bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure, compressibility factor, and dynamics of highly size-asymmetric binary hard-disk liquids
Authors: Xu Wen-Sheng , Sun Zhao-Yan , An Li-Jia
Published: September 2012

By using event-driven molecular dynamics simulation, we investigate effects of varying the area fraction of the smaller component on structure, compressibility factor, and dynamics of the highly size-asymmetric binary hard-disk liquids. We find that the static pair correlations of the large disks are only weakly perturbed by adding small disks. The higher-order static correlations of the large disks, by contrast, can be strongly affected. Accordingly, the static correlation length deduced from the bond-orientation correlation functions first decreases significantly and then tends to reach a plateau as the area fraction of the small disks increases. The compressibility factor of the system first decreases and then increases upon increasing the area fraction of the small disks and separating different contributions to it allows to rationalize this non-monotonic phenomenon. Furthermore, adding small disks can influence dynamics of the system in quantitative and qualitative ways. For the large disks, the structural relaxation time increases monotonically with increasing the area fraction of the small disks at low and moderate area fractions of the large disks. In particular, “reentrant” behavior appears at sufficiently high area fractions of the large disks, strongly resembling the reentrant glass transition in short-ranged attractive colloids and the inverted glass transition in binary hard spheres with large size disparity. By tuning the area fraction of the small disks, relaxation process for the small disks shows concave-to-convex crossover and logarithmic decay behavior, as found in other binary mixtures with large size disparity. Moreover, diffusion of both species is suppressed by adding small disks. Long-time diffusion for the small disks shows power-law-like behavior at sufficiently high area fractions of the small disks, which implies precursors of a glass transition for the large disks and a localization transition for the small disks. Therefore, our results demonstrate the generic dynamic features in highly size-asymmetric binary mixtures.
Relationship between mesoscale dynamics and shear relaxation of ionic liquids with long alkyl chain
Authors: Yamaguchi Tsuyoshi , Mikawa Ken-ichi , Koda Shinobu , Fujii Kenta , Endo Hitoshi , Shibayama Mitsuhoro , Hamano Hiroshi , Umebayashi Yasuhiro
Published: September 2012

The shear relaxation spectra of three imidazolium-based ionic liquids, 1-methyl-3-octylimidazolium chloride ([C8mim][Cl]), 1-methyl-3-octylimidazolium hexafluorophosphate ([C8mim][PF6]), and 1-dodecyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([C12mim][TFSA]) were measured and compared with the intermediate scattering functions determined with neutron spin echo (NSE) spectroscopy. The shear relaxation is slower than that predicted from the relaxation of the main peak of the structure factor that is common to other molecular liquids, whereas it is faster than that from the relaxation of the pre-peak, that corresponds to the correlation length of about 10 nm specific to ionic liquids with an intermediately long alkyl chain. The role of the pre-peak structure in the mechanism of shear viscosity of ionic liquids is discussed based on the comparison between NSE and shear relaxations.
Multiple implantation and multiple annealing of phosphorus doped germanium to achieve n-type activation near the theoretical limit
Authors: Kim Jeehwan , Bedell Stephen W. , Sadana Devendra K.
Published: September 2012

Full activation of n-type dopant in germanium (Ge) reaching to its solid solubility has never been achieved by using ion implantation doping technique. This is because implantation of dopants always leaves defects such as vacancy and interstitials in the Ge crystal. While implantation-induced defects are electrically neutral for the most of semiconductor materials, they are electrically positive for Ge resulting in compensation of n-type dopants. In this Letter, we verified that 5 × 1019 P/cm3 is the maximum active concentration, which can be fully activated in germanium “without leaving implantation damage” per implantation/annealing cycle. The repetition of implantation and annealing of phosphorous (P) with the concentration of 5 × 1019 cm−3 leads to the activation of 1 × 1020 P/cm3 close to its solid solubility limit of 2 × 1020 P/cm3.
Consequences of plasma rotation for neoclassical tearing mode suppression by electron cyclotron current drive
Authors: Ayten B. , Westerhof E.
Published: September 2012

In the generalized Rutherford equation describing the nonlinear evolution of the width of the magnetic island associated with a neoclassical tearing mode, the effect of localized current drive is represented by a term ΔCD′. We investigate oscillations in ΔCD′ originating from the rotation of the island through the electron cyclotron power deposition region and their dependence on the collisional time scale on which the driven current is generated, the rotation period, the island size, and the power deposition width. Furthermore, their consequences for the island growth or the stabilization are analyzed. This work shows that the net result of the oscillations in ΔCD′ is a slight increase in the stabilizing effect of electron cyclotron current drive and consequently, a reduction in the minimum power requirement to fully suppress an island.
Damage detection via Joule effect for multidirectional carbon fiber reinforced composites
Authors: Athanasopoulos N. , Kostopoulos V.
Published: September 2012

