Initial pseudo-steady state & asymptotic KPZ universality in semiconductor on polymer deposition

The Kardar-Parisi-Zhang (KPZ) class is a paradigmatic example of universality in nonequilibrium phenomena, but clear experimental evidences of asymptotic 2D-KPZ statistics are still very rare, and far less understanding stems from its short-time behavior. We tackle such issues by analyzing surface fluctuations of CdTe films deposited on polymeric substrates, based on a huge spatio-temporal surface sampling acquired through atomic force microscopy. A \textit{pseudo}-steady state (where average surface roughness and spatial correlations stay constant in time) is observed at initial times, persisting up to deposition of $\sim 10^{4}$ monolayers. This state results from a fine balance between roughening and smoothening, as supported by a phenomenological growth model. KPZ statistics arises at long times, thoroughly verified by universal exponents, spatial covariance and several distributions. Recent theoretical generalizations of the Family-Vicsek scaling and the emergence of log-normal distributions during interface growth are experimentally confirmed. These results confirm that high vacuum vapor deposition of CdTe constitutes a genuine 2D-KPZ system, and expand our knowledge about possible substrate-induced short-time behaviors.Comment: 13 pages, 8 figures, 2 table

The use of flocculating brewer's yeast for Cr(III) and Pb(II) removal from residual wastewaters

The use of inexpensive biosorbents to sequester heavy metals from aqueous solutions, is one of the most promising technologies being developed to remove these toxic contaminants from wastewaters. Considering this challenge, the viability of Cr(III) and Pb(II) removal from aqueous solutions using a flocculating brewer's yeast residual biomass from a Portuguese brewing industry was studied. The influence of physicochemical factors such as medium pH, biomass concentration and the presence of a co-ion was characterised. Metal uptake kinetics and equilibrium were also analysed, considering different incubation temperatures. For both metals, uptake increased with medium pH, being maximal at 5.0. Optimal biomass concentration for the biosorption process was determined to be 4.5 g dry weight/l. In chromium and lead mixture solutions, competition for yeast binding sites was observed between the two metals, this competition being pH dependent. Yeast biomass showed higher selectivity and uptake capacity to lead. Chromium uptake kinetic was characterised as having a rapid initial step, followed by a slower one. Langmuir model describes well chromium uptake equilibrium. Lead uptake kinetics suggested the presence of mechanisms other than biosorption, possibly including its precipitation.Instituto de Biotecnologia e Química Fina (IBQF) - Junta Nacional de Investigação Cientifica e Tecnologica (J.N.I.C.T), project PEAM/SEL/516/95

Trivalent chromium removal using flocculating yeasts : effect of pre-treatments on removal efficiency

Praxis XXI; Fundação para a Ciência e a Tecnologia (FCT)

Relationship between top executive compensation and corporate governance: evidence from large Italian listed companies

The modernization of corporate governance aims the alignment of the interests of managers with those of companies, promoting a new discipline of internal controls and risk analysis with an enforcement of shareholder rights of information. This research investigates the impact of corporate governance variables –ownership, board of directors and remuneration committee– on executive compensation. A balanced sample of 52 Italian listed companies has been adopted to test the hypotheses, covering 55.98% and 47.13% of market capitalization in 2011 and 2015 respectively and including 669 board members. Theoretical models evidence a certain stability of compensation schemes for Italian managers over time. Findings suggest that there is a statistically significant positive effect of familiar ownership on the amount of compensation. Along with nature of ownership, the number of directors in the remuneration committee appointed by minorities assume a determinant role. With statistical significance, it affects negatively the compensation level, but, contrarily to best practices, it affects negatively the adoption of forms of incentive compensation.info:eu-repo/semantics/acceptedVersio

Sorption of Cr(III) from aqueous solutions by spent brewery grain

Two types of spent brewery grains were tested for Cr(III) uptake from aqueous solutions: not treated spent grains (NTSG), obtained by abundant washing of spent grain obtained from a Portuguese brewing industry with distilled water, and treated spent grain (TSG), prepared by treating NTSG with NaOH 0.5 M for four hours followed by washing with distilled water. Both materials were mixed with chromium solutions (50 and 100 mg Cr(III)/L), varying medium pH from 3 to 5. Maximum metal uptake occurred at pH 5. Langmuir isotherm model well describes Cr(III) biosorption by NTSG and TSG. The maximum uptake capacity obtained was 17.84 mg Cr(III)/g NTSG and 13.87 mg Cr(III)/g TSG. Considering that Langmuir constant, b, reflecting the affinity between the sorbent and the sorbate is lower for NTSG (0.0749 L/mg) it is possible to conclude that the alkalis treatment does not improve spent grain uptake capacity for Cr(III).Fundação para a Ciência e a Tecnologia (FCT) - PRAXIS XXI/BD/15945/98

