Characterizing and Modeling the Experience of Transfer Students in Engineering—Progress on NSF Award 0969474

Characterizing and Modeling the Experience of Transfer Students in Engineering— Progress on NSF Award 0969474Quantitative analysis of MIDFIELD databaseOur analysis used records for 94,732 undergraduate students from the Multiple-InstitutionDatabase for Investigating Engineering Longitudinal Development (MIDFIELD). MIDFIELDcomprises a census of undergraduate students who attended 11 public institutions between 1988and 2008. MIDFIELD institutions represent public universities that educate large numbers ofengineering students.From the 977,950 records available, we restricted our sample to those who (1) were domesticstudents (927,350), (2) were in the data set early enough for us to observe the possibility ofgraduation within six years (677,691), and (3) declared a major in engineering or otherwiseexpressed the intent to study engineering in the fifth semester of their programs (94,732). Fortransfer students, we estimated placement using transfer hours, assuming that 15 credit hoursequals one semester; we also used the fifth semester as the reference point to capture mosttransfer students at the point of matriculation to ensure a valid comparison of transfers to non-transfers. This approach resulted in a sample of 21,542 transfer and 73,190 non-transferengineering students included in this analysis.Semi-structured interviewsCampus representatives at two MIDFIELD institutions sent an invitation to all engineeringstudents who had transferred into the institution in the two semesters preceding the semester ofthe interview. Interested students completed a survey to provide demographic and schedulinginformation. Participants were chosen from six engineering majors - civil, chemical, computer,electrical, industrial, and mechanical - and were diverse with respect to gender and ethnicity.Selected students were interviewed in Fall 2011 and in Spring 2012.We used a semi-structured interview protocol to learn more about student experiences with thetransfer process. We used a constant comparative coding method, whereby emerging conceptswere constantly compared to data that had already been coded.Overview of Progress Identifying and Describing the Entry Points into Engineering Transfer Pathways: A preliminary study relied on 52 of the 86 students who were interviewed across five campuses to understand their reasons for choosing engineering as a field of studies and the transfer pathway to enter the field. Studying the Motivations and Experiences of Older Transfer Students in Engineering: Of the 86 students who were interviewed on the five campuses, the 15 students who were 25 years of age or older at the time of the interview were selected for this study. Studying the Performance of Black transfer students: based on a logistic regression model refined to include transfer pathway (2-year vs. 4-year), we learned that: Studying the Mean Grade Differential by Course Discipline: For engineering transfer and first-time-in-college (FTIC) students, we computed average grades in STEM courses by discipline, and by institution

Degenerate ground state and anomalous flux hysteresis in an YBa2Cu3O7 grain boundary r.f. SQUID

We report measurements of the flux hysteresis curves and trapped flux distribution in an YBa2Cu3O7 r.f. SQUID containing two closely spaced grain boundary Josephson junctions in parallel. Broadening of the flux distribution from T = 15 K to 30 K is followed by a bifurcation at T = 35 K which corresponds to a degenerate ground state. Above T ~ 40 K the bifurcation disappears, the flux distribution narrows significantly and small secondary loops appear in the hysteresis curves. This behaviour can be modelled qualitatively if we assume a temperature dependent second harmonic term in the current-phase relationship of the junctions.Comment: 10 pages, 7 figure

Flux-flow in d-wave superconductors: Low temperature universality and scaling

We demonstrate that superclean d-wave superconductors display a novel type of vortex dynamics: At low temperatures, both dissipative and transverse components of the flux-flow conductivity are found to approach universal values even in the limit of infinite relaxation time. A finite dissipation in the superclean limit is explained in terms of the Landau damping on zero-frequency vortex modes which appear due to minigap nodes in the bound-state spectrum in the vortex core. In the moderately clean regime the scaling law at low T and low field is obtained.Comment: RevTex file, 4 pages, no figures, submitted to Phys. Rev. Lett., revised after referee report

Macroscopic Symmetry Group Describes Josephson Tunneling in Twinned Crystals

A macroscopic symmetry group describing the superconducting state of an orthorhombically twinned crystal of YBCO is introduced. This macroscopic symmetry group is different for different symmetries of twin boundaries. Josephson tunneling experiments performed on twinned crystals of YBCO determine this macroscopic symmetry group and hence determine the twin boundary symmetry (but do not experimentally determine whether the microscopic order parameter is primarily d- or s-wave). A consequence of the odd-symmetry twin boundaries in YBCO is the stability of vortices containing one half an elementary flux quantum at the intersection of a twin boundary and certain grain boundaries.Comment: 6 pages, to be published in the Proceedings of the MOS96 Conference in the Journal of Low Temperature Physic

Mesoscopic Superconducting Disc with Short-Range Columnar Defects

Short-range columnar defects essentially influence the magnetic properties of a mesoscopic superconducting disc.They help the penetration of vortices into the sample, thereby decrease the sample magnetization and reduce the upper critical field. Even the presence of weak defects split a giant vortex state (usually appearing in a clean disc in the vicinity of the transition to a normal state) into a number of vortices with smaller topological charges. In a disc with a sufficient number of strong enough defects vortices are always placed onto defects. The presence of defects lead to the appearance of additional magnetization jumps related to the redistribution of vortices which are already present on the defects and not to the penetration of new vortices.Comment: 14 pgs. RevTex, typos and figures corrected. Submitted to Phys. Rev.

