bluuebunny/crossref_metadata_2025 huggingface dataset:
Very rapid geomagnetic field change recorded by the partial remagnetization of a lava flow
Authors: Bogue Scott W. , Glen Jonathan M. G.
Published: November 2010

A new paleomagnetic result from a lava flow with a distinctive, two‐part remanence reinforces the controversial hypothesis that geomagnetic change during a polarity reversal can be much faster than normal. The 3.9‐m‐thick lava (“Flow 20”) is exposed in the Sheep Creek Range (north central Nevada) and was erupted during a reverse‐to‐normal (R‐N) geomagnetic polarity switch at 15.6 Ma. Flow 20 began to acquire a primary thermoremanence while the field was pointing east and down but was soon buried, reheated, and partially‐remagnetized in a north‐down direction by the 8.2‐m‐thick flow that succeeded it. A simple conductive cooling calculation shows that the observed remagnetization could not have occurred unless Flow 20 was still warm (about 150°C near its base) when buried and that the 53° change from east‐down to north‐down field occurred at an average rate of approximately 1°/week, several orders of magnitude faster than typical of secular variation.
Resonance and impact of the 2009 Samoa tsunami around Tutuila, American Samoa
Authors: Roeber Volker , Yamazaki Yoshiki , Cheung Kwok Fai
Published: November 2010

The 2009 Samoa tsunami resulted in severe damage and inundation at Tutuila, American Samoa. The disparity of the impact and the varying accounts of the tsunami along the coast remain one of the most intriguing aspects of the event. We utilize a dispersive wave model to reconstruct the tsunami from the earthquake source for understanding of the wave dynamics around Tutuila. After validation with water‐level measurements, a Fast Fourier Transform of the computed surface elevation reveals coupled resonance oscillations between 3 and 18 min period over the insular slope and shelf as well as the fringing reefs. The resonance, which focuses energy according to shelf and embayment configurations, provides an explanation of the runup data and eyewitness accounts and identifies the coastal communities prone to tsunami hazards.
Improving global mass flux solutions from Gravity Recovery and Climate Experiment (GRACE) through forward modeling and continuous time correlation
Authors: Sabaka T. J. , Rowlands D. D. , Luthcke S. B. , Boy J.‐P.
Published: November 2010

We describe Earth's mass flux from April 2003 through November 2008 by deriving a time series of mascons on a global 2° × 2° equal‐area grid at 10 day intervals. We estimate the mass flux directly from K band range rate (KBRR) data provided by the Gravity Recovery and Climate Experiment (GRACE) mission. Using regularized least squares, we take into account the underlying process dynamics through continuous space and time‐correlated constraints. In addition, we place the mascon approach in the context of other filtering techniques, showing its equivalence to anisotropic, nonsymmetric filtering, least squares collocation, and Kalman smoothing. We produce mascon time series from KBRR data that have and have not been corrected (forward modeled) for hydrological processes and find that the former produce superior results in oceanic areas by minimizing signal leakage from strong sources on land. By exploiting the structure of the spatiotemporal constraints, we are able to use a much more efficient (in storage and computation) inversion algorithm based upon the conjugate gradient method. This allows us to apply continuous rather than piecewise continuous time‐correlated constraints, which we show via global maps and comparisons with ocean‐bottom pressure gauges, to produce time series with reduced random variance and full systematic signal. Finally, we present a preferred global model, a hybrid whose oceanic portions are derived using forward modeling of hydrology but whose land portions are not, and thus represent a pure GRACE‐derived signal.
Geometry‐specified troposphere decorrelation for subcentimeter real‐time kinematic solutions over long baselines
Authors: Li Bofeng , Feng Yanming , Shen Yunzhong , Wang Charles
Published: November 2010

Real‐time kinematic (RTK) GPS techniques have been extensively developed for applications including surveying, structural monitoring, and machine automation. Limitations of the existing RTK techniques that hinder their applications for geodynamics purposes are twofold: (1) the achievable RTK accuracy is on the level of a few centimeters and the uncertainty of vertical component is 1.5–2 times worse than those of horizontal components and (2) the RTK position uncertainty grows in proportional to the base‐to‐rover distances. The key limiting factor behind the problems is the significant effect of residual tropospheric errors on the positioning solutions, especially on the highly correlated height component. This paper develops the geometry‐specified troposphere decorrelation strategy to achieve the subcentimeter kinematic positioning accuracy in all three components. The key is to set up a relative zenith tropospheric delay (RZTD) parameter to absorb the residual tropospheric effects and to solve the established model as an ill‐posed problem using the regularization method. In order to compute a reasonable regularization parameter to obtain an optimal regularized solution, the covariance matrix of positional parameters estimated without the RZTD parameter, which is characterized by observation geometry, is used to replace the quadratic matrix of their “true” values. As a result, the regularization parameter is adaptively computed with variation of observation geometry. The experiment results show that new method can efficiently alleviate the model's ill condition and stabilize the solution from a single data epoch. Compared to the results from the conventional least squares method, the new method can improve the long‐range RTK solution precision from several centimeters to the subcentimeter in all components. More significantly, the precision of the height component is even higher. Several geosciences applications that require subcentimeter real‐time solutions can largely benefit from the proposed approach, such as monitoring of earthquakes and large dams in real‐time, high‐precision GPS leveling and refinement of the vertical datum. In addition, the high‐resolution RZTD solutions can contribute to effective recovery of tropospheric slant path delays in order to establish a 4‐D troposphere tomography.
Simulation of topographic effects on seismic waves from shallow explosions near the North Korean nuclear test site with emphasis on shear wave generation
Authors: Rodgers Arthur J. , Petersson N. Anders , Sjogreen Bjorn
Published: November 2010

