The coupled transport of Cu(II), Cd(II) and Ni(II) ions through a bulk liquid membrane (BLM) containing pyridine-2-acetaldehyde benzoylhydrazone (2-APBH) as carrier dissolved in toluene has been ...studied. Once the optimal conditions of extraction of each metal were established, a comparative study of the transport kinetics for these metals was performed by means of a kinetic model involving two consecutive irreversible first-order reactions. The kinetic parameters (apparent rate constants of the metal extraction and re-extraction reactions (k ₁, k ₂), the maximum reduced concentration of the metal in the liquid membrane ( graphic removed ), the time of the maximum value of R o ( t max) and the maximum entry and exit fluxes of the metal through the liquid membrane ( graphic removed and graphic removed ) of the extraction and stripping reactions were evaluated and results showed good agreement between experimental data and theoretical predictions. Complete transport through the membrane took place according to the following order: Cd(II)>Cu(II)>Ni(II), with similar kinetic parameters obtained for Cu(II) and Cd(III). The transport behaviour of Ni(II) was different to that of Cu(II) and Cd(III), probably due to the different stoichiometry of the nickel complex compared to those of the other metal ions and the different chemical conditions required for its formation. The influence of the sample salinity on the transport kinetics was studied. k ₁ values decreased slightly when the feed solution salinity was increased for Cu(II) and Ni(II), but not for Cd(II). Values of k ₂ were practically unaffected. The proposed BLM was applied to the preconcentration and separation of metal ions (prior to their determination) in water samples with different saline matrices (CRM, river water and seawater), and good agreement with the certified values was obtained.
A first-principle study of
(
Pt
3
Cu
)
n
n
= 10–11 nanoclusters was performed using the linear combination of Gaussian-type orbitals within the auxiliary density functional theory (ADFT) framework. ...Neutral, anionic and cationic clusters species were studied. To carry on a detailed exploration of the potential energy surface of these systems, Born-Oppenheimer molecular dynamics (BOMD) simulations have been performed. Several dozens of structures were taken along the generated BOMD trajectories as initial geometries for geometry optimizations. Successive geometry optimizations of these systems, in different electron spin multiplicities and without any type of restriction, were computed. The obtained optimized structures have been characterized by frequency analysis calculations. Computed minima structures, harmonic frequencies, average bond lengths, magnetic moments, spin density plots, dissociation energy, ionization potential and electron affinity are reported. The formation of octahedra moieties has been observed in the most stable structures. The findings of the growing pattern of these clusters can serve as guide to search a synthetic route that can yield nanoparticles with desired geometries and high stability.
Aims. We probe the high-energy (>60 MeV) emission from the black hole X-ray binary system, Cygnus X-1, and investigate its origin. Methods. We analyzed 7.5 yr of data by Fermi-LAT with the latest ...Pass 8 software version. Results. We report the detection of a signal at ~8σ statistical significance that is spatially coincident with Cygnus X-1 and has a luminosity of 5.5 × 1033 erg s-1, above 60 MeV. The signal is correlated with the hard X-ray flux: the source is observed at high energies only during the hard X-ray spectral state, when the source is known to display persistent, relativistic radio-emitting jets. The energy spectrum, extending up to ~20 GeV without any sign of spectral break, is well fit by a power-law function with a photon index of 2.3 ± 0.2. There is a hint of orbital flux variability, with high-energy emission mostly coming around the superior conjunction. Conclusions. We detected GeV emission from Cygnus X-1 and probed that the emission is most likely associated with the relativistic jets. The evidence of flux orbital variability indicates the anisotropic inverse-Compton on stellar photons as the mechanism at work, thus constraining the emission region to a distance 1011–1013 cm from the black hole.
In this work, a bulk liquid membrane method has been applied for Ni enrichment and separation from natural waters. The carrier-mediated transport was accomplished by pyridine-2-acetaldehyde ...benzoylhydrazone dissolved in toluene as a complexing agent. The preconcentration was achieved through pH control of source and receiving solutions via a counterflow of protons. The main variables were optimized by using a modified simplex technique. High transport efficiencies (101.2 ± 1.8-99.7 ± 4.2%) were provided by the carrier for nickel ions in a receiving phase of 0.31 mol L-¹ nitric acid after 9-13 h depending on sample salinity. The precision of the method was 2.05% (without a saline matrix) and 4.04% (with 40 g L-¹ NaCl) at the 95% confidence level and the detection limit of the blank was 0.015 μg L-¹ Ni for detection by atomic absorption spectroscopy. The applicability of the method was tested on certified reference and real water samples with successful results, even for saline samples. The relative errors were -0.60% for certified reference materials and ranged from -0.39 to 2.90% and from 0.3 to 11.05% for real samples, obtained by comparison of inductively coupled plasma mass spectrometry and adsorptive cathodic stripping voltammetry measurements, respectively.
