Nonlinear AC resistivity in s-wave and d-wave disordered granular superconductors

We model s-wave and d-wave disordered granular superconductors with a three-dimensional lattice of randomly distributed Josephson junctions with finite self-inductance. The nonlinear ac resistivity of these systems was calculated using Langevin dynamical equations. The current amplitude dependence of the nonlinear resistivity at the peak position is found to be a power law characterized by exponent $\alpha$. The later is not universal but depends on the self-inductance and current regimes. In the weak current regime $\alpha$ is independent of the self-inductance and equal to 0.5 or both of s- and d-wave materials. In the strong current regime this exponent depends on the screening. We find $\alpha \approx 1$ for some interval of inductance which agrees with the experimental finding for d-wave ceramic superconductors.Comment: 4 pages, 5 figures, to appear in Phys. Rev. Let

Optimising prednisolone or prednisone replacement in adrenal insufficiency

CONTEXT: Patients with adrenal insufficiency (AI) have higher mortality than the general population, possibly because of excess glucocorticoid exposure at inappropriate times. The cortisol circadian rhythm is difficult to mimic with twice or thrice-daily hydrocortisone. Prednisolone is a once-daily alternative which may improve patient compliance and convenience. OBJECTIVES: Prednisolone day curves can be used to accurately down-titrate patients to the minimum effective dose. We aimed to review prednisolone day curves and determine therapeutic ranges at different timepoints after administration. METHODS: Between August 2013 and May 2021, 108 prednisolone day curves from 76 individuals receiving prednisolone replacement were analysed. Prednisolone concentrations were determined by ultra-high performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Spearman's correlation coefficient was used to determine the relationship between 2-, 4- and 6-hour prednisolone levels compared to the validated standard 8-hour prednisolone level (15-25 μg/L). RESULTS: The median dose was 4mg prednisolone once daily. There was strong correlation between the 4-hour and 8-hour (R=0.8829, p ≤0.0001), and 6-hour and 8-hour prednisolone levels (R=0.9530, p ≤ 0.0001). Target ranges for prednisolone were 37-62 μg/L at 4-hours, 24-39 μg/L at 6-hours and 15-25 μg/L at 8-hours. Prednisolone doses were successfully reduced in 21 individuals and of these, three were reduced to 2mg once daily. All patients were well upon follow-up. CONCLUSION: This is the largest evaluation of oral prednisolone pharmacokinetics in humans. Low dose prednisolone of 2-4mg is safe and effective in most patients with AI. Doses can be titrated with either 4-hour, 6-hour, or 8-hour single timepoint drug levels

Superconductivity and spin-glass like behavior in system with Pd sheet sandwiched between graphene sheets

Pd-metal graphite (Pd-MG) has a layered structure, where each Pd sheet is sandwiched between adjacent graphene sheets. DC magnetization and AC magnetic susceptibility of Pd-MG have been measured using a SQUID magnetometer. Pd-MG undergoes a superconducting transition at $T_{c}$ ($= 3.63 \pm 0.04$ K). The superconductivity occurs in Pd sheets. The relaxation of $M_{ZFC}$ (aging), which is common to spin glass systems, is also observed below $T_{c}$. The relaxation rate $S(t)$ shows a peak at a characteristic time $t_{cr}$, which is longer than a wait time $t_{w}$. The irreversibility between $\chi_{ZFC}$ and $\chi_{FC}$ occurs well above $T_{c}$. The susceptibility $\chi_{FC}$ obeys a Curie-Weiss behavior with a negative Curie-Weiss temperature ($-13.1 \leq \Theta \leq -5.4$ K). The growth of antiferromagnetic order is limited by the disordered nature of nanographites, forming spin glass-like behavior at low temperatures in graphene sheets.Comment: 21 pages, 15 figures; submitted to J. Phys.: Condensed Matte

Intracellular delivery of full length recombinant human mitochondrial L-Sco2 protein into the mitochondria of permanent cell lines and SCO2 deficient patient's primary cells

