bluuebunny/crossref_metadata_2025 huggingface dataset:
Local equilibrium and off-equilibrium thermoelectric effects in silicon semiconductors
Authors: Muscato O. , Di Stefano V.
Published: November 2011

Thermoelectric effects in bulk silicon are investigated by using a hydrodynamic model for the electron-phonon system, derived in the framework of extended thermodynamics. This model consists of a set of balance equations, where the higher order moments and the production terms are completely determined without any fitting procedure. If the system is in local thermal equilibrium, the thermopower and Peltier coefficients have been obtained and the phonon-drag contribution has been recovered. The model allows us to define and evaluate the Peltier coefficient when the system is out of thermal equilibrium.
Characteristics of a-GaN films and a-AlGaN/GaN heterojunctions prepared on r-sapphire by two-stage growth process
Authors: Polyakov A. Y. , Jang Lee-Woon , Smirnov N. B. , Govorkov A. V. , Kozhukhova E. A. , Yugova T. G. , Reznik V. Y. , Pearton S. J. , Baik Kwang Hyeon , Hwang Sung-Min , Jung Sukkoo , Lee In-Hwan
Published: November 2011

The electrical properties, presence of deep electron and hole traps and photoluminescence spectra were measured for undoped a-GaN films grown by metal-organic chemical vapor deposition (MOCVD) in a two-stage process using a high V/III ratio at the first stage and low V/III ratio at the second stage. Growth was performed on r-sapphire substrates with a high temperature GaN nucleation layer. The films showed a full width at half maximum of 450-470 arcseconds for the (11-20) x-ray rocking curve with little anisotropy with respect to the sample rotation around the growth direction. The stacking fault (SF) density determined by selective etching was ∼5 × 104 cm−1. The residual donor concentration was 1014–1015 cm−3, with a very low density (2.5 × 1013 cm−3) of electron traps located at Ec − 0.6 eV, which are believed to be one of the major non-radiative recombination centers in nonpolar GaN. Consequently, the films showed a high intensity of bandedge luminescence with negligible contribution from defect bands associated with SFs. In contrast to previously studied nonpolar GaN films, the a-GaN layers showed a high concentration of gallium-vacancy-related acceptors near Ev + 1 eV and a strong yellow luminescence band, both indicating that growth conditions were effectively N-rich. a-AlGaN/GaN heterojunctions with thin heavily Si doped AlGaN barriers made on a-GaN substrates showed two-dimensional electron gas (2DEG) concentrations of 1.2 × 1013 cm−3, with 2DEG mobility of 80 cm2/Vs. Capacitance-voltage profiling of Schottky diodes on these HJs suggest that the 2DEG is fully depleted by the built-in voltage of the Schottky diode.
Silver/silicon dioxide/silver sandwich films in the blue-to-red spectral regime with negative-real refractive index
Authors: Jen Yi-Jun , Lakhtakia Akhlesh , Yu Ching-Wei , Jhou Jheng-Jie , Wang Wei-Hao , Lin Meng-Jie , Wu Huang-Ming , Liao Hung-Sheng
Published: November 2011

Sandwich films comprising arrays of silver/silicon-dioxide/silver nanosandwiches were grown by the oblique angle deposition technique. For normally incident light, these films present a negative-real refractive index (NRRI) over almost the entire visible regime, with quite high transparency and figures of merit, regardless of the orientation of the incident electric field. A broad distribution of nanosandwich sizes is responsible for the breadth of the NRRI spectral regime.
Protecting superconducting qubits from radiation
Authors: Córcoles Antonio D. , Chow Jerry M. , Gambetta Jay M. , Rigetti Chad , Rozen J. R. , Keefe George A. , Beth Rothwell Mary , Ketchen Mark B. , Steffen M.
Published: November 2011

We characterize a superconducting qubit before and after embedding it along with its package in an absorptive medium. We observe a drastic improvement in the effective qubit temperature and over a tenfold improvement in the relaxation time up to 5.7 μs. Our results suggest the presence of external radiation inside the cryogenic apparatus can be a limiting factor for both qubit initialization and coherence. Calculations support the hypothesis that the relaxation is not limited by direct coupling of thermal photons to the qubit prior to embedding, but by dissipation arising from quasiparticle generation.
Increased photoluminescence of strain-reduced, high-Sn composition Ge1−xSnx alloys grown by molecular beam epitaxy
Authors: Chen Robert , Lin Hai , Huo Yijie , Hitzman Charles , Kamins Theodore I. , Harris James S.
Published: November 2011

We synthesized up to Ge0.914Sn0.086 alloys on (100) GaAs/InyGa1−yAs buffer layers using molecular beam epitaxy. The buffer layers enable engineered control of strain in the Ge1−xSnx layers to reduce strain-related defects and precipitation. Samples grown under similar conditions show a monotonic increase in the integrated photoluminescence (PL) intensity as the Sn composition is increased, indicating changes in the bandstructure favorable for optoelectronics. We account for bandgap changes from strain and composition to determine a direct bandgap bowing parameter of b = 2.1 ± 0.1. According to our models, these are the first Ge1−xSnx samples that are both direct-bandgap and exhibit PL.
Thermal and optical characterization of resonant coupling between surface plasmon polariton and semiconductor waveguides
Authors: Summers Joseph A. , Ram Rajeev J.
Published: November 2011

