Modulatory action of epidermal growth factor on differentiated human granulosa lutein cells: cross-talk between ligand activated receptors for EGF and gonadotropin

A number of local regulatory factors including polypeptide growth factors like epidermal growth factor (EGF) have been suggested to play an active role within the human ovary. In order to understand the physiology of EGFs action, it is essential to demonstrate and characterize the receptors for this growth factor on ovarian cells which was the aim of this study. We demonstrate using [125I]EGF that specific high affinity sites with Ka for this ligand reaching 2.2 x 10(-9) M for growing cultures of human granulosa-lutein cells and 0.13 x 10(-9) M for the membrane fraction prepared from these cells. Additionally we have identified a 170 kD protein as the EGF receptor with the help of affinity cross linking and immunoblotting procedures. Furthermore, we observed that a pretreatment of granulosa lutein cells with EGF for a short duration (0-30 min) leads to a dose- and time dependent upregulation of the LH-receptor-coupled adenylate cyclase activity. A maximal effect (159 +/- 12% increase compared with untreated cells, P < 0.001, n = 4) was reached at 10-15 min with 10-20 ng/ml EGF. Specific inhibition of the receptor tyrosine kinase activity abolished the observed EGF-induced sensitization of the cyclase activity. Differentiation of granulosa cells in vivo is a prerequisite for ovulation and later transformation into highly differentiated lutein cells, a process depending on the presence of ligands that elevate cAMP production. The observed modulation of the adenylate cyclase by EGF could be a regulatory component for the differentiated status of the granulosa cells during different phases of the cycle.     

On line fatigue life monitoring methodology for power plant components

Fatigue is one of the most important aging effects of power plant components. Information about fatigue helps in assessing structural degradation of the components and so assists in planning in-service inspection and maintenance. It may also support the future life extension programme of a power plant. In the present paper, the development of a methodology for on line fatigue life monitoring using available plant instrumentation is presented. The Green's function technique is used to convert plant data to stress-time data. Using a rainflow cycle counting method, stress-time data are analysed and the fatigue usage factor is computed from the material fatigue curve. Various codes are developed to generate Green's functions, to convert plant data to stress-time data, to find the fatigue usage factor and to display fatigue information. Using the developed codes, information about the fatigue life of various components of a power plant can be updated, stored and displayed interactively by plant operators.

Three different case studies are reported in the present paper. These are the fatigue analyses of a thick pipe, of a nozzle connected to a pressure vessel and of a reducer connecting a heat exchanger to its piping system.     

Effect of inhibitors on flammability range of flames produced from LPG/air mixtures

Burning velocities of Liquefied Petroleum Gas/air flames of different fuel/air compositions have been measured by the flat-flame method originally developed by Egerton and Powling, and the effects of inhibitors such as chlorinated hydrocarbons (chloroform, methylene dichloride, carbon tetrachloride) on the burning velocities have been investigated. The flammability limits at different fuel/air compositions have also been measured. The difference between upper and lower limits of flammability was narrowed by the addition of inhibitors in the order carbon tetrachloride chloroform methylene dichloride, i.e. the inhibiting effect increased with increase in the number of chlorine atoms. The relative effectiveness of different inhibitors has been expressed as an inhibition efficiency, and it has been found that an interesting correlation exists between the inhibition efficiency (also the narrowing of limits, and the maximum burning velocity) and the number of (dissociable) chlorine atoms present in the molecule of inhibiting compound. Other factors were the degree of dissociation of the inhibiting molecule in the flame, and the concentration of the inhibitor in the fuel/air mixture; the effect of small concentrations was that of specific chemical inhibition whereas at higher concentrations dilution effects were dominant. At the upper limit the flame has maximum tendency to flash back in an ordinary burner and the combustion wave may develop into a detonation wave inducing an explosion hazard. Hence upper explosion limit may be considered an index of explosion risk. The inhibitors lower this largely by reducing the concentration of free radicals in the flame boundary, increasing the difficulty of ignition, and thus increasing safety. A large difference has been found between the experimental and calculated value of the upper limit for the pure gas, probably owing to the chemical effects of ethylene via production of acetaldehyde which catalyses the combustion.     

Structural evolution in mechanically alloyed Al-Fe powders

The structural evolution in mechanically alloyed binary aluminum-iron powder mixtures containing 1, 4, 7.3, 10.7, and 25 at. pct Fe was investigated using X-ray diffraction (XRD) and electron microscopic techniques. The constitution (number and identity of phases present), microstructure (crystal size, particle size), and transformation behavior of the powders on annealing were studied. The solid solubility of Fe in Al has been extended up to at least 4.5 at. pct, which is close to that observed using rapid solidification (RS) (4.4 at. pct), compared with the equilibrium value of 0.025 at. pct Fe at room temperature. Nanometer-sized grains were observed in as-milled crystalline powders in all compositions. Increasing the ball-to-powder weight ratio (BPR) resulted in a faster rate of decrease of crystal size. A fully amorphous phase was obtained in the Al-25 at. pct Fe composition, and a mixed amorphous phase plus solid solution of Fe in Al was developed in the Al-10.7 at. pct Fe alloy, agreeing well with the predictions made using the semiempirical Miedema model. Heat treatment of the mechanically alloyed powders containing the supersaturated solid solution or the amorphous phase resulted in the formation of the Al₃Fe intermetallic in all but the Al-25 at. pct Fe powders. In the Al-25 at. pct Fe powder, formation of nanocrystalline Al₅Fe₂ was observed directly by milling. Electron microscope studies of the shock-consolidated mechanically alloyed Al-10.7 and 25 at. pct Fe powders indicated that nanometer-sized grains were retained after compaction.     

Torsional refilling transitions in tea-pumped CH3OH fir lasers with associated high-resolution fir spectra

It is proposed that a number of the high-frequency far-infrared (FIR) laser lines observed when CH₃OH is optically pumped by high-power CO₂ TEA lasers can be identified as refilling torsional transitions within the vibrational ground state. Assignments are presented for 8 such TEA-pump/FIR-laser refilling systems. To provide support for the assigned laser frequencies, high-resolution Fourier transform FIR spectra of CH₃OH have been obtained and partially analyzed in the torsional transition region.     

Helium sources and recovery processes - with special reference to India

Helium plays an important role in a variety of processes. Its only widely exploited source is natural gas with a helium content of 1–8%. Postulated, increased demand has stimulated interest in both novel sources and extraction techniques.Existing and new methods of helium recovery from natural gas are discussed. There is particular attention paid to pilot plants for helium extraction from monazite mineral and thermal springs in India.