Fatty and resin acids of spanishpinus pinaster Ait. Subspecies

The qualitative and quantitative composition of the acid fraction of wood extractives from three SpanishPinus pinaster Ait. subspecies (Atlantic, mountain Mediterranean and plain Mediterranean) were studied. Seven samples of each subspecies were prepared according to Technical Association of Pulp and Paper Standards, extracted with petroleum ether (b.p. 40–60°C) in a Soxhlet apparatus and saponified with ethanolic 0.4N potassium hydroxide. The acid fraction was methylated with diazomethane and studied by combined gas chromatography/mass spectrometry. The major constituents found were palmitic, oleic and linoleic among the fatty acids and pimaric, sandaracopimaric, levopimaric, isopimaric, abietic and dehydroabietic among the resin acids. Neoabietic and palustric acids were not found. Variations in the quantitative composition of the acid fraction enable us to distinguish the three subspecies. Main quantitative differences are found between the Atlantic subspecies and the two Mediterranean subspecies.     

Induction charge detector with multiple sensing stages

An induction charge detector yields the net charge and the time of flight of a particle. The unique ability to independently measure these two parameters sets apart this rather simple detection technique. The main shortcoming of this instrument is its high charge detection limit, resulting from the intrinsic noise of the detector electronics and the low signal associated with the charge to measure. The goal of the present work is to lower the detection limit of this detector. This article describes an induction charge detector whose main novelty is a sequence of aligned cylindrical electrodes for measuring the charge of a particle n times. In a time domain analysis, this feature reduces both the detection limit and the standard error of the charge measurement by factors of square root of 2 and square root of n. More importantly, sensing stages could be added to arbitrarily lower the detection limit in a frequency domain analysis.     

A portable wireless biometric multi-channel system

This article presents an 8-channel system for capturing bioelectric signals and transmitting them by the ZigBee protocol. It is a small, portable system with optimised power supply so that it can be battery fed. One of its main advantages is its versatility, since it enables each channel to be configured, in a dynamic and individualised way. This makes it possible to capture diverse bioelectric signals simultaneously, such as electrocardiogram (ECG), electroencephalogram (EEG), electrooculogram (EOG), etc. The developed system can be easily integrated into a Wireless Sensor Network based on ZigBee technology.     

Accuracy evaluation for sub-aperture interferometry measurements of a synchrotron mirror using virtual experiments

We present a virtual experiment for the accuracy assessment of the sub-aperture interferometric measurement of a synchrotron mirror involving several thousand sub-aperture topographies. The virtual experiment simulates the measurement process and accounts for the influence of positioning device errors, interferometer errors, non-perfect calibration of machine geometry as well as errors in the interferometer reference. Two principles are considered for reconstructing the form of a test specimen from the conducted sub-aperture topographies, a stitching procedure and a direct measurement method. The virtual experiments are applied to the task of absolute form measurement (including its radius of curvature) of a synchrotron mirror with a length of 30 cm, a width of 4 cm, a maximum curvature of about 44 mm⁻¹ and a peak-to-valley of 5 mm. As a result, reconstruction accuracies can be expected to be in the range of 100 nm when the stitching method is applied, which outperforms the direct measurement method by a factor of about 3.     

Differential nanofiller cluster formations in dental adhesive systems

Nanofillers are added to dental adhesives to improve mechanical properties of the hybrid layer. Ethanol or water added to the demineralized dentin to improve adhesive infiltration may produce filler aggregation. OBJECTIVE: To assess the effect of 5 vol% water or ethanol addition on nanoparticles distribution in dental adhesives. METHODS: Six available commercial adhesives systems were selected: Clearfil SE Bond (CSE), Clearfil Protect Bond (CPB), FL‐Bond (FLB), Clearfil S3 (CS3), Bond Force (BF), One Up Bond F plus (OUB), and an experimental adhesive system without filler (EXP). Polymer films were obtained by adding 0 (control) or 5 vol% water or ethanol into the bonding resins. Preparations were light‐cured (40 s). Three specimens were analyzed for each mixture. Three phases and 3D images were taken from each specimen by means of an atomic force microscope in taping mode (TM/AFM). Cluster sizes and surface nanoroughness were assessed. RESULTS: Control specimens from CSE, FLB, OUB, and BF presented clusters. The addition of solvents lead to particles aggregation in tested bonding resins. Ethanol addition produced more aggregates, particularly in adhesives containing fluoraluminosilicate as fillers. CONCLUSIONS: Nanofillers aggregation occurred in all adhesive systems in presence of additional solvents. In general, aggregate sizes were higher after the addition of ethanol. Formed clusters size values are always above the dimensions of the spaces existing between the demineralized collagen fibers. Microsc. Res. Tech. 75:749–757, 2012. © 2011 Wiley Periodicals, Inc.     

