To use or not to use cool superconductors?

The high critical temperature and magnetic field in cuprates and Fe-based superconductors are not enough to assure applications at higher temperatures. Making these superconductors useful involves complex and expensive technologies to address many conflicting physics and materials requirements

Mathematical model describing erythrocyte sedimentation rate. Implications for blood viscosity changes in traumatic shock and crush syndrome

BACKGROUND: The erythrocyte sedimentation rate (ESR) is a simple and inexpensive laboratory test, which is widespread in clinical practice, for assessing the inflammatory or acute response. This work addresses the theoretical and experimental investigation of sedimentation a single and multiple particles in homogeneous and heterogeneous (multiphase) medium, as it relates to their internal structure (aggregation of solid or deformed particles). METHODS: The equation system has been solved numerically. To choose finite analogs of derivatives we used the schemes of directional differences. RESULTS: (1) Our model takes into account the influence of the vessel wall on group aggregation of particles in tubes as well as the effects of rotation of particles, the constraint coefficient, and viscosity of a mixture as a function of the volume fraction. (2) This model can describe ESR as a function of the velocity of adhesion of erythrocytes; (3) Determination of the ESR is best conducted at certain time intervals, i.e. in a series of periods not exceeding 5 minutes each; (4) Differential diagnosis of various diseases by means of ESR should be performed using the aforementioned timed measurement of ESR; (5) An increase in blood viscosity during trauma results from an increase in rouleaux formation and the time-course method of ESR will be useful in patients with trauma, in particular, with traumatic shock and crush syndrome. CONCLUSION: The mathematical model created in this study used the most fundamental differential equations that have ever been derived to estimate ESR. It may further our understanding of its complex mechanism

Modern tests of Lorentz invariance

Motivated by ideas about quantum gravity, a tremendous amount of effort over the past decade has gone into testing Lorentz invariance in various regimes. This review summarizes both the theoretical frameworks for tests of Lorentz invariance and experimental advances that have made new high precision tests possible. The current constraints on Lorentz violating effects from both terrestrial experiments and astrophysical observations are presented.Comment: Modified and expanded discussions of various points. Numerous references added. Version matches that accepted by Living Reviews in Relativit

Analysing laser machined YBCO microbridges using raman spectroscopy and transport measurements aiming to investigate process induced degradation

Machining high temperature superconducting (HTS) thin films is challenging due to the material’s sensitivity. Here, 200 nm thick YBCO microbridges were machined with a femtosecond laser (300 fs at 1030 nm wavelength) as a chemical free and flexible method with minimal edge damage. Transport measurements and Raman spectroscopy were used to analyse the bridges before and after laser processing. While transport and Raman measurements are commonly used separately to evaluate YBCO, our approach links both techniques to analyse laser induced damage. The link between changes in the Raman spectrum and transport measurements is investigated by identifying changes caused by repeated heat treatments while sequentially measuring the critical current density and Raman spectra. The data obtained is used to predict critical current density losses from changes in Raman peak intensities and shifts. This technique is further investigated by applying it to laser machined YBCO bridges which were exposed to highly localised heating. Results show that for bridge widths of 10 μm, a femtosecond laser can be used to repeatedly successfully machine microbridges with no loss in critical current density and that there is some correlation to critical current changes in the Raman spectra.This work was partially supported by the Air Force Research Laboratory - Aerospace Systems Directorate (AFRL/RQ), the Air Force Office of Scientific Research (AFOSR) under contract LRIR #18RQCOR100, and AFOSR/EOARD under contract FA 16I0E050 and the EPSRC (grant number: EP/L016567/1)

Analysing laser machined YBCO microbridges using raman spectroscopy and transport measurements aiming to investigate process induced degradation

Machining high temperature superconducting (HTS) thin films is challenging due to the material's sensitivity. Here, 200 nm thick YBCO microbridges were machined with a femtosecond laser (300 fs at 1030 nm wavelength) as a chemical free and flexible method with minimal edge damage. Transport measurements and Raman spectroscopy were used to analyse the bridges before and after laser processing. While transport and Raman measurements are commonly used separately to evaluate YBCO, our approach links both techniques to analyse laser induced damage. The link between changes in the Raman spectrum and transport measurements is investigated by identifying changes caused by repeated heat treatments while sequentially measuring the critical current density and Raman spectra. The data obtained is used to predict critical current density losses from changes in Raman peak intensities and shifts. This technique is further investigated by applying it to laser machined YBCO bridges which were exposed to highly localised heating. Results show that for bridge widths of 10 μm, a femtosecond laser can be used to repeatedly successfully machine microbridges with no loss in critical current density and that there is some correlation to critical current changes in the Raman spectra

Microwave antenna properties of an optically triggered superconducting ring

We examine the microwave radiation emitted from inductively charged centimeter-scale YBCO (YBa2Cu3O7-δ) annular rings illuminated with a 45 fs, 790 nm laser pulse. The electromagnetic radiation from the rings shows the following behavior. (1) Radiation emitted perpendicular to the plane of the ring is polarized parallel to the plane of the ring and across the point of illumination. (2) The in-plane radiation pattern resembles that of a loop antenna with the orientation of the pattern determined by the location of the illumination point. (3) The dominant frequency of the emitted radiation shows an inverse dependence on the ring diameter. (4) The emitted energy is proportional to energy stored in the ring for a number of different geometries, with thinner films displaying a higher efficiency. Finally, (5) the emitted energy grows exponentially with small laser pulse energy values and approaches saturation for higher energies. These results indicate that optically induced electromagnetic radiation from superconducting structures holds promise for a versatile, compact, self-contained superconducting microwave emitter platform