Majorana Edge Modes of Superfluid 3He A-?and?B-Phases

Motivated by a recent experiment on the superfluid ³He confined in a thin slab, we discuss the Majorana edge modes under the experimental situation. We solve the quasi-classical Eilenberger equation, which is quantitatively reliable, to evaluate several observables, such as local density of states, mass current for the A-phase, and spin current for the B-phase. On the basis of the quantitative calculation, we propose several experiments to check the existence of the Majorana modes.     

Influence of Boron Doping on Transport Properties of?YBa2Cu3O7?y HTS

The nominally pure and boron-doped YBa₂Cu₃B _x O_7?y samples with B-doping level x varying between 0 and 0.15 were prepared by the solid state reaction. X-ray diffraction analysis shows that all the obtained compounds are single YBa₂Cu₃O_7?y phase. The small additives of boron in YBa₂Cu₃B _x O_7?y (x=0.025 and 0.05) do not essentially affect the critical temperature T _c and it remains near 90 K. The higher-level boron doping causes degradation of T _c and tail remains on the ??(T) curve for x=0.15 at 65 K. Lowest-level boron doping applied leads to a significant improvement in J _c compared to the undoped sample (from 100 A?cm^?2 for a control sample to 147 A?cm^?2 for a B-doped sample with x=0.025). Grain boundary critical current density and superconducting volume fraction decrease with increasing amount of added B₂O₃. The obtained results indicate possibility of boron dopant being entered into the lattice-sites.     

Simultaneous Measurement of Torsional Oscillator and?NMR in Solid 4He with 10?ppm of 3He

We have performed the simultaneous measurement of torsional oscillator and NMR in solid ⁴He with 10 ppm of ³He at 3.6 MPa. In this solid, NCRI response appears below about 400 mK. NMR measurement shows that there is the same kind of phase-separated ³He cluster which is found in our previous measurement in solid ⁴He with over a hundred ppm of ³He. When we warm the solid above the phase separation temperature, the cluster disappears gradually. Below and above the phase separation temperature, the distribution of ³He atoms changes significantly with long time constant, which is as long as a day. However, even in such a long time span, we do not observe any systematic changes in the torsional oscillator response. This result suggests that the phase separation and related changes of the distribution of ³He is not directly related to the impurity effect of the NCRI response.     

Improvement of the Superconducting Transport Properties of YBa2Cu3O7?δ by BaZrO3 Doping

We have doped the YBa₂Cu₃O_7– superconducting ceramics with BaZrO₃ up to 75wt.% and studied the changes of some physical properties. The most important finding is the enhancement of the critical current density, which has a maximum at around 5 wt.% doping level. Compared with the undoped samples, the critical current density is four times higher if the doping compound is introduced prior to the calcination treatment, or two times higher if BaZrO₃ is introduced prior to the sintering treatment. The dependence of the critical current density on the doping level is consistent with the dependence of the Seebeck coefficient. We also observed a very small decrease of the critical temperature. The real density of the samples decreases with increasing doping level as expected from the ratio between the theoretical densities of YBa₂Cu₃O_7– and BaZrO₃, the effect being important for doping levels higher than 25 wt.%.     

Mass Coupling and Q ?1 of Impurity-Limited Normal 3He in?a?Torsion Pendulum

We present results of the Q ^?1 and period shift, ??P, for ³He confined in a 98% nominal open aerogel on a torsion pendulum. The aerogel is compressed uniaxially by 10% along a direction aligned to the torsion pendulum axis and was grown within a 400???m tall pancake (after compression) similar to an Andronikashvili geometry. The result is a high Q pendulum able to resolve Q ^?1 and mass coupling of the impurity-limited ³He over the whole temperature range. After measuring the empty cell background, we filled the cell above the critical point and observe a temperature dependent period shift, ??P, between 100?mK and 3?mK that is 2.9% of the period shift (after filling) at 100?mK. The Q ^?1 due to the ³He decreases by an order of magnitude between 100?mK and 3?mK at a pressure of 0.14??0.03?bar. We compare the observable quantities to the corresponding calculated Q ^?1 and period shift for bulk ³He.     

Is 3D Printing of Pharmaceuticals a Disruptor or Enabler?

Additive manufacturing (AM) is a fast‐growing manufacturing approach that comes with the promise of delivering personalized medicine to treat individual patients. However, large‐scale commercial applications in the pharmaceutical industry have been limited. Here, some of the challenges are discussed along with some pharmaceutical products where AM has the potential to make a tangible impact and pave the way for more rapid adoption are highlighted.     