We performed high‐resolution (8 Hz) three‐dimensional simulations of ground motions from shallow explosions in the presence of rough surface topography near the North Korean nuclear test site to study elastic propagation effects with emphasis on theoretical aspects of shear wave generation. Interaction with rough topography causes significant P‐to‐Rg scattering along the surface with amplification of high‐frequency (2–8 Hz) shear waves relative to the flat Earth case. Shear waves of different polarizations are coupled by topographic scattering. Rg precursors composed of P‐to‐Rg conversions traveling as surface waves have the spectral amplitudes comparable to the P wave, while the Rg phase has the low‐frequency (0.5–3 Hz) spectral shape of the Rg from the flat case plus the high‐frequency (3–8 Hz) P wave spectra. Motions at near‐vertical takeoff angles corresponding to teleseismic propagation are increased or decreased indicating that waves are focused or defocused by topographic features above the source. Topographic roughness has a dramatic effect as short‐wavelength features (<2–5 km) are included. Higher frequencies are amplified by topography, including frequencies corresponding to wavelengths shorter than the shortest topographic scale length. Overall topography enhances energy propagating along the surface near the source, amplifies surface waves, and tends to balance SV‐ and SH‐polarized motions, all of which impact shear wave observations used for nuclear explosion monitoring. Further simulation studies could elucidate how the wavefield emerging from a topographically rough area ultimately propagates to regional and/or teleseismic distances.
Examining the influence of spring soil moisture anomalies on summer precipitation in the U.S. Great Plains using the Community Atmosphere Model version 3
Authors: Meng Lei , Quiring Steven M.
Published: November 2010

The influence of spring soil moisture anomalies on summer precipitation variations in the U.S. Great Plains was investigated using the coupled version of the Community Atmosphere Model version 3‐Community Land Model version 3. A series of experiments were conducted to examine how spring soil moisture anomalies influence summer precipitation. Results demonstrate that there are significant differences in precipitation response depending on the timing, sign, and magnitude of the spring soil moisture anomalies. Timing is the most important factor that controls the soil moisture‐precipitation interaction. Soil moisture anomalies imposed on 1 May and 1 June tend to have significant influences on summer precipitation, depending on the sign of the soil moisture anomalies. Dry soil moisture anomalies tend to affect subsequent precipitation for longer than wet soil moisture anomalies when initialized on 1 May. Wet soil moisture anomalies can have more immediate and larger impacts on summer precipitation when they are imposed on 1 June. April soil moisture anomalies do not have a statistically significant impact on summer precipitation. The precipitation response is stronger as the magnitude of the soil moisture anomalies increases. Significant differences in the temporal variations of soil moisture exist not only between dry and wet experiments but also among the 10 soil layers. Generally the near‐surface layers respond much more rapidly than the deep soil layers. Further study is needed to determine whether these findings are model specific.
Mach reflection in a warm dense plasma
Authors: Foster J. M. , Rosen P. A. , Wilde B. H. , Hartigan P. , Perry T. S.
Published: November 2010

The phenomenon of irregular shock-wave reflection is of importance in high-temperature gas dynamics, astrophysics, inertial-confinement fusion, and related fields of high-energy-density science. However, most experimental studies of irregular reflection have used supersonic wind tunnels or shock tubes, and few or no data are available for Mach reflection phenomena in the plasma regime. Similarly, analytic studies have often been confined to calorically perfect gases. We report the first direct observation, and numerical modeling, of Mach stem formation for a warm, dense plasma. Two ablatively driven aluminum disks launch oppositely directed, near-spherical shock waves into a cylindrical plastic block. The interaction of these shocks results in the formation of a Mach-ring shock that is diagnosed by x-ray backlighting. The data are modeled using radiation hydrocodes developed by AWE and LANL. The experiments were carried out at the University of Rochester’s Omega laser [J. M. Soures, R. L. McCrory, C. P. Verdon et al., Phys. Plasmas 3, 2108 (1996)] and were inspired by modeling [A. M. Khokhlov, P. A. Höflich, E. S. Oran et al., Astrophys J. 524, L107 (1999)] of core-collapse supernovae that suggest that in asymmetric supernova explosion significant mass may be ejected in a Mach-ring formation launched by bipolar jets.
Numerical study of the ablative Richtmyer–Meshkov instability of laser-irradiated deuterium and deuterium-tritium targets
Authors: Marocchino Alberto , Atzeni Stefano , Schiavi Angelo
Published: November 2010

