , Ella Ezra , Israel Ariel , Cohen Irit , Corchia Nathalie , Ben-Moshe Tehila , Pappo Orit , Pikarsky Eli , Goldenberg Daniel , Shiloh Yosef , Galun Eithan , Abramovitch Rinat
Published: January 2010

Hepatocellular carcinoma (HCC) is the third leading cause of cancer mortality worldwide and is considered to be the outcome of chronic liver inflammation. Currently, the main treatment for HCC is surgical resection. However, survival rates are suboptimal partially because of tumor recurrence in the remaining liver. Our aim was to understand the molecular mechanisms linking liver regeneration under chronic inflammation to hepatic tumorigenesis. Mdr2-KO mice, a model of inflammation-associated cancer, underwent partial hepatectomy (PHx), which led to enhanced hepatocarcinogenesis. Moreover, liver regeneration in these mice was severely attenuated. We demonstrate the activation of the DNA damage-response machinery and increased genomic instability during early liver inflammatory stages resulting in hepatocyte apoptosis, cell-cycle arrest, and senescence and suggest their involvement in tumor growth acceleration subsequent to PHx. We propose that under the regenerative proliferative stress induced by liver resection, the genomic unstable hepatocytes generated during chronic inflammation escape senescence and apoptosis and reenter the cell cycle, triggering the enhanced tumorigenesis. Thus, we clarify the immediate and long-term contributions of the DNA damage response to HCC development and recurrence.
Prelimbic cortical BDNF is required for memory of learned fear but not extinction or innate fear
Authors: Choi Dennis C. , Maguschak Kimberly A. , Ye Keqiang , Jang Sung-Wuk , Myers Karyn M. , Ressler Kerry J.
Published: January 2010

In the medial prefrontal cortex, the prelimbic area is emerging as a major modulator of fear behavior, but the mechanisms remain unclear. Using a selective neocortical knockout mouse, virally mediated prelimbic cortical-specific gene deletion, and pharmacological rescue with a TrkB agonist, we examined the role of a primary candidate mechanism, BDNF, in conditioned fear. We found consistently robust deficits in consolidation of cued fear but no effects on acquisition, expression of unlearned fear, sensorimotor function, and spatial learning. This deficit in learned fear in the BDNF knockout mice was rescued with systemic administration of a TrkB receptor agonist, 7,8-dihydroxyflavone. These data indicate that prelimbic BDNF is critical for consolidation of learned fear memories, but it is not required for innate fear or extinction of fear. Moreover, use of site-specific, inducible BDNF deletions shows a powerful mechanism that may further our understanding of the pathophysiology of fear-related disorders.
The AAA+ ClpX machine unfolds a keystone subunit to remodel the Mu transpososome
Authors: Abdelhakim Aliaa H. , Sauer Robert T. , Baker Tania A.
Published: January 2010

A hyperstable complex of the tetrameric MuA transposase with recombined DNA must be remodeled to allow subsequent DNA replication. ClpX, a AAA+ enzyme, fulfills this function by unfolding one transpososome subunit. Which MuA subunit is extracted, and how complex destabilization relates to establishment of the correct directionality (left to right) of Mu replication, is not known. Here, using altered-specificity MuA proteins/DNA sites, we demonstrate that transpososome destabilization requires preferential ClpX unfolding of either the catalytic-left or catalytic-right subunits, which make extensive intersubunit contacts in the tetramer. In contrast, ClpX recognizes the other two subunits in the tetramer much less efficiently, and their extraction does not substantially destabilize the complex. Thus, ClpX targets the most stable structural components of the complex. Left-end biased Mu replication is not, however, determined by ClpX’s intrinsic subunit preference. The specific targeting of a stabilizing “keystone subunit” within a complex for unfolding is an attractive general mechanism for remodeling by AAA+ enzymes.
Female teachers’ math anxiety affects girls’ math achievement
Authors: Beilock Sian L. , Gunderson Elizabeth A. , Ramirez Gerardo , Levine Susan C.
Published: January 2010

