bluuebunny/crossref_metadata_2025 huggingface dataset:
Transport properties of room-temperature ionic liquids from classical molecular dynamics
Authors: Andreussi Oliviero , Marzari Nicola
Published: July 2012

Room-temperature ionic liquids (RTILs) have attracted much attention in the scientific community in the past decade due their novel and highly customizable properties. Nonetheless, their high viscosities pose serious limitations to the use of RTILs in practical applications. To elucidate some of the physical aspects behind transport properties of RTILs, extensive classical molecular dynamics calculations are reported. Here, in particular, bulk viscosities and ionic conductivities of butyl-methyl-imidazole based RTILs are presented over a wide range of temperatures. The dependence of the properties of the liquids on simulation parameters, e.g., system-size effects or the choice of the interaction potential, is analyzed in detail.
Translational invariance, the Post constraint and uniqueness in macroscopic electrodynamics
Authors: de Lange O. L. , Raab R. E. , Welter A.
Published: July 2012

We consider semi-classical multipole theory for non-magnetic molecules interacting with harmonic plane electromagnetic waves, to electric octopole–magnetic quadrupole order and relative to an arbitrary set of molecular coordinate origins {On}. Spatial averaging of expectation values of induced molecular multipole moments produces a macroscopic theory for linear, homogeneous, anisotropic media that has three shortcomings: it is only partially invariant with respect to {On}, it is ambivalent on the Post constraint (equality of the traces of the magnetoelectric tensors), and it yields non-unique dynamic response fields D and H. To remedy these, we present a fully invariant theory that is consistent (affirmative) on the Post constraint, and is based on five time-even, invariant molecular polarizability tensors (one each of electric dipole and electric quadrupole–magnetic dipole order, and three of electric octopole–magnetic quadrupole order). As in previous work on linear phenomena, translational invariance is achieved through the Van Vleck–Buckingham condition. Uniqueness of the invariant response fields is demonstrated, based on linear independence of molecular polarizability tensors at each multipole order above electric dipole. Our results are compared with previously published expressions for two invariant polarizabilities.
Nonlocal, kinetic stimulated Raman scattering in nonuniform plasmas: Averaged variational approach
Authors: Khain P. , Friedland L. , Shagalov A. G. , Wurtele J. S.
Published: July 2012

Excitation of continuously phase-locked (autoresonant) plasma waves in a nonuniform plasma via stimulated Raman backscattering is analyzed with a focus on the kinetic regime (kλD∼1). The dominant nonlinear effect in this regime is that of resonant particles, and the plasma wave excitation is a nonlocal process involving formation and transport of the electron phase space holes. Whitham’s averaged variational principle is applied in studying the coupled plasma, laser pump, and seed waves dynamics. A flat-top electron velocity distribution is used as the simplest model allowing a variational formulation within the water bag theory. The corresponding Lagrangian, averaged over the fast phase variable, yields evolution equations for the slow field variables. The adiabatic multiple water bag extension of the theory for application to autoresonant plasma waves in nonuniform plasmas with more realistic initial distributions is also discussed. Numerical solutions of the system of slow variational equations are compared with Vlasov-Ampere simulations.
Effects of scattering on two-dimensional electron gases in InGaAs/InAlAs quantum wells
Authors: Zhou W. Z. , Wang W. , Chang Z. G. , Wang Y. Z. , Lan Z. Q. , Shang L. Y. , Lin T. , Cui L. J. , Zeng Y. P. , Li G. X. , Yu C. H. , Guo J. , Chu J. H.
Published: July 2012

The effects of different scattering on two-dimensional electron gases (2DEGs) in lattice matched In0.53Ga0.47As/In0.52Al0.48As quantum wells with silicon δ-doped in one barrier layer have been investigated by means of magneto-transport measurements. For the studied samples, the 2DEGs have occupied two subbands. It is found that the dominant scattering mechanism is ionized impurities scattering for the two subbands’ electrons. Besides the dominant scattering mechanism of ionized impurities scattering, Coulomb scattering also plays a role in scattering mechanism for both subbands. Both the transport scattering time and the quantum scattering time of the second subband are larger than those of the first subband. It is because that the electrons of the first subband are, on average, closer to the ionized impurities in the doped layer, they will be scattered more strongly than those in the second subband. Due to the electron wave functions for the second subband spread more widely in the quantum wells, the alloy disorder scattering is more important for the carriers in the second subband than that in the first subband.
On the zero-field orbital magnetic susceptibility of Bloch electrons in graphene-like solids: Some rigorous results
Authors: Savoie Baptiste
Published: July 2012

Starting with a nearest-neighbors tight-binding model, we rigorously investigate the bulk zero-field orbital susceptibility of a non-interacting Bloch electrons gas in graphene-like solids at fixed temperature and density of particles. In the zero-temperature limit and in the semiconducting situation, we derive a complete expression which holds for an arbitrary number of bands with possible degeneracies. In the particular case of a two-bands gapped model, all involved quantities are explicitly written down. Besides the formula that we obtain have the special feature to be suitable for numerical computations since it only involves the eigenvalues and associated eigenfunctions of the Bloch Hamiltonian, together with the derivatives (up to the second order) w.r.t. the quasi-momentum of the matrix-elements of the Bloch Hamiltonian. Finally we give a simple application for the two-bands gapped model by considering the case of a dispersion law which is linear w.r.t. the quasi-momentum in the gapless limit. Through this instance, the origin of the singularity, which expresses as a Dirac delta function of the Fermi energy, implied by the McClure's formula in monolayer graphene is discussed.
Quantitative investigations of aggregate systems
Authors: Rai D. K. , Beaucage G. , Jonah E. O. , Britton D. T. , Sukumaran S. , Chopra S. , Gonfa G. Goro , Härting M.
Published: July 2012

