bluuebunny/crossref_metadata_2025 huggingface dataset:
Afterword
Authors: R.E.M.G.
Published: April 2012

The week's communications and deliberations concentrated on dQ/dt and how we could enhance our detection and interpretation of such occurrences, whether Q were a distance, an emission of energy, a velocity, a brightness, an orbital property or a spectroscopic feature. For us mortals, the derivative of Q is in respect of Time—yet rather little attention was paid during the week to Time itself. Maybe that was just as well. As was said by way of introducing the Astronomer Royal to give the public lecture, From Microseconds to Æons, Time is ever-present yet always elusive. It flies and yet it drags. We never seem to have enough of it, yet it can weigh heavily on our hands. It is free but it is priceless. You can't own it but you can spend it. Einstein said bluntly that the only reason for Time is so that everything doesn't happen at once.
Effects of mineral distribution at mesoscopic scale on solute diffusion in a clay‐rich rock: Example of the Callovo‐Oxfordian mudstone (Bure, France)
Authors: Robinet Jean‐Charles , Sardini Paul , Coelho Daniel , Parneix Jean‐Claude , Prêt Dimitri , Sammartino Stéphane , Boller Elodie , Altmann Scott
Published: April 2012

The mesostructure (millimeter to micrometer scale) of clay‐rich sedimentary rocks is generally characterized by a connected fine‐grained clay matrix embedding coarser nonclay minerals. We use the Callovo‐Oxfordian clay‐rich rock formation (France) to illustrate how mesostructure influences solute transfer in clay‐rich rocks at larger scales. Using micrometer resolution imaging techniques (SEM and micro‐CT) major mineral phases (clay matrix, carbonates, tectosilicates, and heavy minerals) were mapped both in two dimensional (2‐D) and three dimensional (3‐D) at the mesoscale. Orientation and elongation distributions of carbonate and tectosilicate grains measured on mineral maps reveal an anisotropic mesostructure relative to the bedding plane, in agreement with the geological history of the sedimentary rock. Diffusion simulations were performed based on the 3‐D mineral maps using a random walk method thus allowing direct computation of mesoscopic scale‐related diffusion anisotropy and tortuosity. Considering an isotropic clay matrix, simulated diffusion anisotropy (1.11–1.26) was found lower than the one experimentally measured on macroscopic samples (1.5 to 2), due to the anisotropy feature of pores within the clay matrix. The effects of the mineral content variations on diffusion properties were then investigated by numerical modifications of a mineral map combined with diffusion simulations. Evolution of the tortuosity and diffusion anisotropy with the clay matrix content were successfully interpreted by the Koponen percolation/diffusion model, whereas the Archie approach fails to reproduce diffusion properties at low clay contents. A comparison of fitting parameters with those obtained experimentally indicates that diffusion coefficient variations observed at a large scale could be mainly controlled by the mesostructure.
Is it the grain size or the characteristic pore size that controls the induced polarization relaxation time of clean sands and sandstones?
Authors: Revil André , Koch Kristof , Holliger Klaus
Published: April 2012

There is a wide range of evidence to suggest that permeability can be constrained through of induced polarization measurements. For clean sands and sandstones, current mechanistic models of induced polarization predict a relationship between the low‐frequency time constant inferred from induced polarization measurements and the grain diameter. A number of observations do, however, disagree with this and indicate that the observed relaxation behavior is rather governed by the so‐called dynamic pore radius Λ. To test this hypothesis, we have developed a set of new scaling relationships, which allow the relaxation time to be computed from the pore size and the permeability to be computed from both the Cole‐Cole time constant and the formation factor. Moreover, these new scaling relationships can be also used to predict the dependence of the Cole‐Cole time constant as a function of the water saturation under unsaturated conditions. Comparative tests of the proposed new relationships with regard to various published experimental results for saturated clean sands and sandstones as well as for partially saturated clean sandstones, do indeed confirm that the dynamic pore radius Λ is a much more reliable indicator of the observed relaxation behavior than grain‐size‐based models.
Evaluation of ionospheric densities using coincident OII 83.4 nm airglow and the Millstone Hill Radar
Authors: Douglas E. S. , Smith S. M. , Stephan A. W. , Cashman L. , Bishop R. L. , Budzien S. A. , Christensen A. B. , Hecht J. H. , Chakrabarti S.
Published: April 2012

We test the utility of the OII 83.4 nm emission feature as a measure of ionospheric parameters. Observed with the Remote Atmospheric and Ionospheric Detection System (RAIDS) Extreme Ultraviolet Spectrograph on the International Space Station (ISS), limb profiles of 83.4 nm emissions are compared to predicted dayglow emission profiles from a theoretical model incorporating ground‐based electron density profiles measured by the Millstone Hill radar and parameterized by a best‐fit Chapman‐α function. Observations and models are compared for periods of conjunction between Millstone Hill and the RAIDS fields‐of‐view. These RAIDS observations show distinct differences in topside morphology between two days, 15 January and 10 March 2010, closely matching the forward model morphology and demonstrating that 83.4 nm emission is sensitive to changes in the ionospheric density profile from the 340 km altitude of the ISS during solar minimum. We find no significant difference between 83.4 nm emission profiles modeled assuming a constant scale height Chapman‐α best‐fit to the ISR measurements and those assuming varying scale height.
Structure and activity of the cold-active and anion-activated carboxyl esterase OLEI01171 from the oil-degrading marine bacteriumOleispira antarctica
Authors: Lemak Sofia , Tchigvintsev Anatoli , Petit Pierre , Flick Robert , Singer Alexander U. , Brown Greg , Evdokimova Elena , Egorova Olga , Gonzalez Claudio F. , Chernikova Tatyana N. , Yakimov Michail M. , Kube Michael , Reinhardt Richard , Golyshin Peter N. , Savchenko Alexei , Yakunin Alexander F.
Published: April 2012

