Modification of silicon carbide fibers for use in SiC/Ti composites

The degradation of silicon carbide fibers during exposure to conditions typical of composite fabrication was investigated. The tensile strength of pristine fibers and fibers sputtered with thin metal coatings were determined before and after treatment at 870 C for one hour in vacuum. Each fiber strength distribution was related by an analytical procedure to a projected composite ultimate tensile strength (PC UTS). The results indicate that a thin aluminum diffusion barrier can yield a 150 percent increase in PC UTS over the baseline SiC/Ti system

Inflaton Decay in an Alpha Vacuum

We study the alpha vacua of de Sitter space by considering the decay rate of the inflaton field coupled to a scalar field placed in an alpha vacuum. We find an {\em alpha dependent} Bose enhancement relative to the Bunch-Davies vacuum and, surprisingly, no non-renormalizable divergences. We also consider a modified alpha dependent time ordering prescription for the Feynman propagator and show that it leads to an alpha independent result. This result suggests that it may be possible to calculate in any alpha vacuum if we employ the appropriate causality preserving prescription.Comment: 16 pages, 1 figure, Revtex 4 preprin

VALIDATED SPECTROPHOTOMETRIC METHOD FOR THE DETERMINATION OF CHLORAMPHENICOL IN PURE AND IN ITS DOSAGE FORM

A simple, précis, rapid sensitive and accurate spectrophotometric methods have been developed for the estimation of Chloramphenicol UV in pure form and its pharmaceutical formulations based on oxidative coupling reaction UV with MBTH reagent at P H-4 which is extractable at 620 nm. Beer's law is obeyed in the concentration range 1-6 ml (10-60 µgml-1). The developed method was applied directly and easily for the analysis of the pharmaceutical formulations. RSD was found to be 0.0194 % and recovery 99.73%. The method was completely validated and proven to be rugged. The interferences of the ingredients and excipients were not observed. The repeatability and the performance of the proved method were established by point and internal hypothesis and through recovery studies.Keywords: Spectrophotometry, Chloramphenicol, MBTH, Oxidative coupling

VALIDATED SPECTROPHOTOMETRIC METHOD FOR THE DETERMINATION OF CHLORAMPHENICOL IN PURE AND IN ITS DOSAGE FORM

Objective: A simple, economic, selective, precise, and accurate UV-Visible spectrophotometric method for the analysis of Chloramphenicol in bulk drug and pharmaceutical formulations was developed and validated in the present study. Methods: Based on oxidative coupling reaction with MBTH reagent at PH-4.5 which is extractable at 620 nm. The Beer's law is obeyed in the concentration range 1-6 ml (10-60 µg ml-1). Results: The RSD was found to be 0.0194% and recovery is 99.73%. The method was completely validated and proven to be rugged. The interferences of the ingredients and recipients were not observed. The repeatability and the performance of the proved method were established by point and internal hypothesis and through recovery studies. Conclusion: The method was found to be accurate and precise, as indicated by recovery studies close to 100 and % RSD is not more than 2. The summery of validation parameters of proposed UV-Visible method is given

Electro-Mechanical Actuator: A Simulation Study

Electro-Mechanical Actuator (EMA) modeling and simulation using Simulink block set has been implemented and tested with input step and repeated sequences. The results obtained from this simulation are satisfactory. This simulation model can be used for developing EMA health condition monitoring techniques and educational purpose. Basically a simplified and complete Simulink based approach is presented

Lipid profile alterations and fasting blood glucose levels in primary hypothyroidism

Background: Hypothyroidism has become a highly prevalent condition worldwide as well as in India. Females are affected more than men and dyslipidemia has been associated with hypothyroidism. This study was conducted to study the prevalence and pattern of dyslipidemia in hypothyroid patients and to justify the screening of lipid profile in hypothyroid patients.Methods: This was a case control study which included 50 newly diagnosed and untreated hypothyroid patients and 50 healthy individuals in the age group of 20-40years. Free Triiodothyronine (FT3), free thyroxine (FT4), Thyroid Stimulating Hormone (TSH) were estimated by chemiluminiscence immunoassay.Serum total cholesterol (TC), triglycerides (TG), high density lipoprotein cholesterol (HDL-C), blood glucose were done in all the subjects by enzymatic colorimetric method. Low density lipoprotein cholesterol (LDL-C) was calculated using Friedwalds formula. Very Low density lipoprotein cholesterol (VLDL-C) was calculated from the triglyceride value.Results: Lipid profile alterations were seen in hypothyroid patients. The mean (standard deviation)values of Total cholesterol, high density lipoprotein cholesterol (HDL-C), Low density lipoprotein cholesterol (LDL-C), Very Low density lipoprotein cholesterol (VLDL-C), triglycerides (TG), Fasting blood glucose were 183.7 (32.9), 38.12 (7.59), 104.4 (29.42), 31.66 (13.09), 158.44 (65.61), 95.9(9.9) mg/dl respectively. The statistical analysis showed that the difference in the above values between cases and controls was significant and all the mean values except HDL-C were increased in cases.Conclusions: Hypothyroid patients demonstrate significant increase in serum lipids as compared to healthy individuals. More females are diagnosed with hypothyroidism and dyslipidemia is associated with primary hypothyroidism.

