bluuebunny/crossref_metadata_2025 huggingface dataset:
Data-Constrained Microstructure Characterization with Multispectrum X-Ray Micro-CT
Authors: Mayo Sheridan C. , Tulloh Andrew M. , Trinchi Adrian , Yang Sam Y.S.
Published: May 2012

Conventional X-ray microcomputed tomography (micro-CT) is not usually sufficient to determine microscopic compositional distributions as it is limited to measuring the X-ray attenuation of the sample, which for a given dataset can be similar for materials of different composition. In contrast, the present work enables three-dimensional compositional analysis with a data-constrained microstructure (DCM) modeling methodology, which uses two or more CT datasets acquired with different X-ray spectra and incorporates them as model constraints. For providing input data for DCM, we have also developed a method of micro-CT data collection that enables two datasets with different X-ray spectra to be acquired in parallel. Such data are used together with the DCM methodology to predict the distributions of corrosion inhibitor and filler in a polymer matrix. The DCM-predicted compositional microstructures have a reasonable agreement with energy dispersive X-ray images taken on the sample surface.
Paradigm Resolution in the Life Cycle of Norse Umlaut
Authors: Iverson Gregory K. , Salmons Joseph C.
Published: May 2012

This paper follows on recent work (Iverson & Salmons 2004, 2007; Kiparsky 2005, 2006) seeking to resolve Kock's 1888 paradox intro-duced in his celebrated “period theory” of Old Norsei-umlaut. The basic finding is this: In paradigms where a phonological innovation has been rendered opaque by the operation of other sound changes, restructuring of the base form incorporates rather than derives the results of the innovation as it dies out; but if the innovation remains transparent in certain other paradigms, its expiration enables reversion to the antecedent phonological form. Both patterns can be subsumed under the traditional rubric of analogy, resulting in allomorphically uniform paradigms, but the former generalizes a sound change to con-texts in which it never occurred naturally, whereas the latter actually undoes, or reverses, a sound change.*
Thoughts on the diversity of convergent evolution of bioluminescence on earth
Authors: Waldenmaier Hans E. , Oliveira Anderson G. , Stevani Cassius V.
Published: May 2012

The widespread independent evolution of analogous bioluminescent systems is one of the most impressive and diverse examples of convergent evolution on earth. There are roughly 30 extant bioluminescent systems that have evolved independently on Earth, with each system likely having unique enzymes responsible for catalysing the bioluminescent reaction. Bioluminescence is a chemical reaction involving a luciferin molecule and a luciferase or photoprotein that results in the emission of light. Some independent systems utilize the same luciferin, such as the use of tetrapyrrolic compounds by krill and dinoflagellates, and the wide use of coelenterazine by marine organisms, while the enzymes involved are unique. One common thread among all the different bioluminescent systems is the requirement of molecular oxygen. Bioluminescence is found in most forms of life, especially marine organisms.

Bioluminescence in known to benefit the organism by: attraction, repulsion, communication, camouflage, and illumination. The marine ecosystem is significantly affected by bioluminescence, the only light found in the pelagic zone and below is from bioluminescent organisms.

Transgenic bioluminescent organisms have revolutionized molecular research, medicine and the biotechnology industry. The use of bioluminescence in studying molecular pathways and disease allows for non-invasive and real-time analysis. Bioluminescence-based assays have been developed for several analytes by coupling luminescence to many enzyme-catalysed reactions.
Exciting Science in Middle Schools
Authors: Lyman Charles
Published: May 2012

In his biography Steve Jobs, Walter Isaacson describes how a single elementary school teacher could inspire a kid to study math and science. During those same formative years, Jobs's neighborhood was filled with engineers who could discuss nifty science topics with young Steve. While today's average school kid may not have such influences, the fact remains that Steve Jobs turned toward math and science before high school. Interest in science should be kindled during middle school so that students will take appropriate courses in high school in preparation to study science in college.
Relativistic electron scattering by large amplitude electromagnetic ion cyclotron waves: The role of phase bunching and trapping
Authors: Liu Kaijun , Winske Dan , Gary S. Peter , Reeves Geoffrey D.
Published: May 2012

