A thickness independent radiochromic film dosimetry system

A new radiochromic thin film dosimeter has been developed for use in radiation processing. The dosimeter's properties are similar to those of the commercially available FWT-60-00 Radiochromic Detectors with three key differences: 1) a lower sensitivity allows reading the optical density at the peak of the absorbtion spectrum (ca. 600 nm) for absorbed doses to over 50 kGy, 2) a radiation-insensitive dye additive allows for automatic thickness correction, and 3) another additive extends to higher doses the agreement between gamma and E-beam calibrations. The dosimeter is analyzed for its sensitivity, temperature and humidity dependencies, stability, reproducibility, and agreement of gamma and E-beam calibrations.     

A new spectrophotometric readout for the alanine-triphenyl tetrazolium chloride system for high-dose dosimetry

The electron spin resonance (ESR) readout of radical concentration in irradiated L-alanine is well known as a transfer dosimetry system, however, the high cost of the ESR equipment is a serious handicap for large-scale routine application. In this study the reaction between irradiated L-alanine powder and aqueous solution of triphenyl tetrazolium chloride (TTC) was studied. The radical produced by irradiation of alanine reacts during the dissolution with TTC forming pink-colored formazans with absorption maxima around 401 and 487 nm. This readout method can be used in the 2–200 kGy dose range.     

A new label dosimetry system

A new label dosimeter which changes its color by large radiation doses has been developed. The green color of the unirradiated dosimeter gradually turns to brown then to red at high doses. The label dosimeter was prepared with a peal-off paper backing, allowing it to stick by self-adhesion to a product box. Three types of dosimeters having different sensitivities to radiation doses were prepared. Correlations were established between absorbed doses and color scale or the green/red axis of the irradiated dosimeters, using a micro color unit equipped with a data station. The data were analyzed to determine the reproducibility of the reflectance measured from the label dosimeters exposed to different doses of γ radiation. These dosimeters showed great stability on extended storage before and after irradiation.Detailed measurements of absorbed dose extremes (D_min and D_max) in product boxes, processed in the Egypt Mega Gamma I radiation processing facility, were obtained using these dosimeters. These dosimeters are currently available in large quantities and are inexpensive, which makes them suitable for routine high-dose applications in radiation processing of materials.     

3–45 MeV/u ion beam dosimetry using thin film dosimeters

Four kinds of film dosimeters well-characterized for low linear energy transfer (LET) radiations were applied to 3–45 MeV/u ions. The dose–responses relative to those for low LET radiations are almost one at a stopping power of about 10 MeV/(mg/cm²) and gradually become smaller with an increase in the stopping power. The overall uncertainty in ion beam dosimetry using these characterized dosimeters is better than ±5% (1σ) including uncertainty in fluence measurement (±2%). Lateral- and depth-dose profile measurements were made using one of the dosimeters (Gafchromic) with a spatial resolution of better than 1 and 10 μm, respectively.     

A new imidazolylquinoline for organic thin film transistor

A new active electronic material, 2-(naphtho[3,4]imidazol-2-yl)quinoline (NIQ), 1, has been synthesized and fully characterized. This compound exhibits field-effect carrier mobility and behaves as a p-type semiconductor (μ_FET = 0.148 cm²/V s at V_DS = 10 V). NIQ and its related imidazolylquinoline compounds may have possible applications as active materials in organic thin film transistors.     

A new dosimetry system using a portable reader

A new dosimeter material has been developed which consists of a radiation sensitive layer on a reflective base, and utilises a portable microdensitometer for response measurement. The instrument, modified from a readily available hand-held unit, is a standard in the printing industry. The system was designed with the demands of ‘in plant’ use in mind, and is equally suitable for either gamma or electron beam irradiation. The dosimeter material develops an easily visible colour change, which is quantitative, highly reproducible and stable over the dose range of approximately 5–45 kGy. The results presented demonstrate the calibration and characteristics of the dosimetry system, and explore some of its potential.     

Enhanced electrothermal pumping with thin film resistive heaters

This work demonstrates the use of thin film heaters to enhance electrothermal pumping in microfluidic systems. Thin film heating electrothermal pumping is more efficient than Joule heating alone. Numerical simulations of an asymmetric electrode array are performed to demonstrate the advantages of incorporating thin film heaters. This specific simulation shows that thin film heater electrothermal pumping provides approximately two and one‐half times more volumetric flow than Joule heating alone for the same input power to both systems. In addition, external heating allows for electrothermal pumping to be applicable to low conductivity media.     

具有宽波反射特性的胆甾相液晶固体薄膜材料的研究

采用两步聚合法得到了具有宽波反射特性的固体胆甾相液晶薄膜,首先通过聚合物稳定胆甾相液晶制备了螺旋结构的高分子网络,然后灌入具有不同螺距的可聚合的胆甾相小分子液晶单体混合物,经紫外光照射聚合后获得了能够反射可见光区(450～780 nm)覆盖红蓝绿三色光的胆甾相液晶固体薄膜.扫描电镜测试结果表明,胆甾相液晶固体薄膜的断面...     

