Orientated crystallization in drawn thermoplastic polyimide modified by carbon nanofibers

The solid state crystallization in drawn thermoplastic polyimide films is studied as a function of draw ratio (DR) under the effect of vapor grown carbon fiber nanoinclusions. The nucleating effect of the nanoinclusions coupled with the orientation effect of drawing generates a unique orientated layered lamellar structure, characteristic of smectic‐like mesophase. The degree of draw induced orientated crystallization increases with the content of nanoinclusions and with the DR, and is reflected in the mechanical behavior of the film. Generally, the Young's modulus and the yield point of the drawn crystalline films in the drawing direction are significantly higher compared with the noncrystalline counterparts. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers     

Rapid and Simultaneous Analysis of Xanthines and Polyphenols as Bitter Taste Markers in Bakery Products by FT-NIR Spectroscopy

The food industry has a direct interest into bitter-tasting substances either for the identification of negative off-flavors or for the monitoring of a desired organoleptic quality. A rapid technique, based on Fourier transform-near infrared (FT-NIR) spectroscopy and able to detect taste molecular markers in bakery commodities, was developed, focusing the attention on biscuits category. Xanthines (caffeine, theobromine, and theophylline) and polyphenols (catechins and epicathechins), considered as mainly responsible for the bitter-taste of coffee\cocoa\chocolate based products, were firstly checked using a confirmatory liquid chromatography (LC)-ESI\mass spectrometry (MS)-MS procedure after hot methanol–water extraction. Correspondent data were used for the calibration of the FT-NIR through PLS regression. Values of the standard errors of prediction (lower than 10 %) were comparable to the values of the standard errors of cross-validation. Coefficients of determination indicated a good predictive power in the calibration model (R ² xanthines?=?0.97, R ² polyphenols?=?0.96) and a satisfying discriminating power among different contents in the validation models (R ² xanthines?=?0.96, R ² polyphenols?=?0.96). A testing phase on the generated model was executed by a comparison of LC-MS and sensory panel data with FT-NIR responses recorded on unknown biscuits: differences between found and predicted levels were generally below 5 % and the best predictability was achievable in chocolate-based biscuits. This methodology is able to work directly on solid products, has the potential to be expanded on other categories of gustative molecular markers (like sugars) and can be conceived as applicable for a routine control of a standardized bitter taste quality in a real industrial production.     

Removal of neutrophil gelatinase‐associated lipocalin by extracorporeal therapies

Neutrophil gelatinase‐associated lipocalin (NGAL) protein is an early biomarker for acute kidney injury (AKI). It is unknown if extracorporeal therapies (EC) have an effect on circulating NGAL levels. This study was designed to describe the kinetics of NGAL molecule in different EC techniques and to evaluate NGAL clearance in different operational conditions. A mock hemofiltration (HF) and hemoperfusion (HP) setup was used. NGAL was added to the blood reservoir and then measured at 30‐minute intervals from arterial, venous, and ultrafiltrate (UF) lines. Removal kinetics and NGAL sieving coefficient were calculated. In our experiments, baseline NGAL concentration averaged 452 μg/L. There was a consistent downward trend throughout the experiment. NGAL concentration in the UF was between 80 and 90 μg/L, though it showed a slight increase in the second hour. The sieving coefficient of NGAL ranged from 0.2 to 0.4 during HF and it appeared to increase with time, suggesting an initial effect of membrane adsorption. HP proved clearly that there was adsorption of NGAL by the membrane and the point of saturation occured at approximately 60 minutes from the start of circulation. Our evaluation demonstrates that NGAL can be adsorbed and ultrafiltrated with polysulfone membranes. This should be taken into consideration when using NGAL as an AKI biomarker in patients undergoing EC circulation.     

DAQs-based wattmeters for high accuracy measurements. Comparison with the Italian power primary standard

This paper is focused on the use of data acquisition boards (DAQs) for the development of high accuracy PC-based instruments for the measurements of electrical power. The proposed systems are simple, portable and low cost because they are based on commercial data acquisition boards (DAQs) connected to a common personal computer. Data processing is carried out by a commercial software based on an interpolating windowed FFT. In the paper it is shown how the voltage can be sensed directly, thanks to the DAQ input range, thus avoiding expensive voltage dividers. The set up of the DAQs-based solutions is described and the evaluation of their metrological features is made by means of a comparison with the Italian power primary standard, which was built at INRIM with a complex solution and expensive with two high precision digital voltmeters.     

