Estimation of PM10-bound As, Cd, Ni and Pb levels by means of statistical modelling: PLSR and ANN approaches

Air quality assessment regarding metals and metalloids using experimental measurements is expensive and time consuming due to the cost and time required for the analytical determination of the levels of these pollutants. According to the European Union (EU) Air Quality Framework Directive (Directive 2008/50/EC), other alternatives, such as objective estimation techniques, can be considered for ambient air quality assessment in zones and agglomerations where the level of pollutants is below a certain concentration value known as the lower assessment threshold. These conditions occur in urban areas in Cantabria (northern Spain). This work aims to estimate the levels of As, Cd, Ni and Pb in airborne PM10 at two urban sites in the Cantabria region (Castro Urdiales and Reinosa) using statistical models as objective estimation techniques. These models were developed based on three different approaches: partial least squares regression (PLSR), artificial neural networks (ANNs) and an alternative approach consisting of principal component analysis (PCA) coupled with ANNs (PCA-ANN). Additionally, these models were externally validated using previously unseen data. The results show that the models developed in this work based on PLSR and ANNs fulfil the EU uncertainty requirements for objective estimation techniques and provide an acceptable estimation of the mean values. As a consequence, they could be considered as an alternative to experimental measurements for air quality assessment regarding the aforementioned pollutants in the study areas while saving time and resources.The authors gratefully acknowledge the financial support from the Spanish Ministry of Economy and Competitiveness through the Project CMT2010-16068. The authors also thank the Regional Environment Ministry of the Cantabria Government for providing the PM10 samples at the Castro Urdiales and Reinosa sites

The role of the mitochondria and the endoplasmic reticulum contact sites in the development of the immune responses

Abstract Mitochondria and endoplasmic reticulum (ER) contact sites (MERCs) are dynamic modules enriched in subset of lipids and specialized proteins that determine their structure and functions. The MERCs regulate lipid transfer, autophagosome formation, mitochondrial fission, Ca2+ homeostasis and apoptosis. Since these functions are essential for cell biology, it is therefore not surprising that MERCs also play a critical role in organ physiology among which the immune system stands by its critical host defense function. This defense system must discriminate and tolerate host cells and beneficial commensal microorganisms while eliminating pathogenic ones in order to preserve normal homeostasis. To meet this goal, the immune system has two lines of defense. First, the fast acting but unspecific innate immune system relies on anatomical physical barriers and subsets of hematopoietically derived cells expressing germline-encoded receptors called pattern recognition receptors (PRR) recognizing conserved motifs on the pathogens. Second, the slower but very specific adaptive immune response is added to complement innate immunity. Adaptive immunity relies on another set of specialized cells, the lymphocytes, harboring receptors requiring somatic recombination to be expressed. Both innate and adaptive immune cells must be activated to phagocytose and process pathogens, migrate, proliferate, release soluble factors and destroy infected cells. Some of these functions are strongly dependent on lipid transfer, autophagosome formation, mitochondrial fission, and Ca2+ flux; this indicates that MERCs could regulate immunity

Interpreting Mössbauer spectra reflecting an infinite number of sites: an application to Fe1-xSi synthesized by pulsed laser annealing

We present a study on the interpretation of conversion electron Mossbauer spectra reflecting an infinite number of sites, in casu Mossbauer spectroscopy on Fe1-xSi layers on Si, synthesized by pulsed laser annealing. These spectra display a broad double-peaked resonance, reflecting the numerous different environments of the Fe-57 probe due to a distribution of vacancies on the Fe sublattice. The spectra can be fitted in many different ways; hence finding a reliable physical interpretation is not straightforward. Therefore ab initio calculations have been performed in order to obtain a priori information about the hyperfine interaction parameter distributions. For this material, the electric-field gradient on the Fe-57 atoms turns out to depend on details in the configuration of neighbors as far as the sixth neighbor shell. The isomer shift appears to be determined by the number of Fe atoms in the first and second Fe neighbor shells only. This leads to the construction of an ab initio based model predicting the mean isomer shift and its distribution for a given Fe1-xSi layer with a known Fe concentration profile. By applying this model new information from the experimental data can be extracted: we show that after applying one or two laser pulses, the Fe atoms are not completely randomized at an atomic scale. The relation of this model to other approaches of analyzing Mossbauer spectra with a distribution of sites is discussed, as well as the difference between the present results on [CsCl]Fe1-xSi and earlier interpretations in the literature. This work reveals how a combination of Mossbauer experiments and ab initio calculations leads to a more reliable interpretation of Mossbauer spectra reflecting an infinite number of sites

