bluuebunny/crossref_metadata_2025 huggingface dataset:
Synchronous measurement of even and odd order intermodulation distortion at the resonant frequency of a superconducting resonator
Authors: Pease Evan K. , Dober Bradley J. , Remillard S. K.
Published: February 2010

A method has been developed that uses three input tones to measure both even and odd order intermodulation distortions (IMDs) inside the pass band of resonant devices. With this technique the surface current density of both the driving signal and the IMD tones can be quantified. Synchronous, or same frequency, measurement of both even and odd order distortions permits quantitative comparison of the respective nonlinearity currents measured within the same time scale. As an example of this technique, a superconducting resonator is used to generate even and odd order IMDs at the same frequency, resulting in physical conclusions, which are pertinent to current research in high temperature superconductors. While varying the level of only one tone, the expected slope of the IMD current versus the driving signal current for both orders is unity, but that is only observed at high temperature when the superconductor becomes very lossy. An observed smaller slope at lower temperatures gives support to the linear-nonlinear interaction model. Also, a sharp increase in the third order IMD relative to the second order IMD near TC gives support to a substantial nonlinear Meissner effect.
A multichamber system for analyzing the outgassing, deposition, and associated optical degradation properties of materials in a vacuum
Authors: Singal Jack , Schindler Rafe , Chang Chihway , Czodrowski Patrick , Kim Peter
Published: February 2010

We report on the camera materials test chamber, a multivessel apparatus that analyzes the outgassing consequences of candidate materials for use in the vacuum cryostat of a new telescope camera. The system measures the outgassing products and rates of samples of materials at different temperatures and collects films of outgassing products to measure the effects on light transmission in six optical bands. The design of the apparatus minimizes potential measurement errors introduced by background contamination.
Direct investigation on conducting nanofilaments in single-crystalline Ni/NiO core/shell nanodisk arrays
Authors: Hwang Inrok , Choi Jinsik , Hong Sahwan , Kim Jin-Soo , Byun Ik-Su , Bahng Jae Ho , Koo Ja-Yong , Kang Sung-Oong , Park Bae Ho
Published: February 2010

We report resistive switching characteristics of single-crystalline Ni/NiO core/shell nanodisk arrays, in which the conducting filaments are highly localized on the surface of nanostructure. The local current distributions observed in such a single-grained nanodisk demonstrate that the contact area and the contact time between the conductive tip of conducting atomic force microscopy and the surface of nanodisk critically influence the voltage-stress-induced electroforming behaviors of nanofilaments in NiO switching nanoblocks. These contact parameters, such as the contact area and the contact time, are interpreted to the electrode size and the voltage-stress time for the formation of filaments in metal oxides.
B diffusion in implanted Ni2Si and NiSi layers
Authors: Blum I. , Portavoce A. , Chow L. , Mangelinck D. , Hoummada K. , Tellouche G. , Carron V.
Published: February 2010

B diffusion in implanted Ni2Si and NiSi layers has been studied using secondary ion mass spectrometry, and compared to B redistribution profiles obtained after the reaction of a Ni layer on a B-implanted Si(001) substrate, in same annealing conditions (400–550 °C). B diffusion appears faster in Ni2Si than in NiSi. The B solubility limit is larger than 1021 atom cm−3 in Ni2Si, while it is ∼3×1019 atom cm−3 in NiSi. The solubility limit found in NiSi is in agreement with the plateau observed in B profiles measured in NiSi after the reaction of Ni on B-implanted Si.
Measurements of the write error rate in bit patterned magnetic recording at 100–320 Gb/in2
Authors: Grobis M. , Dobisz E. , Hellwig O. , Schabes M. E. , Zeltzer G. , Hauet T. , Albrecht T. R.
Published: February 2010

We demonstrate a technique for measuring the intrinsic bit-error-rate as a function of write misregistration in bit patterned media. We examine the recording performance at bit densities of 100, 200, and 320 Gigabits per square inch (Gb/in2) and find that the on-track write misregistration margin for error rates below 10−4 is ∼1/4 of a bit length for all three densities. We demonstrate two-dimensional recording at sub 10−4 bit error rate at 100 and 200 Gb/in2 and with a 10−3 bit error rate at 320 Gb/in2.
Electron cyclotron effective mass in indium nitride
Authors: Goiran Michel , Millot Marius , Poumirol Jean-Marie , Gherasoiu Iulian , Walukiewicz Wladek , Leotin Jean
Published: February 2010

We report on cyclotron effective mass measurement in indium nitride epilayers grown on c-sapphire, using the thermal damping of Shubnikov-de-Haas oscillations obtained in the temperature range 2–70 K and under magnetic field up to 60 T. We unravel an isotropic electron cyclotron effective mass equal to 0.062±0.002m0 for samples having electron concentration near 1018 cm−3. After nonparabolicity and polaron corrections we estimate a bare mass at the bottom of the band equal to 0.055±0.002m0.
Influence of freely diffusing excitons on the photoluminescence spectrum of Si thick films with depth distribution of strain
Authors: Wang Dong , Yang Haigui , Kitamura Tokuhide , Nakashima Hiroshi
Published: February 2010

