The Effect of Oxidation on the Tribological Performance of Few Vegetable Oils

BackgroundThe use of vegetable oils and their derivatives as lubricant base oils are ever increasing because of sustainability issues and in the context of conservation of nature as they are biodegradable and environmentally friendly. The one disadvantage which is of concern with vegetable oils is their limited oxidative stability.ObjectivesTo study the effect of oxidation on the tribological performance of few vegetable oils by subjecting the oil samples to accelerated ageing in a dark oven at different temperatures, inducing the oxidation under controlled conditions.MethodOils were stored at an elevated temperature in an oven under dark condition and the oxidized oil samples were analyzed in terms of various properties.Results and conclusionsThe samples were analyzed for the changes in viscosity, percentage of free fatty acid, peroxide number and were compared with fresh oils samples. Further tribological property was also evaluated and the observed differences were linked to formation of oxidation products like peroxides, kinetics of the oxidation with reference to ageing temperature

Imparting high-temperature grain stability to an Al-Mg alloy

Al alloys, despite their excellent strength-to-weight ratio, cannot be used at elevated temperatures because of microstructural instability owing to grain growth and precipitate coarsening, thus, leading to a drastic loss in their strength. In this work, we have attempted to address the issue of grain growth by introducing in-situ formed polymer derived ceramics in an Al-Mg alloy. A stable grain structure with minimal loss in hardness when exposed to 450 °C and 550 °C for 1 hour was obtained due to the particle pinning of the grain boundaries by the Zener mechanism.This work was supported by the French State through the program “Investment in the future” operated by the National Re- search Agency (ANR) and referenced by ANR-11-LABX-0 0 08-01 (LabEx DAMAS). Abhishek Pariyar acknowledges the Ph.D. scholarship awarded by the Ministry of Human Resource Development, Govt. of India

Association of genetic polymorphisms in XRCC4, XRCC5, XRCC6 and XRCC7 in cervical cancer susceptibility from rural population: a hospital based case-control study

Background: Cervical cancer is a major concern of health risk, moreover the leading cause of cancer causing deaths in women of rural India. This study was aimed to assess the risk of cervical cancer development in association with polymorphisms in XRCC4, XRCC5, XRCC6 and XRCC7 genes in rural population of south-western Maharashtra.Methods: This study included 350 cervical cancer proven cases and 400 age and sex matched controls. We used polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) to analyze the association XRCC4, XRCC6 and XRCC7 gene polymorphisms with cervical cancer development in women of Western Maharashtra.Results: The result from our study showed that allele frequencies of selected genes were not statistically different between the groups for XRCC4, XRCC5 and XRCC6. 6721 >T allele of XRCC7 (6721G>T) (OR= 2.34; 95% CI= (2.34 (1.60-3.43); p= <0.0001) significantly increased the risk of cervical cancer.Conclusions: This study indicates that XRCC7 gene polymorphisms play a role in modifying genetic susceptibility of individuals towards cervical cancer among women from rural Maharashtra. This case-control study also revealed negative association of XRCC6 gene in cervical carcinogenesis in the rural Indian population

Assessment of role of genetic polymorphisms in XRCC1, XRCC2 and XRCC3 genes in cervical cancer susceptibility from a rural population: a hospital based case-control study from Maharashtra, India