AbstractMutations in human SCO2 gene, encoding the mitochondrial inner membrane Sco2 protein, have been found to be responsible for fatal infantile cardioencephalomyopathy and cytochrome c oxidase (COX) deficiency. One potentially fruitful therapeutic approach for this mitochondrial disorder should be considered the production of human recombinant full length L-Sco2 protein and its deliberate transduction into the mitochondria. Recombinant L-Sco2 protein, fused with TAT, a Protein Transduction Domain (PTD), was produced in bacteria and purified from inclusion bodies (IBs). Following solubilisation with l-arginine, this fusion L-Sco2 protein was transduced in cultured mammalian cells of different origin (U-87 MG, T24, K-562, and patient's primary fibroblasts) and assessed for stability, transduction into mitochondria, processing and impact on recovery of COX activity. Our results indicate that: a) l-Arg solution was effective in solubilising recombinant fusion L-Sco2 protein, derived from IBs; b) fusion L-Sco2 protein was delivered successfully via a time- and concentration-dependent process into the mitochondria of human U-87 MG and T24 cells; c) fusion L-Sco2 protein was also transduced in human K-562 cells, transiently depleted of SCO2 transcripts and thus COX deficient; transduction of this fusion protein led to partial recovery of COX activity in such cells; d) [35S]Methionine-labelled fusion L-Sco2 protein, produced in a cell free transcription/translation system and incubated with intact isolated mitochondria derived from K-562 cells, was efficiently processed to yield the corresponding mature Sco2 protein, thus justifying the potential of the transduced fusion L-Sco2 protein to successfully activate COX holoenzyme; and finally, e) recombinant fusion L-Sco2 protein was successfully transduced into the mitochondria of primary fibroblasts derived from SCO2/COX deficient patient and facilitated recovery of COX activity. These findings provide the rationale of delivering recombinant proteins via PTD technology as a model for therapeutic approach of mitochondrial disorders

Nanosecond and femtosecond ablation of La0.6Ca0.4CoO3: a comparison between plume dynamics and composition of the films

Thin films of La0.6Ca0.4CoO3 were grown by pulsed laser ablation with nanosecond and femtosecond pulses. The films deposited with femtosecond pulses (248nm, 500fs pulse duration) exhibit a higher surface roughness and deficiency in the cobalt content compared to the films deposited with nanosecond pulses (248nm, 20ns pulse duration). The origin of these pronounced differences between the films grown by ns and fs ablation has been studied in detail by time-resolved optical emission spectroscopy and imaging. The plumes generated by nanosecond and femtosecond ablation were analyzed in vacuum and in a background pressure of 60 Pa of oxygen. The ns-induced plume in vacuum exhibits a spherical shape, while for femtosecond ablation the plume is more elongated along the expansion direction, but with similar velocities for ns and fs laser ablation. In the case of ablation in the background gas similar velocities of the plume species are observed for fs and ns laser ablation. The different film compositions are therefore not related to different kinetic energies and different distributions of various species in the plasma plume which has been identified as the origin of the deficiency of species for other material

Perceived exertion influences pacing among ultramarathon runners but post-race mood change is associated with performance expectancy

Objectives. This study investigated whether post-race mood changes among ultramarathon runners are associated with perceived exertion or the discrepancy between their actual and predicted performance times.Methods. Eight runners completed the Puffer ultramarathon, which is a challenging 73 km mountainous race across Table Mountain National Park in South Africa. Each runner completed a series of profile of mood state questionnaires (POMS) 2 days before the race (baseline), on the morning of the race (pre-race) and immediately after the race (post-race). Ratings of perceived exertion (RPE) were measured at 13 points during the race using the Borg 6-20 scale. The accuracy of performance expectationswas measured as the difference between runners’ actual and predicted race times.Results. Average completion time was 11:31:36±00:26:32 (h :mm:ss), average running speed was 6.4±2.2 km.hr-1 and averageRPE was 14.1±2.0. Increased POMS confusion was found before the race (33.30.7 v. 37.1±5.2, p=0.014; baseline v. pre-race). Post-race increases in POMS total mood disturbance (TMD) were found (168.3±20 v. 137.5±6.3, p=0.001; post race v. baseline) characterised by decreased vigour (43.3±4.0 v. 33.5±7.0, p=0.008; baseline v. post race), increased confusion (33.3±0.7 v. 38.5±4.8, p=0.006; baseline v. post race) and increased fatigue (37.8±4.8 v. 53.8±7.3, p=0.0003; baseline v. post race). A linear increase in RPE was found during the race (r=0.737, p=0.002).The magnitude of their post-race mood change (r=-0.704, p=0.026) was not found to be associated with runners’ average RPE but was found to be negatively correlated with accuracy of the performance predictions. A time series analysis indicated that POMS TMD would have taken 142±89 min to recover. Conclusions. The results show that RPE influences the wayultramarathon runners pace themselves more than performance expectancy but performance expectations have a greater influence on post-race mood. The magnitude of post-race mood change is associated with the extent of discrepancy between runners’ predicted and actual performance. This has implications for designing appropriate goals and pacing strategies for ultraendurance athletes.

Strong rejuvenation in a chiral-glass superconductor

The glassy paramagnetic Meissner phase of a Bi$_2$Sr$_2$CaCu$_2$O$_x$ superconductor ($x$ = 8.18) is investigated by squid magnetometry, using ``dc-memory'' experiments employed earlier to study spin glasses. The temperature dependence of the zero-field-cooled and thermo-remanent magnetization is recorded on re-heating after specific cooling protocols, in which single or multiple halts are performed at constant temperatures. The 'spin' states equilibrated during the halts are retrieved on re-heating. The observed memory and rejuvenation effects are similar to those observed in Heisenberg-like spin glasses.Comment: REVTeX 4 style; 5 pages, 5 figure