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

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

Impact of technically qualified surgeons on laparoscopic colorectal resection outcomes : results of a propensity score-matching analysis

Background The Endoscopic Surgical Skill Qualification System (ESSQS) was introduced in Japan to improve the quality of laparoscopic surgery. This cohort study investigated the short- and long-term postoperative outcomes of colorectal cancer laparoscopic procedures performed by or with qualified surgeons compared with outcomes for unqualified surgeons. Methods All laparoscopic colorectal resections performed from 2010 to 2013 in 11 Japanese hospitals were reviewed retrospectively. The procedures were categorized as performed by surgeons with or without the ESSQS qualification and patients' clinical, pathological and surgical features were used to match subgroups using propensity scoring. Outcome measures included postoperative and long-term results. Results Overall, 1428 procedures were analysed; 586 procedures were performed with ESSQS-qualified surgeons and 842 were done by ESSQS-unqualified surgeons. Upon matching, two cohorts of 426 patients were selected for comparison of short-term results. A prevalence of rectal resection (50.3 versus 40.5 per cent; P < 0.001) and shorter duration of surgery (230 versus 238 min; P = 0.045) was reported for the ESSQS group. Intraoperative and postoperative complication and reoperation rates were significantly lower in the ESSQS group than in the non-ESSQS group (1.2 versus 3.6 per cent, P = 0.014; 4.6 versus 7.5 per cent, P = 0.025; 1.9 versus 3.9 per cent, P = 0.023, respectively). These findings were confirmed after propensity score matching. Cox regression analysis found that non-attendance of ESSQS-qualified surgeons (hazard ratio 12.30, 95 per cent c.i. 1.28 to 119.10; P = 0.038) was independently associated with local recurrence in patients with stage II disease. Conclusion Laparoscopic colorectal procedures performed with ESSQS-qualified surgeons showed improved postoperative results. Further studies are needed to investigate the impact of the qualification on long-term oncological outcomes