Early-year undergraduate research experiences: How students are mentored, how valuable they find this experience, and what kinds of costs they associate with it

Undergraduate research has been considered as a high impact practice. Engaging in research in early college years are crucial to attracting and retaining students in research-related STEM careers. However, undergraduate research literature mostly focuses on the research experiences of students that are later in their undergraduate years. This dissertation is formed in an article-style format, which is a compilation of two separate research efforts to explore undergraduate students’ research experiences in their freshman and sophomore years. This article-style dissertation is part of a larger investigation into the academic and social experiences of high-achieving low-income undergraduate students. The context of the studies in this dissertation was the National Science Foundation [NSF] funded the Strategic Undergraduate STEM Talent Acceleration INitiative [SUSTAIN] project and the twenty-four undergraduate researchers who participated in the project. Chapter 1 provides an introduction that discusses the need for studying students’ early-year undergraduate research experience and explains the structure of the dissertation. Chapters 2 and 3 each present a complete study with an introduction, literature review, method, results, and discussion. Chapter 2 includes a qualitative investigation of the mentoring structures and the types of support provided to early-year undergraduate researchers. The types of support participants received revealed differences in mentoring dyad or triad structure, as well as the amount of their research experience. Given the potential benefits to undergraduate researchers, undergraduate research programs should be designed to provide clear roles, responsibilities, and expectations from mentors to maximize the support provided to students. Chapter 3 is an exploratory study that utilizes the expectancy-value theory to investigate how much and in what ways early-year undergraduate researchers value their research experience, and which costs they associate with it. Results indicated that intrinsic value and opportunity cost played the most important role in students\u27 motivation to engage in research. This study contributes to the literature by providing preliminary evidence of the range of possible student experiences about the values and costs students associate with their research experience and identifies the most promising avenues for future studies to find ways to improve undergraduate research programs. Collectively, the studies in this dissertation help us better understand early-year undergraduate research experience from students’ perspectives

Censoring Distances Based on Labeled Cortical Distance Maps in Cortical Morphometry

Shape differences are manifested in cortical structures due to neuropsychiatric disorders. Such differences can be measured by labeled cortical distance mapping (LCDM) which characterizes the morphometry of the laminar cortical mantle of cortical structures. LCDM data consist of signed distances of gray matter (GM) voxels with respect to GM/white matter (WM) surface. Volumes and descriptive measures (such as means and variances) for each subject and the pooled distances provide the morphometric differences between diagnostic groups, but they do not reveal all the morphometric information contained in LCDM distances. To extract more information from LCDM data, censoring of the distances is introduced. For censoring of LCDM distances, the range of LCDM distances is partitioned at a fixed increment size; and at each censoring step, and distances not exceeding the censoring distance are kept. Censored LCDM distances inherit the advantages of the pooled distances. Furthermore, the analysis of censored distances provides information about the location of morphometric differences which cannot be obtained from the pooled distances. However, at each step, the censored distances aggregate, which might confound the results. The influence of data aggregation is investigated with an extensive Monte Carlo simulation analysis and it is demonstrated that this influence is negligible. As an illustrative example, GM of ventral medial prefrontal cortices (VMPFCs) of subjects with major depressive disorder (MDD), subjects at high risk (HR) of MDD, and healthy control (Ctrl) subjects are used. A significant reduction in laminar thickness of the VMPFC and perhaps shrinkage in MDD and HR subjects is observed when compared to Ctrl subjects. The methodology is also applicable to LCDM-based morphometric measures of other cortical structures affected by disease.Comment: 25 pages, 10 figure

1H-magnetic resonance spectroscopy in first episode and chronic schizophrenia patients

Background/aim: The aim of this study was to compare metabolite levels of the dorsolateral prefrontal cortex (DLPFC), anterior cingulate gyrus (ACG), thalamus, and hippocampus in patients with chronic schizophrenia (CSPs) and first psychotic episode patients (FEPs) by the use of magnetic resonance spectroscopy (MRS). Materials and methods: Thirty CSPs, 20 FEPs, and 30 healthy subjects participated in this study. N-Acetylaspartate (NAA), creatine, choline (Cho), and myoinositol levels of the DLPFC, ACG, thalamus, and hippocampus were measured by 1H-MRS. Results: It was determined that the NAA/Cho ratio was lower in both the FEPs and CSPs than the healthy controls in the DLPFC. DLPFC Cho levels were also higher in CSPs than healthy controls. NAA levels in CSPs were significantly lower than in the control group in the hippocampus. There was no significant difference in neurometabolite levels and ratios in the ACG and thalamus between the groups. Conclusion: This study supports neuronal dysfunction or loss of neuronal integrity in the DLPFC and hippocampus in CSPs. FEPs showed less neuronal dysfunction in the DLPFC, but not in the hippocampus. Our results suggest that schizophrenic patients show brain metabolic changes with the onset of the disorder in the DLPFC; these changes could be more apparent in the hippocampus as the disease progresses to chronic stages. © TÜBİTAK

