Search

This article investigates the root causes of the premature failure and replacement of a set of second-stage turbine blades from a heavy industrial gas turbine engine. The investigations included dye-penetrant testing, optical microscopy, X-ray diffractometry (XRD), Environmental Scanning Electron Microscopy (ESEM), and energy dispersive X-ray spectroscopy (EDS) techniques. Moreover, the effect of heat treatment process on restoring the blade microstructure so that the properties were suitable for service was also explored. As a result of the investigation, the second-stage turbine blades premature failure was attributed to the grain boundary secondary phase precipitates. These precipitates were present in the “as-found” condition of the investigated blades.

The current work involves modification of zinc oxide by doping silver, this was achieved by photodeposition method. Modified zinc oxide was investigated using X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Both of ZnO and Ag doped ZnO was fabricated on a cotton texture. The photocatalytic activity of these materials was investigated by following the decolorization of congo red from simulated industrial wastewater. The decolorization of congo red over fabricated-ZnO-Ag was more efficient in comparison with non- fabricated catalysts. Different reaction parameters were undertaken including the effect of pH of the solution, irradiation time and the effect of light intensity. Complete dye removal over fabricated materials took three hours while it took 4.5 for non-fabricated materials.

Six heavy metals namely Cd, Pb, Ni, Zn , Mn and Cu at the upper region of the Euphrates river in Iraq, were determined seasonally during 1993 in selected five stations in water, suspended particles, bottom sediments and aquatic plants. There was clear seasonal variation in their concentrations in filtered water. These concentrations were much higher in the suspended particles with a manifest local variations. While their values in the bottom sediments were much lower than that found in the suspended particles, with clear local variations among the studied stations. Mn was the highest concentration in the sediments among the studied metals at all seasons, whereas Cd was the lowest. Four aquatic plants were also considered and found that they accumulated higher concentrations of Mn and Zn. The status of the heavy metals and their evaluation as a pollutant source in the studied area were discussed.

Plugging material in some of the film cooling channels of a failed aero-gas turbine engine first stage turbine blade is analyzed using the energy dispersive X-ray spectroscopy in an environmental scanning electron microscope. The objective of the analysis was to identify the nature and source of the plugging material that appears to have caused overheating and eventual failure of some of the blades. The results of the analysis indicate that the plugging material, which occurs as a dense aggregate of 0.1 m diameter fibers, is mainly composed of Zr, Y, and O. In addition, the material shows presence of micron size particles dispersed between the fibers. The analysis of the particles indicates they are fluoride-rich compounds, possibly of yttrium or calcium. Small or trace amounts of Ca, Na, and Mg are also observed in the plugging material. The analysis of the areas surrounding the plugged cooling channels shows presence of Cr–Co–Ni–aluminide bond coat and a discontinuous platinum coat over the bond coat. In contrast, the areas surrounding the fractured surface and melted edge show significant presence of calcium fluoride and Mg–Al–silicate. The analysis of melted edge shows presence of all the elements representing various coating layers as well as the impurities; however, Zr and Y were not detected in the melted areas.

Introduction The purpose of the present study was to evaluate postoperative pain after root canal treatment at the Department of Conservative Dentistry, Faculty of Dentistry, University of Khartoum, Sudan. Methods Two hundred thirty-four patients were included in this study; age range was 18–62 years. Conventional endodontic treatment was carried out in the included teeth by the undergraduate dental students in a single visit or multiple visits. The chemomechanical preparation of root canals was done by a modified double-flared technique with combination of hand instruments. Postoperative pain was recorded by each patient by using visual analogue scale in well-defined categories at 2 time intervals, 12 hours and 24 hours. Results Data were analyzed with the χ 2 test. The overall incidence of postoperative pain was 9.0% after 12 hours and 24 hours. Postoperative pain developed in 15.9% of the patients with history of preoperative pain, whereas 7.1% had postoperative pain among those without history of preoperative pain. There was no significant difference in postoperative pain between single-visit and multiple-visit root canal treatment (RCT). Conclusions Within the limitations of the present study there was a low incidence of postoperative pain after conventional RCT. No significant difference exists in postoperative pain after single-visit or multiple-visit RCT.