The uncharacterized α/β-hydrolase protein OLEI01171 from the psychrophilic marine bacterium Oleispira antarctica belongs to the PF00756 family of putative esterases, which also includes human esterase D. In the present paper we show that purified recombinant OLEI01171 exhibits high esterase activity against the model esterase substrate α-naphthyl acetate at 5—30°C with maximal activity at 15–20°C. The esterase activity of OLEI01171 was stimulated 3–8-fold by the addition of chloride or several other anions (0.1–1.0 M). Compared with mesophilic PF00756 esterases, OLEI01171 exhibited a lower overall protein thermostability. Two crystal structures of OLEI01171 were solved at 1.75 and 2.1 Å resolution and revealed a classical serine hydrolase catalytic triad and the presence of a chloride or bromide ion bound in the active site close to the catalytic Ser148. Both anions were found to co-ordinate a potential catalytic water molecule located in the vicinity of the catalytic triad His257. The results of the present study suggest that the bound anion perhaps contributes to the polarization of the catalytic water molecule and increases the rate of the hydrolysis of an acyl-enzyme intermediate. Alanine replacement mutagenesis of OLEI01171 identified ten amino acid residues important for esterase activity. The replacement of Asn225 by lysine had no significant effect on the activity or thermostability of OLEI01171, but resulted in a detectable increase of activity at 35–45°C. The present study has provided insight into the molecular mechanisms of activity of a cold-active and anion-activated carboxyl esterase.
Hidden symmetries and supergravity solutions
Authors: Santillan Osvaldo P.
Published: April 2012

The role of Killing and Killing-Yano tensors for studying the geodesic motion of the particle and the superparticle in a curved background is reviewed. Additionally, the Papadopoulos list [G. Papadopoulos, Class. Quantum Grav. 25, 105016 (2008)]10.1088/0264-9381/25/10/105016 for Killing-Yano tensors in G structures is reproduced by studying the torsion types these structures admit. The Papadopoulos list deals with groups G appearing in the Berger classification, and we enlarge the list by considering additional G structures which are not of the Berger type. Possible applications of these results in the study of supersymmetric particle actions and in the AdS/CFT correspondence are outlined.
Mixture model for determination of shock equation of state
Authors: Jordan Jennifer L. , Baer Melvin R.
Published: April 2012

Simple mixture models for the prediction of shock equations of state (Hugoniot) are a necessary tool for characterization of multiple composites. A mixture model for determining the shock equation of state of composite materials is presented. The model is completely flexible allowing for multiple (>2) components. Additionally, error propagation analysis for the two component mixture model has been accomplished. The model predicts the equation of state to 5%–15% of the experimental data, which is comparable to variations realized in meso-scale modeling of similar materials.
High spatial resolution, high energy synchrotron x-ray diffraction characterization of residual strains and stresses in laser shock peened Inconel 718SPF alloy
Authors: Gill Amrinder S. , Zhou Zhong , Lienert Ulrich , Almer Jonathan , Lahrman David F. , Mannava S. R. , Qian Dong , Vasudevan Vijay K.
Published: April 2012

Laser shock peening (LSP) is an advanced surface enhancement technique used to enhance the fatigue strength of metal parts by imparting deep compressive residual stresses. In the present study, LSP was performed on IN718 SPF alloy, a fine grained nickel-based superalloy, with three different power densities and depth resolved residual strain and stress characterization was conducted using high energy synchrotron x-ray diffraction in beam line 1-ID-C at the Advanced Photon Source at the Argonne National laboratory. A fine probe size and conical slits were used to non-destructively obtain data from specific gauge volumes in the samples, allowing for high-resolution strain measurements. The results show that LSP introduces deep compressive residual stresses and the magnitude and depth of these stresses depend on the energy density of the laser. The LSP induced residual stresses were also simulated using three-dimensional nonlinear finite element analysis, with employment of the Johnson-Cook model for describing the nonlinear materials constitutive behavior. Good agreement between the experimental and simulated data was obtained. These various results are presented and discussed.
Frequency and damping of non-axisymmetric surface oscillations of a viscous axisymmetric liquid bridge
Authors: Kidambi R.
Published: April 2012

The frequency and damping of free lateral linear oscillations of a viscous non-cylindrical liquid bridge, formed between two axial disks of radii R1 and R2, are computed using a recently developed semi-analytic procedure [R. Kidambi, J. Fluid Mech. 681, 597 (2011)]. A comparison with recent experimental results [E. J. Vega and J. M. Montanero, Phys. Fluids 21, 092101 (2009)] for the first non-axisymmetric mode over a range of bridge volumes is good and the damping rate is better predicted than by a one-dimensional slice model especially for highly viscous bridges. The procedure can be used to calculate the oscillation characteristics of any desired mode for any region of the parameter space.
Effect of atomic monolayer insertions on electric-field-induced rotation of magnetic easy axis
Authors: Tsujikawa M. , Haraguchi S. , Oda T.
Published: April 2012

