பொருள் அறிவியல் & பொறியியல் இதழ்

Osteoinductive and antiosteroporotic phenomena could be created by using synthetic biomaterials for applications in bone surgery.
In the present study, CH-based bioactive glass (BG-CH) with 17 wt% chitosan was elaborated by a freeze-drying process. BG-CH was implanted in the muscle and in the femoral condyles of ovariectomised rats. Grafted tissues were carefully removed for physico-chemical and histological analysis.
Several physic-chemical techniques (XRD, FT-IR, MEB, ICP-OES and NMR) were employed to highlight the effects of chitosan on the glass matrix before and after implantation.
The results of the study show that despite the non-additional osteogenic cells or agents, BG-CH is endowed with an osteoinductive property. After 8 weeks, 13C NMR spectra showed the characteristic signals of γ-carbons of the hydroxyproline (71 ppm) abundant in collagen.
γ-carboxyglutamate (55 ppm), which occurs in several other bone proteins like osteocalcin, indicating the BGCH degradation and the dominance of the bone tissue formation. Moreover, this study showed a rise in Ca and P ion concentrations in the implanted microenvironment, leading to the formation/deposition of Ca-P phases. Trace elements such as Zn and Fe were detected in the newly-formed bone and involved in the bone healing. The study highlights the suitability and the extensive applications of BG-CH composites and the clinically useful therapy in regenerative medicine.

Cadmium is an established toxic metal with its ability to accumulate in blood, liver and kidney. It adversely affects the renal cortex and ultimately leads to the renal failure. It has been reported that deficiency of certain dietary components affects cadmium toxicity. Present study was designed to evaluate the cadmium toxicity (50 ppm in drinking water) in protein malnourished group (8%) and on normal protein (21%) diet groups. It was found that Cd exposure led to marked elevation in alkaline phosphatase, acid phosphatase, glutamic pyruvic transferase, glutamic oxaloacetic acid transferase with significant increase in protein malnourished group (p 0.005).
Same trend of result was noted in urinary concentration of alpha amino acid, albumin, total protein and glucose. Results were more significant (p 0.001) in malnourished animals. However, hepatic and renal enzymes showed depletion in all groups. There was marked increase in serum enzymes GOT, GPT, alkaline phosphatase, acid phosphatase in low protein diet + Cd (p 0.001).
Hence present findings strongly support that protein under-nutrition predisposes the organism to the deleterious effects of cadmium toxicity.

The effluents of wastewater in some industries such as, textiles, leather, paper and plastics contain various kinds of synthetic dyes. Molecular sieves like aluminosilicate or aluminophosphate materials containing tiny pores of precise and uniform size, which are used as adsorbents, catalyst carriers, desiccants, and so on. In this work, initial dye concentration, contact time, adsorbent dosage, pH and kinetic studies were carried out to evaluate the adsorption capacity ZnAPSO-34 nanoporous material for the removal of MB from aqueous solutions. The results showed that ZnAPSO-34 could be employed as an alternative for the removal of dyes and colors from aqueous solutions.

The processing of TiO₂ semiconducting materials has a long route with numerous contributing variables. The binder plays an important role in the development of this electro-ceramic material. Higher density and strength of a green body are critical not only for handling at its green state but also to avoid the causes of flaw formation during sintering. Use of appropriate binder can lead to improve characteristics of powder which will reduce density gradient in the green body during compaction. Enhanced green properties can consequently lead to higher fired strength of the varistor discs. The binder system is anticipated to have an influence on the grain growth and microstructure which in turn affect the electrical performance. To investigate this phenomenon, TiO₂ powder doped with 0.2% of Ta₂O₅ was processed with and without binder polyvinyl alcohol. The prepared samples were characterized by evaluating the physical properties like green density, fired density, axial and radial shrinkage, micro hardness and compressive strength. It was observed that TiO₂ processed with binder exhibited better properties compared to powder processed without binder. The higher percent of binder enhanced the properties further. XRD revealed that the diffraction angle peak was similar to that of pure TiO₂. SEM analysis indicated that the average grain size was larger for discs prepared with higher percent of binder. It is anticipated that the larger grain size will improve varistor properties in terms of low voltage applications.

Silicon, tin and lead powders belong to group IV in periodic table and exhibit decreasing semi conducting nature towards the bottom of the group. These are very useful in producing non ferrous powder metallurgy components.
In the present investigation silicon, tin and lead powders are exposed to bio field. Both the exposed and unexposed powders are later characterized by various techniques. The average particle size, after an initial decrease is found to increase with increase in number of days after treatment although the size is lee than that exhibited by untreated powder, suggesting the operation of competing mechanisms fracture and sintering. The BET surface area increased slightly in silicon powder but did not change in tin and lead powders. SEM photographs showed that samples exposed to bio field after 20 days showed fracture paths and fractures at inter and intra particle boundaries in treated powders. Thermal analysis indicated a decrease in heat of reaction and decrease in mass in treated samples.
X-ray diffraction of the powder samples indicated both increase and decrease in crystallite size, unit cell volume and molecular weight of samples exposed to bio field even after 179 days.
These results indicate that the properties of the metallic powders can be controlled even up to atomic level by exposing to bio field.

Severe Plastic Deformation (SPD) process is capable of developing the submicron grain structures in metallic alloys and to improve the Mechanical properties. Constrained groove pressing is a processing method in which a metal is subjected to an intense plastic deformation through repeated dominant shearing and pressing (flatting) of plate. This method comprises bending of straight billet with corrugated tools and the restoring the straight shape of the slab with flat tools. The repetition of the process is required to obtain a large strain and desired structural changes. The Constrained Groove Pressing (CGP) processes are widely used in industries to compensate the high strength metal plates components used in automobiles. In the present work an attempt has been made to study the influence of CGP parameters like strain rate and number of passes to predict the degree of importance on grain size, micro hardness and tensile strength of CGP specimens. The results indicated that the number of passes has a major influence on the fine-grain refinement followed by strain rate.

A material for hermetically-sealed casing of multichip subsystem needs the characteristics such as high thermal conductivity, low density, low thermal expansion coefficient, automatic sealing, simplicity and convenience of subsequent application workmanship .The material that is mostly suitable to be used is Al-50% Si compound material prepared by the spray deposition method. The powder metallurgy process (PM) was studied for preparing the Al-Si compound material in this paper.The median particle size of the Al-Si powder must be less than 5μm. The ball-milling technique was adopted to reduce the particle size of Al-Si powder. The result shows: the change in ball-milling speed affects the particle size of Al-50 Si powder greatly and the increase of rotating speed can facilitate powder fining and homogenization. By determining other process parameters, it is found the ball-milling time is the major factor affecting the particle size. As the ball-milling time extends, the particle size reduces. Compared to the dry milling process, the alcohol wet milling process can improve the fine powder output, reduce particle size distribution range, avoid powder agglomeration and get good homogenization. Less particle size also result in higher density and less Si phase particle size in Al-50 Si compound. In the following condition, namely the ratio of grinding media to material is 5:1, the rotating speed 350 rpm and ball-milling time 20 hrs, the median particle size of Al-50 Si powder is 4.64μm.