Monomeric antioxidants. An 1H-NMR spectrometry study of their homopolymerization

Summary The polymerization behaviour of 3,5-di-tert-butyl-4-hydroxy-benzylmethacrylate (I), trans-3,5-di-tert-butyl-4-hydroxycinnamic acid (II), 3,5-di-tert-butyl-4-hydroxystyrene (III) and N-(3,5-ditert-butyl-4-hydroxybenzyl)maleimide (IV) was investigated. These monomeric antioxidants were polymerized in aromatic solvents, in the presence of usual radical initiators, by refluxing under nitrogen. An ¹H-NMR spectrometry method for the calculation of polymerization conversion was developed. The disappearance of the monomer double bond was followed using dibenzyl ether as an internal standard. The reactivity of these monomers, all showing the same antioxidant functionality, decreased in the order IV>I>III. The acid antioxidant (II) was not capable of polymerization.     

PBT blends with rigid polymer and elastomer inclusions: the effect of component type and reactivity on mechanical behaviour

The present study shows the potential of the poly(butylene terephthalate) (PBT) matrix to form ternary blends with well‐balanced properties, analogous to Polyamide 6 (PA6) systems with a very fine (<100 nm) separately dispersed rigid polymer (poly(styrene‐co‐maleic anhydride)) and elastomer (maleated ethylene‐propylene elastomer). The use in PBT blends of maleated components analogous to those in the PA6 systems was much less effective, due to the presence of larger particles. Enhancement of all properties, including toughness, was found in the case of a blend containing at least one component with epoxide groups, such as rigid styrene‐glycidyl methacrylate copolymer or elastomeric poly[(ethylene)‐co‐(methyl acrylate)‐co‐(glycidyl methacrylate)]. In this case, the reactive compatibilization of the epoxy‐group‐containing component caused refinement of particle size of the other component due to enhanced viscosity. As a result, more advantageous micromechanical behaviour of this ternary in comparison with the binary system occurs. The PBT matrix offers a similar potential to PA6 in synergistic influencing of both well‐dispersed phases. This work supports the universality of rigid polymer‐elastomer combination for the enhancement of the properties of pseudoductile polymers. Copyright © 2004 Society of Chemical Industry     

Gray-scale image enhancement as an automatic process driven by evolution.

Image enhancement is the task of applying certain transformations to an input image such as to obtain a visually more pleasant, more detailed, or less noisy output image. The transformation usually requires interpretation and feedback from a human evaluator of the output result image. Therefore, image enhancement is considered a difficult task when attempting to automate the analysis process and eliminate the human intervention. This paper introduces a new automatic image enhancement technique driven by an evolutionary optimization process. We propose a novel objective criterion for enhancement, and attempt finding the best image according to the respective criterion. Due to the high complexity of the enhancement criterion proposed, we employ an evolutionary algorithm (EA) as a global search strategy for the best enhancement. We compared our method with other automatic enhancement techniques, like contrast stretching and histogram equalization. Results obtained, both in terms of subjective and objective evaluation, show the superiority of our method.     

Modeling of drain current overshoot and recombination lifetimeextraction in floating-body submicron SOI MOSFETs

This work reports on a new general modeling of recombination-based mechanisms related to electrically floating-body partially-depleted (PD) SOI MOSFETs. The model describes drain current overshoots induced when turning on the transistor gate and suggests a novel extraction method for the recombination lifetime in the silicon film. We show that the recombination process associated with drain current overshoots in PD silicon-on-insulator (SOI) MOSFETs takes place mainly in the depletion region and not in the neutral region as in case of pulsed MOS capacitors. Associated with existing techniques for generation lifetime extraction, our model offers, for the first time, the possibility of complete and rapid characterization for both generation and recombination lifetime using drain current transients in floating-body SOI MOSFETs. The model is used in order to characterize submicron SOI devices, allowing a thorough investigation of technological parameters impact on floating-body-induced transient mechanisms     

Generation-recombination transient effects in partially depletedSOI transistors: systematic experiments and simulations

