Generation and diagnostics of atmospheric pressure dielectric barrier discharge in argon/air

In this paper, a technique for the determination of electron temperatures and electron densities in atmospheric pressure argon/air discharge by the analysis of optical emission spectra (OES) is reported. The discharge is produced using a high voltage (0-20 kV) power supply operating at a frequency of 27 kHz in parallel electrode system, with glass as dielectric. The dielectric layers covering the electrodes act as current limiters and prevent the transition to an arc discharge. Optical emission spectra in the range of 300 nm to 850 nm have been recorded for the discharge with different inter electrode gap keeping electric field constant. Electron temperature Te and electron density ne have been estimated from electrical and optical methods. Electron density has been calculated using power balance method. The optical methods are related with line intensity ratio from the relative intensities of Ar-I and Ar-II lines in Argon plasma. The electron density calculated by using line intensity ratio method has been compared with the electron density calculated by stark broadening method. The effect of dielectric thickness on plasma parameters has also been studied and it has been found that Te and ne increase as thickness of dielectric decrease for same inter electrode distance and applied voltage

Dependence of dielectric barrier discharge jet length on gas flow rate and applied voltage

The effect of gas flow rate of helium and argon on the length of dielectric barrier discharge (DBD) jet generated under atmospheric pressure using an AC source is investigated. It is found that as the flow rate increases, the jet length increases up to a maximum length. Upon further increase in flow rate, it will cause the jet length to decrease. Visual inspection shows the jet to be of laminar flow when its length was increasing, and gets turbulent when the jet length decreases with increased flow rate. There is an obvious increment in jet length of argon DBD system when the applied voltage is increased from 8.8 kV to 11.0 kV, but not in helium. Spectral analysis reveals the DBD jet to comprise of emission lines of its constituent flow gas. In addition to that, emission lines of component gases (N2 and O) in ambient air and water vapour were also present. Upstream jet was obtained only in helium DBD jet at low flow rate but high applied voltage

Surface modification of polystyrene beads by ultraviolet/ozone treatment and its effect on gelatin coating

Problem statement: Polystyrene failed to provide any reactive functionality of surface hydrophilicity that is capable of binding proteins. It is known that polystyrene must be chemically modified to make its surface amenable to covalent crosslinking with protein. Approach: The aim of this study was to investigate the effects of UV/ozone treatment on gelatin coating. The surfaces of microsize polystyrene beads (150 μm) were modified by UV/ozone treatment system at different treatment time, ozone flow-rate and UV intensity was analyzed by Design expert software. The treated beads were characterized with ATR-FTIR analysis to determine the introduction of carbonyl (-C=O), carboxylic group (-COOH) and amide group (-CO-NH2) onto the polystyrene surface. Sample characterization was also carried out by SEM and densitometer. Gelatin immobilization was then preceded by incubating treated PS sample in gelatin solution and the total amount of gelatin coated on the modified surface was identified by Bradford assay. Results: The maximum amount of gelatin obtained was 63.75 μg mL-1 while the lowest amount obtained for untreated PS (9.947 μg mL-1). The introduction of carbonyl, hydroxyl and amide group on the polystyrene beads surface was confirmed by ATR-FTIR analysis and thus measures the importance of UV/ozone treatment. Conclusion: From the results, it has been found that time is the most significant factor to prepare samples for gelatin immobilization at reduced flow rate and at an increased Ultraviolet (UV) intensity in the ranges of study. © 2010 Science Publications

Relative Thermoluminescence Response of TLD-lOO, TLD-200 and GE-doped Optical Fiber to 8.05 keV X-ray

The responses of three types of thermoluminescence dosimeters (TLDs), namely the TLD-100, TLD-200 and Ge-doped optical fiber to soft X-ray with photon energy of 8.05 keY were measured. The X-ray source used is the vacuum spark plasma which is capable of producing intense coper K" line radiation at energy of 8.05 keY. The output dosage of the vacuum spark X-ray source is measured by a calibrated ion chamber and it is found to increase with operating voltage. The TL sensitivities of TLD-l 00, TLD-200 and Ge-doped optical fiber are determined and results are normalized to their responses to 60CO gamma rays. The TL sensitivities are found to be 1.2 for TLD-100, 29.0 for TLD-200 and 13.8 for Ge-doped Optical Fiber

Sound signatures and production mechanisms of three species of pipefishes (Family: Syngnathidae)

Background. Syngnathid fishes produce three kinds of sounds, named click, growl and purr. These sounds are generated by different mechanisms to give a consistent signal pattern or signature which is believed to play a role in intraspecific and interspecific communication. Commonly known sounds are produced when the fish feeds (click, purr) or is under duress (growl). While there are more acoustic studies on seahorses, pipefishes have not received much attention. Here we document the differences in feeding click signals between three species of pipefishes and relate them to cranial morphology and kinesis, or the sound-producing mechanism. Methods. The feeding clicks of two species of freshwater pipefishes, Doryichthys martensii and Doryichthys deokhathoides and one species of estuarine pipefish, Syngnathoides biaculeatus, were recorded by a hydrophone in acoustic dampened tanks. The acoustic signals were analysed using time-scale distribution (or scalogram) based on wavelet transform. A detailed time-varying analysis of the spectral contents of the localized acoustic signal was obtained by jointly interpreting the oscillogram, scalogram and power spectrum. The heads of both Doryichthys species were prepared for microtomographical scans which were analysed using a 3D imaging software. Additionally, the cranial bones of all three species were examined using a clearing and double-staining method for histological studies. Results. The sound characteristics of the feeding click of the pipefish is species-specific, appearing to be dependent on three bones: the supraoccipital, 1st postcranial plate and 2nd postcranial plate. The sounds are generated when the head of the Dorichthyes pipefishes flexes backward during the feeding strike, as the supraoccipital slides backwards, striking and pushing the 1st postcranial plate against (and striking) the 2nd postcranial plate. In the Syngnathoides pipefish, in the absence of the 1st postcranial plate, the supraoccipital rubs against the 2nd postcranial plate twice as it is pulled backward and released on the return. Cranial morphology and kinesis produce acoustic signals consistent with the bone strikes that produce sharp energy spikes (discrete or merged), or stridulations between bones that produce repeated or multimodal sinusoidal waveforms. Discussion. The variable structure of the sound-producing mechanism explains the unique acoustic signatures of the three species of pipefish. The differences in cranial bone morphology, cranial kinesis and acoustic signatures among pipefishes (and seahorses) could be attributed to independent evolution within the Syngnathidae, which warrants further investigation

