R. Mishra

Thermodynamic stability of solid SrThO3

Abstract The Gibbs energy of formation of strontium thorate was determined by the Knudsen effusion forward collection technique. The evaporation process from a mixture of tungsten and strontium thorate in the Knudsen cell could be represented by the following heterogeneous equilibria: 5SrThO3(s)+W(s)=Sr2WO5(s)+5ThO2(s)+3Sr(g), 1670 Δ f G 0 ( SrThO 3 ( s )) (±5.0 kJ mol −1 )=−1953.6+0.367·T , (1670 Δ f G 0 ( SrThO 3 ( s )) (±7.0 kJ mol −1 )=−1960.2+0.369·T , (2135

Gibbs energy of formation of Ba(OH)2 vapor species using the transpiration technique

Abstract The Gibbs energy of formation of Ba(OH) 2 was determined employing the heterogeneous reaction between solid BaO and water vapor and generating gaseous barium hydroxide species according to the reactions BaO(s)+H 2 O(g)=Ba(OH) 2 (g). The equilibrium vapor pressure of Ba(OH) 2 species under a controlled pressure of water vapor was measured using an automatic recording transpiration apparatus. From the vapor pressure results, the equilibrium constant of the reaction obtained could be represented as ln K p (±0.04)=−16792.3/T+4.94 , K p = p (Ba(OH) 2 )/ p (H 2 O) (1346⩽ T /K⩽1451). The Gibbs energy of formation of Ba(OH) 2 derived from these data could be expressed as Δ f G °( Ba ( OH ) 2 , g )(±2 kJ mol −1 )=−667.29+0.118 T (1346⩽T/ K ⩽1451) . From the study, the second-law and third-law values of Δ f H°(Ba(OH) 2 ,g, 298.15 K) were worked out to be −(645.1±8.0) kJ mol −1 and −(643.9±2.5) kJ mol −1 , respectively.

Ionic transport behavior of BaO containing sodium borosilicate glasses

The present manuscript describes the preparation, characterization and electrical behavior of sodium borosilicate glasses with varying concentrations of BaO, while maintaining the SiO(2):B(2)O(3):Na(2)O ratios constant for all the samples. The effect of BaO substitution on the ionic conductivity of glasses was studied by ac impedance analyzer, below the glass transition temperature. The diffusion coefficient (D) of each sample has been determined from the values of electrical conductivity and density. The activation energy for sodium ion transport has been calculated from the values of diffusion coefficients at different temperatures. The electrical properties of the modified glass have been explained on the basis of the structural factor.

Thermodynamic stability of RuTe2 solid by vapor pressure study

Abstract The vaporization behavior of the intermetallic compound RuTe 2 (s) was studied in the temperature range of 831–1148 K by the Knudsen effusion technique. As a prerequisite to the study, the nature of the vaporization equilibrium was first obtained. Phase analysis of the partially evaporated sample of RuTe 2 (s) from thermogravimetric experiment carried out in inert environment showed the TG residue to be a biphasic mixture of Ru(s) and RuTe 2 (s). This result together with the available thermodynamic information of Te vapor revealed that the compound incongruently volatilize as RuTe 2 (s)=Ru(s)+Te 2 (g). The equilibrium vapor pressure of Te 2 (g) derived from the measurement at the different temperatures could be expressed as ln( p /Pa)(±0.33)=−33231.2/ T +33.67 (831≤ T /K≤1148). The result of this study is discussed in the light of the reported data on the intermetallic compound.

Preparation of Cs2ZrO3 and Cs2ThO3 Through Sol-gel Method and Their Characterization

Cesium zirconate and cesium thorate were prepared by sol-gel method following citrate-nitrate route. The compounds were characterized by X-ray diffraction, chemical analysis and simultaneous TG-DTA. The methods of preparation of Cs2ZrO3 and Cs2ThO3 reported in literature involve difficult steps and require stringent experimental conditions for obtaining the compounds. In this work we report an easier method for the preparation of these compounds at relatively low temperature.

