Wednesday, November 21, 2012

Influence of numerical model decisions on the flow-induced vibration of a computational vocal fold model

Shurtz, Timothy E., and Scott L. Thomson. "Influence of numerical model decisions on the flow-induced vibration of a computational vocal fold model." Computers & Structures (2012).
 
 Computational vocal fold models are often used to study the physics of voice production. In this paper the sensitivity of predicted vocal fold flow-induced vibration and resulting airflow patterns to several modeling selections is explored. The location of contact lines used to prevent mesh collapse and assumptions of symmetry were found to influence airflow patterns. However, these variables had relatively little effect on the vibratory response of the vocal fold model itself. Model motion was very sensitive to Poisson’s ratio. The importance of these parameter sensitivities in the context of vocal fold modeling is discussed.

Equivalence of superspace groups.

van Smaalen, Sander, B. J. Campbell, and H. T. Stokes. "Equivalence of superspace groups." Acta Crystallographica Section A: Foundations of Crystallography 69, no. 1 (2012): 0-0.
 
BYU researcher: H.T. Stokes
 
An algorithm is presented which determines the equivalence of two settings of a (3 + d)-dimensional superspace group (d = 1, 2, 3). The algorithm has been implemented as a web tool [{\tt findssg}] on [{\tt SSG(3+d)D}], providing the transformation of any user-given superspace group to the standard setting of this superspace group in [{\tt SSG(3+d)D}]. It is shown how the standard setting of a superspace group can be directly obtained by an appropriate transformation of the external-space lattice vectors (the basic structure unit cell) and a transformation of the internal-space lattice vectors (new modulation wavevectors are linear combinations of old modulation wavevectors plus a three-dimensional reciprocal-lattice vector). The need for non-standard settings in some cases and the desirability of employing standard settings of superspace groups in other cases are illustrated by an analysis of the symmetries of a series of compounds, comparing published and standard settings and the transformations between them. A compilation is provided of standard settings of compounds with two- and three-dimensional modulations. The problem of settings of superspace groups is discussed for incommensurate composite crystals and for chiral superspace groups.

Right Time, Right Place" Health Communication on Twitter: Value and Accuracy of Location Information

Burton, Scott H., Kesler W. Tanner, Christophe G. Giraud-Carrier, Joshua H. West, and Michael D. Barnes. "" Right Time, Right Place" Health Communication on Twitter: Value and Accuracy of Location Information." Journal of Medical Internet Research 14, no. 6 (2012): e156.
 

ABSTRACT

Background: Twitter provides various types of location data, including exact Global Positioning System (GPS) coordinates, which could be used for infoveillance and infodemiology (ie, the study and monitoring of online health information), health communication, and interventions. Despite its potential, Twitter location information is not well understood or well documented, limiting its public health utility.
Objective: The objective of this study was to document and describe the various types of location information available in Twitter. The different types of location data that can be ascertained from Twitter users are described. This information is key to informing future research on the availability, usability, and limitations of such location data.
Methods: Location data was gathered directly from Twitter using its application programming interface (API). The maximum tweets allowed by Twitter were gathered (1% of the total tweets) over 2 separate weeks in October and November 2011. The final dataset consisted of 23.8 million tweets from 9.5 million unique users. Frequencies for each of the location options were calculated to determine the prevalence of the various location data options by region of the world, time zone, and state within the United States. Data from the US Census Bureau were also compiled to determine population proportions in each state, and Pearson correlation coefficients were used to compare each state’s population with the number of Twitter users who enable the GPS location option.
Results: The GPS location data could be ascertained for 2.02% of tweets and 2.70% of unique users. Using a simple text-matching approach, 17.13% of user profiles in the 4 continental US time zones were able to be used to determine the user’s city and state. Agreement between GPS data and data from the text-matching approach was high (87.69%). Furthermore, there was a significant correlation between the number of Twitter users per state and the 2010 US Census state populations (r ≥ 0.97, P < .001).
Conclusions: Health researchers exploring ways to use Twitter data for disease surveillance should be aware that the majority of tweets are not currently associated with an identifiable geographic location. Location can be identified for approximately 4 times the number of tweets using a straightforward text-matching process compared to using the GPS location information available in Twitter. Given the strong correlation between both data gathering methods, future research may consider using more qualitative approaches with higher yields, such as text mining, to acquire information about Twitter users’ geographical location.

Bayesian Methods for the Analysis of Small Sample Multilevel Data With a Complex Variance Structure.

Baldwin, Scott A., and Gilbert W. Fellingham. "Bayesian Methods for the Analysis of Small Sample Multilevel Data With a Complex Variance Structure." (2012).
 
Inferences from multilevel models can be complicated in small samples or complex data structures. When using (restricted) maximum likelihood methods to estimate multilevel models, standard errors and degrees of freedom often need to be adjusted to ensure that inferences for fixed effects are correct. These adjustments do not address problems in estimating variance/covariance components. An alternative to the adjusted likelihood method is to use Bayesian methods, which can produce accurate inferences about fixed effects and variance/covariance parameters. In this article, the authors contrast the benefits and limitations of likelihood and Bayesian methods in the estimation of multilevel models. The issues are discussed in the context of a partially clustered intervention study, a common intervention design that has been shown to require an adjusted likelihood analysis. The authors report a Monte Carlo study that compares the performance of an adjusted restricted maximum likelihood (REML) analysis to a Bayesian analysis. The results suggest that for fixed effects, the models perform equally well with respect to bias, efficiency, and coverage of interval estimates. Bayesian models with a carefully selected gamma prior for the variance components were more biased but also more efficient with respect to estimation of the variance components than the REML model. However, the results also show that the inferences about the variance components in partially clustered studies are sensitive to the prior distribution when sample sizes are small. Finally, the authors compare the results of a Bayesian and adjusted likelihood model using data from a partially clustered intervention trial. (PsycINFO Database Record (c) 2012 APA, all rights reserved)

With Religious Liberty for All: A Defense of the Affordable Care Act's Contraception Coverage Mandate.