Resonant coupling between an Au-InP surface plasmon polariton (SPP) and an InP/InGaAsP ridge waveguide is investigated. The general design requirements for evanescent coupling between a low-loss waveguide and a highly absorptive SPP are described, and experimental results are presented for fabricated devices. Coupling from the ridge to the SPP is confirmed using fiber-to-fiber optical power measurements, and thermoreflectance imaging is used to directly measure power coupled to the SPP along the length of the metal waveguide. The role of the thin native oxide at the Au-InP interface is also explored and found to have a significant impact on coupling.
Investigation of the negative differential resistance reproducibility in AlN/GaN double-barrier resonant tunnelling diodes
Authors: Boucherit M. , Soltani A. , Monroy E. , Rousseau M. , Deresmes D. , Berthe M. , Durand C. , De Jaeger J.-C.
Published: November 2011

AlN/GaN double-barrier resonant tunnelling diodes were grown by molecular beam epitaxy on GaN/sapphire template and processed into mesa diameters from 2 μm to 4 μm. The current-voltage characteristics were carried out in direct current operation and under-high vacuum. A sharp negative differential resistance (NDR) was detected in the forward bias at 120 K. The NDR was observed for the mesa size of 2 μm at 4 V with a peak-to-valley current ratio of 3.5. The measurement conditions were chosen to make NDR reproducible more than 50 times and apparent in both scan voltage directions after electrical treatment.
Optical and electrical properties of spray pyrolysis deposited nano-crystalline BiFeO3 films
Authors: Venkateswarlu Annapu Reddy , Varma G. D. , Nath R.
Published: November 2011

The nano-crystalline BiFeO3 were prepared under controlled substrate temperature by spray pyrolysis method. Their structural, optical and electrical properties were studied and correlated. A blueshift (Δλ ∼ 8.17 nm) in the absorbance peaks was observed in the films with decrease in grain size. The absorption coefficient spectra show defect transitions at 1.9 and 2.3 eV in large grain size films due to oxygen vacancies. The lowest leakage was observed in smaller grain size (< 20 nm) films due to negligible oxygen vacancies, smooth surface roughness and large energy bang gap. The Poole-Frankel conduction mechanism has been found to be the predominant mechanism for the leakage current.
Contemporary Experimental Aesthetics: State of the Art Technology
Authors: Locher Paul
Published: November 2011

The purpose of this essay is to provide the reader with a brief overview of several recent person-artifact-context relational models that explain the complex interaction of the processes that underlie an ongoing aesthetic experience with visual art forms. Recent progress towards a comprehensive understanding of these processes has been made possible in large part by experimental approaches that take advantage of recent advances in computer technology and electronic sophistication. To illustrate this point, three experimental techniques at the forefront of the field of experimental aesthetics are highlighted here. They include the investigation of viewers' body postural adjustments to depicted pictorial depth and movement in paintings; the use of hand-held computers known as personal data assistants to record audience members' on-going emotional reactions to live performances of dance; and the contribution of audio tour information to museum visitors' interaction with and aesthetic evaluation of sculptures and paintings. Finally, the eMotion: Mapping Museum Experience project, which has the potential to make a tremendous contribution to the understanding of the complex interaction of factors that contribute to a museum visitor's experience, is described.
Cognitive Mechanisms for Explaining Dynamics of Aesthetic Appreciation
Authors: Carbon Claus-Christian
Published: November 2011

For many domains aesthetic appreciation has proven to be highly reliable. Evaluations of facial attractiveness, for instance, show high internal consistencies and impressively high inter-rater reliabilities, even across cultures. This indicates general mechanisms underlying such evaluations. It is, however, also obvious that our taste for specific objects is not always stable—in some realms such stability is hardly conceivable at all since aesthetic domains such as fashion, design, or art are inherently very dynamic. Gaining insights into the cognitive mechanisms that trigger and enable corresponding changes of aesthetic appreciation is of particular interest for psychologists as this will probably reveal essential mechanisms of aesthetic evaluations per se. The present paper develops a two-step model, dynamically adapting itself, which accounts for typical dynamics of aesthetic appreciation found in different research areas such as art history, philosophy, and psychology. The first step assumes singular creative sources creating and establishing innovative material towards which, in a second step, people adapt by integrating it into their visual habits. This inherently leads to dynamic changes of the beholders' aesthetic appreciation.
Illusory Rotation of a Spoked Wheel
Authors: Anstis Stuart , Rogers Brian
Published: November 2011

A disk was divided into 16 stationary sectors of different grey levels that stepped around clockwise. When thin stationary spokes of constant mid-grey separated the sectors, the spokes showed robust and striking counterclockwise apparent motion, and when stopped, they gave a brisk clockwise motion aftereffect. The spokes had to match the grey of some of the sectors. We attribute these effects to small displacements across the thickness of the spokes that stimulated hard-wired motion detectors.
Duboisia Pituri: A Natural History
Authors: Keogh Luke
Published: November 2011

In the 1870s, an intense quest revealed to scientists that pituri, an important Aboriginal commodity, was sourced from the plant Duboisia hopwoodii?a shrub named after a well-known colonist. But it was Aboriginal people and white explorer-pastoralists from the Mulligan River region in far western Queensland who provided the samples and alerted scientists to the important chemical properties of pituri. Subsequently, there was a proposal to change the name of the plant to Duboisia pituri. Whom should the plant have been named after, the colonist or the Aborigine?
Wilbur Norman Christiansen 1913 - 2007
Authors: Frater R. H. , Goss W. M.
Published: November 2011

