Computational Study of the Reactions of Heteroatomic Compounds on CeO2

The mechanisms of ambient-temperature reactions of heteroatomic compounds catalyzed by ceria (CeO2), an archetypical reducible oxide, for enzyme mimetics, environmental protection, and chemical synthesis are investigated in this dissertation using theoretical methods. CeO2 is modeled with thermodynamically stable low-index surfaces exposed by commonly studied ceria thin films and nano particles. To understand phosphatase-like dephosphorylation activity, stable adsorption states and surface reactions of model phosphates are examined. Binding of the central P-atom to surface lattice oxygen (Olatt) supplemented by phosphoryl O-Ce interaction is the only stable adsorption state for the un-dissociated molecule. Deprotonation of phosphate monoesters, which are multi-protic acids, is energetically favorable on the amphoteric CeO2 surfaces, and it mainly affects the P-O ester bond scission energies. Peptidase-like activity toward cleaving stable amide bonds is studied next on model amine compounds including acetamide. Nucleophilic attack by Olatt on the carbonyl C of the amide group forming a tetrahedral intermediate is key to C-N bond scission. When crystalline facet, dispersion interactions, and solvation effects are taken into consideration, the results suggest (110) to be the more active than the other two facets for catalyzing deamidation in aqueous phase. In addition to these hydrolysis reactions, a condensation reaction has also been investigated for a model oxygenate (acetaldehyde), which is relevant to upgrading of biomass feedstock. Conclusive evidence for C-C coupling to selectively form crotonaldehyde on CeO2(111) under flow conditions is obtained theoretically in collaboration with infrared experiment. Overall, the catalytic activity of CeO2 for these reactions at ambient temperature originates from neighboring acid(Ce)-base(Olatt) site pairs through characteristically Langmuir-Hinshelwood mechanisms, instead of Mars-van Krevelen mechanisms that are prevalent at higher temperatures

Hydrolysis of Acetamide on Low-Index CeO Surfaces: Ceria as a Deamidation and General De-esterification Catalyst

Using DFT calculations and acetamide as the main example, we show that ceria is a potential catalyst for the hydrolysis of amide and similar bonds. The overall reaction is endergonic in the gas phase, yielding acetic acid and ammonia, but is slightly exergonic in the aqueous phase, which facilitates ionization of the products (CHCOO and NH ). Neighboring Ce and O sites on the CeO(111), (110), and (100) facets are conducive to the formation of an activated metastable tetrahedral intermediate (TI) complex, followed by C-N bond scission. With van der Waals and solvation effects taken into account, the overall reaction energetics is found to be most favorable on the (111) facet as desorption of acetic acid is much more uphill energetically on (110) and (100). We further suggest that the Ce-O-Ce sites on ceria surfaces can activate X(=Y)-Z type bonds in amides, amidines, and carboxylate and phosphate esters, among many others that we term generalized esters . A Brønsted-Evans-Polanyi relationship is identified correlating the stability of the transition and final states of the X-Z generalized ester bond scission. A simple descriptor (ΣΔχ) based on the electronegativity of the atoms that constitute the bond (X, Y, Z) versus those of the catalytic site (O, Ce, Ce) captures the trend in the stability of the transition state of generalized ester bond scission and suggests a direction for modifying ceria for targeting specific organic substrates

Porocarcinoma scalp with high risk features treated with surgery and adjuvant radiotherapy: A case report and review of literature

Eccrine porocarcinoma is a rare malignant sweat gland tumor arising from the intra dermal part of the gland and accounts for only 0.005% of all epithelial cutaneous tumors. Commonly involved site includes extremities and face. Scalp is a rare site for porocarcinoma with less than 20 reported cases so far. Wide local excision with clear margins remains the treatment of choice. Review of literature revealed a local recurrence rate of 37.5% and a nodal involvement risk of 20%. Porocarcinoma of the scalp is peculiar in that the primary tumor may be large at presentation, making surgery with adequate margins difficult. Adjuvant radiotherapy must be considered in a case to case basis due to the high local recurrence rates compared to other sites of porocarcinoma and should be given to all patients with close margins and extra capsular extension

A Study of Knowledge regarding Health Impact of Tobacco and Attitude towards Quitting among Lower-Middle and Lower Classes in a Resettlement Colony in Delhi, India