Test particle computations are performed to study the interactions of relativistic electrons with electromagnetic ion cyclotron waves propagating parallel to the background magnetic field in a homogeneous plasma. In addition to their pitch angle scattering, electrons experience phase bunching and trapping and become clustered in gyrophase angle when the wave amplitude is sufficiently large. The concepts of electron phase bunching and trapping are defined and first illustrated for electrons interacting with a monochromatic wave. When the wave amplitude is sufficiently large, the electrons in or nearly in resonance with the wave are mainly phase trapped while the off‐resonance electrons are only phase bunched. Phase trapping of electrons leads to nonlinear advection of the electrons toward the resonant pitch angle, at which the electrons with a specified kinetic energy are in resonance with the wave. For a broadband spectrum of incoherent waves, these general trends of electron phase bunching and trapping remain qualitatively the same, but they are not as evident as in the monochromatic wave case due to phase mixing of the electrons. The pitch angle diffusion coefficient and advection rate are evaluated from test particle computations of relativistic electron scattering by broadband waves. The results agree well with quasi‐linear results when the waves are sufficiently weak, as expected. When the waves become strong, however, the diffusion coefficient and advection rate deviate from the predictions of quasi‐linear theory, due to electron phase bunching and trapping. The diffusion coefficient is a flatter function of pitch angle than that predicted by quasi‐linear theory. Electron phase bunching and trapping introduce nonlinear advection of the electrons, which is additional to the inherent advection included in the diffusion equation of quasi‐linear theory and shifts the electrons toward the pitch angle at which the electrons with a specified kinetic energy are in resonance with the wave at the spectral peak. Finally, our results suggest that electron phase bunching and trapping by large amplitude waves flatten the pitch angle distribution and reduce the loss rate for relativistic electrons trapped in the radiation belts, compared to the predictions of quasi‐linear theory. The present study focuses only on local electron scattering in a homogeneous background magnetic field and the results are therefore subject to possible modification after bounce averaging.
Testing lunar permanently shadowed regions for water ice: LEND results from LRO
Authors: Sanin A. B. , Mitrofanov I. G. , Litvak M. L. , Malakhov A. , Boynton W. V. , Chin G. , Droege G. , Evans L. G. , Garvin J. , Golovin D. V. , Harshman K. , McClanahan T. P. , Mokrousov M. I. , Mazarico E. , Milikh G. , Neumann G. , Sagdeev R. , Smith D. E. , Starr R. D. , Zuber M. T.
Published: May 2012

We use measurements from the Lunar Exploration Neutron Detector (LEND) collimated sensors during more than one year of the mapping phase of NASA's Lunar Reconnaissance Orbiter (LRO) mission to make estimates of the epithermal neutron flux within known large Permanently Shadowed Regions (PSRs). These are compared with the local neutron background measured outside PSRs in sunlit regions. Individual and collective analyses of PSR properties have been performed. Only three large PSRs, Shoemaker and Cabeus in the south and Rozhdestvensky U in the north, have been found to manifest significant neutron suppression. All other PSRs have much smaller suppression, only a few percent, if at all. Some even display an excess of neutron emission in comparison to the sunlit vicinity around them. Testing PSRs collectively, we have not found any average suppression for them. Only the group of 18 large PSRs, with area >200 km2, show a marginal effect of small average suppression, ∼2%, with low statistical confidence. A ∼2% suppression corresponds to ∼125 ppm of hydrogen taking into account the global neutron suppression near the lunar poles and assuming a homogeneous H distribution in depth in the regolith. This means that all PSRs, except those in Shoemaker, Cabeus and Rozhdestvensky U craters, do not contain any significant amount of hydrogen in comparison with sunlit areas around them at the same latitude.
Prediction of water retention curves for dry soils from an established pedotransfer function: Evaluation of the Webb model
Authors: Schneider M. , Goss K.‐U.
Published: May 2012

The van Genuchten curve, and its prediction by various pedotransfer functions, has long been an established method to describe the water retention curve (WRC) in soils, but it cannot be used to describe water retention under conditions dryer then the wilting point. Water retention under dry conditions follows a log linear function, which does not agree with the extrapolated van Genuchten curve. As a remedy Webb (2000) proposed an approach that predicts this linear function for the dry range with a smooth transition to the van Genuchten curve that has been fitted to experimental data for the moist range. In this work we present the prediction of water retention curves for 31 soils under dry conditions using the approach presented by Webb. In addition to the larger number of soils that we use for evaluation we deviate from the original Webb approach in two ways: (a) we use predicted (Rosetta) rather than fitted van Genuchten curves and (b) we use a corrected endpoint at zero water content. The outcome reveals good results for the prediction of water retention curves for the dry region and provides a smooth transition between the moist and the dry region of the water retention curve. Occasional inferior performance for some data is likely due to uncertainties in the texture data or in the choice of the right bulk density rather than due to conceptual shortcomings of the Webb approach. This work shows that the WRC for the whole humidity range, from oven dryness to full saturation, can be described by two functions with a smooth transition whose parameters can all be predicted by Rosetta without the need of experimental information.
Water in cratonic lithosphere: Calibrating laboratory‐determined models of electrical conductivity of mantle minerals using geophysical and petrological observations
Authors: Jones Alan G. , Fullea Javier , Evans Rob L. , Muller Mark R.
Published: May 2012

Measurements of electrical conductivity of “slightly damp” mantle minerals from different laboratories are inconsistent, requiring geophysicists to make choices between them when interpreting their electrical observations. These choices lead to dramatically different conclusions about the amount of water in the mantle, resulting in conflicting conclusions regarding rheological conditions; this impacts on our understanding of mantle convection, among other processes. To attempt to reconcile these differences, we test the laboratory‐derived proton conduction models by choosing the simplest petrological scenario possible – cratonic lithosphere – from two locations in southern Africa where we have the most complete knowledge. We compare and contrast the models with field observations of electrical conductivity and of the amount of water in olivine and show that none of the models for proton conduction in olivine proposed by three laboratories are consistent with the field observations. We derive statistically model parameters of the general proton conduction equation that satisfy the observations. The pre‐exponent dry proton conduction term (σ0) and the activation enthalpy (ΔHwet) are derived with tight bounds, and are both within the broader 2σ errors of the different laboratory measurements. The two other terms used by the experimentalists, one to describe proton hopping (exponent ron pre‐exponent water contentCw) and the other to describe H2O concentration‐dependent activation enthalpy (termαCw1/3 added to the activation energy), are less well defined and further field geophysical and petrological observations are required, especially in regions of higher temperature and higher water content.
Global‐phase seismic interferometry unveils P‐wave reflectivity below the Himalayas and Tibet
Authors: Ruigrok Elmer , Wapenaar Kees
Published: May 2012