The Richtmyer–Meshkov instability (RMI) at the ablation front of laser-irradiated planar targets is investigated by two-dimensional numerical hydrodynamics simulations. The linear evolution of perturbations seeded either by surface roughness or target inhomogeneity is studied for perturbation wavelengths in the range 10≤λ≤400 μm and laser intensity 4×1012≤I≤4×1014 W/cm2 (with laser wavelength λlaser=0.35 μm). Thin and thick cryogenic deuterium or deuterium-tritium (DT) planar targets are considered. For targets irradiated at constant intensity, it is found that perturbations with wavelength below a given threshold perform damped oscillations, while perturbations above such a threshold are unstable and oscillate with growing amplitude. This is qualitatively in agreement with theoretical predictions by Goncharov et al. [Phys. Plasmas 13, 012702 (2006)], according to which ablation related processes stabilize perturbations with kDc⪢1, where Dc is the distance between the ablation front and critical density for laser propagation. For kDc<1 a weakly growing Landau–Darrieus instability (LDI) is instead excited. The stability threshold increases substantially with laser intensity, given the dependence of Dc on laser intensity I (roughly Dc∝I, according to the present simulations). Direct-drive laser fusion targets are irradiated by time-shaped pulses, with a low intensity initial foot. In this case, perturbations with wavelengths below some threshold (about 10 μm, for typical ignition-class all-DT targets) are damped after an initial growth. In a thin target, initial perturbations, either damped or amplified by RMI and LDI, seed the subsequent Rayleigh–Taylor instability. Finally, it is shown that RMI growth of fusion targets can be reduced by using laser pulses including an initial adiabat-shaping picket (originally proposed to reduce the growth of Rayleigh–Taylor instability).
Control of surface adatom kinetics for the growth of high-indium content InGaN throughout the miscibility gap
Authors: Moseley Michael , Lowder Jonathan , Billingsley Daniel , Doolittle W. Alan
Published: November 2010

The surface kinetics of InGaN alloys grown via metal-modulated epitaxy (MME) are explored in combination with transient reflection high-energy electron diffraction intensities. A method for monitoring and controlling indium segregation in situ is demonstrated. It is found that indium segregation is more accurately associated with the quantity of excess adsorbed metal, rather than the metal-rich growth regime in general. A modified form of MME is developed in which the excess metal dose is managed via shuttered growth, and high-quality InGaN films throughout the miscibility gap are grown.
Experimental evidence of multimaterial jet formation with lasers
Authors: Nicolaï Ph. , Stenz C. , Tikhonchuk V. , Kasperczuk A. , Pisarczyk T. , Juha L. , Krousky E. , Masek K. , Pfeifer M. , Rohlena K. , Skala J. , Kmetik V. , Ullschmied J. , Kalal M. , Klir D. , Kravarik J. , Kubes P. , Rezac K. , Pisarczyk P. , Tabakhoff E.
Published: November 2010

Laser-produced multimaterial jets have been investigated at the Prague Asterix Laser System laser [K. Jungwirth et al., Phys. Plasmas 8, 2495 (2001)]. The method of jet production is based on the laser-plasma ablation process and proved to be easy to set up and robust. The possibility of multimaterial laboratory jet production is demonstrated and complex hydrodynamic flows in the jet body are obtained. Two complementary diagnostics in the optical ray and x-ray ranges provide detailed information about jet characteristics. The latter are in agreement with estimates and two-dimensional radiation hydrodynamic simulation results. The experiment provides a proof of principle that a velocity field could be produced and controlled in the jet body. It opens a possibility of astrophysical jet structure modeling in laboratory.
Switching mechanism of polarization vortex in single-crystal ferroelectric nanodots
Authors: Wang Jie
Published: November 2010

The polarization switching in a single-crystal ferroelectric tetragonal nanodot subjected to curled electric fields is investigated by a phase field model. The simulation results show that the switching of polarization vortex in the tetragonal nanodot does not begin from the location with the highest energy density, which is different from those of ferroelectric nanotubes and ferroelectric cylindrical nanodots. It is found that the vortex switching begins from the dot corners with the lowest elastic energy density, which implies that the elastic constraint as well as the geometry play an important role on the switching of polarization vortex in ferroelectric nanostructures.
At the crossroads of vaginal health and disease, the genome sequence of
Lactobacillus iners
AB-1
Authors: Macklaim Jean M. , Gloor Gregory B. , Anukam Kingsley C. , Cribby Sarah , Reid Gregor
Published: November 2010

Lactobacilli have long been regarded as important constituents of the healthy human vagina.
Lactobacillus iners
is the most frequently detected bacterial species in the vagina, but little is known about its characteristics. We report a description of the whole-genome sequence of
L. iners
AB-1 along with comparative analysis of published genomes of closely related strains of lactobacilli. The genome is the smallest
Lactobacillus
reported to date, with a 1.3-Mbp single chromosome. The genome seems to have undergone one or more rapid evolution events that resulted in large-scale gene loss and horizontal acquisition of a number of genes for survival in the vagina.
L. iners
may exhibit specialized adaptation mechanisms to the vaginal environment, such as an iron–sulfur cluster assembly system, and several unique σ factors to regulate gene transcription in this fluctuating environment. A potentially highly expressed homolog of a cholesterol-binding lysin may also contribute to host cell adhesion or act as a defense mechanism against other microbes. Notably, there is a lack of apparent adhesion proteins, but several cell-anchor proteins were identified and may be important for interaction with the host mucosal tissues.
L. iners
is widely present in healthy females as well as those suffering from bacterial vaginosis or who have undergone antimicrobial therapy, suggesting that it is an important indigenous species of the vagina.
Generation of trisomies in cancer cells by multipolar mitosis and incomplete cytokinesis
Authors: Gisselsson David , Jin Yuesheng , Lindgren David , Persson Johan , Gisselsson Lennart , Hanks Sandra , Sehic Daniel , Mengelbier Linda Holmquist , Øra Ingrid , Rahman Nazneen , Mertens Fredrik , Mitelman Felix , Mandahl Nils
Published: November 2010

