Line arrangements and direct sums of free groups

We show that if the fundamental groups of the complements of two line arrangements in the complex projective plane are isomorphic to the same direct sum of free groups, then the complements of the arrangements are homotopy equivalent. For any such arrangement, we construct another arrangement that is complexified-real, the intersection lattices of the arrangements are isomorphic, and the complements of the arrangements are diffeomorphic.Comment: 15 pages, 4 figure

Reset Aviation Maintenance Program Study of U.S. Army Aviation

U.S. Army helicopter maintenance condition is affected by operation environment and high flight hours. Due to the environmental conditions and high operation tempo of Afghanistan and Iraq, U.S. Army Aviation created the RESET aviation maintenance program to provide restorative maintenance following deployments in theater. The RESET maintenance program was created in addition to the existing two-level maintenance programs. Following deployment, RESET is a thorough cleaning to remove contaminants, inspection of airframe and components, and repair cycle to restore the condition of the helicopter to acceptable condition. Based on the original intent of RESET, it was projected that at the conclusion of military operations in Afghanistan and Iraq, the RESET maintenance program could be discontinued. Because of the presumed safety, reliability, and mission readiness created by RESET, this thesis appraised the RESET maintenance program as a permanent addition to U.S. Army Aviation maintenance programs. The hypothesis was that RESET does improve safety, reliability, and mission readiness of the Army UH-60 Black Hawk fleet. The design was a quantitative survey of three variables: safety, reliability, and mission readiness. The survey featured Likert scale and open-ended questions of three groups: UH-60 maintenance test pilots, UH-60 AVUM/AVIM maintenance supervisory personnel, and ACE (Airframe Condition Evaluation) technical evaluators. Data from each of the three survey groups verified the hypothesis that RESET improved safety, reliability, and mission readiness. Data from open-ended questions indicated that the additional disassembly and special inspections of RESET are more extensive than the aviation unit and intermediate Phased Maintenance Inspection (PMI). Therefore, given the disassembly and special inspections of RESET, and the verification that RESET improves safety, reliability, and mission readiness, it was concluded that RESET is a successful program that should be continued. Based on the effectiveness of RESET in discovering these deficiencies, RESET should be a permanent addition to the Army aviation maintenance programs

Synthesis and Characterization of Monosaccharide-derived Low Molecular Weight Gelators

Low molecular weight gelators (LMWGs) are interesting materials whose applications are as diverse and wide ranging as their molecular structures. These materials self-assemble through the formation of non-covelent intermolecular forces and interactions to form supramolecular assemblies that trap solvent within their matrices. Because of the non-covalent nature of the forces of self-assembly, the gelation process is typically thermally reversible. In addition, low molecular weight gelators can also be modified to respond to various stimuli, such as change in pH, presence of enzymes or metal cations, or exposure to light. The design of low molecular weight gelators is often difficult, and most new classes of low molecular weight gelators are discovered by serendipity. As such, it is often useful to use structural templates in the design of LMWGs. Biomolecules, such as steroids, amino acids and peptides, and carbohydrates make excellent templates due to their inherent propensity to self assemble. A review of the current literature regarding the use of biomolecules as templates for the design and synthesis of LMWGs will be presented in chapter 1. Our research group has been active in the research of carbohydrate-based LMWGs for several years, and these results are also briefly reviewed in the related chapters. The synthesis and characterization of ester derivatives of D-galactose, D-glucose, and amide derivatives of D-glucosamine will be discussed in chapters 2-4, along with their evaluation for gelation in aqueous and organic solvents, such as hexane, ethanol, water, and aqueous DMSO or ethanol mixtures

Synthesis and Characterization of Monosaccharide-derived Low Molecular Weight Gelators

