bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigating thermal stability of structural defects and its effect on d ferromagnetism in undoped SnO2
Authors: Kamble Vinayak B. , Bhat S. V. , Umarji A. M.
Published: June 2013

The effect of annealing on structural defects and d0 ferromagnetism in SnO2 nanoparticles prepared by solution combustion method is investigated. The as-synthesized SnO2 nanoparticles were annealed at 400–800 °C for 2 h, in ambient conditions. The crystallinity, size, and morphology of the samples were studied using x-ray diffraction and transmission electron microscopy studies. The annealing results in grain growth due to coarsening as well as reduction in oxygen vacancies as confirmed by Raman spectroscopy, photoluminescence spectroscopy, and x-ray photoelectron spectroscopy. All the as synthesized and annealed samples exhibit room temperature ferromagnetism (RTFM) with distinct hysteresis loops and the saturation magnetization as high as ∼0.02 emu/g in as-synthesized samples. However, the saturation magnetization is drastically reduced with increasing annealing temperature. Further the presence of singly charged oxygen vacancies (Vo− signal at g-value 1.99) is confirmed by electron paramagnetic resonance studies, which also diminish with increasing annealing temperature. The observed diminishing RTFM and simultaneous evidences of diminishing O vacancies clearly indicate that RTFM is driven by defects in oxide lattice and confirms primary role of oxygen vacancies in inducing ferromagnetic ordering in metal oxide semiconductors. The study also provides improved fundamental understanding regarding the ambiguity in the origin of intrinsic RTFM in semiconducting metal oxides and projects their technological application in the field of spintronics.
Granular shear flows of flat disks and elongated rods without and with friction
Authors: Guo Y. , Wassgren C. , Hancock B. , Ketterhagen W. , Curtis J.
Published: June 2013

Granular shear flows of flat disks and elongated rods are simulated using the Discrete Element Method. The effects of particle shape, interparticle friction, coefficient of restitution, and Young's modulus on the flow behavior and solid phase stresses have been investigated. Without friction, the stresses decrease as the particles become flatter or more elongated due to the effect of particle shape on the motion and interaction of particles. In dense flows, the particles tend to have their largest dimension aligned in the flow direction and their smallest dimension aligned in the velocity gradient direction, such that the contacts between the particles are reduced. The particle alignment is more significant for flatter disks and more elongated rods. The interparticle friction has a crucial impact on the flow pattern, particle alignment, and stress. Unlike in the smooth layer flows with frictionless particles, frictional particles are entangled into large masses which rotate like solid bodies under shear. In dense flows with friction, a sharp stress increase is observed with a small increase in the solid volume fraction, and a space-spanning network of force chains is rapidly formed with the increase in stress. The stress surge can occur at a lower solid volume fraction for the flatter and more elongated particles. The particle Young's modulus has a negligible effect on dilute and moderately dense flows. However, in dense flows where the space-spanning network of force chains is formed, the stress depends strongly on the particle Young's modulus. In shear flows of non-spherical particles, the stress tensor is found to be symmetric, but anisotropic with the normal component in the flow direction greater than the other two normal components. The granular temperature for the non-spherical particle systems consists of translational and rotational temperatures. The translational temperature is not equally partitioned in the three directions with the component in the flow direction greater than the other two. The rotational temperature is less than the translational temperature at low solid volume fractions, but may become greater than the translational temperature at high solid volume fractions.
The generation of random variates from a relativistic Maxwellian distribution
Authors: Swisdak M.
Published: June 2013

A procedure for generating random variates from a relativistic Maxwellian distribution with arbitrary temperature and drift velocity is presented. The algorithm is based on the rejection method and can be used to initialize particle velocities in kinetic simulations of plasmas and gases.
Experimental investigation of density behaviors in front of the lower hybrid launcher in experimental advanced superconducting tokamak
Authors: Zhang L. , Ding B. J. , Li M. H. , Kong E. H. , Wei W. , Liu F. K. , Shan J. F. , Wu Z. G. , Zhu L. , Ma W. D. , Tong Y. Y. , Li Y. C. , Wang M. , Zhao L. M. , Hu H. C. , Liu L. ,   EAST Team
Published: June 2013

A triple Langmuir probe is mounted on the top of the Lower Hybrid (LH) antenna to measure the electron density near the LH grills in Experimental Advanced Superconducting Tokamak. In this work, the LH power density ranges from 2.3 MWm−2 to 10.3 MWm−2 and the rate of puffing gas varies from 1.7 × 1020 el/s to 14 × 1020 el/s. The relation between the edge density (from 0.3 × ne_cutoff to 20 × ne_cutoff, where ne_cutoff is the cutoff density, ne_cutoff = 0.74 × 1017 m−3 for 2.45 GHz lower hybrid current drive) near the LH grill and the LH power reflection coefficients is investigated. The factors, including the gap between the LH grills and the last closed magnetic flux surface, line-averaged density, LH power, edge safety factor, and gas puffing, are analyzed. The experiments show that injection of LH power is beneficial for increasing edge density. Gas puffing is beneficial for increasing grill density but excess gas puffing is unfavorable for coupling and current drive.
Shape designing for light extraction enhancement bulk-GaN light-emitting diodes
Authors: Sun Bo , Zhao Lixia , Wei Tongbo , Yi Xiaoyan , Liu Zhiqiang , Wang Guohong , Li Jinmin
Published: June 2013