This work describes the refinery gas turbine cogeneration plant, which is applied in the Arab Gulf area. The measurements have been used to calculate a number of important thermodynamic performance parameters for this plant. These parameters include the steam efficiency, electrical efficiency, net heat rate (NHR), power to heat ratio (PHR), and fuel saving rate (FSR). At full load, the steam and electrical efficiencies are 53.3 adn 28%, respectively, the NHR is equal to 1.33, the PHR is equal to 0.525, and FSR is 0.614. When the plant is operated at part load, all values of thermodynamic parameters are decreased except NHR, which increases to 1.514. The break-even analysis method is presented for the economic analysis. By this method, the total annual cost (TAC) and total annual revenue (TAR) are plotted against the operation hours in a year. The point at which the TAR line crosses the TAR line is called the break-even point in hours of operation. In cases where output is constant (at full load) over the time period considered, the break-even point is 2442 h. When the cogeneration plant runs a different loads, the break-even point is 2926 h. The break-even analysis is used to understand the effects of the variations in fixed and variable costs on the break-even point in hours.

The plasma parameters and ion energy distributions (IED) of the dominant species in an Ar-H2 discharge are investigated with an energy resolved mass spectrometer and a Langmuir probe. The plasmas are generated in a conventional magnetron chamber powered at 150 W, 13.56 MHz at hydrogen flow rates ranging from 0 to 25 sccm with a fixed argon gas flow rate of 15 sccm. Various Hn+, SiHn+, SiHn fragments (with n = 1, 2, 3) together with Ar+ and ArH+ species are detected in the discharge. The most important species for the film deposition is SiHn (with n = 0, 1, 2). H fragments affect the hydrogen content in the material. The flux of Ar+ decreases and the flux of ArH+ increases when the hydrogen flow rate is increased; however, both fluxes saturate at hydrogen flow rates above 15 sccm. Electron density, ne, electron energy, Te, and ion density, ni, are estimated from the Langmuir probe data. Te is below 1.2 eV at hydrogen flow rates below 8 sccm, and about 2 eV at flow rates above 8 sccm. ne and ni decrease wit...

H Hameed, J CassidyBeatson West of Scotland Cancer Centre, Glasgow, Scotland, UKAbstract: Capecitabine (Xeloda®, Roche, Basel, Switzerland) is a pro-drug of 5-fluorouracil (5-FU), and it is converted to 5-FU in the cancer cell by enzymatic degradation. The role of capecitabine in colorectal cancer has evolved in the last 15 years. In early trials in the metastatic setting, capecitabine has shown superior response rates compared with those achieved with 5-FU (Mayo Clinic regimen) (26% vs 17%), with equivalent progression-free survival and overall survival. In the adjuvant setting, the Xeloda in Adjuvant Colon Cancer Therapy (X-ACT) trial demonstrated that capecitabine as a single agent led to improvement in relapse-free survival (hazard ratio: 0.86, 95% confidence interval: 0.74–0.99, P = 0.04) and was associated with significantly fewer adverse events than 5-FU plus leucovorin (LV, folinic acid). On the basis of the X-ACT trial, capecitabine was approved by the United States Food and Drug Administration, the National Institute for Clinical Excellence, and the Scottish Medicines Consortium as monotherapy for the adjuvant treatment of stage III colon cancer. The next step was to incorporate capecitabine into combination therapy. The XELOXA trial studied the combination of capecitabine and oxaliplatin (XELOX) vs 5-FU/LV and demonstrated 5-year disease-free survival of 66% for XELOX, compared with 60% for 5-FU/LV. The toxicity profile was also quite comparable in the two arms. So both the single agent use of capecitabine as well as in combination with oxaliplatin can be considered as part of the standard of care in management of early colon cancer in appropriately selected patient groups.Keywords: 5-fluorouracil, 5-FU, leucovorin, folinic acid, LV, XELOX, oxaliplatin, FOLFOX