Extended investigation of LiOH–LiBr binary system for high-temperature thermal energy storage applications

Journal of Thermal Analysis and Calorimetry - LiOH–LiBr binary system is thoroughly investigated by means of DSC and XRD experimental analysis. Observed discrepancies compared to previous...     

Determination of different forms of aminothiols in red blood cells without washing erythrocytes

Detection and quantification of different aminothiols forms (reduced and total) in biological fluids are important for the investigation of oxidative stress‐related diseases and cell homeostasis study. The aim of this study was to optimize a HPLC method in order to determine both reduced and total thiol forms in red blood cells (RBC) at low temperature without washing erythrocytes. Analytical recoveries for total and reduced thiols were 91.6–98.5 and 94.9–98.2% respectively. The relative standard deviations intra‐assay for total and reduced thiols were 1.14–3.64 and 0.83–2.3% respectively and the relative standard deviations inter‐assay for total and reduced thiols were 1.12–3.54 and 0.84–2.03%, respectively. This method allows specific analysis of the aminothiol state inside the RBC, as a model of intracellular metabolism functioning. Copyright © 2013 John Wiley & Sons, Ltd.     

Simulating harmonic oscillator and electrical circuits: a didactical proposal

A Mathematica ^? package is described that uses simulations and animations to illustrate key concepts in harmonic oscillation and electric circuits for students not majoring in physics or mathematics. Students are not required to know the Mathematica^? environment: a user-friendly interface with buttons functionalities and on-line help allows immediate use of the application. Students who are familiar with the programming language have the opportunity to see the set up code that is used, and they can eventually customize it. The goal of the application presented is to enhance student insight, in the spirit of learning by experimentation.     

Synthesis and Base Pairing Properties of 1′,5′‐Anhydro‐L‐Hexitol Nucleic Acids (L‐HNA)

Oligonucleotides composed of 1′,5′‐anhydro‐arabino‐hexitol nucleosides belonging to the L series (L ‐HNA) were prepared and preliminarily studied as a novel potential base‐pairing system. Synthesis of enantiopure L ‐hexitol nucleotide monomers equipped with a 2′‐(N⁶‐benzoyladenin‐9‐yl) or a 2′‐(thymin‐1‐yl) moiety was carried out by a de novo approach based on a domino reaction as key step. The L oligonucleotide analogues were evaluated in duplex formation with natural complements as well as with unnatural sugar‐modified oligonucleotides. In many cases stable homo‐ and heterochiral associations were found. Besides T_m measurements, detection of heterochiral complexes was unambiguously confirmed by LC‐MS studies. Interestingly, circular dichroism measurements of the most stable duplexes suggested that L ‐HNA form left‐handed helices with both D and L oligonucleotides.     

Measurement of PAHs in environmental matrices: results from an interlaboratory comparison on the different steps of the measurement procedure

Proficiency testing (PT) is becoming a feature of laboratory accreditation and the PT results are used to assess the technical competence of the participating laboratories. ISPRA (former APAT) plays an important role in supporting the Italian laboratories belonging to the network of the Regional Environmental Agencies to improve the quality of their analytical measurements. As a consequence, ISPRA organized an interlaboratory comparison to assess the performance of the laboratories on PAH measurement procedure. The interlaboratory comparison was drawn separating the different steps of the measurement (from the extraction to the instrumental measurement). Two matrix reference materials: (1) a polluted soil and (2) an extract reference material of the same polluted soil and a “blind” PAH mixture standard stock solution were distributed to 59 Italian laboratories. The results of interlaboratory comparison showed a significant dispersion of the PAH measurements that masks the effects of the different extraction and cleanup procedures used, but it is consistent with the results of other European interlaboratory comparisons.     

Structural, spectroscopic and magnetic investigation of the LiFe1−xMnxPO4 (x=0-0.18) solid solution

Different solid state and sol-gel preparations of undoped and Mn substituted cathode material LiFePO₄ are investigated. Li₃PO₄, Fe₂P₂O₇ and Li₄P₂O₇ are detected and quantified by XRPD only in solid state synthesis. In addition, micro-Raman spectra reveal low amount of different iron oxides clusters. EPR data, combined with the results of magnetization measurements, evidence signals from Fe³⁺ ions in maghemite nanoclusters, and in Li₃Fe₂(PO₄)₃. The sol-gel synthesis, showing the lowest amount of impurity phases, seems the most suitable to obtain a promising cathode material. The structural refinement gives new insights into the cation distribution of the Mn doped triphylite structure: (i) about 85% of Mn²⁺ ions substitutes Fe²⁺, the remaining 15% being located on the Li site, thus suggesting a structural disorder also confirmed by EPR and micro-Raman results; (ii) Mn ions on the Li site are responsible for the observed slight cell volume expansion.     

Ortho-spirocarbonates and ortho-spirothiocarbonates: synthesis, functionalization and coupling

This paper describes a new efficient synthesis of 2,2′-spirobi-(1,3-benzoxathiole) (1), 2,2′-spirobi-(1,3-benzodithiole) (2) and 2,2′-spirobi-(1,3-benzodioxole) (3). Compound 3 has been functionalized by means of metallation reaction followed by electrophilic quenching to give carboxylic acids, aldehydes and alcohols. Furthermore compound 3 was subjected to homo-coupling and its dimeric structure was determined by XRD analysis.     

Regularization and preconditioning of KKT systems arising in nonnegative least‐squares problems

A regularized Newton‐like method for solving nonnegative least‐squares problems is proposed and analysed in this paper. A preconditioner for KKT systems arising in the method is introduced and spectral properties of the preconditioned matrix are analysed. A bound on the condition number of the preconditioned matrix is provided. The bound does not depend on the interior‐point scaling matrix. Preliminary computational results confirm the effectiveness of the preconditioner and fast convergence of the iterative method established by the analysis performed in this paper. Copyright © 2008 John Wiley & Sons, Ltd.