Light extraction efficiency enhancement of bulk GaN light-emitting diodes (LEDs) in the shape of truncated-pyramid has been investigated. Compared with the reference LEDs, an enhancement of up to 46% on the light output power from rectangle-shaped LEDs chip with the inclination angle (∼44°) has been observed. Compared with the common triangle-shaped and hexagon-shaped LEDs, large size of conventional rectangular LEDs shaped with truncated-pyramid shows more obvious enhancement in light extraction efficiency. In addition, the ray-tracing simulations results show that light extraction efficiency was influenced not only by inclination angle but also by dimension size.
Double injection in graphene p-i-n structures
Authors: Ryzhii V. , Semenikhin I. , Ryzhii M. , Svintsov D. , Vyurkov V. , Satou A. , Otsuji T.
Published: June 2013

We study the processes of the electron and hole injection (double injection) into the i-region of graphene-layer and multiple graphene-layer p-i-n structures at the forward bias voltages. The hydrodynamic equations governing the electron and hole transport in graphene coupled with the two-dimensional Poisson equation are employed. Using analytical and numerical solutions of the equations of the model, we calculate the band edge profile, the spatial distributions of the quasi-Fermi energies, carrier density and velocity, and the current-voltage characteristics. In particular, we demonstrated that the electron and hole collisions can strongly affect these distributions. The obtained results can be used for the realization and optimization of graphene-based injection terahertz and infrared lasers.
From nanographene to monolayer graphene on 6H-SiC(0001) substrate
Authors: Ouerghi A. , Ridene M. , Mathieu C. , Gogneau N. , Belkhou R.
Published: June 2013

Graphene quantum dots, nanoribbons, and nanographene are great promising in various applications owing to the quantum confinement and edge effects. Here we evidence the presence of epitaxial nanographene on SiC. Morphology and electronic structure of the graphene layers have been analyzed by SPELEEM. Using Scanning Tunneling Microscopy, we show that the increase of relative number of clusters carbon enabled the observation of nanographene, the diameter of which was around 20 nm. This nanographene shows a honeycomb structure at atomic level. The local chemical and electronic properties of the sample have been determined by photoelectron spectroscopy using synchrotron radiation.
Investigating the contribution of superdiffusive transport to ultrafast demagnetization of ferromagnetic thin films
Authors: Schellekens A. J. , Verhoeven W. , Vader T. N. , Koopmans B.
Published: June 2013

We experimentally investigate to what extent superdiffusive spin transport contributes to the ultrafast demagnetization of ferromagnets by pumping Ni thin films from the front side and back side of the sample. Within the experimental accuracy, the temporal evolution of the magnetization for front-side and back-side pumping is identical, hence no influence of transport was detected. Furthermore, adding a conducting buffer layer to enhance spin transport does not alter the magnetization dynamics significantly either. In order to explain the experimental results, angular momentum has to be locally dissipated on femtosecond timescales, supporting heating of the spin system as the main driving force for ultrafast demagnetization in the investigated ferromagnetic films.
Electron spin dynamics and g-factor in GaAsBi
Authors: Mazzucato S. , Zhang T. T. , Carrère H. , Lagarde D. , Boonpeng P. , Arnoult A. , Lacoste G. , Balocchi A. , Amand T. , Fontaine C. , Marie X.
Published: June 2013

Electron spin dynamics in elastically strained bulk GaAsBi epilayer with 2.2% Bi concentration has been measured by time resolved photoluminescence spectroscopy. Under external transverse magnetic field, the measurement of the photoluminescence polarization oscillations resulting from the Larmor precession of electron spins yields an accurate determination of the Landé g-factor. We find that the value of g increases from −0.81 to −0.68 when the temperature rises from T = 100 K to T = 300 K. This is typically double the value of GaAs, in agreement with the larger spin-orbit interaction in GaAsBi. In this temperature range, the electron spin lifetime decreases from 370 to 100 ps.
Vertically aligned rolled-up SiO2 optical microcavities in add-drop configuration
Authors: Böttner Stefan , Li Shilong , Jorgensen Matthew R. , Schmidt Oliver G.
Published: June 2013

A significant step towards integrated vertically rolled-up microcavities is demonstrated by interfacing an as-fabricated SiO2 microtube optical ring resonator with tapered fibers. In this transmission configuration, resonant filtering of optical signals at telecommunication wavelengths is shown in subwavelength thick walled microcavities. Moreover, we present a four-port add-drop filter based on a lifted doubly interfaced vertically rolled-up microcavity. Our work opens opportunities for vertical resonant light transfer in 3D multi-level optical data processing as well as for massively parallel optofluidic analysis of biomaterials in lab-on-a-chip systems.
Dependence of the microwave surface resistance of superconducting niobium on the magnitude of the rf field
Authors: Romanenko A. , Grassellino A.
Published: June 2013

Utilizing difference in temperature dependencies we decoupled Bardeen-Cooper-Schrieffer (BCS) and residual components of the microwave surface resistance of superconducting niobium at all rf fields up to Brf∼115 mT. We reveal that the residual resistance decreases with field at Brf≲ 40 mT and strongly increases in chemically treated niobium at Brf>80 mT. We find that BCS surface resistance is weakly dependent on field in the clean limit, whereas a strong and peculiar field dependence emerges after 120 °C vacuum baking.
Tracking emission rate dynamics of nitrogen vacancy centers in nanodiamonds
Authors: Inam F. A. , Edmonds A. M. , Steel M. J. , Castelletto S.
Published: June 2013

