Observation of a Triangular to Square Flux Lattice Phase Transition in YBCO

We have used the technique of small-angle neutron scattering to observe magnetic flux lines directly in an YBCO single crystal at fields higher than previously reported. For field directions close to perpendicular to the CuO2 planes, we find that the flux lattice structure changes smoothly from a distorted triangular co-ordination to nearly perfectly square as the magnetic induction approaches 11 T. The orientation of the square flux lattice is as expected from recent d-wave theories, but is 45 deg from that recently observed in LSCO

Bioimpedance Spectroscopy Compared to Ultrasound-derived Measures of Quadriceps Muscle Quality

Muscle quality is often measured using ultrasound-derived echo intensity (EI). Recent works have shown tissue frequency-dependent electrical impedance from bioimpedance spectroscopy may be a modality for assessing tissue quality. PURPOSE: The purpose of the project was to examine the association between ultrasound-derived EI of the quadriceps muscles (i.e., vastus lateralis [VL], vastus medialis [VM], vastus intermedius [VI], rectus femoris [RF]) and measures of thigh tissue frequency-dependent electrical impedance (i.e., R0, R1, C, a, fp). METHODS: Twenty-four participants (13 women; mean ± SD; age: 22 ± 4 years; BMI: 25.47 ± 3.26 kg/m2) were recruited. Participants completed one laboratory visit where quadriceps tissue quality was assessed via ultrasound and bioimpedance spectroscopy (BIS). Participants laid supine on a portable exam table to undergo imaging of the dominant leg VL using ultrasound in conjunction with a multi-frequency linear array probe (L4 – 12t – RS, 4.2-13 MHz, 47.1mm field of view). The VL was marked at the proximal and distal musculo-tendon junctions determined via ultrasound and the length was measured with a tape measure. Participants had cross-sectional scans of the VM, VL, VI, and RF at 25, 50, 75% of the length of the VL. Images were analyzed using the polygon tool in ImageJ to trace the muscles and provide EI values. Subcutaneous fat width was measured using the straight-line tool. Echo intensity was calculated using ImageJ gray-scale analysis and histogram function as well as corrected for subcutaneous fat. For statistical analyses, the average corrected EI for each muscle was created across scan sites. For BIS, participants were seated in a chair with Ag/AgCl electrodes placed above the patella and below the hip. Electrodes were placed 6cm apart and the Cole-impedance model was used to represent frequency-dependent thigh tissue data. Signals were analyzed using a custom-written software program. Pearson’s correlation coefficient (r) was used to determined associations between the VL, VM, VI, RF and BIS variables (R0, R1, C, a, fp). An alpha level of p ≤ 0.05 determined statistical significance. RESULTS: The results suggest that VL, VM, VI and RF echo intensity was significantly related to R0 (r = 0.65 – 0.81; p \u3c 0.01). For VI and RF, they were significantly related to a (r = -0.51 – -0.50; p = 0.01), but not for VL or VM (r = -0.39 - -0.22; p \u3e 0.06). Lastly, R1, C, and fp were not significantly correlated to the quadriceps muscles (r = -0.38 – 0.33; p \u3e 0.07). CONCLUSION: Our findings suggest that BIS-derived R0 may be a metric of muscle quality of the quadriceps as it was significantly related to ultrasound-derived measures of echo intensity of the VL, VM, VI, and RF. Further investigation of other muscle groups may be warranted

Phenomenological theory of the 3 Kelvin phase in Sr2RuO4

We model the 3K-phase of Sr2RuO4 with Ru-metal inclusion as interface state with locally enhanced transition temperatures. The resulting 3K-phase must have a different pairing symmetry than the bulk phase of Sr2RuO4, because the symmetry at the interface is lower than in the bulk. It is invariant under time reversal and a second transition, in general, above the onset of bulk superconductivity is expected where time reversal symmetry is broken. The nucleation of the 3K-phase exhibits a ``capillary effect'' which can lead to frustration phenomena for the superconducting states on different Ru-inclusions. Furthermore, the phase structure of the pair wave function gives rise to zero-energy quasiparticle states which would be visible in quasiparticle tunneling spectra. Additional characteristic properties are associated with the upper critical field Hc2. The 3K-phase has a weaker anisotropy of Hc2 between the inplane and z-axis orientation than the bulk superconducting phase. This is connected with the more isotropic nature Ru-metal which yields a stronger orbital depairing effect for the inplane magnetic field than in the strongly layered Sr$_2RuO4. An anomalous temperature dependence for the z-axis critical field is found due to the coupling of the magnetic field to the order parameter texture at the interface. Various other experiments are discussed and new measurements are suggested.Comment: 10 pages, 5 figure

Flux-Line Lattice Structures in Untwinned YBa2Cu3O

A small angle neutron scattering study of the flux-line lattice in a large single crystal of untwinned YBa2Cu3O is presented. In fields parallel to the c-axis, diffraction spots are observed corresponding to four orientations of a hexagonal lattice, distorted by the a-b anisotropy. A value for the anisotropy, the penetration depth ratio, of 1.18(2) was obtained. The high quality of the data is such that second order diffraction is observed, indicating a well ordered FLL. With the field at 33 degrees to c a field dependent re-orientation of the lattice is observed around 3T.Comment: 4 pages, 4 figure

