bluuebunny/crossref_metadata_2025 huggingface dataset:
A contribution to the many-fermion problem
Authors: Mattis Daniel C.
Published: August 2012

In this work we reexamine the many-fermion problem in arbitrary dimensions. It is shown that in two dimensions or higher, the Hamiltonian of interacting fermions can be separated into individual nonintersecting sectors labeled by the wave-vector $\vec q$q⃗. Within each sector the Hamiltonian maps onto a generalized version of the one-dimensional Luttinger model that resembles a boson string. These are chain-like quadratic forms in boson operators that are readily diagonalized in the absence of “exchange” corrections. Moreover, in a simple example involving SU(2) fermions, that of the Hubbard model, we show that it can be possible also to incorporate exchange terms and express them entirely within an enlarged set of string variables.
Polarization of glass containing fast and slow ions
Authors: Petrov M. I. , Lepen’kin Ya. A. , Lipovskii A. A.
Published: August 2012

Polarization of glasses containing two types of differing in mobility positive ions is modeled both for blocking and non-blocking anode conditions. Formation of slower ions concentration peak is demonstrated. Comparison of the model with known experimental results shows a good coincidence. The model is applicable to glass-based integrated optics.
Near critical electrolytes: Are the charge-charge sum rules obeyed?
Authors: Das Subir K. , Kim Young C. , Fisher Michael E.
Published: August 2012

In an electrolyte solution the charge-charge structure factor obeys $S_{ZZ}(k;T,\rho )=0+\xi _{Z,1}^2k^2\break -\xi _{Z,2}^4k^4+\cdots$SZZ(k;T,ρ)=0+ξZ,12k2−ξZ,24k4+⋯ , where ξZ, 1 and ξZ, 2 are the second- and fourth-moment charge-charge correlation lengths depending on the temperature T and the overall ion density ρ. The vanishing of the leading term, the first Stillinger-Lovett (SL) sum rule, simply reflects bulk electroneutrality. The second SL rule, or second-moment condition, dictates that ξZ, 1 = ξD, where the Debye screening length ξD is proportional to $\sqrt{T/\rho }$T/ρ. In this paper we present results from grand canonical Monte Carlo simulations of a fully size and charge symmetric1:1 (finely-discretized) hard-sphere electrolyte, or restricted primitive model. By design, electroneutrality is imposed during the simulations, so satisfying the first sum rule automatically. However, careful finite-size scaling analyses of extensive histogram reweighted data indicate that the second-moment condition is violated atcriticality, $\xi _{Z,1}^c$ξZ,1c exceeding $\xi _D^c$ξDc by approximately 8%. It is also found that $\xi _{Z,2}^4$ξZ,24 diverges to +∞ as T → Tc in a manner closely mirroring the density-density fluctuations, SNN(0). These findings contradict generalized Debye-Hückel theory and also the exactly soluble charge-symmetricspherical models, both of which support the second-moment condition at criticality and the finiteness of the fourth-moment. Nevertheless, the observed behavior is strikingly similar to that of the charge-asymmetricspherical models.
Gauge invariance of the nuclear spin/electron orbit interaction and NMR spectral parameters
Authors: Lazzeretti Paolo
Published: August 2012

A gauge transformation of the vector potential ${{{\bm{A}}}}^{{\bf m}_I}$AmI, associated to the magnetic dipole mI of nucleus I in a molecule, has been studied. The conditions for gauge invariance of nuclear magnetic shielding, nuclear spin/electron orbit contribution to spin-spin coupling between two nuclei, I and J, and electronic current density induced by mI, have been expressed via quantum mechanical sum rules that are identically satisfied for exact and optimal variational wavefunctions. It is shown that separate diamagnetic and paramagnetic contributions to the properties transform into one another in the gauge transformation, whereas their sum is invariant. Therefore, only total response properties have a physical meaning. In particular, the disjoint diamagnetic and paramagnetic components of nuclear spin/electron orbit contributions to coupling constants are not uniquely defined. The diamagnetic contribution to the nuclear spin-spin coupling tensor, evaluated as an expectation value in the Ramsey theory, can alternatively be expressed as a sum-over-states formula, by rewriting the second-order Hamiltonian in commutator form à la Geertsen, as previously reported by Sauer. Other sum-over-states formulae are obtained via a gauge transformation, by a procedure formally allowing for a continuous translation of the origin of the mI-induced current density, analogous to those previously proposed for magnetizabilities and nuclear magnetic shielding.
The nature of the ordered phase of the confined self-assembled rigid rod model
Authors: Almarza N. G. , Tavares J. M. , Telo da Gama M. M.
Published: August 2012

We investigate the nature of the ordered phase and the orientational correlations between adjacent layers of the confined three-dimensional self-assembled rigid rod model, on the cubic lattice. We find that the ordered phase at finite temperatures becomes uniaxial in the thermodynamic limit, by contrast to the ground state (partial) order where the orientation of the uncorrelated layers is perpendicular to one of the three lattice directions. The increase of the orientational correlation between layers as the number of layers increases suggests that the unconfined model may also exhibit uniaxial ordering at finite temperatures.
Adaptive lag synchronization of chaotic Cohen-Grossberg neural networks with discrete delays
Authors: Liu Qiming , Zhang Shihua
Published: August 2012