Spontaneous emission from crystal centers is influenced by both the photonic local density of states and non-radiative processes. Here, we monitor the spontaneous emission of single nitrogen vacancy (NV) centers as their host diamond is reduced in size from a large monolithic crystal to a nanocrystal by successive cycles of oxidation. The size reduction induces a quenching of the NV radiative emission. Additional non-radiative channels lead to a decrease of the fluorescence intensity and the excited state lifetime. In one case, we observe the onset of blinking which may provide a route to understand these additional non-radiative decay channels.
Hydrogen ions produced by plasma-assisted catalytic ionization using nickel grid
Authors: Oohara W. , Kawata K. , Hibino T.
Published: June 2013

Positive and negative hydrogen ions are produced by plasma-assisted catalytic ionization using a nickel grid, where the irradiation current density of positive ions onto the grid can be controlled by the discharge power. The irradiation energy can be controlled by both the grid potential and the discharge plasma potential. Extraction properties and energy distributions of positive and negative ions produced in the cases of using the grid and a porous nickel plate are compared. Two production mechanisms of negative ions are found in the process of plasma-assisted catalytic ionization.
A thermodynamic potential for Ni45Co5Mn36.7In13.3 single crystal
Authors: Wang J. J. , Ma X. Q. , Huang H. B. , He W. Q. , Liu Z. H. , Chen Long-Qing
Published: July 2013

A thermodynamic potential as a function of the ferromagnetic, antiferromagnetic, and martensite order parameters is developed using existing experimental data. It successfully reproduces the single domain properties of Ni45Co5Mn36.7In13.3 bulk crystal, including the Curie temperature, the transition temperature from ferromagnetic austenite phase to antiferromagnetic martensite phase as well as its response to an externally applied magnetic field, the saturated magnetization, the martensite strain, the entropy change, and the magnetic permeability. It can be applied to explore the stress-strain and magnetic field-strain behaviors and implemented in phase field simulations to study the ferromagnetic, antiferromagnetic, and martensite domain stability and evolution.
Effect of the magnetic film thickness on the enhancement of the spin current by multi-magnon processes
Authors: Dzyapko O. , Kurebayashi H. , Demidov V. E. , Evelt M. , Ferguson A. J. , Demokritov S. O.
Published: June 2013

We study experimentally the spin-current generation in yttrium iron garnet (YIG)/Pt bilayers based on YIG films with different thicknesses. Our results show that for all films with thicknesses exceeding a certain value, the spin current in the YIG/Pt system is enhanced at low frequencies. The cut-off frequencies, at which the enhancement starts, as well as the efficiency of the enhancement were found to increase with increasing film thickness. Good correlation between the cut-off frequency and the frequency at which the three-magnon splitting becomes allowed was observed. These findings prove that the latter process is responsible for the spin-current enhancement.
Plasmon hybridization in graphene metamaterials
Authors: Ishikawa Atsushi , Tanaka Takuo
Published: June 2013

Plasmon hybridization in a stacked pair of graphene ribbons is investigated at terahertz frequencies. We fabricated and characterized an array of graphene ribbons on a heavily-doped Si substrate with a SiO2 gap layer in between. The interaction between graphene plasmons and their mirror images in the substrate forms a coupled system, mimicking a graphene ribbon pair, thereby dramatically modifies the mode profiles and resultant spectral responses. Magnetic plasmon resonances arising from the plasmon hybridization are demonstrated at terahertz frequencies. The corresponding numerical simulations reveal the important resonant behavior of structured graphene and their hybridized systems.
Electro-photo double modulation on the resistive switching behavior and switchable photoelectric effect in BiFeO3 films
Authors: Wang Le , Jin Kui-juan , Ge Chen , Wang Can , Guo Hai-zhong , Lu Hui-bin , Yang Guo-zhen
Published: June 2013

We present an electro-photo double modulation on the resistive switching behavior in an Au/BiFeO3/La0.7Sr0.3MnO3/SrTiO3 heterostructure, combining the electro-resistance effect and the photo-resistance effect. The pulse voltages can lead to nonvolatile resistance variations in this heterostructure, and the laser illumination can also modulate the high and low resistance states. Consequently, four stable resistance states are achieved. Furthermore, a switchable photoelectric effect-the direction of the photocurrent can be switched by polarization reversal, is also observed in this heterostructure. The present results should have potential applications to develop multi-state memory devices based on perovskite oxides.
Electrical conduction channel along the grain boundaries of Cu(In,Ga)Se2 thin films
Authors: Jiang C.-S. , Repins I. L. , Mansfield L. M. , Contreras M. A. , Moutinho H. R. , Ramanathan K. , Noufi R. , Al-Jassim M. M.
Published: June 2013

We report on a direct nm-resolution resistance mapping on the Cu(In,Ga)Se2 photovoltaic thin films, using scanning spreading resistance microcopy. We found a conductance channel along the grain boundaries (GBs) of the polycrystalline materials, which is consistent with the argument that carrier polarity of the GB and the space charge region around it is inverted. To minimize the probe/film contact resistance, so that the local spreading resistance beneath the probe is measured, the probe must be adequately indented to the film and a bias voltage larger than the onset value of the probe/film barrier should be applied.
Optical properties of AlAsxSb1−x alloys determined by in situ ellipsometry
Authors: Kim J. Y. , Yoon J. J. , Kim T. J. , Kim Y. D. , Lee E. H. , Bae M. H. , Song J. D. , Choi W. J. , Liang C.-T. , Chang Y.-C.
Published: July 2013

