Browsing by Author "T. Mukherjee"

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Absence of novel translation products in relation to induced activity of the 93D puff in Drosophila melanogaster
(Springer-Verlag, 1982) S.C. Lakhotia; T. Mukherjee
Salivary glands of Drosophila larvae were treated in vitro with benzamide or with a homogenate of heat shocked glands to specifically induce high transcriptional activity of the 93D puff. The newly synthesized 14C-amino acids labelled polypeptides in the treated and sister control glands were analysed by polyacrylamide gel electrophoresis, followed by gel autoradiography. The protein synthesis patterns in the treated glands in either case remain the same as in control glands. No novel polypeptide was seen which could be correlated with the high induced transcriptional activity of the 93D puff. This suggests that the 93D transcript/s is/are probably not translated. © 1982 Springer-Verlag.
Influence of Long Term Ageing and Superimposed Creep Stress on the Microstructure of 1 mass%Cr -0.5 Mass%Mo Steel
(1992) N. Gope; T. Mukherjee; D.S. Sarma
In order to understand the effects of high temperature ageing and that of superimposed creep stress on the microstructural variations in a 1 mass%Cr-0.5 mass%Mo steel, the shoulder and gage portions of the specimens, subjected to stress rupture tests at 520 and 560°C were studied by transmission electron microscopy. The optical microstructure of the steel consists of 30 percent ferrite and the remainder bainite. The ferrite is free from any precipitates and ferrite laths with a high dislocation density are frequently observed adjacent to bainite. The bainitic carbide is cementite in a plate-like morphology. Ageing at 520°C upto 10151 h with or without the superimposed creep stress do not bring about any noticeable change in either ferrite or bainite. While ageing at 560°C for 1235 h has not brought about any significant change in microstructure, the superimposed creep stress has led to the precipitation of fine M2C platelets in ferrite and some recovery of ferrite matrix. The exposure at 560°C, for 34667 h with or without creep stress, has led to the precipitation of M2C and M6C in ferrite. The superimposed creep stress has, however, shortened the length of M2C, but increased its profuseness. The long term exposure at 560°C with or without creep stress also led to significant recovery of ferrite and increased spheroidization of cementitie. © 1992, The Japan Institute of Metals. All rights reserved.
Influence of long- term aging and superimposed creep
(1992) N. Gope; T. Mukherjee; D.S. Sarma
In an effort to understand the effects of long-term aging at high temperatures and those of the superimposed creep stresses on the microstructural variations in a 0.50Cr-0.50Mo-0.25V steel, the shoulder and gage portions of the specimens subjected to stress rupture tests at 500 °C and 540 °C have been studied by transmission electron microscopy. The optical microstructure, in the normalized and tempered condition, consists of about 95 pct ferrite with the remainder bainite. The ferrite has an extremely fine precipitation of vanadium carbide (VC) as interphase precipitate as well as in random distribution. In the bainitic area, M 3C is present in the globular as well as plate-like morphology. Specimens ruptured at 500 °C and 540 °C were selected for transmission electron microscopic study. Both the interphase precipitates and randomly distrib- uted precipitates of VC coarsen considerably due to prolonged exposure at elevated tempera- tures, and ultimately fine M 2C platelets nucleate and grow on either side of these precipitates, resulting in the formation of the so-called H-carbides. The superimposed creep stress has a marginal effect on the coarsening kinetics of VC but has enhanced its precipitation along dis- locations and has promoted the formation of H-carbides. © 1992 The Minerals, Metals and Materials Society, and ASM International.