One extra chromosome copy (i.e., trisomy) is the most common type of chromosome aberration in cancer cells. The mechanisms behind the generation of trisomies in tumor cells are largely unknown, although it has been suggested that dysfunction of the spindle assembly checkpoint (SAC) leads to an accumulation of trisomies through failure to correctly segregate sister chromatids in successive cell divisions. By using Wilms tumor as a model for cancers with trisomies, we now show that trisomic cells can form even in the presence of a functional SAC through tripolar cell divisions in which sister chromatid separation proceeds in a regular fashion, but cytokinesis failure nevertheless leads to an asymmetrical segregation of chromosomes into two daughter cells. A model for the generation of trisomies by such asymmetrical cell division accurately predicted several features of clones having extra chromosomes in vivo, including the ratio between trisomies and tetrasomies and the observation that different trisomies found in the same tumor occupy identical proportions of cells and colocalize in tumor tissue. Our findings provide an experimentally validated model explaining how multiple trisomies can occur in tumor cells that still maintain accurate sister chromatid separation at metaphase–anaphase transition and thereby physiologically satisfy the SAC.
Building multifunctionality into a complex containing master regulators of hematopoiesis
Authors: Fujiwara Tohru , Lee Hsiang-Ying , Sanalkumar Rajendran , Bresnick Emery H.
Published: November 2010

Developmental control mechanisms often use multimeric complexes containing transcription factors, coregulators, and additional non-DNA binding components. It is challenging to ascertain how such components contribute to complex function at endogenous loci. We analyzed the function of components of a complex containing master regulators of hematopoiesis (GATA-1 and Scl/TAL1) and the non-DNA binding components ETO2, the LIM domain protein LMO2, and the chromatin looping factor LDB1. Surprisingly, we discovered that ETO2 and LMO2 regulate distinct target-gene ensembles in erythroid cells. ETO2 commonly repressed GATA-1 function via suppressing histone H3 acetylation, although it also regulated methylation of histone H3 at lysine 27 at select loci. Prior studies defined multiple modes by which GATA-1 regulates target genes with or without the coregulator Friend of GATA-1 (FOG-1). LMO2 selectively repressed genes that GATA-1 represses in a FOG-1–independent manner. As LMO2 controls hematopoiesis, its dysregulation is leukemogenic, and its influence on GATA factor function is unknown, this mechanistic link has important biological and pathophysiological implications. The demonstration that ETO2 and LMO2 exert qualitatively distinct functions at endogenous loci illustrates how components of complexes containing master developmental regulators can impart the capacity to regulate unique cohorts of target genes, thereby diversifying complex function.
Stem cell-like micro-RNA signature driven by Myc in aggressive liver cancer
Authors: Cairo Stefano , Wang Yipeng , de Reyniès Aurélien , Duroure Karine , Dahan Jennifer , Redon Marie-José , Fabre Monique , McClelland Michael , Wang Xin W. , Croce Carlo M. , Buendia Marie-Annick
Published: November 2010

Myc activation has been implicated in the pathogenesis of hepatoblastoma (HB), a rare embryonal neoplasm derived from liver progenitor cells. Here, microRNA (miR) expression profiling of 65 HBs evidenced differential patterns related to developmental stage and Myc activity. Undifferentiated aggressive HBs overexpressed the miR-371–3 cluster with concomitant down-regulation of the miR-100/let-7a-2/miR-125b-1 cluster, evoking an ES cell expression profile. ChIP and Myc inhibition assays in hepatoma cells demonstrated that both miR clusters are regulated by Myc in an opposite manner. We show that the two miR clusters exert antagonistic effects on cell proliferation and tumorigenicity. Moreover, their combined deregulation cooperated in modulating the hepatic tumor phenotype, implicating stem cell-like regulation of Myc-dependent miRs in poorly differentiated HBs. Importantly, a four-miR signature representative of these clusters efficiently stratified HB patients, and when applied to 241 hepatocellular carcinomas (HCCs), it identified invasive tumors with a poor prognosis. Our data argue that Myc-driven reprogramming of miR expression patterns contributes to the aggressive phenotype of liver tumors originating from hepatic progenitor cells.
Transcriptional coactivator PGC-1α promotes peroxisomal remodeling and biogenesis
Authors: Bagattin Alessia , Hugendubler Lynne , Mueller Elisabetta
Published: November 2010

Mitochondria and peroxisomes execute some analogous, nonredundant functions including fatty acid oxidation and detoxification of reactive oxygen species, and, in response to select metabolic cues, undergo rapid remodeling and division. Although these organelles share some components of their division machinery, it is not known whether a common regulator coordinates their remodeling and biogenesis. Here we show that in response to thermogenic stimuli, peroxisomes in brown fat tissue (BAT) undergo selective remodeling and expand in number and demonstrate that ectopic expression of the transcriptional coactivator PGC-1α recapitulates these effects on the peroxisomal compartment, both in vitro and in vivo. Conversely, β-adrenergic stimulation of PGC-1α
−/−
cells results in blunted induction of peroxisomal gene expression. Surprisingly, PPARα was not required for the induction of critical biogenesis factors, suggesting that PGC-1α orchestrates peroxisomal remodeling through a PPARα-independent mechanism. Our data suggest that PGC-1α is critical to peroxisomal physiology, establishing a role for this factor as a fundamental orchestrator of cellular adaptation to energy demands.
Lymph node cortical sinus organization and relationship to lymphocyte egress dynamics and antigen exposure
Authors: Grigorova Irina L. , Panteleev Mikhail , Cyster Jason G.
Published: November 2010

