Relative sensitivity of combined standard uncertainty to changes induced in uncertainty components

This work provides a straightforward and rigorous solution to the problem of evaluating and expressing relative changes in combined uncertainty resulting from relative changes in the uncertainty components. The acquired information is essential to optimize the measurement method, indicating the most significant components to work with. This approach works for any discrete relative change in the uncertainties of the inputs, whether positive or negative, and was developed for the cases of independent and correlated quantities. Examples of both cases are treated. The results agree with that provided by direct calculation and are consistent with the ideas in EA 4/16. We propose the use of the expression “sensitivity of combined standard uncertainty to changes in uncertainty components” as a uniform quantitative reference to the individual importance of the components that form the combined uncertainty. We also discuss the reason to avoid the use of the expression “contribution of an uncertainty component to the combined uncertainty.”     

In-Situ Synthesis and Characterization of Nanocomposites in the Si-Ti-N and Si-Ti-C Systems

The pyrolysis (1000 °C) of a liquid poly(vinylmethyl-co-methyl)silazane modified by tetrakis(dimethylamido)titanium in flowing ammonia, nitrogen and argon followed by the annealing (1000–1800 °C) of as-pyrolyzed ceramic powders have been investigated in detail. We first provide a comprehensive mechanistic study of the polymer-to-ceramic conversion based on TG experiments coupled with in-situ mass spectrometry and ex-situ solid-state NMR and FTIR spectroscopies of both the chemically modified polymer and the pyrolysis intermediates. The pyrolysis leads to X-ray amorphous materials with chemical bonding and ceramic yields controlled by the nature of the atmosphere. Then, the structural evolution of the amorphous network of ammonia-, nitrogen- and argon-treated ceramics has been studied above 1000 °C under nitrogen and argon by X-ray diffraction and electron microscopy. HRTEM images coupled with XRD confirm the formation of nanocomposites after annealing at 1400 °C. Their unique nanostructural feature appears to be the result of both the molecular origin of the materials and the nature of the atmosphere used during pyrolysis. Samples are composed of an amorphous Si-based ceramic matrix in which TiN_xC_y nanocrystals (x + y = 1) are homogeneously formed “in situ” in the matrix during the process and evolve toward fully crystallized compounds as TiN/Si₃N₄, TiN_xC_y (x + y = 1)/SiC and TiC/SiC nanocomposites after annealing to 1800 °C as a function of the atmosphere.     

A method for calibration and validation subset partitioning

This paper proposes a new method to divide a pool of samples into calibration and validation subsets for multivariate modelling. The proposed method is of value for analytical applications involving complex matrices, in which the composition variability of real samples cannot be easily reproduced by optimized experimental designs. A stepwise procedure is employed to select samples according to their differences in both x (instrumental responses) and y (predicted parameter) spaces. The proposed technique is illustrated in a case study involving the prediction of three quality parameters (specific mass and distillation temperatures at which 10 and 90% of the sample has evaporated) of diesel by NIR spectrometry and PLS modelling. For comparison, PLS models are also constructed by full cross-validation, as well as by using the Kennard-Stone and random sampling methods for calibration and validation subset partitioning. The obtained models are compared in terms of prediction performance by employing an independent set of samples not used for calibration or validation. The results of F-tests at 95% confidence level reveal that the proposed technique may be an advantageous alternative to the other three strategies.     

Letter: Bounds on the Deficit Solid Angle Parameter from Solar System Tests

We analyze the Mercury perihelion precession, the bending of starlight, and the radar echo delay in the Schwarzschild field modified by the presence of a solid angle deficit. By using the experimental data we obtain that the parameter characterizing the solid angle deficit is less than 10^–9, 10^–8 and 10^–9, respectively, on the length scales associated with such phenomena. In particular, if the solid angle deficit is generated by a global monopole, it is shown that within the length scales associated with such phenomena, the observational data available constrain the monopole energy scale to lower bounds which are in considerable agreement with the limits derived from grand unified theory and cosmology.     