The self-consistent Hartree-Fock-Bogoliubov problem in large boxes can he solved accurately in the coordinate space with the recently developed solvers HFB-AX (2D) and MADNESS-HFB (3D). This is ...essential for the description of superfluid Fermi systems with complicated topologies and significant spatial extend, such as fissioning nuclei, weakly-bound nuclei, nuclear matter in the neutron star rust, and ultracold Fermi atoms in elongated traps. The HFB-AX solver based on B-spline techniques uses a hybrid MPI and OpenMP programming model for parallel computation for distributed parallel computation, within a node multi-threaded LAPACK and BLAS libraries are used to further enable parallel calculations of large eigensystems. The MADNESS-HFB solver uses a novel multi-resolution analysis based adaptive pseudo-spectral techniques to enable fully parallel 3D calculations of very large systems. In this work we present benchmark results for HFB-AX and MADNESS-HFB on ultracold trapped fermions.
Invasive plants such as Castor bean (Ricinus communis) are known to threaten ecosystems due to their competition for resources. The Ballona Wetlands and Temescal Canyon managers employ different ...techniques to manage the spread of R. communis, potentially resulting in differences in plant survivorship. To investigate this possibility, height of the stems of individual R. communis plants at each site were recorded in order to assign them to cohort groups. Based on the hypothesis predicted that R. communis would have a similar cohort structure at both sites but would exhibit higher survivorship at Temescal Canyon, where R. communis are removed less frequently than at the Ballona Wetlands. However, results indicate that management does not affect cohort structure or stability at either site, but rather, it may have contributed to the significantly higher overall survivorship of R. communis at Temescal Canyon.
Previous studies have shown a positive relationship between biomass of the common wetland halophyte, Salicornia virginica, and salinity. This study implements a new technique that is less invasive ...than measuring total plant biomass that involves uprooting the plant. Instead, plant height was used as an indicator of sodium content in surrounding soils. This technique is based on the hypothesis that plant height of S. virginica corresponds to soil sodium concentrations. There was a significant variation in plant height at higher soil sodium concentrations than at lower soil sodium concentrations. Furthermore, in areas of higher soil water content (%), sodium concentration was elevated.
We study the Uhlmann geometric phase of a spin-1 particle subjected to zero-field splitting (ZFS) interaction, modulated by a dimensionless parameter α, under the effect of an external magnetic field ...with a tilting angle θ. We show that the ZFS term induces a transition in the geometrical phase behavior, characterized by a critical parameter value, α=αc. For α<αc, this phase displays two critical temperatures at θ=π/2, similar to spin-1 systems without ZFS, but with a separation that varies with α. In contrast, for α>αc, the phase exhibits two singularities at a single critical temperature but at different field orientations θ≠π/2. The phase disappears for significantly large |α|, regardless of the values of the Hamiltonian parameters. This behavior clearly departs from the usual thermal Uhlmann phase observed in SU(2) systems. In addition, we analytically calculate the heat capacity, which, for θ=π/2 and nearby values, displays two different regimes according to the sign of α. For α<0, it develops two peaks associated to the multilevel nature of the system, while for α>0 only a single Schottky-anomaly like peak appears as in two level systems. Interestingly, when θ=π/2, the temperature centroids of the Uhlmann phase and the heat capacity coincide in the region between critical temperatures for a given value of α<αc. Furthermore, we demonstrate that when α=0, the Uhlmann phase, a global topological property of the system, can be expressed as a function of the thermal component of the Bures metric, a local geometric property related to the heat capacity.
•We study the Uhlmann phase of a spin-1 particle subjected to zero-field splitting (ZFS), under an external magnetic field.•The ZFS term (α) induces a phase transition depending on a critical value α=αc.•For α>αc, the phase exhibits two singularities at a single critical temperature but at different θ orientations (θ≠π/2).•The heat capacity shows two regimes: for α<0, two peaks appear; for α>0, a single Schottky-anomaly-like peak occurs.•Additionally, for α=0, the Uhlmann phase correlates with the thermal component of the Bures metric.
The transfer and separation of Cu(II) ions across a bulk liquid membrane (BLM) containing pyridine-2-acetaldehyde benzoylhydrazone (2-APBH) as the mobile carrier dissolved in toluene has been ...investigated and optimised. The system was applied to the preconcentration of copper from natural waters prior to analysis by flame atomic absorption spectroscopy. The flux of copper across the membrane has been studied, and characterised as a function of analytical variables such as the carrier concentration, volume of organic phase, pH of feed and strip receiving solutions, stirring rate and temperature of solutions. The preconcentration yield at optimum conditions was 100.54±0.94%, even with a high saline matrix (30
g
l
−1 NaCl), with good precision (1.49%). A preconcentration factor of approximately 18 times could be obtained. The detection limit of a blank sample was 0.24
μg
l
−1 of Cu.
The method was validated using a certified reference material (TMDA-62) and was applied successfully to the analysis of copper in two samples of seawater collected from the coast of Huelva (Spain). The relative errors were 2.42% for CRM and 0.48 and 3.66%, for seawaters (obtained between the results of the proposed and DPASV methods), respectively.
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