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The Square Kilometre Array will be an amazing instrument for pulsar astronomy. While the full SKA will be sensitive enough to detect all pulsars in the Galaxy visible from Earth, already with SKA1, pulsar searches will discover enough pulsars to increase the currently known population by a factor of four, no doubt including a range of amazing unknown sources. Real time processing is needed to deal with the 60 PB of pulsar search data collected per day, using a signal processing pipeline required to perform more than 10 POps. Here we present the suggested design of the pulsar search engine for the SKA and discuss challenges and solutions to the pulsar search venture.
W49 A is a star-forming region (SFR) found in the constellation of Aquila. It contains 3 active regions: W49 North (W49 N), W49 South West (W49 SW) and W49 South (W49 S). We present preliminary results from two epochs (e-)MERLIN observations of all ground-state OH masers towards the star-forming region (SFR) complex W49 A. The first epoch of observations was done in full-polarization mode with MERLIN in 2005 while the second epoch was obtained only in dual circular polarization during the test observations of the upgraded e-MERLIN in 2013. The overall maser spatial distributions in both epochs are in good agreement. We found several new high velocity maser features up to +34 km s−1 and −28 km s−1. The magnetic field strengths are between 1.1 to 10.8 mG. All three sources show evidence of magnetic field reversal.
We present the results from the Australian Long Baseline Array (LBA) observations of the ground- and excited-state OH masers at high resolutions towards the massive star-forming region G351.417+0.645 in 2012. We obtain the most accurate spatial gradient of magnetic fields at ground state transitions and verify the reliability of magnetic field strengths measured from previous lower resolution observations. In comparison with previous LBA observations in 2001 at 6.0 GHz, we identified several matched Zeeman pairs. We found that the OH maser features have no significant change of magnetic field strengths and directions with small internal proper motions, implying quite stable physical conditions. Additionally, we found that 1665- and 6035-MHz OH maser features reveal the same trend of reversal of magnetic fields. Moreover, we also analyzed the physical conditions at different locations from the coincidence of different OH maser transitions based on current OH maser models.
Our understanding of the complex relationship between schizophrenia symptomatology and etiological factors can be improved by studying brain-based correlates of schizophrenia. Research showed that impairments in value processing and executive functioning, which have been associated with prefrontal brain areas [particularly the medial orbitofrontal cortex (MOFC)], are linked to negative symptoms. Here we tested the hypothesis that MOFC thickness is associated with negative symptom severity.
This study included 1985 individuals with schizophrenia from 17 research groups around the world contributing to the ENIGMA Schizophrenia Working Group. Cortical thickness values were obtained from T1-weighted structural brain scans using FreeSurfer. A meta-analysis across sites was conducted over effect sizes from a model predicting cortical thickness by negative symptom score (harmonized Scale for the Assessment of Negative Symptoms or Positive and Negative Syndrome Scale scores).
Meta-analytical results showed that left, but not right, MOFC thickness was significantly associated with negative symptom severity (βstd = −0.075; p = 0.019) after accounting for age, gender, and site. This effect remained significant (p = 0.036) in a model including overall illness severity. Covarying for duration of illness, age of onset, antipsychotic medication or handedness weakened the association of negative symptoms with left MOFC thickness. As part of a secondary analysis including 10 other prefrontal regions further associations in the left lateral orbitofrontal gyrus and pars opercularis emerged.
Using an unusually large cohort and a meta-analytical approach, our findings point towards a link between prefrontal thinning and negative symptom severity in schizophrenia. This finding provides further insight into the relationship between structural brain abnormalities and negative symptoms in schizophrenia.
While trauma-focused cognitive–behavioral therapy (TF-CBT) is the ‘gold standard’ treatment for pediatric post-traumatic stress disorder (PTSD), little is known about the neural mechanisms by which TF-CBT produces clinical benefit. Here, we test the hypothesis that PTSD symptom reduction during TF-CBT among adolescent girls with PTSD is associated with changes in patterns of brain functional connectivity (FC) with the amygdala during cognitive reappraisal.