W. N. (?Chris') Christiansen was an innovative and influential radio astronomy pioneer. The hallmarks of his long and distinguished career in science and engineering, spanning almost five decades, were his inventiveness and his commitment to, and success with, large-scale projects. These projects were the outcome of his innovative skill as physicist and engineer. Paralleling this was his equal commitment to forging strong international links and friendships, leading to his election as Vice-President of the International Astronomical Union for the years 1964 to 1970, as President of the International Union of Radio Science, URSI, from 1978 to 1981, and subsequently as Honorary Life President in 1984, and as Foreign Secretary of the Australian Academy of Science from 1981 to 1985. Major subsequent developments in radio astronomy and wireless communications on the global scene stand as a legacy to Chris's approach to his work and to the development of those who worked with him.
FGF2 gene transfer restores hippocampal functions in mouse models of Alzheimer's disease and has therapeutic implications for neurocognitive disorders
Authors: Kiyota Tomomi , Ingraham Kaitlin L. , Jacobsen Michael T. , Xiong Huangui , Ikezu Tsuneya
Published: November 2011

The adult hippocampus plays a central role in memory formation, synaptic plasticity, and neurogenesis. The subgranular zone of the dentate gyrus contains neural progenitor cells with self-renewal and multilineage potency. Transgene expression of familial Alzheimer's disease-linked mutants of β-amyloid precursor protein (APP) and presenilin-1 leads to a significant inhibition of neurogenesis, which is potentially linked to age-dependent memory loss. To investigate the effect of neurogenesis on cognitive function in a relevant disease model, FGF2 gene is delivered bilaterally to the hippocampi of APP+presenilin-1 bigenic mice via an adenoassociated virus serotype 2/1 hybrid (AAV2/1-FGF2). Animals injected with AAV2/1-FGF2 at a pre- or postsymptomatic stage show significantly improved spatial learning in the radial arm water maze test. A neuropathological investigation demonstrates that AAV2/1-FGF2 injection enhances the number of doublecortin, BrdU/NeuN, and c-fos–positive cells in the dentate gyrus, and the clearance of fibrillar amyloid-β peptide (Aβ) in the hippocampus. AAV2/1-FGF2 injection also enhances long-term potentiation in another APP mouse model (J20) compared with control AAV2/1-GFP–injected littermates. An in vitro study confirmed the enhanced neurogenesis of mouse neural stem cells by direct AAV2/1-FGF2 infection in an Aβ oligomer-sensitive manner. Further, FGF2 enhances Aβ phagocytosis in primary cultured microglia, and reduces Aβ production from primary cultured neurons after AAV2/1-FGF2 infection. Thus, our data indicate that virus-mediated FGF2 gene delivery has potential as an alternative therapy of Alzheimer's disease and possibly other neurocognitive disorders.
Marriage exchanges, seed exchanges, and the dynamics of manioc diversity
Authors: Delêtre Marc , McKey Doyle B. , Hodkinson Trevor R.
Published: November 2011

The conservation of crop genetic resources requires understanding the different variables—cultural, social, and economic—that impinge on crop diversity. In small-scale farming systems, seed exchanges represent a key mechanism in the dynamics of crop genetic diversity, and analyzing the rules that structure social networks of seed exchange between farmer communities can help decipher patterns of crop genetic diversity. Using a combination of ethnobotanical and molecular genetic approaches, we investigated the relationships between regional patterns of manioc genetic diversity in Gabon and local networks of seed exchange. Spatially explicit Bayesian clustering methods showed that geographical discontinuities of manioc genetic diversity mirror major ethnolinguistic boundaries, with a southern matrilineal domain characterized by high levels of varietal diversity and a northern patrilineal domain characterized by low varietal diversity. Borrowing concepts from anthropology—kinship, bridewealth, and filiation—we analyzed the relationships between marriage exchanges and seed exchange networks in patrilineal and matrilineal societies. We demonstrate that, by defining marriage prohibitions, kinship systems structure social networks of exchange between farmer communities and influence the movement of seeds in metapopulations, shaping crop diversity at local and regional levels.
Cytoplasmic activation-induced cytidine deaminase (AID) exists in stoichiometric complex with translation elongation factor 1α (eEF1A)
Authors: Häsler Julien , Rada Cristina , Neuberger Michael S.
Published: November 2011

Activation-induced cytidine deaminase (AID) is a B lymphocyte-specific DNA deaminase that acts on the Ig loci to trigger antibody gene diversification. Most AID, however, is retained in the cytoplasm and its nuclear abundance is carefully regulated because off-target action of AID leads to cancer. The nature of the cytosolic AID complex and the mechanisms regulating its release from the cytoplasm and import into the nucleus remain unknown. Here, we show that cytosolic AID in DT40 B cells is part of an 11S complex and, using an endogenously tagged AID protein to avoid overexpression artifacts, that it is bound in good stoichiometry to the translation elongation factor 1 alpha (eEF1A). The AID/eEF1A interaction is recapitulated in transfected cells and depends on the C-terminal domain of eEF1A (which is not responsible for GTP or tRNA binding). The eEF1A interaction is destroyed by mutations in AID that affect its cytosolic retention. These results suggest that eEF1A is a cytosolic retention factor for AID and extend on the multiple moonlighting functions of eEF1A.
T cell immunoglobulin and mucin protein-3 (Tim-3)/Galectin-9 interaction regulates influenza A virus-specific humoral and CD8 T-cell responses
Authors: Sharma Shalini , Sundararajan Aarthi , Suryawanshi Amol , Kumar Naveen , Veiga-Parga Tamara , Kuchroo Vijay K. , Thomas Paul G. , Sangster Mark Y. , Rouse Barry T.
Published: November 2011

