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Nitai Chandra Adak,Kamalkishor Janardhanji Uke,Tapas Kuila,Pranab Samanta,이중희 한국복합재료학회 2018 Composites research Vol.31 No.6
In the present study, the effect of GO in damping capacity of CF/epoxy laminates was studied via free vibration analysis. The composite laminates were manufactured by using vacuum assisted resin transfer molding technique. The damping properties of the prepared hybrid composites were determined in terms of natural frequency and damping ratio in free vibration test. The foremost aspire of this investigation was to compare the vibration properties i.e. natural frequency and modal damping of the prepared composites with the numerical results. The numerical study was carried out via FEA using ANSYSTM workbench software. The parametric study of the numerical models was also studied considering the beam free length and the beam thickness. It was found that the incorporation of GO enhanced the damping capacity of the composite and the variation of natural frequencies in mode1varied by 2- 5% compared to the experimental study.
Adak, Nitai Chandra,Chhetri, Suman,Kuila, Tapas,Murmu, Naresh Chandra,Samanta, Pranab,Lee, Joong Hee Elsevier 2018 Composites. Part B, Engineering Vol.149 No.-
<P><B>Abstract</B></P> <P>In this work, the hybridization effects of hydrazine reduced graphene oxide (rGO) on the inter-laminar shear strength (ILSS), impact strength, and in-plane fracture toughness of symmetric type carbon fiber/epoxy composite (CF/epoxy) laminates were investigated. The composite laminates were fabricated through the vacuum-assisted resin transfer molding (VARTM) process. At 0.2 wt% of rGO loading, the CF/epoxy composites showed the best load carrying capacity among the developed laminates. ILSS, impact strength, and critical stress intensity factor (<I>K</I> <SUB> <I>IC</I> </SUB>) were enhanced by ∼ (84, 100, and 33) %, respectively, in the case of rGO (0.2 wt%) filled CF/epoxy composite specimens, as compared to CF/epoxy composite. The consumed fracture energy of rGO (0.2 wt%)/CF/epoxy increased, as compared to the rGO (0.4 wt%)/CF/epoxy composite. The fracture surfaces obtained from field emission scanning electron microscopy of the developed composites showed compatible dispersion of rGO in the epoxy matrix, and branched fracture of the specimens. This study suggests that the rGO nanofiller might be used as a matrix modifier to resist matrix fracture, as well as fiber fracture.</P>
Adak, Nitai Chandra,Chhetri, Suman,Kim, Nam Hoon,Murmu, Naresh Chandra,Samanta, Pranab,Kuila, Tapas Springer-Verlag 2018 Journal of materials engineering and performance Vol.27 No.3
<P>This study investigates the synergistic effects of graphene oxide (GO) on the woven carbon fiber (CF)-reinforced epoxy composites. The GO nanofiller was incorporated into the epoxy resin with variations in the content, and the CF/epoxy composites were manufactured using a vacuum-assisted resin transfer molding process and then cured at 70 and 120 A degrees C. An analysis of the mechanical properties of the GO (0.2 wt.%)/CF/epoxy composites showed an improvement in the tensile strength, Young's modulus, toughness, flexural strength and flexural modulus by similar to 34, 20, 83, 55 and 31%, respectively, when compared to the CF/epoxy composite. The dynamic mechanical analysis of the composites exhibited an enhancement of similar to 56, 114 and 22% in the storage modulus, loss modulus and damping capacity (tan delta), respectively, at its glass transition temperature. The fiber-matrix interaction was studied using a Cole-Cole plot analysis.</P>
Cloning and Characterization of the Promoters of Temperate Mycobacteriophage L1
( Chandrani Chattopadhyay ),( Subrata Sau ),( Nitai C. Mandal ) 생화학분자생물학회 2003 BMB Reports Vol.36 No.6
Four putative promoters of the temperate mycobacteriophage L1 were cloned by detecting the β-galactosidase reporter expression in E. coli transformants that carried L1 specific operon-fusion library. All of the four L1 promoters were also found to express differentially in the homologous environment of mycobacteria. Of the four promoters, two were suggested to be the putative early promoters of L1 since they express within 0 to 10 inin of the initiation of the lytic growth of L1. One of the putative early promoters showed a relatively better and almost identical activity in both E. coli and M. smegmatis. By a sequence analysis, we suggest that the L1 insert that contained the stronger early promoter possibly carries two convergent E. coli σ^(70)-like L1 promoters, which are separated from each other by about 300 nucleotides. One of them is the early promoter of L1 as it showed a 100% similarity with the early P_)left) promoter of the homoimmune phage L5. The second promoter, designated P4, was suggested for its appreciable level of reporter activity in the absence of the -10 element of the P_(left) equivalent of L1. By analyzing most of the best characterized mycobacteriophages-specific promoters, including the L1 promoter P4, we suggest that both the - 10 and -35 hexamers of the mycobacteriophage promoters are highly conserved and almost similar to the consensus - 10 and -35 hexamers of the E. coli σ^(70) promoters.
Chhetri, Suman,Adak, Nitai Chandra,Samanta, Pranab,Murmu, Naresh Chandra,Hui, David,Kuila, Tapas,Lee, Joong Hee Elsevier 2018 Composites Part B, Engineering Vol.143 No.-
<P><B>Abstract</B></P> <P>Nacre-like graphene nanosheets (GNS) obtained from the <SMALL>L</SMALL>-glutathione mediated reduction of graphene oxide (GO) were used to develop epoxy composites. Field emission scanning electron microscopy (FE-SEM) revealed the layer-by-layer nacre-like structure of GNS. Fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), Raman spectroscopy, and thermogravimetric analysis (TGA) measurements confirmed the successful reduction of GO. The oxidized product of <SMALL>L</SMALL>-glutathione is expected to perform as capping agent to stabilize the GNS, and also stitches the graphene sheets through hydrogen bonding. Transmission electron microscopy was used to confirm the dispersion of GNS in the epoxy matrix. The GNS/epoxy composites showed significant improvement of ∼91% in fracture toughness (K<SUB>IC</SUB>), 46% in flexural strength, and 71% in flexural modulus at 0.25 wt% GNS loadings. The probable toughening mechanism was elucidated from fracture FE-SEM images. The improved compatibility and strong interfacial interaction were reflected in the enhanced storage modulus value. The thermal stability of the composites as investigated by TGA showed appreciable improvement in the degradation temperature.</P>
Purification and Characterization of a Deoxyriboendonuclease from Mycobacterium smegmatis
Mandal, Prajna,Chakraborty, Phulghuri,Sau, Subrata,Mandal, Nitai Chandra Korean Society for Biochemistry and Molecular Biol 2006 Journal of biochemistry and molecular biology Vol.39 No.2
A deoxyriboendonuclease has been purified to near homogeneity from a fast growing mycobacterium species, M. smegmatis and characterized to some extent. The size of enzyme is about 43 kDa as determined by a denaturing gel analysis. It shows optimum activity at $32^{\circ}C$ in Tris-HCl buffer (pH 7.2) containing 2.5 mM of $MgCl_2$. Both EDTA and $K^+$ but not $Na^+$ inhibit its activity. Evidences show that the enzyme is not a restriction endonuclease but catalyzes the endonucleolytic cleavage of both the double- as well as the single-strand DNA non-specifically. It has been shown that the cleavage by this enzyme generates DNA fragments carrying phosphate groups at 5' ends and hydroxyl group at the 3' ends, respectively. Analysis reveals that no endonuclease having size and property identical to our deoxyriboendonuclease had been purified from M. smegmatis before. The property of our enzymes closely matches with the deoxyriboendonucleases purified from diverse sources including bacteria.