Nanomaterials with disordered, ramified structure are increasingly being used for applications where low cost and enhanced performance are desired. A particular example is the use in printed electronics of inorganic conducting and semiconducting nanoparticles. The electrical, as well as other physical properties depend on the arrangement and connectivity of the particles in such aggregate systems. Quantification of aggregate structure and development of structure/property relationships is difficult and progress in the application of these materials in electronics has mainly been empirical. In this paper, a scaling model is used to parameterize the structure of printed electronic layers. This model has chiefly been applied to polymers but surprisingly it shows applicability to these nanolayers. Disordered structures of silicon nanoparticles forming aggregates are investigated using small angle x-ray scattering coupled with the scaling model. It is expected that predictions using these structural parameters can be made for electrical properties. The approach may have wide use in understanding and designing nano-aggregates for electronic devices.
Wall-liquid and wall-crystal interfacial free energies via thermodynamic integration: A molecular dynamics simulation study
Authors: Benjamin Ronald , Horbach Jürgen
Published: July 2012

A method is proposed to compute the interfacial free energy of a Lennard-Jones system in contact with a structured wall by molecular dynamics simulation. Both the bulk liquid and bulk face-centered-cubic crystal phase along the (111) orientation are considered. Our approach is based on a thermodynamic integration scheme where first the bulk Lennard-Jones system is reversibly transformed to a state where it interacts with a structureless flat wall. In a second step, the flat structureless wall is reversibly transformed into an atomistic wall with crystalline structure. The dependence of the interfacial free energy on various parameters such as the wall potential, the density and orientation of the wall is investigated. The conditions are indicated under which a Lennard-Jones crystal partially wets a flat wall.
Improved analysis techniques for cylindrical and spherical double probes
Authors: Beal Brian , Johnson Lee , Brown Daniel , Blakely Joseph , Bromaghim Daron
Published: July 2012

A versatile double Langmuir probe technique has been developed by incorporating analytical fits to Laframboise's numerical results for ion current collection by biased electrodes of various sizes relative to the local electron Debye length. Application of these fits to the double probe circuit has produced a set of coupled equations that express the potential of each electrode relative to the plasma potential as well as the resulting probe current as a function of applied probe voltage. These equations can be readily solved via standard numerical techniques in order to determine electron temperature and plasma density from probe current and voltage measurements. Because this method self-consistently accounts for the effects of sheath expansion, it can be readily applied to plasmas with a wide range of densities and low ion temperature (Ti/Te ≪ 1) without requiring probe dimensions to be asymptotically large or small with respect to the electron Debye length. The presented approach has been successfully applied to experimental measurements obtained in the plume of a low-power Hall thruster, which produced a quasineutral, flowing xenon plasma during operation at 200 W on xenon. The measured plasma densities and electron temperatures were in the range of 1 × 1012–1 × 1017 m−3 and 0.5–5.0 eV, respectively. The estimated measurement uncertainty is +6%/−34% in density and +/−30% in electron temperature.
Non-parabolic intergranular barriers in tin oxide and gas sensing
Authors: Aldao C. M. , Malagù C.
Published: July 2012

Chemoresistive properties of crystalline solids strongly depend on the concentration of stoichiometric defects. In the case of tin oxide, oxygen vacancies are a case in point of such kind of defects. We address the problem of band bending and Schottky barrier formation in tin oxide. We approached the problem of charged native defects, oxygen vacancies, in a metal oxide in equilibrium with an oxygen containing ambient under three equivalent points of view. We focused on the non-parabolic barriers character that forms at intergrains. Implications in electrical responses to oxygen concentration variations will be discussed.
Influence of the dye impregnation time on the electrical impedance of a solar cell
Authors: Alexe-Ionescu A. L. , Barbero G. , Pirri C. F. , Tresso E.
Published: July 2012

The effect of the dye-impregnation time on the electrical impedance of a dye-sensitized solar cell is theoretically investigated. The proposed model is based on the assumption that during the impregnation processes the covering of the titania electrodes, initially incomplete, arrives to saturation and the adsorption coverage can be described by a diffusive process, depending on the square root of the impregnation time. An equivalent circuit, formed by an electrical impedance related to the bulk contribution due to the electrolyte, and by a contribution due to the presence of the porous electrode partially covered by the dye is derived. The equivalent circuit is able to justify the experimental data recently reported on the influence of the dye-impregnation time on the electrical response of a solar cell. We show that a more complete analysis of the response of the solar cell to an external excitation, performed using the equations of continuity of the ions present in the electrolyte, and the equation of Poisson for the actual electric potential across the cell, allows to justify the proposed equivalent electric circuit.
Spin Hall effect in a kagome lattice driven by Rashba spin-orbit interaction
Authors: Dey Moumita , Maiti Santanu K. , Karmakar S. N.
Published: July 2012

Using four-terminal Landauer-Büttiker formalism and Green’s function technique, in this present paper, we calculate numerically spin Hall conductance (SHC) and longitudinal conductance of a finite size kagome lattice with Rashba spin-orbit (SO) interaction both in the presence and absence of external magnetic flux in clean limit. In the absence of magnetic flux, we observe that depending on the Fermi surface topology of the system SHC changes its sign at certain values of Fermi energy. Unlike the infinite system (where SHC is a universal constant ±e8π), here SHC depends on the external parameters like SO coupling strength, Fermi energy, etc. We show that in the presence of any arbitrary magnetic flux, periodicity of the system is lost and the features of SHC tend to get reduced because of elastic scattering. But again at some typical values of flux (ϕ=12, 14, 34…, etc.) the system retains its periodicity depending on its size and the features of spin Hall effect (SHE) reappears. Our predicted results may be useful in providing a deeper insight into the experimental realization of SHE in such geometries.
Measuring acoustic nonlinearity parameter using collinear wave mixing
Authors: Liu Minghe , Tang Guangxin , Jacobs Laurence J. , Qu Jianmin
Published: July 2012

