Development and application of triglyceride-based polymers and composites

Triglyceride oils derived from plants have been used to synthesize several different monomers for use in structural applications. These monomers have been found to form polymers with a wide range of physical properties. They exhibit tensile moduli in the 1–2 GPa range and glass transition temperatures in the range 70–120 °C, depending on the particular monomer and the resin composition. Composite materials were manufactured utilizing these resins and produced a variety of durable and strong materials. At low glass fiber content (35 wt %), composites produced from acrylated epoxidized soybean oil by resin transfer molding displayed a tensile modulus of 5.2 GPa, a flexural modulus of 9 GPa, a tensile strength of 129 MPa, and flexural strength of 206 MPa. At higher fiber contents (50 wt %) composites produced from acrylated epoxidized soybean oil displayed tensile and compression moduli of 24.8 GPa each, and tensile and compressive strengths of 463.2 and 302.6 MPa, respectively. In addition to glass fibers, natural fibers such as flax and hemp were used. Hemp composites of 20% fiber content displayed a tensile strength of 35 MPa and a tensile modulus of 4.4 GPa. The flexural modulus was ∼2.6 GPa and the flexural strength was in the range 35.7–51.3 MPa, depending on the test conditions. The flax composite materials had tensile and flexural strengths in the ranges 20–30 and 45–65 MPa, respectively. The properties exhibited by both the natural- and synthetic fiber-reinforced composites can be combined through the production of “hybrid” composites. These materials combine the low cost of natural fibers with the high performance of synthetic fibers. Their properties lie between those displayed by the all-glass and all-natural composites. Characterization of the polymer properties also presents opportunities for improvement through genetic engineering technology. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 703–723, 2001     

Local Viscosity of Si-O-C-N Nanoscale Amorphous Phases at Ceramic Grain Boundaries

Internal friction characterization has been used to quantitatively assess the viscosity characteristics of Si-O-C-N glasses segregated to nanometer-sized grain boundaries of polycrystalline Si₃N₄ and SiC ceramics. A relaxation peak of internal friction, which arises with rising temperature from the viscous sliding of glassy grain boundaries, was systematically collected and analyzed with respect to its shift upon changing the oscillation frequency. As a result of such an analysis, both activation energy for viscous grain-boundary flow and inherent viscosity of the intergranular glass film could be quantitatively evaluated. Two main features are shown: (i) the presence of N and/or C greatly affects the viscosity characteristics of SiO₂ phases at Si₃N₄ and SiC grain boundaries; and (ii) the internal friction method has potential as a unique experimental tool for understanding the local properties of nanoscale amorphous phases in new ceramic materials.     

Raman Microprobe Evaluation of Bridging Stresses in Highly Anisotropic Silicon Nitride

The microscopic bridging stress distribution developed behind the crack tip of a highly anisotropic silicon nitride has been measured along the crack profile using Raman microprobe spectroscopy with a micrometer spatial resolution. The near-tip rising R -curve behavior and the crack-opening displacement (COD) profile of the material were also determined and discussed in comparison with the Raman microstress data. A comparison with the fracture behavior of a previously investigated silicon nitride material with a three-dimensional random microstructure is also proposed. According to this set of micro/macroscopic fracture characterizations, a self-consistent view of toughening behavior in silicon nitride ceramics is obtained, and the role on toughness of anisotropically oriented acicular grains clarified. In agreement with previous studies, it is confirmed that crack-face bridging is the most effective mechanism for toughening silicon nitride ceramics.     

Possible optimal configurations for the ZECOMIX high efficiency zero emission hydrogen and power plant

Coal use for electricity generation will continue growing in importance. In the present work the optimization of a high efficiency and zero emissions coal-fired plant, which produces both hydrogen and electricity, has been developed. The majority of this paper concerns an integration of gasification unit, which is characterized by coal hydrogasification and carbon dioxide (CO₂) separation, with a power island, where a high-hydrogen content syngas is burnt with pure oxygen stream. Another issue is the high temperature CO₂ desorption. Because of the elevated temperature heat supply, the regeneration process affects the overall performance of ZECOMIX plant. An advanced steam cycle characterized by a medium pressure steam compressor and expander has been considered for power generation. A preliminary study of different components leads to analyze possible routes for optimization of the whole plant. The plant equipped with a CO₂ capture unit could reach efficiency close to 50%. The simulations of a thermodynamic model were carried out using the software ChemCAD.

This study is a part of a larger research project, named ZECOMIX, led by ENEA (Italian Research Agency for New technologies, Energy and Environment), other partners being ANSALDO and different Italian Universities. It is aimed at analyzing an integrated hydrogen and power production plant.     

A Quick Simulation Technique for a Fluid Information Storage Problem

In this paper we present an application of Importance Sampling (IS) for quick simulation of buffer overflow probability in a statistical multiplexer loaded with a number of independent Markov modulated fluid sources. Runtime improvement is deducible from N_MCσ²(p) and N_ISσ²(p^*) that characterize the trade-offs between sample size and variance of the estimators of buffer overflow probability experienced in Monte Carlo (MC) and Importance Sampling simulations. By assuming that the same precision is achieved for the two kinds of simulations if σ²(p)=σ²(p*), an approximate closed form expression for the ratio N_IS/N_MC is derived, and it is minimized with respect to the load of the multiplexer. In the final part of the paper some numerical examples are presented to illustrate the benefits of IS in evaluating very low overflow probabilities.     

