High Redshift Quasars and Star Formation in the Early Universe

In order to derive information on the star formation history in the early universe we observed 6 high-redshift (z=3.4) quasars in the near-infrared to measure the relative iron and \mgii emission strengths. A detailed comparison of the resulting spectra with those of low-redshift quasars show essentially the same FeII/MgII emission ratios and very similar continuum and line spectral properties, indicating a lack of evolution of the relative iron to magnesium abundance of the gas since z=3.4 in bright quasars. On the basis of current chemical evolution scenarios of galaxies, where magnesium is produced in massive stars ending in type II SNe, while iron is formed predominantly in SNe of type Ia with a delay of ~1 Gyr and assuming as cosmological parameters H_o = 72 km/s Mpc, Omega_M = 0.3, and Omega_Lambda = 0.7$, we conclude that major star formation activity in the host galaxies of our z=3.4 quasars must have started already at an epoch corresponding to z_f ~= 10, when the age of the universe was less than 0.5 Gyrs.Comment: 29 pages, 5 figures, ApJ in pres

Malignant glioma: Should chemotherapy be overthrown by experimental treatments?

Despite more than two decades of clinical research with chemotherapy, the outcome of malignant gliomas remains poor. Recent years have seen major advances in elucidation of the biology of these tumors, which in turn have led to the current development of innovative therapeutic strategies. The question confronting us at the end of the 1990s is whether we should continue to use and investigate chemotherapy or whether the time has come for experimental treatments. As a contribution to this debate, we reviewed the abundant literature on chemotherapy of malignant glioma, paying special attention to methodological features. The new treatment approaches based on current knowledge about glioma biology are then briefly summarized. Assessment of more than 20 years of chemotherapy trials is discouraging despite a few areas of modest success. Only patients with specific histology (oligodendroglioma, anaplastic astrocytoma) and good prognostic factors (young age, good performance status) may benefit from chemotherapy, with a possible reversal of neurological dysfunction. However, the real impact on survival is small (anaplastic astrocytoma) or undefined (oligodendroglioma). Furthermore, it is unfortunately obvious that the outcome of glioblastoma patients is not significantly modified by chemotherapy. We believe the time has come to explore the potential of novel biological therapies in glioblastoma patients. This could also be proposed for anaplastic astrocytoma and oligodendroglioma patients after failure of chemotherap

DURABILIDADE DE CONCRETOS PRODUZIDOS COM ADIÇÃO DE RESÍDUOS PROVENIENTES DE ROCHAS ORNAMENTAIS FRENTE À AÇÃO DE ÍONS CLORETO,

Os cloretos são considerados responsáveis por iniciar o processo de corrosão do aço pelo rompimento da sua camada passiva e aceleração das reações eletroquímicas de oxirredução. Para dificultar a penetração desses íons em estruturas de concreto localizadas próximas do mar deve-se investir na qualidade do concreto. O Resíduo do Beneficiamento de Rochas Ornamentais (RBRO) é produzido no Espírito Santo em larga escala e possui potencial para ser utilizado como adição mineral em matrizes cimentícias. Neste trabalho é avaliado o processo de corrosão das armaduras induzido pela ação de íons cloreto, sobre concretos produzidos com três níveis de relação água/cimento - 0,45; 0,55 e 0,65 e quatro níveis de adição de RBRO - 0%, 5%, 10% e 15%- em relação à massa de cimento. Foram avaliados os índices de consistência, massas específicas dos concretos no estado fresco; resistência à compressão axial, absorção de água por imersão e fervura e absorção capilar em 216 corpos de prova cilíndricos de concreto. 36 primas de concreto, com 72 corpos e prova de aço CA-50, foram submetidos a ciclos de indução e aceleração da corrosão. O ciclo compreendeu imersão parcial em solução com 5% de NaCl, por 48horas, e secagem em estufa ventilada, a 50ºC, por 5 dias. O potencial de corrosão das armaduras foi medido após imersão e após secagem dos corpos de prova, até a despassivação das armaduras. Por último, foi feito o ensaio colorimétrico por aspersão de do indicador AgNO3 a 0,1 mol/L para exame da altura de penetração dos íons Cl-. Utilizou-se o software Statgraphics® para a análise de regressão linear múltipla e Anova das variáveis dependentes estudadas. A utilização RBRO diminuiu a trabalhabilidade dos concretos e a sua massa específica no estado fresco, atendeu aos requisitos de resistência à compressão axial. Não se mostrou clara a contribuição da adição nos resultados de potencial de corrosão, entretanto, o tempo de indução da corrosão aumentou com o aumento do percentual de adição. O teor de 5% de RBRO mostrou ser o mais vantajoso do ponto de vista da durabilidade mostrando a menor contaminação de CL- no ensaio colorimétrico

