Evolution Of Microstructure And Residual Stress In Disc-shape Eb-pvd Thermal Barrier Coatings And Temperature Profile Of High Pressure Turbine Blade

A detailed understanding of failure mechanisms in thermal barrier coatings (TBCs) can help develop reliable and durable TBCs for advanced gas turbine engines. One of the characteristics of failure in electron beam physical vapor deposited (EB-PVD) TBCs is the development of instability, named rumpling, at the interface between (Ni, Pt)Al bond coat and thermally grown oxide (TGO). In this study, thermal cycling at 1100°C with 1 hr dwell time was carried out on 25.4mm disc specimens of TBCs that consisted of EB-PVD coated ZrO2-7wt. %Y2O3, (Pt,Ni)Al bond coat, and CMSX-4 Ni-based superalloy. At specific fraction of lifetime, TBCs were examined by electron microscopy and photostimulated luminescence (PL). Changes in the average compressive residual stress of the TGO determined by PL and the magnitude of rumpling, determined by tortuosity from quantitative microstructural analyses, were examined with respect to the furnace thermal cyclic lifetime and microstructural evolution of TBCs. The combination of elastic strain energy within the TGO and interfacial energy at the interface between the TGO and the bond coat was defined as the TGO energy, and its variation with cyclic oxidation time was found to remain approximately constant ~135J/m2 during thermal cycling from 10% to 80% thermal cyclic lifetime. Parametric study at ~135J/m2 was performed and variation in residual stress with rumpling for different oxide scale thicknesses was examined. This study showed that the contribution of rumpling in residual stress relaxation decreased with an increase in TGO thickness. High pressure turbine blades serviced for 2843 hours and in the as coated form were also examined using electron microscopy and photostimulated luminescence. The difference in iv residual stress values obtained using PL on the suction and pressure sides of as-coated turbine blade were discussed. The presence of a thick layer of deposit on the serviced blade gave signals from stress free α-Al2O3 in the deposit, not from the TGO. The TGO growth constant data from the disc-shape TBCs, thermally cycled at 1100°C, and studies by other authors at different temperatures but on similar EB-PVD coated TBCs with (Pt, Ni)Al bond coat and CMSX-4 Nibased superalloy were used to determine the temperature profile at the YSZ/bond coat interface. The interfacial temperature profiles of the serviced blade and the YSZ thickness profile were compared to document the variable temperature exposure at the leading edge, trailing edge, suction and the pressure side

Characterization of PksD and PksG in Bacillus subtilis

Polyketides are a diverse class of natural products that have a wide variety of pharmacological applications. Polyketides are biosynthesized by modular polyketide synthases in a very similar fashion to that of fatty acids. The distinct features of each module govern the degree of reduction in the two carbons added during polyketide synthesis. The highly modular constitution of polyketide synthases makes them adjustable to synthesize unnatural medicinally important polyketides. Difficidin, an antibiotic polyketide, isolated from Bacillus subtilis strain 39320 and 39374, contains an unusual subunit that can not be explained by literature precedent for understood polyketide synthesis. Polyketide synthases have been proposed to biosynthesize difficidin. PksD, being homologous to acyltransferases, is expected to load malonyl CoA to the acyl carrier protein domains found in PksJLMNR, and AcpK. PksG is homologous to hydroxymethylglutaryl-CoA synthases and expected to be involved in the synthesis of the unusual subunit in difficidin. PksD, from B. subtilis strain 168, was successfully cloned, overexpressed, and purified. Attempts to characterize pure PksD by MALDI-MS were not successful. PksG was successfully cloned from B. subtilis strain 39374. Attempts at generating a knockout mutant of pksG in B. subtilis 39374 were not successful. The function of PksG in difficidin production could not be confirmed. However, on the basis of sequence data, we discovered that B. subtilis strain 39374 is likely B. amyloliquefaciens."--Abstract from author supplied metadata

Network analysis reveals common host protein/s modulating pathogenesis of neurotropic viruses

Network analysis through graph theory provides a quantitative approach to characterize specific proteins and their constituent assemblies that underlie host-pathogen interactions. In the present study, graph theory was used to analyze the interactome designed out of 50 differentially expressing proteins from proteomic analysis of Chandipura Virus (CHPV, Family: Rhabdoviridae) infected mouse brain tissue to identify the primary candidates for intervention. Using the measure of degree centrality, that quantifies the connectedness of a single protein within a milieu of several other interacting proteins, DJ-1 was selected for further molecular validation. To elucidate the generality of DJ-1’s role in propagating infection its role was also monitored in another RNA virus, Japanese Encephalitis Virus (JEV, Family: Flaviviridae) infection. Concurrently, DJ-1 got over-expressed in response to reactive oxygen species (ROS) generation following viral infection which in the early phase of infection migrated to mitochondria to remove dysfunctional mitochondria through the process of mitophagy. DJ-1 was also observed to modulate the viral replication and interferon responses along with low-density lipoprotein (LDL) receptor expression in neurons. Collectively these evidences reveal a comprehensive role for DJ-1 in neurotropic virus infection in the brain

