Yellow Transparent Research Articles

Absorption spectra response of XRQA radiochromic film to x-ray radiation

Gafchromic XRQA, radiochromic film is a high sensitivity auto developing x-ray analysis films designed and available for kilovoltage x-ray, dose and QA assessment applications. The film is designed for reflective analysis with a yellow transparent top filter and white opaque backing materials. This allows the film to be visually inspected for colour changes with a higher level of contrast than clear coated radiochromic films such as Gafchromic EBT version 1. The spectral absorption properties in the visible wavelengths have been investigated and results show two main peaks in absorption located at 636 nm and 585 nm. These peaks are located in the same position as EBT Gafchromic film highlighting a similar chemical monomer/polymer for radiation sensitivity. A much higher sensitivity however is found at kilovoltage energies with an average 1.55 OD units per 20 cGy irradiation variation measured at 636 nm using 150 kVp x-rays. This is compared to approximately 0.12 OD units per 20 cGy measured at 636 nm for EBT film at 6 MV x-ray energy. That is, the XRQA film is more than 10 times more sensitive than EBT1 film. The visual colour change is enhanced by the yellow polyester coating. However this does not affect the absorption spectra properties in the red region of analysis which is the main area for use using desktop scanners in reflection mode.

Pulse-Front Propagation and Interaction During the Growth of CdS Nanoparticles in a Gel

We studied the spatiotemporal dynamics of a new system consisting of sulfide ions (outer electrolyte) diffusing into an organic gel (gelatin) containing mercaptoethanol-capped cadmium ions (inner electrolyte). The product, cadmium sulfide, exhibits a faint yellow transparent propagating front starting at the gel-outer electrolyte interface. When subjected to UV light, this system reveals fluorescing CdS nuclei localized spatially in a narrow region, called pulse, that leads the front and propagates down the tube. We show that the pulse consists of CdS nanoclusters of an average size of about 4 nm, whereas the trailing front consists of 6-8 nm cubic-phase CdS crystallites. The width of the pulse remains constant in time, t, at about 2 mm and independent of the outer concentration S0. It was found that the speed of the pulse fluctuates as the concentration of the capping agent is varied, with fastest pulses attained at a concentration of 40 mM for two different outer concentrations of sulfide ions. The origin of the yellow fluorescence of the pulse originates from emission from surface states. This dynamical system was then theoretically studied using a competitive particle growth model. The resulting evolution equations were solved numerically, and the results were compared to the experimental findings. It was shown that the model agrees in many aspects with the experiment. The densities of small particles and large particles rho were shown to evolve like a pulse and a front, respectively. The front was shown to extend "diffusively" as t1/2, as found experimentally. The distance traveled by the pulse xpeak was shown to increase with outer concentration S0 and obeys a concentration power law xpeak approximately S(0)1/4. The width w of the pulse also obeys a time power law w approximately ta with a crossover between early times (a=1/3) and intermediate times (a=0). This system would enable us to study the early time dynamics of Liesegang systems.

Resistance of apple varieties and selections to Erwinia amylovora in the Czech Republic

Sixty-four apple cultivars and selections of potential interest to apple producers and plant breeders in the Czech Republic were tested for their relative resistance to the fire blight pathogen over six years. Level of fire blight resistance was evaluated according to the extent of lesion development on the shoots tips after artificial inoculation in experimental plots under insectproof nets. Cultivars Quinte (resistant) and Yellow transparent (high susceptible) were included in the tests. Of 64 apple cultivars and selections tested, none were high resistant, 3.1% were evaluated as resistant, 10.9% moderately resistant, 57.8% moderately susceptible, 21.9% susceptible and 6.3% high susceptible. Resistant apple genotypes, showing blight necrosis of shoots of 11–12%, were only cultivars Selena and Quinte. Moderately resistant genotypes (blight necrosis 13.1–25.0%) were Kordona, Golden Smoothee, Julia, HL 323, Melodie, HL 421 and S 634/3. High susceptible genotypes (blight necrosis more then 80.1%) were comprised cultivars Vesna, Topas, Yellow transparent and Vanda. The remaining genotypes were moderately susceptible (blight necrosis 26.1–60.0%) and susceptible (blight necrosis 60.1–80.0%). During six experimental years, quantitative variability was recorded in the blight score. Differences between cultivars in susceptibility to fire blight were often statistically significant.