Weak lensing observations of potentially X-ray underluminous galaxy clusters

Optically selected clusters of galaxies display a relation between their optical mass estimates and their X-ray luminosities Lx that has a large scatter. A substantial fraction of optically selected clusters have Lx estimates or upper limits significantly below the values expected from the Lx-mass relation established for X-ray selected clusters, i.e., these clusters are X-ray underluminous for their mass. We attempt to confirm or falsify the X-ray underluminous nature of two clusters, Abell 315 and Abell 1456, by using weak gravitational lensing as a third and independent measure of the clusters' masses. We obtained optical wide-field imaging data and selected background galaxies using their colors and measured the shear exerted by the tidal field of the foreground galaxy clusters. We then fitted parametrized models to our shear catalogs. After accounting for projections of large-scale structure and halo triaxiality, we find that A 315 is significantly X-ray underluminous for its mass, while no significant lensing signal was detected for A 1456. We re-evaluate earlier kinematic and X-ray analyses of these two clusters and discuss the nature of the X-ray underluminous cluster A 315 and why A 1456 was probably erroneously identified as being X-ray underluminous.Comment: Accepted for publication in A&A, included comments from language editor, added two reference

High-harmonic generation: taking control of polarization

The ability to control the polarization of short-wavelength radiation generated by high-harmonic generation is useful not only for applications but also for testing conservation laws in physics

Towards common file formats and data standards for seafloor geodesy - Community Whitepaper for UNAVCO’s “Future Directions for Seafloor Geodesy” Committee, September 2020 (revision of July 13, 2021)

Seafloor geodesy experiments have been expanding considerably in recent years. More and more research teamsaround the globe are conducting projects to monitor the tectonic or volcanic deformation of the seafloor. Theseexperiments are commonly based on limited-duration experiments, but increasingly, permanent observatories arealso being installed. This dynamic development is very encouraging for the establishment of a strong community which arguably willlead to the emergence of a worldwide scientific and technical synergy. However, data andknowledge transferbetween the different groups working on similar topics are still limited at the present time. This can be partlyexplained by the fact that the instruments, infrastructure, and processing software developed are custom-made andthus various file formats are used, although the fundamental observables are most of the time identical. One wayto overcome this limitation is to set up exchange standards in the form of standardized file formats. These fileswould gather and store all the physical quantities observed and will prove useful for the processing simplificationand, in the end, the extraction of the geodetic signal sought. Furthermore, uniformized formats would allow muchmore easily the comparison of software and processing methods between research groups, whether during tests oroperational measurement campaigns. Standardized data will eventually provide a base for the activities of potentialfuture national or international observation services. They would also make it possible to envisage the datadissemination similar to geodetic data recorded on land

Stability of bubble nuclei through Shell-Effects

We investigate the shell structure of bubble nuclei in simple phenomenological shell models and study their binding energy as a function of the radii and of the number of neutron and protons using Strutinsky's method. Shell effects come about, on the one hand, by the high degeneracy of levels with large angular momentum and, on the other, by the big energy gaps between states with a different number of radial nodes. Shell energies down to -40 MeV are shown to occur for certain magic nuclei. Estimates demonstrate that the calculated shell effects for certain magic numbers of constituents are probably large enough to produce stability against fission, alpha-, and beta-decay. No bubble solutions are found for mass number A < 450.Comment: 9 pages and 9 figures in the eps format include

Geometry dominated fluid adsorption on sculptured substrates

Experimental methods allow the shape and chemical composition of solid surfaces to be controlled at a mesoscopic level. Exposing such structured substrates to a gas close to coexistence with its liquid can produce quite distinct adsorption characteristics compared to that occuring for planar systems, which may well play an important role in developing technologies such as super-repellent surfaces or micro-fluidics. Recent studies have concentrated on adsorption of liquids at rough and heterogeneous substrates and the characterisation of nanoscopic liquid films. However, the fundamental effect of geometry has hardly been addressed. Here we show that varying the shape of the substrate can exert a profound influence on the adsorption isotherms allowing us to smoothly connect wetting and capillary condensation through a number of novel and distinct examples of fluid interfacial phenomena. This opens the possibility of tailoring the adsorption properties of solid substrates by sculpturing their surface shape.Comment: 6 pages, 4 figure

Depletion forces near curved surfaces

Based on density functional theory the influence of curvature on the depletion potential of a single big hard sphere immersed in a fluid of small hard spheres with packing fraction \eta_s either inside or outside of a hard spherical cavity of radius R_c is calculated. The relevant features of this potential are analyzed as function of \eta_s and R_c. There is a very slow convergence towards the flat wall limit R_c \to \infty. Our results allow us to discuss the strength of depletion forces acting near membranes both in normal and lateral directions and to make contact with recent experimental results