A solvable version of the collisional random phase approximation

We derive the markovian limit of the collisional Random Phase Approximation (CRPA) by resort to the linearization of the Collisional Time-Dependent-Hartree-Fock (CTDHF) equation of motion for the one-body density matrix. The CRPA spectral problem is numerically solved in the frame of a model consisting of a finite fermion system with axial symmetry interacting by means of a separable force. Calculations are performed within a range of interaction strengths, temperature and size parameters and it is shown that both the centroids and the widths of the high energy collective modes exhibit the trend of experimental data.     

Automated separation and preconcentration of copper(II) from natural waters using a column treatment

Summary A comparison is made between two automated column procedures for the separation and preconcentration of Cu(II) from natural waters. The column materials were: an anion-exchange resin and 8-hydroxyquinoline immobilized on a glass support. 8-Hydroxyquinoline showed about the same performance as the ion exchange resin, but was less time and labour consuming. Cu(II) determinations at the ppb level were checked with standard additions and the results were moreover compared with those obtained by another method.On leave from Lisbon University, Portugal     

Note on the uranyl complexes of EDTA

The nature of the EDTA complex of uranium(VI) is discussed, and it is concluded that there is no need to postulate stabilization of the complex by hydrogen-bonding between a protonated nitrogen atom and the uranyl ion.     

Studies on the cellulose-binding domains adsorption to cellulose

Cellulose-binding domains (CBD) are modular peptides, present in many glycanases, which anchor these enzymes to the substrate. In this work, the effect of CBD adsorption on the surface properties of a model cellulose, Whatman CF11, was studied. The methods applied include inverse gas chromatography (IGC), ESCA, X-ray diffraction, and scanning electron microscopy (SEM). The CBD partition affinity (0.85 L/g) was calculated from adsorption isotherms. However, true adsorption equilibrium does not exist, since CBDs are apparently irreversibly adsorbed to the fibers. Both IGC and ESCA showed that fibers with adsorbed CBD have a lower acidic character and also a slightly higher affinity toward aliphatic molecules. This may however be a consequence of an increased surface area, a hypothesis that is supported by microscopic observations. The crystallinity index was not affected by CBD treatment.     

Kolmogorov complexity as a data similarity metric: application in mitochondrial DNA

The problem of developing a similarity index for different objects is discussed. The limitations of current metrics are evaluated and discussed. The normalized compression distance, based on the non-computable Kolmogorov complexity, is examined and compared with two alternative measures. A case study consisting of a phylogenetic tree of different mammals is constructed applying this technique with a mitochondrial DNA database.     

Frontal Polymerization of Deep Eutectic Solvents Composed of Acrylic and Methacrylic Acids

Frontal polymerization of deep eutectic solvents (DESs) made with acrylic or methacrylic acid as the monomer and hydrogen bond donor was studied. Fronts with acrylic acid and choline chloride propagated more uniformly than with pure acrylic acid, so an exploration into how the DES affected frontal polymerization was performed. The hydrogen bond acceptor of the DES was replaced by several analogs to determine the effect on the DES front behavior. The analogs used were talc, DMSO, lauric acid, and stearic acid, which acted as a heat sink, inert diluent, hydrogen bonding diluent, and inert phase change material, respectively. None of the methacrylic acid‐analog systems were able to sustain a front. While the acrylic acid‐analog systems did sustain a front (with the exception of stearic acid), none of the fronts replicated the acrylic acid DES behavior. The acrylic acid–talc sample behaved more violently—like pure acrylic acid polymerization—than the acrylic acid DES, and the DMSO and lauric acid samples produced slower fronts than that of the acrylic acid DES. We propose that the reactivity of the acrylic acid and methacrylic acid is enhanced in the DES. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 4046–4050     

Sensitive harmonic detection of ammonia trace using a compact photoacoustic resonator at double-pass configuration and a wavelength-modulated distributed feedback diode laser

A sensitive detection of ammonia in parts per billion by volume is described. The system based on photoacoustic spectroscopy (PAS) consists of distributed feedback laser diode emitting near 1,531.7 nm and a compact PA cell at double-pass configuration. In order to optimize the signal background ratio of the system, two types of modulations were tested, amplitude and wavelength modulations (WM). Using a digital lock-in amplifier, the 1f and 2f detection in WM could be investigated. A detection limit of 470 parts per million by volume could be achieved at WM-2f. In the sense of quantifing the adsorption–desorption process, the response time of the system and detection accuracy was performed in different flows. Response times between 10 and 49 s, depending on the flow rate, were obtained which enables the PA system to measure low concentrations of ammonia with high accuracy in real time.     

Noninertial effects on nonrelativistic topological quantum scattering

We investigate noninertial effects on the scattering problem of a nonrelativistic particle in the cosmic string spacetime. By considering the nonrelativistic limit of the Dirac equation we are able to show, in the regime of small rotational frequencies, that the phase shift has two contribution: one related to the noninertial reference frame, and the other, due to the cosmic string conical topology. We also show that both the incident wave and the scattering amplitude are altered as a consequence of the noninertial reference frame and depend on the rotational frequency.