Improved Time-Resolved Measurements of Inorganic Ions in Particulate Matter by PILS-IC Integrated with a Sample Pre-Concentration System

A particle-into-liquid sampler coupled with ion chromatograph (PILS-IC) for the on-line measurement of inorganic ions has been modified by the insertion of two ion-exchange pre-concentration cartridges that enrich the sample during the period of the IC analysis. The limits of detection of the modified instrument were 10-15 times lower and the time coverage 24 times higher (from 2 to 48 min per hour) than those of the original PILS-IC setup. The instrumental performance in terms of recovery and break-through volume from the cartridges was satisfactory. The modified PILS-IC was operated in comparison with a diffusion denuder line and with a high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS) during a short intensive measurement period organized in the framework of the European Monitoring and Evaluation Programme (EMEP), a co-operative program for monitoring and evaluation of the long-range transmission of the air pollutants in Europe. The instrument showed a quantitative response in agreement with the results of the diffusion lines, and an ability to trace fine concentration variations not so different from the performance of the much more complex HR-TOF-AMS. From the time patterns of the ion concentrations measured by the modified PILS-IC, it was possible to obtain useful information about the variations in the air quality and in the strength of the particulate matter sources.

Copyright 2015 American Association for Aerosol Research     

Microtiter spectrophotometric biofilm production assay analyzed with metrological methods and uncertainty evaluation

The microbial biofilm is a structure often developed by microorganisms when performing their harmful effects, both in the medical and industrial fields. Therefore, methods allowing identification and analysis of the biofilm play a fundamental role in determining the kind of intervention needed to avoid these effects. The microtiter spectrophotometric assay is recognized as the gold standard method to quantify a biofilm and to analyze the anti-biofilm activity of various substances. The aim of the present work is to validate this method through an uncertainty evaluation, covering eight different microbial species.     

Chiral Resolution and Pharmacological Characterization of the Enantiomers of the Hsp90 Inhibitor 2‐Amino‐7‐[4‐fluoro‐2‐(3‐pyridyl)phenyl]‐4‐methyl‐7,8‐dihydro‐6H‐quinazolin‐5‐one Oxime

Heat‐shock protein 90 (Hsp90) is a molecular chaperone involved in the stabilization of key oncogenic signaling proteins, and therefore, inhibition of Hsp90 represents a new strategy in cancer therapy. 2‐Amino‐7‐[4‐fluoro‐2‐(3‐pyridyl)phenyl]‐4‐methyl‐7,8‐dihydro‐6H‐quinazolin‐5‐one oxime is a racemic Hsp90 inhibitor that targets the N‐terminal adenosine triphosphatase site. We developed a method to resolve the enantiomers and evaluated their inhibitory activity on Hsp90 and the consequent antitumor effects. The (S) stereoisomer emerged as a potent Hsp90 inhibitor in biochemical and cellular assays. In addition, this enantiomer exhibited high oral bioavailability in mice and excellent antitumor activity in two different human cancer xenograft models.     

Thermomechanical and barrier properties of UV‐cured epoxy/O‐montmorillonite nanocomposites

Mixtures of an epoxy resin and organophilic montmorillonites were subjected to ultraviolet (UV)‐induced photopolymerization. Two types of commercially available nanoclays, namely Cloisite 30B and Cloisite Na⁺, were modified through interaction with organic compatibilizers (dodecylsuccinic anhydride, octadecylamine, octadecyl alcohol, and octadecanoic acid). The modified nanoclays, dispersed in the liquid epoxy resin at 5 wt%, were photopolymerized to get nanocomposite films. The kinetics of the photopolymerization was evaluated by means of real‐time Fourier transform infrared spectroscopy. The modified nanoclays and their nanocomposites were characterized through X‐ray diffractometry; transmission electron microscopy showed the presence of intercalated and partially exfoliated morphologies in the nanocomposites. Thermogravimetric and dynamic‐mechanical analyses showed an increase of the thermal properties and an increase of the glass transition temperatures of the nanocomposites compared with that of the neat UV‐cured resin. Finally, the oxygen barrier properties of nanocomposite films, coated on a polyethyleneterephtalate substrate, were evaluated; the decrease of permeability was correlated with the degree of exfoliation of the nanocomposites. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

