Minimum aberration designs for discrete choice experiments

A discrete choice experiment (DCE) is a survey method that givesinsight into individual preferences for particular attributes.Traditionally, methods for constructing DCEs focus on identifyingthe individual effect of each attribute (a main effect). However, aninteraction effect between two attributes (a two-factor interaction)better represents real-life trade-offs, and provides us a better understandingof subjects’ competing preferences. In practice it is oftenunknown which two-factor interactions are significant. To address theuncertainty, we propose the use of minimum aberration blockeddesigns to construct DCEs. Such designs maximize the number ofmodels with estimable two-factor interactions in a DCE with two-levelattributes. We further extend the minimum aberration criteria toDCEs with mixed-level attributes and develop some general theoreticalresults

The Treatment of Mental Disorders through Medication

Diagnosis plays a huge role in the successful treatment of mental disorders. Subtle differences in symptoms can lead to different diagnoses, and therefore different prescribed medications. The neurological causes of anxiety, depression, bipolar disorder, and ADHD are examined; as well as the mechanisms of the drugs commonly used to treat them

A feasibility assessment of native ferns for phytoremed[i]ation of arsenic

Arsenic contamination is a world-wide concern. In the past, soil contaminated with arsenic was removed using heavy equipment resulting in the destruction of the environment. However, in recent years a new method, phytoremediation, removes arsenic and maintains the integrity of the environment. Phytoremediation is the use of plants to sequester and remove contaminants. In 2008, water samples from Poplar Cove Creek and Cloer Branch in Macon County, NC (located in the Nantahala National Forest) had levels of arsenic ranging from 13.8 to 20.6 ppb. These results are unusually high for Western North Carolina and are higher than the EPA’s drinking water standard of 10 ppb. This study sought to determine if two native fern species (Polystichum acrostichoides (Christmas Fern) and Thelypteris noveboracensis (New York Fern)) accumulate arsenic and to determine if these ferns might be suitable for phytoremediation of arsenic. In the greenhouse experiment, ferns were planted in soil spiked with arsenic ranging from 0 (control) to 50 ppm. Initial and final samples were taken of fronds, roots/rhizomes, and soil to determine arsenic concentration levels. Results showed no accumulation of arsenic in the fronds of either fern species; however, arsenic accumulated in the roots of both fern species. T. noveboracensis showed a stronger relationship with arsenic in the soil and ability to take up arsenic than did P. acrostichoides. However, despite these positive results, the amount of arsenic taken up by these native ferns was too little to make their use feasible for phytoremediation of arsenic

Efavirenz inhibits the human ether-a-go-go related current (hERG) and induces QT interval prolongation in CYP2B6*6*6 allele carriers

Background Efavirenz (EFV) has been associated with torsade de pointes despite marginal QT interval lengthening. Since EFV is metabolized by the cytochrome P450 (CYP) 2B6 enzyme, we hypothesized that EFV would lengthen the rate-corrected QT (QTcF) interval in carriers of the CYP2B6*6 decreased functional allele. Objective The primary objective of this study was to evaluate EFV-associated QT interval changes with regard to CYP2B6 genotype and to explore mechanisms of QT interval lengthening. Methods EFV was administered to healthy volunteers (n=57) as a single 600 mg dose followed by multiple doses to steady-state. Subjects were genotyped for known CYP2B6 alleles and ECGs and EFV plasma concentrations were obtained serially. Whole-cell, voltage-clamp experiments were performed on cells stably expressing hERG and exposed to EFV in the presence and absence of CYP2B6 expression. Results EFV demonstrated a gene-dose effect and exceeded the FDA criteria for QTcF interval prolongation in CYP2B6*6/*6 carriers. The largest mean time-matched differences ΔΔQTcF were observed at 6 hrs (14 ms; 95% CI [1; 27]), 12 hrs (18 ms; 95% CI [−4; 40] and 18 hrs (6 ms; 95% CI [−1; 14]) in the CYP2B6*6/*6 genotype. EFV concentrations exceeding 0.4 µg/mL significantly inhibited outward hERG tail currents (P<0.05). Conclusions This study demonstrates that homozygous carriers of CYP2B6*6 allele may be at increased risk for EFV-induced QTcF interval prolongation via inhibition of hERG

Contributions in Design of Experiments: Methods and Applications

Progresses in science and technology continuously raise new challenges to experimenters and statisticians, calling for innovation in methodological and theoretical development of experimental design. Factorial designs are popular experimental plans for identifying important factors. Motivated by real world applications, we construct efficient and optimal factorial designs with applications in the fields of, but not limited to, biomedical sciences, for drug combination determination, and marketing survey research. First, we provide a novel application of fractional factorial designs to investigate a biological system with Herpes simplex virus type 1 and six antiviral drugs. We show how the sequential use of two- and three-level fractional factorial designs can screen for important drugs and drug interactions, as well as determine potential optimal drug dosages. Second, we construct a new class of composite designs based on a two-level factorial design and a three-level orthogonal array. These new composite designs have many desirable features and are effective for factor screening and response surface modeling. Finally, motivated by the need for smaller optimal discrete choice experiments, we propose a novel application of blocked factorial designs for designing discrete choice experiments for estimating main effects, and main effects plus some two-factor interactions, with 100% efficiency. These observations have major implications in the under- standing of factorial designs, ultimately leading to a better design practice and theory

Investigating the potential for using structure from motion technology as a tool for improving trail degradation assessment

Traditional trail degradation assessment methods can require time- and labor-intensive fieldwork or technical expertise, and the measurements made often consist of a series of 2D cross-sections. Structure from motion technology could potentially be used to improve the accuracy and efficiency trail degradation assessment by creating highly detailed 3D point clouds from a set of unstructured photos. This thesis assesses the accuracy and precision of measurements made from point clouds produced using Microsoft Geosynth. It was found that using a Canon G10 camera and Trimble GPS unit, width, surface area, volume, and slope measurements made from the point clouds were within 2% of the actual measurements. Change analysis of the DEMs generated, however, revealed problems with tilt. Using structure from motion technology to improve trail degradation assessment shows promise, but requires further research to solve the problems encountered in this study before it can be promoted as a valid methodology

A Comparison of Three Assessment Types on Student Engagement and Content Knowledge in Online Instruction

The research described in this article focuses on determining the effectiveness of Bongo in promoting student retention of concepts in online learning. This study used both quantitative and qualitative measures to examine the effectiveness of student video presentation assignments on student retention of learning and perceptions of the assignment’s contributions to learning. The quantitative methods compared the effects of three treatment conditions (independent reading, Bongo video presentation, and Bongo video presentation with Auto Analysis) on retention of concepts (quizzes administered two weeks after the presentation recordings). Qualitative analysis of student perceptions of the perceived value of Bongo in general, and specifically the Auto Analysis tool, were accomplished through video surveys, transcription, and analysis.  Analysis of the data provided strong support for the use of Bongo to increase student retention of concepts, and also revealed that students held favorable perceptions of the value and utility of the tool.</jats:p