Recent studies have identified cortical sinuses as sites of sphingosine-1-phosphate receptor-1 (S1P
1
)-dependent T- and B-cell egress from the lymph node (LN) parenchyma. However, the distribution of cortical sinuses in the entire LN and the extent of lymph flow within them has been unclear. Using 3D reconstruction and intravital two-photon microscopy we describe the branched organization of the cortical sinus network within the inguinal LN and show that lymphocyte flow begins within blunt-ended sinuses. Many cortical sinuses are situated adjacent to high endothelial venules, and some lymphocytes access these sinuses within minutes of entering a LN. However, upon entry to inflamed LNs, lymphocytes rapidly up-regulate CD69 and are prevented from accessing cortical sinuses. Using the LN reconstruction data and knowledge of lymphocyte migration and cortical sinus entry dynamics, we developed a mathematical model of T-cell egress from LNs. The model suggests that random walk encounters with lymphatic sinuses are the major factor contributing to LN transit times. A slight discrepancy between predictions of the model and the measured transit times may be explained by lymphocytes undergoing a few rounds of migration between the parenchyma and sinuses before departing from the LN. Because large soluble antigens gain rapid access to cortical sinuses, such parenchyma–sinus shuttling may facilitate antibody responses.
Climatic warming disrupts recurrent Alpine insect outbreaks
Authors: Johnson Derek M. , Büntgen Ulf , Frank David C. , Kausrud Kyrre , Haynes Kyle J. , Liebhold Andrew M. , Esper Jan , Stenseth Nils Chr.
Published: November 2010

Climate change has been identified as a causal factor for diverse ecological changes worldwide. Warming trends over the last couple of decades have coincided with the collapse of long-term population cycles in a broad range of taxa, although causal mechanisms are not well-understood. Larch budmoth (LBM) population dynamics across the European Alps, a classic example of regular outbreaks, inexplicably changed sometime during the 1980s after 1,200 y of nearly uninterrupted periodic outbreak cycles. Herein, analysis of perhaps the most extensive spatiotemporal dataset of population dynamics and reconstructed Alpine-wide LBM defoliation records reveals elevational shifts in LBM outbreak epicenters that coincide with temperature fluctuations over two centuries. A population model supports the hypothesis that temperature-mediated shifting of the optimal elevation for LBM population growth is the mechanism for elevational epicenter changes. Increases in the optimal elevation for population growth over the warming period of the last century to near the distributional limit of host larch likely dampened population cycles, thereby causing the collapse of a millennium-long outbreak cycle. The threshold-like change in LBM outbreak pattern highlights how interacting species with differential response rates to climate change can result in dramatic ecological changes.
Structural basis of oligomerization in septin-like GTPase of immunity-associated protein 2 (GIMAP2)
Authors: Schwefel David , Fröhlich Chris , Eichhorst Jenny , Wiesner Burkhard , Behlke Joachim , Aravind L. , Daumke Oliver
Published: November 2010

GTPases of immunity-associated proteins (GIMAPs) are a distinctive family of GTPases, which control apoptosis in lymphocytes and play a central role in lymphocyte maturation and lymphocyte-associated diseases. To explore their function and mechanism, we determined crystal structures of a representative member, GIMAP2, in different nucleotide-loading and oligomerization states. Nucleotide-free and GDP-bound GIMAP2 were monomeric and revealed a guanine nucleotide-binding domain of the TRAFAC (translation factor associated) class with a unique amphipathic helix α7 packing against switch II. In the absence of α7 and the presence of GTP, GIMAP2 oligomerized via two distinct interfaces in the crystal. GTP-induced stabilization of switch I mediates dimerization across the nucleotide-binding site, which also involves the GIMAP specificity motif and the nucleotide base. Structural rearrangements in switch II appear to induce the release of α7 allowing oligomerization to proceed via a second interface. The unique architecture of the linear oligomer was confirmed by mutagenesis. Furthermore, we showed a function for the GIMAP2 oligomer at the surface of lipid droplets. Although earlier studies indicated that GIMAPs are related to the septins, the current structure also revealed a strikingly similar nucleotide coordination and dimerization mode as in the dynamin GTPase. Based on this, we reexamined the relationships of the septin- and dynamin-like GTPases and demonstrate that these are likely to have emerged from a common membrane-associated dimerizing ancestor. This ancestral property appears to be critical for the role of GIMAPs as nucleotide-regulated scaffolds on intracellular membranes.
Schistosomamansonitriggers Dectin-2, which activates the Nlrp3 inflammasome and alters adaptive immune responses
Authors: Ritter Manuel , Gross Olaf , Kays Sarah , Ruland Jürgen , Nimmerjahn Falk , Saijo Shinobu , Tschopp Jürg , Layland Laura E. , Prazeres da Costa Clarissa
Published: November 2010

