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Aims: The objective of this work was to determine the degradation capacity of low-density polyethylene by the bacterium Bacillus subtilis and analyze the production of extracellular laccase activity. Methodology: The experiments was realized in 50 mL of culture medium, added with a fragment of known dry weight (1 cm2 colorless polyethylene bag squares), and were incubated at 28°C, pH 6.5, for 6 months under static conditions, determining the growth of the bacterium by dry weight (68, 75, and 91 mg), the production of extracellular protein (271, 234, and 326.1 mg/mL), and the degradation of the substrate by dry biodegraded (8.57%, 5.88%, and 11.76%). Results: The production of extracellular laccase enzyme was analyzed in presence of polyethylene, finding an enzymatic activity of laccase of 2.06, 1.49, and 2,03 U/mL, while in the control without substrate, no enzymatic activity was observed, which suggests that this enzyme may participate in the degradation of polyethylene. In addition, some characteristics of the extracellular enzymatic activities were analyzed, such as stability at 4oC and 28oC, optimal pH and temperature, the effect of protein and substrate concentration. Conclusion: The extracellular protein production and dry weight of the bacterium are higher in the presence of low-density polyethylene. The laccase activity is very stable at 4oC and 28oC, the most effective pH and temperature, were 4.5 and 28oC, and present an incubation time of 5 minutes, and this data suggest that this enzymatic activitiy may participate in the degradation of low density polyethylene.

Recently, the removal capacity of different heavy metals from sites contaminated by low-cost materials has been studied, with promising results. These adsorbents include dead microorganisms, clay minerals, agricultural waste, industrial waste, and other materials. The objective of this work was studying the removal capacity of Cr (VI) by a commercial mushroom, the macromycete Agaricus bisporus (white strain), by the Diphenylcarbazide colorimetric method It was found that the biomass removal 100 mg/L of the metal at 21 minutes, pH 1.0, 28oC, and 100 rpm. On the other hand, if the concentration of the metal is increased, the removal capacity for the analyzed biomass decreases at 28oC. 200 mg/L are removal at 60 minutes, while with 1 g/L of the metal, its removal 90.3%. If the concentration of the bioadsorbent is increased, the removal of the metal also increases, and the presence of other heavy metals does not influence in the removal of the metal, and this was desorbed 70.4%, with NaOH 0.5 N. Finally, it was observing that after 7 days of incubation, 76.2%, and 66.1%, of Cr (VI) present in naturally contaminated earth and water, were removal, respectively.

Industrial effluents from chromium-based products lead to chromium pollution in the environment. Several technologies have been employed for the removal of chromium (Cr) from the environment, including adsorption, ion-exchange, bioremediation, etc. In this study, we isolated a Cr (VI)-resistant fungus, Purpureocillium lilacinum, from contaminated soil, which could reduce chromium. We also characterized a reductant activity of dichromate found in the cellular fraction of the fungus: optimal pH and temperature, effect of enzymatic inhibitors and enhancers, metal ions, use of electron donors, and initial Cr (VI) and protein concentration. This study also shows possible mechanisms that could be involved in the elimination of this metal. We observed an increase in the reduction of Cr (VI) activity in the presence of NADH followed by that of formate and acetate, as electron donor. This reduction was highly inhibited by EDTA followed by NaN3 and KCN, and this activity showed the highest activity at an optimal pH of 7.0 at 37 °C with a protein concentration of 3.62 µg/mL.

The objective of this work was to study the resistance and removal capacity of heavy metals by the fungusAspergillus niger. We analyzed the resistance to some heavy metals by dry weight and plate: the fungus grew in 2000 ppm of zinc, lead, and mercury, 1200 and 1000 ppm of arsenic (III) and (VI), 800 ppm of fluor and cobalt, and least in cadmium (400 ppm). With respect to their potential of removal of heavy metals, this removal was achieved for zinc (100%), mercury (83.2%), fluor (83%), cobalt (71.4%), fairly silver (48%), and copper (37%). The ideal conditions for the removal of 100 mg/L of the heavy metals were 28°C, pH between 4.0 and 5.5, 100 ppm of heavy metal, and 1 g of fungal biomass.

