Hazri Bakhtiar

Photobiostimulation effect on diabetic wound at different power density of near infrared laser

The photobiostimulation effects of near infrared 808 nm diode laser irradiance on diabetic wound were investigated. 120 rats were induced with diabetes by streptozotocin injection. Full thickness punch wounds of 6mm diameter were created on the dorsal part of the rats. All rats were randomly distributed into four groups; one group served as control group, whereas three groups were stimulated daily with unchanged energy density dose of 5 J/cm(2) with different power density, which were 0.1 W/cm(2), 0.2 W/cm(2) and 0.3 W/cm(2) with different exposure duration of 50s, 25s and 17s, respectively. Ten rats from each group were sacrificed on day 3, 6 and 9, respectively. Skin tissues were removed for histological purpose. The contraction of wound was found optimized after exposure with 0.1 W/cm(2). Based on the histological evidence, laser therapy has shown able to promote wound repair through enhanced epithelialization and collagen fiber synthesis. Generally, irradiated groups were advanced in terms of healing than non-irradiated group.

Temperature and Input Energy Dependence of the 946-nm Stimulated Emission Cross Section of Nd 3+ :YAG Pumped by a Flashlamp

The thermal effect on the laser transition at 946 nm is investigated. The temperature of the cooling system is verified in the range 2–60°C. A Nd:YAG laser crystal is utilized as a gain medium and is pumped by a newly developed flashlamp. The variable pumping energy is accomplished within the 5–40 J range. The stimulated emission cross section of the 946-nm line is estimated based on the fluorescence spectrum of the Nd:YAG laser. The stimulated emission cross section of the 946-nm line is found to be inversely proportional to the temperature and to the input energy due to the increase of the thermal population at the ground level.

Effect of green laser irradiation on hydrogen production

The effect of green laser irradiation on hydrogen production via water electrolysis was investigated. Diode pumped solid-state laser operating in second harmonic generation was employed as a source of irradiation. The hydrogen production system was also irradiated by a conventional light, a halogen source, for comparison. The best catalyst was identified by mixing distilled water with two types of salt: NaCl and Na2SO4. Optimization of hydrogen production from water electrolysis was realized by using NaCl and green laser irradiation. The power of green laser irradiation and the concentration of NaCl in water contribute to hydrogen production. The hydrogen yield also depends on the distance and direction of the green beam to the electrode.

Effects of temperature and input energy on a quasi-three-level emission cross section of Nd3+:YAG pumped by a flashlamp

The influence of temperature and input energy on the fluorescence emission cross section of Nd3+:YAG crystal is studied. The stimulated emission cross sections of quasi-three-level systems are determined in a temperature range from −30 to 60°C and an input energy range from 18 to 75 J. The cross section is found to be decreased when the temperature and the input energy are increased. This is attributed to the thermal broadening mechanism of the emission line. This study is relevant for the development of laser design.

Sol–gel based thermally stable mesoporous TiO2 nanomatrix for fiber optic pH sensing

AbstractThermally stable acid catalyzed mesoporous titania (TiO2) nanomatrices are obtained by sol–gel method for fiber optic pH sensing. These synthesized nanoparticles are annealed at 300 °C, at two time intervals i.e., 1 h and 2 h, characterized with several analytical techniques such as FE-SEM/EDS, AFM, XRD, FTIR, TGA, and Brunauer–Emmett–Teller (BET) analysis. Microscopic analysis shows that synthesized nanoparticles have crack-free, dense and homogeneous surface with low surface roughness (4.4–5.9 nm). EDS mapping confirms the uniform distribution of Ti in all samples. XRD findings revealed the TiO2 anatase phase. BET analysis shows that the mesoporous synthesized TiO2 nanoparticles have surface areas 169 m2/g and average pore diameter 39.2 Å. However, surface area is decreased to 113 and 102 m2/g and average pore diameter increased up to 62.36 and 68.18 Å after 1 h and 2 h heat treatment, respectively. Furthermore, the sensing activity of phenolphthalein (phph) doped mesoporous TiO2 nanoparticles/matrix is found to be high at pH 12 without any leaching/cracking.

Synthesis and Characterization of Gold-Silver Nanoparticles in Deionized Water by Pulsed Laser Ablation (PLAL) Technique at Different Laser Parameter

Gold and silver nanoparticles (NPs) are physically synthesized using Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG)-pulsed laser ablation in liquid (PLAL) technique which is a rapid, s...

Thermal stress effect in diode end-pumped Nd:YVO4 bar laser

The thermal stress effect on various doping levels of yttrium vanadate crystal Nd:YVO4 is investigated. Diode end-pumped source was used to obtain the input-output characteristics of the vanadate crystal. The laser performance of the low doping crystal is poor since the optical conversion efficiency is small and high threshold pump power. However the low Dopant crystal is not associated with thermal stress thus no thermal damage. Differently with higher concentration of Nd ions crystal, the laser performance is relatively high but it is accompanied with thermal damage which comprised of microcrack, microfracture and contamination. The high absorption on the doping ions with additional external impurities causes extra heat generation which leads to thermal fracture.

Prominent 946 lines induced from flashlamp pumped Nd: YAG rod

Spectroscopic properties of Nd:YAG laser rod pumped by a new developed flashlamp is investigated. A new power supply is constructed to power xenon flashlamp. A 1 at.% Nd:YAG laser rod is transversely pumped by the flashlamp and stabilized by a water cooling system operated at ambient temperature of 20°C. The absorption and emission spectrum of the flashlamp pumped Nd:YAG rod is analyzed via spectroscopy technique. The peak absorption line is identified to be at 882 nm. The dominant emission line obtained from transition 4F3/2→4I9/2 comprised of quasi three level laser at 938.5 and 946 nm with the corresponding cross section of 2.42×10−19cm2 and 3.04×10−19cm2 respectively. This cross section is found almost ten times greater than the usual one.

Embedded Sensor for Detecting Corrosion of Reinforcement in Concrete

Corrosion of reinforcement is a worldwide problem which causes premature degradations in reinforced concrete structures. Monitoring reinforcement corrosion in concrete can be achieved by embedding corrosion sensor within the concrete cover. In this research, capacitance-based embedded sensor was developed to monitor corrosion potential (Ecorr) and corrosion rate (Icorr) parameters of reinforcement continuously. The sensors were tied to the reinforcement and embedded in concrete slab specimens followed by immersion into NaCl solution for 70 days. During this period, corrosion parameters were weekly recorded. At the same time, half-cell corrosion testing using Portable SRI-CMIII was conducted for calibration purpose. From the research, it was observed that the patterns of Ecorr and Icorrshown by the embedded sensors were similar to that of portable SRI-CMIII device - an indication of suitability of the embedded sensor towards sensing existing corrosion activities around the embedded steel bars. Eventually, the bars were found corroded from the broken specimens to confirm the detection of corrosion activities as recorded by the sensors.

Characterization of ionizing radiation effects in MOS structures by bipolar operation study

This work presents a method to characterize transistors of submicron dimensions. The study of the substrate-drain junction of transistors before and after irradiation shows that irradiation induces junction electrical parameters changes due to surface potential action on the space-charge region. Variations of the current gain of the bipolar transistor (drain-substrate-source as emitter-base-collector) for different gate voltages are analyzed and compared to dose effects on the oxide.