Analysis of mineral water from Brazil using total reflection X-ray fluorescence by synchrotron radiation

The total reflection X-ray fluorescence using synchrotron radiation (SRTXRF) has become a competitive technique for the determination of trace elements in samples that the concentrations are lower than 100 ng ml⁻¹. In this work, thirty-seven mineral waters commonly available in supermarkets of Rio de Janeiro, Brazil, were analyzed by SRTXRF. The measurements were performed at the X-Ray Fluorescence Beamline at Brazilian National Synchrotron Light Laboratory (LNLS), in Campinas, São Paulo, using a polychromatic beam with maximum energy of 20 keV for the excitation. Standard solutions with gallium as internal standard were prepared for calibration of the system. Mineral water samples of 10 μl were added to Perspex sample carrier, dried under infrared lamp and analyzed for 200 s measuring time. It was possible to determine the concentrations of the following elements: Si, S, K, Ca, Ti, Cr, Mn, Ni, Cu, Zn, Ge, Rb, Sr, Ba and Pb. The elemental concentration values were compared with the limits established by the Brazilian legislation.     

Topographic trace-elemental analysis in the brain of Wistar rats by X-ray microfluorescence with synchrotron radiation

Knowledge about the spatial distribution and the local concentration of trace elements in tissues is of great importance, since trace elements are involved in many biological functions of living organisms. However, there are few methods available to measure the spatial (two (three)-dimensional) elemental distribution in animal brain. X-ray microfluorescence with synchrotron radiation is a multielemental mapping technique, which was used in this work to determine the topographic of iron, zinc and copper in coronal sections of female Wistar rats of different ages. Young (14 days old) and middle-aged (20 months old) rats (n = 8) were analyzed. The measurements were carried out at the XRF beam line at the Synchrotron Light National Laboratory (Campinas, Brazil). Two-dimensional scanning was performed in order to study the tendency of elemental concentration variation. The acquisition time for each pixel was 10 s/step and the step size was 300 microm/step in both directions. It was observed that the iron distribution was more conspicuous in the cortical area, thalamus and bellow the thalamus. On the other hand, the zinc distribution was more pronounced in the hippocampus. The iron, copper and zinc levels increased with advancing age. Therefore, this study reinforces the idea that these elements are involved in the chemical mechanisms of the brain that induce some neurological diseases, since they are also present in high levels in specific areas of the brain, such as the hippocampus and the substantia nigra of patients with these disorders.     

The Deck model in the reaction dp → d(Nπ)+

A Deck-like model is proposed for the reaction pd → (Nπ)⁺d. The narrow bump Nπ (1150 MeV) is well explained. The different hypothesis and approximations are widely reviewed. In particular other mechanisms which can contribute to the same reaction are calculated and off-shell effects are discussed.     

Study of the decay D0 --> K+pi-

Using a large sample of photoproduced charm mesons from the FOCUS experiment at Fermilab (FNAL-E831), we observe the decay D0-->K+pi- with a signal yield of 149+/-31 events compared to a similarly cut sample consisting of 36 760+/-195 D0-->K-pi+ events. We use the observed ratio of D0-->K+pi- to D0-->K-pi+ (0.404+/-0.085+/-0.025)% to obtain a relationship between the D0 mixing and doubly Cabibbo suppressed decay parameters.     

Dalitz plot analysis of the decay D(+)-->K(-)pi(+)pi(+) and indication of a low-mass scalar Kpi resonance

We study the Dalitz plot of the decay D(+)-->K(-)pi(+)pi(+) with a sample of 15090 events from Fermilab experiment E791. Modeling the decay amplitude as the coherent sum of known Kpi resonances and a uniform nonresonant term, we do not obtain an acceptable fit. If we allow the mass and width of the K(*)(0)(1430) to float, we obtain values consistent with those from PDG but the chi(2) per degree of freedom of the fit is still unsatisfactory. A good fit is found when we allow for the presence of an additional scalar resonance, with mass 797+/-19+/-43 MeV/c(2) and width 410+/-43+/-87 MeV/c(2). The mass and width of the K(*)(0)(1430) become 1459+/-7+/-5 MeV/c(2) and 175+/-12+/-12 MeV/c(2), respectively. Our results provide new information on the scalar sector in hadron spectroscopy.     

Effect of silica/alumina ratio and structure-directing agent on the physical and chemical properties of SAPO-34

Journal of Sol-Gel Science and Technology - This work describes how the silica/alumina ratio (SAR) affects the framework, texture, chemical composition, and acidity of SAPO-34 molecular sieves...     

Framework for enhancing the estimation of model parameters for data with a high level of uncertainty

Nonlinear Dynamics - Reliable data are essential to obtain adequate simulations for forecasting the dynamics of epidemics. In this context, several political, economic, and social factors may cause...     

Lattice preconditioning for the real relaxation branch-and-bound approach for integer least squares problems

The integer least squares problem is an important problem that arises in numerous applications. We propose a real relaxation-based branch-and-bound (RRBB) method for this problem. First, we define a quantity called the distance to integrality, propose it as a measure of the number of nodes in the RRBB enumeration tree, and provide computational evidence that the size of the RRBB tree is proportional to this distance. Since we cannot know the distance to integrality a priori, we prove that the norm of the Moore–Penrose generalized inverse of the matrix of coefficients is a key factor for bounding this distance, and then we propose a preconditioning method to reduce this norm using lattice reduction techniques. We also propose a set of valid box constraints that help accelerate the RRBB method. Our computational results show that the proposed preconditioning significantly reduces the size of the RRBB enumeration tree, that the preconditioning combined with the proposed set of box constraints can significantly reduce the computational time of RRBB, and that the resulting RRBB method can outperform the Schnorr and Eucher method, a widely used method for solving integer least squares problems, on some types of problem data.