A class of Cohen-Grossberg neural networks with discrete delays are investigated in this paper. By using the suitable Lyapunov function, sufficient conditions for adaptive lag synchronization of such systems are obtained. Finally, a numerical example is given to demonstrate the main results.
A compact instrument for adjusting laser beams to be accurately coincident and coaxial and its use in biomedical imaging using wave-mixed laser sources
Authors: Amor R. , Norris G. , Dempster J. , Amos W. B. , McConnell G.
Published: August 2012

Biomedical imaging applications that involve nonlinear optical processes such as sum-frequency generation (SFG) and four-wave mixing require that the pulses are synchronized in time and the beams are coaxial to better than 400 μrad. For this reason, folding mirrors are normally used to extend the beam path over a few meters so that detectors can be put into the beams to check their overlap at the start of a long path and also at the end of it. We have made a portable instrument with a footprint of only 22 cm × 11 cm × 16 cm that uses a short focal length lens and a telephoto combination for viewing the near-field and far-field simultaneously. Our instrument is simple to build and use, and we show its application in coherent anti-Stokes Raman scattering microscopy and SFG-based two-photon fluorescence microscopy.
Structure simulation of ultrathin dichloromethane layer on a solid substrate by density functional theory and molecular dynamics simulations
Authors: Zubkov Victor V. , Komarov Pavel V.
Published: August 2012

The method for prediction of structural properties of ultrathin liquid layers has been developed on the base of the atomistic molecular dynamics (AMD) and the density functional theory (DFT). A comparative analysis of ultrathin dichloromethane layer density profiles on three types of solid flat substrates showed that these approaches can be effectively used as mutually complementary procedures to describe the structural properties of nanometer scale surface layers. We used AMD calculations to predict the dichloromethane layer density profile on a solid substrate. However, it is difficult and computationally expensive to calculate structural and thermodynamic layers properties. At the same time, DFT can retain the microscopic details of macroscopic systems at the calculative cost significantly lower than that used in AMD. Therefore, in context of DFT, the substrate potential parameters are adjusted to reproduce AMD data. Thus, the obtained potential allows us to compute structural characteristics and, further, can be used to predict other physical properties of ultrathin films within the DFT framework. For instance, we calculated the coefficient of thermal expansion of dichloromethane in the case of three different substrates such as graphite, silicon oxide, and gold.
Shishiodoshi unidirectional energy transfer mechanism in phenylene ethynylene dendrimers
Authors: Fernandez-Alberti S. , Roitberg Adrian E. , Kleiman Valeria D. , Nelson T. , Tretiak S.
Published: August 2012

Non-adiabatic excited-state molecular dynamics is used to study the ultrafast intramolecular energy transfer between two-, three-, and four-ring linear polyphenylene ethynylene chromophore units linked through meta-substitutions. Twenty excited-state electronic energies, with their corresponding gradients and nonadiabatic coupling vectors were included in the simulations. The initial laser excitation creates an exciton delocalized between the different absorbing two-ring linear PPE units. Thereafter, we observe an ultrafast directional change in the spatial localization of the transient electronic transition density. The analysis of the intramolecular flux of the transition density shows a sequential through-bond two-ring→three-ring→four-ring transfer as well as an effective through-space direct two-to-four ring transfer. The vibrational excitations of C≡C stretching motions change according to that. Finally, a mechanism of unidirectional energy transfer is presented based on the variation of the energy gaps between consecutive electronic excited states in response to the intramolecular flux of the transition density. The mechanism resembles a Shishiodoshi Japanese bamboo water fountain where, once the electronic population has been transferred to the state directly below in energy, the two states decouple thereby preventing energy transfer in the opposite direction.
Transition from order to chaos, and density limit, in magnetized plasmas
Authors: Carati A. , Zuin M. , Maiocchi A. , Marino M. , Martines E. , Galgani L.
Published: August 2012

It is known that a plasma in a magnetic field, conceived microscopically as a system of point charges, can exist in a magnetized state, and thus remain confined, inasmuch as it is in an ordered state of motion, with the charged particles performing gyrational motions transverse to the field. Here, we give an estimate of a threshold, beyond which transverse motions become chaotic, the electrons being unable to perform even one gyration, so that a breakdown should occur, with complete loss of confinement. The estimate is obtained by the methods of perturbation theory, taking as perturbing force acting on each electron that due to the so–called microfield, i.e., the electric field produced by all the other charges. We first obtain a general relation for the threshold, which involves the fluctuations of the microfield. Then, taking for such fluctuations, the formula given by Iglesias, Lebowitz, and MacGowan for the model of a one component plasma with neutralizing background, we obtain a definite formula for the threshold, which corresponds to a density limit increasing as the square of the imposed magnetic field. Such a theoretical density limit is found to fit pretty well the empirical data for collapses of fusion machines.
Note: Measurement of extreme-short current pulse duration of runaway electron beam in atmospheric pressure air
Authors: Tarasenko V. F. , Rybka D. V. , Burachenko A. G. , Lomaev M. I. , Balzovsky E. V.
Published: August 2012

This note reports the time-amplitude characteristic of the supershort avalanche electron beam with up to 20 ps time resolution. For the first time it is shown that the electron beam downstream of small-diameter diaphragms in atmospheric pressure air has a complex structure which depends on the interelectrode gap width and cathode design. With a spherical cathode and collimator the minimum duration at half maximum of the supershort avalanche electron beam current pulse was shown to be ∼25 ps. The minimum duration at half maximum of one peak in the pulses with two peaks can reach ∼25 ps too.
Effect of adatom surface diffusivity on microstructure and intrinsic stress evolutions during Ag film growth
Authors: Flötotto D. , Wang Z. M. , Jeurgens L. P. H. , Bischoff E. , Mittemeijer E. J.
Published: August 2012