Japanese encephalitis virus induces human neural stem/progenitor cell death by elevating GRP78, PHB and hnRNPC through ER stress

Japanese encephalitis virus (JEV), which is a causative agent of sporadic encephalitis, harbours itself inside the neural stem/progenitor cells. It is a well-known fact that JEV infects neural stem/progenitor cells and decreases their proliferation capacity. With mass spectrometry-based quantitative proteomic study, it is possible to reveal the impact of virus on the stem cells at protein level. Our aim was to perceive the stem cell proteomic response upon viral challenge. We performed a two-dimensional gel electrophoresis-based proteomic study of the human neural stem cells (hNS1 cell line) post JEV infection and found that 13 proteins were differentially expressed. The altered proteome profile of hNS1 cell line revealed sustained endoplasmic reticulum stress, which deteriorated normal cellular activities leading to cell apoptosis. The proteomic changes found in hNS1 cell line were validated in vivo in the subventricular zone of JE infected BALB/c mice. Congruent alterations were also witnessed in multipotent neural precursor cells isolated from human foetus and in autopsy samples of human brain clinically diagnosed as cases of JE patients. Endoplasmic reticulum resident chaperone GRP78, mitochondrial protein Prohibitin and heterogeneous nuclear ribonucleoprotein hnRNPC (C1/C2) have been shown to interact with viral RNA. Hence it is proposed that these are the principle candidates governing endoplasmic reticulum stress-induced apoptosis in JEV infection

Two-Dimensional Nanostrips of Hydrophobic Copper Tetradecanoate for Making Self-Cleaning Glasses

We report a simple, solution-based technique for coating arbitrary surfaces with thin layers of self-assembled copper tetradecanoate (CTD) nanostrips, resulting in an optically transparent, superhydrophobic coating. The nanostrip-coated surfaces show water contact angles close to 150° and roll-off angles as small as 2°-3°. Importantly, CTD retains its hydrophobic nature even after annealing the self-assembled nanostrips at 200°C, which does not alter the crystal structure but “melts” the surface microstructure. This clearly indicates that the hydrophobicity in CTD is likely to be intrinsic in nature and not induced by the surface microstructure (as has been suggested earlier). Strong hydrophobicity in CTD over a relatively wide temperature range presumably results from the presence of the long aliphatic (tetradecanoate) chains in its structure. Importantly, the self-assembled copper tetradecanoate nanostrips can be dip-coated on glass to render it hydrophobic and at the same time retain a significant level of transparency over the entire visible region. Such nanostructured thin films may be expected to find applications not only as a self-cleaning glass, but also as a corrosion resistant coating, in gas storage (due to the layered structure), and as an active catalyst because of the visible absorbance

Degradation Of (Ni,Pt)Al Coatings By Mixture Of Sodium And Potassium Sulfate At 950°C

Environmental stability of β-(Ni,Pt)Al coatings due to combustion by-product of fuel impurities has been examined owing to recent interests in bio-derived (e.g., algae-derived) fuels. Pure sodium sulfates (Na 2SO4), potassium sulfates (K2SO4) and three of their mixtures with different weight ratio were prepared by mechanically grinding, and their high temperature interactions with diffusional Pt-modified β-NiAl coatings were investigated in a laboratory furnace at 950°C. The corroded samples were characterized by X-ray diffraction and scanning electron microscopy equipped with X-ray energy dispersive spectroscopy. The results showed severe damages occurred in the β-(Ni,Pt)Al coatings when the salts were in molten state at 950°C via fluxing mechanism, and accelerated oxidation also occurred when the pure solid state K 2SO4 was in contact with β-(Ni,Pt)Al

Quantitative analysis of Glycyrrhizic acid from a polyherbal preparation using liquid chromatographic technique