We report pseudodielectric function data  ⟨ε⟩ = ⟨ε1⟩ + i⟨ε2⟩ from 0.74 to 6.48 eV of oxide-free AlAsSb alloys that are the closest representation to date of the intrinsic bulk dielectric response ε of the material. Measurements were performed on 1.3 μm thick films grown on (001) GaAs substrates by molecular beam epitaxy. Data were obtained with the films in situ to avoid oxidation artifacts. Critical-point structures were identified by band-structure calculations done with the linear augmented Slater-type orbital method. Crossings of transitions at the Γ- and X-points and the Γ- and L-points with composition were observed.
Influence of Ag on the microstructure and magnetic properties of perpendicular exchange coupled composite L1-[FePt-Ag]/[Co/Ni]N films
Authors: Guo H. H. , Chu H. G. , Ma B. , Zhang Z. Z. , Jin Q. Y. , Wang H. , Wang J. P.
Published: June 2013

Two series of exchange coupled composite films with and without Ag interlayer, L10-[FePt-Ag]/[Co/Ni]N (FC-Ag-N) and FePt/[Co/Ni]N (FC-N), were prepared and well studied. Coercivities of both series decrease with the increase of the soft [Co/Ni]N thickness. However, well-isolated sphere grains are observed in FC-Ag-N samples, instead of a ledge-type structure in FC-N samples. The average grain size is almost constant for FC-Ag-N films, regardless of the thickness of Co/Ni multilayer. It indicates that Ag effectively suppresses the grain coarseness during the deposition of [Co/Ni]N.
Toward high efficiency of inverted organic solar cells: Concurrent improvement in optical and electrical properties of electron transport layers
Authors: Tsai S. H. , Ho S. T. , Jhuo H. J. , Ho C. R. , Chen S. A. , He Jr-Hau
Published: June 2013

The conversion efficiency (η) of organic solar cells (OSCs) constructed with ITO/ZnO/P3HT:PCBM/PEDOT:PSS/Ag is improved by incorporating Al into ZnO films (AZO) as electron transport layers (ETLs). Compared with ZnO films, AZO-based OSCs enhance η by ∼13.9% via improving short-circuit photocurrent density from 10.73 to 11.12 mA cm−2 and fill factor from 53.7% to 60.8%. Doping Al into ZnO ETLs not only optimizes band alignment between organic active layers and ETLs and increases carrier concentration, conductivity, and bandgap of ZnO films facilitating more light into OSCs but also improves the absorption of P3HT by promoting the molecular ordering of P3HT.
Changes to sexual and intimate relationships in the postnatal period: women’s experiences with health professionals
Authors: Woolhouse Hannah , McDonald Ellie , Brown Stephanie J.
Published: July 2013

Women navigate many social changes when they become a mother, often including considerable changes to intimate and sexual relationships. This paper draws on data collected in an Australian multicentre prospective nulliparous pregnancy cohort study and a nested qualitative substudy exploring women’s experiences of sex and intimacy after the birth of their first child. In all, 1507 women were recruited in early pregnancy (mean gestation 15 weeks) and completed self-administered questionnaires at 3, 6 and 12 months and 4.5 years postpartum. Eighteen participants were interviewed 2.5–3.5 years after the birth of their first child regarding sex and intimacy after having a baby. Interviews were transcribed verbatim and analysed using interpretive phenomenological analysis. Cohort data reveal a considerable drop in both emotional satisfaction and physical pleasure in intimate relationships after birth, with emotional satisfaction continuing to fall up until 4.5 years postpartum. Less than one-quarter of participants reported that their general practitioner had asked directly about sexual health or relationship problems in the first 3 months postpartum (23% and 18%, respectively). In contrast, 13% of women reported that a maternal and child health nurse had asked directly about sexual problems since the birth, and 31% had asked directly about relationship problems. In-depth interviews revealed that relationships with intimate partners were important issues for women following childbirth, and women were seeking reassurance from health professionals that their changing experiences of sex and intimacy after childbirth were ‘normal’. Some women felt they had ‘fallen through the gaps’ and there was not an opportunity provided by health professionals for them to discuss changes affecting their sexual and intimate relationships. The findings suggest that intimate relationships are significantly strained in the years following childbirth and women want more information from primary health care professionals regarding changes to intimate and sexual relationships after childbirth.
Foraging ecology of the night-active bull ant Myrmecia pyriformis
Authors: Reid Samuel F. , Narendra Ajay , Taylor Robert W. , Zeil Jochen
Published: July 2013

Here we report on the nocturnal bull ant Myrmecia pyriformis, a species whose activity to and from the nest is mainly restricted to the dawn and dusk twilight respectively. Recent research on M. pyriformis has focussed on its visual system, the timing of activity patterns, and the navigational strategies employed by individuals while foraging. There is, however, a lack of basic ecological information about this species. The present study describes the behaviour and foraging ecology of wild populations of M. pyriformis. We find that most foragers make only one foraging journey per night, leaving the nest at dusk twilight and returning during dawn twilight. Individuals who make multiple trips typically return with prey. We provide evidence that foragers imbibe liquid food while abroad and likely share these resources via trophallaxis once within the nest. Activity during the night varies with moon illumination, and we postulate that this is due to changes in light levels, which influence navigation to and from the nest. This hypothesis is supported by observations of activity during overcast conditions. Finally, we also describe some aspects of colony founding, colony demise and the behaviour of reproductive individuals during the mating season.
CYP76AH1 catalyzes turnover of miltiradiene in tanshinones biosynthesis and enables heterologous production of ferruginol in yeasts
Authors: Guo Juan , Zhou Yongjin J. , Hillwig Matthew L. , Shen Ye , Yang Lei , Wang Yajun , Zhang Xianan , Liu Wujun , Peters Reuben J. , Chen Xiaoya , Zhao Zongbao K. , Huang Luqi
Published: June 2013