This study introduces a new acoustic nonlinearity parameter βT. It is shown that βT is associated with the interaction between a longitudinal wave and a shear wave in isotropic elastic solids with quadratic nonlinearity. Experimental measurements are conducted to demonstrate that the collinear wave mixing technique is capable of measuring βT nondestructively. Further, it is shown that βT is well-correlated with the plastic deformation in Al-6061 alloys. These results indicate that collinear wave mixing is a promising method for nondestructive assessment of plastic deformation, and possibly, fatigue damage in metallic materials.
Polymeric nanofibrous composite membranes for energy efficient ethanol dehydration
Authors: Yeh Tsung-Ming , Yang Liu , Wang Xiao , Mahajan Devinder , Hsiao Benjamin S. , Chu Benjamin
Published: July 2012

Ethanol derived from the fermentation process (e.g., from corn) is widely used as a blend to improve the air quality and to decrease the demand for gasoline. During the production process, ethanol dehydration is usually carried out by azeotropic distillation, which consumes about twice amount of energy than the “pervaporation” method. The purpose of this study is to demonstrate an energy-efficient nanofibrous composite pervaporation membrane system for production of dehydrated ethanol. The nanofibrous membrane system consists of a cross-linked polyvinyl alcohol hydrophilic barrier layer, an buffer layer based on ultra-fine cellulose nanofibers (diameter about 5 nm), and an electrospun nanofibrous scaffold layer with high porosity (e.g., 80%) and fully interconnected pore structures. The performance between the conventional pervaporation membranes and nanofibrous composite membranes was compared under the same pervaporation conditions.
Supersonic regime of the Hall-magnetohydrodynamics resistive tearing instability
Authors: Ahedo Eduardo , Ramos Jesús J.
Published: July 2012

An earlier analysis of the Hall-magnetohydrodynamics (MHD) tearing instability [E. Ahedo and J. J. Ramos, Plasma Phys. Controlled Fusion 51, 055018 (2009)] is extended to cover the regime where the growth rate becomes comparable or exceeds the sound frequency. Like in the previous subsonic work, a resistive, two-fluid Hall-MHD model with massless electrons and zero-Larmor-radius ions is adopted and a linear stability analysis about a force-free equilibrium in slab geometry is carried out. A salient feature of this supersonic regime is that the mode eigenfunctions become intrinsically complex, but the growth rate remains purely real. Even more interestingly, the dispersion relation remains of the same form as in the subsonic regime for any value of the instability Mach number, provided only that the ion skin depth is sufficiently small for the mode ion inertial layer width to be smaller than the macroscopic lengths, a generous bound that scales like a positive power of the Lundquist number.
Three-dimensional numerical investigation of electron transport with rotating spoke in a cylindrical anode layer Hall plasma accelerator
Authors: Tang D. L. , Geng S. F. , Qiu X. M. , Chu Paul K.
Published: July 2012

The effects of increased magnetic field and pressure on electron transport with a rotating spoke in a cylindrical anode layer Hall plasma accelerator are investigated by three-dimensional particle-in-cell numerical simulation. The azimuthal rotation of electron transport with the spoke has a frequency of 12.5 MHz. It propagates in the direction of the E × B drift at a speed of ∼1.0 × 106 m/s (about 37% of the E × B drift speed). Local charge separation occurs because the azimuthal local electron density concentration is accompanied by an almost uniform azimuthal ion distribution. The non-axisymmetrical electron density concentration and axisymmetrical ion distribution introduce two azimuthal electric fields with opposite directions in the plasma discharge region. The axial electron shear flow is excited under the additional Eθ × B field. The anomalous electron transport with the rotating spoke may be attributed to the axial electron shear flow induced by the two azimuthal electric fields with opposite directions as a result of the azimuthal local electron density concentration.
Peptide-Based Star Polymers: The Rising Star in Functional Polymers
Authors: Sulistio Adrian , Gurr Paul A. , Blencowe Anton , Qiao Greg G.
Published: July 2012

Peptide-based star polymers show great potential as the next-generation of functional polymers due to their structure-related properties. The peptide component augments the polymer’s properties by introducing biocompatible and biodegradable segments, and enhancing their functionalities and structural ordering, which make peptide-based star polymers an attractive candidate in the field of nanomedicine. This article provides a brief summary of the recent developments of peptide-based star polymers synthesised from 2009 onwards. It is evident that the studies conducted so far have only started to uncover the true potential of what these polymers can achieve, and with continued research it is anticipated that peptide-based star polymers will be realised as versatile platforms applicable to broader fields of study, including drug delivery, tissue engineering, biocoatings, bioimaging, and self-directing templating agents.
Application of field portable X-ray fluorescence to the analysis of desert varnish samples in areas affected by coal-fired power plants
Authors: Nowinski Piotr , Hodge Vernon F. , Gerstenberger Shawn
Published: July 2012

