Cosmological quintessence accretion onto primordial black holes : conditions for their growth to the supermassive scale

In this work we revisit the growth of small primordial black holes (PBHs) immersed in a quintessential field and/or radiation to the supermassive black hole (SMBHs) scale. We show the difficulties of scenarios in which such huge growth is possible. For that purpose we evaluated analytical solutions of the differential equations (describing mass evolution) and point out the strong fine tuning for that conclusions. The timescale for growth in a model with a constant quintessence flux is calculated and we show that it is much bigger than the Hubble time.The fractional gain of the mass is further evaluated in other forms, including quintessence and/or radiation. We calculate the cosmological density $\Omega$ due to quintessence necessary to grow BHs to the supermassive range and show it to be much bigger than one. We also describe the set of complete equations analyzing the evolution of the BH+quintessence universe, showing some interesting effects such the quenching of the BH mass growth due to the evolution of the background energy. Additional constraints obtained by using the Holographic Bound are also described. The general equilibrium conditions for evaporating/accreting black holes evolving in a quintessence/radiation universe are discussed in the Appendix.Comment: 21 pp., 2 Figures, To appear in IJMP

Multi-bit sigma-delta modulators with enhanced dynamic-range using non-linear DAC for hearing aids

15th IEEE International Conference on Electronics, Circuits and Systems, MaltaThis paper presents the possibility of employing nonlinear low-resolution DACs in the feedback paths of multi-bit second-order Sigma-Delta modulators. The proposed technique is particularly attractive in applications such as hearing aids, requiring a very large dynamic range and medium signal-tonoise-plus-distortion-ratio. As demonstrated through simulated results in which noise and mismatch effects are included, for the same over-sampling ratio, improvements in the order of 6-to-9 dB in the dynamic range can be achieved when comparing with the same topology employing linear-DACs

A common deep source for upper-mantle upwellings below the Ibero-western Maghreb region from teleseismic P-wave travel-time tomography

Upper-mantle upwellings are often invoked as the cause of Cenozoic volcanism in the Ibero-western Maghreb region. However, their nature, geometry and origin are unclear. This study takes advantage of dense seismic networks, which cover an area extending from the Pyrenees in the north to the Canaries in the south, to provide a new high-resolution P-wave velocity model of the upper-mantle and topmost lower-mantle structure. Our images show three subvertical upper-mantle upwellings below the Canaries, the Atlas Ranges and the Gibraltar Arc, which appear to be rooted beneath the upper-mantle transition zone (MTZ). Two other mantle upwellings beneath the eastern Rif and eastern Betics surround the Gibraltar subduction zone. We propose a new geodynamic model in which narrow upper-mantle upwellings below the Canaries, the Atlas Ranges and the Gibraltar Arc rise from a laterally-propagating layer of material below the MTZ, which in turn is fed by a common deep source below the Canaries. In the Gibraltar region, the deeply rooted upwelling interacts with the Gibraltar slab. Quasi-toroidal flow driven by slab rollback induces the hot mantle material to flow around the slab, creating the two low-velocity anomalies below the eastern Betics and eastern Rif. Our results suggest that the Central Atlantic plume is a likely source of hot mantle material for upper-mantle upwellings in the Ibero-western Maghreb region

Digestibilidade de gerações de perfilhos do capim Tanzânia.

O objetivo do presente experimento foi determinar o efeito da intensidade e do ciclo de pastejo sobre a digestibilidade in vitro da matéria orgânica de gerações de perfilhos de capim Tanzânia. O delineamento experimental foi de blocos completos ao acaso com três tratamentos (intensidade de pastejo alta, média e baixa) e quatro repetições. As gerações de perfilhos eram identificadas com fios de arame coloridos. Um dia antes de cada pastejo duas amostras eram cortadas por parcela e a digestibilidade in vitro da matéria orgânica de cada geração determinada. A digestibilidade das gerações de perfilhos foi maior nas áreas submetidas a elevada intensidade de pastejo e decresceu com o avanço da idade (redução de 3 a 6 pontos percentuais de digestibilidade por ciclo) .Os efeitos negativos do florescimento sobre o valor nutritivo da forragem podem ser reduzidos através de práticas de manejo que promovam uma maior renovação de perfilhos

Microalgae-based unsaponifiable matter as source of natural antioxidants and metal chelators to enhance the value of wet Tetraselmis chuii biomass