The propensity of helminths, such as schistosomes, to immunomodulate the host's immune system is an essential aspect of their survival. Previous research has demonstrated how soluble schistosomal egg antigens (SEA) dampen TLR-signaling during innate immune responses. We show here that the suppressive effect by SEA on TLR signaling is simultaneously coupled to the activation of the Nlrp3 (NLR family, pyrin domain containing 3) inflammasome and thus IL-1β production. Therefore, the responsible protein component of SEA contains the second signal that is required to trigger proteolytic pro-IL-1β processing. Moreover, the SEA component binds to the Dectin-2/FcRγ (Fc receptor γ chain) complex and activates the Syk kinase signaling pathway to induce reactive oxygen species and potassium efflux. As IL-1β has been shown to be an essential orchestrator against several pathogens we studied the in vivo consequences ofSchistosoma mansoniinfection in mice deficient in the central inflammasome adapter ASC and Nlrp3 molecule. These mice failed to induce local IL-1β levels in the liver and showed decreased immunopathology. Interestingly, antigen-specific Th1, Th2, and Th17 responses were down-regulated. Overall, these data imply that component(s) within SEA induce IL-1β production and unravel a crucial role of Nlrp3 duringS.mansoniinfection.
Bisphenol A impairs the double-strand break repair machinery in the germline and causes chromosome abnormalities
Authors: Allard Patrick , Colaiácovo Monica P.
Published: November 2010

Bisphenol A (BPA) is a highly prevalent constituent of plastics that has been associated with diabetes, cardiovascular disease, and an increased risk of miscarriages in humans. In mice, BPA exposure disrupts the process of meiosis; however, analysis of the affected molecular pathways is lagging and has been particularly challenging. Here we show that exposure of the nematode
Caenorhabditis elegans
to BPA, at internal concentrations consistent with mammalian models, causes increased sterility and embryonic lethality. BPA exposure results in impaired chromosome synapsis and disruption of meiotic double-strand break repair (DSBR) progression. BPA carries an anti-estrogenic activity in the germline and results in germline-specific down-regulation of DSBR genes, thereby impairing maintenance of genomic integrity during meiosis.
C. elegans
therefore constitutes a model of remarkable relevance to mammals with which to assess how our chemical landscape affects germ cells and meiosis.
Separate value comparison and learning mechanisms in macaque medial and lateral orbitofrontal cortex
Authors: Noonan M. P. , Walton M. E. , Behrens T. E. J. , Sallet J. , Buckley M. J. , Rushworth M. F. S.
Published: November 2010

Uncertainty about the function of orbitofrontal cortex (OFC) in guiding decision-making may be a result of its medial (mOFC) and lateral (lOFC) divisions having distinct functions. Here we test the hypothesis that the mOFC is more concerned with reward-guided decision making, in contrast with the lOFC's role in reward-guided learning. Macaques performed three-armed bandit tasks and the effects of selective mOFC lesions were contrasted against lOFC lesions. First, we present analyses that make it possible to measure reward-credit assignment—a crucial component of reward-value learning—independently of the decisions animals make. The mOFC lesions do not lead to impairments in reward-credit assignment that are seen after lOFC lesions. Second, we examined how the reward values of choice options were compared. We present three analyses, one of which examines reward-guided decision making independently of reward-value learning. Lesions of the mOFC, but not the lOFC, disrupted reward-guided decision making. Impairments after mOFC lesions were a function of the multiple option contexts in which decisions were made. Contrary to axiomatic assumptions of decision theory, the mOFC-lesioned animals’ value comparisons were no longer independent of irrelevant alternatives.
Reversal of preexisting hyperglycemia in diabetic mice by acute deletion of the
Men1
gene
Authors: Yang Yuqing , Gurung Buddha , Wu Ting , Wang Haoren , Stoffers Doris A. , Hua Xianxin
Published: November 2010

A hallmark of diabetes is an absolute or relative reduction in the number of functional β cells. Therapies that could increase the number of endogenous β cells under diabetic conditions would be desirable. Prevalent gene targeting mouse models for assessing β-cell proliferation and diabetes pathogenesis only address whether deletion of a gene prevents the development of diabetes. Models testing whether acute excision of a single gene can ameliorate or reverse preexisting hyperglycemia in established diabetes remain to be explored, which could directly validate the effect of gene excision on treating diabetes. Here, we report that acute and temporally controlled excision of the
Men1
gene, which encodes menin, ameliorated preexisting hyperglycemia in streptozotocin-treated mice. Moreover,
Men1
excision also improved the preexisting hyperglycemia and glucose intolerance in genetic
db/db
diabetic mice. Furthermore, acute
Men1
excision reversed preexisting glucose intolerance in high-fat diet-fed mice.
Men1
excision improved glucose metabolism at least partly through increasing proliferation of endogenous β cells and islet size. Acute
Men1
excision up-regulated a group of proproliferative genes in pancreatic islets. Together, these findings demonstrate that established hyperglycemia can be reversed through repression of a single gene,
Men1
, in diabetic conditions, and suggest that menin is a vital regulator in pathogenesis of diabetes.
Inversin relays Frizzled-8 signals to promote proximal pronephros development
Authors: Lienkamp Soeren , Ganner Athina , Boehlke Christopher , Schmidt Thorsten , Arnold Sebastian J. , Schäfer Tobias , Romaker Daniel , Schuler Julia , Hoff Sylvia , Powelske Christian , Eifler Annekathrin , Krönig Corinna , Bullerkotte Axel , Nitschke Roland , Kuehn E. Wolfgang , Kim Emily , Burkhardt Hans , Brox Thomas , Ronneberger Olaf , Gloy Joachim , Walz Gerd
Published: November 2010