Environmental context Rock surfaces are often covered with a dark coating called desert varnish that can capture and retain air pollutants. A field portable X-ray fluorescence spectrometer was used for direct non-destructive analysis of varnished rocks in the fallout zones of two coal-fired power plants. At one power plant where tracer studies had been carried out, the highest concentration of elements including Cr, As, Pb and Zn in the rock varnish samples, coincides with the peak tracer concentration locations. AbstractDesert varnish samples were collected near two coal-fired power plants to determine if the varnish contained a record of recent air pollution. Samples were collected: (1) in the fallout patterns of the shuttered Mohave Power Plant (MPP), located in Laughlin, NV; and (2) near the operating Reid-Gardner Power Plant (RGPP), just east of Las Vegas, NV. Small pieces of varnished rocks were analysed by field portable X-ray fluorescence spectroscopy (FPXRF). Results were obtained for 15 elements: Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Zr, Mo, Hg and Pb. The FPXRF data indicate that the elements commonly found in fly ash from coal-fired power plants (e.g. Cr, Zn, As and Pb) had significantly higher concentrations in the rock coatings in relation to the unvarnished substrate rock. For one of the power plants, where tracer plume studies had been carried out, the highest concentrations in the desert varnish coincided with the peak tracer concentration locations. Thus, these elements in desert varnish hold promise for identifying those geographical regions affected by nearby power plants. However, additional samples are required to demonstrate unequivocally that the power plants are indeed the sources of these elements. Overall, it is apparent that desert varnish can be utilised as a passive environmental monitor to investigate recent air pollution (past 20–30 years) and that FPXRF can be used as a surveying tool to obtain multi-element data from a large number of samples.
Application of artificial neural networks and logistic regression to the prediction of forest fire danger in Galicia using MODIS data
Authors: Bisquert Mar , Caselles Eduardo , Sánchez Juan Manuel , Caselles Vicente
Published: July 2012

Fire danger models are a very useful tool for the prevention and extinction of forest fires. Some inputs of these models, such as vegetation status and temperature, can be obtained from remote sensing images, which offer higher spatial and temporal resolution than direct ground measures. In this paper, we focus on the Galicia region (north-west of Spain), and MODIS (Moderate Resolution Imaging Spectroradiometer) images are used to monitor vegetation status and to obtain land surface temperature as essential inputs in forest fire danger models. In this work, we tested the potential of artificial neural networks and logistic regression to estimate forest fire danger from remote sensing and fire history data. Remote sensing inputs used were the land surface temperature and the Enhanced Vegetation Index. A classification into three levels of fire danger was established. Fire danger maps based on this classification will facilitate fire prevention and extinction tasks.
Predictive modelling of burn probability and burn severity in a desert spring ecosystem
Authors: Sunderman Stephanie O. , Weisberg Peter J.
Published: July 2012

Little is known about the fire ecology of desert springs, despite their importance for biodiversity and for provision of ecosystem services. Desert spring ecosystems are characterised by high and continuous fuel loads compared with surrounding uplands, suggesting that fire may play a significant ecological role. For the Ash Meadows spring complex in the south-western USA, we used ecological-niche factor analysis and a Bayesian model averaging regression technique to characterise the environmental conditions associated with spatially explicit burn probability and burn severity over a 24-year period. Burn probability and burn severity were both more strongly associated with fuel availability than with proximity to anthropogenic ignition sources; however, areas with more homogeneous vegetation cover were positively associated with high-severity burns but were negatively associated with burn probability. Burn probability was greater near areas of high anthropogenic influence, whereas areas further from anthropogenic alteration were more likely to experience high-severity fire. Riparian forest and emergent wetland vegetation were most likely to burn although they were among the rarest vegetation types. Human activities may strongly influence fire regimes in desert spring wetlands through groundwater pumping and introductions of exotic plants that alter fuelbed heterogeneity and shift the balance among woody and herbaceous vegetation.
Mediation of estrogen mitogenic effect in human breast cancer MCF-7 cells by PC-cell-derived growth factor (PCDGF/granulin precursor)
Authors: Lu Runqing , Serrero Ginette
Published: July 2012

PC-cell-derived growth factor (PCDGF) is an 88-kDa glycoprotein
corresponding to the granulin precursor. We have reported that PCDGF
was expressed in human breast cancer cells. In estrogen-receptor
positive cells, 17-β-estradiol (E
2
) transcriptionally
stimulated PCDGF expression in a dose- and time-dependent fashion. We
demonstrate here that PCDGF mediates the mitogenic effect of
E
2
in MCF-7 cells. PCDGF substituted for E
2
to
stimulate DNA synthesis. The E
2
mitogenic effect was
inhibited in a dose-dependent fashion by anti-PCDGF neutralizing
antibody. Inhibition of PCDGF expression by antisense transfection also
inhibited the E
2
mitogenic effect. In contrast,
overexpression of PCDGF in MCF-7 cells resulted in cells that were able
to proliferate in the absence of estrogen and were tamoxifen resistant.
The PCDGF signaling pathway was examined. Like E
2
, PCDGF
stimulated mitogen-activated protein kinase activity. PCDGF could
substitute for E
2
in stimulating cyclin D1 expression. The
cyclin D1 stimulation by E
2
was 50% inhibited by
anti-PCDGF antibody. In contrast, PCDGF did not stimulate
c-
myc
expression, another molecular target of
E
2
. We conclude that autocrine PCDGF mediates the
E
2
mitogenic effect via stimulation of cyclin D1. These
studies provide information on estrogen action and identify an
autocrine molecular target in human breast cancer cells.
The chondrogenic transcription factor Sox9 is a target of signaling by the parathyroid hormone-related peptide in the growth plate of endochondral bones
Authors: Huang Wendong , Chung Ung-il , Kronenberg Henry M. , de Crombrugghe Benoit
Published: July 2012