In previous research 1 it was shown that in grating-based phase-contrast imaging (GB-PCI) for low scatter objects, G2 is the dominant scattering source. This scatter is manifested in a different way compared to object scatter, as scattered photons that remain local to the interaction site may even increase object contrast, but reduce system visibility. In this work the magnitude and the spatial distribution of scattered photons from G2 are studied for different conditions using Monte Carlo simulations: (1) The effect of G2 orientation on the scatter-to-primary ratios (SPRs), (2) the impact of reducing the G2-to-detector distance ( D ) from 1.21 cm (current setting) to 0.5 cm on the spatial scatter distribution, and (3) the possibility to apply the G2 scatter probability to predict the scatter images from any primary object image. It was shown that flipping the G2 grating with its substrate away from the detector reduces the scatter-to-primary ratio by a factor 1.15. Furthermore, when D is 1.21 cm, 50% of the scattered photons fell within the first 18 pixels, while for D equal to 0.5 cm, 50% fell within the first 9 pixels, with however a slightly increased SPR. It was shown that convolution of these spatial distributions with the primary images of low scattering objects allows prediction of scatter images with a mean percentage deviation of 21% and 16% for D is 0.5 and 1.21 cm respectively. This work therefore illustrates that small optimization steps can have a notable impact on the magnitude and spatial distribution of scattered radiation at the level of the detector in GB-PCI. An approach to estimate scattered radiation images for objects that produce low levels of scattered radiation was presented.

We study orbital entanglement production in a chaotic cavity connected to four single-channel normal-metal leads and one superconducting lead, assuming the presence of time-reversal symmetry and within a random matrix theory approach. The scattered state of two incident electrons is written as the superposition of several two-outgoing quasi-particle components, four of which are orbitally entangled in a left-right bipartition. We calculate numerically the mean value of the squared norm of each entangled component, as functions of the number of channels in the superconducting lead. Its behavior is explained as resulting from the proximity effect. We also study statistically the amount of entanglement carried by each pair of outgoing quasi-particles. When the influence of the superconductor is more intense, the device works as an entangler of electron-hole pairs, and the average entanglement is found to be considerably larger than that obtained without the superconducting lead.

The biosorption of arsenic (V) on nine chemically modified biomasses (with iron oxide coated) of mycelia fungi: Aspergillus flavus III, IV and V, Aspergillus fumigatus I–II, Paecilomyces sp., Cladosporium sp., Mucor sp-1 and 2 was studied in this work. This study provides evidence that the biomasses of the fungi A. flavus, IV, III and V, Paecilomyces sp., and A. fumigatus I were very efficient at removing 1 mg/L of the metal in solution, using atomic absorption spectroscopy (AAS), achieving the following percentage of removals: 97.1, 92.3, 90.3, 89.0, and 83.4%, respectively. The results of adsorption were obtained at pH 6.0, 30 °C after 24 h of incubation, with 1 g/100 mL of fungal biomass. These results suggest the excellent potential of almost all isolated strains for bioremediation and removal of metals from contaminated sites.

This work proposes a method for assessing the detective quantum efficiency (DQE) of radiographic imaging systems that include both the x-ray detector and the antiscatter device. Cascaded linear analysis of the antiscatter device efficiency (DQEASD) with the x-ray detector DQE is used to develop a metric of system efficiency (DQEsys); the new metric is then related to the existing system efficiency parameters of effective DQE (eDQE) and generalized DQE (gDQE). The effect of scatter on signal transfer was modelled through its point spread function (PSF), leading to an x-ray beam transfer function (BTF) that multiplies with the classical presampling modulation transfer function (MTF) to give the system MTF. Expressions are then derived for the influence of scattered radiation on signal-difference to noise ratio (SDNR) and contrast-detail (c-d) detectability. The DQEsys metric was tested using two digital mammography systems, for eight x-ray beams (four with and four without scatter), matched in terms of effective energy. The model was validated through measurements of contrast, SDNR and MTF for poly(methyl)methacrylate thicknesses covering the range of scatter fractions expected in mammography. The metric also successfully predicted changes in c-d detectability for different scatter conditions. Scatter fractions for the four beams with scatter were established with the beam stop method using an extrapolation function derived from the scatter PSF, and validated through Monte Carlo (MC) simulations. Low-frequency drop of the MTF from scatter was compared to both theory and MC calculations. DQEsys successfully quantified the influence of the grid on SDNR and accurately gave the break-even object thickness at which system efficiency was improved by the grid. The DQEsys metric is proposed as an extension of current detector characterization methods to include a performance evaluation in the presence of scattered radiation, with an antiscatter device in place. ispartof: Physics in Medicine and Biology vol:62 issue:14 pages:5691-5722 ispartof: location:England status: published

Pseudochaotic properties are systematically investigated in a one-parameter family of irrational triangular billiards (all angles irrational with $\ensuremath{\pi}$). The absolute value of the position correlation function ${C}_{x}(t)$ decays like $\ensuremath{\sim}$${t}^{\ensuremath{-}\ensuremath{\alpha}}$. Fast $(\ensuremath{\alpha}\ensuremath{\approx}1)$ and slow $(0l\ensuremath{\alpha}l1)$ decays are observed, thus indicating that the irrational triangles do not share a unique ergodic dynamics, which, instead, may vary smoothly between the opposite limits of strong mixing $(\ensuremath{\alpha}=1)$ and regular behaviors $(\ensuremath{\alpha}=0)$. Upgrading previous data, spectral statistical properties of the quantized counterparts are computed from $150\phantom{\rule{0.16em}{0ex}}000$ energy eigenvalues numerically calculated for each billiard. Gaussian orthogonal ensemble spectral fluctuations are observed when $\ensuremath{\alpha}\ensuremath{\approx}1$ and intermediate statistics are found otherwise. Our irrational billiards have zero Kolmogorov-Sinai entropy and essentially infinity genus. Thus, differently from previous works on rational (pseudointegrable) enclosures, our results provide a missing classical-quantum correspondence regarding the ergodic hierarchy for a set of nonchaotic systems that might enjoy the strong mixing property.