We present an interpretation of photoluminescence (PL) for relatively thick Si films (200–300 nm) with depth distribution of strain, in which freely diffusing excitons influence the PL signal that originates from layers with different strain conditions. Micro-PL was excited by a 325 nm laser at 8.5 K for the Si films. The PL spectra clearly depended on the thickness of the strained part (ts) in the strained Si film. Under the condition of ts greater than the penetration depth (dp) of 325 nm line for Si, only the strained-part-related PL (PLs) could be observed but not the unstrained-part-related PL (PLus). With a decrease in ts, PLus gradually appeared and became strong, and simultaneously PLs became weak. For positions with very small ts, PLs could never be observed. The strain completion for the Si films was also investigated based on exciton behaviors in strained semiconductor. These characteristics of PL are useful references for understanding exciton behavior in semiconductor with depth distribution of band gap.
Generic behavior of the hydrodynamic function of charged colloidal suspensions
Authors: Gapinski Jacek , Patkowski Adam , Nägele Gerhard
Published: February 2010

We discuss the generic behavior of the hydrodynamic function H(q) and diffusion function D(q) characterizing the short-time diffusion in suspensions of charge-stabilized colloidal spheres, by covering the whole fluid regime. Special focus is given to the behavior of these functions at the freezing transition specified by the Hansen–Verlet freezing rule. Results are presented in dependence on scattering wavenumber q, effective particle charge, volume fraction, salt concentration, and particle size, by considering both the low-charge and high-charge branch solutions of static structure factors. The existence of two charge branches leads to the prediction of a re-entrant melting-freezing-melting transition for increasing particle concentration at very low salinity. A universal limiting contour line is derived for the principal peak height value of H(q), independent of particle charge and diameter, and concentration and salinity, which separates the fluid from the fluid-solid coexistence region. This line is only weakly dependent on the value of the structure factor peak height entering the Hansen–Verlet rule. A dynamic freezing criterion is derived in terms of the short-time cage diffusion coefficient, a quantity easily measurable in a scattering experiment. The higher-dimensional parameter scans underlying this study make use of the fast and highly efficient δγ-scheme in conjunction with the analytic rescaled mean spherical approximation input for the static structure factor. Our results constitute a comprehensive database useful to researchers performing dynamic scattering experiments on charge-stabilized dispersions.
Radiation chemistry in ammonia-water ices
Authors: Loeffler M. J. , Raut U. , Baragiola R. A.
Published: February 2010

We studied the effects of 100 keV proton irradiation on films of ammonia-water mixtures between 20 and 120 K. Irradiation destroys ammonia, leading to the formation and trapping of H2, N2, NO, and N2O, the formation of cavities containing radiolytic gases, and ejection of molecules by sputtering. Using infrared spectroscopy, we show that at all temperatures the destruction of ammonia is substantial, but at higher temperatures (120 K), it is nearly complete (∼97% destroyed) after a fluence of 1016 ions/cm2. Using mass spectroscopy and microbalance gravimetry, we measure the sputtering yield of our sample and the main components of the sputtered flux. We find that the sputtering yield depends on fluence. At low temperatures, the yield is very low initially and increases quadratically with fluence, while at 120 K the yield is constant and higher initially. The increase in the sputtering yield with fluence is explained by the formation and trapping of the ammonia decay products, N2 and H2, which are seen to be ejected from the ice at all temperatures.
Structural and electrical properties of ZnO nanorods and Ti buffer layers
Authors: Kwak C.-H. , Kim B.-H. , Park C.-I. , Seo S.-Y. , Kim S.-H. , Han S.-W.
Published: February 2010

Vertically-well-aligned ZnO nanorods were synthesized on Ti buffer layers by a metal-organic chemical-vapor deposition process. Structural analyses demonstrated that the ZnO nanorods were well-aligned in the c-axis and ab-plane. Transmission electron microscopy (TEM) showed that the Ti buffer layer was amorphous and interdiffused into the ZnO nanorods. Energy-dispersive spectroscopy (EDS) analysis revealed the Ti buffer layers to be slightly oxide. Extended x-ray absorption fine structure confirmed the TEM and EDS results. The I-V characteristic measurements showed a 20-fold increase in current density with the Ti buffer layer, suggesting excellent electrical contact between the Ti buffer layer and ZnO nanorods.
Doping and optimal electron spin polarization in n-ZnMnSe for quantum-dot spin-injection light-emitting diodes
Authors: Löffler W. , Höpcke N. , Kalt H. , Li S. F. , Grün M. , Hetterich M.
Published: February 2010

Utilizing the diluted magnetic semiconductor ZnMnSe for electron spin alignment near-perfect spin state preparation in semiconductor quantum dots has been demonstrated. We show that the electron spin polarization depends strongly on the electron concentration in ZnMnSe:Cl. Using a model which takes accurately the Zeeman sublevel occupation into account, we can explain well the experimentally observed results. We find that the electron concentration must be below the effective density of states to obtain full electron spin polarization and best device operation. This is especially important in II-VI spin-aligner materials with a low density of states.
Giant anisotropic magnetoresistance in insulating ultrathin (Ga,Mn)As
Authors: Gareev R. R. , Petukhov A. , Schlapps M. , Sadowski J. , Wegscheider W.
Published: February 2010