Cytochrome P450 enzymes (CYPs) play major roles in generating highly functionalized terpenoids, but identifying the exact biotransformation step(s) catalyzed by plant CYP in terpenoid biosynthesis is extremely challenging. Tanshinones are abietane-type norditerpenoid naphthoquinones that are the main lipophilic bioactive components of the Chinese medicinal herb danshen (
Salvia miltiorrhiza
). Whereas the diterpene synthases responsible for the conversion of (
E,E,E
)-geranylgeranyl diphosphate into the abietane miltiradiene, a potential precursor to tanshinones, have been recently described, molecular characterization of further transformation of miltiradiene remains unavailable. Here we report stable-isotope labeling results that demonstrate the intermediacy of miltiradiene in tanshinone biosynthesis. We further use a next-generation sequencing approach to identify six candidate CYP genes being coregulated with the diterpene synthase genes in both the rhizome and danshen hairy roots, and demonstrate that one of these, CYP76AH1, catalyzes a unique four-electron oxidation cascade on miltiradiene to produce ferruginol both in vitro and in vivo. We then build upon the previous establishment of miltiradiene production in
Saccharomyces cerevisiae
, with incorporation of CYP76AH1 and phyto-CYP reductase genes leading to heterologous production of ferruginol at 10.5 mg/L. As ferruginol has been found in many plants including danshen, the results and the approaches that were described here provide a solid foundation to further elucidate the biosynthesis of tanshinones and related diterpenoids. Moreover, these results should facilitate the construction of microbial cell factories for the production of phytoterpenoids.
RETRACTED: Signaling through hepatocellular A2B adenosine receptors dampens ischemia and reperfusion injury of the liver
Authors: Zimmerman Michael A. , Grenz Almut , Tak Eunyoung , Kaplan Maria , Ridyard Douglas , Brodsky Kelley S. , Mandell Mercedes Susan , Kam Igal , Eltzschig Holger K.
Published: June 2013

Ischemia and reperfusion significantly contributes to the morbidity and mortality of liver surgery and transplantation. Based on studies showing a critical role for adenosine signaling in mediating tissue adaptation during hypoxia, we hypothesized that signaling events through adenosine receptors (ADORA1, ADORA2A, ADORA2B, or ADORA3) attenuates hepatic ischemia and reperfusion injury. Initial screening studies of human liver biopsies obtained during hepatic transplantation demonstrated a selective and robust induction of ADORA2B transcript and protein following ischemia and reperfusion. Subsequent exposure of gene-targeted mice for each individual adenosine receptor to liver ischemia and reperfusion revealed a selective role for the Adora2b in liver protection. Moreover, treatment of wild-type mice with an Adora2b-selective antagonist resulted in enhanced liver injury, whereas Adora2b-agonist treatment was associated with attenuated hepatic injury in wild-type, but not in
Adora2b

−/−

mice. Subsequent studies in mice with
Adora2b
deletion in different tissues—including vascular endothelia, myeloid cells, and hepatocytes—revealed a surprising role for hepatocellular-specific Adora2b signaling in attenuating nuclear factor NF-κB activation and thereby mediating liver protection from ischemia and reperfusion injury. These studies provide a unique role for hepatocellular-specific Adora2b signaling in liver protection during ischemia and reperfusion injury.
Aneuploidy underlies a multicellular phenotypic switch
Authors: Tan Zhihao , Hays Michelle , Cromie Gareth A. , Jeffery Eric W. , Scott Adrian C. , Ahyong Vida , Sirr Amy , Skupin Alexander , Dudley Aimée M.
Published: June 2013

Although microorganisms are traditionally used to investigate unicellular processes, the yeast
Saccharomyces cerevisiae
has the ability to form colonies with highly complex, multicellular structures. Colonies with the “fluffy” morphology have properties reminiscent of bacterial biofilms and are easily distinguished from the “smooth” colonies typically formed by laboratory strains. We have identified strains that are able to reversibly toggle between the fluffy and smooth colony-forming states. Using a combination of flow cytometry and high-throughput restriction-site associated DNA tag sequencing, we show that this switch is correlated with a change in chromosomal copy number. Furthermore, the gain of a single chromosome is sufficient to switch a strain from the fluffy to the smooth state, and its subsequent loss to revert the strain back to the fluffy state. Because copy number imbalance of six of the 16
S. cerevisiae
chromosomes and even a single gene can modulate the switch, our results support the hypothesis that the state switch is produced by dosage-sensitive genes, rather than a general response to altered DNA content. These findings add a complex, multicellular phenotype to the list of molecular and cellular traits known to be altered by aneuploidy and suggest that chromosome missegregation can provide a quick, heritable, and reversible mechanism by which organisms can toggle between phenotypes.
RNA splicing regulates the temporal order of TNF-induced gene expression
Authors: Hao Shengli , Baltimore David
Published: June 2013

