Search results for "Coupled"
showing 10 items of 742 documents
The capability of Rare Earth Elements geochemistry to interpret complex archaeological stratigraphy
2019
Abstract In this study rare earth elements (REE) signatures (REE ratios, cerium and europium anomalies) are applied to a complex soil stratigraphic sequence from the site of Konso, Ethiopia, with the aim of determining whether REE can distinguish the strata observed in the field. Forty soil samples were taken from a depositional sequence that includes overlapping human induced and ‘natural’ erosional and depositional processes. The samples were analysed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to determine trace elements and REE, with concentrations of major elements determined using X-ray fluorescence (XRF). Cluster Analyses (CA) were used to observe differences between str…
A statistical design of experiments for optimizing the MALDI-TOF-MS sample preparation of polymers. An application in the assessment of the thermo-me…
2011
[EN] The sample preparation procedure for MALDI-TOF MS of polymers is addressed in this study by the application of a statistical Design of Experiments (DoE). Industrial poly (ethylene terephthalate) (PET) was chosen as model polymer. Different experimental settings (levels) for matrixes, analyte/matrix proportions and concentrations of cationization agent were considered. The quality parameters used for the analysis were signal-to-noise ratio and resolution. A closer inspection of the statistical results provided the study not only with the best combination of factors for the MALDI sample preparation, but also with a better understanding of the influence of the different factors, individua…
Implementation of the full explicitly correlated coupled-cluster singles and doubles model CCSD-F12 with optimally reduced auxiliary basis dependence.
2008
An implementation of the full explicitly correlated coupled-cluster singles and doubles model CCSD-F12 using a single Slater-type geminal has been obtained with the aid of automated term generation and evaluation techniques. In contrast to a previously reported computer code [T. Shiozaki et al., J. Chem. Phys. 129, 071101 (2008)], our implementation features a reduced dependence on the auxiliary basis set due to the use of a reformulated evaluation of the so-called Z-intermediate rather than straight forward insertion of an auxiliary basis expansion, which allows an unambiguous comparison to more approximate CCSD-F12 models. First benchmark results for total correlation energies and reactio…
Liquid sample introduction in inductively coupled plasma atomic emission and mass spectrometry — Critical review
2014
Abstract Inductively coupled plasma optical emission spectroscopy (ICP-OES) and mass spectrometry (ICP-MS) can be considered as the most important tools in inorganic analytical chemistry. Huge progress has been made since the first analytical applications of the ICP. More stable RF generators, improved spectrometers and detection systems were designed along with the achievements gained from advanced microelectronics, leading to overall greatly improved analytical performance of such instruments. In contrast, for the vast majority of cases liquid sample introduction is still based on the pneumatic principle as described in the late 19th century. High flow pneumatic nebulizers typically deman…
Green direct determination of mineral elements in artichokes by infrared spectroscopy and X-ray fluorescence.
2015
Near infrared (NIR) and X-ray fluorescence (XRF) spectroscopy were investigated to predict the concentration of calcium, potassium, iron, magnesium, manganese and zinc in artichoke samples. Sixty artichokes were purchased from different Spanish areas (Benicarlo, Valencia and Murcia). NIR and XRF spectra, combined with partial least squares (PLS) data treatment, were used to develop chemometric models for the prediction of mineral concentration. To obtain reference data, samples were mineralised and analysed by inductively coupled plasma optical emission spectrometry (ICP-OES). Coefficients of determination obtained for the regression between predicted values and reference ones for calcium, …
Chemical characterization of ancient liturgical vestment (chasuble) by Inductively Coupled Plasma–Optical Emission Spectrometry (ICP–OES)
2016
Abstract This paper presents the chemical characterization of the yarns of an ancient liturgical vestment (chasuble). The samples have been analyzed for Al, Ag, Au, Cd, Co, Cr, Cu, Ni, Pb and Zn using amounts always less than 1 mg by Inductively Coupled Plasma–Optical Emission Spectrometry (ICP-OES). Except a sample, silver is the most abundant element in all the yarns. In the samples containing silver, it ranged from 68 to 97%. Only two samples contain aluminum. Although the investigated chasuble is recorded in the inventory as an artifact of the XV century, a part of the yarns is composed of materials attributed to later period. In fact, the voluntary use of aluminum in metal alloys is du…
Principle and analytical applications of resonance lonization mass spectrometry
1989
Resonance ionization mass spectrometry (RIMS) is a very sensitive analytical technique for the detection of trace elements. This method is based on the excitation and ionization of atoms with resonant laser light followed by mass analysis. It allows element and, in some cases, isotope selective ionization and is applicable to most of the elements of the periodic table. A high selectivity can be achieved by applying three step photoionization of the elements under investigation and an additional mass separation for an unambiguous isotope assignment. An effective facility for resonance ionization mass spectrometry consists of three dye lasers which are pumped by two copper vapor lasers and of…
Coupled Susy, pseudo-bosons and a deformed su(1, 1) Lie algebra
2021
Abstract In a recent paper a pair of operators a and b satisfying the equations a † a = bb † + γ 1 and aa † = b † b + δ 1 , has been considered, and their nature of ladder operators has been deduced and analyzed. Here, motivated by the spreading interest in non self-adjoint operators in quantum mechanics, we extend this situation to a set of four operators, c, d, r and s, satisfying dc = rs + γ 1 and cd = sr + δ 1 , and we show that they are also ladder operators. We show their connection with biorthogonal families of vectors and with the so-called D -pseudo bosons. Some examples are discussed.
Spin-1/2 sub-dynamics nested in the quantum dynamics of two coupled qutrits
2017
In this paper we investigate the quantum dynamics of two spin-1 systems, $\vec{\textbf{S}}_1$ and $\vec{\textbf{S}}_2$, adopting a generalized $(\vec{\textbf{S}}_1+\vec{\textbf{S}}_2)^2$-nonconserving Heisenberg model. We show that, due to its symmetry property, the nine-dimensional dynamics of the two qutrits exactly decouples into the direct sum of two sub-dynamics living in two orthogonal four- and five-dimensional subspaces. Such a reduction is further strengthened by our central result consisting in the fact that in the four-dimensional dynamically invariant subspace, the two qutrits quantum dynamics, with no approximations, is equivalent to that of two non interacting spin 1/2's. The …
Increased dynamic effects in a catalytically compromised variant of Escherichia coli dihydrofolate reductase
2013
Isotopic substitution (15N, 13C, 2H) of a catalytically compromised variant of Escherichia coli dihydrofolate reductase, EcDHFR-N23PP/S148A, has been used to investigate the effect of these mutations on catalysis. The reduction of the rate constant of the chemical step in the EcDHFR-N23PP/S148A catalyzed reaction is essentially a consequence of an increase of the quasi-classical free energy barrier and to a minor extent of an increased number of recrossing trajectories on the transition state dividing surface. Since the variant enzyme is less well set up to catalyze the reaction, a higher degree of active site reorganization is needed to reach the TS. Although millisecond active site motion…