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The nature and origin of the Galactic warp represent one of the open questions posed by Galactic evolution. Thanks to Gaia high precision absolute astrometry, steps towards the understanding of the warp's dynamical nature can be made. Indeed, proper motions for long-lived stable warp are expected to show measurable trends in the component vertical to the galactic plane. Within this context, we search for the kinematic warp signal in the first Gaia data release (DR1). By analyzing distant spectroscopically-identified OB stars in the Hipparcos subset in Gaia DR1, we find that the kinematic trends cannot be explained by a simple model of a long-lived warp. We therefore discuss possible scenarios for the interpretation of the obtained results. We also present current work in progress to select a larger sample of OB star candidates from the Tycho-Gaia Astrometric Solution (TGAS) subsample in DR1, and delineate the points that we will be addressing in the near future.
We use methods of differential astrometry to construct a small field inertial reference frame stable at the micro-arcsecond level. Using Gaia measurements of field angles we look at the influence of the number of reference stars and the stars magnitude as well as astrometric systematics on the total error budget with the help of Gaia-like simulations around the Ecliptic Pole in a differential astrometric scenario. We find that the systematic errors are modeled and reliably estimated to the μas level even in fields with a modest number of 37 stars with G <13 mag over a 0.24 sq. degrees field of view for short timescales of the order of a day for a perfect instrument and with high-cadence observations. Accounting for large-scale calibrations by including the geometric instrument model over such short timescales requires fainter stars down to G=14 mag without diminishing the accuracy of the reference frame.
Hopes to identify genetic susceptibility loci accounting for the heritability seen in unipolar depression have not been fully realized. Family history remains the ‘gold standard’ for both risk stratification and prognosis in complex phenotypes such as depression. Meanwhile, the physiological mechanisms underlying life-event triggers for depression remain opaque. Epigenetics, comprising heritable changes in gene expression other than alterations of the nucleotide sequence, may offer a way to deepen our understanding of the aetiology and pathophysiology of unipolar depression and optimize treatments. A heuristic target for exploring the relevance of epigenetic changes in unipolar depression is the hypothalamic–pituitary–adrenal (HPA) axis. The glucocorticoid receptor (GR) gene (NR3C1) has been found to be susceptible to epigenetic modification, specifically DNA methylation, in the context of environmental stress such as early life trauma, which is an established risk for depression later in life.
In this paper we discuss the progress that has been made by studies that have investigated the relationship between depression, early trauma, the HPA axis and the NR3C1 gene. Difficulties with the design of these studies are also explored.
Future efforts will need to comprehensively address epigenetic natural histories at the population, tissue, cell and gene levels. The complex interactions between the epigenome, genome and environment, as well as ongoing nosological difficulties, also pose significant challenges.
The work that has been done so far is nevertheless encouraging and suggests potential mechanistic and biomarker roles for differential DNA methylation patterns in NR3C1 as well as novel therapeutic targets.
Most of the discovered exoplanets are close to our sun. Usually their host star is with large proper motions, which is an important parameter for exoplanet searching. The first version of absolute proper motions catalog achieved based on Digitized Sky Survey Schmidt plate where outside the galactic plane |b|≥27° is presented, resulting in a zero point error less than ± 0.3 mas/yr, and the overall accuracy better than ± 4.5 mas/yr for objects brighter than RF=18.5, and ranging from 4.5 to 9.0 mas/yr for objects with magnitude 18.5<RF<20.5. The systematic errors of absolute proper motions related to the position, magnitude and color are practically all removed. The sky cover of this catalog is 22,525 degree2, the mean density is 6444 objects/degree2 and the magnitude limit is around RF=20.5.
We report on the parsec program, which observed 140 L and T dwarfs on a regular basis from 2007 to 2011, using the WIFI camera on the ESO/2.2 m telescope. Trigonometric parallaxes at 5 mas precision are derived for 49 objects, and mas yr−1-level proper motions are derived for approximately 200,000 objects in the same fields. We discuss image cleaning, object centroiding, and astrometric methods, in particular three different approaches for trigonometric parallax determination.