A number of seismic methods exist to image the lithosphere below a collection of receivers, using distant earthquakes. In the current practice, especially mode‐conversions in teleseismic phases are utilized. We present a new method that takes advantage of the availability of global phases. This method is called global‐phase seismic interferometry (GloPSI). With GloPSI, zero‐offset reflections are extracted from reverberations near the array caused by global seismicity. We exemplify GloPSI with data from the Hi‐CLIMB experiment (2002–2005) and migrate the obtained reflection responses. This results in a 800 km long reflectivity profile through the Himalayas and a large part of the Tibetan Plateau.
Intense perpendicular electric fields associated with three‐dimensional magnetic reconnection at the subsolar magnetopause
Authors: Pritchett P. L. , Mozer F. S. , Wilber M.
Published: May 2012

The properties of magnetic reconnection in an asymmetric magnetopause current layer are investigated using three‐dimensional particle‐in‐cell simulations and THEMIS subsolar magnetopause crossings. The strong density gradient region on the magnetosphere side of the current layer is found to be unstable to a k⋅B = 0 lower hybrid drift instability type mode with dominant wave number kyρe ∼ 0.5. The accompanying perpendicular electric fields are intense (Ey ∼ 4vAB0 ∼ 100 mV/m) with characteristic frequencies (typically two narrowband signals) between the proton cyclotron and lower hybrid frequencies. In the observations, neither the wave amplitude nor frequency appears to be sensitive to the value of any guide magnetic field or to the degree of asymmetry in Bz/n across the magnetopause. These electric fields remain confined away from the reconnection X line and do not appear to affect the value of the reconnection rate.
On the centennial trend estimates of geomagnetic activity indices
Authors: Martini D. , Linthe H.‐J. , Pandey V. S. , Lee D.‐H.
Published: May 2012

In this paper we reanalyze the centennial trend estimates of a number of selected geomagnetic indices. We show that the peculiar latitudinal ordering of century long trends is mainly an artifact related to different scales. Using a scaling method that takes into account the statistical dispersion of the variables alleviates most of the discrepancies associated with latitude dependence. We demonstrate that geomagnetic activity had a roughly homogenous increase over the Northern Hemisphere during 1901–2000 of about 23%, as registered by digital measures. On the other hand, midlatitude data are shown to possess a distinct disproportion dominantly around solar cycle 15. We also demonstrate that analog indices tend to consistently depict lower activity levels in the early decades, thus considerably larger overall increases of about 32% during the twentieth century. This is likely due to the typically conservative approach in quantifying irregular activity (the K value) in those early years with a large number of quiet days. The recently corrected aa index shows an increase on par with similarly analog but local measures at Niemegk and Sodankylä stations. These results show that after its vital calibration, the widely used aa index does quantify reasonably well the global centennial increase in geomagnetic activity.
Electromagnetic ion cyclotron wave generation by planetary pickup ions: One‐dimensional hybrid simulations at sub‐Alfvénic pickup velocities
Authors: Cowee M. M. , Gary S. P.
Published: May 2012

Enhanced electromagnetic plasma waves generated by unstable pickup ion distributions have been detected by spacecraft in several planetary environments including those of Venus, Earth, Mars, comets, Jupiter and Saturn. These waves are important because they can be used as a diagnostic of the local plasma and the ion pickup conditions. Interpretation of these waves relies on understanding the source of free energy and how that free energy is reduced through instability growth. In this manuscript, we focus on the regime where the pickup velocity is sub‐Alfvénic and systematically illustrate some basic differences in instability behavior by carrying out one‐dimensional hybrid simulations of pickup ion‐generated waves for varying pickup angle, α. Although several pickup ion‐driven instabilities are possible in this regime, the dominant electromagnetic instability that is observed is the ion cyclotron ring instability, which generates waves in the spacecraft frame with frequencies near the pickup ion cyclotron frequency. To better understand the instability behavior as well as what wave properties a spacecraft would potentially observe, we carry out the simulations in the bulk plasma frame and in the planetary rest frame (i.e. spacecraft frame). The simulations presented here are not meant to reproduce any particular planetary environment but are intended to illustrate the general behavior in the sub‐Alfvénic pickup velocity regime. We also review the previous observations and dispersion analyses of pickup ion‐driven waves in the relevant planetary environments, and discuss them in terms of our simulation results.
Cloud droplet spectral width relationship to CCN spectra and vertical velocity
Authors: Hudson James G. , Noble Stephen , Jha Vandana
Published: May 2012