Background: Cervical cancer is a major concern of health risk, moreover the leading cause of cancer causing deaths in women of rural parts of India. This study was aimed to assess the risk of cervical cancer development in association with polymorphisms in X-Ray Cross Complementing Group (XRCC1, XRCC2 and XRCC3) genes in the rural population of south-western Maharashtra. We focused to determine the frequency of polymorphisms in DNA repair genes including XRCC1 at codon (cd) 194, cd 280, cd 399, XRCC2 at cd 188 and XRCC3 at cd 241 and their plausible role in cervical cancer risk from rural parts of India.Methods: This study included 350 proven cases with cervical cancer and 400 age and sex matched controls. We used polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) to analyze the association XRCC1, XRCC2 and XRCC3 gene polymorphisms with cervical cancer development in women of South-Western Maharashtra.Results: The result from our study showed that allele frequencies of selected genes were not statistically different between the groups for XRCC1 Trp194, XRCC2 His188 and XRCC3 Met241. XRCC1 His280 (OR= 4.36; 95% CI= (3.20-5.95); p= <0.0001) and XRCC1 Gln399 (OR= 2.99; 95% CI= (1.60-5.56); p= <0.0001) genotypes significantly increased the risk of cervical cancer.Conclusions: This study indicates that polymorphisms in cd 280 of exon 9 and cd 399 of exon 10 of XRCC1 gene could play a role in modifying genetic susceptibility of individuals towards cervical cancer among women from rural Maharashtra. This case-control study suggest that selected DNA repair genes represent genetic determinants in cervical carcinogenesis along with other risk factors in the rural Indian population

Identification of genetic polymorphisms in DNA repair xenoderma pigmentosum group D gene and its association with head and neck cancer susceptibility in rural Indian population: a hospital based case-control study from south-western Maharashtra, India

Background: Smoking and alcohol related head and neck cancer is a major concern of health risk in developing countries, such as India. In this study, we aimed to determine the frequency of polymorphisms in DNA repair gene, xeroderma pigmentosum complementation group D (XPD) at codon (cd) 156, cd199, cd320, cd751 in patients of oral cancer from South-Western Maharashtra, India and to evaluate their association with oral cancer development.Methods: We used polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) to analyze XPD gene polymorphisms in 320 patients with oral cancer and in 400 age and sex matched disease-free controls.Results: There was no significant difference in the genotype distribution between oral cancer patients and controls for each polymorphism (p>0.05) except XPD199. The result from our study showed that allele frequencies of selected genes were not statistically different between the groups for XPD Arg156, XPD Asn320, XPD Gln751. XPDMet199 (OR=29.44; 95% CI= (18.47-46.92); p≤0.0001) genotypes significantly increased the risk of head and neck cancer.Conclusions: This study indicates that polymorphisms in cd199 of XPD gene could play a role in modifying genetic susceptibility of individual to head and neck cancer inMaharashtra patients. Thus, the case-control study suggest that selected DNA repair genes represent genetic determinants in oral carcinogenesis along with other risk factors in the rural Indian population.

Association of Genetic Variants in XPC and XPG Genes with Cervical Cancer Risk in a Rural Population: A Hospital Based Case Control Study

Background: Cervical cancer is a major concern of health risk in urban and rural parts of India.. Aim and Objectives: This study was aimed to find out frequency of polymorphisms in DNA repair genes including Xeroderma pigmentosum complementation group C (XPC) and Xenoderma pigmentosum complementation group G (XPG) in patients of cervical cancer from Maharashtra and to evaluate their association with risk of cervical cancer. Materials and Methods: We used polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) to examine gene polymorphisms in 350 patients with cancer of cervix and 400 age and sex matched normal controls. Results: The results obtained indicated that there was no significant difference in the genotype distribution between cervical cancer patients and controls for XPC Lys939Gln, -371promoter and XPG His 1104 Asp. The result showed that genotype frequencies of XPC Val 499 Arg of codon 499 in exon 15 (OR=4.26; 95% CI=(3.007-6.03); p= <0.0001) were increased significantly. Conclusion: This study indicates that polymorphisms in Val499Arg haplotype of XPC gene appear to influence genetic susceptibility of individual to cervical cancer in Maharashtrian patients

Damage mechanisms in stainless steel and chromium carbide coatings under controlled environment fretting conditions