People’s fear and anxiety about doing math—over and above actual math ability—can be an impediment to their math achievement. We show that when the math-anxious individuals are female elementary school teachers, their math anxiety carries negative consequences for the math achievement of their female students. Early elementary school teachers in the United States are almost exclusively female (>90%), and we provide evidence that these female teachers’ anxieties relate to girls’ math achievement via girls’ beliefs about who is good at math. First- and second-grade female teachers completed measures of math anxiety. The math achievement of the students in these teachers’ classrooms was also assessed. There was no relation between a teacher’s math anxiety and her students’ math achievement at the beginning of the school year. By the school year’s end, however, the more anxious teachers were about math, the more likely girls (but not boys) were to endorse the commonly held stereotype that “boys are good at math, and girls are good at reading” and the lower these girls’ math achievement. Indeed, by the end of the school year, girls who endorsed this stereotype had significantly worse math achievement than girls who did not and than boys overall. In early elementary school, where the teachers are almost all female, teachers’ math anxiety carries consequences for girls’ math achievement by influencing girls’ beliefs about who is good at math.
Breakdown in cortical effective connectivity during midazolam-induced loss of consciousness
Authors: Ferrarelli Fabio , Massimini Marcello , Sarasso Simone , Casali Adenauer , Riedner Brady A. , Angelini Giuditta , Tononi Giulio , Pearce Robert A.
Published: January 2010

By employing transcranial magnetic stimulation (TMS) in combination with high-density electroencephalography (EEG), we recently reported that cortical effective connectivity is disrupted during early non-rapid eye movement (NREM) sleep. This is a time when subjects, if awakened, may report little or no conscious content. We hypothesized that a similar breakdown of cortical effective connectivity may underlie loss of consciousness (LOC) induced by pharmacologic agents. Here, we tested this hypothesis by comparing EEG responses to TMS during wakefulness and LOC induced by the benzodiazepine midazolam. Unlike spontaneous sleep states, a subject’s level of vigilance can be monitored repeatedly during pharmacological LOC. We found that, unlike during wakefulness, wherein TMS triggered responses in multiple cortical areas lasting for >300 ms, during midazolam-induced LOC, TMS-evoked activity was local and of shorter duration. Furthermore, a measure of the propagation of evoked cortical currents (significant current scattering, SCS) could reliably discriminate between consciousness and LOC. These results resemble those observed in early NREM sleep and suggest that a breakdown of cortical effective connectivity may be a common feature of conditions characterized by LOC. Moreover, these results suggest that it might be possible to use TMS-EEG to assess consciousness during anesthesia and in pathological conditions, such as coma, vegetative state, and minimally conscious state.
RETRACTED: Evidence for a functional role of IgE anticitrullinated protein antibodies in rheumatoid arthritis
Authors: Schuerwegh A. J. M. , Ioan-Facsinay A. , Dorjée A. L. , Roos J. , Bajema I. M. , van der Voort E. I. H. , Huizinga T. W. J. , Toes R. E. M.
Published: January 2010

Rheumatoid arthritis (RA) is a systemic autoimmune disease involving inflammation of the joints. Among the autoantibodies described in RA, anticitrullinated protein antibodies (ACPAs) are highly specific and predictive for RA. In addition, ACPAs have been implicated in the pathogenesis of RA. However, a direct functional response of immune cells from ACPA
+
RA patients toward citrullinated proteins has not been demonstrated. In this study, we show that exposure to citrullinated antigens leads to activation of basophils from ACPA
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RA patients within 20 minutes. This was not observed after exposure of basophils to noncitrullinated control antigens or after stimulation of basophils from ACPA
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RA patients and healthy controls. Basophil activation was correlated with the binding of citrullinated proteins to basophils. Furthermore, serum from ACPA
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RA patients in contrast to that from ACPA
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RA patients could specifically sensitize human FcεRI expressing rat basophil cells (RBL), enabling activation by citrullinated proteins. Mast cell degranulation products such as histamine levels were enhanced in synovial fluid of ACPA
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RA patients as compared with ACPA
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RA and osteoarthritis patients. In addition, histamine levels in synovial fluid from ACPA
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RA patients correlated with IgE levels, suggesting degranulation of mast cells by cross-linking IgE. Immunohistochemistry on synovial biopsies demonstrated an increased number of degranulated CD117
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mast cells in ACPA
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RA patients; IgE and FcεRI expression in synovial mast cells from ACPA
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RA patients was increased. In conclusion, our results show an immunological response of immune cells from ACPA
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RA patients in a citrulline-specific manner. Moreover, these data indicate a role for IgE-ACPAs and FcεRI-positive cells in the pathogenesis of RA.