Optimization of process parameters of TIG welding of duplex stainless steel without filler rod by grey-Taguchi method

Input parameters of welding have played an important role in producing the quality of welding joint. Welding quality has been improved using proper process parameters with sound knowledge base. Current, welding speed and the shielding gas flow rate have been used as the most important influencing parameters of Tungsten Inert Gas (TIG) welding on Duplex Stainless Steel (DSS). In the present work, multi-objective optimization of TIG welding process parameters of Duplex Stainless Steel - ASTM/UNS 2205 has been determined. These welding process parameters have been optimized to achieve the required quality of DSS welding joints. The quality of the TIG welding on DSS has been evaluated in term of tensile test. The grey-based Taguchi technique has been used to solve this multi- optimization problem. Analysis of Variance (ANOVA) has been applied to evaluate the significanc e of the individual factors on desired results which are ultimate tensile strength, yield strength and percentage of elongation. Additional confirmatory experiment has been done to verify the optimal results. The application possibilities of the grey-based Taguchi method for incessant development of welding quality of DSS in many fields, like chemical industries, oil refineries, gas manufacturing industries etc. have been shown by this work

Optimization of process parameters of TIG welding of duplex stainless steel without filler rod by grey-Taguchi method

385-392Input parameters of welding have played an important role in producing the quality of welding joint. Welding quality has been improved using proper process parameters with sound knowledge base. Current, welding speed and the shielding gas flow rate have been used as the most important influencing parameters of Tungsten Inert Gas (TIG) welding on Duplex Stainless Steel (DSS). In the present work, multi-objective optimization of TIG welding process parameters of Duplex Stainless Steel - ASTM/UNS 2205 has been determined. These welding process parameters have been optimized to achieve the required quality of DSS welding joints. The quality of the TIG welding on DSS has been evaluated in term of tensile test. The grey-based Taguchi technique has been used to solve this multi- optimization problem. Analysis of Variance (ANOVA) has been applied to evaluate the significance of the individual factors on desired results which are ultimate tensile strength, yield strength and percentage of elongation. Additional confirmatory experiment has been done to verify the optimal results. The application possibilities of the grey-based Taguchi method for incessant development of welding quality of DSS in many fields, like chemical industries, oil refineries, gas manufacturing industries etc. have been shown by this work

Fresnel zone plate telescopes for X-ray imaging II: numerical simulations with parallel and diverging beams

We present the results of simulations of shadows cast by a zone plate telescope which may have one to four pairs of zone plates. From the shadows we reconstruct the images under various circumstances. We discuss physical basis of the resolution of the telescope and demonstrate this by our simulations. We allow the source to be at a finite distance (diverging beam) as well as at an infinite distance (parallel beam) and show that the resolution is worsened when the source is nearby. By reconstructing the zone plates in a way that both the zone plates subtend the same solid angles at the source, we obtain back high resolution even for sources at a finite distance. We present simulated results for the observation of the galactic center and show that the sources of varying intensities may be reconstructed with accuracy. Results of these simulations would be of immense use in interpreting the X-ray images from recently launched CORONAS-PHOTON satellite.Comment: 17 pages, 36 figures, Published in Experimental Astronom

Instruments of RT-2 Experiment onboard CORONAS-PHOTON and their test and evaluation V: Onboard software, Data Structure, Telemetry and Telecommand

The onboard software and data communication in the RT-2 Experiment onboard the Coronas-Photon satellite is organized in a hierarchical way to effectively handle and communicate asynchronous data generated by the X-ray detectors. A flexible data handling system is organized in the X-ray detector packages themselves and the processing electronic device, namely RT-2/E, has the necessary intelligence to communicate with the 3 scientific payloads by issuing commands and receiving data. It has direct interfacing with the Satellite systems and issues commands to the detectors and processes the detector data before sending to the satellite systems. The onboard software is configured with several novel features like a) device independent communication scheme, b) loss-less data compression and c) Digital Signal Processor. Functionality of the onboard software along with the data structure, command structure, complex processing scheme etc. are discussed in this paper.Comment: 24 pages, 2 figures, Accepted for publication in Experimental Astronomy (in press

Amphiphilic peptide-based supramolecular, noncytotoxic, stimuli-responsive hydrogels with antibacterial activity

A series of peptides with a long fatty acyl chain covalently attached to the C-terminal part and a free amine (-NH2) group at the N-terminus have been designed so that these molecules can be assembled in aqueous medium by using various noncovalent interactions. Five different peptide amphiphiles with a general chemical formula [H2N-(CH2)nCONH-Phe-CONHC12 (n = 1–5, C12 = dodecylamine)] have been synthesized, characterized, and examined for self-assembly and hydrogelation. All of these molecules [P1 (n = 1), P2 (n = 2), P3 (n = 3), P4 (n = 4), P5 (n = 5)] form thermoresponsive hydrogels in water (pH 6.6) with a nanofibrillar network structure. Interestingly, the hydrogels obtained from compounds P4 and P5 exhibit potential antimicrobial activity against Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis) and Gram-negative bacteria (Escherichia coli). Dose-dependent cell-viability studies using MTT assay (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) by taking human lung carcinoma (A549) cells vividly demonstrates the noncytotoxic nature of these gelator molecules in vitro. Hemolytic studies show nonsignificant or little hemolysis of human erythrocyte cells at the minimum inhibitory concentration (MIC) of these tested bacteria. Interestingly, it has been found that these antibacterial noncytotoxic hydrogels exhibit proteolytic resistance toward the enzymes proteinase K and chymotrypsin. Moreover, the gel strength and gel recovery time have been successfully modulated by varying the alkyl chain length of the N-terminally located amino acid residues. Similarly, the thermal stability of these hydrogels has been nicely tuned by altering the alkyl chain length of the N-terminally located amino acid residues. In the era of antibiotic-resistant strains of bacteria, the discovery of this new class of peptide-based antibacterial, proteolytically stable, injectable, and noncytotoxic soft materials holds future promise for the development of new antibiotics

Role of Subunit Exchange and Electrostatic Interactions on the Chaperone Activity of Mycobacterium leprae HSP18.

