Extensive X-ray variability studies of NGC 7314 using long XMM-Newton observations

We present a detailed X-ray variability study of the low mass Active Galactic Nuclei (AGN) NGC 7314 using the two newly obtained XMM-Newton observations ($140$ and $130$ ks), together with two archival data sets of shorter duration ($45$ and $84$ ks). The relationship between the X-ray variability characteristics and other physical source properties (such as the black hole mass) are still relatively poorly defined, especially for low-mass AGN. We perform a new, fully analytical, power spectral density (PSD) model analysis method, which will be described in detail in a forthcoming paper, that takes into consideration the spectral distortions, caused by red-noise leak. We find that the PSD in the $0.5-10$ keV energy range, can be represented by a bending power-law with a bend around $6.7\times10^{-5}$ Hz, having a slope of $0.51$ and $1.99$ below and above the bend, respectively. Adding our bend time-scale estimate, to an already published ensemble of estimates from several AGN, supports the idea that the bend time-scale depends linearly only on the black hole mass and not on the bolometric luminosity. Moreover, we find that as the energy range increases, the PSD normalization increases and there is a hint that simultaneously the high frequency slope becomes steeper. Finally, the X-ray time-lag spectrum of NGC 7314 shows some very weak signatures of relativistic reflection, and the energy resolved time-lag spectrum, for frequencies around $3\times10^{-4}$ Hz, shows no signatures of X-ray reverberation. We show that the previous claim about ks time-delays in this source, is simply an artefact induced by the minuscule number of points entering during the time-lag estimation in the low frequency part of the time-lag spectrum (i.e. below $10^{-4}$ Hz).Comment: Accepted for publication in MNRAS. The paper is 21 pages long and contains 15 figures and 3 table

Towards Recyclable Insulation Materials for High Voltage Cables

The preferred material for modern extruded high voltage transmission cables is cross-linked polyethylene (XLPE). This material has excellent thermo-mechanical and dielectric properties, however it is not easily recycled at end of use, raising questions as to its long term sustainability [1]. Therefore research work at Southampton has sought to identify suitable recyclable alternatives to XLPE. Such candidate materials need to have low temperature flexibility and high temperature mechanical stability combined with a sufficiently high electrical breakdown strength

Finding a closest point in a lattice of Voronoi's first kind

We show that for those lattices of Voronoi's first kind with known obtuse superbasis, a closest lattice point can be computed in $O(n^4)$ operations where $n$ is the dimension of the lattice. To achieve this a series of relevant lattice vectors that converges to a closest lattice point is found. We show that the series converges after at most $n$ terms. Each vector in the series can be efficiently computed in $O(n^3)$ operations using an algorithm to compute a minimum cut in an undirected flow network

Raman Microprobe Analysis of Electrical Treeing in Silicone Rubber

Previous papers have identified Raman microprobe analysis as a useful tool in the chemical analysis of electrical trees and have successfully applied the technique to trees grown in polyethylene. This paper comprises a detailed spectroscopic study of electrical trees grown in silicone rubber. A selection of trees of varying fractal dimensions were exposed using cryogenic microtomy and then the individual tree channels were subjected to surface specific Raman microprobe analysis. It was found that although some trees show that few chemical changes have occurred, some trees (including some where complete breakdown has occurred) show evidence of the presence of silica and carbon, the latter possibly originating from the side groups of the polymer chain. After this, some of the samples were then analyzed using scanning electron microscopy (SEM) to provide an alternative method of analysis and to reinforce the conclusions made. Results are discussed in comparison to previously published results from a similar analysis on trees in polyethylene

Information Flow and Influence during Collective Search, Discussion, and Choice

If decision-relevant information is distributed among team members, the group is inclined to focus on shared information and to neglect unshared information, resulting often in suboptimal decisions. This classical finding is robust in experimental settings, in which the distribution of information is created artificially by an experimenter. The current paper looks at information sharing effects when access to information is not restricted, and decision makers are very familiar with the decision task. We analyzed archival search and discussion data obtained from business executives completing a personnel selection exercise. Information popularity in the population from which groups were composed predicted number of group members accessing items during information searches and whether the group discussed the items. The number of group members who accessed an item predicted whether information was repeated during discussion, and repetition predicted which items were included on an executive summary. Moreover, cognitively central group members were more influential than cognitively peripheral members. One implication is that collective decision making amplifies what is commonly known at the expense of disseminating what is not.Information Sharing, Cognitive Centrality, Group Decision Making, Collective Choice, Archival Data

The Correlation Between Maternal Postpartum Depression and Child Psychopathology

Background: Postpartum depression (PPD) is a phenomenon that affects nearly 10-15% of pregnancies in the US. It is characterized by depressed mood or anhedonia and lasting for more than 2 weeks. PPD changes how moms interact with family members and child-rearing behavior. Depression is a phenomenon that is also known to affect the psychopathology of children. However, the specifics of how postpartum depression impacts children remains controversial. Many studies do not control for major depressive disorder which makes it difficult to disentangle the impact depression has within the first year of life. Furthermore, other PPD risk factors may be confounding the effect PPD has on child psychopathology. Aims: Identify risk factors for PPD in the areas of: A) birth outcomes, B) prenatal behaviors, C) maternal mental health, and D) SES Identify associations between PPD and child psychopathology Identify associations between relevant child psychopathology (identified in aim 2) and select PPD risk factors (identified in aim 1). Determine the GxE interaction for select birth outcomes and select child psychopathology. Methods: This is a retrospective cohort study from the Virginia Twin Study of Adolescent Behavioral Development (VTSABD). There were 855 moms included for analysis with 7.46% reporting PPD and 1710 relevant twin pairs. Results: PPD was associated with: A) child fretting and staying with other family members, B) drinking alcohol during pregnancy, C) major depressive disorder and panic disorder, and, D) marital satisfaction PPD was associated with ADHD and conduct disorder with the main driver being ADHD. ADHD was linked to: A)fretting and staying with other family members, B) drinking alcohol at least once per week C) postpartum depression and alcoholism, and D) low income and low familial education Twin Correlations reveal that fretting and ADHD are driven by genetics. Staying with other family members is driven by the environment. PPD increases the genetic heritability of children’s ADHD. Discussion: Having postpartum depression increases the odds that children have ADHD by increasing the genetic variance

Electrical Treeing in Silicone Rubber

Electrical treeing has been widely studied in a range of polymeric materials. In these investigations, the morphology and PD patterns associated with the growth of electrical trees in a model transparent silicone rubber were investigated using a new system recently developed at Southampton. With increasing voltage the trees became more complex in appearance but nevertheless grow more rapidly. As the tree evolves the PD pattern becomes more intense which may provide a method of monitoring the extent of treeing in opaque samples. Raman studies indicate that treeing and breakdown channels are hollow, carbonaceous entities, a finding consistent with other studies