Evolution of the thymus size in response to physiological and random events throughout life

During embryogenesis and in the early stages of life, the thymus is a crucial organ for the generation of the T cell repertoire. T cells are generated from hematopoietic stem cells already differentiated to precursor T cells in the bone marrow. These cells enter the thymus guided by chemotactic factors secreted by this organ. The complex maturation process takes place that ensures self-tolerance and homeostasis. Thymocytes that show autoreactivity do not leave the thymus, but rather die by apoptosis. The final percentage of mature T cells that survive to migrate from the thymus to the periphery is very low: at most 5%, under optimal conditions. The highest migration occurs in childhood and adulthood, at least in mice and humans; however, it declines throughout life and is minimal in the elderly. Under normal circumstances, the thymus commences involution soon after birth, and this involution correlates with the capacity to export mature T cells to the periphery. Hormones, cytokines, and neurotransmitters all play a role in this age-associated process, but the reasons for and mechanisms of this involution remain unknown. Apart from physiological conditions that change throughout life and govern age-related thymus evolution, random states and events provoked by intrinsic or extrinsic factors can induce either thymus involution, as in reversible transient thymic hypoplasias, or thymic hyperplasias. The age-associated involution, unlike transient involutions, follows a regular pattern for all individuals, though there are clear differences between the sexes. Nevertheless, even the age-associated involution seems to be reversible, raising the possibility of therapeutic strategies aimed at enhancing thymus function in the elderly.     

Different strategies for selective monoacylation of hexoaldoses in acetone

Experimental protocols for the selective production of 6-O-acylhexoaldose emulsifiers from precursor sugars (mannose, glucose, and galactose) and corresponding fatty acids are compared. The protocols employ an immobilized Candida antarctica lipase in a solvent (acetone) which is both easily eliminated and accepted by the European Economic Community for use as an extraction solvent in the manufacture of foods and/or food additives. This comparative study provides guidelines for selection of appropriate conditions for quantitative monoacylation of aldoses in acetone, on the basis of the solubilities of the precursor sugar and the monoester in acetone at different temperatures. Although relatively low temperatures (<40°C) favor precipitation of glucose monoesters, higher temperatures (e.g., 55°C) should be used to increase solubility of mannose and thus selectivity of the reaction leading to the mannose ester. Galactose is transformed with poor selectivity to the desired monoester by these procedures. Factors affecting the viability of these synthetic reactions in acetone are also discussed.     

Microstructural Design of Silicon Nitride with Improved Fracture Toughness: II, Effects of Yttria and Alumina Additives

Significant improvements in the fracture resistance of self-reinforced silicon nitride ceramics have been obtained by tailoring the chemistry of the intergranular amorphous phase. First, the overall microstructure of the material was controlled by incorporation of a fixed amount of elongated ß-Si₃N₄ seeds into the starting powder to regulate the size and fraction of the large reinforcing grains. With controlled microstructures, the interfacial debond strength between the reinforcement and the intergranular glass was optimized by varying the yttria-to-alumina ratio in the sintering additives. It was found that the steady-state fracture toughness value of these silicon nitrides increased with the Y:Al ratio of the oxide additives. The increased toughness was accompanied by a steeply rising R -curve and extensive interfacial debonding between the elongated ß-Si₃N₄ grains and the intergranular glassy phase. Microstructural analyses indicate that the different fracture behavior is related to the Al (and O) content in the ß´-SiAlON growth layer formed on the elongated ß-Si₃N₄ grains during densification. The results imply that the interfacial bond strength is a function of the extent of Al and Si bonding with N and O in the adjoining phases with an abrupt structural/chemical interface achieved by reducing the Al concentration in both the intergranular phase and the ß´-SiAlON growth layer. Analytical modeling revealed that the residual thermal expansion mismatch stress is not a dominant influence on the interfacial fracture behavior when a distinct ß´-SiAlON growth layer forms. It is concluded that the fracture resistance of self-reinforced silicon nitrides can be improved by optimizing the sintering additives employed.     

A probabilistic model for discretionary lane change proposals in highway driving situations

This contribution presents a novel probabilistic approach for the generation of discretionary lane change proposals with a focus on highway driving situations. The developed model is based on the quantification of the utility of driving lanes. It generates a lane change proposal if the current driving lane is unsatisfactory in the sense that the desired velocity of the automated vehicle is undershot because of a slow preceding vehicle. A driving simulator study was conducted to create a dataset for the optimization of the model parameters. The optimization goal is to accurately match the timings of the lane change intentions of all participants. Finally, the applicability of the model is shown on real data from a test vehicle.

     

Distillation column configurations in ammonia–water absorption refrigeration systems

In ammonia–water absorption refrigeration systems a purification process to reduce the water content in the vapour leaving the generator is required. During this process the water content in the vapour must be reduced to a minimum, otherwise it tends to accumulate in the evaporator and strongly deteriorates the efficiency of the system. The vapour purification can be carried out by partial condensation, by establishing a liquid–vapour counter flow or by combining both methods. In systems with partial condensation, the distillation column can be composed of one or more rectifiers using different cooling mediums, and the rectifying and stripping sections. In complete condensation systems only the rectifying and stripping sections can be used. Therefore different distillation column arrangements should be considered. This paper presents a study of several distillation column configurations for single stage ammonia–water absorption refrigeration systems with partial and complete condensation. In order to evaluate and compare the different configurations, a parameter that indicates the ratio of the ammonia vapour concentration increase in each part of the column to the total ammonia purification has been defined. The analysis has been based on the system COP. Finally the efficiency in each part of the column has been calculated to estimate its design requirements.