Small ground-based telescopes can effectively be used to look for transiting rocky planets around nearby low-mass M stars, as recently demonstrated for example by the MEarth project. Since December 2009 at the Astronomical Observatory of the Autonomous Region of Aosta Valley (OAVdA) we are monitoring photometrically a sample of red dwarfs with accurate parallax measurements. The primary goal of this ‘pilot study’ is the characterization of the photometric microvariability of each target over a typical period of approximately 2 months. This is the preparatory step to long-term survey with an array of identical small telescopes, with kick-off in early 2011. Here we discuss the present status of the study, describing the stellar sample, and presenting the most interesting results obtained so far, including the aggressive data analysis devoted to the characterization of the variability properties of the sample and the search for transit-like signals.
Introduction: origins and development of the ecosystem health concept
The need to understand and quantify ecosystem behaviour and condition has come to the forefront of environmental policy due to a greater emphasis on environmental sustainability and an accompanying recognition of the scarcity of natural resources, such as water, soil and biological diversity. Increasing concern regarding human impacts on the environment and the possibility that some human-induced changes in ecological systems may be irreversible has also focused attention on ways in which such changes can be assessed and, if possible, avoided. From the policy maker's perspective, the concern is not only in terms of the possible extent of these problems, but also the likelihood of their occurrence and the timeframe over which they may operate. In the context of global climate change, understanding the functioning of ecosystems, and how their health and performance can be measured and monitored over time are of critical importance, since these are linked inextricably with human health and well-being.
A considerable body of literature over the past decade has sought to define ecosystem health in practical terms. The majority of the definitions of ecosystem health concentrates exclusively on ecological aspects. For example, Costanza (1992) defines the term as follows: ‘An ecological system is healthy and free from “distress syndrome” if it is stable and sustainable – that is, if it is active and maintains its organisation and autonomy over time and is resilient to stress.’
Thick disks have been observed in many disk galaxies and our Galaxy, the Milky Way, also
presents a thick disk whose main spatial, kinematic, and chemical features of this
population are well established. However, the origin of this ancient component is still
unclear in spite the many studies carried out and several formation scenarios proposed
until now. For the first time to our knowledge, we found evidence of a
kinematics-metallicity correlation, of about 40–50 km s-1 per dex, amongst
thick disk stars at 1 kpc
< |z| < 3 kpc and
with abundance −1 <[Fe/H]< −0.5.
This finding sets important constraints on the origin of the thick disk in the context of
CDM hierarchical galaxy formation mechanisms and of secular evolutionary processes in
galactic disks. This result is reported and, preliminary results, based on new N-body high
numerical resolution simulations of stellar disks endowed with a bulge inside a dark
matter NFW halo, are presented.
The growing awareness of the importance of the fossil record in the Milky Way for
constraining galaxy formation theory is reflected by the increasing number of new ground-
and space-based surveys designed to unravel the formation history of the Galaxy. Recently,
a new kinematic survey has been produced by means of spectro-photometric data from the
Sloan Digital Sky Survey (SDSS-DR7) and high-quality proper motions derived from
multiepoch positions from the Guide Star Catalogue II (GSC-II). In this framework, we
assembled a sample of ~ 30 000 FGK nearby metal-poor (sub)dwarfs for which
selection and distance estimates take advantage of accurate stellar atmospheric parameters
(effective temperature, surface gravity and metallicity) derived from SDSS spectra. Here,
as one of the most interesting applications of this catalogue, we consider the feasibility
of probing fossil signatures of the formation of the Milky Way by selecting and analysing
subsamples of stars as tracers of the seven-dimensional space distribution (full
phase-space coordinates plus chemical abundance) of the Galactic halo population within a
few kiloparsecs from the Sun. Preliminary results exhibit statistical evidence for
discrete overdensities localised in kinematics and in the space of adiabatic invariants
(angular momentum and energy). By examination of their intrinsic properties, we suggest
that they may be possible fossil signatures of past mergers or other accretion events.