Retrospective Analysis of Efficacy and Toxicity of Hypo-fractionated Radiotherapy in Breast Carcinoma

INTRODUCTION The conventional dose fractionation of adjuvant radiotherapy (RT) to whole breast is 45-50 Gy in 25 fractions as 1.8-2.0-Gy per fraction. Lumpectomy cavity with a 1.5-2-cm margin receieves additional 10- 16 Gy doseas boost. Alternative dose fraction schedules used in various randomised trials have established the role of hypofractionated radiotherapy (HRT) in early breast cancer. HRT allows time and cost saving thus better patient compliance. However the efficacy and toxicity of HRT in locally advanced breast cancer is still under evaluation. AIM To study the toxicity and efficacy of Hypofractionated Radiotherapy (HRT) as compared to Conventional Radiotherapy (CRT) in breast cancer at our centre. MATERIALS AND METHODS A retrospective analysis of breast cancer patients treated between October 2012- September 2014 with adjuvant radiation therapy as CRT or HRT. The data of these patients was retrieved and analysed regarding demographic profile, stage at presentation, pathological type, extent of surgery, chemotherapy, efficacy and toxicity of HRT. The toxicity assessment was done as per RTOG toxicity criteria. The data were analysed using SPSS software version 20.0. RESULTS A total of 100 patients with carcinoma breast who received radiotherapy over two years were analysed. Age ranged from 18-90 years, mean 49.15 ± 12.7 years. Fifty-five patients were post-menopausal, predominant clinical feature was painless lump in the breast (98%). Early stage (Stage I and II) constituted 41%, locally advanced disease in 59%. Modified radical mastectomy was done in 75%, breast conserving surgery in 25%. A 56 patients received HRT and 44 were treated with CRT. The most common acute toxicity was skin grade I. An 18% patients in HRT arm and 30% patients in conventional arm developed grade II skin toxicity (p=0.23). Dysphagia grade I was seen in 10% cases in CRT arm and 12% in HRT arm. The median follow-up period was 11.3 months with 2 loco-regional failures in each arm. CONCLUSION HRT seems to be equally efficacious and no more toxic than CRT in carcinoma breast even in unselected sub-group of patients.

A Randomized Prospective Study of Concurrent Chemo-Radiotherapy vs Accelerated Hyperfractionation in Advanced Cancer of Head and Neck

INTRODUCTION Locally advanced unresectable squamous cell carcinoma of head and neck has poor locoregional control when treated with conventionally fractionated Radiation Therapy (RT) alone. However, Concurrent Chemo-Radiotherapy (CRT) and altered fractionated RT schedules like Accelerated Hyperfractionation (AHF) are two different treatment strategies that have shown to be associated with better efficacy as compared to conventional RT alone in such cases. AIM Aim of the study was to compare these two treatment strategies i.e., CRT and AHF radiation treatment to know which is better in terms of clinical outcome and toxicity in patients of locally advanced unresectable squamous cell carcinoma of head and neck. MATERIALS AND METHODS A prospective randomized trial was done to compare the effect of CRT and of AHF radiation treatment in locally advanced unresectable head and neck cancer on 15 patients in each arm and followed up over three months period. RESULTS At the end of three months after completion of treatment protocol, complete response was 62% in CRT arm and 53% in AHF arm. In CRT arm and AHF arm, Grade 3 skin reactions were observed in 100% and 87%, grade 3 mucosal reactions were in 62% and 67% of cases, respectively. Three patients died in CRT arm (two due to myelosuppression and associated infection; one during the treatment and another after two weeks of treatment completion. The third patient expired after one month of treatment completion at his native place due to unknown reason). One patient died in AHF arm (during treatment due to cardiac event). CONCLUSION Efficacy of AHF was comparable to CRT with lesser toxicity. So the present study suggests that AHF should be preferred over CRT in locally advanced, unresectable, squamous cell head and neck cancer followed over three months non-treatment period.

Congenital Orbital Teratoma: A Rare Presentation

Congenital Orbital Teratoma: A Rare Presentation We report a very rare case of unilateral congenital orbital teratoma with marked proptosis presenting at birth. Clinical examination and histopathology reports showed the tumor to be confined to the orbit. Considering the size and extent of tumour, an exenteration was done under general anaesthesia.