Application of thin film composite membranes to the membrane aromatic recovery system

The membrane aromatic recovery system (MARS) is a new membrane technology which recovers aromatic acids and bases. The first industrial installation has been operating at a Degussa site in the UK recovering cresols since 2002. The state of the art MARS technology employs a tubular silicone rubber membrane. However, this places some limitations on the process due to relatively low mass transfer rates and limited chemical resistance.In this paper, flat sheet composite membranes were investigated for application to the MARS process. In particular for recovery of compounds, such as 1,2-benzisothiazolin-3-one (BIT) which show low mass transfer rates through the current membrane. These composite membranes are comprised of a thin nonporous PDMS selective layer coated on a microporous support layer cast from polyacrylonitrile, polyvinylidene fluoride, polyetherimide or polyphenylenesulphone. The membranes have been characterised using SEM and gas permeation. The mass transfer of BIT through the composite membranes with no chemical reaction enhancement was an order of magnitude higher than through tubular silicone rubber membranes (10⁻⁷ m s⁻¹ versus 10⁻⁸ m s⁻¹). With chemical reaction enhancement, the mass transfer increased by another order of magnitude to 1.6 × 10⁻⁶ m s⁻¹ for BIT through a PVDF supported composite membrane. Mass transfer through the composite membrane was described well using analysis based on the resistance in series theory with chemical reaction. However, when a high osmotic pressure was applied across the membrane (molarity ∼ 3 M), significant water transport occurred across the membrane.     

A spectrophotometric procedure for DNA assay with a micro-sequential injection lab-on-valve meso-fluidic system

A micro-sequential injection spectrophotometric procedure for DNA assay was developed based on the employment of a lab-on-valve (LOV) meso-fluidic analytical system. A small amount of crystal violet solution (10 μl) was de-colored inside the flow cell of the LOV at the presence of 5 μl λ-DNA/HindIII within a certain pH range, and the absorbance decrease of crystal violet solution at 591 nm was measured via optical fibers and was employed as the basis of quantification. A uni-variant approach was adopted for the optimization of experimental parameters, including buffer pH, concentration and volume of crystal violet solution, reaction time and sample/reagent loading flow rates. A linear calibration graph was obtained within 0.2-6.0 μg ml⁻¹, along with a detection limit of 0.07 μg ml⁻¹. The procedure was applied for the determination of λ-DNA/HindIII in synthetic samples in comparison with a documented procedure.     

A flow injection system with ion-exchange for spectrophotometric determination of copper in rocks

A flow injection system is proposed for the spectrophotometric determination of copper in rocks. Samples are mineralized by treatment with hydrofluoric and perchloric acids and the solutions analysed after iron III precipitation. Copper is preconcentrated in a small CHELEX-100 resin column placed in the flow system, eluted with 2.5M nitric acid and further mixed with diethanoldithiocarbamate (DEDC) in basic medium. The coloured complex was monitored at 410 nm. With the proposed system, about 2-30 samples are run per hour with low reagent consumption. Beer's law is followed within 0.04 and 2.00, microg/ml. Precision and accuracy were assessed by using reference rock standards from USGS and GSJ with copper content as low as 0.4 microg/g with good precision and accuracy.     

A comment on emission,reflection and transmission spectroscopy of thin films

General formulaes and working equations in terms of surface reflectivities and internal transmittances are provided for spectroscopy of layered systems. It is demonstrated that band distortions or splitting of intense bands can occur in emission or reflection spectroscopy of concentrated films, but not in transmission. Distortions due to variations in reflectivities near absorption bands can be eliminated employing an opaque sample as the reference. In extreme cases, a colder outer layer may result in split emission bands. This effect also is corrected for by an opaque reference. The theory is substantiated by experimental spectra.     

Thick film traps with an irregular film. Preparation and evaluation

A new method for preparation of sorbent-based ultra-thick film traps for concentration of trace volatile components from gaseous matrices is described. The procedure is based on blowing a prepolymer (polydimethylsiloxane) through a capillary tube, forming an irregular film of stationary phase. Subsequently, the prepolymer is immobilized in a few seconds by heating to 200 degrees C. Evaluation of the performance of the new traps showed that the loss of efficiency, compared to regular smooth film traps is only on the order of 20-30%. In terms of breakthrough volume, this loss in performance is rather insignificant. The technology is extremely simple and allows a rapid and cheap production of a large number of ultra-thick film traps, even in non-specialized laboratories. The method can be applied to any type of cross-linkable stationary phase, thereby expanding the scope of sorbent-based trapping and preconcentration concept. Many applications are anticipated in trace and ultra-trace analysis in a wide range of fields, such as environmental chemistry, polymers, food and process analysis.     

A study on dielectric characteristics of fluorinated polyimide thin film

In this work, the effects of fluorination of polyimide thin films on surface and dielectric characteristics were studied using X-ray photoelectron spectroscopy (XPS) and dielectric spectrometry, respectively. The thermal and mechanical properties of the film were characterized by thermogravimetric analysis (TGA) and tensile strengths, respectively. The fluorine content of the polyimide thin film was increased with increasing treatment concentration, resulting in decreasing dielectric constant of the film. It was found that the replacement of fluorine led to the decrease of the local electronic polarizability of polyimide, or to the increase of the free volume, which can be attributed to the relatively large size of fluorine. Nevertheless, the fluorination did not significantly affect thermal or mechanical properties of the polyimide film under mild conditions in this system.     

