Context. Classical novae are eruptions on the surface of a white dwarf in a binary system. The material ejected from the white dwarf surface generally forms an axisymmetric shell of gas and dust ...around the system. The three-dimensional structure of these shells is difficult to untangle when viewed on the plane of the sky. In this work a geometrical model is developed to explain new observations of the 2015 nova V5668 Sagittarii. Aim. We aim to better understand the early evolution of classical nova shells in the context of the relationship between polarisation, photometry, and spectroscopy in the optical regime. To understand the ionisation structure in terms of the nova shell morphology and estimate the emission distribution directly following the light curve’s dust-dip. Methods. High-cadence optical polarimetry and spectroscopy observations of a nova are presented. The ejecta is modelled in terms of morpho-kinematics and photoionisation structure. Results. Initially observational results are presented, including broadband polarimetry and spectroscopy of V5668 Sgr nova during eruption. Variability over these observations provides clues towards the evolving structure of the nova shell. The position angle of the shell is derived from polarimetry, which is attributed to scattering from small dust grains. Shocks in the nova outflow are suggested in the photometry and the effect of these on the nova shell are illustrated with various physical diagnostics. Changes in density and temperature as the super soft source phase of the nova began are discussed. Gas densities are found to be of the order of 109 cm−3 for the nova in its auroral phase. The blackbody temperature of the central stellar system is estimated to be around 2.2 × 105 K at times coincident with the super soft source turn-on. It was found that the blend around 4640 Å commonly called “nitrogen flaring” is more naturally explained as flaring of the O II multiplet (V1) from 4638–4696 Å, i.e. “oxygen flaring”. Conclusions. V5668 Sgr (2015) was a remarkable nova of the DQ Her class. Changes in absolute polarimetric and spectroscopic multi-epoch observations lead to interpretations of physical characteristics of the nova’s evolving outflow. The high densities that were found early-on combined with knowledge of the system’s behaviour at other wavelengths and polarimetric measurements strongly suggest that the visual “cusps” are due to radiative shocks between fast and slow ejecta that destroy and create dust seed nuclei cyclically.
•Hippocampal subfields were automatically segmented with FreeSurfer.•Reliability of subfield measurements was assessed using three timepoints.•FreeSurfer preprocessing pipeline had excellent ...reliability.•Hippocampal subfields were not related to prospective PTSD symptoms.
The hippocampus plays a central role in post-traumatic stress disorder (PTSD) pathogenesis, and the majority of neuroimaging research on PTSD has studied the hippocampus in its entirety. Although extensive literature demonstrates changes in hippocampal volume are associated with PTSD, fewer studies have probed the relationship between symptoms and the hippocampus’ functionally and structurally distinct subfields. We utilized data from a longitudinal study examining post-trauma outcomes to determine whether hippocampal subfield volumes change post-trauma and whether specific subfields are significantly associated with, or prospectively related to, PTSD symptom severity. As a secondary aim, we leveraged our unique study design sample to also investigate reliability of hippocampal subfield volumes using both cross-sectional and longitudinal pipelines available in FreeSurfer v6.0.
Two-hundred and fifteen traumatically injured individuals were recruited from an urban Emergency Department. Two-weeks post-injury, participants underwent two consecutive days of neuroimaging (time 1: T1, and time 2: T2) with magnetic resonance imaging (MRI) and completed self-report assessments. Six-months later (time 3: T3), participants underwent an additional scan and were administered a structured interview assessing PTSD symptoms. First, we calculated reliability of hippocampal measurements at T1 and T2 (automatically segmented with FreeSurfer v6.0). We then examined the prospective (T1 subfields) and cross-sectional (T3 subfields) relationship between volumes and PTSD. Finally, we tested whether change in subfield volumes between T1 and T3 explained PTSD symptom variability.
After controlling for sex, age, and total brain volume, none of the subfield volumes (T1) were prospectively related to T3 PTSD symptoms nor were subfield volumes (T3) associated with current PTSD symptoms (T3). Tl – T2 reliability of all hippocampal subfields ranged from good to excellent (intraclass correlation coefficient (ICC) values > 0.83), with poorer reliability in the hippocampal fissure.
Our study was a novel examination of the prospective relationship between hippocampal subfield volumes in relation to PTSD in a large trauma-exposed urban sample. There was no significant relationship between subfield volumes and PTSD symptoms, however, we confirmed FreeSurfer v6.0 hippocampal subfield segmentation is reliable when applied to a traumatically-injured sample, using both cross-sectional and longitudinal analysis pipelines. Although hippocampal subfield volumes may be an important marker of individual variability in PTSD, findings are likely conditional on the timing of the measurements (e.g. acute or chronic post-trauma periods) and analysis strategy (e.g. cross-sectional or prospective).
