Gravitation as a Plastic Distortion of the Lorentz Vacuum

In this paper we present a theory of the gravitational field where this field (a kind of square root of g) is represented by a (1,1)-extensor field h describing a plastic distortion of the Lorentz vacuum (a real substance that lives in a Minkowski spacetime) due to the presence of matter. The field h distorts the Minkowski metric extensor in an appropriate way (see below) generating what may be interpreted as an effective Lorentzian metric extensor g and also it permits the introduction of different kinds of parallelism rules on the world manifold, which may be interpreted as distortions of the parallelism structure of Minkowski spacetime and which may have non null curvature and/or torsion and/or nonmetricity tensors. We thus have different possible effective geometries which may be associated to the gravitational field and thus its description by a Lorentzian geometry is only a possibility, not an imposition from Nature. Moreover, we developed with enough details the theory of multiform functions and multiform functionals that permitted us to successfully write a Lagrangian for h and to obtain its equations of motion, that results equivalent to Einstein field equations of General Relativity (for all those solutions where the manifold M is diffeomorphic to R^4. However, in our theory, differently from the case of General Relativity, trustful energy-momentum and angular momentum conservation laws exist. We express also the results of our theory in terms of the gravitational potential 1-form fields (living in Minkowski spacetime) in order to have results which may be easily expressed with the theory of differential forms. The Hamiltonian formalism for our theory (formulated in terms of the potentials) is also discussed. The paper contains also several important Appendices that complete the material in the main text.Comment: Misprints and typos have been corrected, Chapter 7 have been improved. Appendix E has been reformulated and Appendix F contains new remarks which resulted from a discussion with A. Lasenby. A somewhat modified version has been published in the Springer Series: Fundamental Theories of Physics vol. 168, 2010. http://www.ime.unicamp.br/~walrod/plastic2014.pd

Light-based nonverbal signaling with passive demonstrations for mobile service robots

With emerging applications in robotics that have the potential to bring them into our daily lives, it is expected for them to not only operate in close proximity to humans but also interact with them as well. When operating in crowded, human-populated environments there are many communication challenges faced by robots due to variable levels of interactions (e.g. asking for help, giving information, or navigating near humans). A crucial factor for success in these interactions is a robot’s ability to express information about their intent, actions, and knowledge to co-located humans. Many of the robot platforms developed for service roles have non-anthropomorphic form factors in order to simplify and tailor them to their jobs. Due to a lack of anthropomorphic features, these types of robots primarily communicate using an on-screen display and/or spoken language. To overcome the limitation of not communicating as people do, we explore the viability of nonverbal light-based signals as a communication modality for mobile service robots. These types of signals have many benefits over existing modalities which they can either complement or replace when appropriate, such as having long-range visibility and persisting over time. We present a novel light-based signal control architecture implemented as a custom Robot Operating System (ROS) software package generalized to allow for various signal implementations. We implement our framework on a BWIBot, an autonomous mobile service robot created as part of the Building-Wide Intelligence Project, and evaluate its validity through a real-world user study on the scenario where a robot and human are traversing a shared corridor from opposite ends, and the potential conflict created when their paths meet. Our results demonstrate that exposing users to the robot’s use of an animated light signal only once prior to when it is information critical for the user is sufficient to disambiguate its meaning, and thus greatly enhances its utility in-situ, with no direct instruction or training to the user. These findings suggest a paradigm of passive demonstration of light-based signals in future applications.Computer Science