A synthesis of the most frequent transient phenomena due to floating-body effects in partially depleted SOI MOSFET's is presented. The dominant physical mechanisms are examined through a variety of experiments. Comprehensive models which predict the transient effects are included in SOISPICE. Simulated transients involving both generation and recombination are fully validated by the experiments and are shown to he useful for reliable carrier lifetime extraction as well as SOI circuit simulation     

Catalytic Combustion of the Stoichiometric n-Butane/Air Mixture on Isothermally Heated Platinum Wire

The catalytic combustion of the stoichiometric n-butane–air mixture per se or diluted with N₂, on a platinum wire at different initial pressures (10–70 kPa) and temperatures (690–1,080 K) was studied. The chemical heat flow rate, dQ _r/dt, of the surface reaction was measured in isothermal and isobaric conditions and the overall kinetic parameters were evaluated for both steady state and initial transient catalytic combustion. At low total pressure (10 kPa), the temperature dependence of dQ _r/dt indicated a normal (Arrhenius) behavior for 690 < T < 900 K, while at higher temperatures, over 900 K, an anti-Arrhenius behavior was found. The obtained results are consistent with a diffusion-controlled process, accompanied by reactant depletion around the catalytic surface, at higher temperatures.     

Applications of Nanomaterials in Cell Stem Therapies and the Onset of Nanomedicine

Stem cells hold enormous potential in the treatment of diseases such as diabetes, arthritis, cirrhosis, spinal cord injury, and Alzheimer's disease, due to their unique ability to differentiate into various cell lines and tissues and integrate seamlessly into damaged or diseased tissue. The use of nanoparticles as bioactive molecules is still considered a nascent science, but their unique physical and chemical properties hold great hopes for drug delivery, cancer targeting, and bioimaging. There is active worldwide ongoing research to generate advanced therapeutic compounds for incurable diseases, combining the unique properties of nanomaterials and stem cells. The present review will cover emerging areas of nanotechnology applications in stem cell therapy, one of the next frontiers of medical science.     

Polyethylene materials with multifunctional surface properties by electrospraying chitosan/vitamin E formulation destined to biomedical and food packaging applications

A dual-bioactive layer based on antimicrobial chitosan and antioxidant vitamin E was immobilized onto PE surface using electrospraying as coating technique. Covalent bonding of the antibacterial/antioxidant layer was achieved through amide bonds or carbamate linkage using both 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride and N-hydroxysuccinimide or carbonyldiimidazole coupling agents, respectively. The chitosan/vitamin E formulation was characterized by rheological measurements. The vitamin E addition in chitosan matrix leads to changes in chitosan rheological properties, such as viscosity decrease with increasing vitamin E content, change of the gel-like behavior to a fluid-like behavior, which further influences the electrospraying process and deposited coating morphology. The new stratified hybrid materials with improved properties have been characterized by different techniques as attenuated total reflectance-Fourier transform IR spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS), polyelectrolyte and potentiometric titration, contact angle titration, scanning electron microscopy (SEM) and antibacterial and antioxidative tests. The electrosprayed bioactive coatings exhibit antibacterial, antioxidant and pH responsive activity. The pH responsiveness was evidenced by switching from hydrophilic to hydrophobic surface at pH ≈ 6. The chitosan/vitamin E modified PE substrate inhibited the growth for three different bacterial strains (Gram-negative and Gram-positive) and presented good antioxidative properties, acting as DPPH radical scavenging surfaces. Moreover, the new obtained materials present good stability and maintain their antioxidative capacity even after subjecting to desorption in harsh medium because of relative strong electrostatic and hydrogen bonds interactions between components of the formulation. The obtained materials can find application in food packaging or in medical field where synergistic action of these bioactive compounds is required.     

From Geometric Transformations to Auxetic Metamaterials

The paper introduces a new alternative towards fabrication of auxetic metamaterials (materials with negative Poisson’s ratio) controlled by geometric transformations. These transformations are derived from the theory of small (infinitesimal) elastic deformation superimposed on finite elastic deformations. By using this theory, a cylindrical region filled with initial deformed foam is transformed through deformation into a cylindrical shell region filled with auxetic metamaterial. As an example, the realization of the seismic cloak device becomes a practical possibility.