Novel phytosynthesis of nanoparticles using Indigeneous Australian Plants

Nanoparticles are considered to be the building blocks of nanotechnology. Biosynthesis of nanoparticles using plant material is an exciting and relatively new developing research area in nanobiotechnology. In the present study, Eucalyptus leaves were collected from Olive pink botanical garden, Alice Springs, Australia and were used to synthesize silver nanoparticles. Cubical structured and well monodispersed silver nanoparticles were formed with an average size of 50nm. The formed silver nanoparticles are found to have promising applications in medicine as good antimicrobial agents. To the best of our knowledge this is the first report on exploiting indigeneous Australian plant sources for the synthesis of metallic nanoparticles

Mechanism of phosphorescence quenching in photomagnetic molecules determined by positron annihilation spectroscopy

Platinum Octaethyl Porphyrin (Pt.OEP) is an efficient phosphor under ultraviolet excitation. The phosphorescent triplet state (T(sub 1)) is readily quenched by the oxygen (O2) molecules. This phenomenon is being utilized as the basis for global air pressure measurements in aerodynamic facilities at various laboratories. The exact mechanism by which O2 molecules quench the (T(sub 1)-S(sub 0)) transitions is still unknown. The diamagnetic S(sub n) singlet states, which feed T(sub 1) states via intersystem crossings, would presumably not be affected by O2. It must be the magnetic T(sub 1) states, which can interact with the paramagnetic O2 molecules, that are affected. However, our positron lifetime and Doppler broadening studies suggest the formation of (S(sub n).02) complexes which can also eventually reduce the population of the T(sub 1) states (i.e. quench phosphorescence). This is possible since higher triplet states in (Pt-OEP) are admixed with the S(sub n) states via spin orbit interactions. The experimental procedures and the results of various measurements are discussed in this paper

Mechanism of phosphorescence quenching in photomagnetic molecules determined by positron annihilation spectroscopy

Platinum Octaethyl Porphyrin (Pt.OEP) is an efficient phosphor under ultraviolet excitation. The phosphorescent triplet state (T(sub 1)) is readily quenched by the oxygen (O2) molecules. This phenomenon is being utilized as the basis for global air pressure measurements in aerodynamic facilities at various laboratories. The exact mechanism by which O2 molecules quench the (T(sub 1) - S(sub 0)) transitions is still unknown. The diamagnetic S(sub n) singlet states, which feed T(sub 1) states via intersystem crossings, would presumably not be affected by O2. It must be the magnetic T(sub 1) states, which can interact with the paramagnetic O2 molecules, that are affected. However, our positron lifetime and Doppler broadening studies suggest the formation of (S(sub n) central dot O2) complexes which can also eventually reduce the population of the T(sub 1) states (i.e. quench phosphorescence). This is possible since higher triplet states in (Pt.OEP) are admixed with the S(sub n) states via spin orbit interactions. The experimental procedures and the results of various measurements are discussed in this paper

Effect of graphite particulate on mechanical characterization of hybrid polymer composites

Quest for producing lightweight and biodegradable materials has encouraged researchers to replace synthetic fibers with natural fibers. Hence a study is made to investigate the effects of introducing secondary reinforcement (natural fibers), stacking sequence, and addition of graphite particles on the mechanical characteristics and water uptakes along with diffusivity of hybrid (glass\jute) composites. Different weight fractions of graphite particulates are incorporated into the epoxy to produce different samples having 4 plies for each sample by hand layup vacuum bagging method. The obtained specimens are subjected to various mechanical tests, water absorption tests as per the ASTM standards, and optical microscopy was used to study the fracture morphology of the samples. The results displayed that the properties are deteriorated a little with the addition of secondary reinforcement, however they have improved with the addition of graphite. E-Glass as skin layer and treated jute as core layer composite exhibits ameliorate tensile strength (201.5 MPa), compression strength (515.12 MPa), flexural strength (106.9 MPa), hardness (25 BHN). However highest impact energy of 26 J is recorded for the sample with jute as skin layer and E-Glass as the core layer. Water absorption tests revealed that the addition of graphite has reduced the water absorption in the hybrid samples