Accelerated aging effects on color and translucency of flowable composites

OBJECTIVES: To evaluate the effect of accelerated aging on color and translucency parameter of composites. MATERIALS AND METHODS: Filtek Supreme Ultra Flowable, shades A1, A3, White, Tetric EvoFlow, shades A1, A3, Bleach, and Filtek Z250 shades A1, A3, B1 were evaluated. Color and translucency were recorded using a spectrophotometer after 24-hour storage (baseline) and after accelerated aging. The data were analyzed by analysis of variance. RESULTS: Fisher\u27s PLSD intervals for comparisons among products and shades were 0.4, 0.1, 0.3, and 0.4 for ΔL*, Δa*, Δb*, and ΔE*, respectively. The data showed significant ΔE* and ΔL* main effects for composite product and shades (p \u3c 0.001) and their interactions (p = 0.008 and p = 0.03), respectively. Tetric EvoFlow displayed the smallest aging-dependent color shift followed by Filtek Z250 and Filtek Supreme Ultra Flowable. Accelerated aging did not significantly affected the composites for translucency (p \u3e 0.05). CONCLUSION: The effects of aging on color of resin composites were composite and shade dependent. Translucency was not affected by accelerated aging. CLINICAL SIGNIFICANCE: The effects of aging on color of resin composites were composite and shade dependent

Open string theory and planar algebras

In this note we show that abstract planar algebras are algebras over the topological operad of moduli spaces of stable maps with Lagrangian boundary conditions, which in the case of the projective line are described in terms of real rational functions. These moduli spaces appear naturally in the formulation of open string theory on the projective line. We also show two geometric ways to obtain planar algebras from real algebraic geometry, one based on string topology and one on Gromov-Witten theory. In particular, through the well known relation between planar algebras and subfactors, these results establish a connection between open string theory, real algebraic geometry, and subfactors of von Neumann algebras.Comment: 13 pages, LaTeX, 7 eps figure

Antibacterial, antioxidant and anti-proliferative properties and zinc content of five south Portugal herbs

Context: Crataegus monogyna L. (Rosaceae) (CM), Equisetum telmateia L. (Equisataceae) (ET), Geranium purpureum Vil. (Geraniaceae) (GP), Mentha suaveolens Ehrh. (Lamiaceae) (MS), and Lavandula stoechas L. spp. luisieri (Lamiaceae) (LS) are all medicinal. Objective: To evaluate the antioxidant, antiproliferative and antimicrobial activities of plant extracts and quantify individual phenolics and zinc. Material and methods: Aerial part extracts were prepared with water (W), ethanol (E) and an 80% mixture (80EW). Antioxidant activity was measured with TAA, FRAP and RP methods. Phenolics were quantified with a HPLC. Zinc was quantified using voltammetry. Antibacterial activity (after 48 h) was tested using Enterococcus faecalis, Bacillus cereus, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Listeria monocytogenes. Antiproliferative activity (after 24 h) was tested using HEP G2 cells and fibroblasts. Results: Solvents influenced results; the best were E and 80EW. GP had the highest antioxidant activity (TAA and FRAP of 536.90mg AAE/g dw and 783.48mg TE/g dw, respectively). CM had the highest zinc concentration (37.21 mg/kg) and phenolic variety, with neochlorogenic acid as the most abundant (92.91 mg/100 g dw). LS was rich in rosmarinic acid (301.71 mg/100 g dw). GP and LS inhibited the most microorganisms: B. cereus, E. coli and S. aureus. GP also inhibited E. faecalis. CM had the lowest MIC: 5830 mu g/mL. The antibacterial activity is explained by the phenolics present. LS and CM showed the most significant anti-proliferative activity, which is explained by their zinc content. Conclusion: The most promising plants for further studies are CM, LS and GP.FCT, Fundacao para a Ciencia e a Tecnologia of Portugal [SFRH/BSA/139/2014

Effect of Air Injection on Nucleation Rates: An Approach from Induction Time Statistics

From disruption of the supersaturated solution to improved mass transfer in the crystallizing suspension, the introduction of a moving gas phase in a crystallizer could lead to improved rates of nucleation and crystal growth. In this work, saturated air has been injected to batch crystallizers to study the effects on formation of the first crystal and subsequent turbidity buildup. To account for the typically large sample-to-sample variation, nucleation rates were evaluated for a large number of replicates using probability distributions of induction times. The slope and the intercept of the distributions were studied independently, allowing the simultaneous determination of the mean induction time and a certain detection delay related to the rate of crystal growth after formation of the first nucleus. When saturated air was injected in aqueous glycine solutions, the average detection delay was reduced from 69 to 13 min, and the mean induction time decreased from 128 to 36 min. The effect on aqueous solutions of l-arginine was less apparent, with a detection delay reduction from 15 to 3 min, and no significant changes on the rate of primary nucleation. These results demonstrate the potential of this technique for reduction in nucleation induction time and improved mass deposition rates in crystallization operations