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We describe system verification tests and early science results from the pulsar processor (PTUSE) developed for the newly commissioned 64-dish SARAO MeerKAT radio telescope in South Africa. MeerKAT is a high-gain (${\sim}2.8\,\mbox{K Jy}^{-1}$) low-system temperature (${\sim}18\,\mbox{K at }20\,\mbox{cm}$) radio array that currently operates at 580–1 670 MHz and can produce tied-array beams suitable for pulsar observations. This paper presents results from the MeerTime Large Survey Project and commissioning tests with PTUSE. Highlights include observations of the double pulsar $\mbox{J}0737{-}3039\mbox{A}$, pulse profiles from 34 millisecond pulsars (MSPs) from a single 2.5-h observation of the Globular cluster Terzan 5, the rotation measure of Ter5O, a 420-sigma giant pulse from the Large Magellanic Cloud pulsar PSR $\mbox{J}0540{-}6919$, and nulling identified in the slow pulsar PSR J0633–2015. One of the key design specifications for MeerKAT was absolute timing errors of less than 5 ns using their novel precise time system. Our timing of two bright MSPs confirm that MeerKAT delivers exceptional timing. PSR $\mbox{J}2241{-}5236$ exhibits a jitter limit of $<4\,\mbox{ns h}^{-1}$ whilst timing of PSR $\mbox{J}1909{-}3744$ over almost 11 months yields an rms residual of 66 ns with only 4 min integrations. Our results confirm that the MeerKAT is an exceptional pulsar telescope. The array can be split into four separate sub-arrays to time over 1 000 pulsars per day and the future deployment of S-band (1 750–3 500 MHz) receivers will further enhance its capabilities.
Local structural and metabolic as well as inter-regional connectivity abnormalities have been implicated in the neuropathology of major depressive disorder (MDD). How local tissue properties affect intrinsic functional connectivity is, however, unclear. Using a cross-sectional, multi-modal imaging approach, we investigated the relationship between local cortical tissue abnormalities and intrinsic resting-state functional connectivity (RSFC) in MDD.
Method
A total of 20 MDD in-patients and 20 healthy controls underwent magnetic resonance imaging at 3 T for structural and functional imaging. Whole-brain cortical thickness was calculated and compared between groups. Regions with reduced cortical thickness defined seeds for subsequent whole-brain RSFC analyses. Contributions of structural tissue abnormalities on inter-regional RSFC were explicitly investigated.
Results
Lower cortical thickness was observed in MDD in the right dorsomedial prefrontal cortex (PFC), superior temporal gyrus/temporal pole, middle-posterior cingulate cortex, and dorsolateral PFC. No differences in local fractional amplitude of low-frequency fluctuations were observed. Lower thickness in patients' dorsomedial PFC further directly and selectively affected its RSFC with the precuneus, which was unaffected by symptom severity. No effects of cortical thickness in other regions showing abnormal thickness were observed to influence functional connectivity.
Conclusions
Abnormal cortical thickness in the dorsomedial PFC in MDD patients was observed to selectively and directly affect its intrinsic connectivity with the precuneus in MDD patients independent of depression severity, thereby marking a potential vulnerability for maladaptive mood regulation. Future studies should include an unmedicated sample and replicate findings using independent component analysis to test for morphometric effects on network integrity.
We summarize the status of a computer simulator for microlens planet surveys. The simulator generates synthetic light curves of microlensing events observed with specified networks of telescopes over specified periods of time. Particular attention is paid to models for sky brightness and seeing, calibrated by fitting to data from the OGLE survey and RoboNet observations in 2011. Time intervals during which events are observable are identified by accounting for positions of the Sun and the Moon, and other restrictions on telescope pointing. Simulated observations are then generated for an algorithm that adjusts target priorities in real time with the aim of maximizing planet detection zone area summed over all the available events. The exoplanet detection capability of observations was compared for several telescopes.
Las Cumbres Observatory Global Telescope Network (LCOGT) is currently building a new kind of general-purpose astronomical facility: a fully robotic network of telescopes of 2m, 1m and 0.4m apertures and homogeneous instrumentation. A pan-network approach to scheduling (rather than per individual telescope) offers redundancy in the event of poor weather or technical failure, as well as the ability to observe a target around the clock. Here we describe the network design and instrumentation under development, together with the main science programmes already being lead by LCOGT staff.