Reactions to pathogens are usually tuned to effect immunity and limit tissue damage. Several host counterinflammatory mechanisms inhibit tissue damage but these may also act to constrain the effectiveness of immunity to acute infections, as we demonstrate in mice acutely infected with influenza A virus (IAV). We show that compared with wild type (WT), galectin-9 knockout (G9KO) mice mounted a more robust acute phase virus-specific CD8 T-cell response as well as higher and more rapid virus-specific serum IgM, IgG, and IgA responses and also cleared virus more rapidly than did WT mice. Blocking galectin-9 signals to Tim-3–expressing cells using a Tim-3 fusion protein resulted in improved immune responses in WT mice. When IAV immune mice were challenged with a heterologous IAV, the secondary IAV-specific CD8 T-cell responses were four- to fivefold higher in G9KO compared with WT mice. Our results indicate that manipulating galectin signals may represent a convenient approach to improve immune responses to some vaccines.
Light-dependent attenuation of phycoerythrin gene expression reveals convergent evolution of green light sensing in cyanobacteria
Authors: Bezy Ryan P. , Wiltbank Lisa , Kehoe David M.
Published: November 2011

The colorful process of chromatic acclimation allows many cyanobacteria to change their pigmentation in response to ambient light color changes. In red light, cells produce red-absorbing phycocyanin (PC), whereas in green light, green-absorbing phycoerythrin (PE) is made. Controlling these pigment levels increases fitness by optimizing photosynthetic activity in different light color environments. The light color sensory system controlling PC expression is well understood, but PE regulation has not been resolved. In the filamentous cyanobacterium
Fremyella diplosiphon
UTEX 481, two systems control PE synthesis in response to light color. The first is the Rca pathway, a two-component system controlled by a phytochrome-class photoreceptor, which transcriptionally represses
cpeCDESTR
(
cpeC
) expression during growth in red light. The second is the Cgi pathway, which has not been characterized. We determined that the Cgi system also regulates PE synthesis by repressing
cpeC
expression in red light, but acts posttranscriptionally, requiring the region upstream of the CpeC translation start codon.
cpeC
RNA stability was comparable in
F. diplosiphon
cells grown in red and green light, and a short transcript that included the 5′ region of
cpeC
was detected, suggesting that the Cgi system operates by transcription attenuation. The roles of four predicted stem–loop structures within the 5′ region of
cpeC
RNA were analyzed. The putative stem–loop 31 nucleotides upstream of the translation start site was required for Cgi system function. Thus, the Cgi system appears to be a unique type of signal transduction pathway in which the attenuation of
cpeC
transcription is regulated by light color.
Prototypical model for tensional wrinkling in thin sheets
Authors: Davidovitch Benny , Schroll Robert D. , Vella Dominic , Adda-Bedia Mokhtar , Cerda Enrique A.
Published: November 2011

The buckling and wrinkling of thin films has recently seen a surge of interest among physicists, biologists, mathematicians, and engineers. This activity has been triggered by the growing interest in developing technologies at ever-decreasing scales and the resulting necessity to control the mechanics of tiny structures, as well as by the realization that morphogenetic processes, such as the tissue-shaping instabilities occurring in animal epithelia or plant leaves, often emerge from mechanical instabilities of cell sheets. Although the most basic buckling instability of uniaxially compressed plates was understood by Euler more than two centuries ago, recent experiments on nanometrically thin (ultrathin) films have shown significant deviations from predictions of standard buckling theory. Motivated by this puzzle, we introduce here a theoretical model that allows for a systematic analysis of wrinkling in sheets far from their instability threshold. We focus on the simplest extension of Euler buckling that exhibits wrinkles of finite length—a sheet under axisymmetric tensile loads. The first study of this geometry, which is attributed to Lamé, allows us to construct a phase diagram that demonstrates the dramatic variation of wrinkling patterns from near-threshold to far-from-threshold conditions. Theoretical arguments and comparison to experiments show that the thinner the sheet is, the smaller is the compressive load above which the far-from-threshold regime emerges. This observation emphasizes the relevance of our analysis for nanomechanics applications.
Biliverdin inhibits Toll-like receptor-4 (TLR4) expression through nitric oxide-dependent nuclear translocation of biliverdin reductase
Authors: Wegiel Barbara , Gallo David , Csizmadia Eva , Roger Thierry , Kaczmarek Elzbieta , Harris Clair , Zuckerbraun Brian S. , Otterbein Leo E.
Published: November 2011

The cellular response to an inflammatory stressor requires a proinflammatory cellular activation followed by a controlled resolution of the response to restore homeostasis. We hypothesized that biliverdin reductase (BVR) by binding biliverdin (BV) quells the cellular response to endotoxin-induced inflammation through phosphorylation of endothelial nitric oxide synthase (eNOS). The generated NO, in turn, nitrosylates BVR, leading to nuclear translocation where BVR binds to the Toll-like receptor-4 (TLR4) promoter at the Ap-1 sites to block transcription. We show in macrophages that BV-induced eNOS phosphorylation (Ser-1177) and NO production are mediated in part by Ca
2+
/calmodulin-dependent kinase kinase. Furthermore, we show that BVR is S-nitrosylated on one of three cysteines and that this posttranslational modification is required for BVR-mediated signaling. BV-induced nuclear translocation of BVR and inhibition of TLR4 expression is lost in macrophages derived from

