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

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

Ground State Vortex Lattice Structures in d-wave Superconductors

We show in a realistic $d_{x^{2}-y^{2}}$ symmetry gap model for a cuprate superconductor that the clean vortex lattice has discontinuous structural transitions (at and near T=0), as a function of the magnetic field $B$ along the c-axis. The transitions arise from the singular nonlocal and anisotropic susceptibility of the $d_{x^{2}-y^{2}}$ superconductor to the perturbation caused by supercurrents associated with vortices. The susceptibility, due to virtual Dirac quasiparticle-hole excitation, is calculated carefully, and leads to a ground state transition for the triangular lattice from an orientation along one of the crystal axis to one at 45$^o$ to them, i.e, along the gap zero direction. The field scale is seen to be 5 Tesla $\sim (\Delta_{0}/ta)^{2}\Phi_{0}$, where $\Delta_{0}$ is the gap maximum, $t$ is the nearest neighbour hopping, $a$ is the lattice constant, and $\Phi_{0}$ is the flux quantum. At much higher fields ($\sim 28T$) there is a discontinuous transition to a centred square structure. The source of the differences from existing calculations, and experimental observability are discussed, the latter especially in view of the very small (a few degrees $K$ per vortex) differences in the ground state energy.Comment: To be published in Phys. Rev.

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

Effect of pathology type and severity on the distribution of MRI signal intensities within the degenerated nucleus pulposus: application to idiopathic scoliosis and spondylolisthesis

<p>Abstract</p> <p>Background</p> <p>Disc degeneration is characterized by a loss of cellularity, degradation of the extracellular matrix, and, as a result, morphological changes and biomechanical alterations. We hypothesized that the distribution of the MR signal intensity within the nucleus zone of the intervertebral disc was modified according to the pathology and the severity of the pathology. The objective of this study was to propose new parameters characterizing the distribution of the signal intensity within the nucleus zone of lumbar intervertebral discs, and to quantify these changes in patients suffering from spondylolisthesis or idiopathic scoliosis.</p> <p>Methods</p> <p>A retrospective study had been performed on T2-weighted MR images of twenty nine patients suffering from spondylolisthesis and/or scoliosis. The high intensity zone of the nucleus pulposus was semi-automatically detected. The distance "DX" between the center weighted by the signal intensity and the geometrical center was quantified. The sum of the signal intensity on the axis perpendicular to the longitudinal axis of the disc was plotted for each position of the longitudinal axis allowing defining the maximum sum "SM" and its position "PSM".</p> <p>Results</p> <p>"SM" was clearly higher and "PSM" was more shifted for scoliosis than for spondylolisthesis. A two-way analysis of variance showed that the differences observed on "DX" were not attributed to the pathology nor its severity, the differences observed on "SM" were attributed to the pathology but not to its severity, and the differences observed on "PSM" were attributed to both the pathology and its severity.</p> <p>Conclusions</p> <p>The technique proposed in this study showed significant differences in the distribution of the MR signal intensity within the nucleus zone of intervertebral discs due to the pathology and its severity. The dependence of the "PSM" parameter to the severity of the pathology suggests this parameter as a predictive factor of the pathology progression. This new technique should be useful for the early diagnosis of intervertebral disc pathologies as it highlights abnormal patterns in the MRI signal for low severity of the pathology.</p

Production of benzylisoquinoline alkaloids in Saccharomyces cerevisiae

The benzylisoquinoline alkaloids (BIAs) are a diverse class of metabolites that exhibit a broad range of pharmacological activities and are synthesized through plant biosynthetic pathways comprised of complex enzyme activities and regulatory strategies. We have engineered yeast to produce the key intermediate reticuline and downstream BIA metabolites from a commercially available substrate. An enzyme tuning strategy was implemented that identified activity differences between variants from different plants and determined optimal expression levels. By synthesizing both stereoisomer forms of reticuline and integrating enzyme activities from three plant sources and humans, we demonstrated the synthesis of metabolites in the sanguinarine/berberine and morphinan branches. We also demonstrated that a human P450 enzyme exhibits a novel activity in the conversion of (R)-reticuline to the morphinan alkaloid salutaridine. Our engineered microbial hosts offer access to a rich group of BIA molecules and associated activities that will be further expanded through synthetic chemistry and biology approaches