Disambiguation strategies for cross-language information retrieval

This paper gives an overview of tools and methods for Cross-Language Information Retrieval (CLIR) that are developed within the Twenty-One project. The tools and methods are evaluated with the TREC CLIR task document collection using Dutch queries on the English document base. The main issue addressed here is an evaluation of two approaches to disambiguation. The underlying question is whether a lot of effort should be put in finding the correct translation for each query term before searching, or whether searching with more than one possible translation leads to better results? The experimental study suggests that the quality of search methods is more important than the quality of disambiguation methods. Good retrieval methods are able to disambiguate translated queries implicitly during searching

High-Redshift Superclustering of QSO Absorption Line Systems on 100 Mpc Scales

We have analyzed the clustering of C IV absorption line systems in an extensive new catalog of heavy element QSO absorbers. The catalog permits exploration of clustering over a large range in both scale (from about 1 to over 300 Mpc) and redshift (z from 1.2 to 4.5). We find significant evidence (5.0 sigma) that C IV absorbers are clustered on comoving scales of 100 Mpc and less --- similar to the size of voids and walls found in galaxy redshift surveys of the local universe --- with a mean correlation function $\xi = 0.42 \pm 0.10$ over these scales. We find, on these scales, that the mean correlation function at low (z=1.7), medium (z=2.4), and high redshift (z=3.0) is $\xi=0.40 \pm 0.17$, $0.32 \pm 0.14$, and $0.72 \pm 0.25$, respectively. Thus, the superclustering is present even at high redshift; furthermore, it does not appear that the superclustering scale, in comoving coordinates, has changed significantly since then. We find 7 QSOs with rich groups of absorbers (potential superclusters) that account for a significant portion of the clustering signal, with 2 at redshift $z\sim 2.8$. We find that the superclustering is just as evident if we take $q_0=0.1$ instead of 0.5; however, the inferred scale of clustering is then 240 Mpc , which is larger than the largest scales of clustering known at present. This discrepancy may be indicative of a larger value of $q_0$, and hence $\Omega_0$. The evolution of the correlation function on 50 Mpc scales is consistent with that expected in cosmologies with density parameter ranging from $\Omega_0 =$ 0.1 to 1. Finally, we find no evidence for clustering on scales greater than 100 Mpc ($q_0=0.5$) or 240 Mpc ($q_0=0.1$).Comment: 16 LaTeX pages with 3 encapsulated Postscript figures included, uses AASTeX (v. 4.0) available at ftp://ftp.aas.org/pubs/ , to appear in The Astrophysical Journal Letter

Alternative Adaptive Filter Structures for Improved Radio Frequency Interference Cancellation in Radio Astronomy

In radio astronomy, reference signals from auxiliary antennas that receive only the radio frequency interference (RFI) can be modified to model the RFI environment at the astronomy receivers. The RFI can then be canceled from the astronomy signal paths. However, astronomers typically only require signal statistics. If the RFI statistics are changing slowly, the cancellation can be applied to the signal correlations at a much lower rate than is required for standard adaptive filters. In this paper we describe five canceler setups; precorrelation and postcorrelation cancelers that use one or two reference signals in different ways. The theoretical residual RFI and added noise levels are examined and are demonstrated using microwave television RFI at the Australia Telescope Compact Array. The RFI is attenuated to below the system noise, a reduction of at least 20 dB. While dual-reference cancelers add more reference noise than single-reference cancelers, this noise is zero-mean and only adds to the system noise, decreasing the sensitivity. The residual RFI that remains in the output of single-reference cancelers (but not dual-reference cancelers) sets a nonzero noise floor that does not act like random system noise and may limit the achievable sensitivity. Thus, dual-reference cancelers often result in superior cancellation. Dual-reference precorrelation cancelers require a double-canceler setup to be useful and to give equivalent results to dual-reference postcorrelation cancelers.Comment: 11 pages created using emulateap

Household technology acceptance heterogeneity in computer adoption

Technology policy analysis and implementation relies on knowledge and understanding of the "adoption gap" in information technologies among different groups of consumers. Factors that explain the residential "digital divide" also need to be identified and quantified. Through the application of survey data we provide an enhanced understanding of the key factors involved in the choice of residential computer adoption. These choices are analysed using a discrete choice model that reveals that sociodemographic factors strongly influence the adoption of the residential computer. Moreover, we apply the basic findings of the Technology Adoption Model (TAM) into the discrete choice framework heteroscedastically to deepen our understanding of why some households choose not to have computers; above and beyond what may be explained by socio-demography alone. Generally, we find that computer adoption is sensitive to household digital division measures and that the model fit improves with the heteroscedastic addition of the TAM factors. These findings are important for market planners and policymakers who wish to understand and quantify the impact of these factors on the digital divide across different household types, as defined by the TAM model