Enos
−/−

mice. In vivo in mice, BV provides protection from acute liver damage and is dependent on the availability of NO. Collectively, we elucidate a mechanism for BVR in regulating the inflammatory response to endotoxin that requires eNOS-derived NO and TLR4 signaling in macrophages.
A homolog of male sex-determining factor SRY cooperates with a transposon-derived CENP-B protein to control sex-specific directed recombination
Authors: Matsuda Emiko , Sugioka-Sugiyama Rie , Mizuguchi Takeshi , Mehta Sameet , Cui Bowen , Grewal Shiv I. S.
Published: November 2011

Schizosaccharomyces pombe
cells switch mating type by replacing genetic information at the expressed
mat1
locus with sequences copied from
mat2-P
or
mat3-M
silent donor loci. The choice of donor locus is dictated by cell type, such that
mat2
is the preferred donor in
M
cells and
mat3
is the preferred donor in
P
cells. Donor choice involves a recombination-promoting complex (RPC) containing Swi2 and Swi5. In
P
cells, the RPC localizes to a specific DNA element located adjacent to
mat3
, but in
M
cells it spreads across the silent mating-type region, including
mat2-P
. This differential distribution of the RPC regulates nonrandom choice of donors. However, cell-type–specific differences in RPC localization are not understood. Here we show that the
mat1-M
–encoded factor Mc, which shares structural and functional similarities with the male sex-determining factor SRY, is highly enriched at the
swi2
and
swi5
loci and promotes elevated levels of RPC components. Loss of Mc reduces Swi2 and Swi5 to levels comparable to those in
P
cells and disrupts RPC spreading across the
mat2/3
region. Mc also localizes to loci expressed preferentially in
M
cells and to retrotransposon LTRs. We demonstrate that Mc localization at LTRs and at
swi2
requires Abp1, a homolog of transposon-derived CENP-B protein and that loss of Abp1 impairs Swi2 protein expression and the donor choice mechanism. These results suggest that Mc modulates levels of recombination factors, which is important for mating-type donor selection and for the biased gene conversion observed during meiosis, where
M
cells serve as preferential donors of genetic information.
Genetic dissection of the biotic stress response using a genome-scale gene network for rice
Authors: Lee Insuk , Seo Young-Su , Coltrane Dusica , Hwang Sohyun , Oh Taeyun , Marcotte Edward M. , Ronald Pamela C.
Published: November 2011

Rice is a staple food for one-half the world's population and a model for other monocotyledonous species. Thus, efficient approaches for identifying key genes controlling simple or complex traits in rice have important biological, agricultural, and economic consequences. Here, we report on the construction of RiceNet, an experimentally tested genome-scale gene network for a monocotyledonous species. Many different datasets, derived from five different organisms including plants, animals, yeast, and humans, were evaluated, and 24 of the most useful were integrated into a statistical framework that allowed for the prediction of functional linkages between pairs of genes. Genes could be linked to traits by using guilt-by-association, predicting gene attributes on the basis of network neighbors. We applied RiceNet to an important agronomic trait, the biotic stress response. Using network guilt-by-association followed by focused protein–protein interaction assays, we identified and validated, in planta, two positive regulators, LOC_Os01g70580 (now Regulator of XA21; ROX1) and LOC_Os02g21510 (ROX2), and one negative regulator, LOC_Os06g12530 (ROX3). These proteins control resistance mediated by rice XA21, a pattern recognition receptor. We also showed that RiceNet can accurately predict gene function in another major monocotyledonous crop species, maize. RiceNet thus enables the identification of genes regulating important crop traits, facilitating engineering of pathways critical to crop productivity.
High
T

c

electron doped Ca
10
(Pt
3
As
8
)(Fe
2
As
2
)
5
and Ca
10
(Pt
4
As
8
)(Fe
2
As
2
)
5
superconductors with skutterudite intermediary layers
Authors: Ni Ni , Allred Jared M. , Chan Benny C. , Cava Robert Joseph
Published: November 2011

It has been argued that the very high transition temperatures of the highest
T

c

cuprate superconductors are facilitated by enhanced CuO
2
plane coupling through heavy metal oxide intermediary layers. Whether enhanced coupling through intermediary layers can also influence
T

c

in the new high
T

c

iron arsenide superconductors has never been tested due the lack of appropriate systems for study. Here we report the crystal structures and properties of two iron arsenide superconductors, Ca
10
(Pt
3
As
8
)(Fe
2
As
2
)
5
(the “10-3-8 phase”) and Ca
10
(Pt
4
As
8
)(Fe
2
As
2
)
5
(the “10-4-8 phase”). Based on -Ca-(Pt

n

As
8
)-Ca-Fe
2
As
2
- layer stacking, these are very similar compounds for which the most important differences lie in the structural and electronic characteristics of the intermediary platinum arsenide layers. Electron doping through partial substitution of Pt for Fe in the FeAs layers leads to
T

c

of 11 K in the 10-3-8 phase and 26 K in the 10-4-8 phase. The often-cited empirical rule in the arsenide superconductor literature relating
T

c

to As-Fe-As bond angles does not explain the observed differences in
T

c

of the two phases; rather, comparison suggests the presence of stronger FeAs interlayer coupling in the 10-4-8 phase arising from the two-channel interlayer interactions and the metallic nature of its intermediary Pt
4
As
8
layer. The interlayer coupling is thus revealed as important in enhancing
T

c

in the iron pnictide superconductors.
In vitro reconstitution and steady-state analysis of the fatty acid synthase from
Escherichia coli
Authors: Yu Xingye , Liu Tiangang , Zhu Fayin , Khosla Chaitan
Published: November 2011

