In this study the production of extracellular polysaccharides by the non-pathogenic soil bacteria Arthrobacter viscosus has been investigated. Different variables affecting extracellular polysaccharide production such as the carbon source (glucose or xylose), the agitation speed and the pH have been analysed.
In a first stage, experiments in shaken conical flasks (250 ml), containing 50 ml of culture medium, were carried out. Using xylose (25 g/l) as the carbon source at an initial pH 8 improved the extracellular polysaccharides levels obtained.
In a second stage, the experiments were scaling in bioreactors. Cultivation was carried out in discontinuous mode and with/without pH control. Polysaccharide production reached a maximum of 10 g of crude product per litre of growth medium after 14 days and the relationship between product formation and cell growth of A. viscosus is 2.7 g polysaccharide per gram biomass. This production was obtained at the optimal conditions determined with pH control at pH 7, xylose as carbon source (25 g/l) and an agitation rate of 800 rpm. 相似文献
Discussed in this paper is the Cartesian stiffness matrix, which recently has received special attention within the robotics
research community. Stiffness is a fundamental concept in mechanics; its representation in mechanical systems whose potential
energy is describable by a finite set of generalized coordinates takes the form of a square matrix that is known to be, moreover,
symmetric and positive-definite or, at least, semi-definite. We attempt to elucidate in this paper the notion of “asymmetric
stiffness matrices”. In doing so, we show that to qualify for a stiffness matrix, the matrix should be symmetric and either
positive semi-definite or positive-definite. We derive the conditions under which a matrix mapping small-amplitude displacement
screws into elastic wrenches fails to be symmetric. From the discussion, it should be apparent that the asymmetric matrix
thus derived cannot be, properly speaking, a stiffness matrix. The concept is illustrated with an example. 相似文献
In the era of the nanometer CMOS technology, due to stringent system requirements in power, performance and other fundamental physical limitations (such as mechanical reliability, thermal constraints, overall system form factor, etc.), future VLSI systems are relying more on ultra-high data rates (up to 100 Gbps/pin or 20 Tbps aggregate), scalable, re-configurable, highly compact and reliable interconnect fabric. To overcome such challenges, we first explore the use of multiband RF/wireless-interconnects wh... 相似文献
This paper presents a novel learning methodology based on a hybrid algorithm for interval type-2 fuzzy logic systems. Since only the back-propagation method has been proposed in the literature for the tuning of both the antecedent and the consequent parameters of type-2 fuzzy logic systems, a hybrid learning algorithm has been developed. The hybrid method uses a recursive orthogonal least-squares method for tuning the consequent parameters and the back-propagation method for tuning the antecedent parameters. Systems were tested for three types of inputs: (a) interval singleton, (b) interval type-1 non-singleton, and (c) interval type-2 non-singleton. Experiments were carried out on the application of hybrid interval type-2 fuzzy logic systems for prediction of the scale breaker entry temperature in a real hot strip mill for three different types of coil. The results proved the feasibility of the systems developed here for scale breaker entry temperature prediction. Comparison with type-1 fuzzy logic systems shows that hybrid learning interval type-2 fuzzy logic systems provide improved performance under the conditions tested. 相似文献
This paper outlines a novel approach to the modeling and analysis of impact involving multibody systems. This approach is
based on an analysis of energy absorption and restitution during impact, using a decomposition of the kinetic energy, which
decouples the parts associated with the spaces of admissible and constrained motions of the underlying unilateral constraints.
