Intelligent search for distributed information sources using heterogeneous neural networks

As the number and diversity of distributed information sources on the Internet exponentially increase, various search services are developed to help the users to locate relevant information. But they still exist some drawbacks such as the difficulty of mathematically modeling retrieval process, the lack of adaptivity and the indiscrimination of search. This paper shows how heteroge-neous neural networks can be used in the design of an intelligent distributed in-formation retrieval (DIR) system. In particular, three typical neural network models - Kohoren's SOFM Network, Hopfield Network, and Feed Forward Network with Back Propagation algorithm are introduced to overcome the above drawbacks in current research of DIR by using their unique properties. This preliminary investigation suggests that Neural Networks are useful tools for intelligent search for distributed information sources

A Sino-German λ\lambda6\ cm polarization survey of the Galactic plane VI. Discovery of supernova remnants G178.2-4.2 and G25.1-2.3

Supernova remnants (SNRs) were often discovered in radio surveys of the Galactic plane. Because of the surface-brightness limit of previous surveys, more faint or confused SNRs await discovery. The Sino-German $\lambda$6\ cm Galactic plane survey is a sensitive survey with the potential to detect new low surface-brightness SNRs. We want to identify new SNRs from the $\lambda$6\ cm survey map of the Galactic plane. We searched for new shell-like objects in the $\lambda$6\ cm survey maps, and studied their radio emission, polarization, and spectra using the $\lambda$6\ cm maps together with the $\lambda$11\ cm and $\lambda$21\ cm Effelsberg observations. Extended polarized objects with non-thermal spectra were identified as SNRs. We have discovered two new, large, faint SNRs, G178.2-4.2 and G25.1-2.3, both of which show shell structure. G178.2-4.2 has a size of 72 arcmin x 62 arcmin with strongly polarized emission being detected along its northern shell. The spectrum of G178.2-4.2 is non-thermal, with an integrated spectral index of $\alpha = -0.48\pm0.13$. Its surface brightness is $\Sigma_{1 GHz} = 7.2 x 10^{-23}{Wm^{-2} Hz^{-1} sr^{-1}}$, which makes G178.2-4.2 the second faintest known Galactic SNR. G25.1-2.3 is revealed by its strong southern shell which has a size of 80 arcmin x 30\arcmin. It has a non-thermal radio spectrum with a spectral index of $\alpha = -0.49\pm0.13$. Two new large shell-type SNRs have been detected at $\lambda$6\ cm in an area of 2200 deg^2 along the the Galactic plane. This demonstrates that more large and faint SNRs exist, but are very difficult to detect.Comment: 8 pages, 8 figures, accepted by Astronomy and Astrophysics. For the version with high resolution figures, please go to http://zmtt.bao.ac.cn/6cm/papers/2newSNR.pd

New 6cm and 11cm observations of the supernova remnant CTA 1

(Abridged) We conducted new 6cm and 11cm observations of CTA 1 using the Urumqi 25-m and Effelsberg 100-m telescopes. Data at other wavelengths were included to investigate the spectrum and polarisation properties. We obtained new total intensity and polarisation maps at 6cm and 11cm with angular resolutions of 9.5 arcmin and 4.4 arcmin, respectively. We derived a spectral index of alpha=-0.63+/-0.05 based on the integrated flux densities at 408 MHz, 1420 MHz, 2639 MHz, and 4800 MHz. The spectral index map calculated from data at the four frequencies shows a clear steepening of the spectrum from the strong shell emission towards the north-western breakout region with weak diffuse emission. The decrease of the spectral index is up to about 0.3. The RM map derived from polarisation data at 6cm and 11cm shows a sharp transition between positive RMs in the north-eastern and negative RMs in the south-western part of the SNR. We note a corresponding RM pattern of extragalactic sources and propose the existence of a large-diameter Faraday screen in front of CTA 1, which covers the north-eastern part of the SNR. The RM of the Faraday screen is estimated to be about +45 rad/m2. A RM structure function of CTA 1 indicates a very regular magnetic field within the Faraday screen, which is larger than about 2.7 microG in case of 500 pc distance.Comment: 9 pages, 12 figures, minor changes, accepted for publication in A&

