Parameter determination and experimental validation of a wire feed additive manufacturing model

“Laser metal deposition is an additive manufacturing method with great scope and robustness. The wire fed additive manufacturing method has great opportunities in space applications and other zero gravity manufacturing processes. Process parameters play an important role in controlling the complex phenomenon and obtaining an ideal manufactured part. These parameters can be efficiently determined using simulation tools which are highly essential in visualizing real world experiments, therefore saving time and experimental costs. The objective of this study is to develop a transient 3D model of laser aided wire feed metal deposition which realizes the heat transfer and fluid flow behavior of the melt pool and wire deposition with varying process parameters. The model was programmed in Python and a 1 KW Gaussian beam fiber laser was used to conduct experiments. Design of experiments was utilized to determine all possible levels of factors and experiments were conducted on Ti-6Al-4V alloy with and without wire deposition to establish the behavior of the critical outputs with varying parameters. The effect of laser exposure to the melt pool profile and deposit profile is obtained and the results are compared with the model. The comparison of simulation and experimental results shows that this model can successfully predict the temperature profile, fluid characteristics and solidified metal profile. The optimum input parameters based on material properties can be identified using this model”--Abstract, page iii

Genetic regulation of adult hippocampal neurogenesis: A Systems genetics approach using BXD recombinant inbred mouse strains

Adult hippocampal neurogenesis is regulated at various levels and by various factors. Genetic influence is an important key determinant of adult neurogenesis and exerts its effects at all levels. In vivo studies have suggested that adult hippocampal neurogenesis is highly variable and heritable among different laboratory strains of mice. To dissect the genetic effect from other contributing factors, it is necessary to study adult neurogenesis under highly controlled environment conditions. We extracted adult hippocampal precursor cells (AHPCs) from 20 strains of the BXD set of recombinant inbred mice, cultured them and studied the effect of genetic background on neurogenesis. The BXD panel consists of mouse lines derived from an intercross between inbred parentals C57BL/6J and DBA/2J. Both of the parentals are fully sequenced and all the strains are well characterized in terms of genotypic and phenotypic characteristics. This allows us to use advanced genetic techniques to identify novel genomic loci and gene-gene interactions important in adult neurogenesis. Comparison of the AHPCs from 20 BXD strains, with respect to cell proliferation and neuronal and astrocytic differentiation in vitro, revealed a large variation for these traits across the strains. Proliferation, as measured by BrdU incorporation, showed over two- fold differences between the extremes. Similar differences were observed for neurogenic (4-fold) and astrogenic differentiation (2-fold). These three traits all showed strong heritability values indicating that the differences were mainly attributed to the genetic component. QTL mapping, with these phenotypic data, revealed that there was no major contribution from single loci controlling these traits. Instead, we found many loci with smaller effects associated with these traits. Gene expression profiling using RNA samples from proliferating cultures of the 20 BXD mice strains yielded two cis eQTL candidates that directly regulated proliferation, LRP6 and Chchd8. LRP6 is well known as a co-receptor of Wnt signaling, but the function of Chchd8 is not known. Further experimentation, using over expression and gene silencing demonstrated that LRP6 negatively regulates AHPCs proliferation. Thus, from this study using a system genetics approach, we were able to identify, LRP6 as a novel regulator of adult hippocampal neurogenesis

Identifying Outliers in Fuzzy Time Series

Time series analysis is often associated with the discovery of patterns and prediction of features. Forecasting accuracy can be improved by removing identified outliers in the data set using the Cook’s distance and Studentized residual test. In this paper a modified fuzzy time series method is proposed based on transition probability vector membership function. It is experimentally shown that the proposed method minimizes the average forecasting error compared with other known existing methods

Dry Machining of AA7075 by H-DLC Coated Carbide End Mill

AbstractPresent investigation evaluates the performance of a hydrogenated diamond like carbon (H-DLC) coating on carbide end mills during machining of an Al-Zn-Mg based alloy i.e. AA7075. Although diamond is known to be the most potential hard coating on carbide tools to deal with the challenges of machining aluminium, DLC coating offers economic solution in dealing with this material at medium cutting speeds. Present study explores the feasibility of using a H-DLC coating, which is eventually softer than non-hydrogenated DLC, in machining this alloy and compares its performance with that of uncoated carbide tools under dry environment. In terms of surface finish and cutting force this H-DLC coated tool substantially outperformed uncoated carbide one in the cutting speed range of 60 to 180 m/min. The coating was able to substantially arrest built up edge (BUE) formation, however, found to be with minor trace of built up layer (BUL)

