Drug release assays from new chitosan/pHEMA membranes obtained by gamma irradiation

With the purpose of obtaining a biocompatible and microbiologically safe matrix that simultaneously could be used as wound dressing material and as a controlled drug release system, membranes with different thickness and different contents in chitosan and hydroxyethyl methacrylate (HEMA) have been prepared by γ irradiation from a ⁶⁰Co source. Antibiotic release experiments were performed before or after irradiation over amoxicillin loaded chitosan/pHEMA membranes in physiological saline solution, and monitored by UV-Vis spectrometry.Results point out a fast amoxicillin release with similar release profile in all studied membranes. The amount of released drug was shown to be dependent on membranes network crosslinking due composition, radiation and membrane thickness.     

IPN’s of acrylic acid and N-isopropylacrylamide by gamma and electron beam irradiation

Interpenetrating networks (IPN) of temperature sensitive N-isopropylacrylamide (NIPAAm) and pH sensitive acrylic acid (AAc) monomer were prepared in two consecutive steps. Hydrogels of AAc were synthesized by gamma radiation from a ⁶⁰Co gamma source and an electron beam from a Van de Graaff accelerator. A second hydrogel of NIPAAm was synthesized within the first AAc hydrogel by polymerization and cross-linking with a redox initiator and cross-linking agent. The thermal and pH sensitivity of the hydrogels were determined by measuring the swelling, and the morphology and composition by SEM.     

Radiation-induced grafting of N-isopropylacrylamide and acrylic acid onto polypropylene films by two step method

Binary graft copolymerization of pH sensitive acrylic acid (AAc) and thermosensitive N-isopropylacrylamide (NIPAAm) monomers onto pre-irradiated polypropylene films (PP) was carried out by two individual steps using a Co⁶⁰ gamma radiation source. The influence of preparation conditions, such as pre-irradiation dose and reaction time on grafting yield was studied. The swelling behavior and FTIR-ATR study for PP films grafted films were investigated.     

Heat load behaviors of plasma sprayed tungsten coatings on copper alloys with different compliant layers

Plasma sprayed tungsten (PS-W) coatings with the compliant layers of titanium (Ti), nickel-chromium-aluminum (NiCrAl) alloys and W/Cu mixtures were fabricated on copper alloys, and their properties of the porosity, oxygen content, thermal conductivity and bonding strength were measured. High heat flux tests of actively cooled W coatings were performed by means of an electron beam facility. The results indicated that APS-W coating showed a poorer heat transfer capability and thermo-mechanical properties than VPS-W coating, and the compliant layers improved W coating performance under the heat flux load. Among three compliant layers, W/Cu was the preferable because of its better effects on heat removal and stress alleviating. The optimization of W/Cu compliant layer found that 0.1 mm and 25 vol.%W was optimum compliant layer structure for 1 mm W coating, which induced a 23% reduction of the maximum stress compared to the sharp interface, and the plastic strain was reduced to 0.01% from 1.55%.     

Study of polypropylene/polybutene blends modified by gamma irradiation and (high melt strength polypropylene)/polybutene blends

It is well-known that polypropylene (PP) is difficult to process as a consequence of its linear structure. It is also known that grafting of long-chain branches on PP backbone using ionizing radiation is an effective approach to achieve high melt strength polypropylene (HMS PP). Chain-scission and, in minor extend, crosslinking and grafting are the predominant reaction in order to branch PP backbone. However, if multifunctional monomers are used to promote the grafting reaction, crosslinking can surpass chain scission and grafting, reducing drawability. Therefore, in an effort to enhance the processability and so the drawability, it has been found helpful to add a small amount of polybutene-1. Gamma irradiation technique was used to induce chemical changes in blends of PP and polybutene in acetylene atmosphere (crosslinker promoter) and in HMSPP/polybutene blends. The samples were irradiated with a ⁶⁰Co source with doses of 12.5 and 20 kGy in the presence of acetylene. In this work, two different methods of blends processing were compared regarding rheological and mechanical properties. Effects on the strength and elongation at the yield point and at rupture were observed by mechanical tests and showed decrease of tensile strength and increase of elongation at rupture for samples obtained by irradiation of blends. The results from rheology demonstrated an increase in melt strength and drawability of blends.     