The effect of the adatom surface diffusivity on the evolution of the microstructure and the intrinsic stress of thin metal films was investigated for the case of growth of polycrystalline Ag films on amorphous SiO2 (a-SiO2) and amorphous Ge (a-Ge) substrates, with high and low Ag adatom surface diffusivity, respectively. The surface diffusivity of the deposited Ag adatoms on the a-Ge substrate is suppressed also after coalescence of Ag islands due to the continuous (re)segregation of Ge at the surface of the growing film as evidenced by in-situ XPS. An assessment could be made of the role of adatom surface diffusivity on the microstructural development and the intrinsic stress evolution during film growth. As demonstrated by ex-situ TEM and ex-situ XRD, the Ag films grown on the a-SiO2 and a-Ge substrates possess strikingly different microstructures in terms of grain shape, grain size, and crystallographic texture. Nevertheless, the real-time in-situ stress measurements revealed a compressive → tensile → compressive stress evolution for the developing Ag films on both types of substrates, however on different time scales and with stress-component values of largely different magnitudes. It was concluded that (i) the microstructural development of metallic thin films is predominated by the surface diffusivity of the adatoms and (ii) the intrinsic stress evolution is largely controlled by the developing microstructure and the grain-boundary diffusivity.
Thickness dependence of temperature-induced emission mechanism in InGaN/AlGaN short-period superlattices
Authors: Noh Young-Kyun , Seo Jeong-Han , Choi Hyo-Seok , Kim Moon-Deock , Oh Jae-Eung
Published: August 2012

An analysis of temperature-dependent photoluminescence (PL) spectra for a series of InGaN/AlGaN short-period superlattices (SP-SLs) with different well and barrier thickness is presented. A quantitative model, based on Gaussian-like function of localized electronic states, to fit the temperature-dependent emission peak energy gives good fits over an extended temperature range for all samples. It is found that, among all parameters in the model, the degree of broadening of the Gaussian distribution is strongly dependent of the structural parameters of SP-SLs and determines the anomalous “S-shape” behavior of the temperature-dependent emission energy. In thin well and barrier samples with higher broadening parameter, the temperature-dependence of emission energy is different from those of typical “S-shape” behavior, which is characterized by the bigger red-shift with no blue shift in the temperature range used. The depth of localization, Ea-Eo, is smaller than the corresponding activation energy obtained from the thermal quenching of the PL intensity, thus, indicating that the thermal quenching activation energy and the localization due to band-gap fluctuation most likely have different origins. We demonstrate that, in the InGaN/AlGaN SP-SLs, the interface characteristics also contributes to the temperature-induced PL emission shift as much as the compositional fluctuation does.
Note: Refractive index sensing of turbid media by differentiation of the reflectance profile: Does error-correction work?
Authors: Goyal K. G. , Dong M. L. , Kane D. G. , Makkar S. S. , Worth B. W. , Bali L. M. , Bali S.
Published: August 2012

A widely used method for determining refractive index postulates that the derivative of the angular profile for light reflected from the sample is maximum at the critical angle for total internal reflection (TIR). It is well-known that in turbid media this “differentiation method” yields errors in refractive index. Unexplained anomalies in previous error-calculations are eliminated if one uses a recent model of TIR which departs from traditional Fresnel theory. However we find that, in practical situations, the refractive index obtained by differentiation even after error-correction is significantly different from the best estimate for the refractive index obtained by curve-fitting the reflectance data. Thus the differentiation method lacks scientific validity in turbid media.
Adiponectin regulates expression of hepatic genes critical for glucose and lipid metabolism
Authors: Liu Qingqing , Yuan Bingbing , Lo Kinyui Alice , Patterson Heide Christine , Sun Yutong , Lodish Harvey F.
Published: August 2012

The effects of adiponectin on hepatic glucose and lipid metabolism at transcriptional level are largely unknown. We profiled hepatic gene expression in adiponectin knockout (KO) and wild-type (WT) mice by RNA sequencing. Compared with WT mice, adiponectin KO mice fed a chow diet exhibited decreased mRNA expression of rate-limiting enzymes in several important glucose and lipid metabolic pathways, including glycolysis, tricarboxylic acid cycle, fatty-acid activation and synthesis, triglyceride synthesis, and cholesterol synthesis. In addition, binding of the transcription factor Hnf4a to DNAs encoding several key metabolic enzymes was reduced in KO mice, suggesting that adiponectin might regulate hepatic gene expression via Hnf4a. Phenotypically, adiponectin KO mice possessed smaller epididymal fat pads and showed reduced body weight compared with WT mice. When fed a high-fat diet, adiponectin KO mice showed significantly reduced lipid accumulation in the liver. These lipogenic defects are consistent with the down-regulation of lipogenic genes in the KO mice.
Observation of another's action but not eye gaze triggers allocentric visual perspective
Authors: Mazzarella Elisabetta , Hamilton Antonia , Trojano Luigi , Mastromauro Bianca , Conson Massimiliano
Published: August 2012