Discrimination among eight modified michaelis-menten kinetics models of cellulose hydrolysis with a large range of substrate/enzyme ratios

The kinetics of exoglucanase (Cel7A) from Trichoderma reesei was investigated in the presence of cellobiose and 24 different enzyme/Avicel ratios for 47 h, in order to establish which of the eight available kinetic models best explained the factors involved. The heterogeneous catalysis was studied and the kinetic parameters were estimated employing integrated forms of Michaelis-Menten equations through the use of nonlinear least squares. It was found that cellulose hydrolysis follows a model that takes into account competitive inhibition by cellobiose (final product) with the following parameters: Km = 3.8 mM, Kic = 0.041 mM, kcat = 2 h-1 (5.6 x 10-4 s-1). Other models, such as mixed type inhibition and those incorporating improvements concerning inhibition by substrate and parabolic inhibition, increased the modulation performance very slightly. The results support the hypothesis that nonproductive enzyme substrate complexes, parabolic inhibition, and enzyme inactivation (Selwyn test) are not the principal constraints in enzymatic cellulose hydrolysis. Under our conditions, the increment in hydrolysis was not significant for substrate/enzyme ratios <6.5.     

Immobilization of Anti-Galectin-3 onto Polysiloxane–Polyvinyl Alcohol Disks for Tumor Prostatic Diseases Diagnosis

This work aimed to immobilize the antibody anti-galectin-3 onto polysiloxane–polyvinyl alcohol (POS-PVA) support, to evaluate its capacity to capture the serum antigen galectin-3 and to quantify by ELISA the antigen levels in sera from patients with prostatic adenocarcinoma (PA) and benign prostatic hyperplasia (BPH) and healthy individuals. Also, for comparative effect, the galectin-3 expression in the prostate tissue through immunohistochemistry was evaluated. The optical density (galectin-3 level) values established for the sera from PA and BPH patients were lower compared with those found for the healthy individuals. Galectin-3 immunohistochemically showed a significant increase and reduction of the cytoplasmatic protein expression in BPH and PA, respectively, compared with the normal prostate. These results showed that POS-PVA disks could be used as solid phase to immobilize serum galectins and in immunoassays procedures for the correspondent IgG anti-galectins detection in human sera.     

Thermal characterization of usnic acid/collagen-based films

The purpose of this study was to evaluate the physical–chemical properties of collagen (CL) and usnic acid/collagen-based (UAC) films, using differential thermal analysis (DTA), thermogravimetry (TG/DTG), infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Both films were prepared by casting process using polyethylene glycol 1500 (PEG 1500) as plasticizer. In the spectrum of UAC, similar bands of the usnic acid are observed, indicating that the polymerization (film formation) did not affect the stability of the drug. Distinctly, DTA curve of UAC did not show an endothermic peak at 201 °C, indicative that the drug was incorporated into the polymeric system. These results were corroborated by the scanning electron microscopy (SEM). The TG/DTG curves of UAC presented a different thermal decomposition profile compared to the individual compounds and CL. These findings suggest the occurrence of molecular dispersion or solubilization of the drug in the collagen film.     

Transmission fingerprints in quasiperiodic magnonic multilayers

In this paper we investigated the influence of mirror symmetry on the transmission spectra of quasiperiodic magnonic multilayers arranged according to Fibonacci, Thue-Morse and double period quasiperiodic sequences. We consider that the multilayers composed of two simple cubic Heisenberg ferromagnets with bulk exchange constants J_A and J_B and spin quantum numbers S_A and S_B, respectively. The multilayer structure is surrounded by two semi-infinite slabs of a third Heisenberg ferromagnetic material with exchange constant J_C and spin quantum number S_C. For simplicity, the lattice constant has the same value a in each material, corresponding to epitaxial growth at the interfaces. The transfer matrix treatment was used for the exchange-dominated regime, taking into account the random phase approximation (RPA). Our numerical results illustrate the effects of mirror symmetry on (i) transmission spectra and (ii) transmission fingerprints.     

The use of apatite fission track thermochronology to constrain fault movements and sedimentary basin evolution in northeastern Brazil

An apatite fission track study of crystalline rocks underlying sedimentary basins in northeastern Brazil indicate that crustal blocks that occur on opposite sides of a geological fault experienced different thermal histories. Samples collected on the West block yielded corrected fission-track ages from 140 to 375 Ma, whereas samples collected on the East block yielded ages between 90 and 125 Ma. The thermal models suggest that each block experienced two cooling events separated by a heating event at different times. We concluded that the West block moved downward relative to the East block ca. 140 Ma ago, when sediments eroded from the East side were deposited on the West side. This process represents the early stage of sedimentary basin formation and the opening of the South Atlantic Ocean in the region. Downward and upward movements related to heating and cooling events of these crustal blocks at different periods until recent times are proposed.     

Geometric Phase in Quaternionic Quantum Mechanics

Quaternion quantum mechanics is examined at the level of unbroken SU(2) gauge symmetry. A general quaternionic phase expression is derived from formal properties of the quaternion algebra.