Investigation on Slicing Behavior of Single Crystal Silicon Wafer in AWJM and Influence of Micro Dimple Textured Surface for Solar Applications

Silicon - The current investigation focuses on the slicing characteristics of silicon, a hard and brittle solid that is very difficult to cut, with abrasive water jet machining (AWJM) process by...     

Low-cost synthesis of nano-hydroxyapatite from carp bone waste: Effect of calcination time and temperature

The aim of this study was to synthesize Hydroxyapatite (HA) from carp bone waste by calcination treatment. The effects of calcination temperature and time on crystallite size, crystallinity%, powder size and morphology, formed phases, and Ca/P ratio were analyzed. The XRD analyses indicated that for 1 h calcination time, HA was the only phase produced at all temperatures. However, for 5 h calcination time, temperatures other than 700ºC resulted in formation of TCP+HA. The HA obtained at 700ºC at both times had less crystallinity compared to other temperatures. Crystallite size increased by increase in temperature at 1 h calcination time. The smallest and largest particulate sizes were obtained at 800ºC for 1 h and 900ºC for 5 h, respectively. The Ca/P ratio close to theoretical value (1.67) was obtained for 5 h calcination time. Finally, the results showed the usefulness of the methodology used in natural HA production that can be used in orthopedics and dentistry.     

Severe and unexpected occurrence of water-electrolyte disorders in the postoperative period

Paradoxical cerebral embolism (PCE) through a patent foramen ovale (PFO) should be considered as a cause of ischemic stroke, particularly in young patients without an alternative cause for stroke. PCE is even more important that it is potentially treatable. However, PCE remains often presumed because it rests upon the rarely demonstrated findings of a deep venous thrombosis and a thrombus lodged in the PFO. Recent studies have shown a rather low stroke recurrence rate in patients with PFO and stroke but suggest that some subgroups of patients with a higher stroke recurrence risk-exist according clinical, echocardiographical and radiological characteristics. For these subgroups, it seems that a more invasive treatment should be required. There are four therapeutic options; antiaggregants, anticoagulation, transcatheter closure of PFO, and surgical closure of PFO. However, these treatments have yet to be evaluated in clinical trials.     

Structural,morphological, optical and electrical properties of spray deposited zinc doped copper oxide thin films

Nanostructured spray deposited zinc (Zn) doped copper oxide (CuO) thin films were characterized by employing X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), atomic force microscopy (AFM) and ultraviolet–visible–near infrared (UV–Vis–NIR) spectroscopy. XRD patterns of CuO and Zn doped CuO thin films indicated monoclinic structure with the preferred orientation along \(\left( {\bar 111} \right)\) plane. Maximum value of crystallite size is found about 28.24 nm for 5 at% Zn doped CuO thin film. In FESEM images, nanoparticles were observed around the nucleation center. EDX analysis confirms the presence of all component elements in CuO and Zn doped CuO thin films. Analysis by AFM of CuO and Zn doped CuO thin films figured out decrease of surface roughness due to Zn doping. UV–Vis–NIR spectroscopy showed that CuO and Zn doped CuO thin films are highly transparent in the NIR region. Optical band gap of CuO thin films decreased with substrate temperature and that of Zn doped CuO thin films increased with Zn concentration. Refractive index of CuO and Zn doped CuO thin films raised with photon wavelength and became constant in the NIR region. 5 at% Zn doped CuO thin film showed the highest optical conductivity and the lowest electrical resistivity at room temperature.     

Preparation and characterization of porous scaffold composite films by blending chitosan and gelatin solutions for skin tissue engineering

Biodegradable polymers have significant potential in biotechnology and bioengineering. However, for some applications, they are limited by their inferior mechanical properties and unsatisfactory compatibility with cells and tissues. In the present investigation blends of chitosan and gelatin with various compositions were produced as candidate materials for biomedical applications. Fourier transform infrared spectral analysis showed good compatibility between these two biodegradable polymers. The composite films showed improved tensile properties, highly porous structure, antimicrobial activities, low water dissolution, low water uptake and high buffer uptake compared to pure chitosan or gelatin films. These enhanced properties could be explained by the introduction of free ? OH, ? NH₂ and ? NHOCOCH₃ groups of the amorphous chitosan in the blends and a network structure through electrostatic interactions between the ammonium ions (? NH³⁺) of the chitosan and the carboxylate ions (? COO^?) of the gelatin. Scanning electron microscopy images of the blend composite films showed homogeneous and smooth surfaces which indicate good miscibility between gelatin and chitosan. The leafy morphologies of the scaffolds indicate a large and homogeneous porous structure, which would cause increased ion diffusion into the gel that could lead to an increase in stability in aqueous solution, buffer and temperature compared to the gelatin/chitosan system. In vivo testing was done in a Wistar rat (Rattus norvegicus) model and the healing efficiencies of the scaffolds containing various compositions of chitosan were measured. The healing efficiencies in Wistar rat of composites with gelatin to chitosan ratios of 10:3 and 10:4 were compared with that of a commercially available scaffold (Eco‐plast). It was observed that, after 5 days of application, the scaffold with a gelatin to chitosan ratio of 10:3 showed 100% healing in the Wistar rat; however, the commercial Eco‐plast showed only a little above 40% healing of the dissected rat wound. Copyright © 2012 Society of Chemical Industry     

