Euclidean thermal spinor Green's function in the spacetime of a straight cosmic string

Within the framework of the quantum field theory at finite temperature on a conical space, we determine the Euclidean thermal spinor Green's function for a massless spinor field. We then calculate the thermal average of the energy-momentum tensor of a thermal bath of massless fermions. In the high-temperature limit, we find that the straight cosmic string does not perturb the thermal bathComment: 11 pages, latex, no figure

The HARPS search for southern extrasolar planets XXV. Results from the metal-poor sample

Searching for extrasolar planets around stars of different metallicity may provide strong constraints to the models of planet formation and evolution. In this paper we present the overall results of a HARPS (a high-precision spectrograph mostly dedicated to deriving precise radial velocities) program to search for planets orbiting a sample of 104 metal-poor stars (selected [Fe/H] below -0.5). Radial velocity time series of each star are presented and searched for signals using several statistical diagnostics. Stars with detected signals are presented, including 3 attributed to the presence of previously announced giant planets orbiting the stars HD171028, HD181720, and HD190984. Several binary stars and at least one case of a coherent signal caused by activity-related phenomena are presented. One very promising new, possible giant planet orbiting the star HD107094 is discussed, and the results are analyzed in light of the metallicity-giant planet correlation. We conclude that the frequency of giant planets orbiting metal-poor stars may be higher than previously thought, probably reflecting the higher precision of the HARPS survey. In the metallicity domain of our sample, we also find evidence that the frequency of planets is a steeply rising function of the stellar metal content, as found for higher metallicity stars.Comment: Accepted for publication in A&

Reptilia, Squamata, Polychrotidae, <i>Anolis fuscoauratus</i> D'Orbigny, 1837: Distribution extension for the state of Rio Grande do Norte, Brazil

We provide the first record of Anolis fuscoauratus D’Orbigny, 1837 for the state of Rio Grande do Norte anda distribution map for the species in the Atlantic Rainforest of northeastern Brazil. The record of A. fuscoauratus in themunicipality of Tibau do Sul, state of Rio Grande do Norte, represents a distribution extension of 170 km northwesternfrom the municipality of Cabedelo, state of Paraíba. This is the northernmost record of this species in the Atlantic Rainforest

Disconnection and reconnection: the morphological basis of (mal)adaptation to stress

We would like to thank Antonio Pinheiro, Hugo Almeida, and José Miguel Soares for help with the illustrations. We also thank all past and present members of our laboratories for stimulating discussions.Maladaptive responses to stress and the associated hypersecretion of glucocorticoids cause psychopathologies ranging from hyperemotional states and mood dysfunction to cognitive impairments. Research in both humans and animal models has begun to identify morphological correlates of these functional changes. These include dendritic and synaptic reorganization, glial remodeling, and altered cell fate in cortical and subcortical structures. The emerging view is that stress induces a disconnection syndrome’ whereby the transmission and integration of information that are critical for orchestrating appropriate physiological and behavioral responses are perturbed. High-resolution spatiotemporal mapping of the complete neural circuitry and identification of the cellular processes impacted by stress will help to advance discovery of strategies to reduce or reverse the burden of stress-related neuropsychiatric disorders.Work in our laboratories was supported by the German Academic Exchange Service - Acções Luso-Alemãs, Fundação para a Ciência e Tecnologia (PTDC/SAUNSC/ 111814/2009), and European Union FP7 (SwitchBox Project, Contract 259772; Neuroendocrine Immune Networks in Ageing Scientific Network, Contract 238665)

Protein-ligand docking study: diterpenes from Juniperus brevifolia as anticancer and antimicrobial agentes

REDCAT: Natural Products and related Redox Catalysts: Basic Research and Applications in Medicine and Agriculture, Aveiro, 25-27 Novembro de 2012.From leaves of Juniperus brevifolia, an endemic conifer from Azores, were isolated and structurally characterized, several dehydroabietane and sandaracopimarane derivatives. Some of them (1-4), displayed antiproliferative activity against cancer cell lines (HeLa, A-549 and MCF-7) and bactericidal effect against Bacillus cereus at different concentrations tested. However, it is not known how these compounds interact with most often proteins involved in the antimicrobial and cytotoxic mechanisms. Protein-ligand docking is mainly used to predict (energy and conformation wise) how small molecules bind to a protein of known 3D structure and to predict possible molecular targets for a set of compounds. In this work, the docking studies were performed, using the FlexScreen program, in order to pick molecular targets from a large set of common anticancer (63) and antimicrobial (39) targets to the selected compounds 1-4. The predicted interactions established between the compounds under study and the anticancer targets revealed that the compounds 1 and 3 interact preferentially with phosphatidylinositol-3,4,5-trisphosphate 5-phosphatase 2, whereas compounds 2 and 4 interact preferentially with human mitochondrial peptide deformylase and -tubulin, respectively. Studying the interactions between the compounds 1 and 3 and the antimicrobial targets we predict that these compounds interact preferentially with RNA polymerase and peptide deformylase. These results provide additional understanding of the cytotoxic and antimicrobial effects of diterpenes studied. These preliminary computational docking predictions of therapeutic targets were established working with just 4 compounds, and to obtain more reliable predictions the number of compounds needs to be increased.Thanks are due to the University of Azores, FCT, FEDER, BIOPHARMAC - MAC/1/C104 and Project PEst-OE/QUI/UI0674/2011