Electronic stopping force of 12C, 28Si and 63Cu ions in HfO2 and SiO2 dielectric films

The stopping force of ions in matter is a basic physical concept that provides insight into the nature of ion-beam matter interactions. In applied research such as in nuclear analytical spectrometry the accuracy of stopping force data is crucial to the accuracy of analyses performed. The availability of ab initio calculations that can provide stopping force data with reasonable accuracy is a desirable development not only for ion beam analysis work and other applications that exploit the passage of energetic ions through matter, but also for fundamental ion-beam matter interaction studies. In this work stopping force measurements of 12C, 28Si and 63Cu ions through SiO2 and HfO2 dielectric films were carried out by time of flight spectrometry and the results are compared with semi-empirical calculations by Ziegler’s Stopping and Range of Ions in Matter (SRIM) code, and ab initio calculations by Grande and Schiewietz’s Convolution approximation for swift Particles (CasP) code. Indications are that in the 0.1–1.0 MeV/u projectile energy range, while SRIM performs quite well for lighter ions, in the case of intermediate to heavy projectiles CasP is on par with, and promises to describe stopping more accurately than SRIM, possibly due to the former’s incorporation of charge exchange effects into total stopping.financial support from the National Research Foundation (NRF) of South Africa and the International Atomic Energy agency (IAEA)

Simultaneous real-time x-ray diffraction spectroscopy, Rutherford backscattering spectrometry, and sheet resistance measurements to study thin film growth kinetics by Kissinger plots

When the Kissinger method is used to investigate thin film growth kinetics, activation energies obtained are often significantly higher than those of Arrhenius plots based on isothermal studies. The reason for the higher activation energies is related to the sensitivity of the Kissinger analysis to nucleation effects. In fact, this often undesirable effect opens the possibility of studying nucleation barriers in a semiquantitative way. Furthermore, we show that these nucleation effects can be filtered out by a more careful application of the Kissinger method, and activation energies that are consistent with Arrhenius plots are then obtained

On the nucleation of PdSi and NiSi2 during the ternary Ni(Pd)/Si(100) reaction

During the solid phase reaction of a Ni(Pd) alloy with Si(100), phase separation of binary Ni- and Pd-silicides occurs. The PdSi monosilicide nucleates at temperatures significantly below the widely accepted nucleation temperature of the binary system. The decrease in nucleation temperature originates from the presence of the isomorphous NiSi, lowering the interface energy for PdSi nucleation. Despite the mutual solubility of NiSi and PdSi, the two binaries coexist in a temperature window of 100 °C. Only above 700 °C a Ni1-xPdxSi solid solution is formed, which in turn postpones the NiSi2 formation to a higher temperature due to entropy of mixing. Our findings highlight the overall importance of the interface energy for nucleation in ternary systems. © 2013 AIP Publishing LLC.status: publishe

Simultaneous real-time x-ray diffraction spectroscopy, Rutherford backscattering spectrometry, and sheet resistance measurements to study thin film growth kinetics by Kissinger plots

When the Kissinger method is used to investigate thin film growth kinetics, activation energies obtained are often significantly higher than those of Arrhenius plots based on isothermal studies. The reason for the higher activation energies is related to the sensitivity of the Kissinger analysis to nucleation effects. In fact, this often undesirable effect opens the possibility of studying nucleation barriers in a semiquantitative way. Furthermore, we show that these nucleation effects can be filtered out by a more careful application of the Kissinger method, and activation energies that are consistent with Arrhenius plots are then obtained.status: publishe