Influence of long-term aging and superimposed creep stress on the microstructure of 2.25cr-1Mo steel
(Springer-Verlag, 1993) N. Gope; Amit Chatterjee; T. Mukherjee; D.S. Sarma
To understand the influence of high-temperature aging and superimposed creep stress on the microstructural variations in a 2.25Cr-1Mo steel, the shoulder and gage portions of the specimens subjected to stress-rupture tests at 540 °C and 580 °C have been studied by transmission electron microscopy. In the normalized and tempered condition, the steel exhibited a tempered bainitic structure and the carbides were present as M3C globules, M2C platelets, and M23C6 rectangular parallelepipeds. Aging the steel at 540 °C for 7022 hours or 17,946 hours resulted in considerable coarsening of M2C and caused precipitation of M6C carbides. The superimposed creep stress enhanced the M2C precipitation. The ferrite matrix exhibited some recovery in the specimens exposed for 17,946 hours. While M2C platelets were observed in a few areas after 14,836 hours of aging at 580 °C, this carbide was virtually nonexistent when a stress of 78 MPa was superimposed. Amounts of M23C6 persisted throughout the tests at both 540 °C and 580 °C. The M6C carbide became more predominant after long exposure at 580 °C. The ferrite matrix recovered considerably in specimens subjected to creep stress at 580 °C for 14,836 hours. © 1993 The Minerals, Metals and Materials Society, and ASM International.
Influence of long-term aging at 520 °C and 560 °C and the superimposed creep stress on the microstructure of 1.25Cr-0.5Mo steel
(Springer-Verlag, 1992) N. Gope; T. Mukherjee; D.S. Sarma
In order to understand the influence of high-temperature aging effects and those of the superimposed creep stress on the microstructural variations in a 1.25Cr-0.5Mo steel, the shoulder as well as gage portions of specimens subjected to stress-rupture tests at 520 °C and 560 °C have been studied by transmission electron microscopy. In the normalized and tempered condition, the microstructure of the steel consists of 90 pct ferrite and 10 pct bainite, and M3C is the only carbide present in bainite and at a few ferrite grain boundaries. On aging at 520 °C for 5442 hours, Cr2N precipitates in a fibrous form at ferrite-bainite interfaces, and the creep stress has enhanced this mode of precipitation. On holding for 13,928 hours at 520 °C, fibrous carbide is still present but its composition has changed to Mo2C, while the superimposed creep stress has promoted the precipitation of Mo2C needles with fine globular precipitates of M23C6. Aging at 560 °C for 1854 or 10,338 hours has resulted in the precipitation of longer Mo2C needles and ellipsoidal M23C6 carbide precipitation; the superimposed creep stress has resulted in a more dense precipitation of shorter needles in both cases. There is some recovery of bainitic ferrite at 560 °C, though the cementite coarsening is negligible. © 1992 The Minerals, Metals and Materials Society, and ASM International.
Specific activation of puff 93 D of Drosophila melanogaster by benzamide and the effect of benzamide treatment on the heat shock induced puffing activity
(Springer-Verlag, 1980) S.C. Lakhotia; T. Mukherjee
A 10 or 20 min in vitro treatment of salivary glands of late 3rd instar larvae of Drosophila melanogaster with l mg/ml benzamide (BM) at 24° C results in the specific induction of the 93 D puff and at the same time all other chromosomal RNA synthesis is severely repressed. Incorporation of 3H-uridine in the nucleolus is not affected. In glands heat shocked (37° C) for 20 min in presence of BM, all the temperature shock (TS) puffs are induced but they incorporate 3H-uridine to a lesser extent than in glands heat shocked in absence of BM. The 93 D puff, which is highly induced by either of the treatments alone, is relatively less active in glands exposed to TS and BM simultaneously. When a 10 min BM treatment (at 24° C) precedes a 20 min TS or when the BM treatment follows TS, the 3H-uridine incorporation on all TS puffs is relatively less and significantly, in both cases, the 87 C puff is much less active (more so in TS followed by BM treated glands) than the 87 A puff. Also, in both these treatments, the 93 D puff does not show any additive effect of the BM and TS treatments. These observations are discussed in the light of possible role of the 93 D puff in modulating the heat shock response. © 1980 Springer-Verlag.
Specific induction of the 93D puff in Drosophila melanogaster by a homogenate of heat shocked larval salivary glands
(1981) T. Mukherjee; S.C. Lakhotia
[No abstract available]