Direct determination of rare earth elements at the subpicogram per gram level in antarctic ice by ICP-SFMS using a desolvation system

A method, based on inductively coupled plasma sector field mass spectrometry coupled with a microflow nebulizer and a desolvation system, has been developed for the direct determination of rare earth elements (REE) (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) down to the subpicogram per gram level (1 pg/g = 10(-12) g g(-1)) in approximately 1 mL of molten Antarctic ice. Contamination problems were carefully taken into account by adopting ultraclean procedures during the sample pretreatment phases. The use of a desolvation system for sample introduction during the analysis greatly reduced spectral interferences from oxide formation; the residual interfering contributions were calculated and subtracted whenever necessary. A matched calibration curve method was used for the quantification of the analytes. Instrumental detection limits ranged from 0.001 pg/g for Ho, Tm, and Lu to 0.03 pg/g for Gd. The precision, in terms of relative standard deviation on 10 replicates, ranged from 2% for La, Ce, Pr, and Lu, up to 10% for Er, Tm, and Yb. This methodology allowed the direct determination of REE in a 1-mL sample of ancient Antarctic ice with concentration ranges between 0.006 and 0.4 pg/g for Tm and 0.9-60 pg/g for Ce.     

Imaging the Electric‐Field Distribution in Organic Devices by Confocal Electroreflectance Microscopy

Space resolved Stark spectroscopy is introduced as a non invasive optical technique for imaging electric field distribution in organic semiconductors. Stark spectroscopy relies on the electric field induced change in the absorption/reflection. It is shown that local monitoring of Stark shift with confocal spatial resolution provides quantitative information on the strength of the local field as well as charge distribution within the transport channel.     

Preparation and Characterization of Nanostructured TiO2/Epoxy Polymeric Films

Summary: Titania‐containing coatings were prepared by cationic photopolymerization of an epoxy resin either by dispersion of preformed TiO₂ nanoparticles or by their in‐situ generation through a sol‐gel dual‐cure process. The kinetics of photopolymerization was evaluated by real‐time FT‐IR, studying the effect of the TiO₂ concentration. The properties of cured films were investigated, showing an increase of hydrophilicity on the surface of the coatings with increasing TiO₂ content. TEM analysis demonstrated that it is possible to achieve a significantly better control of the dispersion of the inorganic particles within the organic matrix by in‐situ generation of TiO₂, thus completely avoiding macroscopic phase separation and obtaining homogeneous, transparent coatings.

Bright‐field TEM micrograph for TIP20 dual‐cured film.     

Impact behaviour of A356 alloy for low-pressure die casting automotive wheels

Instrumented impact strength tests have been carried out on KV sub-size Charpy samples drawn from A356 aluminium alloy 17-in. wheels, produced by a low-pressure die casting. The wheels show different geometry and thermal treatment. In this paper, the effects of microstructure and defects on the impact properties are studied. The results indicate that the impact energy is lower in as-cast wheel than in T6 heat-treated wheels. A finer microstructure always corresponds to higher impact strength, while a direct correlation between the resistance to crack propagation values and secondary dendrite arm spacing (SDAS) exists. Casting defects, revealed by means of X-ray and density measurements techniques, become critical when concentrated around the V-notch, where they reduce the load bearing area of Charpy specimens. The fracture profile and surface of Charpy specimens have been investigated revealing how the crack crosses the interdendritic eutectic region where a significant fraction of cracked eutectic silicon and intermetallic particles is found.Numerical simulations have been performed to study the filling and solidification behaviour of the alloy of the wheels analysed, in order to predict the final microstructure and shrinkage formation. Solidification times, estimated by means of SDAS measurements and calculated with a numerical simulation approach, show a good correspondence. Critical areas, as concern hot spots and shrinkage porosities, are generally revealed in the zone of the wheels between the spoke and the rim, as well as in the rim area.