A Corpus-Based Approach for Building Semantic Lexicons

Semantic knowledge can be a great asset to natural language processing systems, but it is usually hand-coded for each application. Although some semantic information is available in general-purpose knowledge bases such as WordNet and Cyc, many applications require domain-specific lexicons that represent words and categories for a particular topic. In this paper, we present a corpus-based method that can be used to build semantic lexicons for specific categories. The input to the system is a small set of seed words for a category and a representative text corpus. The output is a ranked list of words that are associated with the category. A user then reviews the top-ranked words and decides which ones should be entered in the semantic lexicon. In experiments with five categories, users typically found about 60 words per category in 10-15 minutes to build a core semantic lexicon.Comment: 8 pages - to appear in Proceedings of EMNLP-

Being Y-AP Savvy: A primer on creating & sustaining youth-adult partnerships

This manual is designed to help all those committed to youth-adult partnerships (Y-AP) acquire core knowledge, establish and communicate a point of view about Y-AP, and build consensus on key issues regarding Y-AP

Constraints on Dark Matter from Colliders

We show that colliders can impose strong constraints on models of dark matter, in particular when the dark matter is light. We analyze models where the dark matter is a fermion or scalar interacting with quarks and/or gluons through an effective theory containing higher dimensional operators which represent heavier states that have been integrated out of the effective field theory. We determine bounds from existing Tevatron searches for monojets as well as expected LHC reaches for a discovery. We find that colliders can provide information which is complementary or in some cases even superior to experiments searching for direct detection of dark matter through its scattering with nuclei. In particular, both the Tevatron and the LHC can outperform spin dependent searches by an order of magnitude or better over much of parameter space, and if the dark matter couples mainly to gluons, the LHC can place bounds superior to any spin independent search.Comment: 23 pages, 16 figure

Pathways to youth empowerment and community connectedness: a study of youth-adult partnership in Malaysian after-school, co-curricular programs

After-school programs are prevalent across the world, but there is a paucity of research that examines quality within the “black box” of programs at the point of service. Grounded in current theory, this research examined hypothesized pathways between the experience of youth-adult partnership (youth voice in decision-making; supportive adult relationships), the mediators of program safety and engagement, and the developmental outcomes of youth empowerment (leadership competence, policy control) and community connectedness (community connections, school attachment). Surveys were administered to 207 ethnically diverse (47.3 % female; 63.3 % Malay) youth, age 15–16, attending after-school co-curricular programs in Kuala Lumpur, Malaysia. Results showed that youth voice in program decision-making predicted both indicators of youth empowerment. Neither youth voice nor supportive adult relationships was directly associated with community connectedness, however. Program engagement mediated the associations between youth-adult partnership and empowerment. In contrast, program safety mediated the associations between youth-adult partnership and community connectedness. The findings indicate that the two core components of youth-adult partnership—youth voice and supportive adult relationships—may operate through different, yet complementary, pathways of program quality to predict developmental outcomes. Implications for future research are highlighted. For reasons of youth development and youth rights, the immediate challenge is to create opportunities for youth to speak on issues of program concern and to elevate those adults who are able and willing to help youth exercise their voice

Conceptualizing and measuring youth–adult partnership in community programs: a cross national study

Youth participation in program and community decision making is framed by scholars as an issue of social justice, a platform for positive youth development and effective citizenry, and a strategy for nation building. Recent literature reviews have consistently identified youth–adult partnership (Y–AP) as an effective type of youth participation across highly diverse contexts. These same reviews, however, note that indicators of Y–AP have not been conceptualized and validated for measurement purposes. The present study addresses this limitation by developing a brief measure of Y–AP that is explicitly grounded in current theory, research, and community practice. The measure was administered to youth in the United States, Malaysia, and Portugal (N = 610). Validation was assessed through factor analysis and tests of factorial, discriminant, and concurrent validity. Results confirmed the two predicted dimensions of the Y–AP measure: youth voice in decision making and supportive adult relationships. These two dimensions were also found to be distinct from other measures of program quality: safety and engagement. As predicted, they also significantly correlated with measures of agency and empowerment. It is concluded that the measure has the potential to support community efforts to maximize the quality of youth programs

Collagen fibre implant for tendon and ligament biological augmentation. In vivo study in an ovine model.