We have investigated the electric field (EF) effect on the magnetic anisotropy energy (MAE) in the thin films MgO/M/Fe/Au(001) and MgO/Fe/M(001) (M = Pd, Pt, and Au) by means of first-principles density-functional calculations. We find that the MAE varies linearly with the EF and investigate the change in slope of the MAE as a function of the EF as the buffer layer is changed. We find that a single monatomic buffer layer may be useful for devices that use EF-modified MAE. We simulate the critical EF for easy-axis rotation and discuss interface effects of Mg/Fe and Fe/Au on MAE.
Analytical model for the dynamics of semiflexible dendritic polymers
Authors: Fürstenberg Florian , Dolgushev Maxim , Blumen Alexander
Published: April 2012

We study the dynamics of semiflexible dendritic polymers following the method of Dolgushev and Blumen [J. Chem. Phys. 131, 044905 (2009)10.1063/1.3184797]. The scheme allows to formulate in analytical form the corresponding Langevin equations. We determine the eigenvalues by first block-diagonalizing the problem, which allows to treat even very large dendritic objects. A basic ingredient of the procedure is the observation that a set of eigenmodes in the semiflexible case is similar to that chosen by Cai and Chen [Macromolecules 30, 5104 (1997)10.1021/ma970059z] for fully flexible dendritic structures. Varying the flexibility of the macromolecules allows us to better understand their mechanical loss moduli G″(ω) based on their eigenvalue spectra. We present the G″(ω) for a series of stiffness parameters and for different functionalities of the branching points.
Microwave-induced excess quasiparticles in superconducting resonators measured through correlated conductivity fluctuations
Authors: de Visser P. J. , Baselmans J. J. A. , Yates S. J. C. , Diener P. , Endo A. , Klapwijk T. M.
Published: April 2012

We have measured the number of quasiparticles and their lifetime in aluminium superconducting microwave resonators. The number of excess quasiparticles below 160 mK decreases from 72 to 17 μm−3 with a 6 dB decrease of the microwave power. The quasiparticle lifetime increases accordingly from 1.4 to 3.5 ms. These properties of the superconductor were measured through the spectrum of correlated fluctuations in the quasiparticle system and condensate of the superconductor, which show up in the resonator amplitude and phase, respectively. Because uncorrelated noise sources vanish, fluctuations in the superconductor can be studied with a sensitivity close to the vacuum noise.
Spin-dependent tunneling transport in a ferromagnetic GaMnAs and un-doped GaAs double-quantum-well heterostructure
Authors: Muneta Iriya , Ohya Shinobu , Tanaka Masaaki
Published: April 2012

We investigate the spin-dependent tunneling transport in a ferromagnetic GaMnAs and un-doped GaAs double-quantum-well heterostructure. Clear tunneling magnetoresistance (TMR) and negative differential resistance due to the strong resonant tunneling in the GaAs quantum well (QW) are demonstrated in this device. We show that TMR oscillates as a function of the bias voltage following the dI/dV-V characteristics, and TMR becomes negative at biases where resonant tunneling occurs. These results can be explained by the difference of the potential drops in the magnetic tunnel junction composed of the top GaMnAs/AlAs/GaMnAs-QW between parallel and anti-parallel magnetization.
384 nm laser diode grown on a (202¯1) semipolar relaxed AlGaN buffer layer
Authors: Haeger Daniel A. , Young Erin C. , Chung Roy B. , Wu Feng , Pfaff Nathan A. , Tsai Min , Fujito Kenji , DenBaars Steven P. , Speck James S. , Nakamura Shuji , Cohen Daniel A.
Published: April 2012

We demonstrate an electrically injected semipolar (202¯1) laser diode grown on a partially relaxed AlGaN buffer layer. The coherency stresses are relaxed by misfit dislocations at the GaN/AlGaN heterointerface which form by glide of preexisting threading dislocations along the (0001) basal plane. The defects are confined to the heterointerface which allows the growth of high aluminum composition films with threading dislocation densities of less than 108 cm−2. The lasing wavelength was 384 nm with a threshold current density of 15.7 kA/cm−2. UV lasers grown on semipolar relaxed AlGaN buffers provide an alternative to devices grown on AlN or sapphire.
High photocurrent from planar strips of vertical and horizontal aligned multi wall carbon nanotubes
Authors: Passacantando M. , Grossi V. , Santucci S.
Published: April 2012

We report on a significant photocurrent generation from a planar device made by growing simultaneously different strips of vertically and horizontally aligned multi-wall carbon nanotubes, obtained under white light and different wavelengths in the visible region. We show that the photocurrent of all strips increases with decreasing the strip length and, the highest photoconversion is found to be in the blue-shift visible region. This significant photocurrent generation at lower wavelengths is directly related to the absorbance properties of multi-wall carbon nanotubes and a Raman spectroscopy study confirms that the most part of innermost tubes have a semiconducting nature.
Mechanism of GaN quantum dot overgrowth by Al0.5Ga0.5N: Strain evolution and phase separation
Authors: Korytov M. , Budagosky J. A. , Brault J. , Huault T. , Benaissa M. , Neisius T. , Rouvière J.-L. , Vennéguès P.
Published: April 2012

The capping of GaN quantum dots (QDs) with an Al0.5Ga0.5N layer is studied using transmission electron microscopy and atomic force microscopy in combination with theoretical calculations. The capping process can be divided into several well-distinguishable stages including a QD shape change and a local change of the Al0.5Ga0.5N capping layer composition. The phase separation phenomenon is investigated in relation with the capping layer thickness. Amount of the chemical composition fluctuations is determined from separate analysis of scanning transmission electron microscopy and high-resolution transmission electron microscopy images. The local distortion of atomic lattice in the QD surroundings is measured by high-resolution electron microscopy and is confronted with theoretically calculated strain distributions. Based on these data, a possible mechanism of alloy demixing in the Al0.5Ga0.5N layer is discussed.
Semipolar {nn¯01} InGaN/GaN ridge quantum wells (n = 1−3) fabricated by a regrowth technique
Authors: Funato Mitsuru , Kotani Teruhisa , Kondou Takeshi , Kawakami Yoichi
Published: April 2012