Gedicks, Frederick. "With Religious Liberty for All: A Defense of the Affordable Care Act's Contraception Coverage Mandate." American Constitution Society for Law and Policy Issue Brief, Forthcoming (2012).
 
The “contraception mandate” of the Patient Protection and Affordable Care Act of 2010 poses a straightforward question for religious liberty jurisprudence: Must government excuse a believer from complying with a religiously burdensome law, when doing so would violate the liberty of others by imposing on them the costs and consequences of religious beliefs that they do not share? To ask this question is to answer it: One's religious liberty does not include the right to interfere with the liberty of others, and thus religious liberty may not be used by a religious employer to force employees to pay the costs of anti-contraception beliefs that they do not share.

That the free exercise of religion is fundamental constitutional right is not in doubt. But access to contraceptives is also fundamental. Such access, moreover, is a critical component of the well-being and advancement of women, enabling them to time and space their pregnancies, thereby enhancing their own health (and that of their new-born children) and facilitating their participation in the workforce on more equal terms with men.

Contraception nevertheless remains a significant expense beyond the reach of many women who lack insurance coverage or whose health insurance plans do not cover contraceptives or do so only with substantial patient cost-sharing. This is a financial obstacle to the use of contraception by working-class and lower-income women, and simple economics suggests that women of all but the highest income levels are likely to use contraceptives more often and more consistently when they can obtain them at no cost.

The rhetoric of those challenging the mandate charges federal violation of the free exercise rights of religious employers, usually without mentioning the substantial federal interests in protecting the religious liberty and enlarging the access to contraceptives of employees who do not share their employer’s religious values. The contraception mandate strikes a sensible balance of these competing liberty interests by generally exempting only religious persons and organizations who do not externalize the costs of their religious beliefs and practices onto others who do not share them.

The contraception mandate does not violate the rights of religious employers under either the Religion Clauses of the First Amendment or the Religious Freedom Restoration Act. The mandate is a “religiously neutral, generally applicable” law that does not discriminate against religious employers, does not entangle government in disputes about theology or internal church governance, and does not “substantially” burden the free exercise of religion by nonexempt religious employers. The mandate is additionally justified as the least restrictive means of protecting compelling government interests in public health and gender equity. Finally, while all these conclusions apply fully to religious nonprofit organizations, they apply with special force to religious owners of for-profit businesses operating in commercial markets. 

Mitochondrial Genomic Analysis of Late Onset Alzheimer’s Disease Reveals

Ridge, P. G., T. J. Maxwell, C. D. Corcoran, M. C. Norton, and J. T. Tschanz. "Mitochondrial Genomic Analysis of Late Onset Alzheimer’s Disease Reveals." (2012).
 
BYU Researchers: Perry G. Ridge, John S. K. Kauwe
 
Abstract
Background: Alzheimer’s disease (AD) is the most common cause of dementia and AD risk clusters within families. Part of the familial aggregation of AD is accounted for by excess maternal vs. paternal inheritance, a pattern consistent with mitochondrial inheritance. The role of specific mitochondrial DNA (mtDNA) variants and haplogroups in AD risk is uncertain.

Methodology/Principal Findings: We determined the complete mitochondrial genome sequence of 1007 participants in the Cache County Study on Memory in Aging, a population-based prospective cohort study of dementia in northern Utah. AD diagnoses were made with a multi-stage protocol that included clinical examination and review by a panel of clinical experts. We used TreeScanning, a statistically robust approach based on haplotype networks, to analyze the mtDNA
sequence data. Participants with major mitochondrial haplotypes H6A1A and H6A1B showed a reduced risk of AD (p = 0.017, corrected for multiple comparisons). The protective haplotypes were defined by three variants: m.3915G.A, m.4727A.G, and m.9380G.A. These three variants characterize two different major haplogroups. Together m.4727A.G and m.9380G.A define H6A1, and it has been suggested m.3915G.A defines H6A. Additional variants differentiate H6A1A
and H6A1B; however, none of these variants had a significant relationship with AD case-control status.

Conclusions/Significance: Our findings provide evidence of a reduced risk of AD for individuals with mtDNA haplotypes H6A1A and H6A1B. These findings are the results of the largest study to date with complete mtDNA genome sequence data, yet the functional significance of the associated haplotypes remains unknown and replication in others studies is
necessary.

Examining the Early Evidence for Self‐directed Marriage and Relationship Education: A Meta‐analytic Study

McAllister, Shelece, Stephen F. Duncan, and Alan J. Hawkins. "Examining the Early Evidence for Self‐directed Marriage and Relationship Education: A Meta‐analytic Study." Family Relations 61, no. 5 (2012): 742-755.
 
This meta-analysis examines the efficacy of self-directed marriage and relationship education (MRE) programs on relationship quality and communication skills. Programs combining traditional face-to-face learning with self-directed elements are also examined, and traditional programs' effectiveness is included as a comparison point. Sixteen studies focused on self-directed interventions; 13 studies focused on programs combining self-directed and traditional components. For self-directed programs, the effect size for relationship quality was small and not significant (d = .032, ns); a small, significant effect size was found for communication skills (d = .160, p < .05). For blended programs, effect sizes were significant for relationship quality (d = .429, p < .01) and communication skills (d = .715, p < .05), and blended programs produced larger effect sizes than traditional programs.