The electrical conductivity of a thin multidirectional carbon fiber reinforced composite laminates can be expressed by an equivalent symmetric second order tensor. Any change of the microstructure of the composite laminate due to an interlaminar damage locally changes the electrical conductivity tensor of the medium. Applying electric potential difference, the temperature of the medium rises, due to the Joule effect. In the presence of interlaminar damage, the developed temperature field changes locally. Following the coupled electrical/thermal solution of the problem, the mechanism of the phenomenon is elucidated and validated against experimental results by comparing the measured to calculated temperature field.
Experimental observations of turbulent mixing due to Kelvin–Helmholtz instability on the OMEGA Laser Facility
Authors: Smalyuk V. A. , Hansen J. F. , Hurricane O. A. , Langstaff G. , Martinez D. , Park H.-S. , Raman K. , Remington B. A. , Robey H. F. , Schilling O. , Wallace R. , Elbaz Y. , Shimony A. , Shvarts D. , Di Stefano C. , Drake R. P. , Marion D. , Krauland C. M. , Kuranz C. C.
Published: September 2012

Shear-flow, Kelvin–Helmholtz (KH) turbulent mixing experiments were performed on the OMEGA Laser Facility [Boehly et al., Opt. Commun. 133, 495 (1997)] in which laser-driven shock waves propagated through a low-density plastic foam placed on top of a higher-density plastic foil. The plastic foil was comprised a thin iodine-doped plastic tracer layer bonded on each side to an undoped density-matched polyamide-imide plastic. Behind the shock front, lower-density foam plasma flowed over the higher-density plastic plasma, such that the interface between the foam and plastic was KH unstable. The initial perturbations consisted of pre-imposed, sinusoidal 2D perturbations, and broadband 3D perturbations due to surface roughness at the interface between the plastic and foam. KH instability growth was measured using side-on radiography with a point-projection 5-keV vanadium backlighter. Time-integrated images were captured on D-8 x-ray film. Spatial density profiles of iodine-doped plastic mixed with foam were inferred using x-ray radiographs. The mixing layer ensuing from the KH instability with layer width up to ∼100 μm was observed at a location ∼1 mm behind the shock front. The measured mixing layer width was in good agreement with predictions based on a simple self-similar model of KH instability growth using an estimate of the shear velocity obtained from numerical simulations of the experiments.
Density and temperature effects on Compton scattering in plasmas
Authors: Kumar Ravindra , Ravishankar V. , Krishan V.
Published: September 2012

We study the effect of the density and temperature on Compton scattering in a plasma, with particular emphasis on the quality of the scattered electron beam. We find that the longitudinal mode in the plasma plays a dominant role in producing collimated and mono-energetic electron spectrum. The beam profile is, however, sensitive to the plasma parameters such as its density and temperature. We make a careful study of this sensitivity and distinguish regions in the parameter space in which the quality of the beam profile is good from the regions in which it is poor. These findings are potentially useful in understanding the physics of laser plasma accelerators.
Simulative research on the expansion of cathode plasma in high-current electron beam diode
Authors: Xu Qifu , Liu Lie
Published: September 2012

The expansion of cathode plasma has long been recognized as a limiting factor in the impedance lifetime of high-current electron beam diode. Realistic modeling of such plasma is of great necessity in order to discuss the dynamics of cathode plasma. Using the method of particle-in-cell, the expansion of cathode plasma is simulated in this paper by a scaled-down diode model. It is found that the formation of cathode plasma increases the current density in the diode. This consequently leads to the decrease of the potential at plasma front. Once the current density has been increased to a certain value, the potential at plasma front would then be equal to or lower than the plasma potential. Then the ions would move towards the anode, and the expansion of cathode plasma is thereby formed. Different factors affecting the plasma expansion velocity are discussed in this paper. It is shown that the decrease of proton genatation rate has the benefit of reducing the plasma expansion velocity.
The transport of relative canonical helicity
Authors: You S.
Published: September 2012

The evolution of relative canonical helicity is examined in the two-fluid magnetohydrodynamic formalism. Canonical helicity is defined here as the helicity of the plasma species’ canonical momentum. The species’ canonical helicity are coupled together and can be converted from one into the other while the total gauge-invariant relative canonical helicity remains globally invariant. The conversion is driven by enthalpy differences at a surface common to ion and electron canonical flux tubes. The model provides an explanation for why the threshold for bifurcation in counter-helicity merging depends on the size parameter. The size parameter determines whether magnetic helicity annihilation channels enthalpy into the magnetic flux tube or into the vorticity flow tube components of the canonical flux tube. The transport of relative canonical helicity constrains the interaction between plasma flows and magnetic fields, and provides a more general framework for driving flows and currents from enthalpy or inductive boundary conditions.
A statistical analysis of avalanching heat transport in stationary enhanced core confinement regimes
Authors: Tokunaga S. , Jhang Hogun , Kim S. S. , Diamond P. H.
Published: September 2012

We present a statistical analysis of heat transport in stationary enhanced confinement regimes obtained from flux-driven gyrofluid simulations. The probability density functions of heat flux in improved confinement regimes, characterized by the Nusselt number, show significant deviation from Gaussian, with a markedly fat tail, implying the existence of heat avalanches. Two types of avalanching transport are found to be relevant to stationary states, depending on the degree of turbulence suppression. In the weakly suppressed regime, heat avalanches occur in the form of quasi-periodic (QP) heat pulses. Collisional relaxation of zonal flow is likely to be the origin of these QP heat pulses. This phenomenon is similar to transient limit cycle oscillations observed prior to edge pedestal formation in recent experiments. On the other hand, a spectral analysis of heat flux in the strongly suppressed regime shows the emergence of a 1/f (f is the frequency) band, suggesting the presence of self-organized criticality (SOC)-like episodic heat avalanches. This episodic 1/f heat avalanches have a long temporal correlation and constitute the dominant transport process in this regime.
Photoconduction efficiencies and dynamics in GaN nanowires grown by chemical vapor deposition and molecular beam epitaxy: A comparison study
Authors: Chen R. S. , Tsai H. Y. , Huang Y. S. , Chen Y. T. , Chen L. C. , Chen K. H.
Published: September 2012