Cloud droplet spectral width (standard deviation; sigma; σ) was inversely related to cloud condensation nuclei (CCN) concentrations (NCCN) in the Rain in Cumulus over the Ocean (RICO) project. This was determined from thorough comparisons between flight‐averaged NCCNand microphysics of the lowest altitude cloud passes of 17 RICO flights. Adiabatic model predictions of droplet spectra based on complete below cloud CCN spectra and within‐cloud vertical velocity (W) showed good agreement with measured droplet concentrations and mean diameter (MD) butσ predictions were only weakly correlated with measured σ. Significantly better σ predictions were obtained for mixtures of droplet spectra for distributions of W that were measured in each flight. Adiabatic model predictions for various W applied uniformly to all RICO flights displayed a trend of correlation coefficients (R) for σ‐NCCN plotted against W that changed from positive to negative with increasing W. The σ‐NCCN positive R range at low W corresponds to previous results in stratus clouds where it has been suggested that albedo calculations that include σ reduce the indirect aerosol effect (IAE). The σ‐NCCN negative R range of higher W corresponds to more convective clouds such as RICO where albedo calculations that include σ thus might seem to augment IAE.
Immune Effects of Mesenchymal Stromal Cells in Experimental Stroke
Authors: Scheibe Franziska , Ladhoff Juliane , Huck Jojanneke , Grohmann Maik , Blazej Katja , Oersal Arif , Baeva Nevena , Seifert Martina , Priller Josef
Published: May 2012

Preclinical trials confirmed the potential of mesenchymal stromal cells (MSCs) to improve functional recovery after experimental stroke. Beneficial effects of MSCs are often attributed to their immunosuppressive/immunomodulatory functions. Surprisingly, the influence of MSCs on the immune system after stroke is poorly understood, but requires special consideration because cerebral ischemia is associated with stroke-induced immunodepression that predisposes to bacterial infections with increased mortality. In this study, we intravenously transplanted syngeneic murine bone marrow-derived MSCs (mMSCs) into C57BL/6 mice at 6 hours after transient middle cerebral artery occlusion (MCAo; 60 minutes) to investigate the impact of MSCs on stroke-induced immunodepression. Transplantation of syngeneic splenocytes or phosphate-buffered saline (PBS) served as controls. An immune status was determined by flow cytometry on days 3 and 14 after MCAo, which did not reveal any negative effects of cell transplantation on stroke-induced immunodepression. Although our mMSCs were found to exert immunosuppressive effects in vitro, stroke-mediated immune cell dysfunction was not altered by mMSCs in ex-vivo stimulation assays with lipopolysaccharide or concanavalin A. Moreover, systemic inflammatory cytokine levels (interleukin-6, tumor necrosis factor α, interferon γ, monocyte chemoattractant protein-1) remained unchanged in the sera of mice after cerebral ischemia and cell transplantation. These results reduce safety concerns about MSC administration in ongoing clinical stroke trials.
Cysteine biosynthesis, in concert with a novel mechanism, contributes to sulfide detoxification in mitochondria of Arabidopsis thaliana
Authors: Birke Hannah , Haas Florian H. , De Kok Luit J. , Balk Janneke , Wirtz Markus , Hell Rüdiger
Published: May 2012

In higher plants, biosynthesis of cysteine is catalysed by OAS-TL [O-acetylserine(thiol)lyase], which replaces the activated acetyl group of O-acetylserine with sulfide. The enzyme is present in cytosol, plastids and mitochondria of plant cells. The sole knockout of mitochondrial OAS-TL activity (oastlC) leads to significant reduction of growth in Arabidopsis thaliana. The reason for this phenotype is still enigmatic, since mitochondrial OAS-TL accounts only for approximately 5% of total OAS-TL activity. In the present study we demonstrate that sulfide specifically intoxicates Complex IV activity, but not electron transport through Complexes II and III in isolated mitochondria of oastlC plants. Loss of mitochondrial OAS-TL activity resulted in significant inhibition of dark respiration under certain developmental conditions. The abundance of mitochondrially encoded proteins and Fe–S cluster-containing proteins was not affected in oastlC. Furthermore, oastlC seedlings were insensitive to cyanide, which is detoxified by β-cyano-alanine synthase in mitochondria at the expense of cysteine. These results indicate that in situ biosynthesis of cysteine in mitochondria is not mandatory for translation, Fe–S cluster assembly and cyanide detoxification. Finally, we uncover an OAS-TL-independent detoxification system for sulfide in mitochondria of Arabidopsis that allows oastlC plants to cope with high sulfide levels caused by abiotic stresses.
Myosin motor proteins are involved in the final stages of the secretory pathways
Authors: Bond Lisa M. , Brandstaetter Hemma , Sellers James R. , Kendrick-Jones John , Buss Folma
Published: May 2012

In eukaryotes, the final steps in both the regulated and constitutive secretory pathways can be divided into four distinct stages: (i) the ‘approach’ of secretory vesicles/granules to the PM (plasma membrane), (ii) the ‘docking’ of these vesicles/granules at the membrane itself, (iii) the ‘priming’ of the secretory vesicles/granules for the fusion process, and, finally, (iv) the ‘fusion’ of vesicular/granular membranes with the PM to permit content release from the cell. Recent work indicates that non-muscle myosin II and the unconventional myosin motor proteins in classes 1c/1e, Va and VI are specifically involved in these final stages of secretion. In the present review, we examine the roles of these myosins in these stages of the secretory pathway and the implications of their roles for an enhanced understanding of secretion in general.
Regulation of myosin 5a and myosin 7a
Authors: Siththanandan Verl B. , Sellers James R.
Published: May 2012

