Processing nanoparticles with A4F-SAXS for toxicological studies: Iron oxide in cell-based assays

Nanoparticles are not typically ready-to-use for in vitro cell culture assays. Prior to their use in assays, powder samples containing nanoparticles must be dispersed, de-agglomerated, fractionated by size, and characterized with respect to size and size distribution. For this purpose we report exemplarily on polyphosphate-stabilized iron oxide nanoparticles in aqueous suspension. Fractionation and online particle size analysis was performed in a time-saving procedure lasting 50 min by combining asymmetrical flow field-flow fractionation (A4F) and small-angle X-ray scattering (SAXS). Narrowly distributed nanoparticle fractions with radii of gyration (R(g)) from 7 to 21 nm were obtained from polydisperse samples. The A4F-SAXS combination is introduced for the preparation of well-characterized sample fractions originating from a highly polydisperse system as typically found in engineered nanoparticles. A4F-SAXS processed particles are ready-to-use for toxicological studies. The results of preliminary tests of the effects of fractionated iron oxide nanoparticles with a R(g) of 15 nm on a human colon model cell line are reported.     

1H, 13C and 15N NMR spectral assignments of adenosine derivatives with different amino substituents at C6-position

The complete (1)H, (13)C and (15)N NMR signals assignment of adenosine derivatives differently substituted at C(6)-position was achieved using one- and two-dimensional experiments (gs-COSY, gs-NOESY, gs-HSQC and gs-HMBC).     

Synthesis of enantiomerically pure (R)-and (S)-1-benzoyloxypropane-2,3-diol and revision of the stereochemical outcome of the Candida antarctica lipase-catalyzed benzoylation of glycerol

Enantiomerically pure (R)- and (S)-1-benzoyloxypropane-2,3-diol have been prepared from (S)-(+)-2,2-dimethyl-1,3-dioxolane-4-methanol and used as reference compounds to correct the reported stereochemical outcome of the Candida antarctica lipase (CAL)-catalyzed benzoylation of glycerol.     

Modelling the evolution of credit spreads using the Cox process within the HJM framework: A CDS option pricing model

In this paper a simulation approach for defaultable yield curves is developed within the Heath et al. (1992) framework. The default event is modelled using the Cox process where the stochastic intensity represents the credit spread. The forward credit spread volatility function is affected by the entire credit spread term structure. The paper provides the defaultable bond and credit default swap option price in a probability setting equipped with a subfiltration structure. The Euler–Maruyama stochastic integral approximation and the Monte Carlo method are applied to develop a numerical scheme for pricing. Finally, the antithetic variable technique is used to reduce the variance of credit default swap option prices.     

Synthesis of Differently Protected 1‐C‐Methyl‐Ribofuranoses Intermediates for the Preparation of Biologically Active 1′‐C‐Methyl‐Ribonucleosides

Starting from D‐ribose, differently protected 1‐C‐methyl‐D‐ribofuranoses have been prepared as intermediates for the synthesis of variously modified 1′‐C‐methyl‐ribonucleosides, a class of compounds potentially endowed with interesting biological activity.     

Release and speciation of uranium in low-ionic-strength groundwaters at an abandoned uranium mine in Val Vedello (Orobic Alp—Italy) by adsorptive cathodic stripping voltammetry

Adsorptive cathodic stripping voltammetry (AdCSV) with HDME and a chloranilic acid ligand was used in the trace analysis of uranyl ions at pH?=?2 in low-ionic-strength groundwaters around mining areas. Upon optimization, the limit of detection around 0.10?µg?L^?1 was found with linearity up to 10?µg?L^?1. In the abandoned mining area of Val Vedello (Orobic Alps, Italy), measured uranium concentrations in water ranged from 0.3?µg?L^?1 above the uranium mineralization levels to 145?µg?L^?1 in groundwaters percolating from mine galleries. Such uranium concentrations are related to natural weathering effects of CO₂ and/or hydrogen carbonate ion on uranium mineralizations under oxic conditions. A marked seasonal dependence was then found, in agreement with literature data on a pre-operational survey dating back to 1980–1981. No significant chemical impact of the abandoned mining activity on groundwater quality could be found. Accordingly, no significant increase in contaminants derived from the heat-burn of explosives, such as chloride and nitrate, in groundwaters from mine galleries was found.     