In the growth plate of endochondral bones, parathyroid hormone
(PTH)-related peptide (PTHrP) regulates the rate of chondrocyte
maturation from prehypertrophic chondrocytes to hypertrophic
chondrocytes. Using an antibody specific for Sox9 phosphorylated at
serine 181 (S
181
), one of the two consensus protein kinase
A phosphorylation sites of Sox9, we showed that the addition of PTHrP
strongly increased the phosphorylation of SOX9 in COS7 cells
transfected with both SOX9- and PTH/PTHrP receptor-expressing
vectors. PTHrP also increased the SOX9-dependent activity of
chondrocyte-specific enhancers in the gene for type II collagen
(
Col2a1
) in transient transfection experiments. This
increased enhancer activity did not occur with a Sox9 mutant harboring
serine-to-alanine substitutions in its two consensus protein kinase A
phosphorylation sites. Consistent with these results, PTHrP also
increased
Col2a1
mRNA levels in rat chondrosarcoma cells
as well as 10T1/2 mesenchymal cells transfected with a PTH/PTHrP
receptor expressing plasmid. No phosphorylation of Sox9 at
S
181
was detected in prehypertrophic chondrocytes of the
growth plate or any chondrocytes of PTH/PTHrP receptor null mutants.
In contrast in wild-type mouse embryos, previous immunohistochemistry
experiments indicated that Sox9 phosphorylated at S
181
was
detected almost exclusively in chondrocytes of the prehypertrophic
zone. Sox9, regardless of the phosphorylation state, was present in all
chondrocytes of both genotypes except hypertrophic chondrocytes. Our
results indicated that Sox9 is a target of PTHrP signaling in
prehypertrophic chondrocytes in the growth plate. We hypothesize that
Sox9 mediates at least some effects of PTHrP in the growth plate and
that the PTHrP-dependent increased transcriptional activity of Sox9
helps maintain the chondrocyte phenotype of cells in the
prehypertrophic zone and inhibits their maturation to hypertrophic
chondrocytes.
Blocking histone deacetylation in
Arabidopsis
induces pleiotropic effects on plant gene regulation and development
Authors: Tian Lu , Chen Z. Jeffrey
Published: July 2012

Histone acetylation and deacetylation play essential roles in
eukaryotic gene regulation. Reversible modifications of core histones
are catalyzed by two intrinsic enzymes, histone acetyltransferase and
histone deacetylase (HD). In general, histone deacetylation is related
to transcriptional gene silencing, whereas acetylation correlates with
gene activation. We produced transgenic plants expressing the antisense
Arabidopsis
HD (AtHD1) gene. AtHD1 is a homolog of human
HD1 and RPD3 global transcriptional regulator in yeast. Expression of
the antisense
AtHD1
caused dramatic reduction in
endogenous
AtHD1
transcription, resulting in
accumulation of acetylated histones, notably tetraacetylated H4.
Reduction in
AtHD1
expression and AtHD1 production and
changes in acetylation profiles were associated with various
developmental abnormalities, including early senescence, ectopic
expression of silenced genes, suppression of apical dominance, homeotic
changes, heterochronic shift toward juvenility, flower defects, and
male and female sterility. Some of the phenotypes could be attributed
to ectopic expression of tissue-specific genes (e.g.,
SUPERMAN
) in vegetative tissues. No changes in genomic
DNA methylation were detected in the transgenic plants. These results
suggest that AtHD1 is a global regulator, which controls gene
expression during development through DNA-sequence independent or
epigenetic mechanisms in plants. In addition to DNA methylation,
histone modifications may be involved in a general regulatory mechanism
responsible for plant plasticity and variation in nature.
Impaired adipogenesis and lipolysis in the mouse upon selective ablation of the retinoid X receptor α mediated by a tamoxifen-inducible chimeric Cre recombinase (Cre-ER
T2
) in adipocytes
Authors: Imai Takeshi , Jiang Ming , Chambon Pierre , Metzger Daniel
Published: July 2012

Retinoid X receptor α (RXRα) is involved in multiple signaling
pathways, as a heterodimeric partner of several nuclear receptors. To
investigate its function in energy homeostasis, we have selectively
ablated the RXRα gene in adipocytes of 4-week-old transgenic mice by
using the tamoxifen-inducible Cre-ER
T2
recombination
system. Mice lacking RXRα in adipocytes were resistant to dietary and
chemically induced obesity and impaired in fasting-induced lipolysis.
Our results also indicate that RXRα is involved in adipocyte
differentiation. Thus, our data demonstrate the feasibility of
adipocyte-selective temporally controlled gene engineering and reveal a
central role of RXRα in adipogenesis, probably as a
heterodimeric partner for peroxisome proliferator-activated
receptor γ.
Presenilin-mediated transmembrane cleavage is required for Notch signal transduction in
Drosophila
Authors: Struhl Gary , Greenwald Iva
Published: July 2012

The cleavage model for signal transduction by receptors of the
LIN-12/Notch family posits that ligand binding leads to cleavage
within the transmembrane domain, so that the intracellular domain is
released to translocate to the nucleus and activate target gene
expression. The familial Alzheimer's disease-associated protein
Presenilin is required for LIN-12/Notch signaling, and several lines
of evidence suggest that Presenilin mediates the transmembrane cleavage
event that releases the LIN-12/Notch intracellular domain. However,
doubt was cast on this possibility by a report that Presenilin is not
required for the transducing activity of N
ECN
, a
constitutively active transmembrane form of Notch, in
Drosophila
. Here, we have reassessed this finding and
show instead that Presenilin is required for activity of
N
ECN
for all cell fate decisions examined. Our results
indicate that transmembrane cleavage and signal transduction are
strictly correlated, supporting the cleavage model for signal
transduction by LIN-12/Notch and a role for Presenilin in mediating
the ligand-induced transmembrane cleavage.
Anti-apoptotic signaling by hepatocyte growth factor/Met via the phosphatidylinositol 3-kinase/Akt and mitogen-activated protein kinase pathways
Authors: Xiao Guang-Hui , Jeffers Michael , Bellacosa Alfonso , Mitsuuchi Yasuhiro , Vande Woude George F. , Testa Joseph R.
Published: July 2012