Electronic states on a twin boundary of a d-wave superconductor

We show that an induced $s$-wave harmonic in the superconducting gap of an orthorhombic $d_{x^2-y^2}$ superconductor strongly affects the excitation spectrum near a twinning plane. In particular, it yields bound states of zero energy with areal density proportional to the relative weight of the $s$-wave component. An unusual scattering process responsible for the thermal conductivity across the twin boundary at low temperatures is also identified.Comment: 4 pages, ReVTEX, 2 PS-figure

Antiferromagnetic Interactions and the Superconducting Gap Function

Spin-fluctuation-mediated superconductivity is conventionally associated with d_{x^2-y^2} pairing. We show that a generalized model of antiferromagnetic spin fluctuations in three dimensions may also yield a state with formal ``s-wave'' (A_{1g}) symmetry but with line nodes at k_z \approx \pm \pi / 2c. We study this new state within both BCS and Eliashberg theories using a realistic band structure and find that it is more stable than the d_{x^2-y^2} (B_{1g}) state over a wide range of parameters. Thus, models of spin-fluctuation-mediated superconductivity must consider both possibilities on an equal footing.Comment: 4 pages, RevTeX with psfig, 2 PostScript figures included in compressed form, one color PostScript figure available by request to [email protected] or [email protected]. Minor changes and updated references from original postin

Critical Behavior of the Flux-line Tension in Extreme Type-II Superconductors

The entropic corrections to the flux-line energy of extreme type-II superconductors are computed using a schematic dual Villain model description of the flux quanta. We find that the temperature profile of the lower-critical field vanishes polynomially at the transition with an exponent $\nu\cong 2/3$ in the isotropic case, while it exhibits an inflection point for the case of weakly coupled layers in parallel magnetic field. It is argued that vestiges of these effects have already been observed in high-temperature superconductors.Comment: 12 pages of plain TeX, 2 postscipt figures, to appear in Phys. Rev.

Capillary Density of Skeletal Muscle: A Contributing Mechanism for Exercise Intolerance in Class II–III Chronic Heart Failure Independent of Other Peripheral Alterations

AbstractOBJECTIVESThe study was conducted to determine if the capillary density of skeletal muscle is a potential contributor to exercise intolerance in class II–III chronic heart failure (CHF).BACKGROUNDPrevious studies suggest that abnormalities in skeletal muscle histology, contractile protein content and enzymology contribute to exercise intolerance in CHF.METHODSThe present study examined skeletal muscle biopsies from 22 male patients with CHF compared with 10 age-matched normal male control patients. Aerobic capacities, myosin heavy chain (MHC) isoforms, enzymes, and capillary density were measured.RESULTSThe patients with CHF demonstrated a reduced peak oxygen consumption when compared to controls (15.0 ± 2.5 vs. 19.8 ± 5.0 ml·kg−1·min−1, p <0.05). Using cell-specific antibodies to directly assess vascular density, there was a reduction in capillary density in CHF measured as the number of endothelial cells/fiber (1.42 ± 0.28 vs. 1.74 ± 0.35, p = 0.02). In CHF, capillary density was inversely related to maximal oxygen consumption (r = 0.479, p = 0.02). The MHC IIx isoform was found to be higher in patients with CHF versus normal subjects (28.5 ± 13.6 vs. 19.5 ± 9.4, p <0.05).CONCLUSIONSThere was a significant reduction in microvascular density in patients with CHF compared with the control group, without major differences in other usual histologic and biochemical aerobic markers. The inverse relationship with peak oxygen consumption seen in the CHF group suggests that a reduction in microvascular density of skeletal muscle may precede other skeletal muscle alterations and play a critical role in the exercise intolerance characteristic of patients with CHF

Nonlinear Magneto-Optical Response of ss- and dd-Wave Superconductors

The nonlinear magneto-optical response of $s$- and $d$-wave superconductors is discussed. We carry out the symmetry analysis of the nonlinear magneto-optical susceptibility in the superconducting state. Due to the surface sensitivity of the nonlinear optical response for systems with bulk inversion symmetry, we perform a group theoretical classification of the superconducting order parameter close to a surface. For the first time, the mixing of singlet and triplet pairing states induced by spin-orbit coupling is systematically taken into account. We show that the interference of singlet and triplet pairing states leads to an observable contribution of the nonlinear magneto-optical Kerr effect. This effect is not only sensitive to the anisotropy of the gap function but also to the symmetry itself. In view of the current discussion of the order parameter symmetry of High-T$_c$ superconductors, results for a tetragonal system with bulk singlet pairing for various pairing symmetries are discussed.Comment: 21 pages (REVTeX) with 8 figures (Postscript