In the present paper, we investigated whether observation of bodily cues—that is, hand action and eye gaze—can modulate the onlooker's visual perspective taking. Participants were presented with scenes of an actor gazing at an object (or straight ahead) and grasping an object (or not) in a 2 × 2 factorial design and a control condition with no actor in the scene. In Experiment 1, two groups of subjects were explicitly required to judge the left/right location of the target from their own (egocentric group) or the actor's (allocentric group) point of view, whereas in Experiment 2 participants did not receive any instruction on the point of view to assume. In both experiments, allocentric coding (i.e., the actor's point of view) was triggered when the actor grasped the target, but not when he gazed towards it, or when he adopted a neutral posture. In Experiment 3, we demonstrate that the actor's gaze but not action affected participants' attention orienting. The different effects of others' grasping and eye gaze on observers' behaviour demonstrated that specific bodily cues convey distinctive information about other people's intentions.
Guiding and focusing of a nanosecond infrared laser within transient hollow plasma femtosecond filament channels
Authors: Wen Sy-Bor , Chen Chien-Fen , Mao Xianglei , Russo Richard E
Published: August 2012

Long distance guidance and focusing of infrared (IR) nanosecond-pulsed laser light in a hollow plasma channel formed with femtosecond pulsed laser plasma filaments is examined with numerical experiments. Numerical models show that a thick hollow plasma channel can provide low loss long distance (>100 m) guidance of the IR nanosecond-pulsed laser beam. The effectiveness of guidance is determined by the electron number density, thickness of the plasma filament shell and the size of the inner radius of the hollow plasma channel. The hollow plasma channel can be thought of as an open-space optical fibre. The required thickness of the plasma channel with specified electron number density and the inner radius can be estimated with modal analysis, similar to that used for optical fibres. In addition, with a small tapering angle in the hollow plasma channel, the guided light can be moderately focused during long distance propagation. Owing to the rapid decay of electron number density of a plasma channel in free space, the delay time between the generation of the plasma channel and the guided light along with the duration of the guided light are better to be maintained within a few nanoseconds.
Characteristics of plume plasma and its effects on ablation depth during ultrashort laser ablation of copper in air
Authors: Hu Wenqian , Shin Yung C , King Galen
Published: August 2012

The characteristics of plume plasma induced by ultrashort laser ablation of copper in air are studied experimentally and theoretically in this paper. The plasma front evolutions are captured using a high-speed intensified charge-coupled device camera, while the plasma temperature and electron number density evolutions are obtained from the plasma emission spectra measured by a high-precision spectrometer. For the theoretical study, a hybrid simulation model is proposed to combine an atomistic model for the early stage and a hydrodynamic model for the later stage. The simulation model is validated against the measurement results and shown to be capable of predicting plasma properties for a broader range of fluence, without being constrained by the signal strength as in the measurements. Both experimental and theoretical results show that the nonlinear relationship between plasma properties and laser fluence directly relates to the relationship between ablation depth and laser fluence. Therefore, the measurable and predictable plasma properties reveal the underlying ablation mechanism that has been studied primarily by theory.
Direct growth of TiO2 nanotubes on transparent substrates and their resistive switching characteristics
Authors: Chu Dewei , Younis Adnan , Li Sean
Published: August 2012

In this work, TiO2 nanotubes were directly grown by one-step electrochemical deposition process, in the absence of any templates or metal Ti substrates. The Au/TiO2 nanotube/fluorine-doped tin oxide glass capacitor exhibits stable bipolar resistive switching behaviour. The resistive switching behaviour may be related to the oxygen vacancies, giving rise to the formation of straight and extensible conducting filaments along the wall of each vertically aligned TiO2 nanotube. Superior stability in resistive switching characteristics was also observed, indicating that TiO2 nanotubes are one of the potential materials for next-generation nonvolatile memory applications.
Lyα DOMINANCE OF THE CLASSICAL T TAURI FAR-ULTRAVIOLET RADIATION FIELD
Authors: Schindhelm Rebecca N. , France Kevin , Herczeg Gregory J. , Bergin Edwin , Yang Hao , Brown Alexander , Brown Joanna M. , Linsky Jeffrey L. , Valenti Jeff
Published: August 2012

Far-ultraviolet (FUV) radiation plays an important role in determining chemical abundances in protoplanetary disks. H i Lyman α (Lyα) is suspected to be the dominant component of the FUV emission from Classical T Tauri Stars (CTTSs), but is difficult to measure directly due to circumstellar and interstellar H i absorption. To better characterize the intrinsic Lyα radiation, we present FUV spectra of 14 CTTSs taken with the Hubble Space Telescope Cosmic Origins Spectrograph and Space Telescope Imaging Spectrograph instruments. H2 fluorescence, commonly seen in the spectra of CTTSs, is excited by Lyα photons, providing an indirect measure of the Lyα flux incident upon the warm disk surface. We use observed H2 progression fluxes to reconstruct the CTTS Lyα profiles. The Lyα flux correlates with total measured FUV flux, in agreement with an accretion-related source of FUV emission. With a geometry-independent analysis, we confirm that in accreting T Tauri systems Lyα radiation dominates the FUV flux (∼1150 Å –1700 Å). In the systems surveyed this one line comprises 70%–90% of the total FUV flux.
Heart failure highlights in 2011
Authors: Westenbrink B. Daan , Damman Kevin , Rienstra Michiel , Maass Alexander H. , van der Meer Peter
Published: August 2012

Heart failure (HF) remains a major medical problem, and the European Journal of Heart Failure is dedicated to publishing research further investigating its pathophysiology and diagnosis in order to help clinicians alleviate symptoms and improve patient outcomes. This review reports on important studies in the field of HF published in 2011. All research areas are addressed, including experimental studies, biomarkers, clinical trials, arrhythmias, and new insights into the role of device therapy.
IgGs containing light chains of the λ- and κ- type and of all subclasses (IgG1–IgG4) from the sera of patients with systemic lupus erythematosus hydrolyze myelin basic protein
Authors: Bezuglova Anna M. , Konenkova Ludmila P. , Buneva Valentina N. , Nevinsky Georgy A.
Published: August 2012