Anisotropy beta functions

The flow of couplings under anisotropic scaling of momenta is computed in $\phi^3$ theory in 6 dimensions. It is shown that the coupling decreases as momenta of two of the particles become large, keeping the third momentum fixed, but at a slower rate than the decrease of the coupling if all three momenta become large simultaneously. This effect serves as a simple test of effective theories of high energy scattering, since such theories should reproduce these deviations from the usual logarithmic scale dependence.Comment: uuencoded ps file, 6 page

A multi-data source surveillance system to detect a bioterrorism attack during the G8 summit in Scotland

In 18 weeks, Health Protection Scotland (HPS) deployed a syndromic surveillance system to early-detect natural or intentional disease outbreaks during the G8 Summit 2005 at Gleneagles, Scotland. The system integrated clinical and non-clinical datasets. Clinical datasets included Accident and Emergency (A and E) syndromes, and General Practice (GPs) codes grouped into syndromes. Non-clinical data included telephone calls to a nurse helpline, laboratory test orders, and hotel staff absenteeism. A cumulative sum-based detection algorithm and a log-linear regression model identified signals in the data. The system had a fax-based track for real-time identification of unusual presentations. Ninety-five signals were triggered by the detection algorithms and four forms were faxed to HPS. Thirteen signals were investigated. The system successfully complemented a traditional surveillance system in identifying a small cluster of gastroenteritis among the police force and triggered interventions to prevent further cases

A Dynamical Systems Analysis of Methanol-Air Auto-Ignition

Dynamical systems analysis was employed as an alternative investigative tool to conventional reaction path analysis and sensitivity analysis in methanol-air auto-ignition, in which the non-linear chemical rate equations describing a homogeneous, methanol-air auto-ignition system were linearised. The resultant system of linear, inhomogeneous differential equations were solved analytically using an eigen-mode analysis. The numerically determined solution to the non-linear auto-ignition trajectory was employed to determine the local analytic behaviour for a number of regular points along the solution trajectory to equilibrium. The solution trajectory was found to qualitatively change three times, thereby defining four different regions in the time and temperature domain. The dominant eigen-mode solutions were expressed in terms of dominant reactions at regular intervals along the solution path, revealing the dominant local chemistry. The solution trajectory was dominated by four explosive modes in the first, low temperature region (T < 1,090 K). Two dominant explosive modes coupled to form an explosive, oscillating mode in the second region (1,090 K < T < 1,160 K). In the third region (1,160 K < T < 2,000 K), the explosive, oscillating mode changed to a decaying, oscillating mode. The changes in the low temperature region of the solution trajectory were found to be associated with the critical points in the evolution of the branching agent (hydrogen peroxide) concentration. The third qualitative change occurred at T ~ 2,000 K, when the dominant decaying, oscillating mode describing methanol and formaldehyde oxidation to carbon monoxide collapsed, to be replaced with real, decaying modes (proper stable nodes) describing the wet oxidation of carbon monoxide to carbon dioxide, and its reverse reaction, together with the high temperature formation of water and other equilibrium products

Evidence for extended IR emission in NGC2798 and NGC6240

Extended emission at 10 and 20 microns can be used to distinguish starbursts from monsters as the underlying energy source driving the luminous infrared emission in the central regions of galaxies. The spatial extent of the mid infrared emission in the interacting galaxy NCG 2798 and the merger NGC 6240 were investigated. The 10 and 20 micron profiles of the IR source in NGC 2798 are significantly wider than beam profiles measured on a standard star, supporting a starburst interpretation of its IR luminosity. For NGC 6240 there is marginal evidence for an extended 10 micron source, suggesting that a significant fraction of its IR luminosity could be produced by a burst of star formation

Simple Apparatus for Producing Single Liquid Drops

A simple experimental apparatus has been used to produce individual mercury and sodium amalgam drops in the size range of 0.3-2.5 mm diam. A high resistance to the flow of liquid was provided by a capillary tube. The cross section consisted of a 0.20 mm o.d. tungsten wire placed in a 0.25 mm capillary bore. By this method, flow rates of 1 μl/s and lower were obtained, which enabled the formation of drops as small as 1 mm diam in a time interval of 20 s. The drops were formed at a plastic tip, and on reaching the desired size, were stripped off by a stream of argon. An optical sensor was used to detect the growing drop and to switch on the argon stream at the desired time. The growth of the drops at the tip was observed using an image analysis system which showed good agreement between the observed and calculated drop sizes at various instants. The consistency in size from drop to drop, for any particular setting of the apparatus, was evaluated by analyzing magnified pictures of the drops as well as by measuring their weights. The variation in the drop size was found to be within ±2% of the mean value