Evaluation of a Bayesian inference network for ligand-based virtual screening

Background Bayesian inference networks enable the computation of the probability that an event will occur. They have been used previously to rank textual documents in order of decreasing relevance to a user-defined query. Here, we modify the approach to enable a Bayesian inference network to be used for chemical similarity searching, where a database is ranked in order of decreasing probability of bioactivity. Results Bayesian inference networks were implemented using two different types of network and four different types of belief function. Experiments with the MDDR and WOMBAT databases show that a Bayesian inference network can be used to provide effective ligand-based screening, especially when the active molecules being sought have a high degree of structural homogeneity; in such cases, the network substantially out-performs a conventional, Tanimoto-based similarity searching system. However, the effectiveness of the network is much less when structurally heterogeneous sets of actives are being sought. Conclusion A Bayesian inference network provides an interesting alternative to existing tools for ligand-based virtual screening

XMMU J0541.8-6659, a new supernova remnant in the Large Magellanic Cloud

The high sensitivity of the XMM-Newton instrumentation offers the opportunity to study faint and extended sources in the Milky Way and nearby galaxies such as the Large Magellanic Cloud (LMC) in detail. The ROSAT PSPC survey of the LMC has revealed more than 700 X-ray sources, among which there are 46 supernova remnants (SNRs) and candidates. We have observed the field around one of the most promising SNR candidates in the ROSAT PSPC catalogue, labelled [HP99] 456 with XMM-Newton, to determine its nature. We investigated the XMM-Newton data along with new radio-continuum, near infrared and optical data. In particular, spectral and morphological studies of the X-ray and radio data were performed. The X-ray images obtained in different energy bands reveal two different structures. Below 1.0 keV the X-ray emission shows the shell-like morphology of an SNR with a diameter of ~73 pc, one of the largest known in the LMC. For its thermal spectrum we estimate an electron temperature of (0.49 +/- 0.12)keV assuming non-equilibrium ionisation. The X-ray images above 1.0 keV reveal a less extended source within the SNR emission, located ~1' west of the centre of the SNR and coincident with bright point sources detected in radio-continuum. This hard component has an extent of 0.9' (i.e. ~13 pc at a distance of ~50 kpc) and a non-thermal spectrum. The hard source coincides in position with the ROSAT source [HP99] 456 and shows an indication for substructure. We firmly identify a new SNR in the LMC with a shell-like morphology and a thermal spectrum. Assuming the SNR to be in the Sedov phase yields an age of ~23 kyr. We explore possible associations of the hard non-thermal emitting component with a pulsar wind nebula (PWN) or background active galactic nuclei (AGN).Comment: 8 pages, 7 figures, accepted for publication in Astronomy and Astrophysic

Absence of Replication-Competent Lentivirus in the Clinic: Analysis of Infused T Cell Products

Exposure to replication-competent lentivirus (RCL) is a theoretical safety concern for individuals treated with lentiviral gene therapy. For certain ex vivo gene therapy applications, including cancer immunotherapy trials, RCL detection assays are used to screen the vector product as well as the vector-transduced cells. In this study, we reviewed T cell products screened for RCL using methodology developed in the National Gene Vector Biorepository. All trials utilized third-generation lentiviral vectors produced by transient transfection. Samples from 26 clinical trials totaling 460 transduced cell products from 375 subjects were evaluated. All cell products were negative for RCL. A total of 296 of the clinical trial participants were screened for RCL at least 1 month after infusion of the cell product. No research subject has shown evidence of RCL infection. These findings provide further evidence attesting to the safety of third-generation lentiviral vectors and that testing T cell products for RCL does not provide added value to screening the lentiviral vector product