Mycobacterium leprae HSP18, a major immunodominant antigen of M. leprae pathogen, is a small heat shock protein. Previously, we reported that HSP18 is a molecular chaperone that prevents aggregation of different chemically and thermally stressed client proteins and assists refolding of denatured enzyme at normal temperature. We also demonstrated that it can efficiently prevent the thermal killing of E. coli at higher temperature. However, molecular mechanism behind the chaperone function of HSP18 is still unclear. Therefore, we studied the structure and chaperone function of HSP18 at normal temperature (25°C) as well as at higher temperatures (31-43°C). Our study revealed that the chaperone function of HSP18 is enhanced significantly with increasing temperature. Far- and near-UV CD experiments suggested that its secondary and tertiary structure remain intact in this temperature range (25-43°C). Besides, temperature has no effect on the static oligomeric size of this protein. Subunit exchange study demonstrated that subunits of HSP18 exchange at 25°C with a rate constant of 0.018 min(-1). Both rate of subunit exchange and chaperone activity of HSP18 is found to increase with rise in temperature. However, the surface hydrophobicity of HSP18 decreases markedly upon heating and has no correlation with its chaperone function in this temperature range. Furthermore, we observed that HSP18 exhibits diminished chaperone function in the presence of NaCl at 25°C. At elevated temperatures, weakening of interactions between HSP18 and stressed client proteins in the presence of NaCl results in greater reduction of its chaperone function. The oligomeric size, rate of subunit exchange and structural stability of HSP18 were also found to decrease when electrostatic interactions were weakened. These results clearly indicated that subunit exchange and electrostatic interactions play a major role in the chaperone function of HSP18

Temperature-dependent chaperone-like activities of <i>M</i>. <i>leprae</i> HSP18.

<p><b>(A)</b> DTT-induced aggregation of 0.35 mg/ml insulin (Ins) in the absence and presence 0.35 mg/ml HSP18 at different temperatures (25, 31, 37 and 43°C). Aggregation was initiated by adding 20 mM DTT and scattering at 400 nm was monitored at the respective temperatures. Trace 1: Ins alone at 25°C; Trace 2: Ins + HSP18 at 25°C; Trace 3: Ins alone at 31°C; Trace 4: Ins + HSP18 at 31°C; Trace 5: Ins alone at 37°C; Trace 6: Ins + HSP18 at 37°C; Trace 7: Ins alone at 43°C; Trace 8: Ins + HSP18 at 43°C; <b>(B)</b> Percent protection ability of <i>M</i>. <i>leprae</i> HSP18 against insulin aggregation at different temperatures. Data are means ± the standard deviation from triplicate determinations. **<i>p</i>< 0.005 and ***<i>p</i>< 0.0005.</p

Secondary structural elements of HSP18 at various temperatures.

<p>Secondary structural elements of HSP18 at various temperatures.</p

Effect of NaCl on the thermal deactivation prevention ability of <i>M</i>. <i>leprae</i> HSP18.

<p>The MDH enzyme activity was measured in the absence and presence of 30 μM HSP18 pre-incubated in the absence or presence of 0.05–0.5 M NaCl while it was thermally denatured at 43°C. Similar assays were also performed with 30 μM BSA alone or pre-incubated with 0.05–0.5 M NaCl. Data are means ± standard deviation from triplicate determinations. *<i>p</i>< 0.05, **<i>p</i>< 0.005.</p

Effect of NaCl on the chaperone activity of <i>M</i>. <i>leprae</i> HSP18.

<p>DTT-induced aggregation of 0.35 mg/ml insulin at 25°C <b>(panel A)</b> and thermal aggregation of 0.06 mg/ml CS at 43°C <b>(panel C)</b> in the absence or presence of different HSP18 samples. Both insulin and citrate synthase are denoted as client proteins. Trace 1: Client protein (CP) alone; Trace 2: CP +HSP18; Trace 3: CP +0.05 M NaCl; Trace 4: CP + HSP18 + 0.05 M NaCl; Trace 5: CP +0.15 M NaCl; Trace 6: CP + HSP18+0.15 M NaCl; Trace 7: CP +0.5 M NaCl; Trace 8: CP + HSP18+0.5 M NaCl. Each data point is the average of triplicate measurements. The percent protection ability of different HSP18 samples against insulin and CS aggregation are presented in panels B and D, respectively. The insulin: HSP18 ratio was 1:1.2 (w/w) and the CS: HSP18 ratio was 1:1.5 (w/w). Data are means ± standard deviation from triplicate determinations. NS = Not significant, *<i>p</i>< 0.05, **<i>p</i>< 0.005 and ***<i>p</i>< 0.0005.</p