Enhancement of Vortex Pinning in YBa2Cu3O7?δ -BaHfO3 Superconductor-Insulator System

A systematic study on phase evolution, bulk density, resistivity, critical transition temperature (T _C), critical current density (J _C) and in-field transport critical current density (J _C?CB) of pure and nano particles of BaHfO₃ added YBa₂Cu₃O_7??? (YBCO) samples of different weight percentages has been carried out. The result shows a significant improvement in the electrical transport properties of the superconductor, namely the J _C, J _C?CB characteristics and flux pinning force (F _p) of the BaHfO₃ added samples. The transition temperature also was found to increase marginally. A maximum transport J _C of 742?A/cm² at 77?K (for x=2?wt%) was observed for BaHfO₃ added samples against 147?A/cm² for pure YBCO sample. The enhancement of the critical current density in the YBCO?CBaHfO₃ sample is attributed to the formation of an insulating and non-reacting YBa₂HfO_5.5 phase, acting as artificial pinning centers in the matrix. The introduction of nano particles of BaHfO₃ in bulk YBCO increases the pinning force density from 30×10³?N/m³ to 424×10³?N/m³ at 77 K. The improvement in sintering density due to an optimum value 2?wt% BaHfO₃ addition in bulk YBCO indicates its potential use in electrical devices and technology. The enhancement in the superconducting properties, particularly in the J _C?CB characteristics due to BaHfO₃ addition, seems to have great technological significance.     

Effect of Nickel Doping on the Magnetotransport Properties of?Sm0.55Sr0.45MnO3 Manganites

We studied the effects of nickel (Ni) doping on the magneto-transport properties of Sm_0.55Sr_0.45MnO₃ manganites near the metal-insulator transition. Various concentrations of Ni-doped Sm_0.55Sr_0.45MnO₃ samples up to 10% were prepared (Ni was partially substituted at the Mn-site). The temperature dependence of resistivity and magnetoresistance were measured as a function of Ni concentrations at various applied magnetic fields. We observed a nonlinear reduction of the metal-insulator transition temperature (MIT) with increasing concentration of Ni, 5% of Ni was sufficient to completely suppress the insulator-metal transition. Moreover, we observed dramatic increases of the resistance of the doped material with an increasing Ni-doping (5% of Ni increases R by more than 1000 times). The resistivity peaks at various magnetic fields collapses on themselves at the high temperature ends above the MIT. We also performed magnetization versus temperature measurements on both Ni-free the Ni-doped samples for FC and ZFC states. The FC and ZFC curves rapidly decrease to paramagnetic state at 175 K and 130 K for ZFC and FC states, respectively. For other Ni-doped samples, we observed a reduction in the paramagnetic transition temperature with increasing Ni concentration.     

Nuclear Spin Relaxation in Glass States of 3He-A in?Stretched Aerogel

We present results of pulse NMR investigations of superfluid A-like phase of ³He in stretched aerogel. In this case we have anisotropic orbital glass (OG) with two possible types of ordering in spin space??ordered spin nematic (OG-SN) or disordered spin glass (OG-SG) states. It was found that longitudinal relaxation of magnetization is non-exponential in both states and depends on temperature and on inhomogeneity of external steady magnetic field. At the same conditions the relaxation in OG-SG state is more rapid than in OG-SN state. For transverse orientation of the magnetic field relative to anisotropy axis the duration of free induction decay signal was longer than in normal phase. It may be explained by formation of coherently precessing spin state.     

Andreev Reflection of Quasiparticles by a Vortex Tangle in Superfluid 3He-B?

We have made the surprising discovery that the thermal damping of a vibrating wire resonator in superfluid ³ He-B at ultra low temperatures is considerably depressed when a second wire in the vicinity is driven supercritically. The damping of a vibrating wire resonator at low velocities in the B-phase arises from the scattering of quasiparticle excitations and has a temperature dependence proportional to the Boltzmann factor exp(–/kT) at low temperatures. At higher velocities (v>v_L/3), the wire breaks Cooper pairs and emits a quasiparticle beam. At first sight it seems paradoxical that heating the superfluid can reduce the quasiparticle flux on a neighbouring wire. We can only understand this on the basis that vorticity emitted by the supercritical wire shields, via Andreev reflection, part of the background quasiparticle flux from reaching the other wire. If this interpretation is correct, these techniques will provide a sensitive probe of vortex dynamics in the ultra low temperature regime.     

Levitation Force Density on Different Thicknesses of?YBa2Cu3O7?x Bulk Superconductor Fabricated by?FQMG?Process

A precursor YBCO in the stoichiometric ratio of 1:2:3 was prepared by the flame-quench-melt-growth (FQMG) method. Both the superconducting and nonsuperconducting regions were decided by measuring the magnetic levitation force per unit volume as a function of thickness of the superconducting sample. It was determined that superconducting forming ratio depends on where it forms in the sample, and thus a region near the top surface of the sample contains more superconducting forming ratio than the other regions. The levitation force density measured at different thicknesses of the sample ranging from 6.54 to 1.58 mm firstly increased and then separately reached a saturation point (maximum value) for both repulsive and attractive levitation force density. It was found that the maximum values of the repulsive and attractive levitation forces were respectively 125 mN/cm³ and ?23 mN/cm³. The considerably improved F _L ?z performance in FQMG sample can be translated to large-scale Y123 blocks intended for real superconducting levitation applications.     

Optimal timing of initiation of chronic hemodialysis?