Mutations ofinversincause type II nephronophthisis, an infantile autosomal recessive disease characterized by cystic kidney disease and developmental defects. Inversin regulates Wnt signaling and is required for convergent extension movements during early embryogenesis. We now show that Inversin is essential forXenopuspronephros formation, involving two distinct and opposing forms of cell movements. Knockdown of Inversin abrogated both proximal pronephros extension and distal tubule differentiation, phenotypes similar to that ofXenopusdeficient in Frizzled-8. Exogenous Inversin rescued the pronephric defects caused by lack of Frizzled-8, indicating that Inversin acts downstream of Frizzled-8 in pronephros morphogenesis. Depletion of Inversin prevents the recruitment of Dishevelled in response to Frizzled-8 and impeded the accumulation of Dishevelled at the apical membrane of tubular epithelial cells in vivo. Thus, defective tubule morphogenesis seems to contribute to the renal pathology observed in patients with nephronophthisis type II.
Force-induced formation and propagation of adhesion nanodomains in living fungal cells
Authors: Alsteens David , Garcia Melissa C. , Lipke Peter N. , Dufrêne Yves F.
Published: November 2010

Understanding how cell adhesion proteins form adhesion domains is a key challenge in cell biology. Here, we use single-molecule atomic force microscopy (AFM) to demonstrate the force-induced formation and propagation of adhesion nanodomains in living fungal cells, focusing on the covalently anchored cell-wall protein Als5p from
Candida albicans
. We show that pulling on single adhesins with AFM tips terminated with specific antibodies triggers the formation of adhesion domains of 100–500 nm and that the force-induced nanodomains propagate over the entire cell surface. Control experiments (with cells lacking Als5p, single-site mutation in the protein, bare tips, and tips modified with irrelevant antibodies) demonstrate that Als5p nanodomains result from protein redistribution triggered by force-induced conformational changes in the initially probed proteins, rather than from nonspecific cell-wall perturbations. Als5p remodeling is independent of cellular metabolic activity because heat-killed cells show the same behavior as live cells. Using AFM and fluorescence microscopy, we also find that nanodomains are formed within ∼30 min and migrate at a speed of ∼20 nm·min
−1
, indicating that domain formation and propagation are slow, time-dependent processes. These results demonstrate that mechanical stimuli can trigger adhesion nanodomains in fungal cells and suggest that the force-induced clustering of adhesins may be a mechanism for activating cell adhesion.
Specialization and evolutionary branching within migratory populations
Authors: Torney Colin J. , Levin Simon A. , Couzin Iain D.
Published: November 2010

Understanding the mechanisms that drive specialization and speciation within initially homogeneous populations is a fundamental challenge for evolutionary theory. It is an issue of relevance for significant open questions in biology concerning the generation and maintenance of biodiversity, the origins of reciprocal cooperation, and the efficient division of labor in social or colonial organisms. Several mathematical frameworks have been developed to address this question and models based on evolutionary game theory or the adaptive dynamics of phenotypic mutation have demonstrated the emergence of polymorphic, specialized populations. Here we focus on a ubiquitous biological phenomenon, migration. Individuals in our model may evolve the capacity to detect and follow an environmental cue that indicates a preferred migration route. The strategy space is defined by the level of investment in acquiring personal information about this route or the alternative tendency to follow the direction choice of others. The result is a relation between the migratory process and a game theoretic dynamic that is generally applicable to situations where information may be considered a public good. Through the use of an approximation of social interactions, we demonstrate the emergence of a stable, polymorphic population consisting of an uninformed subpopulation that is dependent upon a specialized group of leaders. The branching process is classified using the techniques of adaptive dynamics.
Automatic analysis of syntactic complexity in second language writing
Authors: Lu Xiaofei
Published: November 2010

We describe a computational system for automatic analysis of syntactic complexity in second language writing using fourteen different measures that have been explored or proposed in studies of second language development. The system takes a written language sample as input and produces fourteen indices of syntactic complexity of the sample based on these measures. The system is designed with advanced second language proficiency research in mind, and is therefore developed and evaluated using college-level second language writing data from the Written English Corpus of Chinese Learners (Wen et al. 2005). Experimental results show that the system achieves very high reliability on unseen test data from the corpus. We illustrate how the system is used in an example application to investigate whether and to what extent each of these measures significantly differentiate between different proficiency levels
If both opponents “extend hands in peace” — Why don’t they meet?
Authors: Gavriely-Nuri Dalia
Published: November 2010

This article offers a preliminary and partial mapping of some cultural misconceptions inherent in the Israeli peace discourse. It focuses on one of the central mythic metaphors belonging to this discourse: “We extend our hand in peace.” First articulated in “The Declaration of the Establishment of the State of Israel” (1948). After more than six decades of endless repetition in speeches made by Israeli political leaders, the metaphor has become a fertile arena for learning about Israel’s cultural codes and cultural heritage relating to peace: While expressing the sincere will to make peace, use of the metaphor simultaneously demonstrates moral superiority, feelings of deprivation, latent threat, and recognition of its efficiency for creating a positive image abroad. A discursive analysis of the metaphor reveals four barriers to the effective continuation of a peace process: Images of the Arab opponent, Israel’s self-image, relationships between opponents in addition to the opponents’ readiness to achieve peace.
Cep152 acts as a scaffold for recruitment of Plk4 and CPAP to the centrosome
Authors: Cizmecioglu Onur , Arnold Marc , Bahtz Ramona , Settele Florian , Ehret Lena , Haselmann-Weiß Uta , Antony Claude , Hoffmann Ingrid
Published: November 2010