A high-resolution radio survey of the Vela supernova remnant

This paper presents a high-resolution radio continuum (843 MHz) survey of the Vela supernova remnant. The contrast between the structures in the central pulsar-powered nebula of the remnant and the synchrotron radiation shell allows the remnant to be identified morphologically as a member of the composite class. The data are the first of a composite remnant at spatial scales comparable with those available for the Cygnus Loop and the Crab Nebula, and make possible a comparison of radio, optical and soft X-ray emission from the resolved shell filaments. The survey, made with the Molonglo Observatory Synthesis Telescope, covers an area of 50 square degrees at a resolution of 43'' x 60'', while imaging structures on scales up to 30'.Comment: 18 pages, 7 jpg figures (version with ps figures at http://astro.berkeley.edu/~dbock/papers/); AJ, in pres

All-sky Galactic radiation at 45 MHz and spectral index between 45 and 408 MHz

Aims: We study the Galactic large-scale synchrotron emission by generating a reliable all-sky spectral index map and temperature map at 45 MHz. Methods: We use our observations, the published all-sky map at 408 MHz, and a bibliographical compilation to produce a map corrected for zero-level offset and extragalactic contribution. Results: We present full sky maps of the Galactic emission at 45 MHz and the Galactic spectral index between 45 and 408 MHz with an angular resolution of 5\degs. The spectral index varies between 2.1 and 2.7, reaching values below 2.5 at low latitude because of thermal free-free absorption and its maximum in the zone next to the Northern Spur.Comment: A&A accepte

A Sino-German λ\lambda6\ cm polarization survey of the Galactic plane. V. Large supernova remnants

Observations of large supernova remnants (SNRs) at high frequencies are rare, but provide valuable information about their physical properties. The total intensity and polarization properties of 16 large SNRs in the Galactic plane were investigated based on observations of the Urumqi $\lambda$6\ cm polarization survey of the Galactic plane with an angular resolution of 9\farcm5. We extracted total intensity and linear polarization maps of large SNRs from the Urumqi $\lambda$6\ cm survey, obtained their integrated flux densities, and derived the radio spectra in context with previously published flux densities at various frequencies. In particular, Effelsberg $\lambda$11\ cm and $\lambda$21\ cm survey data were used for calculating integrated flux densities. The $\lambda$6\ cm polarization data also delineate the magnetic field structures of the SNRs. We present the first total intensity maps at $\lambda$6\ cm for SNRs G106.3+2.7, G114.3+0.3, G116.5+1.1, G166.0+4.3 (VRO 42.05.01), G205.5+0.5 (Monoceros Nebula) and G206.9+2.3 (PKS 0646+06) and the first polarization measurements at $\lambda$6\ cm for SNRs G82.2+5.3 (W63), G106.3+2.7, G114.3+0.3, G116.5+1.1, G166.0+4.3 (VRO 42.05.01), G205.5+0.5 (Monoceros Nebula) and G206.9+2.3 (PKS 0646+06). Most of the newly derived integrated radio spectra are consistent with previous results. The new flux densities obtained from the Urumqi $\lambda$6\ cm, Effelsberg $\lambda$11\ cm and $\lambda$21\ cm surveys are crucial to determine the spectra of SNR G65.1+0.6, G69.0+2.7 (CTB 80), G93.7-0.2 and G114.3+0.3. We find that G192.8$-$1.1 (PKS 0607+17) consists of background sources, \ion{H}{II} regions and the extended diffuse emission of thermal nature, and conclude that G192.8$-$1.1 is not a SNR.Comment: 15 pages, 10 figures, accepted by A&\amp;A. Language improved. For the version with high resolution figures, please go to: http://zmtt.bao.ac.cn/6cm/paper/gxy_largeSNR.pd

Protecting eyewitness evidence: Examining the efficacy of a self-administered interview tool

Given the crucial role of eyewitness evidence, statements should be obtained as soon as possible after an incident. This is not always achieved due to demands on police resources. Two studies trace the development of a new tool, the Self-Administered Interview (SAI), designed to elicit a comprehensive initial statement. In Study 1, SAI participants reported more correct details than participants who provided a free recall account, and performed at the same level as participants given a Cognitive Interview. In Study 2, participants viewed a simulated crime and half recorded their statement using the SAI. After a delay of 1 week, all participants completed a free recall test. SAI participants recalled more correct details in the delayed recall task than control participants