Kelothu Suresh

Mechanistic investigations in sono-hybrid techniques for rice straw pretreatment.

This paper reports comparative study of two chemical techniques (viz. dilute acid/alkali treatment) and two physical techniques (viz. hot water bath and autoclaving) coupled with sonication, termed as sono-hybrid techniques, for hydrolysis of rice straw. The efficacy of each sono-hybrid technique was assessed on the basis of total sugar and reducing sugar release. The system of biomass pretreatment is revealed to be mass transfer controlled. Higher sugar release is obtained during dilute acid treatment than dilute alkali treatment. Autoclaving alone was found to increase sugar release marginally as compared to hot water bath. Sonication of the biomass solution after autoclaving and stirring resulted in significant rise of sugar release, which is attributed to strong convection generated during sonication that assists effective transport of sugar molecules. Discrimination between individual contributions of ultrasound and cavitation to mass transfer enhancement reveals that contribution of ultrasound (through micro-streaming) is higher. Micro-turbulence as well as acoustic waves generated by cavitation did not contribute much to enhancing of mass transfer in the system.

Synthesis and characterization of exfoliated PMMA/Co–Al LDH nanocomposites via solvent blending technique

The main aim of the present work is to examine the effect of Co–Al layered double hydroxide (LDH) concentration on the structural, thermal and rheological properties of poly(methyl methacrylate) (PMMA) nanocomposites. PMMA/Co–Al LDH nanocomposites were prepared by dispersing organically modified Co–Al LDH in the PMMA matrix via a solvent blending technique using methylene chloride as a solvent. The resultant samples were analyzed by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The XRD and TEM results confirm the formation of exfoliated PMMA nanocomposites. The PMMA/LDH nanocomposites demonstrate higher thermal stability as compared to pristine PMMA. When 15% weight loss is selected as a point of consideration, the degradation temperature of PMMA/LDH nanocomposites containing 7 wt% of Co–Al LDH is 25 °C higher than that of pristine PMMA. The glass transition temperature (Tg) of PMMA nanocomposites is about 2–4 °C more than for pristine PMMA. The thermal degradation kinetics of different nanocomposites is also determined. The rheological studies elucidate that complex viscosity, storage and loss modulus diminish with increasing temperature from 150 to 190 °C.

Investigation of Structural, Rheological and Thermal Properties of PMMA/ONi-Al LDH Nanocomposites Synthesized via Solvent Blending Method: Effect of LDH Loading

This article addresses the synthesis of organically tailored Ni-Al layered double hydroxide (ONi-Al LDH) and its use in the fabrication of exfoliated poly(methyl methacrylate) (PMMA) nanocomposites. The pristine Ni-Al LDH was initially synthesized by co-precipitation method and subsequently modified using sodium dodecyl sulfate to obtain ONi-Al LDH. Nanocomposites of PMMA containing various amounts of modified Ni-Al LDH (3 wt%-7 wt%) were synthesized via solvent blending method to investigate the influence of LDH content on the properties of PMMA matrix. Several characterization methods such as X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), rheological analysis, differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA), were employed to examine the structural, viscoelastic and thermal properties of PMMA/OLDH nanocomposites. The results of XRD and TEM examination confirm the formation of partially exfoliated PMMA/OLDH nanocomposites. The FTIR results elucidate that the characteristic bands for both pure PMMA and modified LDH are present in the spectra of PMMA/OLDH nanocomposites. Rheological analyses were carried out to examine the adhesion between polymer matrix and fillers present in the nanocomposite sample. The TGA data indicate that the PMMA nanocomposites exhibit higher thermal stability when compared to pure PMMA. The thermal decomposition temperature of PMMA/OLDH nanocomposites increases by 28 K compared to that of pure PMMA at 15% weight loss as a point of reference. In comparison with pure PMMA, the PMMA nanocomposite containing 7 wt% LDH demonstrates improved glass transition temperature (Tg) of around 3 K. The activation energy (Ea), reaction orders (n) and reaction mechanism of thermal degradation of PMMA/OLDH nanocomposites were evaluated using different kinetic models. Water uptake capacity of the PMMA/OLDH nanocomposites is less than that of the pure PMMA.

Mesenchymal Chondrosarcoma of Posterior Maxilla: Report of a Case with Brief Literature Review

Mesenchymal chondrosarcomas (MCs) are infrequent, slow-growing malignant tumors of head and neck region affecting both bone and soft tissues. It represents approximately 1% of all chondrosarcomas. They usually occur in the middle aged individuals, but rarely seen in young patients. It is commonly found in the ribs and jaws. Involvement of the jaws is evident in 22-27% of cases of MC. Most commonly, MCs are painless and occurs in the anterior portion of maxilla. Maxillofacial MCs are aggressive, has a tendency for recurrence and late metastasis to lung, bone, and lymph nodes, and is associated with an overall poor prognosis. Histopathologically, it is characterized by a biphasic pattern consisting of areas of hyaline cartilage mixed with small cell malignancy. Very few case reports involving the posterior maxillary region has been reported. This article reports a rare case of MC along with a review of the pertinent literature.