When cells are induced to express inflammatory genes by treatment with TNF, the mRNAs for the induced genes appear in three distinct waves, defining gene groups I, II, and III, or early, intermediate, and late genes. To examine the basis for these different kinetic classes, we have developed a PCR-based procedure to distinguish pre-mRNAs from mRNAs. It shows that the three groups initiate transcription virtually simultaneously but that delays in splicing characterize groups II and III. We also examined the elongation times, concluding that pre-mRNA synthesis is coordinate but splicing differences directly regulate the timing of mRNA production.
Axon position within the corpus callosum determines contralateral cortical projection
Authors: Zhou Jing , Wen Yunqing , She Liang , Sui Ya-nan , Liu Lu , Richards Linda J. , Poo Mu-ming
Published: June 2013

Significance

Two hemispheres of the neocortex are connected via a large axon bundle, the corpus callosum (CC). Axons from one side of the cortex project primarily to the equivalent cortical area on the contralateral side. How this homotopic axon projection is achieved during development remains unclear. Quantitative analysis of the cortical axons' positions within CC and their projection pattern after crossing the midline showed that axon position within CC is critical for homotopic projection. Further genetic perturbations of semaphorin/neuropilin-1 signaling disrupted the axon order in CC, resulting in an ectopic contralateral axon projection that could not be corrected by developmental refinement.
Parametrizing the exoplanet eccentricity distribution with the Beta distribution
Authors: Kipping David M.
Published: June 2013

It is suggested that the distribution of orbital eccentricities for extrasolar planets is well described by the Beta distribution. Several properties of the Beta distribution make it a powerful tool for this purpose. For example, the Beta distribution can reproduce a diverse range of probability density functions (PDFs) using just two shape parameters (a and b). We argue that this makes it ideal for serving as a parametric model in Bayesian comparative population analysis. The Beta distribution is also uniquely defined over the interval zero to unity, meaning that it can serve as a proper prior for eccentricity when analysing the observations of bound extrasolar planets. Using nested sampling, we find that the distribution of eccentricities for 396 exoplanets detected through radial velocity with high signal-to-noise is well described by a Beta distribution with parameters a = 0.867${^{+ 0.044}_{- 0.044}}$ and b = 3.03${^{+ 0.17}_{- 0.16}}$. The Beta distribution is shown to be 3.7 times more likely to represent the underlying distribution of exoplanet eccentricities than the next best model: a Rayleigh + exponential distribution. The same data are also used in an example population comparison utilizing the Beta distribution, where we find that the short- and long-period planets are described by distinct Beta distributions at a confidence of 11.6σ and display a signature consistent with the effects of tidal circularization.
Jeans instability criterion modified by external tidal field
Authors: Jog Chanda J.
Published: June 2013

The well-known Jeans criterion describes the onset of instabilities in an infinite, homogeneous, self-gravitating medium supported by pressure. Most realistic astrophysical systems, however, are not isolated – instead they are under the influence of an external field such as the tidal field due to a neighbour. Here, we do a linear perturbation analysis for a system in an external field and obtain a generalized dispersion relation that depends on the wavenumber, the sound speed and also the magnitude of the tidal field. A typical, disruptive tidal field is shown to make the system more stable against perturbations, and results in a higher effective Jeans wavelength. The minimum mass that can become unstable is then higher (super-Jeans) than the usual Jeans mass. Conversely, in a compressive tidal field, perturbations can grow even when the mass is lower (sub-Jeans). This approach involving the inclusion of tidal field opens up a new way of looking at instabilities in gravitating systems. The treatment is general and the simple analytical form of the modified Jeans criterion obtained makes it easily accessible.
Differential regulation of AMPK activation in leptin‐and creatine‐deficient mice
Authors: Stockebrand Malte , Sauter Kathrin , Neu Axel , Isbrandt Dirk , Choe Chi‐un
Published: June 2013

AMP‐activated protein kinase (AMPK) is a key sensor and regulator of energy homeostasis. Previously, we demonstrated that intracellular energy depletion by L‐arginine:glycine amidinotransferase (AGAT) deficiency resulted in AMPK activation and protected from metabolic syndrome. In the present study, we show tissue‐specific leptin dependence of AMPK activation by energy depletion. We investigated leptin‐dependent AMPK regulation in AGAT‐ and leptin‐deficient (d/d ob/ob) mice. Like ob/ob mice, but unlike d/d mice, d/d ob/ob mice were obese and glucose intolerant. Therefore, leptin is a prerequisite for resistance to metabolic syndrome in AGAT‐deficient mice. Quantitative Western blots revealed a 4‐fold increase in AMPK activation in skeletal muscle of d/d ob/ob mice (P<0.001). However, AMPK activation was absent in white adipose tissue (WAT) and liver. Compared with blood glucose levels in ob/ob mice, fasting levels were still reduced and therefore did not show leptin dependence (wild‐type, 79.4±3.9 mg/dl; d/d, 68.4±3.2 mg/dl; P<0.05). In ob/ob mice and wild‐type mice, 5‐aminoimidazole‐4‐carboxamide‐1‐β‐d‐ribofuranoside (AICAR), in combination with leptin, augmented glucose tolerance compared with AICAR alone, whereas no improvement was found under conditions of high‐fatdiet feeding. These findings reveal a previously unknown synergistic AMPK activation by leptin and intracellular energy depletion, suggesting that AMPK activation can be therapeutically effective in metabolic syndrome only if leptin sensitivity is preserved.—Stockebrand, M., Sauter, K., Neu, A., Isbrandt, D., Choe, C., Differential regulation of AMPK activation in leptin‐ and creatine‐deficient mice. FASEBJ. 27, 4147‐4156 (2013). www.fasebj.org
Neurotrophic factor expression in expandable cell populations from brain samples in living patients with Parkinson's disease
Authors: Xu Hu , Belkacemi Louiza , Jog Mandar , Parrent Andrew , Hebb Matthew O.
Published: June 2013