The normalized gains, which determines the intrinsic photoconduction (PC) efficiencies, have been defined and compared for the gallium nitride (GaN) nanowires (NWs) grown by chemical vapor deposition (CVD) and molecular beam epitaxy (MBE). By excluding the contributions of experimental parameters and under the same light intensity, the CVD-grown GaN NWs exhibit the normalized gain which is near two orders of magnitude higher than that of the MBE-ones. The temperature-dependent time-resolved photocurrent measurement further indicates that the higher photoconduction efficiency in the CVD-GaN NWs is originated from the longer carrier lifetime induced by the higher barrier height (ϕB = 160 ± 30 mV) of surface band bending. In addition, the experimentally estimated barrier height at 20 ± 2 mV for the MBE-GaN NWs, which is much lower than the theoretical value, is inferred to be resulted from the lower density of charged surface states on the non-polar side walls.
Effect of trapping in a degenerate plasma in the presence of a quantizing magnetic field
Authors: Shah H. A. , Iqbal M. J. , Tsintsadze N. , Masood W. , Qureshi M. N. S.
Published: September 2012

Effect of trapping as a microscopic phenomenon in a degenerate plasma is investigated in the presence of a quantizing magnetic field. The plasma comprises degenerate electrons and non-degenerate ions. The presence of the quantizing magnetic field is discussed briefly and the effect of trapping is investigated by using the Fermi-Dirac distribution function. The linear dispersion relation for ion acoustic wave is derived in the presence of the quantizing magnetic field and its influence on the propagation characteristics of the linear ion acoustic wave is discussed. Subsequently, fully nonlinear equations for ion acoustic waves are used to obtain the Sagdeev potential and the investigation of solitary structures. The formation of solitary structures is studied both for fully and partially degenerate plasmas in the presence of a quantizing magnetic field. Both compressive and rarefactive solitons are obtained for different conditions of temperature and magnetic field.
Electrical transport properties of individual WS2 nanotubes and their dependence on water and oxygen absorption
Authors: Zhang Chaoying , Ning Zhiyuan , Liu Yang , Xu Tingting , Guo Yao , Zak Alla , Zhang Zhiyong , Wang Sheng , Tenne Reshef , Chen Qing
Published: September 2012

The electrical properties of WS2 nanotubes (NTs) were studied through measuring 59 devices. Important electrical parameters, such as the carrier concentration, mobility, and effective barrier height at the contacts, were obtained through fitting experimental non-linear I-V curves using a metal-semiconductor-metal model. The carrier mobility was found to be several orders of magnitude higher than that have been reported previously for WS2 NTs. Water absorption was found to decrease the conductivity and carrier mobility of the NTs, and could be removed when the sample was dried. Oxygen absorption also slightly decreased the conductivity of WS2 NTs.
Coherent terahertz radiation from high-harmonic component of modulated free-electron beam in a tapered two-asymmetric grating structure
Authors: Zhang Ya-Xin , Zhou Yu-Cong , Dong Liang , Liu Sheng-Gang
Published: September 2012

Based on the mechanism of incoherent diffraction radiation excited by an electron bunch in a waveguide with periodic structure, this paper presents the concept of coherent terahertz (THz) radiation from the high-harmonic component of a modulated free-electron beam in a tapered two-asymmetric grating structure. The results show that in this mechanism 0.43 THz radiation can be generated with 10 A/cm2 current density, and the efficiency can reach 0.5%. Because of the low required current density and relative high efficiency, this concept shows the application potential for electron-beam-driven terahertz sources.
Electronic properties of annealed pentacene films in air at various temperatures up to 400 K
Authors: Tsao Hou-Yen , Lin Yow-Jon
Published: September 2012

This study examined the electronic properties of annealed pentacene films in air at various temperatures up to 400 K for 1 min. The carrier mobility in pentacene samples exhibits unexpectedly strong temperature dependence, implying the domination of tunneling (hopping) at low (high) temperatures. Upon annealing temperature, the molecule structure is not affected. The room-temperature mobility was drastically increased from 2.42 to 4.73 cm2/V-s by thermal annealing at 350 K. Hall-effect analysis by using the polaron theory revealed that the enhanced mobility by proper annealing is due to the increased spacing between molecules.
On the onset of the plasmoid instability
Authors: Baty H.
Published: September 2012

