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Numerous factors influence late-life depressive symptoms in adults, many not thoroughly characterized. We addressed whether genetic and environmental influences on depressive symptoms differed by age, sex, and physical illness.
The analysis sample included 24 436 twins aged 40–90 years drawn from the Interplay of Genes and Environment across Multiple Studies (IGEMS) Consortium. Biometric analyses tested age, sex, and physical illness moderation of genetic and environmental variance in depressive symptoms.
Women reported greater depressive symptoms than men. After age 60, there was an accelerating increase in depressive symptom scores with age, but this did not appreciably affect genetic and environmental variances. Overlap in genetic influences between physical illness and depressive symptoms was greater in men than in women. Additionally, in men extent of overlap was greater with worse physical illness (the genetic correlation ranged from near 0.00 for the least physical illness to nearly 0.60 with physical illness 2 s.d. above the mean). For men and women, the same environmental factors that influenced depressive symptoms also influenced physical illness.
Findings suggested that genetic factors play a larger part in the association between depressive symptoms and physical illness for men than for women. For both sexes, across all ages, physical illness may similarly trigger social and health limitations that contribute to depressive symptoms.
We describe the performance of the Boolardy Engineering Test Array, the prototype for the Australian Square Kilometre Array Pathfinder telescope. Boolardy Engineering Test Array is the first aperture synthesis radio telescope to use phased array feed technology, giving it the ability to electronically form up to nine dual-polarisation beams. We report the methods developed for forming and measuring the beams, and the adaptations that have been made to the traditional calibration and imaging procedures in order to allow BETA to function as a multi-beam aperture synthesis telescope. We describe the commissioning of the instrument and present details of Boolardy Engineering Test Array’s performance: sensitivity, beam characteristics, polarimetric properties, and image quality. We summarise the astronomical science that it has produced and draw lessons from operating Boolardy Engineering Test Array that will be relevant to the commissioning and operation of the final Australian Square Kilometre Array Path telescope.
PKS 1830–211 is the strongest known radio gravitational lens by almost an order of magnitude and has the potential to provide a measurement of H0, provided the lensing system can be parameterized. Attempts to identify optical counterparts, to measure redshifts, have so far proved unsuccessful and this has lead to radio and millimetre spectral line observations. We present our discovery of an absorption system at z = 0.19. A brief description is also made of our ATCA observations to measure the lensing time delay for this source.
We describe a space VLBI experiment involving an earth-orbiting satellite (SURFSAT) and simulated satellites, a space VLBI ground tracking station, an array of ground radio telescopes, and a space VLBI correlator. The purpose of this experiment was to provide as complete as possible an end-to-end simulation of space VLBI in preparation for the first space VLBI mission, VSOP, and in particular to test the most critical aspect of space VLBI, viz. the ability to generate a stable and accurate frequency standard (clock) for the orbiting VLBI element.
This paper describes the system architecture of a newly constructed radio telescope – the Boolardy engineering test array, which is a prototype of the Australian square kilometre array pathfinder telescope. Phased array feed technology is used to form multiple simultaneous beams per antenna, providing astronomers with unprecedented survey speed. The test array described here is a six-antenna interferometer, fitted with prototype signal processing hardware capable of forming at least nine dual-polarisation beams simultaneously, allowing several square degrees to be imaged in a single pointed observation. The main purpose of the test array is to develop beamforming and wide-field calibration methods for use with the full telescope, but it will also be capable of limited early science demonstrations.
Altered corticostriatothalamic encoding of reinforcement is a core feature of depression. Here we examine reinforcement learning in late-life depression in the theoretical framework of the vascular depression hypothesis. This hypothesis attributes the co-occurrence of late-life depression and poor executive control to prefrontal/cingulate disconnection by vascular lesions.
Our fMRI study compared 31 patients aged ⩾60 years with major depression to 16 controls. Using a computational model, we estimated neural and behavioral responses to reinforcement in an uncertain, changing environment (probabilistic reversal learning).