Such a decomposition turns out to be useful in the analysis of energy dissipation during impact, and leads to a generalized
definition of the energetic coefficient of restitution, which targets particularly collisions in multibody systems. The applicability
of the approach reported is investigated by conducting an experimental study on a robotic testbed. It is shown that impact
between multibody systems is considerably affected not only by the local dynamics characteristics of the interacting bodies,
but also the configuration of the whole multibody system. The results reported here show that our decomposition can offer
a sound characterization of impact in several problems of multibody systems. 相似文献
To ascertain the possible implications of the nitric oxide (NO*) producing system in striatal senescence, and by using immunohistochemistry and image-processing approaches, we describe the presence of the enzyme nitric oxide synthase (NOS), the NADPH-diaphorase (NADPH-d) histochemical marker, and nitrotyrosine-derived complexes (N-Tyr) in the striatum of adult and aged rats. The results showed neuronal NOS immunoreactive (nNOS-IR) aspiny medium-sized neurons and nervous fibres in both age groups, with no variation in the percentage of immunoreactive area but a significant decrease in the intensity and in the number of somata with age, which were not related to the observed increase with age of the striatal bundles of the white matter. In addition, NADPH-d activity was detected in neurons with morphology similar to that of the nNOS-IR cells; a decrease in the percentage of area per field and in the number of cells, but an increase in the intensity of staining for the NADPH-d histochemical marker, were detected with age. The number of neuronal NADPH-d somata was higher than for the nNOS-IR ones in both age groups. Moreover, N-Tyr-IR complexes were observed in cells (neurons and glia) and fibres, with a significant increase in the percentage of the area of immunoreaction, related to the increase of white matter, but a decrease in intensity for the aged group. On the other hand, we did not detect the inducible isoform (iNOS) either in adult or in aged rats. Taken together, these results support the contention that NADPH-d staining is not such an unambiguous marker for nNOS, and that increased protein nitration may participate in striatal aging. 相似文献
This paper presents a conceptual model of a hybrid electric sailboat in which energy from electric grid is stored in batteries and energy from renewable energies (eolic, solar and hydro) is stored as hydrogen. The main objective of this model is to study the viability of electrifying traditional sailboats with internal combustion engines into hybrid systems with batteries and fuel cell. The most important advantage of this design is the possibility to reduce up to zero emissions of traditional sailboat. Conversion of renewable energy to hydrogen is performed through an electrolyzer and post conversion to energy is carried out by a fuel cell. The fuel cell with the batteries forms the hybrid system (batteries-fuel cell) for propulsion electrical energy supply. In order to model the boat dynamic and energy systems, modular mathematical models were developed under Matlab®-Simulink®, using a fixed-step solver for the simulation of global model. A simulated logic controller manages the global model. In this paper, many models have been used: some of them are based in literature models and others were developed from experimental data. A control strategy has also been developed to manage energy flows and then it has been embedded to Matlab® language. The global model permits test the performance of the sailboat. 相似文献
Crises are common in today's unpredictable environment rising the importance of crisis response strategies. Two societies in Europe are chosen: Finland, where trust in society is generalized to institutions, and Spain, where trust in society remains on the level of individuals. Using the results of the European Communication Monitor 2013 survey on crisis communication, we explored three hypotheses: “certain types of crises are often met with certain types of strategies,” “cultural context makes some crises more likely than others,” and “cultural context makes some response strategies more likely than others.” We find evidence for all three hypotheses and discuss our findings about perceived differences in the two societies. The results show that the cultural context plays an important role for crisis communication. 相似文献
Mobile technology plays an increasing role in museum and cultural heritage contexts. In most cases, these tools support the relatively passive consumption of expert interpretations, or the unguided generation of content by users. This paper explores the potential for technologies to help museum visitors, encountering unfamiliar objects, to engage with them as a skilled professional interpreter would, through structured mobile experiences that focus on creating multimedia content. We explore this concept in the area of artefact interpretation and specifically how to enact a structured process of interpretation, as would commonly be taught in courses dedicated to the analytical diagnostics of visual evidence, such as Classical Archaeology or Art History. We discuss two field trials of prototype systems through which the structured creation of multimedia forms a basis for learning to interpret historical artefacts conducted in contexts of both formal and informal learning. By describing, implementing, and evaluating this approach, we contribute understanding of a new way to conceptualise active engagement in museum contexts, through the effective use of scaffolding and user generation of multimedia. We identify issues around the properties and flexibilities of multiple media for this purpose, links between provision for procedural and factual learning, and the value of media creation-based structures in improving the skills and confidence to interpret. 相似文献