Glycyrrhizic acid has been used in Indian traditional medicine for ages. It is obtained from the root extract of Glycyrrhizaglabra. There is seasonal variation of Glycyrrhizic acid content in the roots of the plant. So a proper method for quantification of the same is necessary from the polyherbal preparation available in the market. A simple, rapid, sensitive and specific reverse phase high performance liquid chromatographic method have been developed for the quantitative estimation of glycyrrhizic acid from polyherbal preparation containing aqueous root extract of Glycyrrhizaglabra using a photodiode array detector. The identity confirmation was carried out using mass spectrometry. Baseline resolution of the glycyrrhizic acid peak was achieved on a reverse phase C18 column (125 mm × 4.0 mm, 5 μ) using an isocratic mobile phase consisting of 5.3 mM phosphate buffer and acetonitrile in the ratio 65:35 v/v. Chromatograms were monitored at 252 nm.5.3 mM phosphate buffer was replaced with 0.5mM ammonium acetate buffer in the mobile phase when MS detector was used. The method was found to be linear in the concentration range of 12.4 to124 μg/ml with a correlation co-efficient of 0.999. The limit of detection and the limit of quantitation were 3.08 μg/ml and 10.27 μg/ml respectively. The average recovery from three spike levels was 99.93 ± 0.26%. Identity confirmation of the chromatographic peak was achieved by electrospray ionization mass spectrometry and similar molecular ion peak was obtained for both sample and standard. The developed method is suitable for the routine analysis, stability testing and assay of glycyrrhizic acid from polyherbal preparations containing aqueous extracts of Glycyrrhizaglabra

Application of an Amine Functionalized Biopolymer in the Colonic Delivery of Glycyrrhizin: A Design and In Vivo Efficacy Study

In our current study, a newer amine functionalized guar gum derivative was studied for its efficacy in colonic drug delivery. Glycyrrhizic acid mono-ammonium salt was used as the model drug. Drug-loaded microparticles were formulated by ionic crosslinking using sodium tripolyphosphate. The Scanning Electron Microscopic study revealed spherical particles of sizes from 4.9 ± 3.8 μm to 6.9 ± 3.9 μm. The FT-IR studies presented a possible interaction between the drug and the polymer. The drug was encapsulated in amorphous form as observed from the powder X-Ray Diffraction studies. A cumulative drug release study was carried out in simulated gastric, intestinal, and colonic fluids. The cumulative drug release studies presented a burst release followed by a sustained release of the drug in simulated colonic fluid containing rat cecal contents. The drug-polymer ratio was optimised using a 32 factorial design by taking the amounts of glycyrrhizic acid (X1) and guar gum alkyl amine (X2) as the independant variables. The percent cumulative drug release at 240 mins (Q240), 720 mins (Q720), and at 1,440 mins (Q1440) were considered as the dependant variables. The efficacy of the optimized formulation was studied in a 2,4,6-trinitrobenzene sulfonic acid-induced rat colitis model. The tissue’s nitric oxide, malondialdehyde, and myeloperoxidase activities were found to be much lower in the microparticle-treated group compared to free drug-treated group. The histology of the colonic tissue from the treated group of animals revealed almost no infiltration of inflammatory cells in the tissue for the microparticle-treated group of animals. The synthesized amine derivative of guar gum was found to be better in vitro with a better in vivo efficacy in the colonic delivery of glycyrrhizic acid monoammonium salt and can be considered as a newer modified biopolymer for colonic drug delivery

Chandipura virus perturbs cholesterol homeostasis leading to neuronal apoptosis

Chandipura virus (CHPV; genus Vesiculovirus, family Rhabdoviridae) induces neuronal death through the Fas-mediated extrinsic apoptosis pathway. What propels this apoptosis remains unclear, although oxysterols have been reported to be key players in neurodegeneration. In our study of CHPV-infected brain samples, we observed over-expression of genes such as apolipoprotein E, Cyp46a1, Srebf-1 and Nsdhl. This backs up the hypothesis that CHPV replication demands cholesterol that is supplied by apolipoprotein E through low density lipid receptors, lipid metabolism being pivotal for viral replication. We were able to illustrate this with over-expression of low density lipid receptors in CHPV-infected neurons. An upsurge of cholesterol concentration has been observed in neurons, triggering the expression of Cyp46a1 enzyme and culminating into the conversion of cholesterol to 24(S)-hydroxycholesterol. Increased 24(S)-hydroxycholesterol concentration is toxic to neurons, propelling neuronal apoptosis through the Fas-mediated extrinsic apoptosis pathway. For the first time, perturbation of cholesterol homeostasis in brain is shown to be utilized by the viruses for both maturation and the release of its matured virions outside the cells for continuous neuropathogenesis. Chandipura virus (CHPV) increases cholesterol import through low density lipid (LDL) receptor in neurons. Cholesterol in neurons are utilized to form the CHPV envelope. Excessive accumulation of cholesterol gets converted to 24(S)-hydroxycholesterol (24(S)-OHC) by cholesterol 24-hydroxylase enzyme (encoded by Cyp46a1 gene) that induces neuronal death through apoptosis. Therapeutics aimed against cholesterol homeostasis perturbation may be an effective anti-viral strategy