Studies on the passive transfer of resistance to Fasciola hepatica

The main aims of this study were to determine the times after infection or reinfection that immune serum from bullocks infected with Fasciola hepatica would transfer protection to rats and to de¬ vise means of sensitising bullocks by which the animals could be stimulated to produce a strongly protective immune serum.The serological response by enzyme-linked immunosorbent assay (ELISA), using either a somatic or a metabolic antigen, the serum glutamic dehydrogenase (GD) activities, and the peripheral eosinophil counts were monitored from both bullocks and rats during the infections.Firstly, two bullocks of about 18 months of age were given an initial infection of 1,000 metacercariae of F. hepatica and immune sera (IBS) collected at three-weekly intervals and passively trans¬ ferred to rats, to monitor their protective effect. Serum obtained during the prepatent period, 6-9 weeks after initial infection, gave partial protection. In an attempt to obtain a more strongly protect¬ ive serum that could transfer a more effective resistance, the bull¬ ocks were given two more infections (22 weeks apart) of 1,000 meta¬ cercariae to each animal on each occasion. However, the IBS from previously infected bullocks gave only relatively weak protection. Indeed IBS from one of the bullocks (9U)> collected after repeated infections was not protective at all.From this study it is clear that juvenile flukes are immunogenic, giving rise to humoral protective agents, since IBS collected at weeks 6-9 after initial infection was protective. Conversely, it is also clear that repeated oral infection is not a suitable method for enhancing the humoral protective response, probably because the challenge flukes are soon killed by the cellular response in previously sensitised animals.It was thought that age might influence the ability of immune serum from bullocks to transfer resistance. Accordingly three adult mature bullocks (b-S years old) were infected with 1,000 metacercariae of F. hepatica and 30 weeks later another 1,000 metacercariae were administered. However the immune serum collected at week 9 from one of the bullocks was not protective while that from the other two was rather weak. After secondary infection, the immune sera collected from 204 appeared to give some protection but not that from 203 or M199.The opposite hypothesis was then examined, namely that older, immunologically mature animals rely more on a cellular response and consequently have a weaker humoral protective response. Accordingly four immature bullocks (6 months old) were infected with 1,000 meta¬ cercariae once, IBS collected six weeks later and again when the animals were killed nine weeks after infection. However these sera were not strongly protective to naive rats.Following initial infection the animals tended to show a biphasic reaction in all the monitored parameters. However, because of great variations between animals, the pattern for some of the parameters was not always clear in individual bullocks.The first ELISA peak occurred before patency and the second after patency. This phenomenon of a biphasic' serological response was ob¬ served by Gundlach (1971) in rabbits, using metabolic or somatic antigen in complement fixation tests. It is suggested that the first ELISA. peak coincides with liver migration and the active feeding by vi. the juvenile flukes on the parenchymal cells, while the second peak, which is usually lower than the first peak, coincides with an immune response to products released from flukes in the bile duct.Following repeated infections, the ELISA values tended to be higher than those following primary infection. There was, therefore, no evidence of any direct relationship between the ELISA value and the protective effect of the sera. At the same time the serum GD activities and the peripheral eosinophil counts tended to be lower and faecal egg counts were very low after repeated infections, showing that the animals had resisted the challenge infections.The GE and eosinophil levels rose to an initial peak at week with the maximum values being reached at weeks 12-16^ in bullocks. Again it is suggested that the first peak results from the direct effect of the parenchymal liver migration by the juvenile flukes, while the second peak probably results from the combined effect of both the fibrotic healing process in damaged liver and the presence of antigen-antibody complex in the liver.It therefore appears that, although the bullocks previously sensitised by oral infection had acquired strong resistance against challenge infections, this was not related to the increased concen¬ trations of antibodies in their immune serum but was more likely to be a cellular effect. Thus it was thought that other means than simply challenging previously infected,animals would be necessary to produce more strongly protective antisera. Implantation of encapsulated flukes, which might be protected from the cellular protective mechanisms in the hosts and so be able to release the protective-inducing immunogen for a more extended period, was therefore adopted,A preliminary study on the effect of implanting flukes in diffusion chambers on the immune response of animals was carried out in rats. The ELISA results suggested that there was an elevated ELISA response in the rats following implantation but this was short¬ lived. In the definitive experiment in bullocks, for logistic reasons, the serum was collected eight weeks after implantation, when a shorter period might have been optimal. Nevertheless, in the associated passive transfer study it was found that immune serum from the im¬ planted bullocks tended to give better protection, except in one animal, than that from orally challenged bullocks. However, these results cannot be considered conclusive because of the limited numbers of experimental animals used.The relatively short elevation in the ELISA value after implantation was attributed to encapsulation of the diffusion chambers "containing the flukes by the host's cellular reaction against diffusing metabolic antigens