Human myelin basic protein (hMBP)-hydrolyzing activity was recently shown to be an intrinsic property of antibodies from systemic lupus erythematosus (SLE) patients. Here, we present the first evidence demonstrating a significant diversity of different fractions of polyclonal IgGs (pIgGs) from SLE patients in their affinity for hMBP and in the ability of pIgGs to hydrolyze hMBP at different optimal pH values (5.3–9.5); the pH profiles of IgG1, IgG2, IgG3 and IgG4 were unique. IgGs containing the λ-type of light chains demonstrated higher relative activities (RAs) in the hydrolysis of hMBP and its oligopeptides (OPs) than κ-IgGs. IgGs of all four subclasses were catalytically active; their RAs in the hydrolysis of hMBP increased in the following order: IgG4 < IgG2 < IgG3 < IgG1. Metal-dependent proteolytic activity of λ-IgG, IgG1, IgG2 and IgG3 was higher than their serine protease-like activity, while these activities of κ-IgG were comparable. Phenylmethylsulfonylfluoride had almost no effect on the activity of IgG4, while EDTA significantly suppressed its activity. The RAs of λ-IgG in the hydrolysis of four OPs corresponding to different cleavage sites of hMBP were remarkably higher than those for κ-IgGs. IgG1–IgG4 demonstrated different RAs and patterns of hydrolysis of these four OPs. Although combination of Ca2+ plus Mg2+ was the best in the activation of IgG1 and IgG2, IgG3 and IgG4 demonstrated the highest activity in the presence of Ca2+ plus Co2+. The ratio of the RAs of λ-IgG, κ-IgG and IgG1–IgG4 preparations in all analyzed cases was individual for each preparation.
A heterozygous IDH1R132H/WT mutation induces genome-wide alterations in DNA methylation
Authors: Duncan Christopher G. , Barwick Benjamin G. , Jin Genglin , Rago Carlo , Kapoor-Vazirani Priya , Powell Doris R. , Chi Jen-Tsan , Bigner Darell D. , Vertino Paula M. , Yan Hai
Published: August 2012

Monoallelic point mutations of the NADP+-dependent isocitrate dehydrogenases IDH1 and IDH2 occur frequently in gliomas, acute myeloid leukemias, and chondromas, and display robust association with specific DNA hypermethylation signatures. Here we show that heterozygous expression of the IDH1R132H allele is sufficient to induce the genome-wide alterations in DNA methylation characteristic of these tumors. Using a gene-targeting approach, we knocked-in a single copy of the most frequently observed IDH1 mutation, R132H, into a human cancer cell line and profiled changes in DNA methylation at over 27,000 CpG dinucleotides relative to wild-type parental cells. We find that IDH1R132H/WT mutation induces widespread alterations in DNA methylation, including hypermethylation of 2010 and hypomethylation of 842 CpG loci. We demonstrate that many of these alterations are consistent with those observed in IDH1-mutant and G-CIMP+ primary gliomas and can segregate IDH wild-type and mutated tumors as well as those exhibiting the G-CIMP phenotype in unsupervised analysis of two primary glioma cohorts. Further, we show that the direction of IDH1R132H/WT-mediated DNA methylation change is largely dependent upon preexisting DNA methylation levels, resulting in depletion of moderately methylated loci. Additionally, whereas the levels of multiple histone H3 and H4 methylation modifications were globally increased, consistent with broad inhibition of histone demethylation, hypermethylation at H3K9 in particular accompanied locus-specific DNA hypermethylation at several genes down-regulated in IDH1R132H/WT knock-in cells. These data provide insight on epigenetic alterations induced by IDH1 mutations and support a causal role for IDH1R132H/WT mutants in driving epigenetic instability in human cancer cells.
New insights into the regulation of synaptic plasticity from an unexpected place: Hippocampal area CA2
Authors: Caruana Douglas A. , Alexander Georgia M. , Dudek Serena M.
Published: August 2012

The search for molecules that restrict synaptic plasticity in the brain has focused primarily on sensory systems during early postnatal development, as critical periods for inducing plasticity in sensory regions are easily defined. The recent discovery that Schaffer collateral inputs to hippocampal area CA2 do not readily support canonical activity-dependent long-term potentiation (LTP) serves as a reminder that the capacity for synaptic modification is also regulated anatomically across different brain regions. Hippocampal CA2 shares features with other similarly “LTP-resistant” brain areas in that many of the genes linked to synaptic function and the associated proteins known to restrict synaptic plasticity are expressed there. Add to this a rich complement of receptors and signaling molecules permissive for induction of atypical forms of synaptic potentiation, and area CA2 becomes an ideal model system for studying specific modulators of brain plasticity. Additionally, recent evidence suggests that hippocampal CA2 is instrumental for certain forms of learning, memory, and social behavior, but the links between CA2-enriched molecules and putative CA2-dependent behaviors are only just beginning to be made. In this review, we offer a detailed look at what is currently known about the synaptic plasticity in this important, yet largely overlooked component of the hippocampus and consider how the study of CA2 may provide clues to understanding the molecular signals critical to the modulation of synaptic function in different brain regions and across different stages of development.
Memory reactivation effects independent of reconsolidation
Authors: Gisquet-Verrier Pascale , Riccio David C.
Published: August 2012