Semipolar {nn¯01} InGaN/GaN quantum wells (QWs) (n = 1−3) are fabricated on top of GaN microstructures, which consist of semipolar {11¯01} facets. Semipolar planes are obtained via regrowth of three-dimensional structures on (0001) GaN templates under controlled growth conditions. Compared to QWs on {11¯01} facets, {nn¯01} ridge QWs show an intense emission at ∼440 nm. Time resolved photoluminescence reveals that the radiative lifetime of excitons in {nn¯01} InGaN ridge QWs at 13 K is 310 ps, which is comparable to that in {11¯01} QWs. The estimated internal quantum efficiency at room temperature is as high as 57%.
Improvement in the device performance of tin-doped indium oxide transistor by oxygen high pressure annealing at 150 °C
Authors: Yeob Park Se , Hwan Ji Kwang , Yoon Jung Hong , Kim Ji-In , Choi Rino , Seok Son Kyoung , Kwan Ryu Myung , Lee Sangyoon , Kyeong Jeong Jae
Published: April 2012

This study examined the effect of oxygen (O2) high pressure annealing (HPA) on tin-doped indium oxide (ITO) thin film transistors (TFTs). The HPA-treated TFT at 150 °C exhibited a high saturation mobility (μSAT), low subthreshold gate swing (SS), threshold voltage, and Ion/off of 25.8 cm2/Vs, 0.14 V/decade, 0.6 V, and 2 × 108, respectively. In contrast, the ambient-annealed device suffered from a lower μSAT and high SS value of 5.2 cm2/Vs and 0.58 V/decade, respectively. This improvement can be attributed to the decreased concentration of oxygen vacancy defects in the ITO channel layer during the effective O2 HPA treatment, which also resulted in smaller hysteresis and less degradation of the drain current under positive bias stress conditions.
Terahertz phase microscopy in the sub-wavelength regime
Authors: Yi Minwoo , Lee Kanghee , Song Jin-Dong , Ahn Jaewook
Published: April 2012

Gouy phase shift is a well-known behavior that occurs when a propagating light is focused, but its behavior in the sub-wavelength confinement is not yet known. Here, we report the theoretical and experimental study of the aperture-size dependency of the Gouy phase shift in the sub-wavelength diffraction regime. In experiments carried out with laser-induced terahertz (THz) wave emission from various semiconductor apertures, we demonstrate the use of Guoy phase shit for sub-wavelength THz microscopy.
Observation of dual magnonic and phononic bandgaps in bi-component nanostructured crystals
Authors: Zhang V. L. , Ma F. S. , Pan H. H. , Lin C. S. , Lim H. S. , Ng S. C. , Kuok M. H. , Jain S. , Adeyeye A. O.
Published: April 2012

We report on the experimental observation of dual magnonic and phononic bandgaps in bi-component nanostructured crystals. The dispersion relations of linear periodic arrays of alternating Fe (or Ni) and Ni80Fe20 nanostripes on a SiO2/Si substrate, mapped by Brillouin spectroscopy, feature distinct bandgaps. Calculations of the magnon and phonon dispersions yield good agreement with experiments. No magnon-phonon interaction is detected for the modes observed, making the structures studied a potential platform for the separate and simultaneous processing of information carried by hypersonic magnons and phonons, with no undesirable cross-talk between them.
Molecular genetic basis of pod corn (
Tunicate
maize)
Authors: Wingen Luzie U. , Münster Thomas , Faigl Wolfram , Deleu Wim , Sommer Hans , Saedler Heinz , Theißen Günter
Published: April 2012

Pod corn is a classic morphological mutant of maize in which the mature kernels of the cob are covered by glumes, in contrast to generally grown maize varieties in which kernels are naked. Pod corn, known since pre-Columbian times, is the result of a dominant gain-of-function mutation at the
Tunicate
(
Tu
) locus. Some classic articles of 20th century maize genetics reported that the mutant
Tu
locus is complex, but molecular details remained elusive. Here, we show that pod corn is caused by a
cis
-regulatory mutation and duplication of the
ZMM19
MADS-box gene. Although the WT locus contains a single-copy gene that is expressed in vegetative organs only, mutation and duplication of
ZMM19
in
Tu
lead to ectopic expression of the gene in the inflorescences, thus conferring vegetative traits to reproductive organs.
Dynamic integration of information about salience and value for saccadic eye movements
Authors: Schütz Alexander C. , Trommershäuser Julia , Gegenfurtner Karl R.
Published: April 2012

Humans shift their gaze to a new location several times per second. It is still unclear what determines where they look next. Fixation behavior is influenced by the low-level salience of the visual stimulus, such as luminance, contrast, and color, but also by high-level task demands and prior knowledge. Under natural conditions, different sources of information might conflict with each other and have to be combined. In our paradigm, we trade off visual salience against expected value. We show that both salience and value information influence the saccadic end point within an object, but with different time courses. The relative weights of salience and value are not constant but vary from eye movement to eye movement, depending critically on the availability of the value information at the time when the saccade is programmed. Short-latency saccades are determined mainly by salience, but value information is taken into account for long-latency saccades. We present a model that describes these data by dynamically weighting and integrating detailed topographic maps of visual salience and value. These results support the notion of independent neural pathways for the processing of visual information and value.
Eukaryotic-type plastid nucleoid protein pTAC3 is essential for transcription by the bacterial-type plastid RNA polymerase
Authors: Yagi Yusuke , Ishizaki Yoko , Nakahira Yoichi , Tozawa Yuzuru , Shiina Takashi
Published: April 2012