Cell‐based therapies offer promise for patients with Parkinson's disease (PD); however, durable and effective transplantation substrates need to be defined. This study characterized the feasibility and growth properties of primary cultures established from small‐volume brain biopsies taken during deep brain stimulation (DBS) surgery in patients with PD. The lineage and expression of neurotrophic factors with known beneficial actions in PD‐affected brain circuitry were also evaluated. Nineteen patients with PD undergoing DBS surgery consented to brain biopsies prior to electrode implantation. Cultures from these samples exhibited exponential and plateau phases of growth and were readily expanded throughout multiple passages. There was robust expression of progenitor markers and the unexpected colocalization of neural and mesenchymal proteins. The oligodendrocyte transcription factor, Olig1, and the myelin‐specific sphingolipid, galactocerebroside, were coexpressed with each of glial‐derived neurotrophic factor, brain‐derived neurotrophic factor, and cerebral dopamine neurotrophic factor. Fluorescence‐activated cell sorting demonstrated homogeneous expression of both nestin and Olig1 throughout the expanded cultures. Cells remained viable after a year in cryostorage. These findings confirm the feasibility of small brain biopsies as an expandable source of autologous cell substrate in living patients and demonstrate the complex phenotype of these cells, with implications for therapeutic application in PD and other neurological diseases.— Xu, H., Belkacemi, L., Jog, M., Parrent, A., Hebb. M. O. Neurotrophic factor expression in expandable cell populations from brain samples in living patients with Parkinson's disease. FASEBJ. 27, 4157‐4168 (2013). www.fasebj.org
Coxsackievirus B3 modulates cardiac ion channels
Authors: Steinke Katja , Sachse Frank , Ettischer Nicole , Strutz‐Seebohm Nathalie , Henrion Ulrike , Rohrbeck Matthias , Klosowski Rafael , Wolters Dirk , Brunner Stefan , Franz Wolfgang‐Michael , Pott Lutz , Munoz Carlos , Kandolf Reinhard , Schulze‐Bahr Eric , Lang Florian , Klingel Karin , Seebohm Guiscard
Published: June 2013

Infections with coxsackieviruses of type B (CVBs), which are known to induce severe forms of acute and chronic myocarditis, are often accompanied by ventricular arrhythmias and sudden cardiac death. The mechanisms underlying the development of virus‐induced, life‐threatening arrhythmias, which are pheno‐typically similar to those observed in patients having functionally impaired cardiac ion channels, remain, however, enigmatic. In the present study, we show, for the first time, modulating time‐dependent effects of CVB3 on the cardiac ion channels KCNQ1, hERG1, and Cav1.2 in heterologous expression. Channel protein abundance in cellular plasma membrane and patterns of their subcellular distribution were altered in infected murine hearts. The antiviral compound AG7088 did not prevent these effects on channels. In silico analyses of infected human myocytes suggest pronounced alterations of electrical and calcium signaling and increased risk of arrhythmogenesis. These modifications are attenuated by the common Asian polymorphism KCNQ1 P448R, a genetic determinant preventing coxsackievirus‐induced effects in vitro. This study provides a previously unknown explanation for the development of arrhythmias in enteroviral myocarditis, which will help to develop therapeutic strategies for arrhythmia treatment.—Steinke, K., Sachse, F., Ettischer, N., Strutz‐Seebohm, N., Henrion, U., Rohrbeck, M., Klosowski, R., Wolters, D., Brunner, S., Franz, W.‐M., Pott, L., Munoz, C., Kandolf, R., SchulzeBahr, E., Lang, F., Klingel, K., Seebohm, G., Coxsackievirus B3 modulates cardiac ion channels. FASEB J. 27, 4108–4121 (2013). www.fasebj.org
Exchange protein activated by cAMP 1 (Epac1)‐deficient mice develop β‐cell dysfunction and metabolic syndrome
Authors: Kai Alan K. L. , Lam Amy K. M. , Chen Yingxian , Tai Andrew C. P. , Zhang Xinmei , Lai Angela K. W. , Yeung Patrick K. K. , Tam Sidney , Wang Jian , Lam Karen S. , Vanhoutte Paul M. , Bos Johannes L. , Chung Stephen S. M. , Xu Aimin , Chung Sookja K.
Published: June 2013