Low molecular weight gelators (LMWGs) are interesting materials whose applications are as diverse and wide ranging as their molecular structures. These materials self-assemble through the formation of non-covelent intermolecular forces and interactions to form supramolecular assemblies that trap solvent within their matrices. Because of the non-covalent nature of the forces of self-assembly, the gelation process is typically thermally reversible. In addition, low molecular weight gelators can also be modified to respond to various stimuli, such as change in pH, presence of enzymes or metal cations, or exposure to light. The design of low molecular weight gelators is often difficult, and most new classes of low molecular weight gelators are discovered by serendipity. As such, it is often useful to use structural templates in the design of LMWGs. Biomolecules, such as steroids, amino acids and peptides, and carbohydrates make excellent templates due to their inherent propensity to self assemble. A review of the current literature regarding the use of biomolecules as templates for the design and synthesis of LMWGs will be presented in chapter 1. Our research group has been active in the research of carbohydrate-based LMWGs for several years, and these results are also briefly reviewed in the related chapters. The synthesis and characterization of ester derivatives of D-galactose, D-glucose, and amide derivatives of D-glucosamine will be discussed in chapters 2-4, along with their evaluation for gelation in aqueous and organic solvents, such as hexane, ethanol, water, and aqueous DMSO or ethanol mixtures

Ideal Bandgap in a 2D Ruddlesden-Popper Perovskite Chalcogenide for Single-junction Solar Cells

Transition metal perovskite chalcogenides (TMPCs) are explored as stable, environmentally friendly semiconductors for solar energy conversion. They can be viewed as the inorganic alternatives to hybrid halide perovskites, and chalcogenide counterparts of perovskite oxides with desirable optoelectronic properties in the visible and infrared part of the electromagnetic spectrum. Past theoretical studies have predicted large absorption coefficient, desirable defect characteristics, and bulk photovoltaic effect in TMPCs. Despite recent progresses in polycrystalline synthesis and measurements of their optical properties, it is necessary to grow these materials in high crystalline quality to develop a fundamental understanding of their optical properties and evaluate their suitability for photovoltaic application. Here, we report the growth of single crystals of a two-dimensional (2D) perovskite chalcogenide, Ba3Zr2S7, with a natural superlattice-like structure of alternating double-layer perovskite blocks and single-layer rock salt structure. The material demonstrated a bright photoluminescence peak at 1.28 eV with a large external luminescence efficiency of up to 0.15%. We performed time-resolved photoluminescence spectroscopy on these crystals and obtained an effective recombination time of ~65 ns. These results clearly show that 2D Ruddlesden-Popper phases of perovskite chalcogenides are promising materials to achieve single-junction solar cells.Comment: 4 Figure

A Phenomenological Study: African-American Males in the Educational Profession

This phenomenological research study explored the perceptions and lived experiences of African-American male teachers related to the underrepresentation of African-American males in the teaching profession. The study was guided by four research questions. The data was collected from 15 African-American male teachers at the elementary school level, middle school level, high school level, administrator level, and retired level from a school system in southeast Georgia. Data collection occurred through teacher/retired teacher interviews and administrator interviews. The findings of the study showed the reasons for African-American males being underrepresented in the teaching profession is due to (a) low starting salary, (b) lack of eligible candidates, (c) perceived dishonor of the profession, and (4) the lack of positive promotion of the profession. Through the findings, the research study was able to identify four emergent themes aimed at reversing the trend of African-American males being underrepresented in the teaching profession. The factors are: (a) provide monetary/financial incentives, (2) provide positive exposure to the profession, (c) promote the profession in a positive light, and (d) increase community support. The participants expressed a desire for the educational world to fully embrace African-American male teachers and utilize their unique skills and abilities to have a positive impact on the lives of students, especially African-American males. The research study was not without limitations and further research on the topic was recommended

Adapting and testing an evidence-based antiretroviral medication adherence intervention in China

