Statistical classification techniques for engineering and climatic data samples

Fisher's sample linear discriminant function is modified through an appropriate alteration of the common sample variance-covariance matrix. The alteration consists of adding nonnegative values to the eigenvalues of the sample variance covariance matrix. The desired results of this modification is to increase the number of correct classifications by the new linear discriminant function over Fisher's function. This study is limited to the two-group discriminant problem

Statistical analysis of SSME system data

A statistical methodology to enhance the Space Shuttle Main Engine (SSME) performance prediction accuracy is proposed. This methodology was to be used in conjunction with existing SSME performance prediction computer codes to improve parameter prediction accuracy and to quantify that accuracy. However, after a review of related literature, researchers concluded that the proposed problem required a coverage of areas such as linear and nonlinear system theory, measurement theory, statistics, and stochastic estimation. Since state space theory is the foundation for a more complete study of each of the before mentioned areas, these researchers chose to refocus emphasis to cover the more specialized topic of state vector estimation procedures. State vector estimation was also selected because of current and future concerns by NASA for SSME performance evaluation; i.e., there is a current interest in an improved evaluation procedure for actual SSME post flight performance as well as for post static test performance of a single SSME. A current investigation of analytical methods may be used to improve test stand failure detection. This paper considers the issue of post flight/test state variable reconstruction through the application of observations made on the output of the Space Shuttle propulsion system. Rogers used the Kalman filtering procedure to reconstruct the state variables of the Space Shuttle propulsion system. An objective of this paper is to give the general setup of the Kalman filter and its connection to linear regression. A second objective is to examine the reconstruction methodology for application to the reconstruction of the state vector of a single Space Shuttle Main Engine (SSME) by using static test firing data

Sexting and Mental Health: A School-based Longitudinal Study Among Youth in Texas

Background: Sexting has emerged as a common socio-cultural problem in our society today. Few studies have estimated the prevalence of sexting among younger middle school youth and even fewer have assessed the relationship between sexting and mental health outcomes like anxiety and depression symptoms among middle school youth. Objectives: To estimate the prevalence of sexting among sixth and seventh-grade middle school students in a large urban school district in Southeast Texas and to assess its relationship with mental health outcomes (both anxiety and depression) among these youth. Methods: A retrospective analysis of an existing three-year randomized, two-arm, nested longitudinal study was conducted. Associations between sexting and depression symptoms; and sexting and anxiety symptoms were assessed via univariate and multivariate logistic analysis. Results: The prevalence of sexting among sixth graders was found to be 12%. Compared to youth who were not engaged in sexting, engagement in sexting was associated with significantly increased odds of depression and anxiety symptoms. Conclusion: Sexting is common among youth and is associated with poorer mental health outcomes such as anxiety and depression among these youth, but further validation of these findings is needed

Perturbation expansions for a class of singular potentials

Harrell's modified perturbation theory [Ann. Phys. 105, 379-406 (1977)] is applied and extended to obtain non-power perturbation expansions for a class of singular Hamiltonians H = -D^2 + x^2 + A/x^2 + lambda/x^alpha, (A\geq 0, alpha > 2), known as generalized spiked harmonic oscillators. The perturbation expansions developed here are valid for small values of the coupling lambda > 0, and they extend the results which Harrell obtained for the spiked harmonic oscillator A = 0. Formulas for the the excited-states are also developed.Comment: 23 page

The origin and evolution of the ribosome

<p>Abstract</p> <p>Background</p> <p>The origin and early evolution of the active site of the ribosome can be elucidated through an analysis of the ribosomal proteins' taxonomic block structures and their RNA interactions. Comparison between the two subunits, exploiting the detailed three-dimensional structures of the bacterial and archaeal ribosomes, is especially informative.</p> <p>Results</p> <p>The analysis of the differences between these two sites can be summarized as follows: 1) There is no self-folding RNA segment that defines the decoding site of the small subunit; 2) there is one self-folding RNA segment encompassing the entire peptidyl transfer center of the large subunit; 3) the protein contacts with the decoding site are made by a set of universal alignable sequence blocks of the ribosomal proteins; 4) the majority of those peptides contacting the peptidyl transfer center are made by bacterial or archaeal-specific sequence blocks.</p> <p>Conclusion</p> <p>These clear distinctions between the two subunit active sites support an earlier origin for the large subunit's peptidyl transferase center (PTC) with the decoding site of the small subunit being a later addition to the ribosome. The main implications are that a single self-folding RNA, in conjunction with a few short stabilizing peptides, formed the precursor of the modern ribosomal large subunit in association with a membrane.</p> <p>Reviewers</p> <p>This article was reviewed by Jerzy Jurka, W. Ford Doolittle, Eugene Shaknovich, and George E. Fox (nominated by Jerzy Jurka).</p