The myosin superfamily is diverse in its structure, kinetic mechanisms and cellular function. The enzymatic activities of most myosins are regulated by some means such as Ca2+ ion binding, phosphorylation or binding of other proteins. In the present review, we discuss the structural basis for the regulation of mammalian myosin 5a and Drosophila myosin 7a. We show that, although both myosins have a folded inactive state in which domains in the myosin tail interact with the motor domain, the details of the regulation of these two myosins differ greatly.
Melanosomes on the move: a model to understand organelle dynamics
Authors: Hume Alistair N. , Seabra Miguel C.
Published: May 2012

Advances in live-cell microscopy have revealed the extraordinarily dynamic nature of intracellular organelles. Moreover, movement appears to be critical in establishing and maintaining intracellular organization and organellar and cellular function. Motility is regulated by the activity of organelle-associated motor proteins, kinesins, dyneins and myosins, which move cargo along polar MT (microtubule) and actin tracks. However, in most instances, the motors that move specific organelles remain mysterious. Over recent years, pigment granules, or melanosomes, within pigment cells have provided an excellent model for understanding the molecular mechanisms by which motor proteins associate with and move intracellular organelles. In the present paper, we discuss recent discoveries that shed light on the mechanisms of melanosome transport and highlight future prospects for the use of pigment cells in unravelling general molecular mechanisms of intracellular transport.
The many different cellular functions of MYO7A in the retina
Authors: Williams David S. , Lopes Vanda S.
Published: May 2012

Mutations in MYO7A (myosin VIIa) cause Usher syndrome type 1B, a disorder involving profound congenital deafness and progressive blindness. In the retina, most MYO7A is localized in the apical region of the RPE (retinal pigmented epithelial) cells, and a small amount is associated with the ciliary and periciliary membranes of the photoreceptor cells. Its roles appear to be quite varied. Studies with MYO7A-null mice indicate that MYO7A participates in the apical localization of RPE melanosomes and in the removal of phagosomes from the apical RPE for their delivery to lysosomes in the basal RPE. In the first role, MYO7A competes with microtubule motors, but in the second one, it may function co-operatively. An additional role of MYO7A in the RPE is indicated by the requirement for it in the light-dependent translocation of the ER (endoplasmic reticulum)-associated visual cycle enzyme RPE65 and normal functioning of the visual retinoid cycle. In photoreceptor cells lacking MYO7A, opsin accumulates abnormally in the transition zone of the cilium, suggesting that MYO7A functions as a selective barrier for membrane proteins at the distal end of the transition zone. It is likely that the progressive retinal degeneration that occurs in Usher syndrome 1B patients results from a combination of cellular defects in the RPE and photoreceptor cells.
Oxidative chemistry of fluorescent dyes: implications in the detection of reactive oxygen and nitrogen species
Authors: Kalyanaraman Balaraman
Published: May 2012

HE (hydroethidine), a widely used fluorescent dye for detecting intracellular superoxide, undergoes specific oxidation and hydroxylation reactions. The reaction between HE and O2•− (superoxide radical) yields a diagnostic marker product, 2-hydroxyethidium. This is contrary to the popular notion that O2•− oxidizes HE to form ethidium. HE, however, undergoes a non-specific oxidation to form ethidium in the presence of other oxidants (hydroxyl radical, peroxynitrite and perferryl iron) and other dimeric products. The mitochondria-targeted HE analogue Mito-SOX® undergoes the same type of oxidative chemistry to form products similar to those formed from HE. On the basis of the oxidative chemical mechanism of HE and Mito-SOX®, we conclude that flurorescence microscopy or related techniques are not sufficient to measure the superoxide-specific hydroxylated products. HPLC methodologies are required to separate and identify these products. Peroxynitrite reacts rapidly and stoichiometrically with boronates to form specific products. Assays using fluorescent-based boronate probes will be more reliable for peroxynitrite determination than those using either dichlorodihydrofluorescein or dihydrorhodamine.
The WFDC1 gene: role in wound response and tissue homoeostasis
Authors: Ressler Steven J. , Rowley David R.
Published: May 2012

The present evaluates the key features of the WFDC1 [WAP (whey acidic protein) four disulfide core 1] gene that encodes ps20 (20 kDa prostate stromal protein), a member of the WAP family. ps20 was first characterized as a growth inhibitory activity that was secreted by fetal urogenital sinus mesenchymal cells. Purified ps20 exhibited several activities that centre on cell adhesion, migration and proliferation. The WFDC1 gene was cloned, contained seven exons, and was mapped to chromosome 16q24, suggesting that it may function as a tumour suppressor; however, direct evidence of this has not emerged. In vivo, ps20 stimulated angiogenesis, although expression of WFDC1/ps20 was down-regulated in the reactive stroma tumour microenvironment in prostate cancer. WFDC1 expression is differential in other cancers and inflammatory conditions. Recent studies point to a role in viral infectivity. Although mechanisms of action are not fully understood, WFDC1/ps20 is emerging as a secreted matricellular protein that probably affects response to micro-organisms and tissue repair homoeostasis.
Aggresome formation and segregation of inclusions influence toxicity of α-synuclein and synphilin-1 in yeast
Authors: Swinnen Erwin , Büttner Sabrina , Outeiro Tiago F. , Galas Marie-Christine , Madeo Frank , Winderickx Joris , Franssens Vanessa
Published: May 2012

