Optimal incorporation of sparsity information by weighted ℓ1\ell_1 optimization

Compressed sensing of sparse sources can be improved by incorporating prior knowledge of the source. In this paper we demonstrate a method for optimal selection of weights in weighted $L_1$ norm minimization for a noiseless reconstruction model, and show the improvements in compression that can be achieved.Comment: 5 pages, 2 figures, to appear in Proceedings of ISIT201

A mean field method with correlations determined by linear response

We introduce a new mean-field approximation based on the reconciliation of maximum entropy and linear response for correlations in the cluster variation method. Within a general formalism that includes previous mean-field methods, we derive formulas improving upon, e.g., the Bethe approximation and the Sessak-Monasson result at high temperature. Applying the method to direct and inverse Ising problems, we find improvements over standard implementations.Comment: 15 pages, 8 figures, 9 appendices, significant expansion on versions v1 and v

A compilation of information and data on the Manson impact structure

A problem for the impact hypothesis for the Cretaceous-Tertiary (K-T) mass extinction is the apparent absence of an identifiable impact site. The Manson Impact Structure is a candidate because it is the largest recognized in the U.S.; it is relatively close to the largest and most abundant shocked quartz grains found at the K-T boundary; and its age is indistinguishable from that of the K-T boundary based on paleontological evidence, fission track dates, and preliminary Ar-40/Ar-39 measurements. The region of northwest central Iowa containing the Manson Impact Structure is covered by Quaternary glacial deposits underlain by Phanerozoic sedimentary rocks (mostly flat-lying carbonates) and Proterozoic red clastic, metamorphic, volcanic, and plutonic rocks. In a circular area about 22 miles (35 km) in diameter around Manson, Iowa, this normal sequence is absent or disturbed and near the center of the disturbed area granitic basement rocks have been uplifted some 20,000 ft (6000m). Attention was drawn to Manson initially by the unusual quality of the groundwater there. Within the structure three roughly concentric zones of rock associations have been identified: (1) displaced strata; (2) completely disrupted strata, and igneous and metamorphic rocks. Manson was established as an impact structure based on its circular shape, its central uplift, and the presence of shocked quartz within the granitic central uplift. A gravity survey identified locations of low-density brecciated rocks and high-density uplifted crystalline rocks, but the outer boundary of the structure could not be established. Aeromagnetic and ground magnetic surveys showed locations and depths of shallowly buried crystalline rock and the locations of faults. A refraction seismic survey identified the crystalline central uplift, determined that the average elevation of bedrock is 70 ft (20 m) higher outside the structure than within, and was used to map the bedrock topography within the structure. A connection between the Manson impact and the K-T boundary may be established or refuted through study of the impact energy, the impact time, and composition of host rock, possible impactors, and impact melts

Conceptualising, Understanding and Alleviating Choking in Sport: The Role of Significant Others

Through a qualitative descriptive methodology, this study sought to understand the influence of significant others (i.e., parents, coaches and team-mates) on athletes’ experience of choking in sport. Nine participants (6 males, 3 females) who were either elite (n=1) or intermediate / lower-end semi-athletes (n=8) completed semi-structured interviews which explored their choking experiences and the perceived impact that significant others had on their choking episodes. All participants were aged between 21 and 45 (m = 24.56; SD = 7.68), and were recruited from a number of sports including: football (n=4), cricket (n=2), golf (n=1), netball (n=1) and rifle shooting (n=1). Participants perceived their choking events were associated with a range of antecedents (i.e., perceived pressure, self-presentational motives and high expectations), mechanisms (i.e., debilitative anxiety, distraction and self-focus), moderators (i.e., social support, self-confidence, team cohesion, ego motivational climate and leadership), and consequences (i.e., acute drop in performance, short- and long-term negative affect, and a delayed-positive affect). Significant others were reported to increase or decrease the likelihood of choking, as a result of their influence on perceived pressure, self-presentational motives and expectations prior to the choking episode. Moreover, they also appeared to encourage / discourage choking through affecting the athletes’ self-confidence, levels of team cohesion, the motivational climate and availability of social support. The findings of this study extend the choking literature and identify recommendations which practitioners can utilise to manage the impact that significant others have athletes who choke frequently