Microbial fatty acid derivatives are emerging as promising alternatives to fossil fuel derived transportation fuels. Among bacterial fatty acid synthases (FAS), the
Escherichia coli
FAS is perhaps the most well studied, but little is known about its steady-state kinetic behavior. Here we describe the reconstitution of
E. coli
FAS using purified protein components and report detailed kinetic analysis of this reconstituted system. When all ketosynthases are present at 1 μM, the maximum rate of free fatty acid synthesis of the FAS exceeded 100 μM/ min. The steady-state turnover frequency was not significantly inhibited at high concentrations of any substrate or cofactor. FAS activity was saturated with respect to most individual protein components when their concentrations exceeded 1 μM. The exceptions were FabI and FabZ, which increased FAS activity up to concentrations of 10 μM; FabH and FabF, which decreased FAS activity at concentrations higher than 1 μM; and
holo
-ACP and TesA, which gave maximum FAS activity at 30 μM concentrations. Analysis of the S36T mutant of the ACP revealed that the unusual dependence of FAS activity on
holo
-ACP concentration was due, at least in part, to the acyl-phosphopantetheine moiety. MALDI-TOF mass spectrometry analysis of the reaction mixture further revealed medium and long chain fatty acyl-ACP intermediates as predominant ACP species. We speculate that one or more of such intermediates are key allosteric regulators of FAS turnover. Our findings provide a new basis for assessing the scope and limitations of using
E. coli
as a biocatalyst for the production of diesel-like fuels.
Long-term RNA interference gene therapy in a dominant retinitis pigmentosa mouse model
Authors: Jiang Li , Zhang Houbin , Dizhoor Alexander M. , Boye Shannon E. , Hauswirth William W. , Frederick Jeanne M. , Baehr Wolfgang
Published: November 2011

RNA interference (RNAi) gene silencing is a potential therapeutic strategy for dominant retinal degeneration disorders. We used self-complementary (sc) AAV2/8 vector to develop an RNAi-based gene therapy in a dominant retinal degeneration mouse model expressing bovine GCAP1(Y99C). We established an in vitro shRNA screening assay based on EGFP-tagged bovine GCAP1, and identified a shRNA that effectively silenced the bovine GCAP1 transgene with ∼80% efficiency. Subretinal injection of scAAV2/8 carrying shRNA expression cassette showed robust expression as early as 1 wk after injection. The gene silencing significantly improved photoreceptor survival, delayed disease onset, and increased visual function. Our results provide a promising strategy toward effective RNAi-based gene therapy by scAAV2/8 delivery for dominant retinal diseases.
High levels of nuclear heat-shock factor 1 (HSF1) are associated with poor prognosis in breast cancer
Authors: Santagata Sandro , Hu Rong , Lin Nancy U. , Mendillo Marc L. , Collins Laura C. , Hankinson Susan E. , Schnitt Stuart J. , Whitesell Luke , Tamimi Rulla M. , Lindquist Susan , Ince Tan A.
Published: November 2011

Heat-shock factor 1 (HSF1) is the master transcriptional regulator of the cellular response to heat and a wide variety of other stressors. We previously reported that HSF1 promotes the survival and proliferation of malignant cells. At this time, however, the clinical and prognostic significance of HSF1 in cancer is unknown. To address this issue breast cancer samples from 1,841 participants in the Nurses’ Health Study were scored for levels of nuclear HSF1. Associations of HSF1 status with clinical parameters and survival outcomes were investigated by Kaplan–Meier analysis and Cox proportional hazard models. The associations were further delineated by Kaplan–Meier analysis using publicly available mRNA expression data. Our results show that nuclear HSF1 levels were elevated in ∼80% of in situ and invasive breast carcinomas. In invasive carcinomas, HSF1 expression was associated with high histologic grade, larger tumor size, and nodal involvement at diagnosis (
P
< 0.0001). By using multivariate analysis to account for the effects of covariates, high HSF1 levels were found to be independently associated with increased mortality (hazards ratio: 1.62; 95% confidence interval: 1.21–2.17;
P
< 0.0013). This association was seen in the estrogen receptor (ER)-positive population (hazards ratio: 2.10; 95% confidence interval: 1.45–3.03;
P
< 0.0001). In public expression profiling data, high HSF1 mRNA levels were also associated with an increase in ER-positive breast cancer-specific mortality. We conclude that increased HSF1 is associated with reduced breast cancer survival. The findings indicate that HSF1 should be evaluated prospectively as an independent prognostic indicator in ER-positive breast cancer. HSF1 may ultimately be a useful therapeutic target in cancer.
Intracellular neutralization of viral infection in polarized epithelial cells by neonatal Fc receptor (FcRn)-mediated IgG transport
Authors: Bai Yu , Ye Lilin , Tesar Devin B. , Song Haichen , Zhao Deming , Björkman Pamela J. , Roopenian Derry C. , Zhu Xiaoping
Published: November 2011

