Stress response inside perturbed particle assemblies

The effect of structural disorder on the stress response inside three dimensional particle assemblies is studied using computer simulations of frictionless sphere packings. Upon applying a localised, perturbative force within the packings, the resulting {\it Green's} function response is mapped inside the different assemblies, thus providing an explicit view as to how the imposed perturbation is transmitted through the packing. In weakly disordered arrays, the resulting transmission of forces is of the double-peak variety, but with peak widths scaling linearly with distance from the source of the perturbation. This behaviour is consistent with an anisotropic elasticity response profile. Increasing the disorder distorts the response function until a single-peak response is obtained for fully disordered packings consistent with an isotropic description.Comment: 8 pages, 7 figure captions To appear in Granular Matte

An intelligent controller for robot contact and non-contact task control

An architecture for intelligent control of a robot that interacts with a dynamically changing environment is proposed. The problems that are encountered in the implementations of low-level controllers for such robotics applications and their inherent limitations are outlined. An intelligent monitor is proposed to overcome these problems. Since this intelligent interface can change the desired trajectory and thereby affect the stability of the low-level controller, a stability analysis of the integrated controller and the interface is provided. This conceptual architecture is an attempt to emulate humans in employing common-sense reasoning in dynamic decision making and control. It is strongly believed that this approach will enable the controller to generate control actions in a more 'humanlike' manner than the current implementations of learning control

Anther Dehiscence And Circumscription Of Miconia Sect. Hypoxanthus (melastomataceae)

While most Melastomataceae have poricidal anthers, Miconia sect. Hypoxanthus (former sect. Chaenanthera) has anthers dehiscing by longitudinal pores, resembling rimose openings. Anther development of three species (Miconia pusilliflora and M. laticrenata from this section and M. cinnamomifolia from sect. Glossocentrum) studied through SEM and light microscopy showed that all have an epidermis with a thick and striate cuticle, except for the dehiscence area. This area is covered by a non-striate epidermis which is associated with the septum that lies between the two thecae. During dehiscence the septum holds the non-striate epidermis, which is torn at the margins of the dehiscence area. Since anther opening of all three species follows the same pattern, in terms of tissues and mechanisms, we conclude that the circumscription of Miconia sect. Hypoxanthus should comprise all species with stamens that dehisce along the septum, resulting in narrow openings that extend from the anther apex to the base (as in M. pusilliflora) or from the apex until half of the anther length (as in M. laticrenata). Miconia section Chaenopleura also has anthers opening by longitudinal slits, but these expose four locules, instead of the two in Hypoxanthus.581195203Baumgratz, J.F.A., Miconias do estado do Rio de Janeiro. Seção Chaenanthera Naud. (Melastomataceae) (1984) Rodriguésia, 36, pp. 45-58Souza, M.L.D.R., Woodgyer, E.M., Nic Lughada, E.M., Polysporangiate anthers described for the first time in Melastomataceae (1996) Kew Bull., 51, pp. 133-144Clausing, G., Renner, S.S., Molecular phylogenetics of Melastomataceae and Memecylaceae: Implications for character evolution (2001) Amer. J. Bot., 88, pp. 486-498Cogniaux, A., Melastomataceae, Miconieae (1886) Flora Brasiliensis, 14 (4), pp. 64-558. , C. E P. von Martius, A. G. Eichler & I. Urban (eds.)Melastomataceae (1891) Monographiae Phanerogamarum, 7. , A. De Candolle & C. De Candolle (eds.). G. Masson, Paris, FranceEyde, R.H., Teeri, J.A., Floral Anatomy of Rhexia virginica (Melastomataceae) (1967) Rhodora, 69, pp. 163-178Fahn, A., (1990) Plant Anatomy, , Pergamon Press, Oxford, U.KGoldenberg, R., (2000) O Gênero Miconia Ruiz & Pav. (Melastomataceae): I. Listagens AnalíticasII. Revisão Taxonômica Seção Hypoxanthus (Rich. ex DC.) Hook. f. D. Phil, , Thesis, Universidade Estadual de Campinas, Campinas, BrazilGroenendijk, J.P., Bouman, F., Cleef, A., An exploratory study on seed morphology of Miconia (Melastomataceae), with taxonomic and ecological implications (1996) Acta Bot. Neerl., 45, pp. 323-344Jensen, W.A., (1962) Botanical Histochemistry: Principles and Practice, , W. H. Freeman, San Francisco, U.S.AJohansen, D.A., (1940) Plant Microtechnique, , McGraw-Hill Book Company, New York, U.S.AJohri, B.M., Ambegaokar, K.B., Srivastava, P.S., (1992) Comparative Embryology of Angiosperms, , Springer-Verlag, Berlin, GermanyMatthews, J.R., Maclachlan, C.M., The structure of certain poricidal anthers (1929) Trans. & Proc. Bot. Soc. Edinburgh, 30, pp. 104-122Medeiros, J.D., Morretes, B.L., The embryology of Miconia cabucu (Melastomataceae) (1996) Cytologia, 61, pp. 83-91Naudin, C.V., Melastomacearum monographicae descriptiones (1851) Ann. Sci. Nat. Bot., Sér., 3 (16), pp. 83-246Renner, S.S., Phylogeny and classification of the Melastomataceae and Memecylaceae (1993) Nordic J. Bot., 13, pp. 519-540Subramanyam, K., An embryological study of Melastoma malabathricum L. (1948) J. Indian Bot. Soc., 27, pp. 11-19Tobe, H., Raven, P.H., The embryology and relationships of Dactylocladus (Crypteroniaceae) and a discussion of the family (1987) Bot. Gaz., 148, pp. 103-111Wurdack, J.J., Melastomataceae of Santa Catarina (1962) Sellowia, 14, pp. 109-217Melastomataceae (1973) Flora de Venezuela, 8, pp. 1-819. , T. Lasser (ed.)Melastomataceae (1980) Flora of Ecuador, 13, pp. 1-406. , G. Harling & B. Sparre (eds.)Ziegler, A., Beiträge zur Kenntnis des Androceums und der Samenentwicklung einiger Melastomataceen (1925) Bot. Arch., 9, pp. 398-46