Molecular-beam epitaxy grown, 5 nm thick annealed Ga0.95Mn0.05As films demonstrate transition from metallic to insulating state for sheet resistances near resistance quantum, which we connect with the two-dimensional hole localization. Below the metal-insulator transition we found the giant anisotropic magnetoresistance (GAMR) effect, which depends on the orientation of magnetization to crystallographic axes and demonstrates the twofold symmetry angular dependence. The GAMR manifests itself in positive magnetoresistance near 50% at T=1.7 K for H//[110] crystallographic direction in contrast to smaller negative magnetoresistance for H//[11¯0] direction. We connect the GAMR with formation of high- and low-resistance states with different localization due to anisotropic spin-orbit interaction.
Corrigendum to: Assessing canopy fuel stratum characteristics in crown fire prone fuel types of western North America
Authors: Cruz Miguel G. , Alexander Martin E. , Wakimoto Ronald H.
Published: February 2010

Application of crown fire behavior models in fire management decision-making have been limited by the difficulty of quantitatively describing fuel complexes, specifically characteristics of the canopy fuel stratum. To estimate canopy fuel stratum characteristics of four broad fuel types found in the western United States and adjacent areas of Canada, namely Douglas-fir, ponderosa pine, mixed conifer, and lodgepole pine forest stands, data from the USDA Forest Service's Forest Inventory and Analysis (FIA) database were analysed and linked with tree-level foliage dry weight equations. Models to predict canopy base height (CBH), canopy fuel load (CFL) and canopy bulk density (CBD) were developed through linear regression analysis and using common stand descriptors (e.g. stand density, basal area, stand height) as explanatory variables. The models developed were fuel type specific and coefficients of determination ranged from 0.90 to 0.95 for CFL, between 0.84 and 0.92 for CBD and from 0.64 to 0.88 for CBH. Although not formally evaluated, the models seem to give a reasonable characterization of the canopy fuel stratum for use in fire management applications.
Use of linguistic estimates and vegetation indices to assess post-fire vegetation regrowth in woodland areas
Authors: Jacobson Carol R.
Published: February 2010

This study examined an area of woodland that was recovering from severe fire in Royal National Park (NSW, Australia). A non-destructive method of field sampling is required for vulnerable recovering vegetation and therefore classification of digital photographs using linguistic terms was trialled. The linguistic data for three vegetation strata (canopy, shrub and ground) were converted to crisp scores and compared with vegetation index data derived from remotely sensed imagery. All possible subset regression was used to test the proposition that the combined vegetation scores (independent variables) would explain the values of NDVI (Normalized Difference Vegetation Index) and NDMI (Normalized Difference Moisture Index). Vegetation scores for the three strata were also combined using simplified weighting ratios to assess broad relationships between the indices and field data. The combined vegetation scores explained ~60% of the variation in the vegetation index data and inclusion of variables representing multiple strata explained more of the variation than any single variable. The precise value of the weights used to combine the layers did not affect the strength of the association. A simple ratio is proposed that may be useful to estimate woodland parameters under similar conditions, by inversion of the relationship with vegetation index data.
Monitoring post-wildfire vegetation response with remotely sensed time-series data in Spain, USA and Israel
Authors: van Leeuwen Willem J. D. , Casady Grant M. , Neary Daniel G. , Bautista Susana , Alloza José Antonio , Carmel Yohay , Wittenberg Lea , Malkinson Dan , Orr Barron J.
Published: February 2010

Due to the challenges faced by resource managers in maintaining post-fire ecosystem health, there is a need for methods to assess the ecological consequences of disturbances. This research examines an approach for assessing changes in post-fire vegetation dynamics for sites in Spain, Israel and the USA that burned in 1998, 1999 and 2002 respectively. Moderate Resolution Imaging Spectroradiometer satellite Normalized Difference Vegetation Index (NDVI) time-series data (2000–07) are used for all sites to characterise and track the seasonal and spatial changes in vegetation response. Post-fire trends and metrics for burned areas are evaluated and compared with unburned reference sites to account for the influence of local environmental conditions. Time-series data interpretation provides insights into climatic influences on the post-fire vegetation. Although only two sites show increases in post-fire vegetation, all sites show declines in heterogeneity across the site. The evaluation of land surface phenological metrics, including the start and end of the season, the base and peak NDVI, and the integrated seasonal NDVI, show promising results, indicating trends in some measures of post-fire phenology. Results indicate that this monitoring approach, based on readily available satellite-based time-series vegetation data, provides a valuable tool for assessing post-fire vegetation response.
Spatial and temporal characteristics of wildfires in Mississippi, USA
Authors: Grala Katarzyna , Cooke William H.
Published: February 2010

Forests constitute a large percentage of the total land area in Mississippi and are a vital element of the state economy. Although wildfire occurrences have been considerably reduced since the 1920s, there are still ~4000 wildfires each year in Mississippi burning over 24 000 ha (60 000 acres). This study focusses on recent history and various characteristics of Mississippi wildfires to provide better understanding of spatial and temporal characteristics of wildfires in the state. Geographic information systems and Mississippi Forestry Commission wildfire occurrence data were used to examine relationships between climatic and anthropogenic factors, the incidence, burned area, wildfire cause, and socioeconomic factors. The analysis indicated that wildfires are more frequent in southern Mississippi, in counties covered mostly by pine forest, and are most prominent in the winter–spring season. Proximity to roads and cities were two anthropogenic factors that had the most statistically significant correlation with wildfire occurrence and size. In addition, the validity of the Palmer Drought Severity Index as a measure of fire activity was tested for climatic districts in Mississippi. Analysis indicated that drought influences fire numbers and size during summer and fall (autumn). The strongest relationship between the Palmer Drought Severity Index and burned area was found for the southern climatic districts for the summer–fall season.
Assessing ignition probability and moisture of extinction in a Mediterranean grass fuel
Authors: Dimitrakopoulos A. P. , Mitsopoulos I. D. , Gatoulas K.
Published: February 2010