Surface modification of polystyrene beads by ultraviolet/ozone treatment and its effect on gelatin coating

Polystyrene failed to provide any reactive functionality of surface hydrophilicity that is capable of binding proteins. It is known that polystyrene must be chemically modified to make its surface amenable to covalent crosslinking with protein. Approach: The aim of this study was to investigate the effects of UV/ozone treatment on gelatin coating. The surfaces of microsize polystyrene beads (150 μm) were modified by UV/ozone treatment system at different treatment time, ozone flow-rate and UV intensity was analyzed by Design expert software. The treated beads were characterized with ATR-FTIR analysis to determine the introduction of carbonyl (-C=O), carboxylic group (-COOH) and amide group (-CO-NH2) onto the polystyrene surface. Sample characterization was also carried out by SEM and densitometer. Gelatin immobilization was then preceded by incubating treated PS sample in gelatin solution and the total amount of gelatin coated on the modified surface was identified by Bradford assay. Results: The maximum amount of gelatin obtained was 63.75 μg mL-1 while the lowest amount obtained for untreated PS (9.947 μg mL-1). The introduction of carbonyl, hydroxyl and amide group on the polystyrene beads surface was confirmed by ATR-FTIR analysis and thus measures the importance of UV/ozone treatment. Conclusion: From the results, it has been found that time is the most significant factor to prepare samples for gelatin immobilization at reduced flow rate and at an increased Ultraviolet (UV) intensity in the ranges of study

Enhanced photoluminescence and Raman properties of Al-Doped ZnO nanostructures prepared using thermal chemical vapor deposition of methanol assisted with heated brass.

Vapor phase transport (VPT) assisted by mixture of methanol and acetone via thermal evaporation of brass (CuZn) was used to prepare un-doped and Al-doped zinc oxide (ZnO) nanostructures (NSs). The structure and morphology were characterized by field emission scanning electron microscopy (FESEM) and x-ray diffraction (XRD). Photoluminescence (PL) properties of un-doped and Al-doped ZnO showed significant changes in the optical properties providing evidence for several types of defects such as zinc interstitials (Zni), oxygen interstitials (Oi), zinc vacancy (Vzn), singly charged zinc vacancy (VZn-), oxygen vacancy (Vo), singly charged oxygen vacancy (Vo+) and oxygen anti-site defects (OZn) in the grown NSs. The Al-doped ZnO NSs have exhibited shifted PL peaks at near band edge (NBE) and red luminescence compared to the un-doped ZnO. The Raman scattering results provided evidence of Al doping into the ZnO NSs due to peak shift from 145 cm-1 to an anomalous peak at 138 cm-1. Presence of enhanced Raman signal at around 274 and 743 cm-1 further confirmed Al in ZnO NSs. The enhanced D and G band in all Al-doped ZnO NSs shows possible functionalization and doping process in ZnO NSs

Synthesis of ZnO Nanowires via Hotwire Thermal Evaporation of Brass (CuZn) Assisted by Vapor Phase Transport of Methanol

Zinc oxide (ZnO) nanowires (NWs) were synthesized using vapor phase transport (VPT) and thermal evaporation of Zn from CuZn. Time dependence of ZnO NWs growth was investigated for 5, 10, 15, 20, 25, and 30 minutes. Significant changes were observed from the field electron scanning electron microscopy (FESEM) images as well as from the X-ray diffraction (XRD) profile. The photoluminescence (PL) profile was attributed to the contribution of oxygen vacancy, zinc interstitials, and hydrogen defects in the ZnO NWs. Raman scattering results show a significant peak at 143 cm−1 and possible functionalization on the wall of ZnO NWs. Growth of ZnO NWs in (0002) with an estimated distance between adjacent lattice planes 0.26 nm was determined from transmission electron microscopy (TEM) analysis

Surface modification of polystyrene beads by UV/Ozone treatment

It is known that polystyrene must be chemically modified to make its surface amenable to covalent cross-linking with protein. The aim of this study was to set up a UV/Ozone system and investigate the effects of UV/Ozone treatment on polystyrene surface. Microsize polystyrene beads with an average size of 150 μm in diameter were treated with and without distilled water at the same treatment time, ozone flow-rate and UV intensity. The treated beads were analyzed by ATRFTIR, SEM, EDX and hydrophilicity measurement. The results show that the hydrophilicity of the surface of polystyrene beads was increased after the UV/ozone treatment and the introduction of carbonyl, carboxyl and hydroxyl groups on the polystyrene beads surface was also confirmed. It was demonstrated that the UV/Ozone system was effective for treatment of polystyrene bead and the best result was obtained without distilled wate