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When people seek to understand concepts from an incomplete set of examples and counterexamples, there is usually an exponentially large number of classification rules that can correctly classify the observed data, depending on which features of the examples are used to construct these rules. A mechanistic approximation of human concept-learning should help to explain how humans prefer some rules over others when there are many that can be used to correctly classify the observed data. Here, we exploit the tools of propositional logic to develop an experimental framework that controls the minimal rules that are simultaneously consistent with the presented examples. For example, our framework allows us to present participants with concepts consistent with a disjunction and also with a conjunction, depending on which features are used to build the rule. Similarly, it allows us to present concepts that are simultaneously consistent with two or more rules of different complexity and using different features. Importantly, our framework fully controls which minimal rules compete to explain the examples and is able to recover the features used by the participant to build the classification rule, without relying on supplementary attention-tracking mechanisms (e.g. eye-tracking). We exploit our framework in an experiment with a sequence of such competitive trials, illustrating the emergence of various transfer effects that bias participants’ prior attention to specific sets of features during learning. Fil: Abriola, Sergio Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigación en Ciencias de la Computación. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Investigación en Ciencias de la Computación; Argentina Fil: Tano, Pablo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina Fil: Romano, Sergio Gaston. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigación en Ciencias de la Computación. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Investigación en Ciencias de la Computación; Argentina Fil: Figueira, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigación en Ciencias de la Computación. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Investigación en Ciencias de la Computación; Argentina

Probabilistic proposals of Language of Thoughts (LoTs) can explain learning across different domains as statistical inference over a compositionally structured hypothesis space. While frameworks may differ on how a LoT may be implemented computationally, they all share the property that they are built from a set of atomic symbols and rules by which these symbols can be combined. In this work we propose an extra validation step for the set of atomic productions defined by the experimenter. It starts by expanding the defined LoT grammar for the cognitive domain with a broader set of arbitrary productions and then uses Bayesian inference to prune the productions from the experimental data. The result allows the researcher to validate that the resulting grammar still matches the intuitive grammar chosen for the domain. We then test this method in the language of geometry, a specific LoT model for geometrical sequence learning. Finally, despite the fact of the geometrical LoT not being a universal (i.e. Turing-complete) language, we show an empirical relation between a sequence’s probability and its complexity consistent with the theoretical relationship for universal languages described by Levin’s Coding Theorem. Fil: Romano, Sergio Gaston. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigación en Ciencias de la Computación. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Investigación en Ciencias de la Computación; Argentina Fil: Salles, Alejo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Cálculo; Argentina Fil: Amalric, Marie. Université Paris Sud; Francia. Université Paris-Saclay; Francia. Institut National de la Santé et de la Recherche Médicale; Francia Fil: Dehaene, Stanislas. Université Paris-Saclay; Francia. Institut National de la Santé et de la Recherche Médicale; Francia. Université Paris Sud; Francia Fil: Sigman, Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Torcuato Di Tella; Argentina Fil: Figueira, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigación en Ciencias de la Computación. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Investigación en Ciencias de la Computación; Argentina

A 51-year-old native of Rio de Janeiro presented with bilateral synchronous Paget's sarcomas in the tibiae, which developed in the upper right tibia and in the distal third of the left tibia. There were no other areas of Paget's disease. The largest tumor spread to the right inguinal nodes and also soft tissue. The tumor in the left tibia spread dramatically in the soft tissues up the leg and only involved the medullary cavity in its inferior portion. The patient died, but there was no autopsy. Comments are made about the prevalence of Paget's disease in Rio de Janeiro.

A bulky tumor of the first lumbar vertebra is described. The case is the 21st to be reported. The tumor resembled an aneurysmal bone cyst radiologically. It was resected without incident. The previously reported cases are reviewed and the literature discussed.

To evaluate the treatment of GIST in INCA.We conducted a retrospective analysis of all cases of GIST treated at INCA in the period from 1997 to 2009.We analyzed 146 patients with a mean age of 44.5 years and female predominance. The main symptom was abdominal pain. We observed the occurrence of a second primary tumor in 22% of cases and 92% of the immunohistochemistry exams were positive for CD117. The most frequent location was in the stomach and the high-risk group was predominant. Surgery was considered R0 (extensive) in 70% of the cases and the main sites of metastases were liver and peritoneum. Overall survival in two and five years was, respectively, 86% and 59%. There was a significant difference between overall survival (p = 0.29) of the high-risk group versus the other.Our patients presented mainly in the form of high-risk disease, with obvious impact on survival. The use of imatinib improved survival of patients with recurrent and metastatic disease. We should study its use in the setting of adjuvant and neoadjuvant therapy to improve results of the high risk group. The creation of reference centers is a need for the study of rare diseases.