Memory reactivation is an important process resulting from reexposure to salient training-related information whereby a memory is brought from an inactive to an active state. Reactivation is the first stage of memory retrieval but can result from the exposure to salient cues without any behavioral output. Such cue-induced reactivation, although frequently used by neuroscientists to study reconsolidation, has seldom been considered as a process in its own right and studied as such. This review presents arguments indicating that memory reactivation has two main consequences: (1) to enhance the accessibility of the target memory and (2) to make the memory malleable. Accordingly, reactivation creates a transient state during which the content of the memory is easily accessible and can be modified and/or updated. As both of these aspects can be observed shortly after memory reactivation, this review emphasizes that reconsolidation is not necessarily required for these processes and calls attention to reactivation as a factor in the dynamics of the memory.
Consolidation and translation regulation: Figure 1.
Authors: Gal-Ben-Ari Shunit , Kenney Justin W. , Ounalla-Saad Hadile , Taha Elham , David Orit , Levitan David , Gildish Iness , Panja Debabrata , Pai Balagopal , Wibrand Karin , Simpson T. Ian , Proud Christopher G. , Bramham Clive R. , Armstrong J. Douglas , Rosenblum Kobi
Published: August 2012

mRNA translation, or protein synthesis, is a major component of the transformation of the genetic code into any cellular activity. This complicated, multistep process is divided into three phases: initiation, elongation, and termination. Initiation is the step at which the ribosome is recruited to the mRNA, and is regarded as the major rate-limiting step in translation, while elongation consists of the elongation of the polypeptide chain; both steps are frequent targets for regulation, which is defined as a change in the rate of translation of an mRNA per unit time. In the normal brain, control of translation is a key mechanism for regulation of memory and synaptic plasticity consolidation, i.e., the off-line processing of acquired information. These regulation processes may differ between different brain structures or neuronal populations. Moreover, dysregulation of translation leads to pathological brain function such as memory impairment. Both normal and abnormal function of the translation machinery is believed to lead to translational up-regulation or down-regulation of a subset of mRNAs. However, the identification of these newly synthesized proteins and determination of the rates of protein synthesis or degradation taking place in different neuronal types and compartments at different time points in the brain demand new proteomic methods and system biology approaches. Here, we discuss in detail the relationship between translation regulation and memory or synaptic plasticity consolidation while focusing on a model of cortical-dependent taste learning task and hippocampal-dependent plasticity. In addition, we describe a novel systems biology perspective to better describe consolidation.
Role of signal transduction crosstalk between adenylyl cyclase and MAP kinase in hippocampus-dependent memory
Authors: Xia Zhengui , Storm Daniel R.
Published: August 2012

One of the intriguing questions in neurobiology is how long-term memory (LTM) traces are established and maintained in the brain. Memory can be divided into at least two temporally and mechanistically distinct forms. Short-term memory (STM) lasts no longer than several hours, while LTM persists for days or longer. A crucial step in the generation of LTM is consolidation, a process in which STM is converted to LTM. Hippocampus-dependent LTM depends on activation of Ca2+, Erk/MAP kinase (MAPK), and cAMP signaling pathways, as well as de novo gene expression and translation. One of the transcriptional pathways strongly implicated in LTM is the CREB/CRE (calcium, cAMP response element) transcriptional pathway. Interestingly, this transcriptional pathway may also contribute to other forms of neuroplasticity including adaptive responses to drugs. Evidence discussed in this review indicates that activation of the Erk1/2 MAP Kinase (MAPK)/CRE transcriptional pathway during the formation of hippocampus-dependent memory depends on calmodulin (CaM)-stimulated adenylyl cyclases.
Two Novel RING-Type Ubiquitin Ligases, RGLG3 and RGLG4, Are Essential for Jasmonate-Mediated Responses in Arabidopsis
Authors: Zhang Xu , Wu Qian , Ren Jiao , Qian Wanqiang , He Shanping , Huang Kuowei , Yu XiangChun , Gao Yin , Huang Ping , An Chengcai
Published: August 2012

Jasmonates (JAs) regulate various stress responses and development processes in plants, and the JA pathway is tightly controlled. In this study, we report the functional characterization of two novel RING-type ubiquitin ligases, RING DOMAIN LIGASE3 (RGLG3) and RGLG4, in modulating JA signaling. Both RGLG3 and RGLG4 possessed ubiquitin ligase activities and were widely distributed in Arabidopsis (Arabidopsis thaliana) tissues. Altered expression of RGLG3 and RGLG4 affected methyl JA-inhibited root growth and JA-inductive gene expression, which could be suppressed by the coronatine insensitive1 (coi1) mutant. rglg3 rglg4 also attenuated the inhibitory effect of JA-isoleucine-mimicking coronatine on root elongation, and consistently, rglg3 rglg4 was resistant to the coronatine-secreting pathogen Pseudomonas syringae pv tomato DC3000, suggesting that RGLG3 and RGLG4 acted in response to the coronatine and promoted JA-mediated pathogen susceptibility. In addition, rglg3 rglg4 repressed wound-stunted plant growth, wound-stimulated expression of JA-responsive genes, and wound-induced JA biosynthesis, indicating their roles in JA-dependent wound response. Furthermore, both RGLG3 and RGLG4 responded to methyl JA, P. syringae pv tomato DC3000, and wounding in a COI1-dependent manner. Taken together, these results indicate that the ubiquitin ligases RGLG3 and RGLG4 are essential upstream modulators of JA signaling in response to various stimuli.
A novel one-dimensional CoIIcoordination polymer:catena-poly[[hexaaquacobalt(II)] [[diaquabis(sulfato-κO)cobalt(II)]-μ-4,4′-bipyridine-κ2N:N′] [[triaqua(sulfato-κO)cobalt(II)]-μ-4,4′-bipyridine-κ2N:N′]]
Authors: Zhong Kai-Long , Qian Ming-Yi
Published: August 2012

