Mathematical retroreflectors

Retroreflectors are optical devices that reverse the direction of incident beams of light. Here we present a collection of billiard type retroreflectors consisting of four objects; three of them are asymptotically perfect retroreflectors, and the fourth one is a retroreflector which is very close to perfect. Three objects of the collection have recently been discovered and published or submitted for publication. The fourth object - notched angle - is a new one; a proof of its retroreflectivity is given.Comment: 32 pages, 19 figure

Educação e mediação intercultural: Experiências e práticas de formação e investigação

Com base na comunicação que este grupo de investigadoras realizou nas primeiras Jornadas da Rede de Ensino Superior para a Mediação Intercultural “Entre Iguais e Diferentes a Mediação Intercultural”, apresentamos, sucinta-mente, alguns projetos de investigação, formação e intervenção educativa, em que temos estado envolvidas nas nossas instituições, e nos quais a mediação constituiu uma componente relevante. Adotamos aqui um conceito abrangente de mediação, considerando dispositivos, contextos, protagonistas e interações que concorrem para o desenvolvimento de processos de comunicação e de aproximação entre pessoas, grupos e/ou comunidades, no sentido da transformação pessoal e social, da emancipação e da coesão social. É por isso que nalguns casos os projetos foram (ou são) mais focados na mediação de conflitos, noutros na mediação cultural e noutros ainda na mediação intercultural e comunitária. Também os campos de ação e investigação em que estes projetos tiveram lugar podem considerar-se diversos. Alguns deles têm o seu foco no campo da formação, por vezes em articulação com a investigação, e outros no campo da ação socioeducativa, integrando processos de investigação, designadamente de investigação-ação e de etnografia crítica. Pensamos ser esta uma oportunidade para promover a divulgação destes projetos, favorecer o reconhecimento das nossas áreas de interesse e encontrar possíveis sinergias para o desenvolvimento de projetos comuns.info:eu-repo/semantics/publishedVersio

Layer-by-layer deposition of antimicrobial polymers on cellulosic fibers : a new strategy to develop bioactive textiles

In recent years, there has been an increase of infectious diseases caused by different microorganisms and the development of antibiotic resistance. In this way, the search for new and efficient antibacterial materials is imperative. The main polysaccharides currently used in the biomedical and pharmaceutical domains are chitin and its derivative chitosan (CH) and alginates (ALG). In this study, a simple technique of Layer by Layer (LbL) of applying polycation CH and polyanion ALG was used to prepare CH/ALG multilayers on cotton samples via the electrostatic assembly with success. The CH/ALG cotton samples (functionalized) were investigated for their antibacterial properties towards Staphylococcus aureus and Klebsiella pneumonia using the international standard method JIS L 1902:2002. The antibacterial activity of the functionalized samples was tested in terms of bacteriostatic and bactericidal activity, and results showed that the samples exhibited a bacteriostatic effect on the two bacteria tested, as expected. In addition, samples with five layers (CH/ALG/CH/ALG/CH) were more effective in inhibiting bacterial growth. This new coating for cellulosic fibers is a new strategy and may open new avenues for the development of antimicrobial polymers with potential application in health-care field.The authors would like to thank Fundacao para a Ciencia e Tecnologia (FCT) for the funding granted concerning the project - PTDC/EBB-BIO/113671/2009 (FCOMP-01-0124-FEDER-014752) Skin2Tex. Also, we would like to thank Fundo Europeu de Desenvolvimento Regional (FEDER) through COMPETE - Programa Operacional Factores de Competitividade (POFC) for the co-funding

On the two-dimensional rotational body of maximal Newtonian resistance

We investigate, by means of computer simulations, shapes of nonconvex bodies that maximize resistance to their motion through a rarefied medium, considering that bodies are moving forward and at the same time slowly rotating. A two-dimensional geometric shape that confers to the body a resistance very close to the theoretical supremum value is obtained, improving previous results.Comment: This is a preprint version of the paper published in J. Math. Sci. (N. Y.), Vol. 161, no. 6, 2009, 811--819. DOI:10.1007/s10958-009-9602-

Do you know this syndrome? Dyspigmentation along the Blaschko lines caused by trisomy 7 mosaicism

