Parallel implementation of fast randomized algorithms for the decomposition of low rank matrices

We analyze the parallel performance of randomized interpolative decomposition by decomposing low rank complex-valued Gaussian random matrices up to 64 GB. We chose a Cray XMT supercomputer as it provides an almost ideal PRAM model permitting quick investigation of parallel algorithms without obfuscation from hardware idiosyncrasies. We obtain that on non-square matrices performance becomes very good, with overall runtime over 70 times faster on 128 processors. We also verify that numerically discovered error bounds still hold on matrices nearly two orders of magnitude larger than those previously tested.Comment: 9 pages, 2 figures, 5 tables. v2: extended version. this is a preprint of a published paper - see published version for definitive versio

Thromboelastometry (ROTEM®) in children: age-related reference ranges and correlations with standard coagulation tests

Background The small sample volume needed and the prompt availability of results make viscoelastic methods like rotational thromboelastometry (ROTEM®) attractive for monitoring coagulation in small children. However, data on reference ranges for ROTEM® parameters in children are scarce. Methods Four hundred and seven children (ASA I and II) undergoing elective surgery were recruited for this prospective, two-centre, observational study. Subjects were grouped as follows: 0-3, 4-12, 13-24 months, 2-5, 6-10, and 11-16 yr. Study objectives were to establish age-dependent reference ranges for ROTEM® assays, analyse age dependence of parameters, and compare ROTEM® data with standard coagulation tests. Results Data from 359 subjects remained for final analysis. Except for extrinsically activated clot strength and lysis, parameters for ROTEM® assays were significantly different among all age groups. The most striking finding was that subjects aged 0-3 months exhibited accelerated initiation (ExTEM coagulation time: median 48 s, Q1-Q3 38-65 s; P=0.001) and propagation of coagulation (α angle: median 78o, Q1-Q3 69-84o; P<0.001) and maximum clot firmness (median 62 mm, Q1-Q3 54-74 mm), although standard plasma coagulation test results were prolonged (prothrombin time: median 13.2 s, Q1-Q3 12.6-13.6 s; activated partial thromboplastin time: median 42 s, Q1-Q3 40-46 s). Lysis indices of <85% were observed in nearly one-third of all children without increased bleeding tendency. Platelet count and fibrinogen levels correlated significantly with clot strength, and fibrinogen levels correlated with fibrin polymerization. Conclusions Reference ranges for ROTEM® assays were determined for all paediatric age groups. These values will be helpful when monitoring paediatric patients and in studies of perioperative coagulation in childre

The Effect of Social Capital on Hispanic Post-Secondary Educational Outcomes

Hispanics have one of the lowest college enrollment rate of any racial/ethnic group in the United States, and for those who enroll, they are three times less likely than Whites to graduate with a four-year degree. Past research has explored racial and socioeconomic disparities for Hispanics and focused on educational attrition. This study takes a different approach, drawing attention to factors which positively influence college degree attainment. Specifically, utilizing a social capital and education retention theory framework, this study sought to understand how social capital factors may contribute to Hispanic educational outcomes. Using a national data set from the Educational Longitudinal Study of 2002, I hypothesized that students who have faculty, peer and family social networks, along with participation in formal extracurricular participation at the high school and college levels, would be more likely to enroll in college after high school and complete a bachelor’s degree. I found that peer networks, faculty encouragement, and participation in extracurricular activities all predict greater educational outcomes for Hispanics, net of racial differences and socioeconomic background. Not all social networks produced positive outcomes: receiving college information from siblings and teachers had detrimental effects for Hispanics. Implications for applied interventions are discussed