Adolescent girls with PTSD related to physical or sexual assault (n = 34) were enrolled in TF-CBT, delivered in an approximately 12-session format, in an open trial. Before and after treatment, they were engaged in a cognitive reappraisal task, probing neural mechanisms of explicit emotion regulation, during 3 T functional magnetic resonance imaging.
Among adolescent girls completing TF-CBT with usable pre- and post-treatment scans (n = 20), improvements in self-reported emotion from pre- to post-treatment were positively related to improvements in PTSD symptoms. Adolescent girls with greater post-treatment symptom reduction were also able to suppress amygdala–insula FC while re-appraising, which was not evident in girls with less symptom reduction. Pre- to post-treatment changes in right amygdala to left insula FC that scaled with PTSD symptom reduction also scaled with improvements in emotion regulation.
These preliminary results suggest the neurocircuitry mechanisms through which TF-CBT produces clinical outcomes, providing putative brain targets for augmenting TF-CBT response.
We developed a syndromic surveillance (SyS) concept using emergency dispatch, ambulance and emergency-department data from different European countries. Based on an inventory of sub-national emergency data availability in 12 countries, we propose framework definitions for specific syndromes and a SyS system design. We tested the concept by retrospectively applying cumulative sum and spatio-temporal cluster analyses for the detection of local gastrointestinal outbreaks in four countries and comparing the results with notifiable disease reporting. Routine emergency data was available daily and electronically in 11 regions, following a common structure. We identified two gastrointestinal outbreaks in two countries; one was confirmed as a norovirus outbreak. We detected 1/147 notified outbreaks. Emergency-care data-based SyS can supplement local surveillance with near real-time information on gastrointestinal patients, especially in special circumstances, e.g. foreign tourists. It most likely cannot detect the majority of local gastrointestinal outbreaks with few, mild or dispersed cases.
Radio pulsars in relativistic binary systems are unique tools to study the curved space-time around massive compact objects. The discovery of a pulsar closely orbiting the super-massive black hole at the centre of our Galaxy, Sgr A⋆, would provide a superb test-bed for gravitational physics. To date, the absence of any radio pulsar discoveries within a few arc minutes of Sgr A⋆ has been explained by one principal factor: extreme scattering of radio waves caused by inhomogeneities in the ionized component of the interstellar medium in the central 100 pc around Sgr A⋆. Scattering, which causes temporal broadening of pulses, can only be mitigated by observing at higher frequencies. Here we describe recent searches of the Galactic centre region performed at a frequency of 18.95 GHz with the Effelsberg radio telescope.
Within the Herschel key project “The Warm And Dense ISM” (WADI) we systematically observe
a number of prominent photon-dominated regions (PDRs) to measure the impact of varying UV
fields on the energy balance, the chemical and dynamical structure of heated molecular
In this report two different aspects in the development of AlGaN/GaN power amplifiers will be discussed. In the first part of this paper we report on the optimization of the Ti/Al/Ni/Au metallization scheme on a doped AlGaN/GaN FET structure. By a systematic investigation we were able to reduce the contact resistance to 0.2 ωmm (7.3×10×7ωcm2). The Al/Ti thickness ratio for this contact was 6, which according to the Al-Ti binary phase diagram, does not result in excess Ti which should react with nitrogen in the AlGaN layer to render the surface heavily doped. Preliminary results on Schottky contacts indicate an improvement in the reverse leakage current if a RIE oxygen plasma in combination with a NH4OH dip is performed prior to metallization.
Coplanar waveguides on AlN are discussed in the second part of this paper. These transmission lines can be used in AlGaN/GaN power amplifiers if no via-hole technology is available or if a hybrid solution is pursued. The signal line should have a large metal cross- sectional area (> 5 × 50 [.proportional]m2) in order to carry enough current in the output stage of an amplifier. It is shown that CPWs with large dimensions show non-quasi TEM behavior related to propagation of parallel plate modes.