We consider statistics of electronic transport in chaotic cavities where time-reversal symmetry is broken and one of the leads is weakly non-ideal, i.e. it contains tunnel barriers characterized by tunneling probabilities $\Gamma_i$. Using symmetric function expansions and a generalized Selberg integral, we develop a systematic perturbation theory in $1-\Gamma_i$ valid for arbitrary number of channels, and obtain explicit formulas up to second order for the average and variance of the conductance, and for the average shot-noise. Higher moments of the conductance are considered to leading order., Comment: 6 pag., 2 fig. - submitted to PRB

We investigate entanglement production in a generic normal conductor, connected to two single-channel left leads and two single-channel right leads. We consider the joint statistics of the number of entangled pairs produced during a given time and amount of entanglement carried by them. We find a constraint that implies that more entangled states are less likely to be detected. Namely, if $\mathcal{C}$ is the concurrence and $\mathcal{N}$ is the squared norm of the entangled state, then production occurs only if $\mathcal{N}(1+\mathcal{C})l1$. For the particular case of a chaotic cavity working as quantum entangler, we obtain explicit expressions for the joint distribution of $\mathcal{C}$ and $\mathcal{N}$, both for systems with and without time-reversal symmetry.

A stub model is introduced to describe the charge transport properties of a system consisting of an arbitrary number of noncollinear ferromagnetic or normal reservoirs coupled nonideally to a normal metal chaotic cavity. We characterize the contacts by a reduced set of parameters which can be used to express the average value of any charge-transfer cumulant. Explicit expressions of this set of parameters are given for the cases of ideal ballistic contacts and tunnel junctions. The average conductance and shot-noise power of a two terminal FNF device with noncollinear ferromagnetic reservoirs are calculated analytically via an extended diagrammatic method which allows for the importation of all diagrams of the corresponding NNN system. We observe that the Fano factor exhibits a transition between monotonic and nonmonotonic behaviors as a function of the reservoir's relative magnetization angle. A diagram of this transition in the plane of the polarization parameters is shown. With straightforward modifications, our scheme paves the way for efficient calculations of the average value of an arbitrary cumulant of the charge-transfer statistics in hybrid devices along with its quantum corrections.

We proposed a probabilistic algorithm to solve the Multiple Sequence Alignment problem. The algorithm is a Simulated Annealing (SA) that exploits the representation of the Multiple Alignment between $D$ sequences as a directed polymer in $D$ dimensions. Within this representation we can easily track the evolution in the configuration space of the alignment through local moves of low computational cost. At variance with other probabilistic algorithms proposed to solve this problem, our approach allows for the creation and deletion of gaps without extra computational cost. The algorithm was tested aligning proteins from the kinases family. When D=3 the results are consistent with those obtained using a complete algorithm. For $D>3$ where the complete algorithm fails, we show that our algorithm still converges to reasonable alignments. Moreover, we study the space of solutions obtained and show that depending on the number of sequences aligned the solutions are organized in different ways, suggesting a possible source of errors for progressive algorithms., 7 pages and 11 figures

We study the current-induced torque for electrons on ferromagnet-normal metal-ferromagnet (FNF) trilayer with non-collinear magnetizations. Our system is composed of a chaotic cavity and two junctions, coupled with ideal contacts to ferromagnetic reservatories in local equilibrium by means of a small number of scattering channels. We assume that the normal part is disordered. Each junction is related to the direction of the reservoirs magnetization. The system is taken out of equilibrium causing a spin accumulation. We suppose that all elements have a length smaller than the coherence phase and the spin flip lengths. This consideration lets us neglect decoherence and spin flip processes. The conductance and torque were found numerically by employing the random-matrix theory and scattering matrix formalism for the spin-flux. The observables are presented as a function of the number of propagating channels in the extreme quantum limit regime and of the angle between the magnetizations of the different ferromagnet layers.

A rapid and simple method of analysis of silicate rocks using gold crucibles and fluoroboric acid as a solvent of the disintegrated material has been developed. The main elements are determined in a single treatment. The results obtained are comparable to the values recommended for samples of eleven standard rocks.