Cooperative object transport with a swarm of e-puck robots: robustness and scalability of evolved collective strategies

Cooperative object transport in distributed multi-robot systems requires the coordination and synchronisation of pushing/pulling forces by a group of autonomous robots in order to transport items that cannot be transported by a single agent. The results of this study show that fairly robust and scalable collective transport strategies can be generated by robots equipped with a relatively simple sensory apparatus (i.e. no force sensors and no devices for direct communication). In the experiments described in this paper, homogeneous groups of physical e-puck robots are required to coordinate and synchronise their actions in order to transport a heavy rectangular cuboid object as far as possible from its starting position to an arbitrary direction. The robots are controlled by dynamic neural networks synthesised using evolutionary computation techniques. The best evolved controller demonstrates an effective group transport strategy that is robust to variability in the physical characteristics of the object (i.e. object mass and size of the longest object’s side) and scalable to different group sizes. To run these experiments, we designed, built, and mounted on the robots a new sensor that returns the agents’ displacement on a 2D plane. The study shows that the feedback generated by the robots’ sensors relative to the object’s movement is sufficient to allow the robots to coordinate their efforts and to sustain the transports for an extended period of time. By extensively analysing successful behavioural strategies, we illustrate the nature of the operational mechanisms underpinning the coordination and synchronisation of actions during group transport

Cyclical and Patch-Like GDNF Distribution along the Basal Surface of Sertoli Cells in Mouse and Hamster Testes

BACKGROUND AND AIMS: In mammalian spermatogenesis, glial cell line-derived neurotrophic factor (GDNF) is one of the major Sertoli cell-derived factors which regulates the maintenance of undifferentiated spermatogonia including spermatogonial stem cells (SSCs) through GDNF family receptor α1 (GFRα1). It remains unclear as to when, where and how GDNF molecules are produced and exposed to the GFRα1-positive spermatogonia in vivo. METHODOLOGY AND PRINCIPAL FINDINGS: Here we show the cyclical and patch-like distribution of immunoreactive GDNF-positive signals and their close co-localization with a subpopulation of GFRα1-positive spermatogonia along the basal surface of Sertoli cells in mice and hamsters. Anti-GDNF section immunostaining revealed that GDNF-positive signals are mainly cytoplasmic and observed specifically in the Sertoli cells in a species-specific as well as a seminiferous cycle- and spermatogenic activity-dependent manner. In contrast to the ubiquitous GDNF signals in mouse testes, high levels of its signals were cyclically observed in hamster testes prior to spermiation. Whole-mount anti-GDNF staining of the seminiferous tubules successfully visualized the cyclical and patch-like extracellular distribution of GDNF-positive granular deposits along the basal surface of Sertoli cells in both species. Double-staining of GDNF and GFRα1 demonstrated the close co-localization of GDNF deposits and a subpopulation of GFRα1-positive spermatogonia. In both species, GFRα1-positive cells showed a slender bipolar shape as well as a tendency for increased cell numbers in the GDNF-enriched area, as compared with those in the GDNF-low/negative area of the seminiferous tubules. CONCLUSION/SIGNIFICANCE: Our data provide direct evidence of regionally defined patch-like GDNF-positive signal site in which GFRα1-positive spermatogonia possibly interact with GDNF in the basal compartment of the seminiferous tubules

Histochemical and chronological analysis of mouse submandibular gland parenchyma subjected to abrupt reperfusion

We examined the effects of abrupt reperfusion on the mouse submandibular gland parenchyma and determined the degree of recovery from tissue damage. A main trophic artery supplying the gland was ligated with silk thread, and the ligature was then released after a variable period. The gland was removed at various times after reperfusion and then examined immunohistochemically and ultrastructurally. With reperfusion after 15 or 30 min of ligation, the tissue damage to the glands was slight or inapparent. With reperfusion after 1 or 3 h of ligation, collapse of the acini and the ducts was observed in parts of the lobules, but restoration of the parenchymal structures occurred, with the appearance of PCNA-positive cells, although there were differences in the level of restoration. After 6 h of ligation, most of the normal parenchymal cells had disappeared by the 5th and 7th days after reperfusion, and apoptosis and necrosis were present. These findings suggest that if interruption of the blood supply to the submandibular gland parenchyma is limited to within a few hours, then tissue repair after reperfusion is possible, although this will differ according to the level of damage, because the acini and the ducts reappear, probably with proliferation of parenchymal cells

Minimal maps between the hyperbolic discs and generalized Gauss maps ofmaximal surfaces in the anti-de sitter 3-space

Problems related to minimal maps are studied. In particular, we prove an existence result for the Dirichlet problem at infinity for minimal diffeomorphisms between the hyperbolic discs. We also give a representation formula for a minimal diffeomorphism between the hyperbolic discs by means of the generalized Gauss map of a complete maximal surface in the anti-de Sitter 3-space

Modern management for brain metastasis patients using stereotactic radiosurgery: literature review and the authors’ gamma knife treatment experiences

Yoshinori Higuchi,1,* Masaaki Yamamoto,2,* Toru Serizawa,3 Hitoshi Aiyama,2 Yasunori Sato,4 Bierta E Barfod2 1Department of Neurological Surgery, Chiba University Graduate School of Medicine, Chiba, Japan; 2Katsuta Hospital Mito Gamma House, Hitachi-Naka, Japan; 3Tokyo Gamma Unit Center, Tsukiji Neurological Clinic, Tokyo, Japan; 4Department of Global Clinical Research, Chiba University Graduate School of Medicine, Chiba, Japan *These authors contributed equally to this work Abstract: Historically, whole brain radiotherapy was administered to most patients with brain metastases. However, over the past three decades, stereotactic radiosurgery (SRS), targeted at individual cranial lesions, has been accepted widely. In this study, based on the authors’ experiences along with published data, recent trends in SRS for brain metastases are discussed. This article focuses on the following issues: 1) How many tumors can or should be treated with SRS? 2) Two-/three-staged SRS for relatively large tumors, 3) post- or preoperative SRS, and 4) repeat SRS. Keywords: brain metastases, radiotherapy, radiosurgery, gamma knif

Lifting Mechanism for Payload Transport by Collaborative Mobile Robots

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