IgG was traditionally thought to neutralize virions by blocking their attachment to or penetration into mucosal epithelial cells, a common site of exposure to viruses. However, we describe an intracellular neutralizing action for an influenza hemagglutinin-specific monoclonal antibody, Y8-10C2 (Y8), which has neutralizing activity only at an acidic pH. When Y8 was applied to the basolateral surface of Madin–Darby canine kidney cells expressing the rat neonatal Fc receptor for IgG (FcRn), it significantly reduced viral replication following apical exposure of the cell monolayer to influenza virus. Virus neutralization by Y8 mAb was dependent on FcRn expression and its transport of IgG. As both FcRn and Y8 mAb bind their partners only at acidic pH, the Y8 mAb is proposed to carry out its antiviral activity intracellularly. Furthermore, the virus, Y8 mAb, and FcRn colocalized within endosomes, possibly inhibiting the fusion of viral envelopes with endosomal membranes during primary uncoating, and preventing the accumulation of the neutralized viral nucleoprotein antigen in the nucleus. Prophylactic administration of Y8 mAb before viral challenge in WT mice, but not FcRn-KO mice, conferred protection from lethality, prevented weight loss, resulted in a significant reduction in pulmonary virus titers, and largely reduced virus-induced lung pathology. Thus, this study reveals an intracellular mechanism for viral neutralization in polarized epithelial cells that is dependent on FcRn-mediated transport of neutralizing IgG.
Cell-autonomous circadian clock of hepatocytes drives rhythms in transcription and polyamine synthesis
Authors: Atwood Ann , DeConde Robert , Wang Susanna S. , Mockler Todd C. , Sabir Jamal S. M. , Ideker Trey , Kay Steve A.
Published: November 2011

The circadian clock generates daily rhythms in mammalian liver processes, such as glucose and lipid homeostasis, xenobiotic metabolism, and regeneration. The mechanisms governing these rhythms are not well understood, particularly the distinct contributions of the cell-autonomous clock and central pacemaker to rhythmic liver physiology. Through microarray expression profiling in Met murine hepatocytes (MMH)-D3, we identified over 1,000 transcripts that exhibit circadian oscillations, demonstrating that the cell-autonomous clock can drive many rhythms, and that MMH-D3 is a valid circadian model system. The genes represented by these circadian transcripts displayed both cophasic and antiphasic organization within a protein–protein interaction network, suggesting the existence of competition for binding sites or partners by genes of disparate transcriptional phases. Multiple pathways displayed enrichment in MMH-D3 circadian transcripts, including the polyamine synthesis module of the glutathione metabolic pathway. The polyamine synthesis module, which is highly associated with cell proliferation and whose products are required for initiation of liver regeneration, includes enzymes whose transcripts exhibit circadian oscillations, such as ornithine decarboxylase and spermidine synthase. Metabolic profiling revealed that the enzymatic product of spermidine synthase, spermidine, cycles as well. Thus, the cell-autonomous hepatocyte clock can drive a significant amount of transcriptional rhythms and orchestrate physiologically relevant modules such as polyamine synthesis.
Depletion of β-catenin from mature hepatocytes of mice promotes expansion of hepatic progenitor cells and tumor development
Authors: Wang Er-Yea , Yeh Shiou-Hwei , Tsai Ting-Fen , Huang Hsiang-Po , Jeng Yung-Ming , Lin Wei-Hsiang , Chen Wei-Chih , Yeh Kun-Huei , Chen Pei-Jer , Chen Ding-Shinn
Published: November 2011

Depletion of β-catenin impairs regeneration of the rapid turn-over gut epithelial cells, but appears dispensable for that of the slow turn-over mature hepatocytes in mice until 1 y of age. As the life span of mature murine hepatocytes is about 400 d, we studied conditional β-catenin knockout mice (
Alb-Cre
;

Ctnnb1
flx/flx

) until 20 mo of age to determine the function of β-catenin in the postnatal liver. β-catenin was absent from the hepatocytes of β-catenin knockout mice 4 wk after delivery. From 9 mo of age, hepatocytes were gradually replaced by newly formed β-catenin-positive hepatocytes, which constituted about 90% of hepatocytes at 18–20 mo of age. This process was accompanied by active proliferation of bile duct/ductule cells. β-catenin-positive hepatocytes exhibited elevated proliferation activity and expression of progenitor cell markers, but lower albumin and Cre. This might explain their intact β-catenin protein, and suggest their origins from hepatic progenitor cells. Liver tumors arose spontaneously from β-catenin-positive cells, and tumorigenesis was accelerated by hepatitis B X protein. These results indicate β-catenin critical for the regeneration of mature hepatocytes. Failure to regenerate mature hepatocytes results in proliferation of hepatic progenitor cells that are able to maintain liver function but are predisposed to form liver tumors.
Electromyography activities for shoulder muscles over various movements on different torque changes
Authors: Park Siyoung , Nho Hosung , Chang Myoung‐Jei , Kim Jong‐Kyung
Published: November 2011