Magnetic resonance butterfly coils: Design and application for hyperpolarized C studies

Hyperpolarized ¹³C magnetic resonance spectroscopy in pig models enables cardiac metabolism assessment and provides a powerful tool for heart physiology studies, although the low molar concentration of derivate metabolites gives rise to technological limitations in terms of data quality. The design of dedicated coils capable of providing large field of view with high Signal-to-Noise Ratio (SNR) data is of fundamental importance.     

Renewable electricity production costs—A framework to assist policy-makers' decisions on price support

Despite recent progress, the production costs for renewable electricity remain above those for conventional power. Expectations of continuous reductions in production costs, typically underpin governments' policies for financial support. They often draw on the technology-focused versions of the Experience Curve model. This paper discusses how national-contextual factors also have a strong influence on production costs, such as geographic, infrastructural, institutional, and resource factors. As technologies mature, and as they reach significant levels of diffusion nationally, sustained increases in production costs might be recorded, due to these nationally contextual factors, poorly accounted for in policy-making decisions for price support. The paper suggests an analytical framework for a more comprehensive understanding of production costs. Based on this, it recommends that the evolution of specific cost levels and factors be monitored to locate ‘sources of changes’. The paper also suggests policy instruments that governments may use to facilitate cost decreases, whenever possible. The application of the framework is illustrated for the diffusion of wind power in Spain during the past three decades.     

The study of weak oscillatory flows in space experiments

The effects of residual accelerations have been studied by using three-dimensional modeling of the flow in a rectangular cell filled with a liquid, Pr=20, the walls of which were kept at different temperatures. The system was subjected to an acceleration field, which can be decomposed into two parts: a steady component and another one which varies slowly with time, the frequency is about f₀≈10⁻³ Hz. The convective heat transport and flow characteristics are discussed for different parameters of g-jitter. The high and low frequency modulation of a sinusoidal g-jitter is discussed. To capture many of the essential characteristics of buoyancy-induced convection a new approach is suggested, which was developed based on the observation of the trajectories of tracer particles. On the one hand, it is a typical way to record the flow in experiments. On the other hand, creating database of different types of trajectories gives the possibility to solve the inverse problem. The shape of the trajectory depends on the g-jitter parameters. It is shown that for slow convective motions the tracer particles perform loops along trajectory due to g-jitter with low frequencies, and the additional high frequencies only cause trembling of the shape of these loops. Taking the experimentally recorded trajectories of tracer particles and comparing with those in the database, one can draw a conclusion about the amplitude and direction of the resulting gravity vector during the experiment.     

Melting behavior,crystallization kinetics and morphology of random copolyesters of poly(2‐hydroxyethoxybenzoate) with ε‐caprolactone

The melting behavior after isothermal crystallization and the crystallization kinetics of random poly(2‐hydroxyethoxybenzoate/ε‐caprolactone) copolymers rich in 2hydroxyethoxybenzoate units were investigated by means of differential scanning calorimetry and hot‐stage optical microscopy. The observed multiple endotherms, which are commonly displayed by polyesters, were found to be influenced both by crystallization temperature and composition. By applying the Hoffman‐Weeks method to the melting temperatures of isothermally crystallized samples, the equilibrium melting temperatures of the copolymers were obtained. Furthermore, isothemal crystallization kinetics was analyzed according to the Avrami treatment. Values of the exponent n close to 3 were obtained, independently of crystallization temperature and composition, in agreement with a crystallization process originating from predeterminated nuclei and characterized by three‐dimensional spherulitic growth. Space‐filling banded spherulites were observed by hot‐stage optical polarizing microscopy at all the crystallization temperatures explored, the band spacing being affected by both crystallization temperature and composition. As expected, the introduction of ε‐caprolactone comonomeric units in the polymer chain of PHEBA was found to decrease its crystallization rate.     

Ru-Containing Polymeric Catalysts for Cellulose Conversion to Polyols

In this paper Ru-containing catalysts based on hypercrosslinked polystyrene (MN-270) and its functional analogues (MN-100 and MN-500) were studied for the first time in cellulose hydrolytic hydrogenation. The catalysts were characterized using transmission electron microscopy (TEM), high resolution TEM, and porosity measurements. Catalytic studies demonstrated that the catalyst containing 1.0 % Ru and based on MN-270 is the most active. The total yield of sorbitol and mannitol was 50 % on the average at 85 % cellulose conversion.