Poor executive control and depression each explained distinct variance in corticostriatothalamic response to unexpected rewards. Depression, but not poor executive control, predicted disrupted functional connectivity between the striatum and prefrontal cortex. White-matter hyperintensities predicted diminished corticostriatothalamic responses to reinforcement, but did not mediate effects of depression or executive control. In two independent samples, poor executive control predicted a failure to persist with rewarded actions, an effect distinct from depressive oversensitivity to punishment. The findings were unchanged in a subsample of participants with vascular disease. Results were robust to effects of confounders including psychiatric comorbidities, physical illness, depressive severity, and psychotropic exposure.
Contrary to the predictions of the vascular depression hypothesis, altered encoding of rewards in late-life depression is dissociable from impaired contingency learning associated with poor executive control. Functional connectivity and behavioral analyses point to a disruption of ascending mesostriatocortical reward signals in late-life depression and a failure of cortical contingency encoding in elderly with poor executive control.
Zinc Oxide crystals have historically been grown in hydrothermal autoclaves with a basic mineralizer; however, doubts have been raised about the quality of such crystals because they have often exhibited large x-ray rocking curve widths and low photoluminescence (PL) yield with large linewidths. Several ZnO crystals were grown hydrothermally and sliced parallel to the c-plane. This resulted in opposite surfaces (the C+ and C−) exhibiting pronounced chemical and mechanical differences. Different surface treatments were investigated and compared by PL both at room temperature and liquid helium temperatures, and by double axis X-ray rocking curve measurements. The high quality of hydrothermally-grown ZnO is substantiated by the narrow rocking curve widths and sharp PL peaks obtained. A critical factor in obtaining these results was found to be surface preparation.
The rice leaf roller, Cnaphalocrocis medinalis (Guenée), is a serious insect pest of rice with a strong migratory ability. Previous studies on the migration of C. medinalis were mostly carried out in tropical or subtropical regions, however, and what the pattern of seasonal movements this species exhibits in temperate regions (i.e. Northern China, where they cannot overwinter) remains unknown. Here we present data from an 11-year study of this species made by searchlight trapping on Beihuang Island (BH, 38°24′N; 120°55′E) in the centre of the Bohai Strait, which provides direct evidence that C. medinalis regularly migrates across this sea into northeastern agricultural region of China, and to take advantage of the abundant food resources there during the summer season. There was considerable seasonal variation in number of C. medinalis trapped on BH, and the migration period during 2003–2013 ranged from 72 to 122 days. Some females trapped in June and July showed a relatively higher proportion of mated and a degree of ovarian development suggesting that the migration of this species is not completely bound by the ‘oogenesis-flight syndrome’. These findings revealed a new route for C. medinalis movements to and from Northeastern China, which will help us develop more effective management strategies against this pest.
The genus Diorhabda (Coleoptera: Chrysomelidae) was recently revised, using morphological characters, into five tamarisk-feeding species, four of which have been used in the tamarisk (Tamarix spp.) biological control program in North America and are the subject of these studies. The taxonomic revision is here supported using molecular genetic and hybridization studies. Four Diorhabda species separated into five clades using cytochrome c oxidase subunit 1 sequence data with Diorhabda elongata separating into two clades. Amplified fragment length polymorphism (AFLP) analysis using genomic DNA revealed only four clades, which corresponded to the four morphospecies. Hybridization between the four species yielded viable eggs in F1 crosses but viability was significantly lower than achieved with intraspecific crosses. Crosses involving Diorhabda carinulata and the other three species resulted in low F2 egg viability, whereas crosses between D. elongata, Diorhabda sublineata and Diorhabda carinata resulted in > 40% F2 egg viability. Crosses between D. carinulata and the other three species resulted in high mortality of D. carinulata females due to genital mismatch. AFLP patterns combined with principal coordinates analysis enabled effective separation between D. elongata and D. sublineata, providing a method to measure genetic introgression in the field.