This papers is a retrospective analysis of all cases of colorectal GIST treated at our institution. Considering the increased interest in this pathology, in 2008, we recently established a unit supported by Novartis in our department to research and treat GIST. Since then, there was a dramatic increase in the referral of this type of tumor to our center. Before initiating our research group, we had the permission of the ethics committee and the medical directors to study and publish the analysis of our cases. Now, we have a cohort of 98 patients treated during the last 10 years and from that, we selected all cases of Colorectal GIST's. They numbered 13 cases. We performed an analysis of these cases from the presentation to the results of treatment.

Completion lymph node dissection (CLND) is the standard procedure for patients with positive sentinel lymph nodes (SLN). With extensive pathological workup, increased numbers of small metastatic deposits are detected in SLN. This study evaluated the prognostic significance of SLN metastatic depositsor = 0.2 mm in patients treated in a referral cancer center in Brazil.Patients with stage I/II melanoma, consecutively submitted to a SLN procedure by the same surgeon from 2000 to 2006, were evaluated. All positive SLN and randomly selected negative cases were reviewed by two pathologists. Different prognostic factors and SLN tumor burden were recorded. Additional positive non-SLN after CLND, and disease outcome were evaluated.Of 381 patients who underwent SLN biopsy, 103 (27%) were positive. The mean/median Breslow tumor thickness in the overall group was 3.4/2.0 mm and in the SLN positive patients was 5.72/4.0 mm. Among these patients, 48 (47%) had metastatic deposits2 mm (macrometastasis), 49 (47%) had metastatic depositsor =2 mm but0.2 mm (micrometastasis), and 6 (6%) had metastatic depositsor =0.2 mm (submicrometastasis). Additional positive non-SLN were detected in 29% of patients with macrometastasis, in 25% of patients with micrometastasis, and in 0% of patients with submicrometastases. At median follow-up of 35 months, the estimated 3-year overall survival was 92% for negative SLN, 64% for micrometastases, 53% for macrometastases, and 100% for submicrometastases (P0.001).In the present study, patients with SLN metastatic depositsor =0.2 mm had no additional positive non-SLNs, and no recurrences or deaths were recorded, suggesting that their prognosis is equivalent to that of patients with negative SLN.

ORIGINAL ARTICLE Juliane Garcez MusacchioMaria da Gloria da Costa CarvalhoJose Carlos Oliveira de MoraisNathalie Henriques SilvaAdriana ScheligaSergio RomanoNelson Spector Detection of free circulating Epstein-Barr virus DNA in plasma of patients with Hodgkin’s disease Hematology Service, Universidade Federal do Rio de Janeiro and Oncology Service, Instituto Nacional do Câncer, Rio de Janeiro, Brazil CONTEXT AND OBJECTIVE: Free circulating Ep-stein-Barr virus (EBV) DNA is often present in the plasma of Hodgkin’s disease patients. The aim here was to evaluate the prevalence of this fi nd-ing, its correlation with the immunohistochemical expression of LMP-1 (latent membrane protein 1) and the infl uence of other clinical factors.DESIGN AND SETTING: Prospective study in two public tertiary institutions: Hematology Service, Universidade Federal do Rio de Janeiro, and Oncology Service, Instituto Nacional do Câncer, Rio de Janeiro.METHODS: A cohort of 30 patients with newly diagnosed Hodgkin’s disease was studied. The control group consisted of 13 healthy adult volun-teers. EBV DNA was determined by conventional polymerase chain reaction (PCR).RESULTS: The median age was 28 years, and 16 patients were women. Advanced disease was present in 19 patients, and six were HIV-positive. EBV DNA was present in the plasma of 13 patients and one control (43% versus 8%, p = 0.03). EBV DNA prevalence was higher in HIV-posi-tive patients (100% versus 29%, p = 0.0007) and those with advanced disease (63% versus 9%, p = 0.006). Among HIV-negative patients alone, EBV DNA prevalence remained higher in those with advanced disease. EBV DNA was found in 10/11 patients with LMP-1 expression in the lymph nodes, and in 3/19 without LMP-1 expression (kappa coeffi cient = 0.72).CONCLUSION