480 research outputs found
Advanced titanium scaffolds obtained by directional freeze-drying: on the influence of processing conditions
Ministry of Science and Innovation of Spain under Grant No. MAT2010-20855Junta de Andalucía (Spain) / FEDER (EU), through the project Ref. P12-TEP-140
Hole spin driving by strain-induced spin-orbit interactions
Hole spins in semiconductor quantum dots can be efficiently manipulated with
radio-frequency electric fields owing to the strong spin-orbit interactions in
the valence bands. Here we show that the motion of the dot in inhomogeneous
strain fields gives rise to linear Rashba spin-orbit interactions (with
spatially dependent spin-orbit lengths) and g-factor modulations that allow for
fast Rabi oscillations. Such inhomogeneous strains may build up spontaneously
due to process and cool down stress. We discuss spin qubits in Ge/GeSi
heterostructures as an illustration. We highlight that Rabi frequencies can be
enhanced by one order of magnitude by shear strain gradients as small as
nm within the dots. This underlines that spin in
solids can be very sensitive to strains and opens the way for strain
engineering in hole spin devices for quantum information and spintronics.Comment: 19 pages, 3 figure
Hole spin manipulation in inhomogeneous and non-separable electric fields
The usual models for electrical spin manipulation in semiconductor quantum
dots assume that the confinement potential is separable in the three spatial
dimensions and that the AC drive field is homogeneous. However, the electric
field induced by the gates in quantum dot devices is not fully separable and
displays significant inhomogeneities. Here, we address the electrical
manipulation of hole spins in semiconductor heterostructures subject to
inhomogeneous vertical electric fields and/or in-plane AC electric fields. We
consider Ge quantum dots electrically confined in a Ge/GeSi quantum well as an
illustration. We show that the lack of separability between the vertical and
in-plane motions gives rise to an additional spin-orbit coupling mechanism
(beyond the usual linear and cubic in momentum Rashba terms) that modulates the
principal axes of the hole gyromagnetic g-matrix. This non-separability
mechanism can be of the same order of magnitude as Rashba-type interactions,
and enables spin manipulation when the magnetic field is applied in the plane
of the heterostructure even if the dot is symmetric (disk-shaped). More
generally, we show that Rabi oscillations in strongly patterned electric fields
harness a variety of g-factor modulations. We discuss the implications for the
design, modeling and understanding of hole spin qubit devices
Running Economy: Reproductibility at submaximal high speed
INTRODUCTION: The running economy (RE) has been traditionally determined by measuring the steady-state consumption of oxygen at a specific speed; however few studies has been designed to evaluate the reproductibility of the RE at a high rate of maximum oxygen consumption after repeated submaximal efforts within the same session. PURPOSE: The purpose of this study was valuate if the reproductibility of running economy at submaximal high speed could be affected by two previous submaximal efforts. METHODS: In this study participated 19 subjects (mean±SD; age, 21.8±2.5 years; body mass, 71.0±10.6 and height, 175.2±8.1). During three days of assessment separately for at least 24h of recovery, subjects performed the following tests. Day 1 a maximum incremental test, to determine the intensities. Day 2 a test of running economy at 80% of VO2max. Day 3 a test of running economy at 30, 70 and 80% of VO2max separated by 5 min of recovery. t-student test was conducted to measure test-retest differences in RE the p value were set al ≤0.05. RESULTS: No significant differences were found in the Running Economy at 80% of VO2max determined in both economy tests RE 220.1± 21.6vs 219.6±20.6 (ml·kg-1·km-1), ICC; 0.92, CV; 4.4 ± 2.6. CONCLUSION: The results of the present study showed exercises sessions at 30 and 70 of VO2max performed before the submaximal exercise test (80% of VO2max) did not affected the RE during an exercise test performed at 80% of VO2max
Second Order Sliding Mode Control of a STATCOM with Saturated Inputs