The human hookworm Necator americanus appears to have evolved a number of complementary strategies to overcome the host's haemostatic processes. These include the inhibition of blood coagulation, platelet aggregation and mediator release, and the secretion of fibrinogenolytic enzymes. These strategies presumably allow the parasite to establish the chronic infections so often documented in human populations.
We present the science case for ICE-T, the International Concordia Explorer Telescope, a double telescope optimized for ultra-high and ultra wide field optical time-series photometry fromDome C. ICE-T consists of two 60 cm 8°×8°-FOV Schmidt telescopes for Sloan g and i photometry and one independent 25 cm, solar, full-disk, Ca ii-K imagingtelescope on a single mount. ICE-T is therefore operable during night and day. A 28 cm narrow-field Maksutov spectrophotometric telescope for night-time aerosol measurements (TAVERN-SP) will beprovided by AWI early on and operated in parallel with IRAIT and later with ICE-T. The low scintillation noise and the long continuous darkness are among the unique properties for highprecision optical time-series photometry.
The WASP consortium is conducting an ultra-wide field survey of stars between 8–15 mag from both hemispheres. Our primary science goal is to detect extra-solar ‘hot-Jupiter’-type planets that eclipse (or transit) bright host stars and for which further detailed investigation will be possible. We summarize the design of the SuperWASP instruments and describe the first results from our northern station SW-N, sited in La Palma, Canary Islands. Our second station, which began operations this year, is located at the South African Astronomical Observatory. Between April and September, 2004, SW-N continuously observed ~6.7 million stars. The consortium's custom-written, fully automated data reduction pipeline has been used to process these data, and the information is now stored in the project archive, held by the Leicester database and archive service (LEDAS). We have applied a sophisticated, automated algorithm to identify the low-amplitude (~0.01 mag), brief (~few hours) signatures of transiting exoplanets. In addition, we have assessed each candidate in the light of all available catalogue information in order to reject data artefacts and astrophysical false positive detections. The highest priority candidates are currently being subjected to further observations in order to select the true planets. Once the exoplanets are confirmed, a host of exciting opportunities are open to us. In this paper, we describe two techniques that exploit the transits in order to detect other objects within the same system. The first involves determining precise epochs for a sequence of transit events in order to detect the small timing variations caused by the gravitational pull of other planets in the same system. The second method employs ultra-high precision photometry of the transits to detect the deviations caused by the presence of exoplanetary moons. Both of these techniques are capable of detecting objects the size of terrestrial planets.
We present first results from a coordinated multiwavelength study of the neutron star low-mass X-ray binary EXO 0748 676. Fast UV, X-ray, and optical data were obtained including both spectral and timing information. We discuss how this study allows us to probe the temperature distribution within the binary and hence the geometry and efficiency of X-ray irradiation.
Multivariate meta-analysis was performed on 39 studies of ventricular size in schizophrenia which used the ventricle:brain ratio (VBR). The size of the VBR was dependent both upon the date when studies were carried out (more recent studies showing a reduction in the difference between schizophrenics and controls), and upon the diagnostic criterion used in the studies. Methodological factors in study design seemed more important than the characteristics of the schizophrenic subjects, in determining the VBR. Our analysis suggests that there is a difference in VBR between schizophrenics and controls which would seem to be an indisputable characteristic of schizophrenia. However, the difference is smaller than has previously been thought, so that, although of undoubted theoretical interest in accounting for the aetiology of schizophrenia, it is probably too small to be of practical significance in diagnosis, or in the differentiation of subtypes.
In this study of 53 twin pregnancies, the plasma concentrations of the placental proteins, placental lactogen (hPL), and pregnancy-specific glycoprotein (SP1) were measured. Placental lactogen was found to be of more value than SP1 both in the detection of twins and in assessment of fetal growth. Serial measurement of either protein would seem to be more useful in assessment of fetal growth than single measurements. Preliminary studies of the less well known placental protein, PP5, in a small series of twin pregnancies indicate that it may also prove to be of clinical value in the detection and monitoring of twin pregnancies.
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