Student Self-Reported Academic Confidence as an Indicator of First-Year Retention

Many first-year college/university students have low retention and success rates which affect their ability to remain in college and attain a career. Despite matriculation practices employed by institutions of higher learning to increase retention, a gap remains in the understanding of the causative factors of retention. The purpose of this study was to determine if academic self-confidence scores of students prior to entry and post- completion of an FYS are reliable predictors of students\u27 ability to progress from the first year to the second year of college. Tinto\u27s (1987) academic retention theory framed the study. A quantitative case study approach including a paired t-test for the dependent sample analysis, point-biserial correlation analysis, and a one-way analysis of covariance (ANCOVA) was employed for this study. The findings are that students\u27 self-reported academic confidence does improve postcompletion of the FYS and that these results are not gender specific. The statistical analysis of correlation between posttest self-confidence scores and re-enrollment for second year of college were not statistically significant. The findings of this study contribute to the body of knowledge in current literature on factors of retention, specifically students\u27 self-reported academic confidence. When careful investigations are conducted to determine causative factors that can be used as predictors of student retention, those investigations directly impact positive social change and promote accountability for current matriculation practices employed by institutions of higher learning

A Re-Evaluation of the Abundance of Lutetium in the Sun

Lutetium is one of the few nonvolatile elements whose solar photospheric abundance departs significantly from that derived from CI chondrites. We have applied the Cowan code to compute new oscillator strengths for Luii, and have included a correction for core polarization. The results have been used in a synthesis of the solar spectrum in the vicinity of features at 3397.062 and 6221.72. We find that the majority of the absorption in the ultraviolet feature is due to NH, making it unsuitable for extracting a reliable lutetium abundance. Our best fit to the low-noise Jungfraujoch spectrum for the weak, nine-component hyperfine Luii line at λ 6221.87 yields an abundance of +0.06 on a scale where log(H) = 12.00. This value is within 0.07 dex of the meteoritic result (+0.13). (These figures reflect the note added in proof below.)Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43714/1/11207_2004_Article_146254.pd

Computational Study of the Human Dystrophin Repeats: Interaction Properties and Molecular Dynamics

Dystrophin is a large protein involved in the rare genetic disease Duchenne muscular dystrophy (DMD). It functions as a mechanical linker between the cytoskeleton and the sarcolemma, and is able to resist shear stresses during muscle activity. In all, 75% of the dystrophin molecule consists of a large central rod domain made up of 24 repeat units that share high structural homology with spectrin-like repeats. However, in the absence of any high-resolution structure of these repeats, the molecular basis of dystrophin central domain's functions has not yet been deciphered. In this context, we have performed a computational study of the whole dystrophin central rod domain based on the rational homology modeling of successive and overlapping tandem repeats and the analysis of their surface properties. Each tandem repeat has very specific surface properties that make it unique. However, the repeats share enough electrostatic-surface similarities to be grouped into four separate clusters. Molecular dynamics simulations of four representative tandem repeats reveal specific flexibility or bending properties depending on the repeat sequence. We thus suggest that the dystrophin central rod domain is constituted of seven biologically relevant sub-domains. Our results provide evidence for the role of the dystrophin central rod domain as a scaffold platform with a wide range of surface features and biophysical properties allowing it to interact with its various known partners such as proteins and membrane lipids. This new integrative view is strongly supported by the previous experimental works that investigated the isolated domains and the observed heterogeneity of the severity of dystrophin related pathologies, especially Becker muscular dystrophy

Figure 9: Alternative representations of the Ramachandran plot.

