University of Colorado Boulder

About: University of Colorado Boulder is a education organization based out in Boulder, Colorado, United States. It is known for research contribution in the topics: Population & Galaxy. The organization has 48794 authors who have published 115151 publications receiving 5387328 citations. The organization is also known as: CU Boulder & UCB.

Contribution of copy number variants to schizophrenia from a genome-wide study of 41,321 subjects

Abstract: Copy number variants (CNVs) have been strongly implicated in the genetic etiology of schizophrenia (SCZ). However, genome-wide investigation of the contribution of CNV to risk has been hampered by limited sample sizes. We sought to address this obstacle by applying a centralized analysis pipeline to a SCZ cohort of 21,094 cases and 20,227 controls. A global enrichment of CNV burden was observed in cases (odds ratio (OR) = 1.11, P = 5.7 × 10-15), which persisted after excluding loci implicated in previous studies (OR = 1.07, P = 1.7 × 10-6). CNV burden was enriched for genes associated with synaptic function (OR = 1.68, P = 2.8 × 10-11) and neurobehavioral phenotypes in mouse (OR = 1.18, P = 7.3 × 10-5). Genome-wide significant evidence was obtained for eight loci, including 1q21.1, 2p16.3 (NRXN1), 3q29, 7q11.2, 15q13.3, distal 16p11.2, proximal 16p11.2 and 22q11.2. Suggestive support was found for eight additional candidate susceptibility and protective loci, which consisted predominantly of CNVs mediated by nonallelic homologous recombination.

Facilitating change in undergraduate STEM instructional practices: An analytic review of the literature

Abstract: This article reviews current scholarship about how to promote change in instructional practices used in undergraduate science, technology, engineering, and mathematics (STEM) courses. The review is based on 191 conceptual and empirical journal articles published between 1995 and 2008. Four broad categories of change strategies were developed to capture core differences within this body of literature: disseminating curriculum and pedagogy, developing reflective teachers, enacting policy, and developing shared vision. STEM education researchers largely write about change in terms of dis- seminating curriculum and pedagogy. Faculty development researchers largely write about change in terms of developing reflective teachers. Higher education researchers largely write about change in terms of enacting policy. New work often does not build on prior empirical or theoretical work. Although most articles claim success of the change strategy studied, evidence presented to support these claims is typically not strong. For example, only 21% of articles that studied implementation of a change strategy were categorized as presenting strong evidence to support claims of success or failure of the strategy. These analyses suggest that the state of change strategies and the study of change strategies are weak, and that research communities that study and enact change are largely isolated from one-another. In spite of the weak state of the literature, some conclusions related to the design of change strategies can be drawn from this review. Two commonly used change strategies are clearly not effective: developing and testing ''best practice'' curricular materials and then making these materials available to other facul- ty and ''top-down'' policy-making meant to influence instructional practices. Effective change strategies: are aligned with or seek to change the beliefs of the individuals involved; involve long-term interventions, lasting at least one semester; require understanding a college or university as a complex system and designing a strategy that is compatible with this system. ! 2011 Wiley Periodicals, Inc. J Res Sci Teach 48: 952-984, 2011

Synthesis of minimum roundoff noise fixed point digital filters

Abstract: Beginning with an external specification of a digital filter, structures which minimize roundoff noise are investigated. After fixing the probability of overflow through an l_{2} scaling procedure, roundoff noise is studied via the internal structure of the filter using a state variable formulation. An output noise variance formula in terms of the internal structure is derived. Conditions for minimizing this output noise are established and realizations which meet these conditions are constructed. A new set of filter invariants called second-order modes are defined and shown to play a definitive role in minimal noise realizations. From these invariants, for example, one can calculate the minimal output noise variance of a given external specification. Numerical results are given which compare these new filter structures with the usual parallel and cascade connections of second-order filters, both theoretically and through simulations. For narrow-band filters, these new structures can be orders of magnitude better (in terms of output noise variance). One drawback of these new structures is a large increase in the number of multipliers needed to realize them. However, by applying the theory to subfilters connected in parallel and cascade, a good compromise between output noise and number of multipliers is obtained.

Directional mutation pressure and neutral molecular evolution.

Abstract: A quantitative theory of directional mutation pressure proposed in 1962 explained the wide variation of DNA base composition observed among different bacteria and its small heterogeneity within individual bacterial species. The theory was based on the assumption that the effect of mutation on a genome is not random but has a directionality toward higher or lower guanine-plus-cytosine content of DNA, and this pressure generates directional changes more in neutral parts of the genome than in functionally significant parts. Now that DNA sequence data are available, the theory allows the estimation of the extent of neutrality of directional mutation pressure against selection. Newly defined parameters were used in the analysis, and two apparently universal constants were discovered. Analysis of DNA sequence has revealed that practically all organisms are subject to directional mutation pressure. The theory also offers plausible explanations for the large heterogeneity in guanine-plus-cytosine content among different parts of the vertebrate genome.

Using the gravity equation to differentiate among alternative theories of trade

Abstract: The simple gravity equation explains a great deal about the data on bilateral trade flows and is consistent with several theoretical models of trade. We argue that alternative theories nev- ertheless predict subtle differences in key parameter values, depending on whether goods are homogeneous or differentiated and whether or not there are barriers to entry. Our empirical work for differentiated goods delivers results consistent with the theoretical predictions of the monopolistic-competition model, or a reciprocal-dumping model with free entry. Homo- geneous goods are described by a model with national (Armington) product differentiation or