Rheological study of polypropylene irradiated with polyfunctional monomers

The aim of this paper is to investigate the rheological properties of polypropylene (PP) modified by ionization radiation (gamma rays) in the presence of two different monomers. The samples were mixed in a twin-screw extruder with ethylene glycol dimethacrylate (EGDMA) or trimethylolpropane trimethacrylate (TMPTMA) with concentration in the range of 0.5-5.0 mmol. After that, they were irradiated with 20 kGy dose of gamma radiation. The structural modification of polypropylene was analyzed in the melt state by measuring melt flow rate (MFR), η* (complex viscosity) and G′ (storage modulus) in the angular frequency range of 10⁻¹ to 3 × 10² rad s⁻¹. From the oscillatory rheology data, one could obtain the values of η₀ (zero shear viscosity) that would be related to the molar mass. All results were discussed with respect to the crosslinking and degradation process that occur in the post-reactor treatment to produce controlled rheology polypropylene.The resulting polymeric materials were submitted the cytotoxicity in vitro test by neutral red uptake methodology with NCTC L 929 cell line from American Type Culture Collection bank. All modified PP samples presented no cytotoxicity.     

Failure modes of vacuum plasma spray tungsten coating created on carbon fibre composites under thermal loads

Vacuum plasma spray tungsten (VPS-W) coating created on a carbon fibre reinforced composite (CFC) was tested under two thermal load schemes in the electron beam facility to examine the operation limits and failure modes. In cyclic ELM-like short transient thermal loads, the VPS-W coating was destroyed sub-layer by sub-layer at 0.33 GW/m² for 1 ms pulse duration. At longer single pulses, simulating steady-state thermal loads, the coating was destroyed at surface temperatures above 2700 °C by melting of the rhenium containing multilayer at the interface between VPS-W and CFC. The operation limits and failure modes of the VPS-W coating in the thermal load schemes are discussed in detail.     

Ultra-violet protection and water repellency of polyester fabrics treated by surface deposition of nickel under the effect of low temperature plasma

This paper is aimed at understanding the textile properties of nickel-deposited polyester fabric after treating with low temperature plasma treatment. Low temperature plasma treatment with oxygen gas was employed in this paper to activate a hydrophilic surface for the polyester fabrics and hence facilitate the nickel deposition through an electroless plating process. The textile properties of plasma-induced electroless nickel-plated polyester fabrics were evaluated by different standard testing methods in terms of both physical and chemical performances. The electroless nickel plating with plasma treatment improved significantly the performance of nickel-plated polyester fabrics as reflected by the scanning electron microscopy, tensile strength, ultraviolet protection as well as fabric weight. On the contrary, it also enhanced the fabric thickness and colour fastness to crocking. In addition, there was no influence on the performance of colour fastness to light and colourfastness to laundering. Moreover, the application of plasma treatment adversely affected slightly the performance of contact angle and wrinkle recovery property.     

Space- and time-resolved optical diagnosis for the study of laser ablation plasma dynamics

The dynamics of transient plasmas generated by high-fluence nanosecond laser ablation has been investigated by means of optical methods (time- and space-resolved emission spectroscopy and fast ICCD imaging). Systematic measurements have been carried out on plasma produced in vacuum (10⁻⁸ Torr residual pressure) by Nd:YAG laser (10 ns, 532 nm) irradiation of Aluminum targets. Al neutral atoms and different charge state ions have been monitored through the evolution of corresponding spectral lines. The study evidenced the presence of two different groups of particles, tentatively related to two distinct ejection mechanisms. This behavior has been confirmed by the fast ICCD (20 ns gate) recording of the total optical emission of the plume. The application of the relative line intensity method to the study of the excitation temperature axial profile is equally discussed.     

Study of H loss from hydrogenated Hg1−xCdxTe under high electronic excitation by elastic recoil detection analysis (ERDA)

Large erosion (∼1.1 × 10⁴ atoms/ion) of H from hydrogenated MCT wafers is observed due to the bombardment with 80 MeV Ni⁹⁺ ions. The initial H areal concentration and hydrogen depletion rate is monitored by elastic recoil detection analysis. The ion-damaged zones from where depletion of H takes place have been calculated from fluence-dependent hydrogen areal content analysis. The results are explained on the basis of the thermal spike model of ion-solid interaction.     

Deposition of gold nano-particles and nano-layers on polyethylene modified by plasma discharge and chemical treatment

Polyethylene (PE) was treated in Ar plasma discharge and then grafted from methanol solution of 1,2-ethanedithiol to enhance adhesion of gold nano-particles or sputtered gold layers. The modified PE samples were either immersed into freshly prepared colloid solution of Au nano-particles or covered by sputtered, 50 nm thick gold nano-layer. Properties of the plasma modified, dithiol grafted and gold coated PE were studied using XPS, UV-VIS, AFM, EPR, RBS methods and nanoindentation. It was shown that the plasma treatment results in degradation of polymer chain, creation of excessive free radicals and conjugated double bonds. After grafting with 1,2-ethanedithiol the concentration of free radicals declined but the concentration of double bonds remained unchanged. Plasma treatment changes PE surface morphology and increases surface roughness too. Another significant change in the surface morphology and roughness was observed after deposition of Au nano-particles. The presence of Au on the sample surface after the coating with Au nano-particles was proved by XPS and RBS methods. Nanoindentation measurements shown that the grafting of plasma activated PE surface with dithiol increases significantly adhesion of sputtered Au nano-layer.     