The Australian Square Kilometre Array Pathfinder (ASKAP) will give us an unprecedented opportunity to investigate the transient sky at radio wavelengths. In this paper we present VAST, an ASKAP survey for Variables and Slow Transients. VAST will exploit the wide-field survey capabilities of ASKAP to enable the discovery and investigation of variable and transient phenomena from the local to the cosmological, including flare stars, intermittent pulsars, X-ray binaries, magnetars, extreme scattering events, interstellar scintillation, radio supernovae, and orphan afterglows of gamma-ray bursts. In addition, it will allow us to probe unexplored regions of parameter space where new classes of transient sources may be detected. In this paper we review the known radio transient and variable populations and the current results from blind radio surveys. We outline a comprehensive program based on a multi-tiered survey strategy to characterise the radio transient sky through detection and monitoring of transient and variable sources on the ASKAP imaging timescales of 5 s and greater. We also present an analysis of the expected source populations that we will be able to detect with VAST.
The Parkes pulsar data archive currently provides access to 144044 data files obtained from observations carried out at the Parkes observatory since the year 1991. Around 105 files are from surveys of the sky, the remainder are observations of 775 individual pulsars and their corresponding calibration signals. Survey observations are included from the Parkes 70 cm and the Swinburne Intermediate Latitude surveys. Individual pulsar observations are included from young pulsar timing projects, the Parkes Pulsar Timing Array and from the PULSE@Parkes outreach program. The data files and access methods are compatible with Virtual Observatory protocols. This paper describes the data currently stored in the archive and presents ways in which these data can be searched and downloaded.
Fe bioavailability can be manipulated by the nutritional composition of a meal. Ascorbic acid and unidentified components of meat, fish and poultry, but particularly beef, all appear to enhance the absorption of non-haem Fe. The aim of the present study is to identify whether extracts of green-lipped mussels (GLM; Perna canaliculus) enhance non-haem Fe absorption in Caco-2 cells and to compare the effect with that of beef. Raw GLM and raw beef homogenates were digested in vitro with pepsin at pH 2, and pancreatin and bile salts at pH 7. Tracer 55Fe was used to measure cellular Fe uptake. Ascorbic acid was used as a positive control and egg albumin, exposed to the same in vitro digestion process, was used as a negative control. Caco-2 cell monolayers were incubated with treatments for 60 min. All values were standardised per μg of GLM, egg albumin, beef or ascorbic acid. The results showed that ascorbic acid enhanced non-haem Fe absorption to the highest degree. Beef and GLM digestates both significantly enhanced Fe absorption compared with egg albumin. In conclusion, GLM digestate significantly enhances non-haem Fe uptake in Caco-2 cells with a similar magnitude to that of beef.
Molecular beam deposition of quaterthiophene oligomer on a single crystal of potassium acid phtalate yields thin films exhibiting a novel supramolecular organisation which has been determined by a combined study of X-ray diffraction and polarized optical transmission measurements. In this structure consisting of stacks of tilted H aggregates, a commensurate ratio between the KAP substrate and the overgrown oligothiophene layer (quasi-epitaxial growth) is attained. The samples are optically extremely anisotropic, with the projection of the molecular axis on the substrate surface perfectly aligned along the b crystallographic axis. Using these novel structural data, the optical properties are interpreted within the framework of the transition density approach.
Wurzite GaN epilayers on sapphire substrates usually suffer from biaxial compressive strain due to the mismatches of the thermal expansion coefficients and the lattice constants between GaN layers and sapphire substrates. We have investigated the layer thickness effects on strain and transition energies by photoluminescence (PL), photoreflectance (PR) and X-ray diffraction (XRD). Samples used in this study are grown by hydride vapor phase epitaxy (HVPE) and have the layer thickness of 0.76, 2.6, 5.3 and 48 m. The PL and PR spectra showed the redshift of the transition energies with increasing layer thickness. This is attributed to strain-induced energy shift. The layer thickness dependence of strains is directly observed by XRD. The strain along the c -axis (εzz) decreased with increasing layer thickness. This indicates the strain is relaxed with layer thickness. From strain variation with layer thickness, we suggest that strain relaxation process is rapid at the initial stage of growth and becomes slower as the layer grows. The full width at half maximum (FWHM) of PL spectra and theta rocking curves decrease with increasing layer thickness. This indicates the crystal quality improves as the strain is reduced. Since the strain effect is very small at the layer thickness of 48 μm, we expect zero strain for thicker layers that can potentially be used as substrates for homoepitaxy.