The objective of this study was the assessment of the probability of ignition and moisture of extinction of the annual herbaceous species Slender Oat (Avena barbata Pott. ex Link) in Greece. Multiple ignition tests were conducted in situ with a drip torch during two fire seasons, with simultaneous monitoring of the weather conditions. Stepwise logistic regression was applied to assess the probability of ignition based on plant moisture content and meteorological parameters. Fuel moisture content was determined to be the only statistically significant (P < 0.0001) parameter and, therefore, it was the only variable kept in the analysis. The logistic model correctly predicted fire ignition in 93.6% of the tests and 50% ignition probability was determined at 38.5% oven-dried weight (ODW) plant moisture content. Moisture of extinction (i.e. probability of ignition at 1%) was calculated at 55.5% ODW. Furthermore, classification tree analysis was applied to determine the independent variables that explain the variability in ignition probability. Wind speed was found to have an effect on ignition probability only at relatively high (>30% ODW) fuel moisture contents. Assessment of the ignition potential and moisture of extinction of grass fuels is a prerequisite for reliable fire danger prediction.
The effect of fuel age on the spread of fire in sclerophyll forest in the Sydney region of Australia
Authors: Price Owen F. , Bradstock Ross A.
Published: February 2010

We investigated the effect of fuel age on the truncation of spread of unplanned fires using a set of 1473 patches in the Sydney region of Australia. Twenty-two percent of patches derived from prescribed fire experienced a subsequent unplanned fire within 5 years, compared with 42% of patches derived from unplanned fires. Among those encounters, the subsequent unplanned fire stopped at the leading edge of 18% of prescribed patches and 11% of unplanned patches. In comparison, the subsequent fire stopped somewhere in the patch for 44% of both prescribed and unplanned fires. Overall, there was a 10% chance that a prescribed burn patch would experience an unplanned fire that stops within the patch. Statistical modelling revealed that the presence of a road barrier was the best predictor of the likelihood of stopping on the leading edge, but fuel age and weather also had an influence. Stopping on the trailing edge was less influenced by the variables analysed. In extreme weather, even 1-year-old patches have a low likelihood of stopping unplanned fires. Fuel age had little influence on the spread of unplanned fires. Consequently, prescribed fires will be most effective when sited at the urban interface where resultant reduced unplanned fire intensity will be a benefit.
Trust, acceptance, and citizen - agency interactions after large fires: influences on planning processes
Authors: Olsen Christine S. , Shindler Bruce A.
Published: February 2010

Wildfires have increased in number and size in recent years, making post-fire forest management an increasingly important topic. Citizen–agency interactions, citizen trust, and citizen acceptance of management strategies are central to successful planning and decision-making in these settings. In this study, citizen opinions from the attentive public are evaluated in two locations near recent fires in Oregon: the 2003 Bear and Booth Complex Fires and the 2002 Biscuit Fire. Results suggest an agency’s commitment to long-term interactions with citizens influences citizen trust in the agencies and acceptance of post-fire management strategies. There is broad acceptance for several post-fire management strategies (i.e. erosion control, replanting, reseeding). However, acceptance is highly dependent on trustworthy relations. Further, results suggest it is not enough to simply offer opportunities for public engagement; citizens need to feel that these activities were meaningful opportunities to participate. Although results differed between locations, overall the majority of respondents did not agree with how the local Forest Service and Bureau of Land Management handled forest planning after recent fires. Findings from this research indicate that positive citizen–agency relations need to be long-term and developed well before a fire occurs if post-fire actions are to be supported by communities.
Applying LiDAR technology for tree measurements in burned landscapes
Authors: Wing Michael G. , Eklund Aaron , Sessions John
Published: February 2010

Wildfires burn several million hectares in the United States annually. Time is critical in gathering information from burned landscapes for post-fire recovery planning. A technology to obtain spatial vegetation information across landscapes is Light Detecting and Ranging (LiDAR). We compared tree positional and height measurements, primarily from Douglas-fir (Pseudotsuga menziesii) and ponderosa pine (Pinus ponderosa), between field-based and LiDAR-derived measurements at three south-western Oregon (USA) sites. The sites represented a range of tree mortality from minimal to extensive. Our primary objective was to determine whether significant differences existed between field and LiDAR tree measurements in burned landscapes. Secondary objectives were to examine whether LiDAR pulse intensities in burned landscapes could differentiate coniferous from deciduous trees, discern fire-killed from live trees, and whether other tree measurement parameters were related to pulse intensities. No significant differences were detected between field-based and LiDAR-derived horizontal positions. Tree height differences between field-based and LiDAR measurements were significant at one site likely owing to dense canopy and measurement biases. Mean and maximum LiDAR intensities were significantly different between live and dead (fire-killed) trees in two of three sites. Additionally, crown diameter and tree sweep were significant in explaining variation in maximum LiDAR intensities at all sites.
Fire severity in a northern Australian savanna landscape: the importance of time since previous fire
Authors: Murphy Brett P. , Russell-Smith Jeremy
Published: February 2010

