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113 results on '"Mamun, M.A."'

24. Unreplicated DNA remaining from unperturbed S phases passes through mitosis for resolution in daughter cells

Author

Moreno, A. Carrington, J.T. Albergante, L. Mamun, M.A. Haagensen, E.J. Komseli, E.-S. Gorgoulis, V.G. Newman, T.J. Blow, J.J.

Abstract

To prevent rereplication of genomic segments, the eukaryotic cell cycle is divided into two nonoverlapping phases. During late mitosis and G1 replication origins are "licensed" by loading MCM2-7 double hexamers and during S phase licensed replication origins activate to initiate bidirectional replication forks. Replication forks can stall irreversibly, and if two converging forks stall with no intervening licensed origin-a "double fork stall" (DFS)-replication cannot be completed by conventional means. We previously showed how the distribution of replication origins in yeasts promotes complete genome replication even in the presence of irreversible fork stalling. This analysis predicts that DFSs are rare in yeasts but highly likely in large mammalian genomes. Here we show that complementary strand synthesis in early mitosis, ultrafine anaphase bridges, and G1-specific p53-binding protein 1 (53BP1) nuclear bodies provide a mechanism for resolving unreplicated DNA at DFSs in human cells. When origin number was experimentally altered, the number of these structures closely agreed with theoretical predictions of DFSs. The 53BP1 is preferentially bound to larger replicons, where the probability of DFSs is higher. Loss of 53BP1 caused hypersensitivity to licensing inhibition when replication origins were removed. These results provide a striking convergence of experimental and theoretical evidence that unreplicated DNA can pass through mitosis for resolution in the following cell cycle.

Published
2016

29. Nanoindentation investigation of the reactive pulsed laser deposited superconducting niobium nitride thin films

Author

Mamun M.A., Farha A.H., Ufuktepe Y., Kimura S.I., Hajiri T., Imura K., Karadag F., and Çukurova Üniversitesi

Subjects
Superconductivity, Hardness, XRD, NbN, TEM, XPS, AFM, PLD, UPS, Modulus, Nanoindentation
Abstract

142nd Annual Meeting and Exhibition: Linking Science and Technology for Global Solutions, TMS 2013 --3 March 2013 through 7 March 2013 -- San Antonio, TX -- Nanomechanical properties were investigated for the reactive pulsed laser deposited (PLD) superconducting NbNx thin films grown on Si(100) at constant substrate temperature of 800°C using three different background nitrogen gas pressures (200, 400 and 500 mTorr). The Cross-sectional transmission electron microscopy (TEM), X-ray diffraction (XRD), and atomic force microscopy (AFM) were employed to characterize the films' surface structure and morphology. Superconductivity was determined by performing resistance measurements. Nanoindentation technique was used to evaluate the hardness and modulus of the films. The results indicate that the background pressure impacted the crystalline quality, morphology, superconductivity and the hardness of the films. As the background pressure increases to 500 mTorr, improved superconducting properties and higher hardness (17.5±1.5 GPa at 20 nm depth) values were reported as compared to the other two samples.

Published
2013

43. Post impoundment changes in the fish fauna of Kaptai reservoir, Bangladesh

Author

Ahmed, K.K., Mamun, M.A., Haque, M.E., and Alamgir, M.

Subjects
Kaptai reservoir, Fisheries, Fish fauna, Post impoundment change, Biology
Abstract

Based on the present investigation and reviewing the published and unpublished documents critically, this communication considers the post impoundment changes in the fish fauna of Kaptai reservoir. Investigation reveals that a total of 73 species of fish belongs to 47 genera, 25 families and 2 species of prawn are present in the reservoir. Of them, 31 are commercially important, 6 and 9 species are newly identified.

Published
2003

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