The application of multi-objective optimisation to evolutionary robotics is receiving increasing attention. A survey of the literature reveals the different possibilities it offers to improve the automatic design of efficient and adaptive robotic systems, and points to the successful demonstrations available for both task-specific and task-agnostic approaches (i.e., with or without reference to the specific design problem to be tackled). However, the advantages of multi-objective approaches over single-objective ones have not been clearly spelled out and experimentally demonstrated. This paper fills this gap for task-specific approaches: starting from well-known results in multi-objective optimisation, we discuss how to tackle commonly recognised problems in evolutionary robotics. In particular, we show that multi-objective optimisation (i) allows evolving a more varied set of behaviours by exploring multiple trade-offs of the objectives to optimise, (ii) supports the evolution of the desired behaviour through the introduction of objectives as proxies, (iii) avoids the premature convergence to local optima possibly introduced by multi-component fitness functions, and (iv) solves the bootstrap problem exploiting ancillary objectives to guide evolution in the early phases. We present an experimental demonstration of these benefits in three different case studies: maze navigation in a single robot domain, flocking in a swarm robotics context, and a strictly collaborative task in collective robotics. 相似文献
OBJECTIVE--To examine the relations among tissue plasminogen activator antigen, plasminogen activator inhibitor, the lupus anticoagulant, and anticardiolipin antibodies in patients with systemic lupus erythematosus. DESIGN--Prospective study of blood samples (a) from selected patients with systemic lupus erythematosus whose disease was and was not complicated by a history of thrombosis or recurrent abortions, or both, and (b) from a series of healthy controls with a similar age and sex distribution. SETTING--University based medical clinic. SUBJECTS--23 Patients with definite systemic lupus erythematosus (American Rheumatism Association criteria), of whom 11 (eight women) aged 26-51 had a history of thrombosis or recurrent abortions, or both, and 12 (10 women) aged 23-53 had no such history. 15 Healthy subjects (10 women) aged 25-58 served as controls. MAIN OUTCOME MEASURES--Tissue plasminogen activator concentrations, plasminogen activator inhibitor activities, detection of the lupus anticoagulant, and values of anticardiolipin antibodies in the two groups of patients and in the patients with a history of thrombosis or abortions compared with controls. Other measurements included concentrations of proteins that are known to change during the acute phase of systemic lupus erythematosus--namely, fibrinogen, C3 and C4, and C reactive protein. RESULTS--Patients with a history of thrombosis or abortions, or both, had significantly higher values of tissue plasminogen activator and plasminogen activator inhibitor than patients with no such history. A significant correlation between tissue plasminogen activator and plasminogen activator inhibitor (r = 0.80) was found only in the patients with a history of complications of their disease. The lupus anticoagulant was detected in six of the 11 patients with a history of thrombosis or abortions when tested by measuring the activated partial thromboplastin time but was found in all 11 patients when tested by measuring the diluted activated partial thromboplastin time. Nine of these 11 patients had raised values of anticardiolipin antibodies. The findings showed no relation to the activity of the disease. CONCLUSIONS--A significant correlation between tissue plasminogen activator concentrations and plasminogen activator inhibitor activities was found only in patients whose systemic lupus erythematosus was complicated by a history of thrombosis or recurrent abortions. The findings show that these patients have raised plasminogen activator inhibitor activities, and the frequent association between these raised activities and the presence of the lupus anticoagulant suggests that the two may be linked. 相似文献
Cordycepin sensitive mutants of Saccharomyces cerevisiae, which are permeable to 5'-deoxy-5'-methylthioadenosine (MTA), were used to study the fate of the methylthioribose carbons of this purine nucleoside. Evidence is presented for the recycling of the methylthio group and part of the ribose portion of MTA in a biosynthetic pathway which leads to the synthesis of methionine. The main pathway involves the phosphorylytic cleavage of MTA by MTA phosphorylase yielding 5-methylthioribose 1-phosphate and adenine as products. Loss of the phosphate group of 5-methylthioribose 1-phosphate, concurrent with the rearrangement of the ribose carbons, leads to the synthesis of 2-keto-4-methylthiobutyric acid. In the final step of the sequence, 2-keto-4-methylthiobutyric acid is converted to methionine via transamination. Several compounds not directly associated with the biosynthesis of methionine were also isolated. These compounds, which may arise through the degradation of intermediates in the pathway, were: 5'-methylthioinosine, a deaminated catabolite of MTA; 5-methylthioribose, a result of the phosphorylysis of 5-methylthioribose 1-phosphate, and 3-methylthiopropionaldehyde, 3-methylthiopropionic acid and 2-hydroxy-4-methylthiobutyric acid, all arising from the catabolism of 2-keto-4-methylthiobutyric acid. 相似文献
The influence of the maternal genotype (Canton-S, proficient in the repair of X-ray-induced chromosome breaks and ebony, less proficient in this regard) on the recovery of X-ray-induced autosomal (II–III) translocations and ring-X chromosome losses in mature spermatozoa was studied. In the first series of experiments, males carrying appropriate markers on their second and third chromosomes were irradiated and mated to Canton-S or ebony females and the frequencies of II–III translocations were determined. In the second series of experiments, males carrying ring-X chromosomes were irradiated in N2 or in O2, mated to Canton-S or ebony females and the frequencies of XO males were determined; additionally, under similar gas-treatment and radiation conditions, the pattern of egg-mortality was also assessed.