PD (Parkinson's disease) is a neurodegenerative disorder, caused by a selective loss of dopaminergic neurons in the substantia nigra, which affects an increasing number of the elderly population worldwide. One of the major hallmarks of PD is the occurrence of intracellular protein deposits in the dying neurons, termed Lewy bodies, which contain different proteins, including aggregated α-synuclein and its interacting protein synphilin-1. During the last decade, a number of groups developed yeast models that reproduced important features of PD and allowed the deciphering of pathways underlying the cytotoxicity triggered by α-synuclein. Here, we review the recent contributions obtained with yeast models designed to study the presumed pathobiology of synphilin-1. These models pointed towards a crucial role of the sirtuin Sir2 and the chaperonin complex TRiC (TCP-1 ring complex)/CCT (chaperonin containing TCP-1) in handling misfolded and aggregated proteins.
Using yeast models to probe the molecular basis of amyotrophic lateral sclerosis
Authors: Bastow Emma L. , Gourlay Campbell W. , Tuite Mick F.
Published: May 2012

ALS (amyotrophic lateral sclerosis) is a fatal neurodegenerative disease attributable to the death of motor neurons. Associated with ALS are mutations in the genes encoding SOD1 (superoxide dismutase 1), FUS (fused in Sarcoma) protein and TDP-43 (TAR DNA-binding protein-43) each of which leads to aggregation of the respective protein. For example, the ALS-associated mutations in the hSOD1 (human SOD1) gene typically destabilize the native SOD homodimer, leading to misfolding, aggregation and degradation of SOD1. The ALS-associated pathology is not a consequence of the functional inactivation of SOD1 itself, but is rather due to a toxic gain-of-function triggered by mutant SOD1. Recently, the molecular basis of a number of human neurodegenerative diseases resulting from protein misfolding and aggregation, including fALS (familial ALS), was probed by using the baker's yeast, Saccharomyces cerevisiae, as a highly tractable model. Such studies have, for example, identified novel mutant SOD1-specific interactions and demonstrated that mutant SOD1 disrupts mitochondrial homoeostasis. Features of ALS associated with TDP-43 aggregation have also been recapitulated in S. cerevisiae including the identification of modulators of the toxicity of TDP-43. In this paper, we review recent studies of ALS pathogenesis using S. cerevisiae as a model organism and summarize the potential mechanisms involved in ALS progression.
Mitochondrial dynamics in yeast cell death and aging
Authors: Braun Ralf J. , Westermann Benedikt
Published: May 2012

Mitochondria play crucial roles in programmed cell death and aging. Different stimuli activate distinct mitochondrion-dependent cell death pathways, and aging is associated with a progressive increase in mitochondrial damage, culminating in oxidative stress and cellular dysfunction. Mitochondria are highly dynamic organelles that constantly fuse and divide, forming either interconnected mitochondrial networks or separated fragmented mitochondria. These processes are believed to provide a mitochondrial quality control system and enable an effective adaptation of the mitochondrial compartment to the metabolic needs of the cell. The baker's yeast, Saccharomyces cerevisiae, is an established model for programmed cell death and aging research. The present review summarizes how mitochondrial morphology is altered on induction of cell death or on aging and how this correlates with the induction of different cell death pathways in yeast. We highlight the roles of the components of the mitochondrial fusion and fission machinery that affect and regulate cell death and aging.
Duchenne Muscular Dystrophy in a 4-Year-Old Girl due to Heterozygous Frame Shift Deletion of the Dystrophin Gene and Skewed X-Inactivation
Authors: Schänzer A. , Rau I. , Kreß W. , Köhler A. , Neubauer B. , Hahn A.
Published: May 2012

X-linked recessive diseases affect males, whereas female carriers are generally asymptomatic.

We report on a 4-year-old girl who presented with a classical phenotype of Duchenne Muscular Dystrophy (DMD), a severe X-linked recessive type of muscular dystrophy affecting boys in early childhood.

A thorough diagnostic work-up revealed that this resulted from a heterozygous out-of frame deletion in the DMD-gene in combination with an X-inactivation ratio of <10:90 in blood leukocytes and muscle.

