Utilization of potentially alkali-silica reactive aggregates requires reliable performance tests to evaluate the alkali-silica reactivity of various aggregate combinations, including their alkali threshold dependence on binder type. Several such performance tests have been used worldwide for more than 15 years, but none of the methods have proven to be reliable for use with all aggregate types and all binders. One of the objectives of RILEM TC 219-ACS (2007-2012) is to develop and validate one or more of such performance tests. Several parameters may influence the results obtained in an accelerated performance test compared to the field behavior. Based on a state of the art literature review, this paper discusses which parameters must be considered to be able to develop reliable ASR performance testing methods and provides some tentative recommendations. The internal humidity in the test specimens, the extent of alkali leaching and the storage temperature are of particular importance.

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Problem-Based Learning, a methodology that builds on problems to develop students' new knowledge, can also be useful in helping students to learn Nature of Science. Prospective science teachers' conceptions regarding Nature of Science and its teaching through Problem-Based Learning were analyzed by applying a semi-structured interview. Nine respondents recognized that this methodology promote research activities and contribute to the learning of some aspects of scientific inquiry. Moreover, they specifically considered that Problem-Based Learning may foster the understanding of the tentative nature of scientific knowledge and of the role of creativity implicit in scientific endeavor. Authors consider that more attention should be given to the contemporary Nature of Science views and to its consistent teaching through this methodology.

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Resumo: A xantomatose plana difusa normolipêmica (XPDN) é uma dermatose adquirida rara, muitas vezes associada a doenças sistêmicas, nomeadamente neoplasias hematológicas(sobretudo o mieloma múl-tiplo) ou a processos linfoproliferativos. A XPDN pode preceder o aparecimento dessas doenças em vários anos, sendo por isso recomendada uma vigilância clínica e laboratorial periódica, mesmo para os doentes que aparentemente não apresentam uma doença associada. Descrevemos um caso associado à gamopatia monoclonal. Este caso demonstra a importância das manifestações cutâneas como primeira manifestação de doenças hematológicas importantes e por isso os clínicos devem estar familiarizados com esta entidade. Palavras-chave: Mieloma múltiplo; Paraproteinemias; Xantomatose Abstract: Diffuse plane normolipemic xanthomatosis (DPNX) is a rare, non-inherited disease that is often associated with systemic diseases, mainly malignant hematological (especially multiple myeloma) or lymph proliferative disorders. The DPNX can precede the appearance of such conditions by several years, so careful follow-up and periodic laboratory examinations are recommended even for patients that seemed to have no underlying disease. We describe a case associated with monoclonal gammopathy. This case shows that dermatological lesions can be the first manifestation of important hematological diseases and so physicians should be familiarized with this entity.

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BACKGROUNDMastocytosis is a clonal disorder characterized by the accumulation of abnormal mast cells in the skin and/or in extracutaneous organs. OBJECTIVESTo present all cases of mastocytosis seen in the Porto Hospital Center and evaluate the performance of World Health Organization diagnostic criteria for systemic disease. METHODSThe cases of twenty-four adult patients with mastocytosis were reviewed. Their clinical and laboratorial characteristics were assessed, and the properties of the criteria used to diagnose systemic mastocytosis were evaluated. RESULTSThe age of disease onset ranged from 2 to 75 years. Twenty-three patients had cutaneous involvement and 75% were referred by dermatologists. Urticaria pigmentosa was the most common manifestation of the disease. One patient with severe systemic mast cell mediator-related symptoms showed the activating V560G KIT mutation. The bone marrow was examined in 79% of patients, and mast cell immunophenotyping was performed in 67% of the participants. Systemic disease was detected in 84% of cases, and 81% of the sample had elevated serum tryptase levels. All the diagnostic criteria for systemic mastocytosis had high specificity and positive predictive value. Bone marrow biopsy had the lowest sensitivity, negative predictive value and efficiency, while the highest such values were observed for mast cell immunophenotyping. Patients were treated with regimens including antihistamines, sodium cromoglycate, alpha-interferon, hydroxyurea and phototherapy. CONCLUSIONSCutaneous involvement is often seen in adult mastocytosis patients, with most individuals presenting with indolent systemic disease. Although serum tryptase levels are a good indicator of mast cell burden, bone marrow biopsy should also be performed in patients with normal serum tryptase, with flow cytometry being the most adequate method to diagnose systemic disease.

The alkali–aggregate reaction comprises the alkali–silica reaction (ASR) and the alkali–carbonate reaction (ACR). Reaction kinetics of the ASR depends on the grain size and crystalline structure of the reactive silicon dioxide. The reaction starts in the aggregates along the particle periphery and progresses inward. After cracking of the particle, larger amounts of reaction products are formed and are eventually extruded in the cement paste, where they fill cracks and voids. ASR products within aggregates predominantly consist of (hydrated) silicon, alkalis and calcium with characteristic atomic ratios of (Na + K)/Si ∼ 0·25 and Ca/Si ∼ 0·25. They take up additional calcium while releasing alkalis when extruded. Amorphous and crystalline reaction products occur and coexist. Expansion is the result of water adsorption by the reaction products. In ACR, harmless dedolomitisation is distinguished from deleterious reaction of fine-grained silica disseminated throughout the carbonate matrix. Further research is needed to gain more in-depth knowledge about the thermodynamics and kinetics of ASR products and the mechanisms of expansion. This should allow the establishment of a better link between concrete structures and both accelerated testing and models.