Dyspigmentation along the Blaschko lines is strongly suggestive of a mosaic skin disorder. We report a 9-year-old male patient who presented with swirls and streaks of both hypo and hyperpigmentation involving the entire body. Additionally, he had hypertrichosis, musculoskeletal and minor neurodevelopment abnormalities but no intellectual disability. Cultured fibroblast displayed trisomy 7 mosaicism, which can explain this pigmentary phenotype. Widespread dyspigmentation associated with involvement of other organs should prompt systemic examination to detect additional anomalies and genetic evaluation should be considered, even with normal fetal karyotype.info:eu-repo/semantics/publishedVersio

Geochemical fingerprinting of Roman pottery production from Manta Rota kilns (Southern Portugal)

The Roman site of Manta Rota, located in Algarve region, Portugal, is known from the XIXth century when Estacio da Veiga recovered a few pottery fragments and identified the foundations of Roman structures. References in early XXth century refer to a pottery kiln and to the remains of both amphorae and lamps. In 1992, emergency excavations directed by Cristina Garcia excavated a structure identified as a kiln and recovered abundant amphorae fragments of a locally produced Dressel 14 type. There is evidence of production of tiles, common ware and amphora. The study of the remains collected (terra sigillata and amphorae) in the excavations shows that Roman occupation of the site covers a period from the middle of the 1st century until the 5th century AD. The major production of the kiln area was the Dressel 14 fish sauce amphora centered in the middle/second half of the 1st century but the production of Almagro 51c is also attested. A preliminary macroscopic analysis of both the amphorae and the common ware show identical features. The aim of this paper is to present chemical characterization of the production of Manta Rota and to compare the results with different workshops in the Algarve region as Quinta do Lago, near Faro or S. Bartolomeu de Castro Marim, in the proximity of the studied area, in order to establish geochemical fingerprints of Manta Rota ceramic production center. Preliminary results point to a fine geochemical differentiation of the Manta Rota ceramics in comparison with the other two roman production centers of Algarve region

Multidrug-Resistant Klebsiella Pneumoniae Meningitis Successfully Treated with Intrathecal Colistin

Background: Multidrug-resistant (MDR) gram negative bacteria meningitis has become a clinical entity with increasing importance in recent years. Intrathecal colistin (ITH) has been used in the treatment of this cases. Aims: To report one case of MDR Klebsiella pneumoniae meningitis and ventriculitis successfully treated with ITH colistin. Case Report: Nine months old boy, born at 28 weeks of gestational age, diagnosed with neonatal meningitis, complicated with tetraventricular hydrocephalus requiring ventriculo-peritoneal shunt (VPS) placement and multiple shunt revisions. Admitted for worsening hydrocephalus. Cerebrospinal fluid (CSF) cultures were positive for extended-spectrum β-lactamase (ESBL) Klebsiella pneumoniae, only sensitive to meropenem and amikacin. Intravenous meropenen was started but CSF cultures remained positive and shunt device could not be removed. Although susceptibility to colistin was not available, on day 24 intrathecal colistin(4mg/day) was started through an external shunt. CSF white blood cell count improved and cultures became negative. Colistin was stopped after 19 days because of CSF pleocitosis and meropenen maintained for a total of 2 months with clinical improvement. Conclusion: In Klebsiella pneumoniae meningitis with ventriculitis, ITH colistin can be considered a safe, effective, and practicable alternative treatment when parental administration fails.info:eu-repo/semantics/publishedVersio

Asymmetric core combustion in neutron stars and a potential mechanism for gamma ray bursts

We study the transition of nuclear matter to strange quark matter (SQM) inside neutron stars (NSs). It is shown that the influence of the magnetic field expected to be present in NS interiors has a dramatic effect on the propagation of a laminar deflagration (widely studied so far), generating a strong acceleration of the flame in the polar direction. This results in a strong asymmetry in the geometry of the just formed core of hot SQM which resembles a cylinder orientated in the direction of the magnetic poles of the NS. This geometrical asymmetry gives rise to a bipolar emission of the thermal neutrino-antineutrino pairs produced in the process of SQM formation. The neutrino-antineutrino pairs annihilate into electron-positron pairs just above the polar caps of the NS giving rise to a relativistic fireball, thus providing a suitable form of energy transport and conversion to gamma emission that may be associated to short gamma ray bursts (GRBs).Comment: 2 figure