Hepatocyte growth factor (HGF) is a ligand of the receptor tyrosine
kinase encoded by the c-
Met
protooncogene.
HGF/Met signaling has multifunctional effects on various cell
types. We sought to determine the role of HGF/Met in
apoptosis and identify signal transducers involved in this
process. In experiments with human SK-LMS-1 leiomyosarcoma cells, we
show that the Akt kinase is activated by HGF in a time- and
dose-dependent manner by phosphatidylinositol 3-kinase (PI3-kinase).
Akt is also activated by active tumorigenic forms of Met, i.e.,
ligand-independent Tpr-Met, a truncated and constitutively dimerized
form of Met, and a mutationally activated version of Met corresponding
to that found in human hereditary papillary renal carcinoma. In NIH 3T3
cells transfected with wild-type Met, HGF inhibits apoptosis
induced by serum starvation and UV irradiation. HGF-induced survival
correlates with Akt activity and is inhibited by the specific
PI3-kinase inhibitor LY294002, indicating that HGF inhibits cell death
through the PI3-kinase/Akt signal transduction pathway.
Furthermore, transiently transfected Tpr-Met activates Akt (both Akt1
and Akt2) and protects cells from apoptosis. Mitogen-activated
protein kinase (MAPK) also is activated by HGF and rescues cells from
apoptosis, although the cytoprotective effect is less marked
than for PI3-kinase/Akt. Blocking MAPK with the specific MAPK
kinase inhibitor PD098059 impairs the ability of HGF to promote cell
survival. Similar results were obtained with NIH 3T3 cells expressing
the fusion protein Trk-Met and stimulated with nerve growth factor, the
Trk ligand. These results demonstrate that HGF/Met is capable of
protecting cells from apoptosis by using both
PI3-kinase/Akt and, to a lesser extent, MAPK pathways.
Oscillator representations and systems of ordinary differential equations
Authors: Parmeggiani Alberto , Wakayama Masato
Published: July 2012

Using representation-theoretic methods, we determine the spectrum
of the 2 × 2 system

\documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\setlength{\oddsidemargin}{-69pt}
\begin{document}
\begin{equation*}\boldsymbol{{\mathit{Q}}}(\boldsymbol{{\mathit{x}}{\mathrm{,\hspace{.167em}}}{\mathit{D}}}_{\boldsymbol{{\mathit{x}}}})\boldsymbol{{\mathrm{\hspace{.167em}=\hspace{.167em}}}{\mathit{A}}} \left( \boldsymbol{{\mathrm{-}}}\frac{\boldsymbol{{\mathrm{{\partial}}}}^{\boldsymbol{{\mathrm{2}}}}_{\boldsymbol{{\mathit{x}}}}}{\boldsymbol{{\mathrm{2}}}}\boldsymbol{{\mathrm{\hspace{.167em}+\hspace{.167em}}}}\frac{\boldsymbol{{\mathit{x}}}^{\boldsymbol{{\mathrm{2}}}}}{\boldsymbol{{\mathrm{2}}}} \right) \boldsymbol{{\mathrm{\hspace{.167em}+\hspace{.167em}}}{\mathit{B}}} \left( \boldsymbol{{\mathit{x}}{\mathrm{{\partial}}}}_{\boldsymbol{{\mathit{x}}}}\boldsymbol{{\mathrm{\hspace{.167em}+\hspace{.167em}}}}\frac{\boldsymbol{{\mathrm{1}}}}{\boldsymbol{{\mathrm{2}}}} \right) \boldsymbol{{\mathrm{,\hspace{.167em}}}{\mathit{x}}{\mathrm{\hspace{.167em}{\in}\hspace{.167em}{\mathbb{R}},}}}\end{equation*}\end{document}

with
A
,
B
∈ Mat
2
(ℝ)
constant matrices such that
A
=

t

A
> 0 (or <0),
B
= −

t

B
≠ 0, and the Hermitian matrix
A
+
iB
positive (or negative) definite. We
also give results that generalize (in a possible direction) the main
construction.
Extended lung expression and increased tissue localization of viral IL-10 with adenoviral gene therapy
Authors: Minter Rebecca M. , Ferry Maria A. , Rectenwald John E. , Bahjat F. R. , Oberholzer Andreas , Oberholzer Caroline , La Face Drake , Tsai Van , Ahmed C. M. Iqbal , Hutchins Beth , Copeland Edward M. , Ginsberg Harold S. , Moldawer Lyle L.
Published: July 2012