Plastid transcription is mediated by two distinct types of RNA polymerases (RNAPs), bacterial-type RNAP (PEP) and phage-type RNAP (NEP). Recent genomic and proteomic studies revealed that higher plants have lost most prokaryotic transcription regulators and have acquired eukaryotic-type proteins during plant evolution. However, in vivo dynamics of chloroplast RNA polymerases and eukaryotic-type plastid nucleoid proteins have not been directly characterized experimentally. Here, we examine the association of the α-subunit of PEP and eukaryotic-type protein, plastid transcriptionally active chromosome 3 (pTAC3) with transcribed regions in vivo by using chloroplast chromatin immunoprecipitation (cpChIP) assays. PEP α-subunit preferentially associates with PEP promoters of photosynthesis and rRNA genes, but not with NEP promoter regions, suggesting selective and accurate recognition of PEP promoters by PEP. The cpChIP assays further demonstrate that the peak of PEP association occurs at the promoter-proximal region and declines gradually along the transcribed region. pTAC3 is a putative DNA-binding protein that is localized to chloroplast nucleoids and is essential for PEP-dependent transcription. Density gradient and immunoprecipitation analyses of PEP revealed that pTAC3 is associated with the PEP complex. Interestingly, pTAC3 associates with the PEP complex not only during transcription initiation, but also during elongation and termination. These results suggest that pTAC3 is an essential component of the chloroplast PEP complex. In addition, we demonstrate that light-dependent chloroplast transcription is mediated by light-induced association of the PEP–pTAC3 complex with promoters. This study illustrates unique dynamics of PEP and its associated protein pTAC3 during light-dependent transcription in chloroplasts.
Alternative pathway for atmospheric particles growth
Authors: Monge Maria Eugenia , Rosenørn Thomas , Favez Olivier , Müller Markus , Adler Gabriela , Abo Riziq Ali , Rudich Yinon , Herrmann Hartmut , George Christian , D’Anna Barbara
Published: April 2012

Credible climate change predictions require reliable fundamental scientific knowledge of the underlying processes. Despite extensive observational data accumulated to date, atmospheric aerosols still pose key uncertainties in the understanding of Earth’s radiative balance due to direct interaction with radiation and because they modify clouds’ properties. Specifically, major gaps exist in the understanding of the physicochemical pathways that lead to aerosol growth in the atmosphere and to changes in their properties while in the atmosphere. Traditionally, the driving forces for particle growth are attributed to condensation of low vapor pressure species following atmospheric oxidation of volatile compounds by gaseous oxidants. The current study presents experimental evidence of an unaccounted-for new photoinduced pathway for particle growth. We show that heterogeneous reactions activated by light can lead to fast uptake of noncondensable Volatile Organic Compounds (VOCs) at the surface of particles when only traces of a photosensitizer are present in the seed aerosol. Under such conditions, size and mass increase; changes in the chemical composition of the aerosol are also observed upon exposure to volatile organic compounds such as terpenes and near-UV irradiation. Experimentally determined growth rate values match field observations, suggesting that this photochemical process can provide a new, unaccounted-for pathway for atmospheric particle growth and should be considered by models.
Astrocytic high-mobility group box 1 promotes endothelial progenitor cell-mediated neurovascular remodeling during stroke recovery
Authors: Hayakawa Kazuhide , Pham Loc-Duyen D. , Katusic Zvonimir S. , Arai Ken , Lo Eng H.
Published: April 2012

Crosstalk between the brain and systemic responses in blood is increasingly suspected of playing critical roles in stroke. However, how this communication takes place remains to be fully understood. Here, we show that reactive astrocytes can release a damage-associated molecular-pattern molecule called high-mobility-group-box-1 (HMGB1) that promotes endothelial progenitor cell (EPC)-mediated neurovascular remodeling during stroke recovery. Conditioned media from reactive astrocytes increase EPC proliferation in vitro. siRNA suppression of HMGB1 in astrocytes or blockade of the HMGB1 receptor for advanced glycation endproducts in EPCs prevents this effect. In a mouse model of focal cerebral ischemia, reactive astrocytes in the peri-infarct cortex up-regulate HMGB1 at 14 d poststroke, along with an accumulation of endogenous EPCs. In vivo siRNA suppression of HMGB1 blocks this EPC response, reduces peri-infact angiogenesis, and worsens neurological deficits. Taken together, these molecular and in vivo findings support a previously undescribed mechanism of crosstalk between reactive astrocytes and EPCs wherein HMGB1 promotes neurovascular remodeling and functional recovery after stroke and brain injury.
Accumulation of impact markers in desert wetlands and implications for the Younger Dryas impact hypothesis
Authors: Pigati Jeffrey S. , Latorre Claudio , Rech Jason A. , Betancourt Julio L. , Martínez Katherine E. , Budahn James R.
Published: April 2012

