RHEED digital image analysis system for in-situ growth rate and alloy composition measurements of GaAs-based nanostructures

Monitoring the intensity of the reflected spot in a RHEED image is the most important method used to control the growth of semiconductors in MBE. The accurate control of both layer thickness and alloy composition is particularly important for the growth of high quality heterostructures. Indeed, under such conditions, extremely uniform and high quality epitaxial devices become possible. RHEED intensity oscillation can be used as accurate, quick and direct measure of the growth rates and alloy compositions as well. Although analog signal could be obtained by using an optical fiber associated to a photo-detector PM tube and a plotter, this method is troublesome and limited. In some application, the availability of the intensity signal as a digital voltage is useful to realize further advanced analysis, and achieve feedback between growth dynamic and the external parameters, such as the cells temperatures and the synchronization of the shutters. In this paper we describe the advantages gained with the upgrade of our analog system into a digital package using CCD camera, frame grabber and a home made software. Its main purpose is to track RHEED intensity changes and measures the rate of oscillation. A state-of-the-art RHEED digital image analysis system gives us the necessary tools to gain insight into the thin film growth process and optimize material quality

Modeling and simulation of tendon transfer for pinch task

This work displayed the maximum magnitude of the fingertip force required to secure objects following paralysis, rupture of extrinsic index extensors and following tendons transfers to assist clinicians in setting realistic expectations for rehabilitating strength of pinch. The optimal combination of tendon tensions that maximize fingertip force was predicted in case of the healthy, the pathological and the reconstructed index finger via a tendon transfer. We used a three-dimensional static biomechanical model based on finger anatomy and numerical optimization technique. The outcomes of the flexor carpi ulnaris (FCU) transfer to extensor communis (EDC), used to restore extension in the index finger, were simulated

Inhibitory effect of Teucrium ramosissimum extracts on aflatoxin B1, benzo[a]pyrene, 4-nitro-o-phenylenediamine and sodium azide induced mutagenicity: Correlation with antioxidant activity

AbstractThe mutagenic potential of total oligomers flavonoids (TOF), ethyl acetate (EA) and petroleum ether (PE) extracts from aerial parts of Teucrium ramosissimum was assessed using Ames Salmonella tester strains TA98, TA100 and TA1535 with and without metabolic activation (S9). None of the different extracts produced a mutagenic effect. Likewise, the antimutagenicity of the same extracts was tested using the “Ames test”. Our results showed that T. ramosissimum extracts possess antimutagenic activity against all the tested genotoxicants (aflatoxin B1, benzo[a]pyrene, 4-nitro-o-phenylenediamine and sodium azide) in the Salmonella assay systems used in this study. In addition, all extracts showed important free radical scavenging activity toward the radicals DPPH and ABTS except the PE extract

Comparative Analysis of CBRM Cases in Kenya, Ethiopia and Tunisia

In various countries, development and conservation organizations and national policymakers have been experimenting with ways of applying the community-based natural resource management approach to the unique social and biophysical characteristics of pastoralist rangeland settings, with mixed results. We carried out comparative case study research on community-based rangeland management (CBRM) in a variety of settings in Ethiopia, Kenya and Tunisia with the objective of identifying what kinds of strategies and methods work in which social and ecological contexts. We used an “options by context” approach guided by a research protocol that includes key variables and descriptors for characterizing the implementing organization’s approach to CBRM and important contextual factors that may vary from place to place and affect the implementation and success of the approach. The commonalities among our cases include: i) community governance and management structures for rangeland management; ii) the geographic rangeland unit which those structures are managing, and iii) a development agent that is supporting the community. We found that differences among the cases in the challenges faced and their degree of success depended at least as much on certain aspects of social and biophysical context as it did on the exact nature of the approach being implemented by the development agent. For example, the extent to which there are effective natural or social borders that provide the rangeland community with some degree of separation from neighbours is crucial; without such landscape features, the design principle of clearly defined rights to a clearly defined piece of land belonging to a clearly defined community is difficult to implement in any straightforward way. In some pastoral rangeland contexts, conventional community-based approaches need substantial modification to be effective in contexts with the highest levels of spatio-temporal variability, mobility and openness of the landscape

Barium effect on germination, plant growth, and antioxidant enzymes in Cucumis sativus L. plants

Barium (Ba) is a nonessential element that can cause several deleterious effects in most organisms. Elevated Ba concentrations can be toxic for plants and may affect growth and disturbances in homeostasis. This study aimed to evaluate the Ba stress, the plant-tolerance limits, and the detoxification strategy adopted by Cucumis sativus L. The effect of Ba on seed's germination and vegetative development of this species was evaluated. For germination test, different Ba concentrations were used (0, 200, 500, 1,000, and 2,000 μM). Results showed that germination was stimulated with 500 and 2,000 µM of Ba. The toxicity effect on plant development was studied by treating the plants with increasing doses of Ba (100, 200, 300, and 500 μM) during 45 days. Shoot and root dry biomass production decreased significantly with elevated Ba concentrations, although water content enhanced in the roots. The concentration of Ba, 500 µM, induced high Ba accumulation in shoots and roots (9 times higher than in the control plants). Moreover, results showed that catalase, guaiacol peroxidase, and ascorbate peroxidase activities were stimulated in the different tissues of cucumber plants which highlight the occurring of an oxidative damage through Ba treatments and the involvement of the plant enzymatic antioxidant defense system

A multipurpose experimental facility for advanced X-ray Spectrometry applications

Ponencia presentada en la European Conference on X-Ray Spectrometry (EXRS). 2014Motivation, Ultra High Vacuum Chamber (UHVC) project: To support/enhance the training of scientists/engineers from developing countries in the operation of synchrotron radiation instrumentation; To provide beam time access for R&D projects and hands-on training in SR-XRS based techniques; To promote networking and knowledge sharing; To increase the quality and the competitiveness of the developing countries to apply beam time proposals at SR facilities; To contribute in the further development of XRS techniques in applications with socioeconomicalrelevance (characterization of energy storage/conversion materials, environmental, biological and biomedical applications)Fil: Leani, Juan José. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina.Fil: Leani, Juan José. Nuclear Science and Instrumentation Laboratory, IAEA Laboratories; Austria.Física Atómica, Molecular y Química (física de átomos y moléculas incluyendo colisión, interacción con radiación, resonancia magnética, Moessbauer Efecto.