The aim of the present study was to investigate the patterns of shoulder muscle activation and joint torques during maximal effort eccentric contractions with shoulder extension, abduction, and diagonal movements on the isokinetic device. Participants in this investigation were nine men and four women with no history of shoulder injury or disorders. They all participated in overhead sports at least three days a week, and volunteered to participate in this study for shoulder isokinetic muscle strength testing. They performed eccentric muscle action with shoulder flexion, abduction, and diagonal movements at velocities of 60 rad·s−1 and 180 rad· s−1, which was followed alternately by passive shoulder flexion, abduction and diagonal movement at a velocity of 30 rad· s−1, and total range of motion was standardised to 90°. Electromyography (EMG) and torque values were calculated to every 10°, except for the start and end 5° during each task. During each test, the isokinetic force output and muscle activation were synchronised. EMG data were normalised by percentage of maximum voluntary isometric contraction (%MVIC). EMG signals were recorded by surface EMG from the anterior deltoid (AD), middle deltoid (MD), posterior deltoid (PD), upper trapezius (UT), middle trapezius (MT), and biceps brachii (BB) muscles during this test. All of the muscle patterns were significantly decreased at the last compared with the initial part during eccentric shoulder flexion movement, except for the BB muscle (P < 0.05). AD and BB muscles played a similar role when peak torque was generated under load during eccentric muscle action with varying shoulder movements. PD and UT muscle activities were significantly lower than the other muscle activities during eccentric contraction with shoulder flexion and abduction movements, and the PD and UT muscles played a significant role in conjunction with MD and MT muscles in varying degrees during eccentric contraction with shoulder diagonal movements at 180 rad·s−1 (P < 0.05). Our study demonstrated that MT muscle activity was greatly influenced when torque values showed a peak moment under load during maximum effort, eccentric contraction with shoulder abduction and diagonal movements. However, the MD, PD, UT, and MT muscle activities had no great influence when peak torque was generated under load during eccentric muscle action with shoulder diagonal movement at high velocity. The present study suggested that varying eccentric muscle activity patterns may be needed to investigate proper training and functional contributions of upper extremity muscles to stabilisation of the shoulder joint when peak torque was generated under load.
Quantification of the manifestations of fatigue during treadmill running
Authors: Stirling Lisa M. , Von Tscharner Vinzenz , Fletcher Jared R. , Nigg Benno M.
Published: November 2011

During whole‐body exercise, fatigue is difficult to quantify; however, changes to mechanical, physiological and psychological systems during exercise are associated with the development of fatigue. To quantify fatigue, one must therefore assess changes occurring in these variables. The purpose of this study was to demonstrate a method to assign weightings to selected variables and to combine them into a single value quantifying changes occurring during exercise. Twelve female recreational runners performed one hour of treadmill running, during which heart rate, respiration rate, stride frequency and six selected psychological variables were collected at defined intervals throughout the run. Data were normalised and a principle component analysis was performed. The resulting first eigenvector was termed the “contribution vector” and indicated the weighting of each variable towards the global exercise‐induced changes in the body. The projection of data onto the contribution vector resulted in a value described as the “fatigue index”. An assessment of the generalisation of the method to new data was performed using a leave‐one‐out cross‐validation procedure and indicated that the index is accurate to within 3.01% of the maximum index value measured. The method developed here has the advantage over current methods due to its multifactorial, causal and customisable nature.
Acute effects of whole‐body vibrations on balance, maximal force and perceived exertion: Vertical platform versus oscillating platform
Authors: García‐López David , Garatachea Nuria , Marín Pedro J. , Martín Teresa , Herrero Azael J.
Published: November 2011

To investigate the effects of acute whole body vibration (WBV) intervention on body balance, neuromuscular performance and perceived exertion two types of vibration platforms were compared: vertical platform (VP) and oscillating platform (OP). Forty‐four healthy college students (35 men and nine women) were exposed on different days to two types of WBV platforms (VP and OP). Electromyography activity (EMG) of six muscle groups was recorded while standing in squat position on the vibrating platform during five 1‐min sets. Balance, maximal voluntary isometric contraction (MVIC), and rating of perceived exertion (RPE) were recorded immediately after the WBV exposure. The OP protocol induced a significantly higher change in balance than VP protocol, as shown by variations in displacement area of the centre of pressure (+25.5% versus –5.5% for OP and VP, respectively). Moreover, RPE scores were significantly higher during OP than VP (+13.2%; P<0.05). No changes were observed concerning MVIC. WBV exposure induces changes in static body balance, these changes being larger when the vibratory stimulus is provided by an OP in comparison to a VP. Moreover, the perceptual response is higher with the OP. Aspects related to direction of vibration or amplitude could explain this acute effect.
Effect of creatine plus caffeine supplements on time to exhaustion during an incremental maximum exercise
Authors: Lee Chia Lun , Lin Jung Charng , Cheng Ching Feng
Published: November 2011

This study investigated the effects of acute caffeine ingestion following short‐term creatine supplementation on an incremental cycling to exhaustion task. Twelve active males performed the task under three conditions: baseline condition (BASE, no ergogenic aid), creatine plus caffeine condition (CRE + CAF), and creatine with placebo condition (CRE + PLA). Following the establishment of BASE condition, participants were administered CRE + CAF (0.3 g·kg−1·day−1 of creatine for 5 days followed by 6 mg·kg−1 of caffeine 1 h prior to testing) and CRE + PLA (0.3 g·kg−1·day−1 of creatine for 5 days followed by 6 mg·kg−1 of placebo 1 h prior to testing) in a double‐blind, randomized crossover and counterbalancing protocol. No significant differences were observed in relative maximal oxygen consumption ([Vdot]O2max) (51.7±5.5, 52.8±4.9 and 51.3±5.6 ml·kg−1·min−1 for BASE, CRE + CAF and CRE + PLA, respectively; P>0.05) and absolute [Vdot]O2max (3.6±0.4, 3.7±0.4 and 3.5±0.5 l·min−1 for BASE, CRE + CAF and CRE + PLA, respectively; P>0.05). Blood samples indicated significantly higher blood lactate and glucose concentrations in the CRE + CAF among those in the BASE or CRE + PLA condition during the test (P<0.05). The time to exhaustion on a cycling ergometer was significantly longer for CRE + CAF (1087.2±123.9 s) compared with BASE (1009.2±86.0 s) or CRE + PLA (1040.3±96.1 s). This study indicated that a single dose of caffeine following short‐term creatine supplementation did not hinder the creatine–caffeine interaction. In fact, it lengthened the time to exhaustion during an incremental maximum exercise test. However, this regime might lead to the accumulation of lactate in the blood.