Using a detailed fire history collected over a 10-year period throughout a savanna landscape in northern Australia, we have addressed the question of whether fire severity, inferred from a semiquantitative fire severity index, increases with time since previous fire. There was a clear trend of fires becoming much more severe with increasing time since previous fire. Between 1 and 5 years following a fire, the probability of a subsequent fire being classified as ‘severe’ increased from 3 to 8% for early dry-season fires, and from 21 to 43% for late dry-season fires. It was clear that the strong increase in fire severity was not confined to the first 2–3 years following the previous fire, as previously suspected. These findings highlight the difficulty of reducing both fire frequency and severity in northern Australian savanna landscapes, as they imply that a negative feedback process exists between the two; that is, reducing fire frequency is likely to increase the severity of fires that do occur.
Subcellular dynamics of T cell immunological synapses and kinapses in lymph nodes
Authors: Azar Georges A. , Lemaître Fabrice , Robey Ellen A. , Bousso Philippe
Published: February 2010

In vitro studies have revealed that T cell activation occurs during the formation of either dynamic or stable interactions with antigen-presenting cells (APC), and the respective cell junctions have been referred to as immunological kinapses and synapses. However, the relevance and molecular dynamics of kinapses and synapses remain to be established in vivo. Using two-photon imaging, we tracked the distribution of LAT-EGFP molecules during antigen recognition by activated CD4+T cells in lymph nodes. At steady state, LAT-EGFP molecules were preferentially found at the uropod of rapidly migrating T cells. In contrast to naïve T cells that fully stopped upon systemic antigen delivery, recently activated T cells decelerated and formed kinapses, characterized by continuous extension of membrane protrusions and by the absence of persistent LAT-EGFP clustering. On the other hand, activated CD4+T cells formed stable immunological synapses with antigen-loaded B cells and displayed sustained accumulation of LAT-EGFP fluorescence at the contact zone. Our results show that the state of T cell activation and the type of APC largely influence T cell–APC contact dynamics in lymph nodes. Furthermore, we provide a dynamic look at immunological kinapses and synapses in lymph nodes and suggest the existence of distinct patterns of LAT redistribution during antigen recognition.
Local adaptation in Trinidadian guppies alters ecosystem processes
Authors: Bassar Ronald D. , Marshall Michael C. , López-Sepulcre Andrés , Zandonà Eugenia , Auer Sonya K. , Travis Joseph , Pringle Catherine M. , Flecker Alexander S. , Thomas Steven A. , Fraser Douglas F. , Reznick David N.
Published: February 2010

Theory suggests evolutionary change can significantly influence and act in tandem with ecological forces via ecological-evolutionary feedbacks. This theory assumes that significant evolutionary change occurs over ecologically relevant timescales and that phenotypes have differential effects on the environment. Here we test the hypothesis that local adaptation causes ecosystem structure and function to diverge. We demonstrate that populations of Trinidadian guppies (
Poecilia reticulata
), characterized by differences in phenotypic and population-level traits, differ in their impact on ecosystem properties. We report results from a replicated, common garden mesocosm experiment and show that differences between guppy phenotypes result in the divergence of ecosystem structure (algal, invertebrate, and detrital standing stocks) and function (gross primary productivity, leaf decomposition rates, and nutrient flux). These phenotypic effects are further modified by effects of guppy density. We evaluated the generality of these effects by replicating the experiment using guppies derived from two independent origins of the phenotype. Finally, we tested the ability of multiple guppy traits to explain observed differences in the mesocosms. Our findings demonstrate that evolution can significantly affect both ecosystem structure and function. The ecosystem differences reported here are consistent with patterns observed across natural streams and argue that guppies play a significant role in shaping these ecosystems.
Synergistic roles of the proteasome and autophagy for mitochondrial maintenance and chronological lifespan in fission yeast
Authors: Takeda Kojiro , Yoshida Tomoko , Kikuchi Sakura , Nagao Koji , Kokubu Aya , Pluskal Tomáš , Villar-Briones Alejandro , Nakamura Takahiro , Yanagida Mitsuhiro
Published: February 2010

Regulations of proliferation and quiescence in response to nutritional cues are important for medicine and basic biology. The fission yeast
Schizosaccharomyces pombe
serves as a model, owing to the shift of proliferating cells to the metabolically active quiescence (designate G0 phase hereafter) by responding to low nitrogen source.
S. pombe
G0 phase cells keep alive for months without growth and division. Nitrogen replenishment reinstates vegetative proliferation phase (designate VEG). Some 40 genes required for G0 maintenance were identified, but many more remain to be identified. We here show, using mutants, that the proteasome is required for maintaining G0 quiescence. Functional outcomes of proteasome in G0 and VEG phases appear to be distinct. Upon proteasome dysfunction, a number of antioxidant proteins and compounds responsive to ROS (reactive oxygen species) are produced. In addition, autophagy-mediated destruction of mitochondria occurs, which suppresses the loss of viability by eliminating ROS-generating mitochondria. These defensive responses are found in G0 but not in VEG, suggesting that the main function of proteasome in G0 phase homeostasis is to minimize ROS. Proteasome and autophagy are thus collaborative to support the lifespan of
S. pombe
G0 phase.
Prolonged sensory-selective nerve blockade
Authors: Sagie Itay , Kohane Daniel S.
Published: February 2010