Swift heavy ion induced phase transition in CdTe films deposited by spray pyrolysis in presence of electric field

CdTe polycrystalline thin films possessing hexagonal phase regions are obtained by spray deposition in presence of a high electric field. Thin film samples are irradiated with 100 MeV Ag ions using Pelletron accelerator to study the swift heavy ion induced effects. The ion irradiation results in the transformation of the metastable hexagonal regions in the films to stable cubic phase due to the dense electronic excitations induced by beam irradiation. The phase transformation is seen from the X-ray diffraction patterns. The band gap of the CdTe film changes marginally due to ion irradiation induced phase transformation. The value changes from 1.47 eV for the as deposited sample to 1.44 eV for the sample irradiated at the fluence 1×10¹³ ions/cm². The AFM images show a gradual change in the shape of the particles from rod shape to nearly spherical ones after irradiation.     

Fabrication of uniform ZrC coating layer for the coated fuel particle of the very high temperature reactor

Fuel for the very high temperature reactor is required to be used under severer irradiation conditions and higher operational reactor temperatures than those of present high temperature gas cooled reactors. Japan Atomic Energy Agency has developed zirconium carbide (ZrC)-coated fuel particles previously in laboratory scale which are expected to maintain their integrity at higher temperatures and burnup conditions than conventional silicon carbide-coated fuel particles. As one of the important R&D items, ZrC coating process development has been started in the year 2004 to determine the coating conditions to fabricate uniform structure of ZrC layers by using a new large-scale coater up to 0.2 kg batch. It was thought that excess carbon formed in the ZrC layer under the oscillation of coating temperature would cause non-uniformity of the ZrC layer. Finally, uniform ZrC coating layer has been fabricated successfully by adjusting the time constant of the coater and keeping the coating temperature at around 1400 °C.     

Temperature dependence of the chemical sputtering of amorphous hydrogenated carbon films by hydrogen

The temperature dependence of chemical erosion and chemical sputtering of amorphous hydrogenated carbon films due to exposure to hydrogen atoms (H⁰) alone and combined exposure to argon ions and H⁰ was measured in the temperature range from 110 to 950 K. The chemical erosion yield for H⁰ alone is below the detection limit for temperatures below about 340 K. It increases strongly with increasing temperature, goes through a maximum around 650–700 K and decreases again for higher temperatures. Combined exposure to Ar⁺ and H⁰ results in substantial chemical sputtering yields in the temperature range below 340 K. In this range the yield does not depend on temperature, but it increases with energy from about 1 (eroded carbon atoms per impinging Ar⁺ ion) to about 4 if the ion energy is increased from 50 to 800 eV. For temperatures above 340 K the measured erosion rates show the same temperature dependence as for the H⁰-only case, but they are higher than for H⁰-only. The difference between the Ar⁺ and H⁰ and the H⁰-only cases increases monotonically with increasing ion energy.     

Properties of poly(ethylene terephthalate) track membranes with a polymer layer obtained by plasma polymerization of pyrrole vapors

The structure and the charge transport properties of poly(ethylene terephthalate) track membrane modified by pyrrole plasma were studied. It was found that polymer deposition on the surface of a track membrane via plasma polymerization of pyrrole results in the creation of composite nanomembranes that, in the case of the formation of a semipermeable layer, possess asymmetric conductivity in electrolyte solutions - a rectification effect similar to that of a p-n junction in semiconductors. It is caused by presence in the membranes of two layers with different functional groups and also by the pore geometry. Such membranes can be used to create chemical and biochemical sensors.     

The research about the time-effect of the wettability on the wool surface treated by the Ar plasma jet in the atmospheric pressure

A facility which is called atmospheric pressure and normal temperature plasma jet was introduced in this paper. After the wool surface was treated by this kind of facility with Ar in different irradiating times, the time-effect of the fabric wettability has been weakened, and if the parameters of the irradiating time and the voltage of the facility are appropriate, the time-effect of wettability can be effectively inhibited. With the stable wettability, the fabric can be dressed without PVA (polyvinyl alcohol) which can cause lager pollution in the textile field, so the method without the time-effect of the textile wettability will be useful in the field of clean textile production. Undoubtedly, the stable wettability of textile surface was caused by the stable hydrophilic molecules on the textile surface. Thus, the reaction process and results on the textile surface treated by plasma needs to be studied to optimize the parameters of the irradiating time and the voltage of the plasma jet. So the initial experimental studies on the optimization of the parameters of the plasma jet were discussed in this paper, and the authors believe that the method without the time-effect also can be used in other fields of plasma application.