The Ramachandran plot is important to structural biology as it describes a peptide backbone in the context of its dominant degrees of freedom—the backbone dihedral angles φ and ψ (Ramachandran, Ramakrishnan & Sasisekharan, 1963). Since its introduction, the Ramachandran plot has been a crucial tool to characterize protein backbone features. However, the conformation or twist of a backbone as a function of φ and ψ has not been completely described for both cis and trans backbones. Additionally, little intuitive understanding is available about a peptide’s conformation simply from knowing the φ and ψ values of a peptide (e.g., is the regular peptide defined by φ = ψ =  − 100°  left-handed or right-handed?). This report provides a new metric for backbone handedness (h) based on interpreting a peptide backbone as a helix with axial displacement d and angular displacement θ, both of which are derived from a peptide backbone’s internal coordinates, especially dihedral angles φ, ψ and ω. In particular, h equals sin(θ)d∕|d|, with range [−1, 1] and negative (or positive) values indicating left(or right)-handedness. The metric h is used to characterize the handedness of every region of the Ramachandran plot for both cis (ω = 0°) and trans (ω = 180°) backbones, which provides the first exhaustive survey of twist handedness in Ramachandran (φ, ψ) space. These maps fill in the ‘dead space’ within the Ramachandran plot, which are regions that are not commonly accessed by structured proteins, but which may be accessible to intrinsically disordered proteins, short peptide fragments, and protein mimics such as peptoids. Finally, building on the work of (Zacharias & Knapp, 2013), this report presents a new plot based on d and θ that serves as a universal and intuitive alternative to the Ramachandran plot. The universality arises from the fact that the co-inhabitants of such a plot include every possible peptide backbone including cis and trans backbones. The intuitiveness arises from the fact that d and θ provide, at a glance, numerous aspects of the backbone including compactness, handedness, and planarity

Techniques to Characterize Vapor Cell Performance for a Nuclear-Magnetic-Resonance Gyroscope

Research was performed to improve the procedures for testing performance parameters of vapor cells for a nuclear-magnetic-resonance gyroscope. In addition to summarizing the theoretical infrastructure of the technology, this research resulted in the development and successful implementation of new techniques to characterize gyro cell performance. One of the most important parameters to measure for gyro performance is the longitudinal spin lifetime of polarized xenon atoms in the vapor cell. The newly implemented technique for measuring these lifetimes matches results from the industry standard method to within 3.5% error while reducing the average testing time by 76% and increasing data resolution by 54%. The vapor cell test methods were appended with new software to expedite the analysis of test data and to investigate more subtle details of the results; one of the two isotopes of xenon in the cells tends to exhibit troublesome second-order effects during these tests due to electric-quadrupole coupling, but now the added analysis capabilities can accurately extract relevant results from such data with no extra effort. Some extraneous lifetime measurement techniques were explored with less substantial results, but they provided useful insight into the complex workings of the gyro cell test system. New criteria were established to define the signal to noise ratio on a consistent basis from cell to cell across various parameters such as cell volume, temperature, and vapor pressure. A technique for measuring gas pressures inside the sealed cells helped link cell performance to cell development processes. This led to informed decisions on filling and sealing methods that consistently yielded cells with better performance in the last few months of this work. When this research began, cells with xenon lifetimes over ten seconds were rare in our lab; by the end, anything under 30 seconds was a disappointment. Not only did the test procedures improve, but so did the parameters being tested, and quite significantly at that. At the same time, many new avenues for continued progress have been opened; the work presented here, while instrumental, is only the beginning

Unique elastic properties of the spectrin tetramer as revealed by multiscale coarse-grained modeling

The force-extension profile of tetrameric spectrin is determined by using multiscale computer simulation. Fluctuation results of atomistic simulations of double spectrin repeat units (DSRU) are used to systematically build a coarse-grained (CG) model for the tetrameric form of spectrin. It is found that the spectrin tetramer can be modeled as a soft polymer with a unique flat force-extension profile over the range of biologically important lengths. It is also concluded that in the cytoskeletal network of the red blood cell the tetramer is in an “overcompressed” state. These findings are in contrast to the commonly used models of spectrin tetramer elasticity, namely the “entropic spring” polymer models. From these results, it is concluded that stable intact helical linker regions are needed to maintain the soft elasticity of the spectrin tetramer