PURPOSE: Although most in vitro studies indicate that collagen is a suitable biomaterial for tendon and ligament tissue engineering, in vivo studies of implanted collagen for regeneration of these tissues are still lacking. The objectives of this study were the following: (1) to investigate the regeneration of the central third of the ovine patellar tendon using implants made of an open array of collagen fibres (reconstituted, extruded bovine collagen); and (2) to compare two collagen crosslinking chemistries: carbodiimide and carbodiimide associated with ethyleneglycoldiglycidylether. METHODS: Forty-eight Welsh Mountain sheep were operated on their right hind leg. The central third of patellar tendon was removed and substituted with carbodiimide (n = 16) and carbodiimide-ethyleneglycoldiglycidylether-crosslinked implants (n = 16). In the control group the defect was left empty (n = 16). The central third of contralateral unoperated tendons was used as positive controls. Half of the sheep in each group were killed at 3- and 6-month time points. After proper dissection, tendon sub-units (medial, central and lateral) were tested to failure (n = 6 for each group), whilst 2 non-dissected samples were used for histology. RESULTS: Both the implants had significantly lower stress to failure and modulus with respect to native tendon at both 3- and at 6-month time points. The implants did not statistically differ in stress to failure, whilst carbodiimide-crosslinked implants had significantly higher modulus than carbodiimide-ethyleneglycoldiglycidylether-crosslinked implants both at 3 and at 6 months. Histology showed carbodiimide-crosslinked implants to have a better integration with the native tendon than carbodiimide-ethyleneglycoldiglycidylether-crosslinked implants. Carbodiimide-crosslinked implants appeared partially resorbed and showed increased tissue ingrowth with respect to carbodiimide-ethyleneglycoldiglycidylether-crosslinked implants. CONCLUSIONS: To deliver collagen implants as an open array of fibres allows optimal tendon-implant integration and good ingrowth of regenerated tissue. In the present study the resorption rate of both the examined implants was too low due to the high level of crosslinking. This led to only minor substitution of the implant with regenerated tissue, which in turn produced a low-strength implanted region. Further studies are needed to find the right balance between strength and resorption rate of collagen fibres

A survey of extended radio jets with Chandra and HST

We present the results from an X-ray and optical survey of a sample of 17 radio jets in AGN performed with Chandra and HST. The sample was selected from the radio and is unbiased toward detection at shorter wavelengths, but preferentially it includes beamed sources. We find that X-ray emission is common on kpc-scales, with over half radio jets exhibiting at least one X-ray knot on the Chandra images. The distributions of the radio-to-X-ray and radio-to-optical spectral indices for the detected jets are similar to the limits for the non-detections,suggesting all bright radio jets have X-ray counterparts which will be visible in longer observations. Comparing the radio and X-ray morphologies shows that the majority of the X-ray jets have structures that closely map the radio. Analysis of the SED of the jet knots suggest the knots in which the X-ray and radio morphologies track each other produce X-rays by IC scattering of the Cosmic Microwave Background. The remaining knots produce X-rays by the synchrotron process. Spectral changes are detected along the jets, with the ratio of the X-ray-to-radio and optical-to-radio flux densities decreasing from the inner to the outer regions. This suggests the presence of an additional contribution to the X-ray flux in the jet's inner part, either from synchrotron or IC of the stellar light. Alternatively, in a pure IC/CMB scenario, the plasma decelerates as it flows from the inner to the outer regions. Finally, the X-ray spectral indices for the brightest knots are flat, indicating that the bulk of the luminosity of the jets is emitted at GeV energies, and raising the interesting possibility of future detections with GLAST.Comment: 26 pages, 6 ps figures, 6 jpeg figures (1 replaced); accepted for publication in Ap