This paper describes the results of atmospheric corrosion testing and of an examination of patina samples from Brisbane, Denmark, Sweden, France, USA and Austria. The aim was threefold: (1) to ...determine the structure of natural patinas and to relate their structure to their appearance in service and to the atmospheric corrosion of copper; (2) to understand why a brown rust coloured layer forms on the surface of some copper patinas; (3) to understand why some patinas are still black in colour despite being of significant age. During the atmospheric corrosion of copper, a two-layer patina forms on the copper surface. Cuprite is the initial corrosion product and cuprite is always the patina layer in contact with the copper. The growth laws describing patina formation indicate that the decreasing corrosion rate with increasing exposure time is due to the protective nature of the cuprite layer. The green patinas were typically characterised by an outer layer of brochantite, which forms as individual crystals on the surface of the cuprite layer, probably by a precipitation reaction from an aqueous surface layer on the cuprite layer. Natural patinas come in a variety of colours. The colour is controlled by the amount of the patina and its chemical composition. Thin patinas containing predominantly cuprite were black. If the patina was sufficiently thick, and the Fe/Cu ratio was low, then the patina was green, whereas if the Fe/Cu ratio was approximately 10
at%, then the patina is rust brown in colour. The iron was in solid solution in the brochantite, which might be designated as a (copper/iron) hydroxysulphate. In the brown patinas examined, the iron was distributed predominately in the outermost part of the patina.
Pneumonia is the leading cause of paediatric hospitalisation in Vietnam, placing a huge burden on the health care system. Pneumonia is also the main reason for antibiotic use in children. ...Unfortunately many hospital admissions for child pneumonia in Vietnam are unnecessary and inappropriate use of antibiotics is common, as in the rest of Asia, with little awareness of its adverse effects. We explored the value of an alternative approach that, instead of focusing on the identification of children with severe bacterial pneumonia, focuses on the identification of children with ‘unlikely bacterial pneumonia’ to improve patient care and rational antibiotic use. Implementing improved models of care require pragmatic management algorithms that are well validated, but it is ultimately dependent on financial structures, management support and evidence-based training of healthcare providers at all relevant levels. Apart from better case management, sustained reductions in the pneumonia disease burden also require increased emphasis on primary prevention.
Nance-Horan syndrome (NHS) is an X-linked disorder characterized by congenital cataracts, dental anomalies, dysmorphic features, and, in some cases, mental retardation. NHS has been mapped to a ...1.3-Mb interval on Xp22.13. We have confirmed the same localization in the original, extended Australian family with NHS and have identified protein-truncating mutations in a novel gene, which we have called
“NHS,” in five families. The
NHS gene encompasses ∼650 kb of genomic DNA, coding for a 1,630–amino acid putative nuclear protein.
NHS orthologs were found in other vertebrates, but no sequence similarity to known genes was identified. The murine developmental expression profile of the
NHS gene was studied using in situ hybridization and a mouse line containing a
lacZ reporter-gene insertion in the
Nhs locus. We found a complex pattern of temporally and spatially regulated expression, which, together with the pleiotropic features of NHS, suggests that this gene has key functions in the regulation of eye, tooth, brain, and craniofacial development.
Single-crystalline ZnO nanorod arrays with diameters of 60–120
nm and lengths of 2
μm have been grown epitaxially on GaN (0
0
1) by hydrothermal synthesis at 100
°C. The ZnO nanorods exhibit true ...epitaxial growth, in contrast to most of the previously reported methods, which involved the nucleation on a ZnO buffer layer pre-deposited on the substrate. An unprecedented high degree of
c-axis orientation is achieved in this hydrothermal epitaxial growth. The effect of growth conditions on the deposition of ZnO nanorods was systematically studied. We showed that by changing the molar ratio of the reactants, we can control the growth morphology of the ZnO nanorod arrays. The optimal conditions to produce high-density single-crystalline ZnO nanorods with
c-axis orientation have been identified. The mechanism affecting ZnO nanorod epitaxial nucleation and growth on GaN is discussed. The ZnO nanorods exhibited ultraviolet photoluminescence (PL) at 388
nm and the PL shows a decay lifetime of 58
ps.
The chemistry of copper patination Fitzgerald, K.P.; Nairn, J.; Atrens, A.
Corrosion science,
12/1998, Letnik:
40, Številka:
12
Journal Article
Recenzirano
The chemistry of copper patination was investigated by two series of experiments. The chemistry of an aqueous copper-sulphate solution was studied at concentrations and pH values near those predicted ...in an electrolyte on copper exposed to the atmosphere. The electrochemical reactions in an electrolyte in contact with cuprite were investigated in a reaction vessel which used cuprite powder in artificial rainwater to study the electrochemistry of the atmospheric corrosion and patination of copper. Typical sulphate concentrations in rainwater are sufficient to precipitate posnjakite (Cu
4SO
4 (OH)
62H
2O)), a possible precursor to brochantite, within an hour of wetting a cuprite surface. Brochantite (Cu
4SO
4 (OH)
6), the most commonly found copper salt in natural patinas is responsible for their green appearance. Precipitation of brochantite from the electrolyte resulted from an increase in pH due to the cathodic reduction of oxygen and an increase in cupric ion concentrations by cuprite oxidation.
The origin and evolution of surface microstructures in the GaAs layer grown on the Ge/Si1-xGex/Si substrate were studied. The characteristic surface microstructures are formed in pairs. By ...correlating the results from atomic force microscopy and cross-sectional transmission electron microscopy characterization, these paired surface microstructures are identified as {1 1 1} stacking faults that propagate at 54 deg with respect to the substrate surface. The stacking faults originate from the single-stepped GaAs/Ge heterointerface, as a consequence of in situ annealing of the Ge surface. The surface microstructure density becomes lower and the mean lateral size larger when the GaAs thickness is increased from 0.54 to 1.11 mum.
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