IL-10 is a pleiotropic cytokine that acts as an important regulator of macrophage, T cell, and natural killer cell functions. Human IL-10 (hIL-10) has both stimulatory and inhibitory effects on a wide variety of cell types. Viral IL-10 (vIL-10) possesses only a subset of hIL-10's activities, predominantly its suppression of cytokine synthesis by T helper type 1 clones. In the present report, we evaluated tissue accumulation and biological activity of hIL-10 and vIL-10in vivoin individual organs by using a first-generation adenoviral (Ad) vector administered intratracheally and intravenously. We report the observation that Ad vectors delivering vIL-10, but not hIL-10, are associated with prolonged expression in the lung (>42 days) when delivered intratracheally. In contrast, there was no prolongation in vIL-10 expression when Ad vectors were intravenously administered, although vIL-10 levels in the tissue, but not serum, were markedly increased relative to hIL-10. Moreover, we report an augmented capacity of expressed vIL-10 versus hIL-10 to suppress the acute inflammatory responses in the lung to intratracheal administration of Ad. These findings confirm fundamental differences in Ad-induced expression of vIL-10 and hIL-10 when administered to the lungs. The results further suggest that Ad vectors expressing vIL-10 may have a role as anti-inflammatory agents in the treatment of acute and chronic lung inflammation.
Presynaptic regulation of recurrent excitation by D1 receptors in prefrontal circuits
Authors: Gao Wen-Jun , Krimer Leonid S. , Goldman-Rakic Patricia S.
Published: July 2012

The prefrontal cortex plays a fundamental role in the working
memory functions of the cerebral cortex and is also the site of
dysfunction in several neurological and psychiatric disorders,
including schizophrenia. Prefrontal neurons are distinguished by their
capacity for sustained activity during the time a stimulus is held in
memory, and this mnemonic response is considered a substrate for a
variety of cognitive functions. The neuronal basis for sustained
activity in prefrontal neurons is unknown but is thought to involve
recurrent excitation among pyramidal neurons. Recent studies in awake
behaving monkeys have demonstrated that the persistent activity in
prefrontal neurons is modulated by dopamine. To examine the mechanisms
by which dopamine might modulate transmission in local excitatory
circuits, we have performed dual whole-cell recordings in connected
pyramidal cell pairs with and without dopamine application. We find
that dopamine reduces the efficacy of unitary excitatory
neurotransmission in layer V pyramidal cells by decreasing its
reliability. These effects, which are reproduced by a selective D1
agonist and blocked by a D1 antagonist, are independent of voltage
changes and are not attenuated by blockade of sodium and potassium
channels in the postsynaptic neurons. We conclude that attenuation of
local horizontal excitatory synaptic transmission in layer V pyramidal
neurons by dopamine is through D1 actions at a presynaptic site.
Direction of motion discrimination after early lesions of striate cortex (V1) of the macaque monkey
Authors: Moore Tirin , Rodman Hillary R. , Gross Charles G.
Published: July 2012

Previous studies have established that humans and monkeys with
damage to striate cortex are able to detect and localize bright targets
within the resultant scotoma. Electrophysiological evidence in monkeys
suggests that residual vision also might include sensitivity to
direction of visual motion. We tested whether macaque monkeys with
longstanding lesions of striate cortex (V1), sustained in infancy,
could discriminate visual stimuli on the basis of direction of motion.
Three monkeys with unilateral striate cortex lesions sustained in
infancy were tested 2–5 years postlesion on a direction of motion
discrimination task. Each monkey was trained to make saccadic eye
movements to a field of moving dots or to withhold such eye movements,
depending on the direction of motion in a coherent random dot display.
With smaller motion displays, monkeys were unable to detect or
discriminate motion within the scotoma, although they could
discriminate moving from static stimuli. Yet, each monkey was able to
discriminate direction of motion when the motion stimulus was larger,
but still confined to the scotoma. The results demonstrate that the
recovery after infant damage to striate cortex includes some
sensitivity to direction of visual motion.
Oligomerization of opioid receptors with β
2
-adrenergic receptors: A role in trafficking and mitogen-activated protein kinase activation
Authors: Jordan B. A. , Trapaidze N. , Gomes I. , Nivarthi R. , Devi L. A.
Published: July 2012

G-protein-coupled receptors (GPCRs) have recently joined the list
of cell surface receptors that dimerize. Dimerization has been shown to
alter the ligand-binding, signaling, and trafficking properties of
these receptors. Recent studies have shown that GPCRs heterodimerize
with closely related members, resulting in the modulation of their
function. In this study, we have attempted to determine whether members
of GPCR superfamilies that couple to different families of G-proteins
can associate and form oligomers. We chose the β
2
adrenergic receptor that couples to stimulatory G-proteins and δ &
κ opioid receptors that couple to inhibitory G-proteins.
β
2
and δ receptors undergo robust agonist-mediated
endocytosis, whereas κ receptors do not. We find that when
coexpressed, β
2
receptors can form heteromeric complexes
with both δ and κ receptors. This heterooligomerization does
not significantly alter the ligand binding or coupling properties of
the receptors. However, it affects the trafficking properties of
the receptors. For example, we find that δ receptors, when
coexpressed with β
2
receptors, undergo
isoproterenol-mediated endocytosis. Conversely, β
2
receptors in these cells undergo etorphine-mediated endocytosis.
However, β
2
receptors, when coexpressed with κ
receptors, undergo neither opioid- nor isoproterenol-mediated
endocytosis. Moreover, these cells exhibit a substantial decrease in
the isoproterenol-induced phosphorylation of mitogen-activated protein
kinases. Taken together, these results provide direct evidence of
heteromerization of GPCRs that couple to different types of G-proteins,
which results in the modulation of receptor trafficking and signal
transduction.
Activation ofReggene, a gene for insulin-producing β-cell regeneration: Poly(ADP-ribose) polymerase bindsRegpromoter and regulates the transcription by autopoly(ADP-ribosyl)ation
Authors: Akiyama Takako , Takasawa Shin , Nata Koji , Kobayashi Seiichi , Abe Michiaki , Shervani Nausheen J. , Ikeda Takayuki , Nakagawa Kei , Unno Michiaki , Matsuno Seiki , Okamoto Hiroshi
Published: July 2012