Session presented on: Thursday, July 25, 2013: Purpose: To test the effectiveness of a culturally adapted evidence-based home nursing intervention to improve adherence to antiretroviral medications among people living with HIV/AIDS (PLWH/A) in Hunan, China. Methods: In a randomized, controlled trial, 114 subjects were assigned to receive a culturally adapted intervention consisting of monthly visits and interim phone calls plus standard care or standard care alone. The intervention previously demonstrated efficacy in a randomized clinical trial conducted in the United States. All subjects were residents of Hunan, China, living with HIV/AIDS and self-reporting less than 90% adherence to prescribed medications. Measures included a 7-day visual analogue medication adherence scale, a social support rating scale, the Chinese version of the Center for Epidemiological Studies Depression scale Chinese, and an HIV/AIDS stigma scale. Data were collected in structured face-to-face interviews at baseline, 6 months, and 12 months at the time of a regularly scheduled clinical visit. Information regarding ARV regimen, treatment duration, time of diagnosis, CD4 count and HIV-RNA was extracted from the medical record. Results: Subjects were 72% male (N=82); 52% (N=59) married; and only 28% (N=32) stably employed. Thirty-one percent (N=35) reported past or current drug abuse. The great majority (98%) had a CD4 count at baseline that was less than 350 cells/mm3. At 6 months and 12 months, a greater proportion of subjects in the intervention group self-reported adherence greater than 90% compared to the control group. The difference over time is significant (Extended Mantel-Haenszel Test: 8.8, p=.003). Conclusions: In spite of significant cultural differences, evidence-based interventions can be implemented effectively in new settings and with new populations

Required Sample Size to Detect Mediation in 3-Level Implementation Studies

Background: Statistical tests of mediation are important for advancing implementation science; however, little research has examined the sample sizes needed to detect mediation in 3-level designs (e.g., organization, provider, patient) that are common in implementation research. Using a generalizable Monte Carlo simulation method, this paper examines the sample sizes required to detect mediation in 3-level designs under a range of conditions plausible for implementation studies. Method: Statistical power was estimated for 17,496 3-level mediation designs in which the independent variable (X) resided at the highest cluster level (e.g., organization), the mediator (M) resided at the intermediate nested level (e.g., provider), and the outcome (Y) resided at the lowest nested level (e.g., patient). Designs varied by sample size per level, intraclass correlation coefficients of M and Y, effect sizes of the two paths constituting the indirect (mediation) effect (i.e., X→M and M→Y), and size of the direct effect. Power estimates were generated for all designs using two statistical models—conventional linear multilevel modeling of manifest variables (MVM) and multilevel structural equation modeling (MSEM)—for both 1- and 2-sided hypothesis tests. Results: For 2-sided tests, statistical power to detect mediation was sufficient (≥0.8) in only 463 designs (2.6%) estimated using MVM and 228 designs (1.3%) estimated using MSEM; the minimum number of highest-level units needed to achieve adequate power was 40; the minimum total sample size was 900 observations. For 1-sided tests, 808 designs (4.6%) estimated using MVM and 369 designs (2.1%) estimated using MSEM had adequate power; the minimum number of highest-level units was 20; the minimum total sample was 600. At least one large effect size for either the X→M or M→Y path was necessary to achieve adequate power across all conditions. Conclusions: While our analysis has important limitations, results suggest many of the 3-level mediation designs that can realistically be conducted in implementation research lack statistical power to detect mediation of highest-level independent variables unless effect sizes are large and 40 or more highest-level units are enrolled. We suggest strategies to increase statistical power for multilevel mediation designs and innovations to improve the feasibility of mediation tests in implementation research

Riverine sustainment 2012

Student Integrated ProjectIncludes supplementary materialThis technical report analyzed the Navy's proposed Riverine Force (RF) structure and capabilities for 2012. The Riverine Sustainment 2012 Team (RST) examined the cost and performance of systems of systems which increased RF sustainment in logistically barren environments. RF sustainment was decomposed into its functional areas of supply, repair, and force protection. The functional and physical architectures were developed in parallel and were used to construct an operational architecture for the RF. The RST used mathematical, agent-based and queuing models to analyze various supply, repair and force protection system alternatives. Extraction of modeling data revealed several key insights. Waterborne heavy lift connectors such as the LCU-2000 are vital in the re-supply of the RF when it is operating up river in a non-permissive environment. Airborne heavy lift connectors such as the MV-22 were ineffective and dominated by the waterborne variants in the same environment. Increase in manpower and facilities did appreciable add to the operational availability of the RF. Mean supply response time was the biggest factor effecting operational availability and should be kept below 24 hours to maintain operational availability rates above 80%. Current mortar defenses proposed by the RF are insufficient.N