SAXS/DSC/WAXD study of TiO2 nanoparticles and the effect of γ-radiation on nanopolymer electrolyte

Nanostructured polymer electrolytes are very attractive materials for components of batteries and opto-electronic devices. (PEO)₈ZnCl₂ polymer electrolytes and nanocomposites were prepared using Poly(ethylene oxide) (PEO) γ-irradiated with a selected dose of 529 kGy and with an addition of 10% of TiO₂ nanograins. The influence of the added nanosize TiO₂ grains on the polymer electrolytes and the effect of the γ-radiation from a Co-60 source were studied by small-angle X-ray scattering (SAXS) simultaneously recorded with differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) at the synchrotron ELETTRA. Infrared (IR) and impedance spectroscopy (IS) were also performed [1]. It was shown by previously performed IS that the room temperature conductivity of the nanocomposite polymer electrolyte increased more than two times above 65 °C, relative to pure composites of PEO and salts. We observed all changes between 20 °C and 100 °C for treated and as prepared polymer electrolyte in the SAXS, DSC and WAXD spectra and especially during the phase transition to the super-ionic phase at 65 °C [2] and [3]. The SAXS/DSC measurements yielded insight into the temperature-dependent changes of the grains of the electrolyte as well as into the differences due to different heating and cooling rates. The crystal structure and the melting and crystallization temperatures of the nanosize grains were revealed by the simultaneous WAXD measurements.     

Low-level occupational 14C contamination--results from a pilot study

This paper presents a pilot study in which specific activities of 14C in hair and urine from 11 radiation workers handling 14C-containing substances have been measured using accelerator mass spectrometry. Varying degrees of contamination were revealed: up to 63% excess in hair and 400% excess in urine. Although the 14C excess reported in this study would result in low effective doses, it would be of interest to monitor the situation at other workplaces with potentially higher risks of contamination. Simultaneous measurements of 14C in hair and urine with additional random measurements of 14C in faeces and exhaled air could provide a means of improving dose estimates for workers handling different types of 14C-containing substances.     

A pumping lemma for random permitting context languages

Random context grammars belong to the class of context-free grammars with regulated rewriting. Their productions depend on context that may be randomly distributed in a sentential form. Context is classified as either permitting or forbidding, where permitting context enables the application of a production and forbidding context inhibits it. For random context languages of finite index a generalization of the well-known pumping lemma for context-free languages has been proven. We drop the finite index restriction and concentrate on non-erasing grammars that use permitting context only. We prove a pumping lemma for their languages that generalizes and refines the existing one, and show that these grammars are strictly weaker than the non-erasing random context grammars.     

The role of electrical current mode in calcium carbonate deposition on conductive carbon nanofiber–epoxy coating

Calcium carbonate is one of the most common scaling minerals. In this paper we have used different electrical current modes (direct current [DC], pulsed DC, and alternating current [AC]) to control the amount, morphology, and distribution of calcium carbonate deposit on electroconductive epoxy/carbon nanofiber (CNF) coating. The effect of different current modes on surface scaling was visualized using scanning electron microscopy. It has been shown that both AC and DC anodic polarization limited scale deposition on epoxy/CNF coated surfaces, although the mechanisms of scale inhibition during AC and DC polarization were different. DC polarization of the coating at +2 V resulted in the smallest scale buildup without leading to coating degradation, while DC polarization at potentials as high as +5 V caused the coating to degrade. Interestingly, application of pulsed DC with high pulse frequency (50 Hz) inhibited the degradation. The type of current applied affected also the morphology of the precipitate at the cathode. The results presented in this work show, for the first time, how different modes of electrical current applied to electroconductive composite coatings can be used to control the morphology and distribution of calcium carbonate scale, and how the organic coating degradation at high polarization potentials can be avoided.     

The influence of discharge time on post-partial discharge gassing of zinc powder

Gas evolution in primary alkaline cells depends on discharge time. This dependence can be so strong that acceptable volumes of gas are evolved in cells when discharged over relatively long periods, whereas shorter times may lead to gassing beyond the limits of the cell design. The dependency of gassing on discharge time was investigated for a number of commercial cells and for different zinc-alloy powders. An indication of a relation between certain alloying elements and the gas evolution at short discharge times was found. The most important result of the investigations, however, was the development of a modified zinc powder production process which leads to zinc powders with reduced gas evolution rates for both short and long discharge times.     

Molecular Imaging of Apoptosis: The Case of Caspase-3 Radiotracers

The molecular imaging of apoptosis remains an important method for the diagnosis and monitoring of the progression of certain diseases and the evaluation of the efficacy of anticancer apoptosis-inducing therapies. Among the multiple biomarkers involved in apoptosis, activated caspase-3 is an attractive target, as it is the most abundant of the executioner caspases. Nuclear imaging is a good candidate, as it combines a high depth of tissue penetration and high sensitivity, features necessary to detect small changes in levels of apoptosis. However, designing a caspase-3 radiotracer comes with challenges, such as selectivity, cell permeability and transient caspase-3 activation. In this review, we discuss the different caspase-3 radiotracers for the imaging of apoptosis together with the challenges of the translation of various apoptosis-imaging strategies in clinical trials.     

Symmetry and asymmetry of solutions in discrete variable structural optimization

In this paper symmetry and asymmetry of optimal solutions in symmetric structural optimization problems is investigated, based on the choice of variables. A group theory approach is used to define the symmetry of the structural problems in a general way. This approach allows the set of symmetric structures to be described and related to the entire search space of the problem. A relationship between the design variables and the likelihood of finding symmetric or asymmetric solutions to problems is established. It is shown that an optimal symmetric solution (if any) does not necessarily exist in the case of discrete variable problems, regardless of the size of the discrete, countable set from which variables can be chosen. Finally a number of examples illustrate these principles on simple truss structures with discrete topology and sizing variables.