The regeneration of pancreatic islet β cells is important for the prevention and cure ofdiabetes mellitus. We have demonstrated that the administration of poly(ADP-ribose) synthetase/polymerase (PARP) inhibitors such as nicotinamide to 90% depancreatized rats induces islet regeneration. From the regenerating islet-derived cDNA library, we have isolatedReg(regenerating gene) and demonstrated that Reg protein induces β-cell replication via the Reg receptor and ameliorates experimental diabetes. However, the mechanism by whichReggene is activated in β cells has been elusive. In this study, we found that the combined addition of IL-6 and dexamethasone induced the expression ofReggene in β cells and that PARP inhibitors enhanced the expression. Reporter gene assays revealed that the −81 ≈ −70 region (TGCCCCTCCCAT) of theReggene promoter is acis-element for the expression ofReggene. Gel mobility shift assays showed that the active transcriptional DNA/protein complex was formed by the stimulation with IL-6 and dexamethasone. Surprisingly, PARP bound to thecis-element and was involved in the active transcriptional DNA/protein complex. The DNA/protein complex formation was inhibited depending on the autopoly(ADP-ribosyl)ation of PARP in the complex. Thus, PARP inhibitors enhance the DNA/protein complex formation forReggene transcription and stabilize the complex by inhibiting the autopoly(ADP-ribosyl)ation of PARP.
An anthelmintic compound, nafuredin, shows selective inhibition of complex I in helminth mitochondria
Authors: Ōmura Satoshi , Miyadera Hiroko , Ui Hideaki , Shiomi Kazuro , Yamaguchi Yuuichi , Masuma Rokuro , Nagamitsu Tohru , Takano Daisuke , Sunazuka Toshiaki , Harder Achim , Kölbl Heinz , Namikoshi Michio , Miyoshi Hideto , Sakamoto Kimitoshi , Kita Kiyoshi
Published: July 2012

Infections with parasitic helminths are important causes of
morbidity and mortality worldwide. New drugs that are parasite specific
and minimally toxic to the host are needed to counter these infections
effectively. Here we report the finding of a previously unidentified
compound, nafuredin, from
Aspergillus niger
. Nafuredin
inhibits NADH-fumarate reductase (complexes I + II) activity, a unique
anaerobic electron transport system in helminth mitochondria, at nM
order. It competes for the quinone-binding site in complex I and shows
high selective toxicity to the helminth enzyme. Moreover, nafuredin
exerts anthelmintic activity against
Haemonchus
contortus
in
in vivo
trials with sheep. Thus,
our study indicates that mitochondrial complex I is a promising target
for chemotherapy, and nafuredin is a potential lead compound as an
anthelmintic isolated from microorganisms.
RNA degradosomes existin vivoinEscherichia colias multicomponent complexes associated with the cytoplasmic membrane via the N-terminal region of ribonuclease E
Authors: Liou Gunn-Guang , Jane Wann-Neng , Cohen Stanley N. , Lin Na-Sheng , Lin-Chao Sue
Published: July 2012

RNase E isolated fromEscherichia coliis contained in a multicomponent “degradosome” complex with other proteins implicated in RNA decay. Earlier work has shown that the C-terminal region of RNase E is a scaffold for the binding of degradosome components and has identified specific RNase E segments necessary for its interaction with polynucleotide phosphorylase (PNPase), RhlB RNA helicase, and enolase. Here, we report electron microscopy studies that use immunogold labeling and freeze–fracture methods to show that degradosomes existin vivoinE. colias multicomponent structures that associate with the cytoplasmic membrane via the N-terminal region of RNase E. Whereas PNPase and enolase are present inE. coliin large excess relative to RNase E and therefore are detected in cells largely as molecules unlinked to the RNase E scaffold, immunogold labeling and biochemical analyses show that helicase is present in approximately equimolar amounts to RNase E at all cell growth stages. Our findings, which establish the existence and cellular location of RNase E-based degradosomesin vivoinE. coli, also suggest that RNA processing and decay may occur at specific sites within cells.
Glutamic and aminoadipic semialdehydes are the main carbonyl products of metal-catalyzed oxidation of proteins
Authors: Requena Jesús R. , Chao Chien-Chung , Levine Rodney L. , Stadtman Earl R.
Published: July 2012

Metal-catalyzed oxidation results in loss of function and
structural alteration of proteins. The oxidative process affects a
variety of side amino acid groups, some of which are converted to
carbonyl compounds. Spectrophotometric measurement of these moieties,
after their reaction with 2,4-dinitrophenylhydrazine, is a simple,
accurate technique that has been widely used to reveal increased levels
of protein carbonyls in aging and disease. We have initiated studies
aimed at elucidating the chemical nature of protein carbonyls. Methods
based on gas chromatography/mass spectrometry with isotopic dilution
were developed for the quantitation of glutamic and aminoadipic
semialdehydes after their reduction to hydroxyaminovaleric and
hydroxyaminocaproic acids. Analysis of model proteins oxidized
in vitro
by Cu
2+
/ascorbate revealed that
these two compounds constitute the majority of protein carbonyls
generated. Glutamic and aminoadipic semialdehydes were also detected in
rat liver proteins, where they constitute ≈60% of the total protein
carbonyl value. Aminoadipic semialdehyde was also measured in protein
extracts from HeLa cells, and its level increased as a consequence of
oxidative stress to cell cultures. These results indicate that glutamic
and aminoadipic semialdehydes are the main carbonyl products of
metal-catalyzed oxidation of proteins, and that this reaction is a
major route leading to the generation of protein carbonyls in
biological samples.