Body Composition and Anthropometric Changes During a 10-week Training Academy in Police Recruits

Obesity and cardiometabolic risk factors are often present in law enforcement personnel, which may compromise physical readiness and long-term health. As such, physical fitness interventions are warranted for promoting officers\u27 performance and wellbeing. PURPOSE: To determine the body composition and anthropometric changes experienced by police recruits undergoing a departmental training academy. METHODS: Twenty-one police recruits (20 M, 1 F; age: 25.1 ± 5.0 y; BMI: 27.8 ± 4.3 kg/m2) were tested before and after a 10-week training academy in Lubbock, Texas. Supervised physical training was conducted 5 times per week and consisted of ~1–1.5 hours of high-intensity, multi-modal (i.e., running, weightlifting, calisthenics), functional training following linear periodization. Dual-energy X-ray absorptiometry (DXA; GE Lunar iDXA) and 3-dimensional optical imaging (3DO; Size Stream SS20) were performed to assess body composition and anthropometry. Paired-samples t-tests were performed to compare values before and after the training academy, and Cohen’s d effect sizes were generated. After Bonferroni correction, statistical significance was accepted at p\u3c0.003. Changes are presented as mean ± SD. RESULTS: From DXA, statistically significant decreases in total fat mass (FM; -3.3 ± 3.1 kg, p\u3c0.001, d=1.1), trunk FM (-2.1 ± 2.2 kg, p\u3c0.001, d=1.0), arms FM (-0.3 ± 0.3 kg, p=0.001, d=1.1), legs FM (-0.9 ± 0.9 kg, p\u3c0.001, d=1.1), and body fat percentage (-3.1 ± 2.5%, p\u3c0.001, d=1.2) were observed. Increases in total lean soft tissue (LST; 1.3 ± 1.3 kg, p=0.002, d=1.0) and trunk LST (0.8 ± 0.9 kg, p\u3c0.001, d=0.9) were also noted, with trends for increases in leg LST (0.2 ± 0.7 kg, p=0.096, d=0.4) and arm LST (0.2 ± 0.4, p=0.04, d=0.5). Decreases in 3DO abdomen circumference (-3.5 ± 3.8 cm, p\u3c0.001, d=0.9) and hip circumference (-2.2 ± 2.2 cm, p\u3c0.001, d=1.0) were noted, with trends for decreases in the circumferences of the waist (-2.4 ± 3.6 cm, p=0.007, d=0.7) and upper arm (-0.9 ± 1.5 cm, p=0.02, d=0.6). No significant changes in thigh circumference (-0.7 ± 1.9 cm, p=0.12, d=0.4) or calf circumference (-0.2 ± 1.5 cm, p=0.52, d=0.1) were noted. A trend for a decrease in body mass (-2.0 ± 3.1 kg, p=0.007, d=0.7) was also observed. CONCLUSION: The present study indicates that police academy training significantly improves recruits\u27 body composition, both reducing FM and increasing LST, which has the potential to positively affect operational performance. Future studies should track these changes over time to help develop ongoing health and fitness strategies for career police officers, ultimately improving their long-term wellbeing and job readiness

Interface superconductivity in the eutectic Sr2RuO4-Ru: 3-K phase of Sr2RuO4

The eutectic system Sr2RuO4-Ru is referred to as the 3-K phase of the spin-triplet supeconductor Sr2RuO4 because of its enhanced superconducting transition temperature Tc of ~3 K. We have investigated the field-temperature (H-T) phase diagram of the 3-K phase for fields parallel and perpendicular to the ab-plane of Sr2RuO4, using out-of-plane resistivity measurements. We have found an upturn curvature in the Hc2(T) curve for H // c, and a rather gradual temperature dependence of Hc2 close to Tc for both H // ab and H // c. We have also investigated the dependence of Hc2 on the angle between the field and the ab-plane at several temperatures. Fitting the Ginzburg-Landau effective-mass model apparently fails to reproduce the angle dependence, particularly near H // c and at low temperatures. We propose that all of these charecteric features can be explained, at least in a qualitative fashion, on the basis of a theory by Sigrist and Monien that assumes surface superconductivity with a two-component order parameter occurring at the interface between Sr2RuO4 and Ru inclusions. This provides evidence of the chiral state postulated for the 1.5-K phase by several experiments.Comment: 7 pages and 5 figs; accepted for publication in Phys. Rev.

Low temperature electronic properties of Sr_2RuO_4 III: Magnetic fields

Based on the microscopic model introduced previously the observed specific heat and ac-susceptibility data in the superconducting phase in Sr_2RuO_4 with applied magnetic fields are described consistently within a phenomenological approach. Discussed in detail are the temperature dependence of the upper critical fields H_{c2} and H_2, the dependence of the upper critical fields on the field direction, the linear specific heat below the superconducting phase transition as a function of field or temperature, the anisotropy of the two spatial components of the order parameter, and the fluctuation field H_p.Comment: 8 pages REVTEX, 4 figure