A numerical study of magnetic reconnection in two-dimensional resistive magnetohydrodynamics for marginally unstable Sweet-Parker current sheets that are subject to plasmoid formation is carried out. Despite the procedure used to form the primary Sweet-Parker-like current layer, that is different with respect to previous studies, the reconnection layer is unstable to the plasmoid instability for a Lundquist number greater than the expected critical value Sc≈104. For Lundquist numbers S≳Sc, the instability exhibits a quasi-periodic behaviour consisting of formation, rapid growth, and evacuation of a moving magnetic island. The so called “plasmoid” breaks up the primary current layer and significantly enhances the maximum current density over the value expected from Sweet-Parker theory. This local enhancement spatially coincides with the downstream X-point of the magnetic island and is associated with the formation of a pair of slow-mode Petschek-like shocks bounding the outflowing plasma. These results suggest that the inter-plasmoid current layers forming in high-Lundquist-number plasmas (S≫Sc) could not be simply described as marginally stable Sweet-Parker current sheets.
Studies on atomic layer deposition Al2O3/In0.53Ga0.47As interface formation mechanism based on air-gap capacitance-voltage method
Authors: Yoshida Toshiyuki , Hashizume Tamotsu
Published: September 2012

The air-gap capacitance-voltage characteristics of InGaAs surfaces were measured after 1-, 2-, 6-, 9-, and 17-cycle atomic layer deposition (ALD) Al2O3 processing. A high density of mid-gap states was found to be generated and increased during these ALD process steps, while the native oxide component was reduced. On the other hand, the mid-gap state density was drastically reduced after the usual annealing process. The generation of the mid-gap states seemed to be relevant to a non-stoichiometric Al-oxide component associated with a deficit in oxygen atoms, which became re-oxidized during the annealing process.
Contrapuntal Urbanisms: Towards a Postcolonial Relational Geography
Authors: O'Callaghan Cian
Published: September 2012

Relational geography has reformulated how we study cities, but has reiterated perennial problems in the discipline between the utility of theory and the complex realities it purports to represent. I argue that by constructing this problem as a dialogue between urban and postcolonial studies, we can find better ways to understand this frustration and reflexively engage with it. Through reworking Edward Said's ‘contrapuntal’ perspective, I propose a relational urban geography which is more sensitive to the ontological limitations of theory, and which takes a provisional approach to conceptualising and writing about cities. I then illustrate these propositions through a contrapuntal reading of recent redevelopment in Cork, Ireland.
The future of grain legumes in cropping systems
Authors: Sinclair Thomas R. , Vadez Vincent
Published: September 2012

Grain legume production is increasing worldwide due to their use directly as human food, feed for animals, and industrial demands. Further, grain legumes have the ability to enhance the levels of nitrogen and phosphorus in cropping systems. Considering the increasing needs for human consumption of plant products and the economic constraints of applying fertiliser on cereal crops, we envision a greater role for grain legumes in cropping systems, especially in regions where accessibility and affordability of fertiliser is an issue. However, for several reasons the role of grain legumes in cropping systems has often received less emphasis than cereals. In this review, we discuss four major issues in increasing grain legume productivity and their role in overall crop production: (i) increased symbiotic nitrogen fixation capacity, (ii) increased phosphorus recovery from the soil, (iii) overcoming grain legume yield limitations, and (iv) cropping systems to take advantage of the multi-dimensional benefits of grain legumes.
The extent and cost of mallee - crop competition in unharvested carbon sequestration and harvested mallee biomass agroforestry systems
Authors: Sudmeyer R. A. , Daniels T. , Jones H. , Huxtable D.
Published: September 2012

Mallee-based agroforestry has potential to provide farmers with new income sources derived from biofuels, biofeedstocks, and carbon sequestration. Although mallees are planted on >12 700 ha across the south-west of Western Australia, very little commercial harvesting of mallee has occurred to date. The development of biomass processing industries is constrained by lack of robust information regarding the productivity of integrated mallee and agricultural systems. This study addresses this constraint by quantifying the productivity and economics of agricultural crops and pastures growing in the competition zone adjacent to mallee belts at 15 sites across the Western Australian wheatbelt. The sites covered a range of climate and edaphic conditions, three mallee species (Eucalyptus polybractea R Baker, E. loxophleba ssp. lissophloia LAS Johnson and KD Hill, or E. kochii ssp. plenissima (CA Gardner) Brooker), various crop and pasture rotations, and various mallee harvest-management treatments.
Mallee–crop competition was negatively correlated with rainfall and positively correlated with mallee age and size, and greater for crops than pasture. Consequently, extent and magnitude of competition were highly variable across sites and years. On average, mallee–crop competition extended 11.3 m from unharvested belts and reduced crop and pasture yields by 36% within 2–20 m of the mallee belts relative to open paddock yields. This is similar to what has been reported for taller tree species. Harvesting mallees reduced competition such that crop and pasture yield was reduced by 22 or 27% relative to open paddock yields for mallees harvested at 3- or 6+-year intervals, respectively.
The economic cost of mallee–crop competition on agricultural enterprises was also highly variable between sites, and between years within individual sites. Averaged across all site-years, the opportunity cost of competition was equivalent to forgoing agricultural production for 14.4 m on each side of unharvested mallee belts, or 9–10 m on each side of harvested belts.
Farmers with mallee agroforestry systems will need to manage the economic impacts of competition by reducing agricultural input costs in the competition zone, timing crop-grazing rotations with mallee harvests, ensuring that the width of alleys is at least 25 times the height of the mature trees, and possibly root-pruning mallees in unharvested or long harvest interval systems.
This research has shown that mallee–crop competition presents a significant cost to farmers and must be considered when designing mallee agroforestry systems. The findings have relevance for the development of appropriate biomass and carbon sequestration pricing benchmarks for mallee plantings.
The effects of personal experience on choice-based preferences for wildfire protection programs
Authors: Holmes Thomas P. , González-Cabán Armando , Loomis John , Sánchez José
Published: September 2012