Electron spin coherence in semiconductors: Considerations for a spin-based solid state quantum computer architecture

We theoretically consider coherence times for spins in two quantum computer architectures, where the qubit is the spin of an electron bound to a P donor impurity in Si or within a GaAs quantum dot. We show that low temperature decoherence is dominated by spin-spin interactions, through spectral diffusion and dipolar flip-flop mechanisms. These contributions lead to 1-100 $\mu$s calculated spin coherence times for a wide range of parameters, much higher than former estimates based on $T_{2}^{*}$ measurements.Comment: Role of the dipolar interaction clarified; Included discussion on the approximations employed in the spectral diffusion calculation. Final version to appear in Phys. Rev.

Age-related qualitative shift in emotional behaviour : paradoxical findings after re-exposure of rats in the elevated-plus maze

Several variables, including age, are known to influence anxiety. Previous exposure to the elevated-plus maze (EPM) is known to modify emotional behaviour as retesting in the EPM at a standard age of 3 months increases open-arm avoidance and attenuates the effects of anxiolytic drugs. This study analysed whether similar results are obtained when older animals are subjected to these experimental paradigms. Overall, increasing age was associated with more signs of anxiety. Additionally, we observed a paradoxical behaviour pattern in aged-subjects that were re-exposed to the EPM, with mid-aged and old rats failing to display open arm avoidance (OAA) in the second trial; this qualitative shift in emotional behaviour was not associated with decreased locomotion. An examination of how age influences responsiveness to anxiolytic drugs, with or without previous maze experience, was also conducted. Midazolam (0.5 and 1 mg/kg) proved anxiolytic in maize-naive young animals; in marked contrast, in older animals midazolam at 1 mg/kg resulted in sedation but not anxiolyis. One trial tolerance to midazolam was evident in animals of both ages that were subjected to a second EPM trial; the latter phenomenon was apparently accentuated in older animals as they do not show open arm avoidance upon re-exposure to the EPM. These data suggest that the age-associated ‘resistance’ to anxiolytic drugs might be related to a qualitative shift in emotional behaviour

Methylation at the CpG island shore region upregulates Nr3c1 promoter activity after early-life stress

Early-life stress (ELS) induces long-lasting changes in gene expression conferring an increased risk for the development of stress-related mental disorders. Glucocorticoid receptors (GR) mediate the negative feedback actions of glucocorticoids (GC) in the paraventricular nucleus (PVN) of the hypothalamus and anterior pituitary and therefore play a key role in the regulation of the hypothalamic-pituitary-adrenal (HPA) axis and the endocrine response to stress. We here show that ELS programs the expression of the GR gene (Nr3c1) by site-specific hypermethylation at the CpG island (CGI) shore in hypothalamic neurons that produce corticotropin-releasing hormone (Crh), thus preventing Crh upregulation under conditions of chronic stress. CpGs mapping to the Nr3c1 CGI shore region are dynamically regulated by ELS and underpin methylation-sensitive control of this region's insulation-like function via Ying Yang 1 (YY1) binding. Our results provide new insight into how a genomic element integrates experience-dependent epigenetic programming of the composite proximal Nr3c1 promoter, and assigns an insulating role to the CGI shore.European Union Directorate General for Research & Innovation through the CRESCENDO Consortium (O.F.X.A. and D.S) and the NINA Initial Training Program (D.S. and O.F.X.A

Effect of an inhomogeneous external magnetic field on a quantum dot quantum computer

We calculate the effect of an inhomogeneous magnetic field, which is invariably present in an experimental environment, on the exchange energy of a double quantum dot artificial molecule, projected to be used as a 2-qubit quantum gate in the proposed quantum dot quantum computer. We use two different theoretical methods to calculate the Hilbert space structure in the presence of the inhomogeneous field: the Heitler-London method which is carried out analytically and the molecular orbital method which is done computationally. Within these approximations we show that the exchange energy J changes slowly when the coupled dots are subject to a magnetic field with a wide range of inhomogeneity, suggesting swap operations can be performed in such an environment as long as quantum error correction is applied to account for the Zeeman term. We also point out the quantum interference nature of this slow variation in exchange.Comment: 12 pages, 4 figures embedded in tex

Collective Decoherence of Nuclear Spin Clusters

The problem of dipole-dipole decoherence of nuclear spins is considered for strongly entangled spin cluster. Our results show that its dynamics can be described as the decoherence due to interaction with a composite bath consisting of fully correlated and uncorrelated parts. The correlated term causes the slower decay of coherence at larger times. The decoherence rate scales up as a square root of the number of spins giving the linear scaling of the resulting error. Our theory is consistent with recent experiment reported in decoherence of correlated spin clusters.Comment: 4 pages, 4 figure