Sensory-selective local anesthesia has long been a key goal in local anesthetic development. For example, it allows women to be pain-free during labor without compromising their ability to push. Here we show that prolonged sensory-selective nerve block can be produced by specific concentrations of surfactants—such as are used to enhance drug flux across skin—in combination with QX-314, a lidocaine derivative that has relative difficulty penetrating nerves. For example, injection of 25 mM QX-314 in 30 mM octyltrimethylammonium bromide (OTAB) lasted up to 7 h. Sensory selectivity was imparted to varying degrees by cationic, neutral, and anionic surfactants, and also was achieved with another lidocaine derivative, QX-222. Simultaneous injection of OTAB at a s.c. injection site remote from the sciatic nerve did not result in prolonged sensory-specific nerve blockade from QX-314, suggesting that the observed effect is due to a local interaction between the surfactant and the lidocaine derivative, not a systemic effect.
Inverted-U-shaped correlation between dopamine receptor availability in striatum and sensation seeking
Authors: Gjedde Albert , Kumakura Yoshitaka , Cumming Paul , Linnet Jakob , Møller Arne
Published: February 2010

Sensation seeking is a core personality trait that declines with age in both men and women, as do also both density and availability of the dopamine D2/3receptors in striatum and cortical regions. In contrast, novelty seeking at a given age relates inversely to dopamine receptor availability. The simplest explanation of these findings is an inverted-U-shaped correlation between ratings of sensation seeking on the Zuckerman scale and dopamine D2/3receptor availability. To test the claim of an inverted-U-shaped relation between ratings of the sensation-seeking personality and measures of dopamine receptor availability, we used PET to record [11C]raclopride binding in striatum of 18 healthy men. Here we report that an inverted-U shape significantly matched the receptor availability as a function of the Zuckerman score, with maximum binding potentials observed in the midrange of the scale. The inverted-U shape is consistent with a negative correlation between sensation seeking and the reactivity (“gain”) of dopaminergic neurotransmission to dopamine. The correlation reflects Zuckerman scores that are linearly linked to dopamine receptor densities in the striatum but nonlinearly linked to dopamine concentrations. Higher dopamine occupancy and dopamine concentrations explain the motivation that drives afflicted individuals to seek sensations, in agreement with reduced protection against addictive behavior that is characteristic of individuals with low binding potentials.
N
-acetylserotonin activates TrkB receptor in a circadian rhythm
Authors: Jang Sung-Wuk , Liu Xia , Pradoldej Sompol , Tosini Gianluca , Chang Qiang , Iuvone P. Michael , Ye Keqiang
Published: February 2010

Brain-derived neurotrophic factor (BDNF) is a cognate ligand for the TrkB receptor. BDNF and serotonin often function in a cooperative manner to regulate neuronal plasticity, neurogenesis, and neuronal survival. Here we show that NAS (
N
-acetylserotonin) swiftly activates TrkB in a circadian manner and exhibits antidepressant effect in a TrkB-dependent manner. NAS, a precursor of melatonin, is acetylated from serotonin by AANAT (
a
ryl
a
lkylamine
N
-
a
cetyl
t
ransferase). NAS rapidly activates TrkB, but not TrkA or TrkC, in a neurotrophin- and MT3 receptor-independent manner. Administration of NAS activates TrkB in BDNF knockout mice. Furthermore, NAS, but not melatonin, displays a robust antidepressant-like behavioral effect in a TrkB-dependent way. Endogenous TrkB is activated in wild-type C3H/f
+/+
mice but not in AANAT-mutated C57BL/6J mice, in a circadian rhythm; TrkB activation is high at night in the dark and low during the day. Hence, our findings support that NAS is more than a melatonin precursor, and that it can potently activate TrkB receptor.
Minimalist design of water-soluble cross-β architecture
Authors: Biancalana Matthew , Makabe Koki , Koide Shohei
Published: February 2010

Demonstrated successes of protein design and engineering suggest significant potential to produce diverse protein architectures and assemblies beyond those found in nature. Here, we describe a new class of synthetic protein architecture through the successful design and atomic structures of water-soluble cross-β proteins. The cross-β motif is formed from the lamination of successive β-sheet layers, and it is abundantly observed in the core of insoluble amyloid fibrils associated with protein-misfolding diseases. Despite its prominence, cross-β has been designed only in the context of insoluble aggregates of peptides or proteins. Cross-β’s recalcitrance to protein engineering and conspicuous absence among the known atomic structures of natural proteins thus makes it a challenging target for design in a water-soluble form. Through comparative analysis of the cross-β structures of fibril-forming peptides, we identified rows of hydrophobic residues (“ladders”) running across β-strands of each β-sheet layer as a minimal component of the cross-β motif. Grafting a single ladder of hydrophobic residues designed from the Alzheimer’s amyloid-β peptide onto a large β-sheet protein formed a dimeric protein with a cross-β architecture that remained water-soluble, as revealed by solution analysis and x-ray crystal structures. These results demonstrate that the cross-β motif is a stable architecture in water-soluble polypeptides and can be readily designed. Our results provide a new route for accessing the cross-β structure and expanding the scope of protein design.
Sex determines the expression level of one third of the actively expressed genes in bovine blastocysts
Authors: Bermejo-Alvarez P. , Rizos D. , Rath D. , Lonergan P. , Gutierrez-Adan A.
Published: February 2010

