A Titration Microcalorimetric Study of the Effects of Halide Counterions on Vesicle-Forming Aggregation in Aqueous Solution of Branched-Chain Alkylpyridinium Surfactants

Titration microcalorimetry is used to study the influences of iodide, bromide, and chloride counterions on the aggregation of vesicle-forming 1-methyl-4-(2-pentylheptyl)pyridinium halide surfactants. Formation of vesicles by these surfactants was characterised using transmission electron microscopy. When the counterion is changed at 303 K through the series iodide, bromide, to chloride, the critical vesicular concentration (cvc) increases and the enthalpy of vesicle formation changes from exo- to endothermic. With increase in temperature to 333 K, vesicle formation becomes strongly exothermic. Increasing the temperature leads to a decrease in enthalpy and entropy of vesicle formation for all three surfactants. However the standard Gibbs energy for vesicle formation is, perhaps surprisingly, largely unaffected by an increase in temperature, as a consequence of a compensating change in both standard entropy and standard enthalpy of vesicle formation. Interestingly, standard isobaric heat capacities of vesicle formation are negative, large in magnitude but not strikingly dependent on the counterion. We conclude that the driving force for vesicle formation can be understood in terms of overlap of the thermally labile hydrophobic hydration shells of the alkyl chains. Copyright 2000 Academic Press.     

Dirac's aether in relativistic quantum mechanics

The introduction by Dirac of a new aether model based on a stochastic covariant distribution of subquantum motions (corresponding to a vacuum state alive with fluctuations and randomness) is discussed with respect to the present experimental and theoretical discussion of nonlocality in EPR situations. It is shown (1) that one can deduce the de Broglie waves as real collective Markov processes on the top of Dirac's aether; (2) that the quantum potential associated with this aether's modification, by the presence of EPR photon pairs, yields a relativistic causal action at a distance which interprets the superluminal correlations recently established by Aspect et al.; (3) that the existence of the Einstein-de Broglie photon model (deduced from Dirac's aether) implies experimental predictions which conflict with the Copenhagen interpretation in certain specific testable interference experiments.     

Effects of Adsorbed Polyaniline on Redox Process on MoO3 Surface

The effects exhibited by adsorbed conducting polyaniline on the redox process on a molybdenum oxide surface were studied. Thermogravimetric results indicate a 4% polyaniline deposition. Cyclic voltammograms of the adsorbed polymer on MoO3 show that polyaniline exerts remarkable effects on the molybdenum blue oxidation-reduction process, with oxidation and reduction potentials of 0.33 and 0.18 V, respectively. This effect strongly enhances the electrode response, and can be used as an important tool in qualitative and/or quantitative determinations of molybdenum in solution as well as in any substrate. Copyright 1999 Academic Press.     

Synthesis, characterisation and thermal behaviour of solid state compounds of 4-methylbenzylidenepyruvate with some bivalent metal ions

Solid state M-4-Me-BP compounds, where M stands for bivalent Mn, Fe, Co, Ni, Cu, Zn, Pb and 4-Me-BP is 4-methylbenzylidenepyruvate, have been synthesized. Simultaneous thermogravimetry-differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry, infrared spectroscopy, elemental analysis, and complexometry were used to characterise and to study the thermal behaviour of these compounds. The results led to information about the composition, dehydration, thermal stability and thermal decomposition of the isolated complexes.     

The role of quality management system in the monitoring and continuous improvement of GMP-regulated short-lived radiopharmaceutical manufacture

The last decade has seen extraordinary growth in the clinical use of Positron Emission Tomography (PET), an in vivo molecular imaging modality widely used in oncology that requires the use of radiopharmaceuticals labeled with short-lived radionuclides. These medicinal products have found widespread application in Nuclear Medicine departments equipped with PET scanners. Due to the great increase in radiopharmaceutical demand, their production has been centralized and moved to industrial manufacturing sites in which Good Manufacturing Practice (GMP) principles and guidelines for medicinal products are to be applied. The production of PET radiopharmaceuticals features particular aspects such as the use of the lot before the completion of all tests, the multiplicity of batches produced per single day and the absence of product stock due to radionuclide short half-life. In this context, the application of quality principles to all stages of the process and the implementation of a quality management system (QMS) are of primary importance. This paper reports on the development of a QMS applied to a GMP manufacturing site of an in vivo PET diagnostic product, and on how its application can describe the performance of the site. Data were collected over a 6-year period (2008–2013) and demonstrate the ability of Key Performance Indicators, strictly related to the structure and organization of the QMS, and quality tools (data analysis, internal audit, etc.) to monitor process performance in terms of effectiveness, efficacy and stability.     

Implementation of Good Manufacturing Practice in small-volume production of [18F]FDG: a case report of performance measurements

Positron Emission Tomography has become increasingly relevant in clinical practice for diagnostic purposes. A major concern regarding radiopharmaceuticals in general is how quality requirements can be guaranteed in nuclear medicine departments or in cases where marketing authorization has been granted. This article focuses on issues related to the small-volume preparation of radiopharmaceuticals by a Research Institute after Good Manufacturing Practice implementation.