HYBRID NANOSTRUCTURED MATERIALS FOR SUPERCAPACITORS

School of Molecular Sciences(Chemistry)clos

Studies on methylmalonyl-CoA mutase from Escherichia coli

Methylmalonyl-CoA mutase (MCM, E.C. 5.4.99.2), a coenzyme B12-dependent enzyme, catalyses the inter conversion of succinyl-CoA and methylmalonyl- CoA. The gene (sbm) encoding this enzyme is found in Escherichia coli (E. coli) at 62.3min on the E. coli chromosome. However, the metabolic role of this enzyme in the organism is not known. This project involves an investigation into this metabolic obscurity. The sbm gene is part of a four gene operon which also includes argK (or ygfD) that codes for a protein kinase catalysing the phosphorylation of two periplasmic binding proteins involved in cationic amino acid transport, ygfG that codes for methylmalonyl-CoA decarboxylase and ygfH that codes for propionyl-CoA: succinyl-CoA transferase. From existing literature we suspect that this operon, including the sbm gene, could be involved in the utilisation of unusual carbon sources such as succinate and propionate. An insertion mutant of the sbm gene created by transposon mediated mutagenesis was used for investigating the role of this gene. The wild type E. coli K12 strain, E. coli TR6524 and the mutant E. coli K12 (sbm::MudJ) were used in this study. Growth of the two strains (E. coli TR6524 and FA1P1) in minimal media with three different concentrations (0.05, 0.5, 5.0μg/mL) of vitamin B12 and in the presence succinate, propionate or glucose as the sole source of carbon, was studied. Growth was typical in media with glucose with no major differences in the growth pattern of the wild type and mutant strain. However, the two strains exhibited a differential growth pattern in media containing succinate, with the wild type growing faster than the mutant, indicating the role of the sbm gene in the utilisation of this carbon source. Growth in media containing propionate as the sole carbon source indicated only marginal differences in the growth pattern of the wild type and mutant strain. This result possibly suggests that the other pathways for propionate utilisation in E. coli compensate for the lack of a functional Sbm protein in the mutant strain. Promoter analysis indicated the presence of a promoter induced by σS, a transcription factor involved in the expression of proteins under stress or stationary phase growth conditions. Reverse transcription polymerase chain reaction (RT-PCR) studies of the genes of the sbm operon (sbm-argK-ygfGygfH) under the same growth conditions were carried out. Densitometric analysis of the PCR products suggested that the transcription level of sbm was higher in E. coli grown in succinate as compared to when grown in glucose and not as much when grown in propionate indicating a transcriptional level control of the sbm gene expression during the utilisation of succinate. RT-PCR studies also indicated a higher level of transcription of the gene in the stationary phase of the culture during the utilisation of succinate. Real time reverse transcription PCR (QPCR) analysis was used for the absolute quantification of the transcription of the genes of the sbm operon. An increase in the mRNA levels corresponding to the sbm, argK and ygfG genes was observed as E. coli TR6524 growth reached stationary phase, in the presence of succinate or propionate as the sole source of carbon as compared to glucose, In contrast, the highest mRNA levels corresponding to the ygfH gene were observed in the early log-phase of growth. This indicated a differential transcriptional level control of the genes within the operon. This study further established the possible role of this operon in the utilisation of succinate and propionate. The MCM enzyme activity measurement in the whole cell extracts of the wild type E. coli K12, grown under the above mentioned conditions, led to the first ever measurement of MCM activity in wild type E. coli. These measurements also revealed a four fold increase of the MCM specific activity in the case of growth in succinate (4.76x10-3U/mg) and a two fold increase for growth in propionate (2.79x10-3U/mg) compared to that observed with growth in glucose (1.37x10-3U/mg), indicating a significant level of involvement of the enzyme in succinate utilisation, and to a lesser extent in propionate utilisation. The proteomic analysis to understand the gene expression pattern of E. coli TR6524 was carried out using cells harvested at the stationary phase. The results showed that growth conditions induced the expression of transport related (HisJ, DppA) and energy generating proteins (PckA, AceF) required by E. coli to cope with the stressful growth conditions. However, Sbm was not identified among the limited protein spots that were analysed. Finally, E. coli K12 sbm gene was successfully cloned into B. cereus SPV leading to the development of a metabolically engineered polyhydroxyalkanoate producing strain of B. cereus. The intention was to provide the bacteria with a natural intracellular source of propionyl-CoA, leading to the production of the P(3HB-co-3HV) copolymer from structurally non related carbon sources like glucose. Hence, this work has initiated investigation into the metabolic role of the sbm gene product in E. coli. In addition, it has also led to the use of this gene product in metabolic engineering applications.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Prediction of glomerular filtration rate by schwartz formula in children aged 5 - 12 years admitted in an urban referral centre