Internal quality control as a tool for planning a robustness study regarding a multiresidue method for pesticides found in olive oil

The implementation of the internal quality assurance program allows for demonstration of the performance characteristics of a method, as well as the avoidance of erroneous results. There is increasing concern in testing laboratories to ensure that the analytical process remains stable, giving reliable results under statistical control. Robustness is tested by introducing variations in experimental conditions and examining the effects on the results. The European document SANCO/12495/2011, “Method validation and quality control procedures for pesticide residue analysis in food and feed”, defines robustness as a parameter that can be derived from ongoing method verification. Internal quality control tools, such as the recovery control chart, were employed in this study to enhance the stability of the recovery rates and to investigate the experimental conditions that have a major influence on the quantification of recovery rates. The method investigated in this study permitted us to investigate eighteen pesticides in olive oil by using a gas chromatography–mass spectrometry technique. This method has been accredited to ISO/IEC 17025:2005 standards and was applied for 1 year in routine conditions for pesticide residues at the Italian National Reference Laboratory. The recovery control chart has showed that all recovery rates for 1 year were close to the maximum limit (120 %) of recovery performance criteria. Consequently, a “positive” bias has affected all data over longer periods of time. A robustness test was planned in order to investigate the grounds that most influenced the variability of the results. The robustness test involved the following three parameters: solvent used to dissolve the final extract, internal standards, and type of olive oil.     

Anion Recognition by Uranyl–Salophen Derivatives as Probed by Infrared Multiple Photon Dissociation Spectroscopy and Ab Initio Modeling

The vibrational features and molecular structures of complexes formed by a series of uranyl–salophen receptors with simple anions, such as Cl^?, H^?, and HCOO^?, have been investigated in the gas phase. Spectra of the anionic complexes were studied in the $\tilde \nu $ =800–1800 cm^?1 range by mass‐selective infrared multiple photon dissociation (IRMPD) spectroscopy with a continuously tunable free‐electron laser. The gas‐phase decarboxylation of the formate adducts produces uranyl–salophen monohydride anions, which have been characterized for the first time and reveal a strong U?H bond, the nature of which has been elucidated theoretically. The spectra are in excellent agreement with the results obtained from high‐quality ab initio calculations, which provided the structure and binding features of the anion–receptor complexes.     

Spherical aggregates obtained from N-carboxymethylation and acetylation of chitosan

Chitosan is a biopolymer with great industrial potential. However, solubility in aqueous solutions limits some applications. In this paper, the N-carboxymethylation (CM) of chitosan generated five derivatives namely, N-carboxymethylchitosan (NCMC) 1, NCMC2, NCMC3, NCMC4, and NCMC5, from 10.1% to 80% of CM. Afterwards, a new NCMC6 (∼60% of CM) was acetylated to produce the NCMCAc derivate. The modifications were confirmed by ¹³C nuclear magnetic resonance. A globular conformation to NCMC derivatives was confirmed by association of static and dynamic light scattering in which the form factor (ρ) is ∼1.3 in phosphate buffer (pH 7.4). The NCMCAc showed a ρ of 0.75, which is characteristic of dense spheres. Topographical analyses were performed by atomic force microscopy images in which dense spheres were observed. The critical aggregation concentration (CAC) was determined using pyrene as a hydrophobic fluorescent probe. For NCMC1–6 and NCMCAc, a CAC of 1.0 and 0.1 mg mL⁻¹ were, respectively, observed. NCMC1–6 and NCMCAc showed a globular and dense spherical conformation, respectively.     

Effects of natural convection on thermal explosion in a closed vessel

A new way of ascertaining whether or not a reacting mixture will explode uses just three timescales: that for chemical reaction to heat up the fluid containing the reactants and products, the timescale for heat conduction out of the reactor, and the timescale for natural convection in the fluid. This approach is developed for an nth order chemical reaction, A --> B occurring exothermically in a spherical, batch reactor without significant consumption of A. The three timescales are expressed in terms of the physical and chemical parameters of the system. Numerical simulations are performed for laminar natural convection occurring; also, a theoretical relation is developed for turbulent flow. These theoretical and numerical results agree well with previous experimental measurements for the decomposition of azomethane in the gas phase. The new theory developed here is compared with Frank-Kamenetskii's classical criterion for explosion. This new treatment has the advantage of separating the two effects inhibiting explosion, viz. heat removal by thermal conduction and by natural convection. Also, the approach is easily generalised to more complex reactions and flow systems.