Objectives: To study knowledge regarding health impact of tobacco and attitude towards quitting among lower-middle and lower classes in a resettlement colony in Delhi.Materials and Methods: The study was conducted between the months of March and October in the year 2011, in a resettlement colony of Delhi. The study was a cross-sectional, community-based, house-to-house survey and involved interviews of present tobacco consumers using a structured interview guide consisting mainly of close-ended questions and some open-ended questions.Results: 1698 subjects were enrolled in the study with 90.8% males and 8.7% females. Mean age of the subjects was 40 years, while median age was 37 years. 87% of the respondents were educated up to higher secondary or less. Some other key findings included the following:45% of the respondents had no information on the effect of tobacco consumption on health, and 60% did not have any knowledge of the laws regarding tobacco consumption. Television was the most common source of information regarding tobacco consumption, followed by newspapers. Three-fourths of the respondents had knowledge that their using tobacco had an impact on other family members, and 60% believed that children were affected most commonly.Spouse or children were the most common people who stressed upon the respondents to leave tobacco, followed by parents. Self-motivation was the most commonly reported second reason for attempting to quit tobacco. However, doctors or other medical personnel appeared to play only a marginal role in motivating the tobacco users to quit tobacco.Conclusion: This study shows that there is tremendous scope for improving the outcomes in tobacco control by strengthening the programmatic components of tobacco control such as propagating the health effects of tobacco in a manner intelligible to the people and making the health system to proactively contribute in anti-tobacco efforts

Outcome of primary orbital lymphoma treated with induction chemotherapy followed by conformal radiotherapy

Purpose: To analyze the clinical outcome of primary orbital lymphoma (POL) patients treated with a combined modality approach with local radiotherapy after induction chemotherapy. Methodology: We retrospectively retrieved demographic, treatment and outcome data of patients treated for POL from 2000 to 2010. The charts were reviewed and the data were tabulated in a predesigned pro-forma. Results: 23 patients of POL were found evaluable. Median age was 55 years (range 24–70 years). Of 23 patients, 15 were male and 8 female, making the male:female ratio approximately 1.9:1. Patients were thoroughly evaluated and staged. All but one patient received multi agent chemotherapy. Radiotherapy was delivered for all cases. Radiation was delivered by 3DCRT technique. Median dose of radiation was 45 Gy (range 20–45 Gy). Median follow up was 26.8 months. None of the patients had any evidence of local failure or systemic progression. Conclusion: A combined modality therapy with a combination of CHOP/COP based chemotherapy and moderate dose of radiotherapy imparts excellent long term local and systemic disease control

Elucidating the Mechanism of Ambient-Temperature Aldol Condensation of Acetaldehyde on Ceria

Using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT) calculations, we conclusively demonstrate that acetaldehyde (AcH) undergoes aldol condensation when flown over ceria octahedral nanoparticles, and the reaction is desorption-limited at ambient temperature. -Crotonaldehyde (CrH) is the predominant product whose coverage builds up on the catalyst with time on stream. The proposed mechanism on CeO(111) proceeds via AcH enolization (i.e., α C-H bond scission), C-C coupling, and further enolization and dehydroxylation of the aldol adduct, 3-hydroxybutanal, to yield -CrH. The mechanism with its DFT-calculated parameters is consistent with reactivity at ambient temperature and with the kinetic behavior of the aldol condensation of AcH reported on other oxides. The slightly less stable -CrH can be produced by the same mechanism depending on how the enolate and AcH are positioned with respect to each other in C-C coupling. All vibrational modes in DRIFTS are identified with AcH or -CrH, except for a feature at 1620 cm that is more intense relative to the other bands on the partially reduced ceria sample than on the oxidized sample. It is identified to be the C=C stretch mode of CHCHOHCHCHO adsorbed on an oxygen vacancy. It constitutes a deep energy minimum, rendering oxygen vacancies an inactive site for CrH formation under given conditions

Malignant Peripheral Nerve Sheath Tumour of the Maxilla

A 38-year-old man was diagnosed with malignant peripheral nerve sheath tumour of the maxilla. He was treated with total maxillectomy. Histopathological examination of the resected specimen revealed a close resection margin. The tumour was of high grade with an MIB-1 labelling index of almost 60%. At six weeks following the surgery, he developed local tumour relapse. The patient succumbed to the disease at five months from the time of diagnosis. The present report underlines the locally aggressive nature of malignant peripheral nerve sheath tumour of the maxilla which necessitates an early therapeutic intervention. A complete resection with clear margins is the most important prognostic factor for malignant peripheral nerve sheath tumour in the head and neck region. Adjuvant radiotherapy may be considered to improve the local control. Future research may demarcate the role of targeted therapy for patients with malignant peripheral nerve sheath tumour