Preparation and characterization of poly (ethylene glycol) grafted Ca-alginate fibers by γ-irradiation for biomedical applications

Radiation processing, being a physical process, is an environmentally friendly alternative to chemical modifications. It is economically viable, safe, and possesses several advantages over other conventional methods employed for modification and grafting. To improve the physico-mechanical properties of Ca-alginate fiber (CaAF), poly (ethylene glycol) (PEG) was grafted by applying γ-radiation of different intensities. The effect of γ-irradiation on the physico-mechanical, thermal, morphological, thermal and water aging, water, and simulated body fluid (SBF) uptake were evaluated. FT-IR results confirmed that PEG was successfully grafted onto Ca-alginate fibers by γ-irradiation. From the detailed experimental results, irradiation doses and PEG concentration were optimized for grafting processes. The results showed that 50% PEG and 2.5?kGy irradiation dose yielded the highest tensile strength. Differential scanning calorimetric (DSC) analysis showed that with increasing γ-intensity a decrease of dehydration temperature of the fibers had occurred. On the other hand, the glass transition temperature (T _g) increased with increasing irradiation dose. The tensile cracked surfaces of the grafted alginate fibers were analyzed by scanning electron microscope (SEM) in order to monitor their surface morphologies. The SEM images of the cracked surfaces demonstrated that spherical shape rods were present for irradiated fiber sample while no such rods were observed for non-irradiated fibers. The characteristic data obtained from SBF and water uptake, and water and thermal aging experiments indicated that CaAF grafted with 50% PEG by applying 2.5?kGy γ-irradiation can be potentially employed for biomedical purposes, such as surgical suture.     

Pervaporative aroma compounds recovery from lemon juice using poly(octyl methyl siloxane) membrane

BACKGROUND: In this research, a pervaporation process was used to recover volatile aroma compounds from lemon juice using a poly(octyl methyl siloxane) membrane. The majority of previous studies have been with binary model feed systems, while the results with actual feed mixtures did not always match those with model feeds. In order to successfully optimize the pervaporation process, it is essential to work with actual fruit juice. The influences of various operating parameters such as feed flow rate, feed temperature and permeate pressure on the permeate flux and selectivity were investigated. For this purpose, three compounds that make a significant contribution to lemon juice aroma, namely, α‐pinene, β‐pinene and limonene were studied. RESULTS: It was shown that decreasing the permeate pressure increased both permeation flux and enrichment factor, while an increase in feed temperature increased the water flux more significantly than the aroma compounds flux, resulting in lower enrichment factor. Also, the results indicated that feed flow rate had no significant effect on the performance of the process. CONCLUSION: The membrane used was found to be very selective towards α‐pinene, β‐pinene and limonene. It can be concluded that pervaporation is an attractive technology for the recovery of lemon aroma compounds as it yields good separation and operates under mild conditions. Copyright © 2010 Society of Chemical Industry     

Rough rice convective drying enhancement by intervention of airborne ultrasound – A response surface strategy for experimental design and optimization

This study has examined the influence of ultrasonic-assisted hot air drying process on the dehydration behavior of in-bin rough rice (Oryza sativa) kernels. To this aim, the experimental drying kinetics of rough rice subjecting to different drying air temperatures (35, 40, 45, 50, and 55?°C) and inlet air velocities (0.2, 0.5, 0.8, 1.1, and 1.4?m/s) were carried out by applying various ultrasound power levels (30, 60, 90, 120, and 150?W) in the frequency of 21?kHz. The effect of ultrasound intervention was investigated on drying kinetics, effective moisture diffusivity, energy consumption, and product quality. Experimental plans were designed by response surface method to study the feasible interactions between research parameters. Based on the key results, high-power ultrasound in conjunction with conventional deep bed drying led in 26.47% decrease in drying time, 30.66% increase in moisture diffusivity, as well as improvement in the grain quality, in terms of acceptable reduction in head rice yield and whiteness losses. In addition, energy consumption reduced approximately by 24.36% when high-power ultrasound was applied at selected drying condition. Ultrasound intervention during hot air drying process is recommended as it generates rice kernels with desirable milling quality within shorter drying time.