Vapor polymerization deposition of new polyamide thin films having oligothiophene segments in the main chain

New polyamide thin films that have oligothiophene segments in the main chain have been fabricated in the form of thin films by vapor deposition polymerization. The condensation reaction for polyamide takes place between 2,2′-bithiophene-5,5′-dicarbonyl dichloride and αω-bis(aminomethyl)oligothiophene whose degree of polymerization spans dimer to pentamer. Spectroscopic data indicate that the reaction occurs successfully and that the thin films are characterized by an oligothiophene backbone. The films of high quality are uniform and yellow transparent. The morphology of the films is found to be amorphous by X-ray diffraction measurements, contrasted with the vapor deposited films of the monomers that showed a layered structure.

Synthesis and Radical Ring-Opening Polymerization Behavior of Bifunctional Vinylcyclopropane Bearing a Spiroacetal Moiety

Synthesis and radical ring-opening polymerization of bifunctional vinylcyclopropane having a spiroacetal moiety, 1,10-bis(vinyl)-4,8,12,15-tetraoxatrispiro[2.2.2.2.2.2]pentadecane (1), were carried out. 1 was prepared by the reaction of 1,1-dichloro-2-vinylcyclopropane and pentaerythritol in DMF in the presence of a base. 1 was isolated by column chromatography as a highly viscous pale yellow transparent oil. Radical polymerization of 1 was carried out in the presence of an appropriate initiator (3 mol % vs 1) at 60, 80, and 120 °C in degassed sealed ampules for 20 h. The polymerization mixtures were homogeneous during the polymerizations. Poly(1) was isolated by reprecipitation into ether with a small amount of triethylamine to avoid hydrolysis of the polymer. The crude polymerization mixtures were soluble in chlorobenzene, DMF, and chloroform ; however, the polymers after isolation were insoluble in common organic solvents. An incomplete single ring-opening polymerization was confirmed from the analyses of the 1 H- and 13 C-NMR and IR spectra of the polymer. A double ring-opened unit was not contained in the polymer. The volume shrinkage on the polymerization of 1 with AIBN at 60 °C was 4.7%.

New processable low band-gap, conjugated polyheterocycles

Poly(2,3-dihexylthieno[3,4-b]pyrazine) ( 2b) has been prepared by ferric chloride polymerization of 2,3-dihexylthieno[3,4-b]pyrazine( 4) and studied. It is a dark blue-black soluble material which becomes light yellow in the doped state as either a solution or film. Doped films can be cast directly from solution. The band-gap, obtained from the absorption edge, is ca. 0.86–1.02 eV as the film and 1.14 eV as a CHCl 3 solution. This value of about 0.95±0.1 eV is lower than that of poly(isothianaphthene) and poly(5-decylisothianaphthene), which we report here. It is consistent with theoretical predictions and is one of the lowest band-gaps reported to date. When doped with nitrosonium tetrafluoroborate the films show conductivities of up to 3.6 × 10 −2 S cm −1. Poly(50decylisothianaphthene) {( 1b; poly(5-decylbenzo[c]thiophene)} has been prepared by FeCl 3 oxidation of 5-decyl-1,3-dihyhrobenzo[c]thiophene ( 6). It is a soluble dark blue-black material which forms a light yellow transparent solution when doped.

Lead Scandium Tantalate Thin Films for Thermal Detectors

AbstractThin films of lead scandium tantalate (Pb(Sc½Ta½)03) (PST) have been prepared by a novel modified sol-gel process. The process involves two deposition steps. In the first, layers of amorphous ScTaO4 are deposited by spin coating a solution of metallorganic compounds of scandium and tantalum. A film of lead oxide is then deposited onto the surface using a solution of lead acetate, and the process repeated to obtain thicker films. After firing the composite film, a pale yellow transparent film of PST is obtained. The films are highly orientated and 100% perovskite.The film's electrical properties have been measured against field and temperature, showing a strong induced pyroelectric response (peak value of 3.8 x 10−3C/m2K), peak permittivities of 4500 and low loss. The figure-ofmerit of these films (11 x 10−5Pa−½) indicates a performance equivalent to conventional bulk ceramic pyroelectric wafers prepared by slicing, lapping and polishing of ceramic blocks.