Botulism in UK cattle has been confirmed by demonstrating type C botulinum toxin in sera from affected animals. Evidence is presented indicating the source of intoxication to be poultry carcasses containing type C Clostridium botulinum and its toxin. The organism was also found in poultry litter and in alimentary tract samples from slaughtered animals. The implications of these findings are discussed.
In this work we present the study of fabrication, Ge incorporation, structure and electronic properties of nano-structured GeySi1-y:H films with y>0.5 prepared by low frequency (LF) PECVD. GeySi1-y:H films were deposited by LF PECVD at a frequency f= 110 kHz from SiH4+GeH4+H2 gas mixture. SiH4 and GeH4 flows were varied to fabricate the films in wide range of 0<y<l. Hydrogen dilution was varied in the range of RH =20 to 80. Structure of the films was studied by AFM and SEM with consequent image processing to extract statistical parameters such as grain distribution and mean values. Composition of the films was characterized by SIMS and EDX. Electronic properties were characterized by temperature dependence of conductivity, spectral dependence of optical absorption. Sub-gap absorption was characterized by Urbach energy, EU; and defect absorption, αD. We observed grain like nano-structure with Gauss distribution of grain diameters by both AFM and SEM measurements. The most interesting films had mean grain diameter<D> = 24.0±0.7 nm, dispersion D=11.0±0.2 nm and fill factor FF=0.313, Ge content y=0.96-0.97(by SIMS and EDS). These films showed also the lowest values of Urbach energy EU = 0.030 eV and low defect absorption αD = 5×102 cm −1 (at photon energy hv = 1.04 eV) indicating on low density of localized states in mobility gap. Doped films have been also fabricated and studied. Finally we shall discuss application of the above films in photovoltaic devices.
TiO2 is an attractive anode material for Li-ion batteries due to its high capacity, high mechanical stability during Li intercalation/deintercalation process, limited side reactions with the electrolyte, low cost, and environmental friendliness. In this study, titanium hydroxide gel films were prepared in acidic aqueous solutions of TiOSO4, H2O2 and KNO3 by potentiostatic cathodic electrosynthesis on various copper substrates, including planar Cu foil, mechanically polished planar Cu foil, and Cu nanorod arrays grown on Cu foil. Crystalline TiO2 films were obtained by heat treating the electrodeposited titanium hydroxide gel films at 500 oC in argon atmosphere. The morphology and microstructure of the TiO2 films were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD). SEM results showed that after deposition, each Cu nanorod has been covered by a layer of TiO2 gel, forming a core-shell structure. The effects of Cu nanorod arrays on the morphology and the electrochemical property of the TiO2 deposits were discussed.
A novel Ce4+/Ce3+- V2+/V3+ redox flow cell has been investigated. It was composed of the Ce4+/Ce3+ couple, which replaced the V5+/V4+ couple of the all6vanadium redox flow cell, and the V2+/V3+ couple. The normal potential and the kinetic parameters for anodic oxidation of Ce3+ and cathodic reduction of Ce4+ were measured. The results showed that the surface of platinum electrode was fully covered with type I oxide that inhibited the reduction of Ce4+. The reversibility of the Ce4+/Ce3+ couple improved with the increase of H2SO4 concentration, but both higher energy efficiency and coulombic efficiency were observed in 0.5 mol/dm3 H2SO4 solution. Different electrochemically active substances were found to exist at various state of charge (SOC) and the reversibility of the Ce4+/Ce3+ couple at the carbon electrode was found to be superior to platinum electrode. Periodic charge6discharge measurements were conducted under constant current and constant load with the proposed Ce6V redox flow cell. The results indicated that the coulombic efficiency remained around 90% and the discharge voltage stabilized between 1.5 and 1.2 V. But as the cycle numbers increased, the discharge capacity declined a bit and a better result might be expected by improving the separator materials and increase the concentration of electro6active materials. By comparison with the existing Fe6Cr, Fe6Ti and all6vanadium redox flow cell, the Ce6V system has a higher open6circuit voltage (OCV). And results from this preliminary study suggest that the novel Ce6V redox flow cell is a promising energy storage system and is worthy of further studies.