INTRODUCTION: Glomerular filtration rate (GFR) provides an excellent measure of the filtering capacity of the kidneys. Glomerular filtration rate (GFR) is the best estimate of functional renal mass. It is the most widely used indicator of renal function in patients with renal disease. The severity and the prognosis of any renal disease are usually predicted on this parameter. A low or decreasing GFR is a good index of chronic kidney disease. Since the total kidney GFR is equal to the sum of the filtration rates in each of the functioning nephrons, the total GFR can be used as an index of functioning renal mass. A decrease in GFR precedes kidney failure in all forms of progressive kidney disease. Monitoring changes in GFR can delineate progression of kidney disease. The level of GFR is a strong predictor of the time to onset of kidney failure as well as the risk of complications of chronic kidney disease. Additionally, estimation of GFR in clinical practice allows proper dosing of drugs excreted by glomerular filtration to avoid potential drug toxicity. AIM OF THE STUDY: To study the validity / accuracy of Schwartz formula in predicting Glomerular filtration rate (GFR), comparing it with creatinine clearance. MATERIALS AND METHODS: Place of study: Institute of Child Health & Hospital for children, Chennai. Period of study: July 2004 to February 2006. Study Design: Evaluation of a diagnostic modality. Study population: Children aged 5 – 12 years. Inclusion criteria: 1. Children without any evidence of renal disease with normal hydration, 2. Nephrotic syndrome patients, 3. Acute Glomerulonephritis patients, 4. All CRF patients admitted in nephrology ward as predicted by creatinine clearance. Exclusion criteria: Children with obstructive uropathy, neurogenic bladder and voiding dysfunction. SUMMARY AND CONCLUSION: •The Schwartz formula predicts GFR better in children with normal renal function. •In predicting GFR in children with impaired renal function, the Schwartz formula has a sensitivity of 65.8%. a specificity of 94.3%. a positive predictive value of 97.3%. a negative predictive value 46.5%. •There is a significant correlation (r = 0.75) between Schwartz formula and creatinine clearance. To conclude, the Schwartz formula has a sensitivity of 65.8% in detecting children with impaired renal function, and therefore may not be useful as a screening method, and these children may need more accurate methods of estimating GFR

Selection of Machining Parameters of Face Milling operation for Aluminium with HSS cutter using Response Surface Methodology and Genetic Algorithm

Components used in chemical equipments are produced from forging, extrusion and casting processes with classic dimension tolerances due to its producing ability. So machining processes were introduced for close tolerance assembly and improve the product working efficiencies. At present,  lot of machining processes are available for producing chemical equipments such as turning, milling, drilling and grinding etc.,. Milling operation is playing critical role on making the chemical equipment’s components with high accuracy and higher productivity. Face milling operation is one of the milling processes which is used for achieving higher flatness and surface finish of chemical equipment’s parts. Thiswork concentrates the parameters influence on Material Removal Rate (MRR) and Surface Roughness (SR) by using aluminium as work piece material. Actually, aluminium alloy has the  most significant in chemical industries because of its inherent properties such as, corrosive resistance , low weight to strength ratio. The milling parameters such as feed rate, spindle speed  and depth of cut are selected as parameters for improving the quality and productivity. This work put together the link between input and response variables for developing the face milling performances. The Response Surface Methodology (RSM) is employ for making the link between dependent and independent variables. Building the empirical model by conducting regression analysis The performance of developed regression models are verified with experimental results. Verification results show the developed models have best agreement with experimental results. The developed models are used for achieving the best input parameters by using Genetic Algorithm (GA). Finally, the optimal parameters are evaluated by GA