In this paper, we investigate homeowner preferences and willingness to pay for wildfire protection programs using a choice experiment with three attributes: risk, loss and cost. Preference heterogeneity among survey respondents was examined using three econometric models and risk preferences were evaluated by comparing willingness to pay for wildfire protection programs against expected monetary losses. The results showed that while nearly all respondents had risk seeking preferences, a small segment of respondents were risk neutral or risk averse. Only respondents who had personal experience with the effects of wildfire consistently made trade-offs among risk, loss and cost and these respondents were willing to pay more for wildfire protection programs than were respondents without prior experience of the effects of wildfire. The degree to which people with prior experience with the effects of wildfire can effectively articulate an economic rationale for investing in wildfire protection to other members of their own or other communities facing the threat of wildfires may influence the overall success of wildfire protection programs.
Selective requirement for Mediator MED23 in Ras-active lung cancer
Authors: Yang Xu , Zhao Meng , Xia Min , Liu Yuting , Yan Jun , Ji Hongbin , Wang Gang
Published: September 2012

K-RAS
–activating mutations occur frequently in non-small cell lung cancer, leading to aberrant activation of the Ras–MAPK signaling pathway that contributes to the malignant phenotype. However, the development of Ras-targeted therapeutics remains challenging. Here, we show that MED23, a component of the multisubunit Mediator complex that is known to integrate signaling and gene activities, is selectively important for Ras-active lung cancer. By screening a large panel of human lung cancer cell lines with or without a Ras mutation, we found that
Med23
RNAi specifically inhibits the proliferation and tumorigenicity of lung cancer cells with hyperactive Ras activity.
Med23
deficiency in fibroblasts selectively inhibited the oncogenic transformation induced by Ras but not by c-Myc. The transcription factor ELK1, which is phosphorylated by MAPK for relaying Ras signaling to MED23, also was required for the Ras-driven oncogenesis. Transcriptome analysis revealed that MED23 and ELK1 co-regulate a common set of target genes enriched in regulating cell-cycle and -proliferation functions to support the Ras dependency. Furthermore, MED23 was up-regulated by Ras transformation in correlation with the strength of Ras signaling as indicated by the ELK1 phosphorylation level and was found to be overexpressed in both Ras-mutated lung cancer cell lines and primary tumor samples. Remarkably, lower
Med23
expression predicted better survival in Ras-active lung cancer patients and xenograft mice. Collectively, our findings demonstrate a critical role for MED23 in enabling the “Ras-addiction” of lung carcinogenesis, thus providing a vulnerable target for the treatment of Ras-active lung cancer.
Aberrantly elevated microRNA-34a in obesity attenuates hepatic responses to FGF19 by targeting a membrane coreceptor β-Klotho
Authors: Fu Ting , Choi Sung-E , Kim Dong-Hyun , Seok Sunmi , Suino-Powell Kelly M. , Xu H. Eric , Kemper Jongsook Kim
Published: September 2012

MicroRNA-34a (miR-34a) is the most highly elevated hepatic miR in obese mice and is also substantially elevated in patients who have steatosis, but its role in obesity and metabolic dysfunction remains unclear. After a meal, FGF19 is secreted from the ileum; binds to a hepatic membrane receptor complex, FGF19 receptor 4 and coreceptor β-Klotho (βKL); and mediates postprandial responses under physiological conditions, but hepatic responses to FGF19 signaling were shown to be impaired in patients with steatosis. Here, we show an unexpected functional link between aberrantly elevated miR-34a and impaired βKL/FGF19 signaling in obesity. In vitro studies show that miR-34a down-regulates βKL by binding to the 3′ UTR of βKL mRNA. Adenoviral-mediated overexpression of miR-34a in mice decreased hepatic βKL levels, impaired FGF19-activated ERK and glycogen synthase kinase signaling, and altered expression of FGF19 metabolic target genes. Consistent with these results, βKL levels were decreased and hepatic responses to FGF19 were severely impaired in dietary obese mice that have elevated miR-34a. Remarkably, in vivo antisense inhibition of miR-34a in obese mice partially restored βKL levels and improved FGF19 target gene expression and metabolic outcomes, including decreased liver fat. Further, anti–miR-34a treatment in primary hepatocytes of obese mice restored FGF19-activated ERK and glycogen synthase kinase signaling in a βKL-dependent manner. These results indicate that aberrantly elevated miR-34a in obesity attenuates hepatic FGF19 signaling by directly targeting βKL. The miR-34a/βKL/FGF19 axis may present unique therapeutic targets for FGF19-related human diseases, including metabolic disorders and cancer.
α-Synuclein disrupts stress signaling by inhibiting polo-like kinase Cdc5/Plk2
Authors: Wang Shaoxiao , Xu Baoshan , Liou Liang-Chun , Ren Qun , Huang Shile , Luo Yan , Zhang Zhaojie , Witt Stephan N.
Published: September 2012