吖啶黄荧光光度法测定腺嘌呤

碱性条件下,痕量腺嘌呤使得吖啶黄在激发波长为454 nm、发射波长为509 nm处的荧光强度明显增强,由此建立了荧光光度法测定痕量腺嘌呤的新方法.方法的线性范围为0.2～3.0×10-4 g/L,检出限为1.83×10-5 g/L,方法用于维生素B4片剂中腺嘌呤的测定,回收率为99.6%～101.4%.     

Sulphate adsorption at chemically deposited silver thin film electrodes: time-dependent behaviour as studied by internal reflection step-scan infrared spectroscopy

Stable silver thin films were chemically deposited on a germanium substrate. Ex-situ STM images showed that these films are formed by grains with a diameter between 20 and 100 nm. The silver films have been used as the working electrode in infrared spectroelectrochemical experiments with an internal reflection (Kretschmann) configuration. The adsorption of sulphate anions in neutral or slightly acidic solutions has been studied. The high intensity of the S–O stretching bands in the absorption spectra allowed the monitoring of the time-dependent behaviour of the adsorption/desorption processes in time-domain step-scan experiments.     

Electrokinetics of a poly(N-isopropylacrylamid-co-carboxyacrylamid) soft thin film: evidence of diffuse segment distribution in the swollen state

Streaming current measurements were performed on poly(N-isopropylacrylamid-co-carboxyacrylamid) (PNiPAAM-co-carboxyAAM) soft thin films over a broad range of pH and salt concentration (pH 2.5-10, 0.1-10 mM KCl) at a constant temperature of 22 °C. The films are negatively charged because of the ionization of the carboxylic acid groups in the repeat unit of the copolymer. For a given salt concentration, the absolute value of the streaming current exhibits an unconventional, nonmonotonous dependence on pH with the presence of a maximum at pH ～6.4. This maximum is most pronounced at low electrolyte concentration and gradually disappears with increasing salinity. Complementary ellipsometry data further reveal that the average film thickness increases by a factor of ～2.2 with increasing pH over the whole range of salt concentration examined. The larger the solution salt concentration, the lower the pH value where expansion of the hydrogel layer starts to take place. The dependence of film thickness on pH and electrolyte concentration remarkably follows that obtained for surface conductivity. The streaming current and surface conductivity results could be consistently interpreted on a quantitative basis using the theory we previously derived for the electrokinetics of charged diffuse (heterogeneous) soft thin films complemented here by the derivation of a general expression for the surface conductivity of such systems. In particular, the maximum in streaming current versus pH is unambiguously attributed to the presence of an interphasial gradient in polymer segment density following the heterogeneous expansion of the chains within the film upon swelling with increasing pH. A quantitative inspection of the data further suggests that pK values of ionogenic groups in the film as derived from the streaming current and surface conductivity data differ by ～0.9 pH unit. Such a difference is attributed to the impact of position-dependent hydrophobicity across the film on the degree of ionization of carboxylic sites.     

Electrochromic performance of Zn-Ti-O composite thin film with electrolyte dependence

Zn-Ti-O composite thin film prepared on FTO by sol-gel technique is discovered presenting electrochromic behavior in electrolytes with Li⁺ ion (LiClO₄) and K⁺ (KCl) as well. The observed EC colored/bleached switching is electrolyte dependent which is blue-green/transparent in LiClO₄ and gray-blue/transparent in KCl, respectively. Accordantly, the respective most optical modulation (ΔT) between colored and bleached states is ~?32% (710 nm) in LiClO₄ and ~?37% (600 nm) in KCl. The finding of appreciable steady EC durability with appealing visual optical contrast (ΔT) in conventionally fabricated Zn-Ti-O thin film using with bigger/heavier K⁺ electrolyte helps expanding the applicable components in EC device.     

A new inorganic-organic polymer for the passivation of thin film capacitors

Inorganic-organic polymers with barrier properties against water vapor, excellent electrical data (3, 2, R _D>10¹⁶ cm, E _D up to 400 V/µm) and good adhesion to various substrate materials have been developed. Tailored modifications of these materials provide an excellent protective coating for thin film capacitors. Several mm thick, expensive, encapsulations could be replaced by thin coatings (up to 10 µm). The polymer coating allows the use of thin film chip capacitors in surface-mount technology. As a measure for the efficiency of the coating, the capacitance decrease under controlled humidity has been used. The influence of the material composition, the type of catalyst during sol-gel processing and the curing conditions have been studied. Adhesion and water vapor permeation properties of the polymers and rheological properties of the coating solutions have been investigated. A protective coating is developed, which increases the withstandness of capacitors against humid conditions (90°C, 100% rel. humidity) by a factor of about 30 (compared to uncoated capacitors) and shows no crack formation during thermal cycling.