ESO452-SC11: The lowest mass globular cluster with a potential chemical inhomogeneity

We present the largest spectroscopic investigation of one of the faintest and least studied stellar clusters of the Milky Way, ESO452-SC11. Using the Anglo-Australian Telescope AAOmega and Keck HIRES spectrographs we have identified 11 members of the cluster and found indications of star-to-star light element abundance variation, primarily using the blue cyanogen (CN) absorption features. From a stellar density profile, we estimate a total cluster mass of $(6.8\pm3.4)\times10^3$ solar masses. This would make ESO452-SC11 the lowest mass cluster with evidence for multiple populations. These data were also used to measure the radial velocity of the cluster ($16.7\pm0.3$ km s$^{-1}$) and confirm that ESO452-SC11 is relatively metal-rich for a globular cluster ([Fe/H]$=-0.81\pm0.13$). All known massive clusters studied in detail show multiple populations of stars each with a different chemical composition, but many low-mass globular clusters appear to be chemically homogeneous. ESO452-SC11 sets a lower mass limit for the multiple stellar population phenomenon.Comment: 13 pages, 11 figures. Accepted for publication in MNRA

Spin relaxation and anticrossing in quantum dots: Rashba versus Dresselhaus spin-orbit coupling

The spin-orbit splitting of the electron levels in a two-dimensional quantum dot in a perpendicular magnetic field is studied. It is shown that at the point of an accidental degeneracy of the two lowest levels above the ground state the Rashba spin-orbit coupling leads to a level anticrossing and to mixing of spin-up and spin-down states, whereas there is no mixing of these levels due to the Dresselhaus term. We calculate the relaxation and decoherence times of the three lowest levels due to phonons. We find that the spin relaxation rate as a function of a magnetic field exhibits a cusp-like structure for Rashba but not for Dresselhaus spin-orbit interaction.Comment: 6 pages, 1 figur

MoS2 and MoS2 Nanocomposites for Adsorption and Photodegradation of Water Pollutants: A Review

The need for fresh and conveniently treated water has become a major concern in recent years. Molybdenum disulfide (MoS2) nanomaterials are attracting attention in various fields, such as energy, hydrogen production, and water decontamination. This review provides an overview of the recent developments in MoS2-based nanomaterials for water treatment via adsorption and photodegradation. Primary attention is given to the structure, properties, and major methods for the synthesis and modification of MoS2, aiming for efficient water-contaminant removal. The combination of MoS2 with other components results in nanocomposites that can be separated easily or that present enhanced adsorptive and photocatalytic properties. The performance of these materials in the adsorption of heavy metal ions and organic contaminants, such as dyes and drugs, is reviewed. The review also summarizes current progress in the photocatalytic degradation of various water pollutants, using MoS2-based nanomaterials under UV-VIS light irradiation. MoS2-based materials showed good activity after several reuse cycles and in real water scenarios. Regarding the ecotoxicity of the MoS2, the number of studies is still limited, and more work is needed to effectively evaluate the risks of using this nanomaterial in water treatment.publishe

Descolagem de um revestimento cerâmico em fachada

A capacidade de um revestimento cerâmico resistir à descolagem depende da correcta selecção do produto de colagem e do método de colagem. Estes devem ser adequados à intensidade das acções previstas, ao tipo de utilização do revestimento, às características do suporte e ao tipo de revestimento. Uma cuidada concepção do revestimento e a selecção do produto de colagem adequado para cada situação não garante por si só a eficiência da colagem sendo necessário que essas precauções sejam acompanhadas de uma correcta execução. Nesta comunicação apresenta-se um trabalho onde se procedeu à análise das causas da des-colagem de um revestimento cerâmico de uma fachada. Procede-se à caracterização da situação existente e à descrição dos ensaios realizados. Propõem-se soluções de reabilitação e elaboram-se recomendações de aplicação

Estudo de um edifício de habitação multifamiliar com anomalias não estruturais

Os erros de construção grosseiros, a reduzida qualidade de execução, o deficiente acompanhamento/fiscalização dos trabalhos em obra, o completo desrespeito da legislação em vigor desde a fase de projecto não são invulgares. Estas situações provocam elevados prejuízos materiais, reduzem a qualidade de vida das populações e chegam por vezes a constituir risco para a vida. Nesta comunicação, apresenta-se um trabalho onde se procedeu ao levantamento das patologias de um edifício de habitação com alguns dos vícios anteriormente referidos. Realizaram-se várias visitas ao local, procedeu-se ao registo das anomalias, analisou-se o projecto de licenciamento e recolheu-se o testemunho de moradores. Fez-se uma análise das causas das patologias encontradas e propõem-se medidas correctivas

Eficácia de barreiras acústicas

O tráfego rodoviário tem impactes significativos no ambiente, na saúde e na qualidade de vida das populações. Os avultados investimentos aplicados na construção de barreiras acústicas nem sempre se traduzem numa redução eficaz do ruído. Esta comunicação apresenta os resultados da avaliação da eficácia de três barreiras acústicas colocadas em vias de comunicação com volumes de tráfego distintos. Os materiais que as constituem são blocos de betão parcialmente preenchidos com lã de rocha, chapa metálica perfurada com lã de rocha e painéis pré-fabricados de betão com inertes leves. A avaliação da eficácia de cada barreira acústica foi efectuada com recurso a sonómetros colocados à frente, no tardoz e numa zona contígua não influenciada pela mesma. Para complementar a avaliação, estabelecem-se comparações entre os valores medidos e os valores obtidos a partir de modelos simplificados de comportamento.The road traffic has significant impacts in the environment, in population quality of life and health. The large investments applied in construction of acoustics barriers nor always result in an efficient noise reduction. This paper presents the results of the evaluation of the effectiveness of three acoustics barriers placed in highways with distinct traffic. The materials that constitute the barriers are concrete blocks partially filled with rockwool, perforated metallic shell with rockwool and prefabricated concrete panels. The evaluation of the effectiveness of each acoustics barrier was carried out with sound level meters placed in the front, behind and in a contiguous zone not influenced by the barrier. Comparisons between the measured values and the values gotten from simplified behaviour models are established

Drug Delivery Systems and Flavonoids: Current Knowledge in Melanoma Treatment and Future Perspectives

Melanoma is an aggressive form of skin cancer with a high prevalence in the population. An early diagnosis is crucial to cure this disease. Still, when this is not possible, combining potent pharmacological agents and effective drug delivery systems is essential to achieve optimal treatment and improve patients' quality of life. Nanotechnology application in biomedical sciences to encapsulate anticancer drugs, including flavonoids, in order to enhance therapeutic efficacy has attracted particular interest. Flavonoids have shown effectiveness against various types of cancers including in melanoma, but they show low aqueous solubility, low stability and very poor oral bioavailability. The utilization of novel drug delivery systems could increase flavonoid bioavailability, thereby potentiating its antitumor effects in melanoma. This review summarizes the potential of different flavonoids in melanoma treatment and the several nanosystems used to improve their biological activity, considering published information that reported improved biological and pharmacological properties of encapsulated flavonoids.publishe