Previously, exchange protein directly activated by cAMP 2 (Epac2) and PKA were known to play a role in glucose‐stimulated insulin secretion (GSIS) by pancreatic β cells. The present study shows that Epac1 mRNA is also expressed by β cells. Therefore, we generated mice and embryonic stem (ES) cells with deletion of the Epac1 gene to define its role in β‐cell biology and metabolism. The homozygous Epac1‐ knockout (Epac1–/–) mice developed impaired glucose tolerance and GSIS with deranged islet cytoarchitecture, which was confirmed by isolated islets from adult Epac1–/– mice. Moreover, Epac1–/– mice developed more severe hyperglycemia with increased β‐cell apoptosis and insulitis after multiple low‐dose streptozotocin (MLDS; 40 mg/kg) treatment than Epac1+/+ mice. Interestingly, Epac1–/– mice also showed metabolic defects, including increased respiratory exchange ratio (RER) and plasma triglyceride (TG), and more severe diet‐induced obesity with insulin resistance, which may contributed to β‐cell dysfunction. However, islets differentiated from Epac1–/– ES cells showed insulin secretion defect, reduced Glut2 and PDX‐1 expression, and abolished GLP‐1‐stimulated PCNA induction, suggesting a role of Epac1 in β‐cell function. The current study provides in vitro and in vivo evidence that Epac1 has an important role in GSIS of β cells and phenotype resembling metabolic syndrome. Kai, A. K. L., Lam, A. K. M., Chen, Y., Tai, A. C. P., Zhang, X., Lai, A. K. W., Yeung, P. K. K., Tam, S., Wang, J., Lam, K. S., Vanhoutte, P. M., Bos, J. L., Chung, S. S. M., Xu, A., Chung, S. K. Exchange protein activated by cAMP 1 (Epac1)‐deficient mice develop β‐cell dysfunction and metabolic syndrome. FASEBJ. 27, 4122–4135 (2013). www.fasebj.org
Muscle uncoupling protein 3 overexpression mimics endurance training and reduces circulating biomarkers of incomplete β‐oxidation
Authors: Aguer Céline , Fiehn Oliver , Seifert Erin L. , Bézaire Véronic , Meissen John K. , Daniels Amanda , Scott Kyle , Renaud Jean‐Marc , Padilla Marta , Bickel David R. , Dysart Michael , Adams Sean H. , Harper Mary‐Ellen
Published: June 2013

Exercise substantially improves metabolic health, making the elicited mechanisms important targets for novel therapeutic strategies. Uncoupling protein 3 (UCP3) is a mitochondrial inner membrane protein highly selectively expressed in skeletal muscle. Here we report that moderate UCP3 overexpression (roughly 3‐fold) in muscles of UCP3 transgenic (UCP3Tg) mice acts as an exercise mimetic in many ways. UCP3 overexpression increased spontaneous activity (~40%) and energy expenditure (~5–10%) and decreased oxidative stress (~ 15–20%), similar to exercise training in wild‐type (WT) mice. The increase in complete fatty acid oxidation (FAO; ~30% for WT and ~70% for UCP3 Tg) and energy expenditure (~8% for WT and 15% for UCP3 Tg) in response to endurance training was higher in UCP3 Tg than in WT mice, showing an additive effect of UCP3 and endurance training on these two parameters. Moreover, increases in circulating short‐chain acylcarnitines in response to acute exercise in untrained WT mice were absent with training or in UCP3 Tg mice. UCP3 overexpression had the same effect as training in decreasing long‐chain acylcarnitines. Outcomes coincided with a reduction in muscle carnitine acetyltransferase activity that catalyzes the formation of acylcarnitines. Overall, results are consistent with the conclusions that circulating acylcarnitines could be used as a marker of incomplete muscle FAO and that UCP3 is a potential target for the treatment of prevalent metabolic diseases in which muscle FAO is affected.—Aguer, C., Fiehn, O., Seifert, E. L., Bézaire, V., Meissen, J. K., Daniels, A., Scott, K., Renaud, J.‐M., Padilla, M., Bickel, D. R., Dysart, M., Adams, S. H., Harper, M.‐E. Muscle uncoupling protein 3 overexpression mimics endurance training and reduces circulating biomarkers of incomplete β‐oxidation. FASEB J. 27, 4213–4225 (2013). www.fasebj.org
An obesogenic diet during mouse pregnancy modifies maternal nutrient partitioning and the fetal growth trajectory
Authors: Sferruzzi‐Perri Amanda N. , Vaughan Owen R. , Haro Maria , Cooper Wendy N. , Musial Barbara , Charalambous Marika , Pestana Diogo , Ayyar Shruti , Ferguson‐Smith Anne C. , Burton Graham J. , Constancia Miguel , Fowden Abigail L.
Published: June 2013

In developed societies, high‐sugar and high‐fat (HSHF) diets are now the norm and are increasing the rates of maternal obesity during pregnancy. In pregnant rodents, these diets lead to cardiovascular and metabolic dysfunction in their adult offspring, but the intrauterine mechanisms involved remain unknown. This study shows that, relative to standard chow, HSHF feeding throughout mouse pregnancy increases maternal adiposity (+30%, P<0.05) and reduces fetoplacental growth at d 16 (–10%, P<0.001). At d 19, however, HSHF diet group pup weight had normalized, despite the HSHF diet group placenta remaining small and morphologically compromised. This altered fetal growth trajectory was associated with enhanced placental glucose and amino acid transfer (+35%, P<0.001) and expression of their transporters (+40%, P<0.024). HSHF feeding also up‐regulated placental expression of fatty acid transporter protein, metabolic signaling pathways (phosphoinositol 3‐kinase and mitogen‐activated protein kinase), and several growth regulatory imprinted genes (Igf2, Dlk1, Snrpn, Grb10, and H19) independently of changes in DNA methylation. Obesogenic diets during pregnancy, therefore, alter maternal nutrient partitioning, partly through changes in the placental phenotype, which helps to meet fetal nutrient demands for growth near term. However, by altering provision of specific nutrients, dietary‐induced placental adaptations have important roles in programming development with health implications for the offspring in later life.—Sferruzzi‐Perri, A N., Vaughan, O. R., Haro, M., Cooper, W. N., Musial, B., Charalambous, M., Pestana, D., Ayyar, S., Ferguson‐Smith, A C., Burton, G. J., Con‐stancia, M., Fowden, A. L., An obesogenic diet during mouse pregnancy modifies maternal nutrient partitioning and the fetal growth trajectory. FASEB J. 27, 3928–3937 (2013). www.fasebj.org