Cubic anisotropy in high homogeneity thin (Ga,Mn)As layers

Historically, comprehensive studies of dilute ferromagnetic semiconductors, e.g., $p$-type (Cd,Mn)Te and (Ga,Mn)As, paved the way for a quantitative theoretical description of effects associated with spin-orbit interactions in solids, such as crystalline magnetic anisotropy. In particular, the theory was successful in explaining {\em uniaxial} magnetic anisotropies associated with biaxial strain and non-random formation of magnetic dimers in epitaxial (Ga,Mn)As layers. However, the situation appears much less settled in the case of the {\em cubic} term: the theory predicts switchings of the easy axis between in-plane $\langle 100\rangle$ and $\langle 110\rangle$ directions as a function of the hole concentration, whereas only the $\langle 100\rangle$ orientation has been found experimentally. Here, we report on the observation of such switchings by magnetization and ferromagnetic resonance studies on a series of high-crystalline quality (Ga,Mn)As films. We describe our findings by the mean-field $p$-$d$ Zener model augmented with three new ingredients. The first one is a scattering broadening of the hole density of states, which reduces significantly the amplitude of the alternating carrier-induced contribution. This opens the way for the two other ingredients, namely the so-far disregarded single-ion magnetic anisotropy and disorder-driven non-uniformities of the carrier density, both favoring the $\langle 100\rangle$ direction of the apparent easy axis. However, according to our results, when the disorder gets reduced a switching to the $\langle 110\rangle$ orientation is possible in a certain temperature and hole concentration range.Comment: 12 pages, 9 figure

A neuromechanics-based powered ankle exoskeleton to assist walking post-stroke: a feasibility study

Background: In persons post-stroke, diminished ankle joint function can contribute to inadequate gait propulsion. To target paretic ankle impairments, we developed a neuromechanics-based powered ankle exoskeleton. Specifically, this exoskeleton supplies plantarflexion assistance that is proportional to the user’s paretic soleus electromyography (EMG) amplitude only during a phase of gait when the stance limb is subjected to an anteriorly directed ground reaction force (GRF). The purpose of this feasibility study was to examine the short-term effects of the powered ankle exoskeleton on the mechanics and energetics of gait. Methods: Five subjects with stroke walked with a powered ankle exoskeleton on the paretic limb for three 5 minute sessions. We analyzed the peak paretic ankle plantarflexion moment, paretic ankle positive work, symmetry of GRF propulsion impulse, and net metabolic power. Results: The exoskeleton increased the paretic plantarflexion moment by 16% during the powered walking trials relative to unassisted walking condition (p \u3c .05). Despite this enhanced paretic ankle moment, there was no significant increase in paretic ankle positive work, or changes in any other mechanical variables with the powered assistance. The exoskeleton assistance appeared to reduce the net metabolic power gradually with each 5 minute repetition, though no statistical significance was found. In three of the subjects, the paretic soleus activation during the propulsion phase of stance was reduced during the powered assistance compared to unassisted walking (35% reduction in the integrated EMG amplitude during the third powered session). Conclusions: This feasibility study demonstrated that the exoskeleton can enhance paretic ankle moment. Future studies with greater sample size and prolonged sessions are warranted to evaluate the effects of the powered ankle exoskeleton on overall gait outcomes in persons post-stroke

Six degree-of-freedom analysis of hip, knee, ankle and foot provides updated understanding of biomechanical work during human walking

Measuring biomechanical work performed by humans and other animals is critical for understanding muscle–tendon function, jointspecific contributions and energy-saving mechanisms during locomotion. Inverse dynamics is often employed to estimate jointlevel contributions, and deformable body estimates can be used to study work performed by the foot. We recently discovered that these commonly used experimental estimates fail to explain whole-body energy changes observed during human walking. By re-analyzing previously published data, we found that about 25% (8 J) of total positive energy changes of/about the body’s center-of-mass and \u3e30% of the energy changes during the Push-off phase of walking were not explained by conventional joint- and segment-level work estimates, exposing a gap in our fundamental understanding of work production during gait. Here, we present a novel Energy-Accounting analysis that integrates various empirical measures of work and energy to elucidate the source of unexplained biomechanical work. We discovered that by extending conventional 3 degree-of-freedom (DOF) inverse dynamics (estimating rotational work about joints) to 6DOF (rotational and translational) analysis of the hip, knee, ankle and foot, we could fully explain the missing positive work. This revealed that Push-off work performed about the hip may be \u3e50% greater than conventionally estimated (9.3 versus 6.0 J, P=0.0002, at 1.4 m s−1 ). Our findings demonstrate that 6DOF analysis (of hip– knee–ankle–foot) better captures energy changes of the body than more conventional 3DOF estimates. These findings refine our fundamental understanding of how work is distributed within the body, which has implications for assistive technology, biomechanical simulations and potentially clinical treatment