Parkinson disease (PD) results from the slow, progressive loss of dopaminergic neurons in the substantia nigra. Alterations in α-synuclein (aSyn), such as mutations or multiplications of the gene, are thought to trigger this degeneration. Here, we show that aSyn disrupts mitogen-activated protein kinase (MAPK)-controlled stress signaling in yeast and human cells, which results in inefficient cell protective responses and cell death. aSyn is a substrate of the yeast (and human) polo-like kinase Cdc5 (Plk2), and elevated levels of aSyn prevent Cdc5 from maintaining a normal level of GTP-bound Rho1, which is an essential GTPase that regulates stress signaling. The nine N-terminal amino acids of aSyn are essential for the interaction with polo-like kinases. The results support a unique mechanism of PD pathology.
Inhibitory cross-talk upon introduction of a new metabolic pathway into an existing metabolic network
Authors: Kim Juhan , Copley Shelley D.
Published: September 2012

Evolution or engineering of novel metabolic pathways can endow microbes with new abilities to degrade anthropogenic pollutants or synthesize valuable chemicals. Most studies of the evolution of new pathways have focused on the origins and quality of function of the enzymes involved. However, there is an additional layer of complexity that has received less attention. Introduction of a novel pathway into an existing metabolic network can result in inhibitory cross-talk due to adventitious interactions between metabolites and macromolecules that have not previously encountered one another. Here, we report a thorough examination of inhibitory cross-talk between a novel metabolic pathway for synthesis of pyridoxal 5′-phosphate and the existing metabolic network of
Escherichia coli.
We demonstrate multiple problematic interactions, including (
i
) interference by metabolites in the novel pathway with metabolic processes in the existing network, (
ii
) interference by metabolites in the existing network with the function of the novel pathway, and (
iii
) diversion of metabolites from the novel pathway by promiscuous activities of enzymes in the existing metabolic network. Identification of the mechanisms of inhibitory cross-talk can reveal the types of adaptations that must occur to enhance the performance of a novel metabolic pathway as well as the fitness of the microbial host. These findings have important implications for evolutionary studies of the emergence of novel pathways in nature as well as genetic engineering of microbes for “green” manufacturing processes.
Science faculty’s subtle gender biases favor male students
Authors: Moss-Racusin Corinne A. , Dovidio John F. , Brescoll Victoria L. , Graham Mark J. , Handelsman Jo
Published: September 2012

Despite efforts to recruit and retain more women, a stark gender disparity persists within academic science. Abundant research has demonstrated gender bias in many demographic groups, but has yet to experimentally investigate whether science faculty exhibit a bias against female students that could contribute to the gender disparity in academic science. In a randomized double-blind study (n= 127), science faculty from research-intensive universities rated the application materials of a student—who was randomly assigned either a male or female name—for a laboratory manager position. Faculty participants rated the male applicant as significantly more competent and hireable than the (identical) female applicant. These participants also selected a higher starting salary and offered more career mentoring to the male applicant. The gender of the faculty participants did not affect responses, such that female and male faculty were equally likely to exhibit bias against the female student. Mediation analyses indicated that the female student was less likely to be hired because she was viewed as less competent. We also assessed faculty participants’ preexisting subtle bias against women using a standard instrument and found that preexisting subtle bias against women played a moderating role, such that subtle bias against women was associated with less support for the female student, but was unrelated to reactions to the male student. These results suggest that interventions addressing faculty gender bias might advance the goal of increasing the participation of women in science.
Global forecasts of urban expansion to 2030 and direct impacts on biodiversity and carbon pools
Authors: Seto Karen C. , Güneralp Burak , Hutyra Lucy R.
Published: September 2012

Urban land-cover change threatens biodiversity and affects ecosystem productivity through loss of habitat, biomass, and carbon storage. However, despite projections that world urban populations will increase to nearly 5 billion by 2030, little is known about future locations, magnitudes, and rates of urban expansion. Here we develop spatially explicit probabilistic forecasts of global urban land-cover change and explore the direct impacts on biodiversity hotspots and tropical carbon biomass. If current trends in population density continue and all areas with high probabilities of urban expansion undergo change, then by 2030, urban land cover will increase by 1.2 million km
2
, nearly tripling the global urban land area circa 2000. This increase would result in considerable loss of habitats in key biodiversity hotspots, with the highest rates of forecasted urban growth to take place in regions that were relatively undisturbed by urban development in 2000: the Eastern Afromontane, the Guinean Forests of West Africa, and the Western Ghats and Sri Lanka hotspots. Within the pan-tropics, loss in vegetation biomass from areas with high probability of urban expansion is estimated to be 1.38 PgC (0.05 PgC yr
−1
), equal to ∼5% of emissions from tropical deforestation and land-use change. Although urbanization is often considered a local issue, the aggregate global impacts of projected urban expansion will require significant policy changes to affect future growth trajectories to minimize global biodiversity and vegetation carbon losses.
Detection of a rare BCR–ABL tyrosine kinase fusion protein in H929 multiple myeloma cells using immunoprecipitation (IP)-tandem mass spectrometry (MS/MS)
Authors: Breitkopf Susanne B. , Yuan Min , Pihan German A. , Asara John M.
Published: September 2012