The Younger Dryas impact hypothesis contends that an extraterrestrial object exploded over North America at 12.9 ka, initiating the Younger Dryas cold event, the extinction of many North American megafauna, and the demise of the Clovis archeological culture. Although the exact nature and location of the proposed impact or explosion remain unclear, alleged evidence for the fallout comes from multiple sites across North America and a site in Belgium. At 6 of the 10 original sites (excluding the Carolina Bays), elevated concentrations of various “impact markers” were found in association with black mats that date to the onset of the Younger Dryas. Black mats are common features in paleowetland deposits and typically represent shallow marsh environments. In this study, we investigated black mats ranging in age from approximately 6 to more than 40 ka in the southwestern United States and the Atacama Desert of northern Chile. At 10 of 13 sites, we found elevated concentrations of iridium in bulk and magnetic sediments, magnetic spherules, and/or titanomagnetite grains within or at the base of black mats, regardless of their age or location, suggesting that elevated concentrations of these markers arise from processes common to wetland systems, and not a catastrophic extraterrestrial impact event.
MicroRNA-200a serves a key role in the decline of progesterone receptor function leading to term and preterm labor
Authors: Williams Koriand’r C. , Renthal Nora E. , Condon Jennifer C. , Gerard Robert D. , Mendelson Carole R.
Published: April 2012

During pregnancy, uterine quiescence is maintained by increased progesterone receptor (PR) activity, but labor is facilitated by a series of events that impair PR function. Previously, we discovered that miR-200 family members serve as progesterone (P
4
)-modulated activators of contraction-associated genes in the pregnant uterus. In this study, we identified a unique role for miR-200a to enhance the local metabolism of P
4
in myometrium and, thus, decrease PR function during the progression toward labor. miR-200a exerts this action by direct repression of STAT5b, a transcriptional repressor of the P
4
-metabolizing enzyme 20α-hydroxysteroid dehydrogenase (20α-HSD). We observed that miR-200a expression increased and STAT5b expression coordinately decreased in myometrium of mice as they progressed to labor and in laboring myometrium from pregnant women. These changes were associated with a dramatic increase in expression and activity of 20α-HSD in laboring myometrium from mouse and human. Notably, overexpression of miR-200a in cultured human myometrial cells (hTERT-HM) suppressed STAT5b and increased 20α-HSD mRNA levels. In uterine tissues of ovariectomized mice injected with P
4
, miR-200 expression was significantly decreased, STAT5b expression was up-regulated, and 20α-HSD mRNA was decreased, but in 15 d postcoitum pregnant mice injected with the PR antagonist RU486, preterm labor was associated with increased miR-200a, decreased STAT5b, and enhanced 20α-HSD expression. Taken together, these findings implicate miR-200a as an important regulator of increased local P
4
metabolism in the pregnant uterus near term and provide insight into the importance of miR-200s in the decline in PR function leading to labor.
Dynamics of unconscious contextual effects in orientation processing
Authors: Mareschal Isabelle , Clifford Colin W. G.
Published: April 2012

Contextual effects abound in the real world; how we perceive an object depends on what surrounds it. A classic example of this is the tilt illusion (TI) whereby the presence of a surround shifts the perceived orientation of a target. Surprisingly, the magnitude and direction of this shift depend on the orientation difference between the target and surround: when their orientations are similar, the perceived difference is amplified and the target appears repelled in orientation from the surround (i.e., the TI). However, when their orientations are close to perpendicular, the difference is decreased and the target appears attracted in orientation toward the surround (i.e., the indirect TI). These misperceptions of orientation have revealed much about the underlying detectors involved in visual processing and how they interact with each other. What remains at stake are the levels of processing involved. To examine this, we designed a reverse-correlation technique whereby observers are blind to the orientation of the surround. We find that the TI and indirect TI occur reliably and over a similar time course, supporting the role of a single mechanism underlying orientation biases that operates in the early stages of visual processing before the conscious extraction of the surround orientation.
Locomotive implication of a Pliocene three-toed horse skeleton from Tibet and its paleo-altimetry significance
Authors: Deng Tao , Li Qiang , Tseng Zhijie Jack , Takeuchi Gary T. , Wang Yang , Xie Guangpu , Wang Shiqi , Hou Sukuan , Wang Xiaoming
Published: April 2012

The Tibetan Plateau is the youngest and highest plateau on Earth, and its elevation reaches one-third of the height of the troposphere, with profound dynamic and thermal effects on atmospheric circulation and climate. The uplift of the Tibetan Plateau was an important factor of global climate change during the late Cenozoic and strongly influenced the development of the Asian monsoon system. However, there have been heated debates about the history and process of Tibetan Plateau uplift, especially the paleo-altimetry in different geological ages. Here we report a well-preserved skeleton of a 4.6 million-y-old three-toed horse (Hipparion zandaense) from the Zanda Basin, southwestern Tibet. Morphological features indicate thatH. zandaensewas a cursorial horse that lived in alpine steppe habitats. Because this open landscape would be situated above the timberline on the steep southern margin of the Tibetan Plateau, the elevation of the Zanda Basin at 4.6 Ma was estimated to be ∼4,000 m above sea level using an adjustment to the paleo-temperature in the middle Pliocene, as well as comparison with modern vegetation vertical zones. Thus, we conclude that the southwestern Tibetan Plateau achieved the present-day elevation in the mid-Pliocene.
Maternal cortisol over the course of pregnancy and subsequent child amygdala and hippocampus volumes and affective problems
Authors: Buss Claudia , Davis Elysia Poggi , Shahbaba Babak , Pruessner Jens C. , Head Kevin , Sandman Curt A.
Published: April 2012

