Numerical Simulation of Magnetic Interactions in Polycrystalline YFeO3

The magnetic behavior of polycrystalline yttrium orthoferrite was studied from the experimental and theoretical points of view. Magnetization measurements up to 170 kOe were carried out on a single-phase YFeO3 sample synthesized from heterobimetallic alkoxides. The complex interplay between weak-ferromagnetic and antiferromagnetic interactions, observed in the experimental M(H) curves, was successfully simulated by locally minimizing the magnetic energy of two interacting Fe sublattices. The resulting values of exchange field (H_E = 5590 kOe), anisotropy field (H_A = 0.5 kOe) and Dzyaloshinsky-Moriya antisymmetric field (H_D = 149 kOe) are in good agreement with previous reports on this system.Comment: 26 pages, 9 figure

Device for lengthening of a musculotendinous unit by direct continuous traction in the sheep

Background Retraction, atrophy and fatty infiltration are signs subsequent to chronic rotator cuff tendon tears. They are associated with an increased pennation angle and a shortening of the muscle fibers in series. These deleterious changes of the muscular architecture are not reversible with current repair techniques and are the main factors for failed rotator cuff tendon repair. Whereas fast stretching of the retracted musculotendinous unit results in proliferation of non-contractile fibrous tissue, slow stretching may lead to muscle regeneration in terms of sarcomerogenesis. To slowly stretch the retracted musculotendinous unit in a sheep model, two here described tensioning devices have been developed and mounted on the scapular spine of the sheep using an expandable threaded rod, which has been interposed between the retracted tendon end and the original insertion site at the humeral head. Traction is transmitted in line with the musculotendinous unit by sutures knotted on the expandable threaded rod. The threaded rod of the tensioner is driven within the body through a rotating axis, which enters the body on the opposite side. The tendon end, which was previously released (16 weeks prior) from its insertion site with a bone chip, was elongated with a velocity of 1 mm/day. Results After several steps of technical improvements, the tensioner proved to be capable of actively stretching the retracted and degenerated muscle back to the original length and to withstand the external forces acting on it. Conclusion This technical report describes the experimental technique for continuous elongation of the musculotendinous unit and reversion of the length of chronically shortened muscle

Costamere protein expression and tissue composition of rotator cuff muscle after tendon release in sheep

Previous studies suggested that degradation of contractile tissue requires cleavage of the costamere, a structural protein complex that holds sarcomeres in place. This study examined if costamere turnover is affected by a rotator cuff tear in a previously established ovine model. We found the activity of focal adhesion kinase (FAK), a main regulator of costamere turnover, was unchanged at 2 weeks but decreased by 27% 16 weeks after surgical release of the infraspinatus tendon. This was accompanied by cleavage of the costamere protein talin into a 190 kDa fragment while full length talin remained unchanged. At 2 weeks after tendon release, muscle volume decreased by 17 cm from an initial 185 cm(3) , the fatty tissue volume was halved, and the contractile tissue volume remained unchanged. After 16 weeks, the muscle volume decreased by 36 cm(3) , contractile tissue was quantitatively lost, and the fat content increased by 184%. Nandrolone administration mitigated the loss of contractile tissue by 26% and prevented fat accumulation, alterations in FAK activity, and talin cleavage. Taken together, these findings imply that muscle remodeling after tendon release occurs in two stages. The early decrease of muscle volume is associated with reduction of fat; while, the second stage is characterized by substantial loss of contractile tissue accompanied by massive fat accumulation. Regulation of costamere turnover is associated with the loss of contractile tissue and seems to be impacted by nandrolone treatment. Clinically, the costamere may represent a potential intervention target to mitigate muscle loss after a rotator cuff tear. © 2017 The Authors. Journal of Orthopaedic Research published by Wiley Periodicals, Inc. on behalf of the Orthopaedic Research Society. J Orthop Res

Size dependence of the magnetic relaxation and specific power absorption in iron oxide nanoparticles