Hypothesis directed proteomics offers higher throughput over global analyses. We show that immunoprecipitation (IP)–tandem mass spectrometry (LC-MS/MS) in H929 multiple myeloma (MM) cancer cells led to the discovery of a rare and unexpected BCR–ABL fusion, informing a therapeutic intervention using imatinib (Gleevec). BCR–ABL is the driving mutation in chronic myeloid leukemia (CML) and is uncommon to other cancers. Three different IP–MS experiments central to cell signaling pathways were sufficient to discover a BCR–ABL fusion in H929 cells: phosphotyrosine (pY) peptide IP, p85 regulatory subunit of phosphoinositide-3-kinase (PI3K) IP, and the GRB2 adaptor IP. The pY peptides inform tyrosine kinase activity, p85 IP informs the activating adaptors and receptor tyrosine kinases (RTKs) involved in AKT activation and GRB2 IP identifies RTKs and adaptors leading to ERK activation. Integration of the bait–prey data from the three separate experiments identified the BCR–ABL protein complex, which was confirmed by biochemistry, cytogenetic methods, and DNA sequencing revealed the e14a2 fusion transcript. The tyrosine phosphatase SHP2 and the GAB2 adaptor protein, important for MAPK signaling, were common to all three IP–MS experiments. The comparative treatment of tyrosine kinase inhibitor (TKI) drugs revealed only imatinib, the standard of care in CML, was inhibitory to BCR–ABL leading to down-regulation of pERK and pS6K and inhibiting cell proliferation. These data suggest a model for directed proteomics from patient tumor samples for selecting the appropriate TKI drug(s) based on IP and LC-MS/MS. The data also suggest that MM patients, in addition to CML patients, may benefit from BCR–ABL diagnostic screening.
siRNA silencing of estrogen receptor-α expression specifically in medial preoptic area neurons abolishes maternal care in female mice
Authors: Ribeiro Ana C. , Musatov Sergei , Shteyler Anna , Simanduyev Serge , Arrieta-Cruz Isabel , Ogawa Sonoko , Pfaff Donald W.
Published: September 2012

The medial preoptic area has been shown to be intricately involved in many behaviors, including locomotion, sexual behavior, maternal care, and aggression. The gene encoding estrogen receptor-α (ERα) protein is expressed in preoptic area neurons, and a very dense immunoreactive field of ERα is found in the preoptic region. ERα knockout animals show deficits in maternal care and sexual behavior and fail to exhibit increases in these behaviors in response to systemic estradiol treatment. In the present study, we used viral-vector mediated RNA interference to silence ERα expression specifically in the preoptic area of female mice and measured a variety of behaviors, including social and sexual aggression, maternal care, and arousal activity. Suppression of ERα in the preoptic area almost completely abolished maternal care, significantly increasing the latency to pup retrieval and significantly reducing the time the moms spent nursing and licking the pups. Strikingly, maternal aggression toward a male intruder was not different between control and preoptic ERα-silenced mice, demonstrating the remarkably specific role of ERα in these neurons. Reduction of ERα expression in preoptic neurons significantly decreased sexual behavior in female mice and increased aggression toward both sexual partners and male intruders in a seminatural environment. Estrogen-dependent increases in arousal, measured by home cage activity, were not mediated by ERα expression in the preoptic neurons we targeted, as ERα-suppressed mice had increases similar to control mice. Thus, we have established that a specific gene in a specific group of neurons is required for a crucially important natural behavior.
The impact of directionality on Chinese/English simultaneous interpreting
Authors: Chang Chia-chien , Schallert Diane L.
Published: September 2012

This paper addresses the issue of directionality in simultaneous interpreting by exploring professional Chinese/English interpreters’ experience of simultaneous interpreting, focusing specifically on the impact of language direction on their choice of strategies. Ten professional interpreters interpreted two speeches from English into Mandarin Chinese, and two speeches from Mandarin Chinese into English, each followed by a stimulated retrospective interview. The processes which seemed to be at work in their simultaneous interpreting were explored through a qualitative analysis of their retrospections, and a model was constructed on the role of professional practitioners’ use of strategies in each of the two directions. The results suggest that professional interpreters who must regularly work in both directions may develop strategic approaches to cope with the different demands of A-to-B and B-to-A interpreting. The differences seem to be a result not only of the asymmetry between their A- and B-language proficiency, but also of the strategies available to them, their metacognitive awareness of the limits of their language abilities, their audience’s expectations and other norms they believe apply to their performance, as well as the discourse structures of their working languages.
Are Yellowstone Lake Temperatures More Suitable to Nonnative Lake Trout than to Native Cutthroat Trout?
Authors: Kaeding Lynn R.
Published: September 2012

A recent study revealed limitations to the reproduction potential of Yellowstone cutthroat trout Oncorhynchus clarkii bouvieri (YCT) in Yellowstone Lake, Wyoming, resulting from suboptimal conditions for somatic growth. The present study evaluated the lake as suitable thermal habitat for YCT and lake trout Salvelinus namaycush, a highly piscivorous, nonnative species, a reproducing population of which was discovered there in 1994. Because the fundamental thermal niche of lake trout delimits a zone of the lake's annual temperature profile that surrounds the corresponding, separate zone for YCT, the annual growing season and volume of suitable Yellowstone Lake habitat will invariably be larger for lake trout than YCT across the range of cool-to-warm climate years. Ongoing management actions to control lake trout emphasize intensive gill netting, while temporal changes in lake trout catch rates and population structure provide metrics of program success. However, the limits to YCT reproduction potential attributed to the short growing season make the YCT population especially susceptible to lake trout predation, perhaps even from a measurably reduced predator population. Identification of such effects requires that dynamic, age-structured models of the YCT population that incorporate all important population drivers be formulated and used in data analyses and control program assessment.