Stress-related variation in the intrauterine milieu may impact brain development and emergent function, with long-term implications in terms of susceptibility for affective disorders. Studies in animals suggest limbic regions in the developing brain are particularly sensitive to exposure to the stress hormone cortisol. However, the nature, magnitude, and time course of these effects have not yet been adequately characterized in humans. A prospective, longitudinal study was conducted in 65 normal, healthy mother–child dyads to examine the association of maternal cortisol in early, mid-, and late gestation with subsequent measures at approximately 7 y age of child amygdala and hippocampus volume and affective problems. After accounting for the effects of potential confounding pre- and postnatal factors, higher maternal cortisol levels in earlier but not later gestation was associated with a larger right amygdala volume in girls (a 1 SD increase in cortisol was associated with a 6.4% increase in right amygdala volume), but not in boys. Moreover, higher maternal cortisol levels in early gestation was associated with more affective problems in girls, and this association was mediated, in part, by amygdala volume. No association between maternal cortisol in pregnancy and child hippocampus volume was observed in either sex. The current findings represent, to the best of our knowledge, the first report linking maternal stress hormone levels in human pregnancy with subsequent child amygdala volume and affect. The results underscore the importance of the intrauterine environment and suggest the origins of neuropsychiatric disorders may have their foundations early in life.
Altered subcellular localization of transcription factor TEAD4 regulates first mammalian cell lineage commitment
Authors: Home Pratik , Saha Biswarup , Ray Soma , Dutta Debasree , Gunewardena Sumedha , Yoo Byunggil , Pal Arindam , Vivian Jay L. , Larson Melissa , Petroff Margaret , Gallagher Patrick G. , Schulz Vincent P. , White Kenneth L. , Golos Thaddeus G. , Behr Barry , Paul Soumen
Published: April 2012

In the preimplantation mouse embryo, TEAD4 is critical to establishing the trophectoderm (TE)-specific transcriptional program and segregating TE from the inner cell mass (ICM). However, TEAD4 is expressed in the TE and the ICM. Thus, differential function of TEAD4 rather than expression itself regulates specification of the first two cell lineages. We used ChIP sequencing to define genomewide TEAD4 target genes and asked how transcription of TEAD4 target genes is specifically maintained in the TE. Our analyses revealed an evolutionarily conserved mechanism, in which lack of nuclear localization of TEAD4 impairs the TE-specific transcriptional program in inner blastomeres, thereby allowing their maturation toward the ICM lineage. Restoration of TEAD4 nuclear localization maintains the TE-specific transcriptional program in the inner blastomeres and prevents segregation of the TE and ICM lineages and blastocyst formation. We propose that altered subcellular localization of TEAD4 in blastomeres dictates first mammalian cell fate specification.
Plant hormone jasmonate prioritizes defense over growth by interfering with gibberellin signaling cascade
Authors: Yang Dong-Lei , Yao Jian , Mei Chuan-Sheng , Tong Xiao-Hong , Zeng Long-Jun , Li Qun , Xiao Lang-Tao , Sun Tai-ping , Li Jigang , Deng Xing-Wang , Lee Chin Mei , Thomashow Michael F. , Yang Yinong , He Zuhua , He Sheng Yang
Published: April 2012

Plants must effectively defend against biotic and abiotic stresses to survive in nature. However, this defense is costly and is often accompanied by significant growth inhibition. How plants coordinate the fluctuating growth-defense dynamics is not well understood and remains a fundamental question. Jasmonate (JA) and gibberellic acid (GA) are important plant hormones that mediate defense and growth, respectively. Binding of bioactive JA or GA ligands to cognate receptors leads to proteasome-dependent degradation of specific transcriptional repressors (the JAZ or DELLA family of proteins), which, at the resting state, represses cognate transcription factors involved in defense (e.g., MYCs) or growth [e.g. phytochrome interacting factors (PIFs)]. In this study, we found that the
coi1
JA receptor mutants of rice (a domesticated monocot crop) and
Arabidopsis
(a model dicot plant) both exhibit hallmark phenotypes of GA-hypersensitive mutants. JA delays GA-mediated DELLA protein degradation, and the
della
mutant is less sensitive to JA for growth inhibition. Overexpression of a selected group of JAZ repressors in
Arabidopsis
plants partially phenocopies GA-associated phenotypes of the
coi1
mutant, and JAZ9 inhibits RGA (a DELLA protein) interaction with transcription factor PIF3. Importantly, the
pif
quadruple (
pifq
) mutant no longer responds to JA-induced growth inhibition, and overexpression of PIF3 could partially overcome JA-induced growth inhibition. Thus, a molecular cascade involving the COI1–JAZ–DELLA–PIF signaling module, by which angiosperm plants prioritize JA-mediated defense over growth, has been elucidated.
Mitochondrial DNA variant associated with Leber hereditary optic neuropathy and high-altitude Tibetans
Authors: Ji Fuyun , Sharpley Mark S. , Derbeneva Olga , Alves Leonardo Scherer , Qian Pin , Wang Yaoli , Chalkia Dimitra , Lvova Maria , Xu Jiancheng , Yao Wei , Simon Mariella , Platt Julia , Xu Shiqin , Angelin Alessia , Davila Antonio , Huang Taosheng , Wang Ping H. , Chuang Lee-Ming , Moore Lorna G. , Qian Guisheng , Wallace Douglas C.
Published: April 2012