The data on translocations show that the yields are higher with ebony than with Canton-S females; these and earlier results on dominant lethals and sex-linked recessive lethals support the interpretation that the maternal repair system in the ebony strain is less proficient and more error-prone than that of the Canton-S strain.
Those on the losses of ring-X chromosomes demonstrate that (i) the absolute yields of XO males are lower with ebony than with Canton-S females irrespective of whether the parental males are irradiated in N2 or in O2; (ii) the exposure-frequency relationships are all linear, but the slopes are higher when the males are irradiated in O2 and are consistent with an oxygen-enhancement-ratio of about 1.5 and (iii) the relationships between the logarithm of egg-survival and XO male frequency are also linear, but the slopes for the O2 groups are lower than those for the N2 groups (slope ratios of 0.86–0.87).
The finding that at given survival levels, the XO frequencies are lower in the O2 than in the N2 groups of both the Canton-S and ebony series viewed in the context of the mechanisms that have been postulated to explain the loss of ring-X chromosomes in irradiated mature spermatozoa permits the following interpretation for the observed results: (i) a higher proportion of potential XO zygotes is lost through dominant lethality in the O2 groups than in the N2 ones presumably because the chromosome breaks induced in O2 are qualitatively different in the sense that they have higher probability to undergo reunions relative to restitution, compared with breaks induced under anoxia and (ii) this leads to lower than expected oxygen-enhancement ratios (i.e., expected on the basis of published data on sex-linked recessive lethals, another kind of genetic damage which shows a linear exposure-frequency relationship). 相似文献
We investigated larval sensitivity to UV and repair of UV- and X-ray-induced lesions in the DNA of the ebony strain compared to a wild-type strain (Canton S). The ebony strain was previously characterized as being more sensitive to UV-induced killing of embryos than Canton S. Also the ebony strain is more sensitive to X-rays for induction of larval killing, dominant lethals and recessive lethals. In this paper it is demonstrated that (1) ebony larvae are more sensitive to killing by UV and less proficient in photoreactivation (PR) ability than Canton S larvae; (2) the ebony strain has a defect in PR repair of endonuclease-sensitive sites induced in the DNA of primary cell cultures by UV irradiation; (3) the ebony strain has a defect in the repair of single-strand breaks induced in the DNA by X-rays (again in primary cell cultures), at least early on in the repair incubation. A rough localization of the UV sensitivity and the PR ability is presented and the possible relevance of the biochemical to the genetic results is discussed. 相似文献
The teratogenic and goitrogenic effects of Propineb, dithiocarbamate pesticide and Propylenthiourea (PLTU), its metabolite and degradation product have been studied. The aim of this study was to show the possible correlation between the two activities. Female Sprague-Dawley rats were treated with Propineb and PLTU starting from 6th to 16th day of pregnancy. The functional state of maternal and foetal thyroid, the toxicity of products versus dams and embryotoxic and teratogenic effects were examined. The observed goitrogenic effect may be compared to that reported in the previous studies of the authors, if considering time of sacrifice. In fact, the lesion quickly rises and as rapidly regresses when treatment is stopped. The foetal thyroid has not been affected by the product administered to the dams. PLTU showed a clear teratogenic activity at doses that did not show any maternal toxicity (45 and 90 mg/k). 相似文献
To commemorate the 20th Anniversary of the Society of Melanoma Research and the first International Melanoma Research Congress held in June of 2003, we have described in brief, how the Society for Melanoma Research (SMR) began, the purpose, goals, and governance of the SMR, and how the society has evolved to support new melanoma researchers. In celebration of the immense progress in treating melanoma patients over the last 20 years and the impact of the SMR on these advances, we have highlighted memories and insight from early SMR members and founders. 相似文献
The inaugural Diversity and Inclusion in Science Session was held during the 2021 Society for Melanoma Research (SMR) congress. The goal of the session was to discuss diversity, equity, and inclusion in the melanoma research community and strategies to promote the advancement of underrepresented melanoma researchers. An international survey was conducted to assess the diversity, equity, and inclusion (DEI) climate among researchers and clinicians within the Society for Melanoma Research (SMR). The findings suggest there are feelings and experiences of inequity, bias, and harassment within the melanoma community that correlate with one's gender, ethnic/racial group, and/or geographic location. Notably, significant reports of inequity in opportunity, discrimination, and sexual harassment demonstrate there is much work remaining to ensure all scientists in our community experience an academic workplace culture built on mutual respect, fair access, inclusion, and equitable opportunity. 相似文献