The remarkable ability of magnesium to store significant quantities of hydrogen has fostered intense research efforts in the last years in view of its future applications where light and safe hydrogen-storage media are needed. Magnesium material, characterized by light weight and low cost of production, can reversibly store about 7.7 wt% hydrogen. However, further research is needed since Mg has a high operation temperature and slow absorption kinetics that prevent the use in practical applications. For these reasons a detailed study of the interface between Mg and MgH2 is needed. Further insights are gained by characterizing the Mg-MgH2 system from both the experimental and the numerical point of view.
The study of the MgH2-Mg phase transformation in powder samples has been performed to gain detailed metallographic information. A method for studying this phase transformation by cross sectional samples scanning electron microscopy observation of partially transformed material has been developed. This method exploits the peculiar features of this system where the MgH2 phase is insulating and the Mg is a metallic conducting phase. This difference can induce a contrast between the two phases owing to the different secondary emission yield. Further insights are gained by characterizing Mg-MgH2 interfaces by means of accurate first-principle molecular dynamics simulations based on the density-functional theory. Extensive electronic structure calculations are used to characterize the equilibrium properties and the behavior of the surfaces in terms of total energy considerations and atomic diffusion.
We synthesized a methanol electrocatalyst with high activity and low noble metal content. The electrocatalyst consists of carbon&supported PtRu nanoparticles, which have 1-2 Pt monoatomic layers on Ru nanocores. In spite of the pure Pt surface, the catalyst showed high catalytic activity when used in the anode of a direct methanol fuel cell. Clearly the underlying Ru atoms modified the property of the surface Pt atoms, bringing about the high catalytic activity.
The electrochemical cycling performance of high purity single wall carbon nanotube (SWCNT) paper electrodes has been measured for a series of electrolyte solvent compositions. The effects of varying the galvanostatic charge rate and cycling temperature on lithium ion capacity have been evaluated between 25-100 °C. The measured reversible lithium ion capacities for SWCNT anodes range from 600-1000 mAh/g for a 1M LiPF6 electrolyte, depending on solvent composition and cycling temperature. The solid-electrolyte-interface (SEI) formation and first cycle charge loss are also shown to vary dramatically with carbonate solvent selection and illustrate the importance of solvent alkyl chain length and polarity on SWCNT capacity. SWCNT anodes have also been incorporated into full battery designs using LiCoO2 cathode composites. An electrochemical pre-lithiation sequence, prior to battery assembly, has been developed to mitigate the first cycle charge loss of SWCNT anodes. The pre-lithiated SWCNT anodes show reversible cycling at varying charge rates and depths of discharge with the cathode system. The summary of data shows that the structural integrity of individual SWCNTs is preserved after cycling, and that free-standing SWCNT paper electrodes represent an attractive material for lithium ion batteries.
In this study, we explored the synthesis of LiMnPO4 through hydrothermal methods using urea as the hydroxide ion source. The hydrothermally prepared LiMnPO4 was examined through x, ray diffraction, microscopy, surface area and electrochemical measurements. Small crystallites were formed and significant agglomeration of particles was observed. The effect of additives to control nucleation and growth of the LiMnPO4 is reported. None of the attempted additives led to the desired morphology. At a C/5 discharge rate, a capacity of about 53 mAh/g was observed for a carbon coated sample of hydrothermally prepared LiMnPO4.
Microscopic mechanism of Hydrogen-Induced Amorphization (HIA) in AB2 C15 Laves phase compound is studied. Experimentally, compounds in which A atoms are contracted and B atoms are expanded in Laves phase show HIA. It suggests that the relative atomic size is the controlling factor. We investigate the role of the size effect by molecular Dynamics (MD) methods using Lennard-Jones pair-wise potentials. Our simulations show that in such a compound, the bulk modulus is remarkably reduced by hydrogenation compared to the isotropic tensile load, so that elastic instability is facilitated. This situation is caused by the negative increase of the pressure-fluctuation contribution in the elastic constant. The relaxation of B-atom positions by hydrogenation gives the fluctuation contribution. The fluctuation effect is essential in the elastic instability, although the energy change is small.