The distinction between mild pathogenic mtDNA mutations and population polymorphisms can be ambiguous because both are homoplasmic, alter conserved functions, and correlate with disease. One possible explanation for this ambiguity is that the same variant may have different consequences in different contexts. The NADH dehydrogenase subunit 1 (ND1) nucleotide 3394 T > C (Y30H) variant is such a case. This variant has been associated with Leber hereditary optic neuropathy and it reduces complex I activity and cellular respiration between 7% and 28% on the Asian B4c and F1 haplogroup backgrounds. However, complex I activity between B4c and F1 mtDNAs, which harbor the common 3394T allele, can also differ by 30%. In Asia, the 3394C variant is most commonly associated with the M9 haplogroup, which is rare at low elevations but increases in frequency with elevation to an average of 25% of the Tibetan mtDNAs (odds ratio = 23.7). In high-altitude Tibetan and Indian populations, the 3394C variant occurs on five different macrohaplogroup M haplogroup backgrounds and is enriched on the M9 background in Tibet and the C4a4 background on the Indian Deccan Plateau (odds ratio = 21.9). When present on the M9 background, the 3394C variant is associated with a complex I activity that is equal to or higher than that of the 3394T variant on the B4c and F1 backgrounds. Hence, the 3394C variant can either be deleterious or beneficial depending on its haplogroup and environmental context. Thus, this mtDNA variant fulfills the criteria for a common variant that predisposes to a “complex” disease.
Mind bomb 1
is required for pancreatic β-cell formation
Authors: Horn Signe , Kobberup Sune , Jørgensen Mette C. , Kalisz Mark , Klein Tino , Kageyama Ryoichiro , Gegg Moritz , Lickert Heiko , Lindner Jill , Magnuson Mark A. , Kong Young-Yun , Serup Palle , Ahnfelt-Rønne Jonas , Jensen Jan N.
Published: April 2012

During early pancreatic development, Notch signaling represses differentiation of endocrine cells and promotes proliferation of Nkx6-1
+
Ptf1a
+
multipotent progenitor cells (MPCs). Later, antagonistic interactions between Nkx6 transcription factors and Ptf1a function to segregate MPCs into distal Nkx6-1
−
Ptf1a
+
acinar progenitors and proximal Nkx6-1
+
Ptf1a
−
duct and β-cell progenitors. Distal cells are initially multipotent, but evolve into unipotent, acinar cell progenitors. Conversely, proximal cells are bipotent and give rise to duct cells and late-born endocrine cells, including the insulin producing β-cells. However, signals that regulate proximodistal (P-D) patterning and thus formation of β-cell progenitors are unknown. Here we show that
Mind bomb 1
(
Mib1
) is required for correct P-D patterning of the developing pancreas and β-cell formation. We found that endoderm-specific inactivation of
Mib1
caused a loss of Nkx6-1
+
Ptf1a
−
and Hnf1β
+
cells and a corresponding loss of Neurog3
+
endocrine progenitors and β-cells. An accompanying increase in Nkx6-1
−
Ptf1a
+
and amylase
+
cells, occupying the proximal domain, suggests that proximal cells adopt a distal fate in the absence of Mib1 activity. Impeding Notch-mediated transcriptional activation by conditional expression of dominant negative Mastermind-like 1 (Maml1) resulted in a similarly distorted P-D patterning and suppressed β-cell formation, as did conditional inactivation of the Notch target gene
Hes1
. Our results reveal iterative use of Notch in pancreatic development to ensure correct P-D patterning and adequate β-cell formation.
Dysregulation of dopamine receptor D2 as a sensitive measure for Huntington disease pathology in model mice
Authors: Crook Zachary R. , Housman David E.
Published: April 2012

The ability to quantitatively evaluate the impact of a potential therapeutic intervention for Huntington disease (HD) in animal models for the disease is a critical step in the pathway to development of an effective therapy for this devastating neurodegenerative disorder. We report here an approach that combines a cell-based assay’s quantitative accuracy and direct relationship to molecular processes with the ability to directly monitor effects in HD model mouse neurons. To accomplish this goal, we have developed an accurate quantitative reporter assay for a transcript known to be down-regulated as an early consequence of mutant
huntingtin
expression. This system uses mouse strains carrying a GFP reporter for the expression of the dopamine receptor D2, expressed in the medium spiny neurons of the basal ganglion. This receptor consistently demonstrates reduced expression in patients and murine models, and the FACS-based assay gives a highly accurate and quantitative readout of this pathology in mouse neurons expressing mutant
huntingtin
. For four genetic models and one viral model, a highly reproducible time course of loss of reporter expression is observed. This quantitative measure of HD pathology can be used to measure the effects of HD therapeutics in small cohorts with high confidence. We further demonstrate that the introduction of an shRNA against the
huntingtin
transgene by virus can improve this pathological status in medium spiny neurons transduced with the construct. We believe this system can be of great utility in the validation of effective therapeutic interventions for HD.
‘Weeping tears of blood’: exploring Italian soldiers' emotions in the First World War
Authors: Wilcox Vanda
Published: April 2012

Emotion plays a vital role in any rounded history of warfare, both as an element in morale and as component in understanding the soldier's experience. Theories on the functioning of emotions vary, but an exploration of Italian soldiers' emotions during the First World War highlights both cognitive and cultural elements in the ways emotions were experienced and expressed. Although Italian stereotypes of passivity and resignation dominated contemporary discourse concerning the feelings and reactions of peasant conscripts, letters reveal that Italian soldiers vividly expressed a wide range of intense emotions. Focusing on fear, horror and grief as recurrent themes, this article finds that these emotions were processed and expressed in ways which show similarities to the combatants of other nations but which also display distinctly Italian features. The language and imagery commonly deployed offer insights into the ways in which Italian socio-cultural norms shaped expressions of personal war experience. In letters that drew on both religious imagery and the traditional peasant concerns of land, terrain and basic survival, soldiers expressed their fears of death, isolation, suffering and killing in surprisingly vigorous terms.