Although genetically identical for autosomal Chrs (Chr), male and female preimplantation embryos could display sex-specific transcriptional regulation. To illustrate sex-specific differences at the mRNA level, we compared gene-expression patterns between male and female blastocysts by DNA microarray comparison of nine groups of 60 bovine in vitro-produced blastocysts of each sex. Almost one-third of the transcripts detected showed sexual dimorphism (2,921 transcripts; false-discovery rate,
P
< 0.05), suggesting that in the absence of hormonal influences, the sex Chrs impose an extensive transcriptional regulation upon autosomal genes. Six genes were analyzed by qPCR in in vivo-derived embryos, which displayed similar sexual dimorphism. Ontology analysis suggested a higher global transcriptional level in females and a more active protein metabolism in males. A gene homolog to an X-linked gene involved in network interactions during spliceosome assembly was found in the Y-Chr. Most of the X-linked-expressed transcripts (88.5%) were up-regulated in females, but most of them (70%) exhibited fold-changes lower than 1.6, suggesting that X-Chr inactivation is partially achieved at the blastocyst stage. Almost half of the transcripts up-regulated in female embryos exhibiting more than 1.6-fold change were present in the X-Chr and eight of them were selected to determine a putative paternal imprinting by gene expression comparison with parthenogenetic embryos. Five (
BEX
,
CAPN6
,
BEX2
,
SRPX2
, and
UBE2A
) exhibited a higher expression in females than in parthenotes, suggesting that they are predominantly expressed by the paternal inherited X-Chr and that imprinting may increase the transcriptional skew caused by double X-Chr dosage.
MYC regulation of a “poor-prognosis” metastatic cancer cell state
Authors: Wolfer Anita , Wittner Ben S. , Irimia Daniel , Flavin Richard J. , Lupien Mathieu , Gunawardane Ruwanthi N. , Meyer Clifford A. , Lightcap Eric S. , Tamayo Pablo , Mesirov Jill P. , Liu X. Shirley , Shioda Toshi , Toner Mehmet , Loda Massimo , Brown Myles , Brugge Joan S. , Ramaswamy Sridhar
Published: February 2010

Gene expression signatures are used in the clinic as prognostic tools to determine the risk of individual patients with localized breast tumors developing distant metastasis. We lack a clear understanding, however, of whether these correlative biomarkers link to a common biological network that regulates metastasis. We find that the c-MYC oncoprotein coordinately regulates the expression of 13 different “poor-outcome” cancer signatures. In addition, functional inactivation of MYC in human breast cancer cells specifically inhibits distant metastasis in vivo and invasive behavior in vitro of these cells. These results suggest that MYC oncogene activity (as marked by “poor-prognosis” signature expression) may be necessary for the translocation of poor-outcome human breast tumors to distant sites.
Dynamic regulation of functionally distinct virus-specific T cells
Authors: Ndhlovu Zaza M. , Oelke Mathias , Schneck Jonathan P. , Griffin Diane E.
Published: February 2010

The functional capacities of CD8+T cells important for virus clearance are influenced by interactions with antigen presenting cells (APCs) and CD4+T cells during initial selection, subsequent expansion, and development of memory. Recently, investigators have shown that polyfunctional T cells correlate best with long-term protection, however, it is still unknown how to stimulate T cells to achieve these responses. To study this, we examined the phenotypes and functions of CD8+T cells specific for two different virus antigens stimulated ex vivo using either autologous monocyte-derived dendritic cells (moDCs) or HLA-A2-Ig-based artificial APCs (aAPCs). Although similar numbers of influenza virus and measles virus tetramer-positive cells were generated by stimulation with peptide-loaded moDCs and aAPCs, T cell function, assessed by expression of IL-2, IFN-γ, TNF-α, MIP1β, and CD107a, showed that aAPC-generated CD8+T cells were multifunctional, whereas moDC-generated cells were mostly monofunctional. aAPC-generated cells also produced more of each cytokine per cell than CD8+T cells generated with moDCs. These phenotypes were not fixed, as changing the culture conditions of expanding T cells from aAPCs to moDCs, and moDCs to aAPCs, reversed the phenotypes. We conclude that CD8+T cells are heterogeneous in their functionality and that this is dependent, in a dynamic way, on the stimulating APC. These studies will lead to understanding the factors that influence induction of optimal CD8+T cell function.
Representational gain in cortical area underlies increase of memory strength
Authors: Bieszczad Kasia M. , Weinberger Norman M.
Published: February 2010