The title compound, {[Co(H2O)6][Co(SO4)(C10H8N2)(H2O)3][Co(SO4)2(C10H8N2)(H2O)2]}n, contains three crystallographically unique CoIIcentres, all of which are in six-coordinated environments. One CoIIcentre is coordinated by two bridging 4,4′-bipyridine (4,4′-bipy) ligands, one sulfate ion and three aqua ligands. The second CoIIcentre is surrounded by two N atoms of two 4,4′-bipy ligands and four O atoms,i.e.two O atoms from two monodentate sulfate ions and two from water molecules. The third CoIIcentre forms part of a hexaaquacobalt(II) ion. In the crystal structure, there are two different one-dimensional chains, one being anionic and the other neutral, and adjacent chains are arranged in a cross-like fashion around the mid-point of the 4,4′-bipy ligands. The structure features O—H...O hydrogen-bonding interactions between sulfate anions and water molecules, resulting in a three-dimensional supramolecular network.
Tris(1,10-phenanthroline-κ2N,N′)iron(II) bis(2,4,5-tricarboxybenzoate) monohydrate and tris(2,2′-bipyridine-κ2N,N′)iron(II) 2,5-dicarboxybenzene-1,4-dicarboxylate–benzene-1,2,4,5-tetracarboxylic acid–water (1/1/2)
Authors: Zhong Kai-Long
Published: August 2012

The title compounds, tris(1,10-phenanthroline-κ2N,N′)iron(II) bis(2,4,5-tricarboxybenzoate) monohydrate, [Fe(C12H8N2)3](C10H5O8)2·H2O, (I), and tris(2,2′-bipyridine-κ2N,N′)iron(II) 2,5-dicarboxybenzene-1,4-dicarboxylate–benzene-1,2,4,5-tetracarboxylic acid–water (1/1/2), [Fe(C10H8N2)3](C10H4O8)·C10H6O8·2H2O, (II), were obtained during an attempt to synthesize a mixed-ligand complex of FeIIwith an N-containing ligand and benzene-1,2,4,5-tetracarboxylic acidviaa solvothermal reaction. In both mononuclear complexes, each FeIImetal ion is six-coordinated in a distorted octahedral manner by six N atoms from three chelating 1,10-phenanthroline or 2,2′-bipyridine ligands. In compound (I), the FeIIatom lies on a twofold axis in the space groupC2/c, whereas (II) crystallizes in the space groupP21/n. In both compounds, the uncoordinated carboxylate anions and water molecules are linked by typical O—H...O hydrogen bonds, generating extensive three-dimensional hydrogen-bond networks which surround the cations.
Overexpression of enhancer of zeste homolog 2 and MUC1 may be related to malignant behaviour in intraductal papillary neoplasm of the bile duct
Authors: Sasaki Motoko , Matsubara Takashi , Yoneda Norihide , Nomoto Kazuhiro , Tsuneyama Koichi , Sato Yasunori , Nakanuma Yasuni
Published: August 2012

Aims:  Intraductal papillary neoplasm of the bile duct (IPNB) usually has a favourable prognosis, but occasionally is associated with invasive carcinoma. Overexpression of the polycomb group protein enhancer of zeste homolog 2 (EZH2) is involved in the progression of malignant tumours. In this study, we examined the significance of EZH2 expression in IPNB and its association with clinicopathological features and the expression of p16INK4a, p53 and mucin core proteins.

Methods and results:  We examined immunohistochemically the expression of EZH2, p16INK4a, MUC mucin core proteins and p53 in 15 patients with IPNB without invasion, including the cystic variant [male/female ratio (M/F) = 9/6], and in 19 with IPNB associated with invasive carcinoma (M/F = 13/6). The expression levels of EZH2, p53 and MUC1 were significantly lower (P < 0.01), and of MUC6 were significantly higher (P < 0.05), in IPNB without invasion than in IPNB with invasion. Expression of EZH2 was significantly correlated with expression of MUC1 (P < 0.01) and inversely correlated with expression of MUC6 (P < 0.05). In cholangiocarcinoma cells (HuCTT‐1 and TFK‐1), knockdown of EZH2 and MUC1 by small interfering RNA decreased invasion and proliferation, whereas knockdown of MUC6 increased invasion.

Conclusions:  Overexpression of EZH2 may be associated with malignant behaviour in IPNB in parallel with up‐regulated MUC1 expression and down‐regulated MUC6 expression.
Neuronally expressed Ras‐family GTPase Di‐Ras modulates synaptic activity in Caenorhabditis elegans
Authors: Tada Minoru , Gengyo‐Ando Keiko , Kobayashi Tetsuo , Fukuyama Masamitsu , Mitani Shohei , Kontani Kenji , Katada Toshiaki
Published: August 2012