Epitaxial PbTiO3 thin films have been grown on single-crystal MgO (100) substrates using metalorganic chemical vapor deposition technique. The energy gap was determined from optical absorption data to be Eg= 3,425 eV. Secondary ion mass spectrometry data showed uniform distribution of Pb, Ti and O atoms with no traces of carbon contamination. Atomic force microscopy studies showed different surface morphology for different film growth rates. In-situ X-ray diffraction data indicate that the tetragonal-to-cubic structural phase transition occurs at about 500–520°C. Above 750 °C the films exhibit multi-phase character, the textured PbTiO3 phase co-existing with a polycrystalline Pb2Ti2O6 structure and a possible Mg-containing impurity phase.
Application of excimer laser crystallization of Amorphous silicon (a-Si) has
introduced a new, interesting potential technology for the fabrication of
polycrystalline (poly-Si) thin film transistors. We are currently studying
polycrystalline Si1−xGex thin films in order to
determine whether this material can lead to improved electrical properties
or to better processing requirements when compared with polycrystalline Si
films. In this work we analyze by RBS, TEM, Raman spectroscopy and surface
reflectance, the structure of thin Amorphous Si1−xGex
films after irradiation with a XeCl excimer laser. The Amorphous SiGe films
were prepared by evaporation of Si and Ge onto oxidized Si substrates using
an electron gun in vaccum. The effects of laser energy fluence during
irradiation are investigated. The Amorphous to crystalline transition is
followed by in-situ measurement of time-resolved reflectivity.
Organic chromophores have been exploited for a wide range of discrete optical and electronic functions as well as a growing number of combined opto-electronic functions. We are pursuing development of organic and polymer materials for a range of applications that require properties including liquid crystallinity, second order optical nonlinearity, photorefractivity and, more recently, special nonlinear optical behavior involving molecular chirality.
The molecular orientation within a surface liquid crystalline layer made up of semifluorinated side-groups [-CO-(CH2)x−x-(CF2)yF] (SF groups) attached to the isoprene block of a styrene-isoprene diblock copolymer was determined by analyzing the partial electron yield Cedge NEXAFS signal. The results show that in contrast to the bulk, where the SF groups lie parallel to the diblock copolymer lamellae and thus parallel to the surface, the surface SF groups make an average angle with the surface normal of between 29 and 46° depending on x and y.
Following up on our previous low-resolution studies (Beuther et al.
2000; Mookerjea et al. 2006) in the nearby star forming region
Cepheus B, we try to understand photo-induced chemistry of the
photon dominated regions (PDRs) using the higher resolution data
observed with the IRAM 30 m telescope at Pico Veleta. The aim of our
study is to resolve the temperature, chemical, and excitation
structure of the transition zone from the H ii region to the
dense molecular cloud in a PDR which is subject only to moderately
strong UV fields. We study two cuts running through the interfaces
into the main cloud and thus allow to trace several interface
regions. Particularly, we select two positions at the interface for
a more detailed study. The studied frequency ranges from 85 GHz to
272 GHz and includes 21 transitions of 11 molecules such as HCN,
HCO+, CN, CS, CCH, and CCS. Combined with the low – J CO maps
in this region (Ungerechts et al. 2000), we calculate the
integrated intensity distribution along the cuts and line ratios
between different tracers and transitions. H2 column density
along the cuts has been estimated under the Local Thermodynamic
Equilibrium (LTE) assumption. The integrated line intensities
present nice changes from the H ii region into the molecular
clouds. There is an enhancement of all the tracers at the two
We report our recent progress on extragalactic spectroscopic and continuum observations,
including HCN(J=1–0), HCO+(J=1–0), and CN(N=1–0) imaging surveys
of local Seyfert and starburst galaxies
using the Nobeyama Millimeter Array,
high-J CO observations (J=3–2 observations
using the Atacama Submillimeter Telescope Experiment (ASTE)
and J=2–1 observations with the Submillimeter Array) of galaxies,
and λ 1.1 mm continuum observations of high-z violent starburst galaxies
using the bolometer camera AzTEC mounted on ASTE.
Observations using the HIFI and PACS instruments aboard the Herschel
satellite provide a unique way to study the chemical inventory,
the dynamics, and the energy balance in dense interstellar clouds heated by
UV radiation. We propose a comprehensive observing program to reveal
the details of the interaction of massive young stars with their
parental molecular clouds.