Despite the availability of clinical guidelines for the timing of dialysis initiation in both the United States and Canada, patients continue to start dialysis at very low levels of predicted glomerular filtration rate (GFR). A cross-sectional study was performed to determine the demographic and clinical characteristics of patients who started hemodialysis, their level of GFR, and mortality at 1 and 2 years following the initiation of dialysis. Retrospective data were collected on all eligible patients who commenced chronic hemodialysis in 1 tertiary care center in Canada from March 2001 to February 2005. Only those patients who had been followed by a nephrologist in the chronic kidney disease clinic before dialysis initiation were included (n=271). Seventeen percent of patients started hemodialysis late (GFR<5 mL/min/1.73 m(2)). Compared with the group of patients who started dialysis earlier, the late start group were significantly younger (p=0.008), had more females (p=0.013), more employed (p=0.051), less cardiac (p<0.001), and peripheral vascular disease (p=0.031), and were taking medication for hypertension (p=0.041). Serum albumin was lower in the late start group (p=0.023). At year 1, there was no difference in mortality rate while at year 2, the earlier the dialysis, the greater the mortality rate (p=0.022). After adjustment for demographic variables and comorbidities, only antihypertensive use had an independent but weak association with the 2 year mortality. Adjustment for all these variables eliminated the significant association noted for the 2 year mortality in the early versus late dialysis start. The survival benefit for late versus early dialysis start appears to be multifactorial and relates to a preponderance of clinical and demographic factors favoring a lengthened survival occurring in the late dialysis group. Our survival benefit findings suggest the premorbid health condition is a more important determinant of 2 year survival than the timing of dialysis initiation.     

Textures of Superfluid 3He-B in Applied Flow and?Comparison with Hydrostatic Theory

Measurements of the order parameter texture of rotating superfluid ³He-B have been performed as a function of the applied azimuthal counterflow velocity down to temperatures of 0.2 T _c. The results are compared to the hydrostatic theory of ³He-B. Good agreement is found at all measured temperatures and rotation velocities when the flow anisotropy contribution to the textural free energy is adjusted. This gives a superfluid energy gap ??(T) which agrees with that measured by Todoshchenko et al., with ??(0)=1.97 k _B T _c at 29.0 bar. The B-phase susceptibility, longitudinal resonance frequency, and textural phase transition have been extracted from the measurements as a function of temperature and azimuthal counterflow velocity. Owing to decreasing absorption intensities the present measuring method, based on the line shape analysis of the NMR spectrum, loses its sensitivity with decreasing temperature. However, we find that in practice the measurement of vortex numbers and counterflow velocities is still feasible down to 0.2 T _c.     

NMR in Superfluid A-Like Phase of 3He Confined in?Globally Deformed Aerogel in?Tilted Magnetic Field

NMR spectra in superfluid A-like phases confined in axially deformed aerogel in the presence of a magnetic field inclined with respect to deformation axis is considered. The characteristic features of dipole frequency shift in axially compressed and axially stretched cases are compared. In particular, it is shown that in axially stretched aerogel environment the stability region of coherently spin-precessing mode is rather narrow due to the U(1) LIM effect. The spectrum of high-frequency spin fluctuations accompanying coherently precessing spin modes is constructed.     

Effect of SiO 32? /OH? on plasma electrolytic oxidation of Ti-5Mo-4V-3Al

Plasma electrolyte oxidation (PEO) was utilized to produce thick films on titanium and Ti-5Mo-4V-3Al alloys by immersing them in various solutions of Na₂SiO₃ and KOH with different concentrations to investigate the effect of SiO₃²⁻/OH⁻ relations on the morphology and formed phases by utilizing SEM and XRD. Corrosion resistance is evaluated by open circuit potential (OCP) variation of samples in NaCl 3.5% and potentiodynamic polarization. The results show that the unstable film is formed by using more aggressive PEO electrolyte. By increasing this ratio, pore size varied from fine to coarse and the rate of corrosion decreased and OCP became more positive. The best protective film was formed in SiO₃²⁻/OH⁻ ratio of 1.     

Crystallization Characteristics of YBa2Cu3O7?δ Film during TFA-MOD

The phase formation and film shrinkage during the crystallization process of YBa₂Cu₃O_7−δ (YBCO) film prepared by the trifluoroacetate organic deposition (TFA-MOD) were investigated through a series of quenching experiments. X-ray diffraction patterns show that the YBCO grains initially form following the formation of the Ba-O-F phase at the heating ramp between 720 °C and 770 °C in the case of a high heating rate of 20 °C/min. It is identified that the crystallization process is involved three stages, i.e., the first one characterized by the formation of the Ba-O-F phase, the second one by the YBCO grain nucleation together with the significant shrinkage of films, and the last one by continuous YBCO grain growth. Moreover, a heterogeneous Cl element is believed to arise from the flowing water vapor, and it may move into the intermediate pyrolyzed film. It is observed that the densification process existing in the secondary stage can be destroyed by the exterior Cl element, leading to a more porous structure in contrast to their surrounding.