Ras‐family GTPases regulate a wide variety of cellular functions including cell growth and differentiation. Di‐Ras, which belongs to a distinct subfamily of Ras‐family GTPases, is expressed predominantly in brain, but the role of Di‐Ras in nervous systems remains totally unknown. Here, we report that the Caenorhabditis elegans Di‐Ras homologue drn‐1 is expressed specifically in neuronal cells and involved in synaptic function at neuromuscular junctions. Loss of function of drn‐1 conferred resistance to the acetylcholinesterase inhibitor aldicarb and partially suppressed the aldicarb‐hypersensitive phenotypes of heterotrimeric G‐protein mutants, in which acetylcholine release is up‐regulated. drn‐1 mutants displayed no apparent defects in the axonal distribution of the membrane‐bound second messenger diacylglycerol (DAG), which is a key stimulator of acetylcholine release. Finally, we have identified EPAC‐1, a C. elegans Epac homologue, as a binding partner for DRN‐1. Deletion mutants of epac‐1 displayed an aldicarb‐resistant phenotype as drn‐1 mutants. Genetic analysis of drn‐1 and epac‐1 showed that they acted in the same pathway to control acetylcholine release. Furthermore, DRN‐1 and EPAC‐1 were co‐immunoprecipitated. These findings suggest that DRN‐1 may function cooperatively with EPAC‐1 to modulate synaptic activity in C. elegans.
The effect of ensiling and fractionation on the suitability for combustion of three common grassland species at sequential harvest dates
Authors: McEniry J. , Finnan J. , King C. , O'Kiely P.
Published: August 2012

In a Green Biorefinery processing green biomass, one possible application for the press‐cake fraction is as biomass fuel for combustion. In an industrial setting, the preservation of herbage as silage and its subsequent fractionation into press‐juice and press‐cake fractions represent the two major process steps in the utilization of green biomass. This study investigated (i) the effects of ensiling and fractionation on the chemical composition of three common temperate grassland species harvested at different stages of maturity and (ii) the suitability of the herbage of these species for thermal combustion. The high contents of ash, N, Cl and K in perennial ryegrass, cocksfoot and red clover, at both pre‐ and post‐ensiling, make these materials less suitable for combustion in certain applications. The loss of soluble/fermentable organic matter during ensiling increased the relative proportions of fibre, ash and N in the herbage, but these changes were relatively minor. In contrast, the substantial reduction in the concentration of compounds such as ash, N, Cl and K during fractionation improved the suitability of the press‐cake fraction for combustion compared with the parent material. Press‐cake prepared from later‐harvested grass herbage with lower ash, S and N contents would be more suitable for combustion.
Novel mutations in calcium/calmodulin‐dependent protein kinase IV (CAMK4) gene in infertile men
Authors: Khattri A. , Reddy V. P. , Pandey R. K. , Sudhakar D. V. S. , Gupta N. J. , Chakravarty B. N. , Deenadayal M. , Singh L. , Thangaraj K.
Published: August 2012

Calcium/calmodulin‐dependent protein kinase IV (CAMK4) is a multifunctional serine/threonine protein kinase, which plays an important role in the spermatogenesis by phosphorylating protamines. It has been shown to be involved in the regulation of human sperm motility. Moreover, the Camk4 knockout mice were infertile because of severely reduced sperm count and morphological abnormalities. As no study is available on the association of this gene with male infertility, we analysed all the exons of CAMK4 gene in ethnically matched 283 infertile and 268 fertile Indian men. We identified twenty nucleotide substitutions, of which twelve were novel. Of these novel variants, eight were exclusively detected in infertile men. Moreover, two infertile men‐specific mutations were non‐synonymous replacing amino acids at the highly conserved region. In silico analysis predicted both of these mutations as ‘deleterious’. In addition to nucleotide substitutions, we identified five novel insertion–deletion mutations; of these, g.150264_66delGCG was exclusively found in two oligoasthenoteratozoospermic men. In silico analysis of infertile men exclusive mutations predicted that they can alter/diminish the potential binding sites of splicing factors, which may affect the mRNA splicing and protein translation. Our study suggests that the mutations in CAMK4 may lead to abnormal semen parameters.
Does psychological well‐being mediate the association between experiences of acts of offensive behaviour and turnover among care workers? A longitudinal analysis
Authors: Clausen Thomas , Hogh Annie , Carneiro Isabella Gomes , Borg Vilhelm
Published: August 2012

Aim

To investigate whether the psychological well‐being of care workers in the Danish eldercare services mediated the association between experiences of acts of offensive behaviour and actual turnover.

Background

Research suggests that experiences of acts of offensive behaviour are associated with risk of turnover. However, little is known about the longitudinal associations between experiences of different types of offensive behaviour (threats, violence, bullying, and unwanted sexual attention) and risk of actual turnover.

Design

A prospective cohort study.

Methods

The study was conducted among employees in the eldercare services in Denmark. Employees aged 55 or more and non‐care staff were excluded from the study. Employees who were working in eldercare at baseline (2005) and no longer worked in eldercare at follow‐up (2006) were interviewed through questionnaires. Respondents to this questionnaire were coded as cases of turnover (N = 608) and were compared with employees who had not changed jobs during follow‐up (N = 4330). Data on experiences of acts of offensive behaviour and well‐being were measured at baseline. Data were analysed using logistic regression analysis.

Results

Frequent and occasional experiences of bullying and threats and occasional experiences of unwanted sexual attention at baseline entailed a significantly increased risk of turnover at follow‐up. Further analyses showed that psychological well‐being significantly reduced the risk of turnover and that well‐being partially mediated the association between bullying and turnover and fully mediated the association between threats, unwanted sexual attention, and turnover.

Conclusion

Prevention of threats, unwanted sexual attention and – especially – bullying may contribute towards improving well‐being and reducing turnover among eldercare staff.