Cr(III) removal and recovery from Saccharomyces cerevisiae

Heavy metal recovery from biosorbents is of major importance in the assessment of competitiveness of biosorption processes. Several desorption agents (H2SO4, HNO3, HCl, CH3COOH and EDTA) were tested for the selection of the optimal elution conditions for Cr(III) recovery from Saccharomyces cerevisiae cells. Sorption time was optimised as it plays an important role in the sorption–desorption process, being shown that a 30 min sorption period is the best option to ensure metal removal from solution and good recovery from biosorbent. The optimal contact time with desorption agents was also studied, as long exposures to these ones may cause cell damage, affecting biosorbent metal uptake capacity in subsequent sorption cycles. Each eluant was analysed in terms of its desorption capacity and its effect on the biomass metal uptake capacity in multiple sorption–desorption cycles. Considering the effectiveness of chromium desorption from loaded biomass, it was possible to conclude that H2SO4 (pH≈1) was the most effective eluant tested, accomplishing the highest Cr(III) recovery from S. cerevisiae in three consecutive sorption/desorption cycles. Regarding the damage caused by acid treatment on S. cerevisiae cells, assessed by the reduction on metal uptake capacity after elution, it was possible to observe that sulphuric acid was the most harmful eluant causing long term negative effects in metal uptake. By the time the experiments were interrupted (nearly 26 h of continuous cycles) biomass uptake capacity was reduced to about 77% of the value reached before acid treatment.Fundação para a Ciência e a Tecnologia (FCT) – PRAXIS XXI/BD/15945/98

Field-theoretical renormalization group for a flat two-dimensional Fermi surface

We implement an explicit two-loop calculation of the coupling functions and the self-energy of interacting fermions with a two-dimensional flat Fermi surface in the framework of the field theoretical renormalization group (RG) approach. Throughout the calculation both the Fermi surface and the Fermi velocity are assumed to be fixed and unaffected by interactions. We show that in two dimensions, in a weak coupling regime, there is no significant change in the RG flow compared to the well-known one-loop results available in the literature. However, if we extrapolate the flow to a moderate coupling regime there are interesting new features associated with an anisotropic suppression of the quasiparticle weight Z along the Fermi surface, and the vanishing of the renormalized coupling functions for several choices of the external momenta.Comment: 16 pages and 22 figure

Cr (III) recovery from Saccharomyces cerevisiae by elution : a preliminary study

To recover adsorbed metals from biosorbents, in order to recycle metal and reuse biomass in several adsorption/desorption cycles, elution conditions need to be optimized. The present work aimed to study the following elution parameters: eluant type and concentration (H2SO4, HNO3, HCl, CH3COOH and Na2CO3 0.1, 0.5 and 1.0 M, and EDTA 0.01, 0.05 and 0.1 M); biosorbent contact time with Cr (III) solution (15 min, 2 and 24 h), and S/L ratio (4 and 8 g/L). Experimental data show a decrease in Cr recovery efficiency with increasing sorption time, probably due to metal bioaccumulation. Concerning the S/L ratio, it was possible to observe, in most essays, that best recoveries were achieved using biosorbent concentration of 8 g/L. Comparing the eluants tested according to their metal recovery efficiencies, it can be concluded that Na2CO3 is not a good eluant (maximum recovery of 21 %). All the others showed equivalent behaviours, being necessary more assays to determine eluant treatment effect in Cr uptake capacity in subsequent sorption cycles.Fundação para a Ciência e a Tecnologia (FCT

Convergence of simple adaptive Galerkin schemes based on h − h/2 error estimators

We discuss several adaptive mesh-refinement strategies based on (h − h/2)-error estimation. This class of adaptivemethods is particularly popular in practise since it is problem independent and requires virtually no implementational overhead. We prove that, under the saturation assumption, these adaptive algorithms are convergent. Our framework applies not only to finite element methods, but also yields a first convergence proof for adaptive boundary element schemes. For a finite element model problem, we extend the proposed adaptive scheme and prove convergence even if the saturation assumption fails to hold in general