The case exemplifies that a skewed X-inactivation pattern has to be taken into account as mechanism causing clinical symptoms in female carriers of X-linked recessive disorders
Effect of adding small amount of inductive fields to O2, Ar/O2 capacitively coupled plasmas
Authors: Lee Min-Hyong , Lee Hyo-Chang , Chung Chin-Wook
Published: May 2012

Electron energy distribution functions (EEDFs) of low pressure O2 plasma were measured by adding small amount of coil power in a capacitive discharge. When the plasma was generated by bias power only, the measured EEDF showed a bi-Maxwellian distribution. However, when a very small coil power (a few Watts) was added, the EEDF evolved abruptly into a Maxwellian distribution, while the electron density was decreased. In an Ar/O2 mixture discharge, this EEDF evolution to the Maxwellian was also observed at a relatively higher coil power. This abrupt change in EEDFs with a very small coil power appears to be attributed to a combined effect of collisionless heating by capacitive and induced electric fields.
Understanding disruptions in tokamaks
Authors: Zakharov Leonid E. , Galkin Sergei A. , Gerasimov Sergei N. , contributors JET-EFDA
Published: May 2012

This paper describes progress achieved since 2007 in understanding disruptions in tokamaks, when the effect of plasma current sharing with the wall was introduced into theory. As a result, the toroidal asymmetry of the plasma current measurements during vertical disruption event (VDE) on the Joint European Torus was explained. A new kind of plasma equilibria and mode coupling was introduced into theory, which can explain the duration of the external kink 1/1 mode during VDE. The paper presents first results of numerical simulations using a free boundary plasma model, relevant to disruptions.
Magnetic assembly of gold core-shell necklace resonators
Authors: Aoki Kanna , Furusawa Kentaro , Tanaka Takuo
Published: May 2012

Gold core-shell necklace structures are assembled by inducing magnetic moments of gold-coated paramagnetic microspheres and a diamagnetic sphere using an external magnetic field. Sphere numbers in a necklace structure was tuned solely by controlling magnetic permeability of background medium. A necklace structure consisting of evenly spaced metal spheres or disks is known to be a good medium for a plasmonic resonance. Therefore, their optical properties were numerically studied. The electric field enhancement by a factor of 1800 was estimated in the gaps between adjacent spheres at a resonant wavelength. The wavelength-scaling strategies of our structures to visible wavelength are also discussed.
Thermophysical and electrical properties of Al-doped ZnO films
Authors: Oka Nobuto , Kimura Kentaro , Yagi Takashi , Taketoshi Naoyuki , Baba Tetsuya , Shigesato Yuzo
Published: May 2012

Thermal diffusivity of Al-doped ZnO (AZO) films with a thickness of 200 nm was quantitatively analyzed using a “rear heating/front detection type” nanosecond thermoreflectance system. AZO monolayer and Mo/AZO/Mo three-layered films were prepared on synthesized silica substrates by DC magnetron sputtering using high density ceramic ZnO–Al2O3 (Al2O3: 2.5 wt. %) and Mo metal targets. The thermal diffusivity and electrical resistivity of the deposited AZO films ranged 1.8 × 10−6 –2.4 × 10−6 m2 s−1 and 2.3 × 10−3–5.9 × 10−4 Ω cm, respectively. The thermal conductivity corresponding to the thermal diffusivity was one order of magnitude smaller than that of sintered AZO ceramics prepared from ZnO and Al2O3 powders. However, it was found to be larger than that of In2O3-based transparent conductive oxide (TCO) films with approximately the same electrical conductivity, thus implying that AZO can be considered an excellent material for diathermanous TCO circuits.
Effect of Li-doping on the magnetic properties of ZnO with Zn vacancies
Authors: Gao Hui-Xia , Xia Jian-Bai
Published: May 2012

Using first-principles calculations, we investigate the electronic and magnetic properties of Zn vacancy in ZnO with and without Li-doping. It is found that the Zn vacancy can induce magnetism but the formation energy of the system is high. We also found that the Li-dopant at either the substitutional sites or the interstitial sites and both at two sites can lower the formation energy of Zn vacancy. The total magnetic moments of the system is increased after Li doping at the substitutional site, while it is decreased after Li doping at the interstitial site. In addition, the extended tails of the wave functions of Zn vacancy make long-ranged spin couplings possible. Li atoms at the substitutional sites further stabilize the long-ranged ferromagnetism induced by Zn vacancies. Thus, it is possible to tune the magnetism of ZnO through defect engineering.
Interplay between magnetism and chemical structure at spinel-spinel interfaces
Authors: Nelson-Cheeseman B. B. , Chopdekar R. V. , Toney M. F. , Arenholz E. , Suzuki Y.
Published: May 2012

By utilizing a graded wedge sample geometry in combination with surface sensitive soft x-ray techniques, we explain the enhanced magnetic properties observed at the interface between two dissimilar magnetic spinel oxide thin films in terms of the chemical and magnetic character of the constituent cations. Through x-ray absorption spectroscopy and magnetic circular dichroism studies, we find that the interfacial cations exhibit chemical valences and site-occupancies which differ remarkably from the bulk of either film. This results in enhanced magnetic properties localized to the interface region. While this phenomena likely arises from cation interdiffusion of 1–2 nm near the interface due to the open spinel crystal structure, this dramatic change in the magnetic properties localized to a thin interface region may provide a route to obtaining isolated interfacial properties in other spinel-structured heterostructures.
Terahertz plasmon amplification using two-dimensional electron-gas layers
Authors: Ali Khorrami Mohammad , El-Ghazaly Samir , Yu Shui-Qing , Naseem Hameed
Published: May 2012