Limited Reaction Processing (LRP) is a new technique which combines Rapid Thermal Processing (RTP) and Chemical Vapor Deposition (CVD). The added temperature control provided in rapid thermal processing enables the use of substrate temperature as a reaction switch. In addition, rapid thermal technology has been shown to provide other advantages for chemical vapor deposition of Si and III–V materials. Results are presented for group IV materials including epitaxial Si, SiGe alloys, SiO2 , and polysilicon. MOSFETs have been demonstrated and sensitive tests of interface quality are presented, paving the way for future bipolar transistor fabrication. III–V materials such as GaAs, AlGaAs, InGaAs have been grown. GaAs electron mobilities are the best reported for material grown using trimethylarsenic. As-ambient rapid thermal anneals of GaAs have also been performed.
High resolution photoluminescence for the identification of impurities and defects in semiconductors has emerged as a powerful technique. We review the technique with emphasis on GaAs realizing that it is applicable to many different semiconductor materials. The binding energies of thle ground state and of several low-lying excited states of the impurity centers are determined by studying the radiative transitions associated with excitons bound to neutral donors or acceptors. Recent developments in the studies of GaAs-AlGaAs multi-quantum-well (MQW) structures using high resolution photoluminescence are also reported. Variations of the energies of the various transitions in MQW structures as a function of well size are presented. Estimates of the interfacial quality in these heterostructures are made from line shape analysis.
Sintered ceramic, nonresorbable hydroxylapatite (HA) is a calcium phosphate biomaterial widely employed alone for augmentation or maintenance of the mandibular ridge and for filling alveolar bony defects. The small particles used for ridge augmentation or periodontal defects tend to scatter and the larger blocks used for extraction sockets don't fit well. Our recent studies suggest that these problems can be circumvented by composite plaster of Paris/HA implants. In addition to binding the HA particles, the plaster makes the implants easier to shape. Plaster is not only very biocompatible but may actually help prevent infection. It appears to act as a scaffold for incorporation of the HA particles into osseous tissue. In several days the plaster is resorbed but it is replaced at the same rate by infiltrating fibrovascular tissue; plaster definitely promotes the filling of osseous defects initially by connective tissue. This tissue not only maintains the form and integrity of the implant, but its vascular and collagen components promote healing and contribute to subsequent filling of the defects and approximation of the HA particles by new cancellous bone. These composite implants can be preformed on casts prior to surgery or tailored during the surgical procedure. Their use precludes the difficulties encountered when plaster alone is implanted (resorption) or when HA alone is used (particle scatter or nonpenetration of the material by host vascular and connective tissues). By having a resorbable component which permits penetration by fibrovascular tissue and a nonresorbable component which can act as a nidus for new cancellous bone formation, these composite alloplasts act like artificial bone. Their use to support a denture, or for immobilizing teeth and reducing pocket depths in advanced periodontal disease, gives better results than HA alone.
GaN films and GaN/AlGaN heterostructures have been gro wn by MBE. GaN films doped with varying levels of Mg indicate effective mass acceptor at low doping concentrations, as determined from strong photoluminescence emission at about 380 nm. As the Mg concentration is increased the photoluminescence emission line red shifts considerably, indicating the formation of Mg-related or induced complexes whose lifetimes are relatively short. GaN/AlGaN separate confinement heterostructures grown on sapphire show strong near ultraviolet stimulated emission at room temperature in a side-pumping configuration. The pumping threshold for stimulated emission at room temperature was found to be ∼90 kW/cm2. Initial GaN films grown on ZnO substrates show the A exciton in low temperature photoluminescence. ZnO is being considered for nitride growth because of its stacking order and close lattice match.