Fretting is of a serious concern in many industrial components, specifically, in nuclear industry for the safe and reliable operation of various component and/or system. Under fretting condition small amplitude oscillations induce surface degradation in the form of surface cracks and/or surface wear. Comprehensive experimental studies have been carried out simulating different fretting regimes under ambient and vacuum (10(-9) MPa) conditions and, temperature up to 400 degrees C. Studies have been carried out with stainless steel spheres on stainless steel flats, and stainless steel spheres against chromium carbide, with 25% nickel chrome binder coatings. Mechanical responses are correlated with the damage observed. It has been observed that adhesion plays a vital role in material degradation process, and its effectiveness depends on mechanical variables such as normal load, interfacial tangential displacement, characteristics of the contacting bodies and most importantly on the environment conditions. Material degradation mechanism for ductile materials involved severe plastic deformation, which results in the initiation or nucleation of cracks. Ratcheting has been observed as the governing damage mode for crack nucleation under cyclic tangential loading condition. Further, propagation of the cracks has been observed under fatigue and their orientation has been observed to be governed by the contact conditions prevailing at the contact interface. Coated surfaces show damage in the form of brittle fracture and spalling of the coatings. Existence of stick slip has been observed under high normal load and low displacement amplitude. It has also been observed that adhesion at the contact interface and instantaneous cohesive strength of the contacting bodies dictates the occurrence of material transfer. The paper discusses the mechanics and mechanisms involved in fretting damage under controlled environment conditions. (C) 2015 Elsevier B.V. All rights reserved

Elastic-plastic contact conditions for frictionally constrained bodies under cyclic tangential loading

A Frictionally constrained condition implies dependence of friction force on tangential displacement amplitude. The condition may occur due to chemical, physical, and/or mechanical interaction between the contacting surfaces. The condition, sometimes also referred to as the presliding condition or partial slip condition, is characterized under fretting. Under such conditions, various experimental studies indicate the existence of two distinguishable regions, that is, stick region and slip region. In the present study, frictionally constrained conditions are identified and the evolutions of stick-slip regions are investigated in detail. Investigations have been performed on self-mated stainless steel and chromium carbide coated surfaces mated against stainless steel, under both vacuum and ambient conditions. Contact conditions prevailing at the contact interface were identified based on the mechanical responses and were correlated with the surface damage observed. Surface degradation has been observed in the form of microcracks and material transfer. Detailed numerical analysis has also been performed in order to understand the energy dissipation and the damage mode involved in the surface or subsurface damage. It has been observed that under frictionally constrained conditions, the occurrence of annular slip features are mainly due to the junction growth, resulting from elastic-plastic deformation at the contact interface. Ratcheting has been observed as the governing damage mode under cyclic tangential loading condition

Fretting studies on self-mated stainless steel and chromium carbide coated surfaces under controlled environment conditions

Adhesive wear has been widely accepted as the type of wear which is most frequently encountered under fretting conditions. Present study has been carried out to study the mode of failure and mechanisms associated under conditions where strong adhesion prevails at the contact interface. Mechanical variables such as normal load, displacement amplitude, and environment conditions were controlled so as to simulate adhesion as the governing mechanism at the contact interface. Self-mated Stainless Steel (SS) and chromium carbide with 25% nickel chrome binder coatings using plasma spray and high-velocity oxy-fuel (HVOF) processes on SS were considered as the material for contacting bodies. Damage in the form of plastic deformation, fracture, and material transfer has been observed. Further, chromium carbide with 25% nickel chrome binder coatings using HVOF process on SS shows less fretting damage, and can be considered as an effective palliative against fretting damage, even under high vacuum conditions. (C) 2013 Elsevier B.V. All rights reserved

Damage quantification under sliding and seizure condition using first-of-a-kind fretting machine

In a practical situation, it is difficult to model exact contact conditions clue to challenges involved in the estimation of contact forces, and relative displacements between the contacting bodies. Sliding and seizure conditions were simulated on first-of-a-kind displacement controlled system. Self-mated stainless steels have been investigated in detail. Categorization of contact conditions prevailing at the contact interface has been carried out based on the variation of coefficient of friction with number of cycles, and three-dimensional fretting loops. Surface and subsurface micro-cracks have been observed, and their characteristic shows strong dependence on loading conditions. Existence of shear bands in the subsurface region has been observed for high strain and low strain rate loading conditions. Studies also include the influence of initial surface roughness on the damage under two extreme contact conditions. (C) 2013 Elsevier B.V. All rights reserved