“Clinic laboratory accreditation with ISO 15189:2007 in the European Union”: report of the VI European symposium on clinical laboratory and in vitro diagnostic industry

Accreditation and Quality Assurance -     

Cooperative motions in PVC studied by thermally stimulated currents: Comparison with A.C. dielectric derivative analysis

The thermally stimulated current–thermal sampling (TSC–TS) technique was used to study the broadened glass transition in conventional “atactic” poly(vinyl chloride), PVC. The activated parameters obtained from the TSC–TS data, mainly the apparent activation energy (E_a), characterize the breadth of glass transitions in a very sensitive way. These results are compared with those values of E_a obtained from the literature, using a recently proposed method of analyzing a.c. dielectric constants and their derivatives, over the temperature range of −100–130°C. Both techniques detect weak cooperative glass transition-like relaxations well below the main glass transition of ca. 80°C. As is the case with “atactic” PMMA, the data suggest that compositional heterogeneity related to a small fraction of predominantly isotactic sequences contribute to the broad glass transition extending ca. 60°C below the main glass transition in atactic PVC. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 913–918, 1998     

Mixed-metal cluster chemistry. 26 . Proclivity for “all-terminal” or “plane-of-bridging-carbonyls” ligand disposition in tungsten-triiridium clusters

Reaction of WH(CO)₃(η-C₅Me₅) with IrCl(CO)₂(4-H₂NC₆H₄Me) affords WIr₃(μ-CO)₃(CO)₈(η-C₅Me₅) in low yield. A structural study reveals a WIr₂-centred plane of bridging carbonyls, in contrast to the crystal structure of WIr₃(CO)₁₁(η-C₅H₅) (all-terminal carbonyl distribution). DFT calculations reveal an increasing proclivity to adopt an all-terminal CO disposition for clusters MIr₃(CO)₁₁(η-C₅H₅) in the gas phase on proceeding from M=Cr to Mo and then W, consistent with structural studies in the solid state for which the tungsten-containing cluster is the only all-terminal example. Increasing electron donation from the ligands in the tungsten system (either from phosphine substitution or cyclopentadienyl permethylation) suffices to impose a plane of bridging carbonyls in the ground state structure. ¹³C NMR fluxionality studies reveal that CO exchange mechanism(s) for WIr₃(CO)₁₁(η-C₅H₅) and the related tetrahedral cluster W₂Ir₂(CO)₁₀(η-C₅H₅)₂ are very fast and involve all carbonyls on the clusters. DFT calculations on MIr₃(CO)₁₁(η-C₅H₅) (M=Cr, Mo) substantiate a ‘merry-go-round’ mechanism for carbonyl scrambling in these systems, a result which is consistent with the scrambling behaviour seen in the NMR fluxionality studies on the W-containing congener.     

Effect of the electrodeposition potential on the photoelectroactivity of the SnS/Sb2S3 thin films

Journal of Solid State Electrochemistry - The present work outlines a simple and novel approach to obtain nanostructured and heterostructured SnS/Sb2S3 thin films. This material showed enhanced...     

Determination of levofloxacin in pharmaceutical formulations and urine at reduced graphene oxide and carbon nanotube-modified electrodes

Journal of Solid State Electrochemistry - In this paper, we compare reduced graphene oxide (RGO) electrode with multi-walled carbon nanotubes (MWCNT) as modifiers for the sensitive detection of...     

Photochemistry in Real Space: Batho- and Hypsochromism in the Water Dimer

The development of chemical intuition in photochemistry faces several difficulties that result from the inadequacy of the one-particle picture, the Born–Oppenheimer approximation, and other basic ideas used to build models. It is shown herein how real-space approaches can be efficiently used to gain valuable insights in photochemistry through a simple example of red and blue shift effects: the double hypso- and bathochromic shifts in the low-lying valence excited states of (H₂O)₂. It is demonstrated that 1) the use of these techniques allows the perturbative language used in the theory of intermolecular interactions, even in the strongly interacting short-range regime, to be maintained; 2) one and only one molecule is photoexcited in each of the addressed excited states and 3) the electrostatic interaction between the in-the-cluster molecular dipoles provides a fairly intuitive rationalisation of the observed batho- and hypsochromism. The methods exploited and illustrated herein are able to maintain the individuality and properties of the interacting entities in a molecular aggregate, and thereby they allow chemical intuition in general states, at any geometry and using a broad variety of electronic structure methods to be kept and built.     

Influence of some sugars on the thermal,rheological and morphological properties of “pinhão” starch

When starch is incorporated into puddings, desserts, and other foods containing sugar as the main ingredient, it will have an effect on the gelatinisation temperature and pasting properties. Many studies have been undertaken to investigate the effect of several sugars in foods and starches, as well as their physicochemical and functional properties. These studies have verified the significant influence on these properties, which are dependent on the nature of sugar and of starch. In this study, pinhão starch was extracted in the laboratory and was added, stirring for 60 min, to solutions at 1 % of each of the following sugars: fructose, glucose, sucrose, and 0.5 % fructose and 0.5 % glucose. After this time, the slurry was filtered, washed, dried at 40 °C and kept in a desiccator over anhydrous calcium chloride until constant mass. The effects of each sugar on the surface of the pinhão starch granules were observed using the non-contact method of atomic force microscopy, whereby it was possible to verify a decrease in the average diameter and an increase in the average roughness. X-ray diffractometry made it possible to evaluate the degree of relative crystallinity, which was proportional to the roughness and inversely proportional to the gelatinisation enthalpy (ΔH), which was studied by differential scanning calorimetry.     

1H NMR studies of binary and ternary dapsone supramolecular complexes with different drug carriers: EPC liposome,SBE‐β‐CD and β‐CD

Binary and ternary systems composed of dapsone, sulfobutylether‐β‐cyclodextrin (SBE‐β‐CD), β‐CD and egg phosphatidylcholine (EPC) were evaluated using 1D ROESY, saturation transfer difference NMR and diffusion experiments (DOSY) revealing the binary complexes Dap/β‐CD (K_a 1396 l mol^?1), Dap/SBE‐β‐CD (K_a 246 l mol^?1), Dap/EPC (K_a 84 l mol^?1) and the ternary complex Dap/β‐CD/EPC (K_a 18 l mol^?1) in which dapsone is more soluble. Copyright © 2014 John Wiley & Sons, Ltd.     

Hybrid Plasmonic–Aerogel Materials as Optical Superheaters with Engineered Resonances

Solar radiation is a versatile source of energy, convertible to different forms of power. A direct path to exploit it is the generation of heat, for applications including passive building heating, but it can also drive secondary energy-conversion steps. We present a novel concept for a hybrid material which is both strongly photo-absorbing and with superior characteristics for the insulation of heat. The combination of that two properties is rather unique, and make this material an optical superheater. To realize such a material, we are combining plasmonic nanoheaters with alumina aerogel. The aerogel has the double function of providing structural support for plasmonic nanocrystals, which serve as nanoheaters, and reducing the diffusion rate of the heat generated by them, resulting in large local temperature increases under a relatively low radiation intensity. This work includes theoretical discussion on the physical mechanisms impacting the system's balanced thermal equilibrium.     

A dithienylethene-tethered beta-cyclodextrin dimer as a photoswitchable host

The binding of TSPP by a dithienylethene-tethered beta-cyclodextrin dimer can be altered reversibly by irradiation with light.