In this study, we present an analytical model to investigate the possibility of guiding and amplifying terahertz (THz) plasmons in a two dimensional electron gas (2DEG) layer of a hetero-structure by applying a bias electric field. This analytical model solves Maxwell equations and semi-classical electronic transport equations inside the biased hetero-structure simultaneously. It is shown that the two dimensional plasmon’s properties alter vastly as the electrons are accelerated by the bias field. Four asymmetric plasmonic modes can propagate inside the un-gated 2DEG layer of the biased hetero-structure. One of these modes in the un-gated 2DEG layer is a growing mode which can be useful in the implementation of THz amplifiers. Since the modes characteristics can be controlled via biasing, design of new plasmonic devices such as modulators and switches is possible by this approach. Similar analysis has been performed in a gated 2DEG layer that shows clear changes in the two dimensional plasmon properties due to the biasing. Unlike the un-gated 2DEG layer, our efforts to find a growing mode in the gated 2DEG layer have failed. These multi-physics models lead to a better understanding of THz plasmonic sources and detectors as well as proposals on new plasmonic devices. Besides, they provide a physical insight into the electron-wave interactions inside the biased hetero-structure.
Effect of charge-transfer complex on the energy level alignment between graphene and organic molecules
Authors: Bae Giyeol , Jung Hyun , Park Noejung , Park Jinwoo , Hong Suklyun , Park Wanjun
Published: May 2012

We performed density-functional theory calculations to study the electronic structures at the interfaces between graphene and organic molecules that have been used in organic light-emitting diodes. In terms of work function, graphene itself is not favorable as either anode or cathode for commonly used electron or hole transport molecular species. However, the formation of charge transfer complex on the chemically inert sp2 carbon surface can provide a particular advantage. Unlike metal surfaces, the graphene surface remains non-bonded to electron-accepting molecules even after electron transfer, inducing an improved Fermi-level alignment with the highest-occupied-molecular-orbital level of the hole-injecting-layer molecules.
Complete tailor-made inverse filter for image processing of scanning SQUID microscope
Authors: Hayashi Masahiko , Ebisawa Hiromichi , Thanh Huy Ho , Ishida Takekazu
Published: May 2012

By introducing a numerical image processing technique, the resolution of scanning SQUID microscope (SSM) has been improved beyond the “naive” limit determined by the size of the pickup (sensor) coil. Our image processing is developed by taking account of the specific characteristics of SSM apparatus, including detailed shape of the coil and its perfect diamagnetism, in a tailor-made manner. The actual experiment has been done for nano-scale superconducting Pb network, and the magnetic field structures apparently smaller than the size of the pickup coil were made visible by our method.
Discontinuous phase transition in a dimer lattice gas
Authors: Dickman Ronald
Published: May 2012

I study a dimer model on the square lattice with nearest neighbor exclusion as the only interaction. Detailed simulations using tomographic entropic sampling show that as the chemical potential is varied, there is a strongly discontinuous phase transition, at which the particle density jumps by about 18% of its maximum value, 1/4. The transition is accompanied by the onset of orientational order, to an arrangement corresponding to the {1/2, 0, 1/2} structure identified by Phares et al. [Physica B 409, 1096 (2011)] in a dimer model with finite repulsion at fixed density. Using finite-size scaling and Binder's cumulant, the expected scaling behavior at a discontinuous transition is verified in detail. The discontinuous transition can be understood qualitatively given that the model possesses eight equivalent maximum-density configurations, so that its coarse-grained description corresponds to that of the q = 8 Potts model.
Fabrication of white light-emitting diodes based on solvothermally synthesized copper indium sulfide quantum dots as color converters
Authors: Song Woo-Seuk , Yang Heesun
Published: May 2012

A facile, large-scalable solvothermal synthesis of copper indium sulfide (CIS) quantum dots (QDs) and their application to the fabrication of QD-based white light-emitting diodes (LEDs) are reported. Depending on CIS QD growth time of 2 versus 5 h, the core/shell structured QDs of CIS/ZnS exhibit tunable emissions of yellow-orange with excellent quantum yields of 55%-91%. A white QD-LED is realized by applying CIS (2 h)/ZnS QD as a blue-to-yellow color converter. Furthermore, a white QD-LED having a blend of yellow and orange QDs is fabricated to improve a color rendering property through spectral extension, and its electroluminescent properties are evaluated.
Toward an attosecond view of molecules
Authors: Miller Johanna L.
Published: May 2012

Theory and experiment combine to examine an important ultrafast process in polyatomic molecules.
Is there any isotopic fractionation of nitrate associated with diffusion and advection?
Authors: Semaoune Priscillia , Sebilo Mathieu , Templier Joëlle , Derenne Sylvie
Published: May 2012

Environmental contextAnthropogenic nitrogen inputs have significant effects on terrestrial and aquatic ecosystems, the extent of which can be traced by using the natural stable isotopic composition of nitrate to integrate the sources of nitrogen and the biological processes of their production. In ecosystems, nitrates are transported by diffusion in water and advection of water masses, but these physical processes have not been characterised in terms of isotopic fractionation. We report experiments demonstrating that physical transport processes have a negligible effect on the isotopic composition of dissolved nitrate.
AbstractWe experimentally investigated the effect of the physical process of transport (diffusion and advection) on the isotopic composition of nitrate (δ15N and δ18O). Strict diffusion of nitrate in water was studied using a modified Richter apparatus. The combination of diffusion and advection processes was followed by elution of nitrate solution onto silica gel column. No significant isotopic fractionation was observed.