Price modeling of IaaS providers - An approach focused on enterprise application integration

One of the main advances in information technology today is cloud computing. It is a great alternative for users to reduce costs related to the need to acquire and maintain computational infrastructure to develop, implement and execute software applications. Cloud computing services are offered by providers and can be classified into three main modalities: Platform-as-a-Service (PaaS), Software-as-a-Service (SaaS) and Infrastructureas-a-Service (IaaS). In IaaS, the user has a virtual machine at their disposal with the desired computational resources at a given cost. Generally, the providers offer infrastructure services divided into instances, with preestablished configurations. The main challenge faced by companies is to choose the instance that best fits their needs among the many options offered by providers. Frequently, these companies need a large computational infrastructure to manage and improve their business processes and, due to the high cost of maintaining local infrastructure, they have begun to migrate applications to the cloud in order to reduce these costs. In this paper, we introduce a proposal for price modeling of instances of virtual machines using linear regression. This approach analyzes a set of simplified hypotheses considering the following providers: Amazon EC2, Google Compute Engine and Microsoft Windows Azure.info:eu-repo/semantics/acceptedVersio

Cloud Configuration Modelling: a Literature Review from an Application Integration Deployment Perspective

Enterprise Application Integration has played an important role in providing methodologies, techniques and tools to develop integration solutions, aiming at reusing current applications and supporting the new demands that arise from the evolution of business processes in companies. Cloud-computing is part of a new reality in which companies have at their disposal a high capacity IT infrastructure at a low-cost, in which integration solutions can be deployed and run. The charging model adopted by cloud-computing providers is based on the amount of computing resources consumed by clients. Such demand of resources can be computed either from the implemented integration solution, or from the conceptual model that describes it. It is desirable that cloud-computing providers supply detailed conceptual models describing the variability of services and restrictions between them. However, this is not the case and providers do not supply the conceptual models of their services. The conceptual model of services is the basis to develop a process and provide supporting tools for the decision-making on the deployment of integration solutions to the cloud. In this paper, we review the literature on cloud configuration modelling, and compare current proposals based on a comparison framework that we have developed

Profile of Phenolic Acids and Antioxidant Capacity in Organs of Common Buckwheat Sprout

The aim of the study was to analyse the content of phenolic acids, total phenolic compounds, proanthocyanidins, and antioxidant capacity in cotyledons and hypocotyl of five cultivars of common buckwheat (Fagopyrum esculentum Moench) sprout. This study presents the first broad profile of phenolic acids occurring in buckwheat microgreen seedlings. In the hypocotyl and cotyledons trans-cinnamic acid and its derivatives: o-, m-, and p-coumaric acids (2-, 3-, and 4-hydroxycinnamic), synapic acid (4-hydroxy-3,5-dimethoxycinnamic), caffeic acid (3,4-dihydroxycinnamic), and two isomers of ferulic acid (4-hydroxy-3-methoxycinnamic and 3-hydroxy-4-methoxycinnamic) have been identified. Among the benzoic acid derivatives hydroxybenzoic, protocatechuic (3,4-dihydroxybenzoic), gallic (3,4,5-dihydroxybenzoic) and syringic (4-hydroxy-3,5-dimethoxybenzoic) were found in the organs. In addition to those mentioned, the organs of buckwheat sprouts contain chlorogenic acid as well. The contents of all analysed phenolics were substantially higher in the cotyledons than in the hypocotyl of buckwheat sprouts, except for chlorogenic and caffeic acids. Trans-cinnamic acid was the major phenolic acid in both organs. In the cotyledons, a significant, positive linear correlation between the TEAC, ORAC, PLC-ACW values and content of total phenolic compounds, and also between DPPH and total phenolic acids were found. In the hypocotyl correlations between the DPPH, TEAC, and ORAC and proanthocyanidins content, between TEAC and total phenolic compounds, and between total phenolic acids and PCL-ACW were found