We report on the magnetic and power absorption properties of a series of iron oxide nanoparticles with average sizes ranging from 3 to 23 nm, prepared by thermal decomposition of Iron(III) acetylacetonate in organic media. From the careful characterization of the magnetic and physicochemical properties of these samples, we were able to reproduce the specific power absorption (SPA) values experimentally found, as well as their dependence with particle size, using a simple model of Brownian and Neel Relaxation at ´ room temperature. SPA experiments in ac magnetic fields (0 = 13 kA/m and f = 250 kHz) indicated that the magnetic and rheological properties played the fundamental rule to determine the heating efficiency at different conditions. A maximum SPA value of 344 W/g was obtained for a sample containing nanoparticles with = 12 nm and dispersion σ = 0.25. The observed SPA dependence with particle diameter and their magnetic parameters indicated that, for the size range and experimental conditions of f and H studied in this work, both Neel and Brown relaxation mechanisms are important to the heat generation observed.Fil: Lima, Enio Junior. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Torres, T. E.. Universidad de Zaragoza; EspañaFil: Rossi, L. M.. Universidade de Sao Paulo; BrasilFil: Rechenberg, R.. Universidade de Sao Paulo; BrasilFil: Berquo, T. S.. University Of Minnesota; Estados UnidosFil: Ibarra, A.. Universidad de Zaragoza; EspañaFil: Marquina, C.. Universidad de Zaragoza; EspañaFil: Ibarra, R. M.. Universidad de Zaragoza; EspañaFil: Goya, G. F.. Universidad de Zaragoza; Españ

The effect of cartilage and bone density of mushroom-shaped, photooxidized, osteochondral transplants: an experimental study on graft performance in sheep using transplants originating from different species

BACKGROUND: Differences in overall performance of osteochondral photooxidized grafts were studied in accordance of their species origin and a new, more rigorous cleansing procedure using alcohol during preparation. METHODS: Photooxidized mushroom-shaped grafts of bovine, ovine, human and equine origin were implanted in the femoral condyles of 32 sheep (condyles: n = 64). No viable chondrocytes were present at the time of implantation. Grafts were evaluated at 6 months using plastic embedded sections of non-decalcified bone and cartilage specimens. Graft incorporation, the formation of cyst-like lesions at the base of the cartilage junction as well as cartilage morphology was studied qualitatively, semi-quantitatively using a score system and quantitatively by performing histomorphometrical measurements of percentage of bone and fibrous tissue of the original defects. For statistical analysis a factorial analysis of variance (ANOVA- test) was applied. RESULTS: Differences of graft performance were found according to species origin and cleansing process during graft preparation. According to the score system cartilage surface integrity was best for equine grafts, as well as dislocation or mechanical stability. The equine grafts showed the highest percentage for bone and lowest for fibrous tissue, resp. cystic lesions. The new, more rigorous cleansing process decreased cartilage persistence and overall graft performance. CONCLUSION: Performance of grafts from equine origin was better compared to bovine, ovine and human grafts. The exact reason for this difference was not proven in the current study, but could be related to differences in density of cartilage and subchondral bone between species

Analysis of the Hydrogen-rich Magnetic White Dwarfs in the SDSS

We have calculated optical spectra of hydrogen-rich (DA) white dwarfs with magnetic field strengths between 1 MG and 1000 MG for temperatures between 7000 K and 50000 K. Through a least-squares minimization scheme with an evolutionary algorithm, we have analyzed the spectra of 114 magnetic DAs from the SDSS (95 previously published plus 14 newly discovered within SDSS, and five discovered by SEGUE). Since we were limited to a single spectrum for each object we used only centered magnetic dipoles or dipoles which were shifted along the magnetic dipole axis. We also statistically investigated the distribution of magnetic-field strengths and geometries of our sample.Comment: to appear in the proceedings of the 16th European Workshop on White Dwarfs, Barcelona, 200

Hybridizing the 1/5-th Success Rule with Q-Learning for Controlling the Mutation Rate of an Evolutionary Algorithm

It is well known that evolutionary algorithms (EAs) achieve peak performance only when their parameters are suitably tuned to the given problem. Even more, it is known that the best parameter values can change during the optimization process. Parameter control mechanisms are techniques developed to identify and to track these values. Recently, a series of rigorous theoretical works confirmed the superiority of several parameter control techniques over EAs with best possible static parameters. Among these results are examples for controlling the mutation rate of the $(1+\lambda)$~EA when optimizing the OneMax problem. However, it was shown in [Rodionova et al., GECCO'19] that the quality of these techniques strongly depends on the offspring population size $\lambda$. We introduce in this work a new hybrid parameter control technique, which combines the well-known one-fifth success rule with Q-learning. We demonstrate that our HQL mechanism achieves equal or superior performance to all techniques tested in [Rodionova et al., GECCO'19] and this -- in contrast to previous parameter control methods -- simultaneously for all offspring population sizes $\lambda$. We also show that the promising performance of HQL is not restricted to OneMax, but extends to several other benchmark problems.Comment: To appear in the Proceedings of Parallel Problem Solving from Nature (PPSN'2020