The present work aimed to determine the antioxidant, metal chelating and neuroprotective potential of the unsaponifiable matter (UM) of Tetraselmis chuii to be applied to a biorefinery setting. The UM obtained via saponification from crude lipids extracted from microalgal wet biomass showed a radical scavenging activity (RSA) towards the DPPH radical of 90.7 +/- 1.3% and 57.1 +/- 1.2% at a concentration of 10 and 5 mg/ mL, respectively. The UM fraction also displayed metal chelating capacity at a concentration of 5 mg/ mL: 58.5 +/- 1.4% and 50.9 +/- 4.0% for copper and iron, respectively. The chemical characterization of the UM revealed significant levels of total phenolics (TPC, 13.61 mg GAE/g) and carotenoids (2.45 mg/g of beta-carotene, lutein and violaxanthin). Overall, the separation of the UM containing high value metabolites might significantly upgrade the total wet biomass value in a biorefinery, allowing the exploitation of a stream with relevant antioxidant and metal chelating activities.SFRH/BD/105541/2014, IF/00049/2012, CCMAR/Multi/04326/2013info:eu-repo/semantics/publishedVersio

Custo de produção de mudas clonais de Café Arábica produzidas por embriogênese somática

A produção de mudas clonais de café pode ser feita de diferentes formas. Entretanto, a produção por embriogênese somática é a que tem despontado como a mais promissora. A embriogênese somática permite a produção de mudas em larga escala a partir de folhas usadas como explantes. Plantas obtidas por esse processo apresentam comportamento semelhante ao de plantas oriundas de sementes, não havendo limitação para a sua utilização comercial. A produção de mudas clonais de café é realizada em laboratórios de cultura de tecidos adaptados para a produção em escala industrial, denominados de biofábricas. Todavia, a produção de mudas clonais via embriogênese somática é uma técnica que ainda não foi explorada comercialmente no Brasil e não existe uma estimativa do custo de produção de mudas clonais de café arábica. Assim, o objetivo no presente trabalho foi calcular o custo de produção de mudas clonais de café em uma biofábrica de pequeno porte, tendo-se como base o protocolo desenvolvido pela Fundação Procafé/Embrapa Café, com a colaboração de pesquisadores da Embrapa Recursos Genéticos e Biotecnologia e do Centro de Cooperação Internacional em Pesquisa Agronômica para o Desenvolvimento, CIRAD, França. Este trabalho apresenta também uma relação dos equipamentos e materiais necessários para a produção de mudas de café in vitro. O custo de produção de uma muda foi de R$0,97 para uma produção anual de 400.000 mudas, utilizando-se o plantio de embriões pré-germinados diretamente em tubetes. Caso a etapa de produção de plântulas em potes in vitro seja utilizada, o custo de produção passa a ser de R$1,34

Tuning the Biological Activity of Camphorimine Complexes through Metal Selection

This research was funded by FCT—Fundação para a Ciência e a Tecnologia, through projects CQE (UIDB/00100/2020 and UIDP/00100/2020) and C2TN (UID/MULTI/04349/2019), the projects of the Research Unit Institute for Bioengineering and Biosciences—iBB (UIDB/04565/2020 and UIDP/04565/2020), the project LA/P/0140/2020 of the Associate Laboratory Institute for Health and Bioeconomy—i4HB, and a PhD grant to J.P.C. (UI/BD/152244/2021).The cytotoxic activity of four sets of camphorimine complexes based on the Cu(I), Cu(II), Ag(I), and Au(I) metal sites were assessed against the cisplatin-sensitive A2780 and OVCAR3 ovarian cancer cells. The results showed that the gold complexes were ca. one order of magnitude more active than the silver complexes, which in turn were ca. one order of magnitude more active than the copper complexes. An important finding was that the cytotoxic activity of the Ag(I) and Au(I) camphorimine complexes was higher than that of cisplatin. Another relevant aspect was that the camphorimine complexes did not interact significantly with DNA, in contrast with cisplatin. The cytotoxic activity of the camphorimine complexes displayed a direct relationship with the cellular uptake by OVCAR3 cells, as ascertained by PIXE (particle-induced X-ray emission). The levels of ROS (reactive oxygen species) formation exhibited an inverse relationship with the reduction potentials for the complexes with the same metal, as assessed by cyclic voltammetry. In order to gain insight into the toxicity of the complexes, their cytotoxicity toward nontumoral cells (HDF and V79 fibroblasts) was evaluated. The in vivo cytotoxicity of complex 5 using the nematode Caenorhabditis elegans was also assessed. The silver camphorimine complexes displayed the highest selectivity coefficients (activity vs. toxicity).publishersversionpublishe