Both gain and loss of function studies have identified the Polo-like kinase Plk4/Sak as a crucial regulator of centriole biogenesis, but the mechanisms governing centrosome duplication are incompletely understood. In this study, we show that the pericentriolar material protein, Cep152, interacts with the distinctive cryptic Polo-box of Plk4 via its N-terminal domain and is required for Plk4-induced centriole overduplication. Reduction of endogenous Cep152 levels results in a failure in centriole duplication, loss of centrioles, and formation of monopolar mitotic spindles. Interfering with Cep152 function prevents recruitment of Plk4 to the centrosome and promotes loss of CPAP, a protein required for the control of centriole length in Plk4-regulated centriole biogenesis. Our results suggest that Cep152 recruits Plk4 and CPAP to the centrosome to ensure a faithful centrosome duplication process.
Identification of a polyI:C-inducible membrane protein that participates in dendritic cell–mediated natural killer cell activation
Authors: Ebihara Takashi , Azuma Masahiro , Oshiumi Hiroyuki , Kasamatsu Jun , Iwabuchi Kazuya , Matsumoto Kenji , Saito Hirohisa , Taniguchi Tadatsugu , Matsumoto Misako , Seya Tsukasa
Published: November 2010

In myeloid dendritic cells (mDCs), TLR3 is expressed in the endosomal membrane and interacts with the adaptor toll/interleukin 1 receptor homology domain–containing adaptor molecule 1 (TICAM-1; TRIF). TICAM-1 signals culminate in interferon (IFN) regulatory factor (IRF) 3 activation. Co-culture of mDC pretreated with the TLR3 ligand polyI:C and natural killer (NK) cells resulted in NK cell activation. This activation was triggered by cell-to-cell contact but not cytokines. Using expression profiling and gain/loss-of-function analyses of mDC genes, we tried to identify a TICAM-1–inducing membrane protein that participates in mDC-mediated NK activation. Of the nine candidates screened, one contained a tetraspanin-like sequence and satisfied the screening criteria. The protein, referred to as IRF-3–dependent NK-activating molecule (INAM), functioned in both the mDC and NK cell to facilitate NK activation. In the mDC, TICAM-1, IFN promoter stimulator 1, and IRF-3, but not IRF-7, were required for mDC-mediated NK activation. INAM was minimally expressed on NK cells, was up-regulated in response to polyI:C, and contributed to mDC–NK reciprocal activation via its cytoplasmic tail, which was crucial for the activation signal in NK cells. Adoptive transfer of INAM-expressing mDCs into mice implanted with NK-sensitive tumors caused NK-mediated tumor regression. We identify a new pathway for mDC–NK contact-mediated NK activation that is governed by a TLR signal-derived membrane molecule.
Fabrication of an inkjet-printed seed pattern with silver nanoparticulate ink on a textured silicon solar cell wafer
Authors: Shin Dong-Youn
Published: November 2010

In this study, the possibility of using inkjet printing in the fabrication of a conductive seed pattern on a textured silicon solar wafer is investigated. Firstly, solar cell wafers were coated with a hydrophobic solution. It was found that the surface texture of a solar cell wafer causes a slight increase in the contact angle of silver nanoparticulate ink by 7.5° due to a weak Cassie–Baxter wetting state. After selective laser ablation of the hydrophobic coating and the SiN
x
layer in preparation for the surface energy-patterned finger electrode regions, silver nanoparticulate ink was deposited with a piezo drop-on-demand inkjet print head. Because the threshold laser fluence for the ablation of the hydrophobic coating is lower than that for the SiN
x
layer, the effective width of a surface energy-patterned finger electrode region with the Gaussian laser beam profile was found to be wider than the actual width of the SiN
x
-ablated region. Although this initially results in a widened deposition of silver nanoparticulate ink, the subsequent drying of silver nanoparticulate ink is found to cause a reduction of line width of around 6% to 14%. Therefore, the final line width of the seed pattern is the outcome of two opposing phenomena. The physical and electrical characteristics of the seed pattern are as narrow as 58.5 ± 1.2 µm, as thick as 1.81 µm on average and as conductive as 2.72 µΩ cm.
“The Devil We Know”: Gold Coast Consumers, Local Employees, and the United Africa Company, 1940–1960
Authors: Murillo Bianca
Published: November 2010

On January 31, 1957, about five weeks before the Gold Coast gained political independence from Britain, the country's first Prime Minister Kwame Nkrumah inaugurated the opening of Kingsway, Accra, the country's largest department store. Owned and operated by the United Africa Company (UAC), a subsidiary of the Anglo-Dutch multinational Unilever, Kingsway Stores were well known throughout British West Africa as a chain of urban retail outlets. Although Kingsway Stores originally targeted the needs of European colonials and their families, they increasingly attracted elite and emerging middle-class African shoppers. Equipped with an elevator, a modern car park, and three floors of retail space, the new state-of-the-art Kingsway building would be the first of its kind in all of West Africa. Invited to give the inaugural speech at the store's grand opening, Nkrumah stated: “It is idle to pretend that the people of the Gold Coast . . . [have] always been on the friendliest terms with such a mighty financial power as Unilever. But . . . my government like myself and the people of the Gold Coast, does prefer the devil it knows to the devil it does not know.”