IK-FA, a new heuristic inverse kinematics solver using firefly algorithm

In this paper, a heuristic method based on Firefly Algorithm is proposed for inverse kinematics problems in articulated robotics. The proposal is called, IK-FA. Solving inverse kinematics, IK, consists in finding a set of joint-positions allowing a specific point of the system to achieve a target position. In IK-FA, the Fireflies positions are assumed to be a possible solution for joints elementary motions. For a robotic system with a known forward kinematic model, IK-Fireflies, is used to generate iteratively a set of joint motions, then the forward kinematic model of the system is used to compute the relative Cartesian positions of a specific end-segment, and to compare it to the needed target position. This is a heuristic approach for solving inverse kinematics without computing the inverse model. IK-FA tends to minimize the distance to a target position, the fitness function could be established as the distance between the obtained forward positions and the desired one, it is subject to minimization. In this paper IK-FA is tested over a 3 links articulated planar system, the evaluation is based on statistical analysis of the convergence and the solution quality for 100 tests. The impact of key FA parameters is also investigated with a focus on the impact of the number of fireflies, the impact of the maximum iteration number and also the impact of (a, ß, ¿, d) parameters. For a given set of valuable parameters, the heuristic converges to a static fitness value within a fix maximum number of iterations. IK-FA has a fair convergence time, for the tested configuration, the average was about 2.3394 × 10-3 seconds with a position error fitness around 3.116 × 10-8 for 100 tests. The algorithm showed also evidence of robustness over the target position, since for all conducted tests with a random target position IK-FA achieved a solution with a position error lower or equal to 5.4722 × 10-9.Peer ReviewedPostprint (author's final draft

[The cancer, a defeat of the psyche?]

Patients and families often put forward psychosocial determinants to explain occurring or progression of cancer disease. The idea of a psychogenesis in cancer is widely spread by the surrounding culture. Nevertheless, the scientific research in this field brought very contradictory results, and often rests on debatable methods, Some authors hypothesize that a type C personality predisposes to cancer. But so far, most of Prospective studies analysing the association between C traits and this disease have been negative. Results of semi-prospective studies in which patients are enlisted before a diagnostic investigation, are difficult to interpret, because the starting features can partly result from the stress of this investigation, The same problem interferes with most studies about the association between alexithymia and cancer. The reliable works analysing the impact of depression most often conclude in favour of a non-existent ora weak risk, and do not allow defining it as a well established risk factor. Most of prospective studies about the link between stress and cancer are negative, Moreover, they index stressful life events occurred for a few years before the diagnosis, that is to say during a too short delay to be allowed to incriminate them in the supervening of the disease. The question of the possible impact of coping styles with cancer on its evolution also remains debated. Some studies for instance plead in favour of a beneficial effect of fighting spirit or denial, hut they are contradicted by other studies. All this forces us to be very careful when discussing the possible links between psyche and cancer. It is important to underline the hypothetical nature of these relationships. Psychosomatic explanations risk to be used to fill in gaps of knowledge, and to give us the illusion that we can avoid or control a disease which escapes us, They especially risk to make the patients guilty of their cancer or its evolution, through an inadequate point of view which does not take the complexity in stake into account

Le spectre clinique des déficits en cobalamines en Tunisie

International audiencePurpose: the aim of this study was to determine the prevalence of cobalamin (vitamin B12) deficiency in different populations of patients with clinical manifestations associated or secondary to cobalamin or folates deficiency and to analyse the demographic, clinical, paraclinical investigations in cobalamin deficient patients in Tunisia. Methods: it was a prospective (19992001) multicenter study of 604 patients divided into four groups. The first group is composed of 478 consecutive patients with anaemia and/or macrocytosis with megaloblastic haemopoiesis on bone marrow examination without myelodyslasic or malignancy signs. The second group is made up of 34 patients with unexplained neurological symptoms without the presence of anaemia. The third group was composed of 82 invidious with isolated psychiatric disorders and the 10 patients with Hashimoto thyroiditis constituted the last,group. Results: serum cobalamin level was low in 98%, 23%, 14% of cases, respectively, in the first three groups. Only one case of patients with Hashimoto thyroiditis has serum cobalamin deficiency. Pernicious anaemia (Biermer's disease) was established by dual isotope schilling examination in 103 patients among a sample of 120 serum cobalamin deficient patients (86%). The median age at presentation was 45.5 years. Severe chronic atrophic gastritis was diagnosed in 97.5% of patients with Biermer's disease. Serum antibodies against intrinsic factor and gastric parietal cells were detected in (42.5%) and (60.6%) patients, respectively; (25.5%) patients had the both types of antibodies. 23.4% patients were positive for antithyroid antibodies. Anti-nuclear antibodies were detected in 3% patients. Conclusion: an interesting finding of our study was the high frequency of cobalamin deficiency in Tunisia, particularly in relative young patients. Our patients had classic features of florid cobalamin deficiency (severe haematological manifestations and neuro-psychiatric disorders). The main underlying causes of such deficiencies were Biermer's disease. Subtle clinical manifestations should be recognized and investigated even in young patients at risk.Objectif : déterminer la prévalence des déficits en cobalamines (vitamine B12) chez différentes populations de patients présentant des manifestations cliniques pouvant être associées ou secondaires à un déficit en vitamine B12 ou en folates et analyser les données démographiques, cliniques et paracliniques chez les patients déficitaires en vitamine B12 en Tunisie. Méthodes : il s’agissait d’une étude prospective (1999-2001), multicentrique, incluant 604 patients répartis en quatre groupes : le premier groupe comportait 478 patients consécutifs présentant une hématopoïèse mégaloblastique sans signe de myélodysplasie avec ou sans anémie. Le deuxième groupe était composé de 34 patients présentant un tableau neurologique inexpliqué sans anémie mégaloblastique associée. Le troisième groupe était constitué de 82 individus présentant des manifestations psychiques isolées. Le quatrième groupe comportait dix patients ayant une thyroïdite d’Hashimoto. Résultats : le taux des cobalamines sériques était bas dans 98 %, 23 %, 14 % des cas, respectivement, des trois premiers groupes, alors qu’un seul patient du quatrième groupe était déficitaire en vitamine B12. Le test de Schilling réalisé chez un échantillon de 120 patients déficitaires en cobalamines a montré que 103 patients (86 %) étaient atteints par la maladie de Biermer. Ils avaient une médiane d’âge de 45,5 ans ; 97,5 % d’entre eux avaient une gastrite fundique atrophique sévère. L’Helicobacter pylori a été détecté chez seulement 5 parmi les 43 patients où il a été histologiquement recherché. Le bilan auto-immun chez ces patients montre : anticorps anti-cellules pariétales : 60,6 % ; anticorps anti-facteur intrinsèque : 42,5 % ; concordance entre les 2 anticorps : 48% ; anticorps anti-thyroïdiens : 23,4 % (2 % chez les témoins normaux) ; anticorps anti-nucléaire : 3 %. Conclusion : notre travail souligne la fréquence élevée des déficits en vitamine B12 en Tunisie particulièrement chez les sujets relativement jeunes. Nos patients présentaient un tableau clinique des formes florides des déficits en cobalamines (manifestations hématologiques sévères et troubles neuropsychiatriques). La cause principale sous-jacente de ces déficits était la maladie de Biermer. Les formes cliniques frustes méritent d’être recherchées et explorées même chez les sujets jeunes à risque