Neuronal plasticity that develops in the cortex during learning is assumed to represent memory content, but the functions of such plasticity are actually unknown. The shift in spectral tuning in primary auditory cortex (A1) to the frequency of a tone signal is a compelling candidate for a substrate of memory because it has all of the cardinal attributes of associative memory: associativity, specificity, rapid induction, consolidation, and long-term retention. Tuning shifts increase the representational area of the signal in A1, as an increasing function of performance level, suggesting that area encodes the magnitude of acquired stimulus significance. The present study addresses the question of the specific function of learning-induced associative representational plasticity. We tested the hypothesis that specific increases in A1 representational area for an auditory signal serve the mnemonic function of enhancing memory strength for that signal. Rats were trained to bar-press for reward contingent on the presence of a signal tone (5.0 kHz), and assessed for memory strength during extinction. The amount of representational area gain for the signal frequency band was significantly positively correlated with resistance to extinction to the signal frequency in two studies that spanned the range of task difficulty. These findings indicate that specific gain in cortical representational area underlies the strength of the behaviorally-relevant contents of memory. Thus, mnemonic functions of cortical plasticity are determinable.
Physiological and Emotional Responses of Disabled Children to Therapeutic Clowns: A Pilot Study
Authors: Kingsnorth Shauna , Blain Stefanie , McKeever Patricia
Published: February 2010

This pilot study examined the effects of Therapeutic Clowning on inpatients in a pediatric rehabilitation hospital. Ten disabled children with varied physical and verbal expressive abilities participated in all or portions of the data collection protocol. Employing a mixed‐method, single‐subject ABAB study design, measures of physiological arousal, emotion and behavior were obtained from eight children under two conditions—television exposure and therapeutic clown interventions. Four peripheral autonomic nervous system (ANS) signals were recorded as measures of physiological arousal; these signals were analyzed with respect to measures of emotion (verbal self reports of mood) and behavior (facial expressions and vocalizations). Semistructured interviews were completed with verbally expressive children (n = 7) and nurses of participating children (n = 13). Significant differences among children were found in response to the clown intervention relative to television exposure. Physiologically, changes in ANS signals occurred either more frequently or in different patterns. Emotionally, children′s (self) and nurses′ (observed) reports of mood were elevated positively. Behaviorally, children exhibited more positive and fewer negative facial expressions and vocalizations of emotion during the clown intervention. Content and themes extracted from the interviews corroborated these findings. The results suggest that this popular psychosocial intervention has a direct and positive impact on hospitalized children. This pilot study contributes to the current understanding of the importance of alternative approaches in promoting well‐being within healthcare settings.
Ocean currents help explain population genetic structure
Authors: White Crow , Selkoe Kimberly A. , Watson James , Siegel David A. , Zacherl Danielle C. , Toonen Robert J.
Published: February 2010

Management and conservation can be greatly informed by considering explicitly how environmental factors influence population genetic structure. Using simulated larval dispersal estimates based on ocean current observations, we demonstrate how explicit consideration of frequency of exchange of larvae among sites via ocean advection can fundamentally change the interpretation of empirical population genetic structuring as compared with conventional spatial genetic analyses. Both frequency of larval exchange and empirical genetic difference were uncorrelated with Euclidean distance between sites. When transformed into relative oceanographic distances and integrated into a genetic isolation-by-distance framework, however, the frequency of larval exchange explained nearly 50 per cent of the variance in empirical genetic differences among sites over scales of tens of kilometres. Explanatory power was strongest when we considered effects of multiple generations of larval dispersal via intermediary locations on the long-term probability of exchange between sites. Our results uncover meaningful spatial patterning to population genetic structuring that corresponds with ocean circulation. This study advances our ability to interpret population structure from complex genetic data characteristic of high gene flow species, validates recent advances in oceanographic approaches for assessing larval dispersal and represents a novel approach to characterize population connectivity at small spatial scales germane to conservation and fisheries management.
Empyema due to a highly transmissible Pseudomonas aeruginosa strain in an adult cystic fibrosis patient
Authors: Mohan Kamlesh , Lakshman Vinay , Fothergill Joanne L. , Ledson Martin J. , Winstanley Craig , Walshaw Martin J.
Published: February 2010

Chronic pulmonary infection with Pseudomonas aeruginosa occurs in up to 85 % of individuals with cystic fibrosis (CF) by the time they reach adulthood, and is the major cause of morbidity and mortality: nearly all patients die from progressive respiratory failure due to repeated pulmonary exacerbations. However, despite the predilection of this organism for the lungs of CF people, infection of the pleura is much less common and is not well described in the CF population. We describe what is believed to be the first case of pleural empyema due to a particularly pathogenic transmissible strain of P. aeruginosa (the Liverpool epidemic strain) in an adult CF patient.
Protein-losing enteropathy and hypogammaglobulinaemia as first manifestations of disseminated histoplasmosis coincident with Nocardia infection
Authors: Kok Jen , Chen Sharon C. A. , Anderson Lyndal , Berglund Lucinda , Sleiman Sue , Moss Alan , Bourke Michael , Fulcher David , Gilroy Nicole
Published: February 2010

Disseminated histoplasmosis and nocardiosis typically affect immunocompromised hosts. We report a case of gastrointestinal and adrenal histoplasmosis, presenting as protein-losing enteropathy and hypogammaglobulinaemia, coincident with Nocardia infection, in a HIV-negative patient in whom a specific immunological defect could not be identified. Clinicians in areas of non-endemicity should be vigilant for rare manifestations of histoplasmosis.