This paper presents a robust controller for a STATCOM device with saturated inputs. As the primary assumption, the proposed design considers the presence of unknown but bounded external perturbations and parametric variations. This proposal has a cascade structure, where a saturated super twisting control algorithm closes the currents control loop, and a high-gain proportional-integral (PI) algorithm ensures the voltage regulation. Thus, the exposed scheme provides an adequate performance of the STATCOM, considering the saturation of the inputs with the anti-windup feature. Posteriorly, a proper stability analysis presents the conditions for the appropriate operation of the closed-loop system in saturation and non-saturation regimes. Numerical simulations are also included to show the performance of the proposed controller
Magnetic solid-phase extraction based on poly 4-vinyl pyridine for HPLC-FLD analysis of naproxen in urine samples
Producción Científica: A magnetic solid phase extraction technique followed by liquid chromatography with a fluorescence detector for naproxen analysis in human urine samples was developed. The method includes the extraction of naproxen with a magnetic solid synthetized with magnetite and poly 4-vinylpriridine, followed by the magnetic separation of the solid phase and desorption of the analyte with methanol. Under optimal conditions, the linear range of the calibration curve was 0.05–0.60 μg L−1, with a limit of detection of 0.02 μg L−1. In all cases values of repeatability were lower than 5.0% with recoveries of 99.4 ± 1.3%. Precision and accuracy values are adequate for naproxen (Npx) analysis in urine samples
Signature of microRNA expression during osteogenic differentiation of bone marrow MSCs reveals a putative role of miR-335-5p in osteoarthritis
Background: The aim of this study was to evaluate, the existence of a
signature of differentially expressed microRNAs (miRNAs) during
osteogenic differentiation of bone marrow MSCs from OA and healthy
donors and to describe their possible implication in joint regeneration
through modulation of molecular mechanisms involved in homeostatic
control in OA pathophysiology.
Methods: Following phenotypic assessment of BM-MSCs obtained from OA
diagnosed patients (n = 10) and non-OA (n = 10), total small RNA was
isolated after osteogenic induction for 1, 10 and 21 days, miRNA
profiles were generated using a commercial expression array of 754
well-characterized miRNAs. MiRNAs, with consistent differential
expression were selected for further validation by quantitative
reverse-transcription polymerase chain reaction (qRT-PCR) analysis.
Results: A total of 246 miRNAs were differentially expressed (fold
change >=+/- 2, P <= 0.05) between OA and non-OA BM-MSC samples; these
miRNAs showed variable interactions depending on the cell and
differentiation status. Two miRNAs, hsa-miR-210 and hsa-miR-335-5p out
of 21 used for validation showed a significant downregulated expression
during induced osteogenesis. In particular hsa-miR-335-5p, a critical
regulator in bone homeostasis, was further studied. hsa-miR-335-5p
downregulation in OA-MSCs, as well as their host coding gene, MEST, were
also assessed.
Conclusions: To our knowledge, this study represents the most
comprehensive assessment to date of miRNA expression profiling in
BM-MSCs from OA patients and their role during osteogenic
differentiation. We describe the existence of a correlation between
miR-335-5p expression and OA indicating the putative role of this miRNA
in OA features. These findings, may contribute to our understanding of
the molecular mechanisms involved in MSCs mediated homeostatic control
in OA pathophysiology that could be applicable in future therapeutic
approaches.This work was supported in part by institutional grants from the
Instituto de Salud Carlos III CP10/00346 and PI10/00178 and the Spanish
society of orthopaedics surgery and traumatology (SECOT).; J.R. Lamas is
supported by the Miguel Servet program from ISCIII-Fondo Investigacion
Sanitaria-Spain (CP10/00346).S
Biology (growth and reproduction) of the Mediterranean deep-water rose shrimp (Parapenaeus longirostris (Lucas, 1846), Crustacea, Decapoda) from the Alicante Gulf (s.e. Spain).
The deep-water rose shrimp (Parapenaeus longirostris) is a demersal species and an important resource for the trawl fishery in the Alicante Gulf (S.E. Spain). This paper describes, for first time in this area, certain biometric relationships, as well as growth parameters and reproductive patterns of the species. The results showed a sexual size dimorphism, with a negative allometry of relative growth and high rates of absolute growth, both particularly in males. However, females dominated in the catch proportion. The spawning period occurred throughout the year, but especially in June-July and in October-November and the maturation stage for females takes place within the second year of life
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