Received February 5, 2012; accepted May 8, 2012
Estimating Escapement for a Low-Abundance Steelhead Population Using Dual-Frequency Identification Sonar (DIDSON)
Authors: Pipal Kerrie A. , Notch Jeremy J. , Hayes Sean A. , Adams Peter B.
Published: September 2012

Estimating the escapement of small populations of steelhead Oncorhynchus mykiss (ocean-migrating rainbow trout) is challenging and requires innovative methods. Difficulties arise from rare and episodic occurrence of individuals, high turbidity levels during migration, and the need to minimize jeopardy to the fish, which have led to a lack of population estimates, especially in California. Here we show that dual-frequency identification sonar (DIDSON) can be used to produce escapement estimates for a small steelhead population in Scott Creek, Santa Cruz County, California, with virtually no impact on the fish. The DIDSON uses sound to form near-video quality images and passively monitors fish without the need to handle them or constrict passage. We deployed a DIDSON and recorded steelhead passage over three spawning seasons (2008–2010). We used a decision support tool to analyze DIDSON images and compared the resulting estimates (153, 57, and 84) with raw weir counts (50, 23, and 40), mark–recapture estimates (293 ± 9, 126 ± 12, and 109 ± 34) generated over the entire migration period, and adjusted mark–recapture estimates (201, 74, and 85), which coincided with the period of DIDSON deployment. The DIDSON and weir estimates were restricted to a smaller sampling window due to the installation of downstream migrant traps causing increased incidences of milling fish that interfered with the DIDSON results late in the migration season. The DIDSON estimates were two to three times higher than weir estimates and 23% to 55% less than the full-season mark–recapture estimates. The adjusted mark–recapture estimates followed the same trends as the full-season mark–recapture estimates and were correlated with the DIDSON estimates. We conclude that DIDSON is an effective tool to generate steelhead escapement estimates, but it is important to collect data over the entire migration season and to consider fish behavior and potential species identification issues during analysis.

Received October 6, 2011; accepted May 21, 2012
Behavior, Knowledge, and Attitudes towards Khat among Yemeni Medical Students and Effects of a Seminar
Authors: Yi Paul H. , Kim John S. , Hussein Khalil I. , Saitz Richard
Published: September 2012

This study describes khat behavior, knowledge, and attitudes among Yemeni medical students (MS) and the effects of a seminar. The students completed a survey ( n = 62); a subgroup participated in a discussion-based seminar and follow-up survey ( n = 18). Although the students demonstrated knowledge about khat's health effects and considered it unacceptable for health professionals to chew khat, they disagreed that health professionals should advise patients to quit. Knowledge and attitudes improved post-seminar (not significant, except for a borderline significant increase in students correctly identifying khat as addictive; P = 0.063). Although effects were small, seminars may help health professionals address khat use in Yemen.
An Injectable, Slow-Release Implantation Method for Exposing Fish to Chemicals over a Period of Weeks
Authors: Zaroogian Gerald E , Gutjahr-Gobell Ruth E , Horowitz Doranne Borsay , Jayaraman Saro , Cantwell Mark , Chichester Clinton O , Mills Lesley J
Published: September 2012

A slow-release, injectable implant method was developed for administering test chemicals to cunners Tautogolabrus adspersus. The implant is composed of a matrix of a test chemical homogenized in a mixture of Ethocel (Dow Chemical) and coconut oil. The effectiveness of a subcutaneous implant of this matrix in vivo was determined by tracing plasma concentrations of three separate chemicals (estradiol, ethynylestradiol, and atrazine) over time in treated male cunners. Release from the implant was determined based on the percentage of the implanted concentration of test chemical (plus metabolites) that was detected in fish plasma over a 1–2-week period after implantation. Circulating estrogen concentrations measured in plasma from two different cunners that received the estradiol implant were almost identical, indicating that there is a reasonably even distribution of test chemical within the Ethocel–coconut oil preparation and that individual variability may be minimal for release of test chemical from the implant. Metabolites of estradiol and atrazine were a major portion of the circulating concentration of these chemicals. Estradiol and atrazine demonstrated metabolic and clearance profiles that were very different from those of the xenoestrogen ethynylestradiol. A follow-up in vitro study was conducted to further characterize the release of estradiol from the implant matrix. Results showed a rapid release of estradiol from the matrix bolus during the first 24 h, followed by a more gradual release over subsequent days. The in vitro tests indicated that measuring in vivo plasma concentrations may not accurately reflect the release rate of a chemical from the implant matrix, in part because metabolism and clearance affect the circulating concentrations in vivo.