The Association Between Problematic Parental Substance Use and Adolescent Substance Use in an Ethnically Diverse Sample of 9th and 10th Graders

Adolescents of parents who use substances are at an increased risk for substance use themselves. Both parental monitoring and closeness have been shown to mediate the relationship between parents’ and their adolescents’ substance use. However, we know little about whether these relationships vary across different substances used by adolescents. Using structural equation modeling, we examined these associations within a racially and ethnically diverse sample of 9th and 10th graders (N = 927). Path analyses indicated that maternal closeness partially mediated the association between maternal problematic substance use and adolescent alcohol use. Parental monitoring partially mediated the relationship between paternal problematic substance use and adolescent alcohol, cigarette, marijuana, inhalant, and illicit prescription drug use. These results were consistent across gender and race/ethnicity. These findings suggest that parental interventions designed to increase closeness and monitoring may help to reduce adolescent substance use

Assessing the Need and Receptivity for an Integrated Healthy Sexual and Dating Relationships Intervention for Community College Students

Background: In emerging adulthood, youth often become involved in more serious romantic relationships. However, many lack the skills to avoid an unplanned pregnancy or sexually transmitted infection (STI), and to ensure a healthy dating relationship. Community college students serve nearly half of all undergraduate students in the United States; yet, community colleges typically lack resources for sexual health promotion. Purpose: To assess the need and receptivity for a web-based integrated healthy sexual and dating relationships intervention among community college students. Methods: In summer 2016, we partnered with three community colleges in South Central Texas to conduct an online survey of students’ sexual behaviors and dating relationships, and usability testing of activities from an integrated, web-based healthy sexual and dating relationship intervention. Results: Online survey participants (n=271) were 70% female, 38% Hispanic, 24% White, 17% Black, and 16% Asian; 20% self-identified as sexual minority; mean age was 20.8 years (SD = 2.05). Participants reported high rates of sexual risk behavior including sex without a condom or an effective birth control method, low use of long-acting reversible contraception, frequent use of emergency contraception, and low use of dual protection to prevent pregnancy and sexually transmitted infections. Two-thirds reported experiencing any type of dating violence perpetration or victimization in the past year. Usability testing participants (n=14) were 86% female, 42% Hispanic, 50% Asian/Pacific Islander, 14% Black, and 7% White; 71% were sexually experienced; mean age was 20.7 years (SD = 1.64). The web-based activities were highly rated in terms of usability parameters, and positively impacted short-term psychosocial outcomes related to condom use, accessing contraceptive health services, and constructive interpersonal conflict resolution. Conclusion: Findings underscore the high need and receptivity for an integrated healthy sexual and dating relationship web-based intervention among community college students, an understudied subgroup of youth in emerging adulthood

Siren songs or path to salvation? Interpreting the visions of web technology at a UK regional newspaper in crisis, 2006-11

A 5-year case study of an established regional newspaper in Britain investigates journalists about their perceptions of convergence in digital technologies. This research is the first ethnographic longitudinal case study of a UK regional newspaper. Although conforming to some trends observed in the wider field of scholarship, the analysis adds to skepticism about any linear or directional views of innovation and adoption: the Northern Echo newspaper journalists were observed to have revised their opinions of optimum Web practices, and sometimes radically reversed policies. Technology is seen in the period as a fluid, amorphous entity. Central corporate authority appeared to diminish in the period as part of a wider reduction in formalism. Questioning functionalist notions of the market, the study suggests cause and effect models of change are often subverted by contradictory perceptions of particular actions. Meanwhile, during technological evolution, the ‘professional imagination’ can be understood as strongly reflecting the parent print culture and its routines, despite pioneering a new convergence partnership with an independent television company