Filtering activity of Spongia officinalis var. adriatica (Schmidt) (Porifera, Demospongiae) on bacterioplankton: implications for bioremediation of polluted seawater

A study on the filtering activity has been carried out on reared specimens of the demosponge Spongia officinalis var. adriatica coming from an off-shore farm displaced off the Apulian coast (Ionian Sea). The experience was carried out under laboratory conditions, by using natural seawater collected from the sponge environment. The study demonstrates a high efficiency of the sponge in removing bacteria. Bacterial concentration significantly decreases in presence of the sponge, with a marked drop after 2 h from the start of the experience. The maximum clearance rate was 210 ml h(-1) g(-1) DW at 60 min. Retention efficiency reached the highest value of 61% at 120 min. The bacterial density removed by the S. officinalis filtering activity was 12.3 +/- 1.8 x 10(4) cells ml(-1) corresponding to a biomass of about 11.7 +/- 1.4 microg Cl(-1). The sponge fed preferentially large- and medium-size bacteria, whereas the small ones are fed after the removal of the largest size categories. The results obtained suggest that S. offcinalis is a suitable species for marine environmental bioremediation.     

2,3‐Disubstituted Benzo[b]thiophenes from Diarylalkynes via Electrophilic Addition‐Cyclization and Palladium‐Catalyzed Cross‐Coupling

Diarylalkynes are readily transformed in 3‐chlorobenzo[b]thiophenes in a two‐step electrophilic addition‐cyclization procedure that runs highly efficiently in solution or in the solid phase. The heteroaromatic carbon‐chlorine bond participates in palladium‐catalyzed Suzuki–Miyaura or Buchwald–Hartwig cross‐couplings to give, in a single step, 2,3‐disubstituted derivatives of pharmacological relevance .     

A new hybrid MCDM approach for RPN evaluation for a medical device prototype

The Failure Mode and Effect Analysis (FMEA) is a useful instrument born in the aerospace industry and widely used to improve a process or product's efficiency. Over the years, this instrument has been adopted in increasingly different contexts, such as HealthCare. This paper proposes an approach aimed at improving the defects typical of the classic FMEA in the design phase, that is, in a scenario full of uncertainties and with little information available, using a new hybrid Multiple-criteria decision-making (MCDM) method in order to obtain a priority index more performant than Risk Priority Number (RPN). In the proposed method, the three assessment criteria have a different weighting in the index's final computation, differently from the classical RPN. These weights are obtained with a scientific technique, thus avoiding that excessive subjectivity influences the final result. A more efficient priority index is obtained through a new hybrid approach that solves some classical RPN gaps. A case study concerning an endoscope Ear Nose Throat Entropy (ENT) prototype is examined to illustrate the proposed method. FMEA analysis in HealthCare is increasingly used for its flexibility and reliability. This study focuses on using new techniques to eliminate certain defects or exploit some qualities better. The use of a robust and elastic innovative MCDM method to calculate a new priority index and a scientific technique to obtain the weight of the selection are the interesting insights proposed in this paper.     

Dynamic response of the ITER tokamak during asymmetric VDEs

During the operational life of ITER, it is expected that a number of vertical displacement events (VDEs) will occur. A sub-class of these events, ‘slow’ asymmetric VDEs, is of particular interest from a structural point of view. This is because the forces generated during such events are both substantial and sufficiently long-lasting to significantly excite the structure. It is necessary to establish that the absolute and relative displacements of components, as well as internal and external forces, stay within acceptable limits during these events. Previous studies have investigated this problem using relatively simple models and non-rotating loads. A new, more detailed, 360-degree model was developed, and used to assess the effects of asymmetric VDEs. This paper presents the main results of this investigation. It is shown that the distance between the VV and the TFC at the inboard wall can decrease by as much as 19 mm at the equatorial plane, and that the vertical reaction force in the Vacuum Vessel supports can reach 15 MN.     

Human Aquaporin-4 and Molecular Modeling: Historical Perspective and View to the Future

Among the different aquaporins (AQPs), human aquaporin-4 (hAQP4) has attracted the greatest interest in recent years as a new promising therapeutic target. Such a membrane protein is, in fact, involved in a multiple sclerosis-like immunopathology called Neuromyelitis Optica (NMO) and in several disorders resulting from imbalanced water homeostasis such as deafness and cerebral edema. The gap of knowledge in its functioning and dynamics at the atomistic level of detail has hindered the development of rational strategies for designing hAQP4 modulators. The application, lately, of molecular modeling has proved able to fill this gap providing a breeding ground to rationally address compounds targeting hAQP4. In this review, we give an overview of the important advances obtained in this field through the application of Molecular Dynamics (MD) and other complementary modeling techniques. The case studies presented herein are discussed with the aim of providing important clues for computational chemists and biophysicists interested in this field and looking for new challenges.