Simultaneous Transitions in Cuprate Momentum-Space Topology and Electronic Symmetry Breaking

Fujita, K.,Kim, Chung Koo,Lee, Inhee,Lee, Jinho,Hamidian, M. H.,Firmo, I. A.,Mukhopadhyay, S.,Eisaki, H.,Uchida, S.,Lawler, M. J.,Kim, E.-A.,Davis, J. C. American Association for the Advancement of Scienc 2014 Science Vol.344 No.6184

<P><B>Under the Dome</B></P><P>The superconducting transition temperature <I>T<SUB>c</SUB></I> of copper oxides has a dome-shaped dependence on chemical doping. Whether there is a quantum critical point (QCP) beneath the dome, and whether it is related to the enigmatic pseudogap, has been heavily debated. Two papers address this question in two different families of Bi-based cuprates. In (Bi,Pb)<SUB>2</SUB>(Sr,La)<SUB>2</SUB>CuO<SUB>6+δ</SUB>, <B>He <I>et al.</I></B> (p. 608) found that the Fermi surface (FS) undergoes a topological change as doping is increased, which points to the existence of a QCP at a doping close to the maximum in <I>T<SUB>c</SUB></I>, seemingly uncorrelated with the pseudogap. <B>Fujita <I>et al.</I></B> (p. 612) studied a range of dopings in Bi<SUB>2</SUB>Sr<SUB>2</SUB>CaCu<SUB>2</SUB>O<SUB>8+δ</SUB> to find an FS reconstruction simultaneous with the disappearance of both rotational and translational symmetry breaking, the latter of which has been associated with the pseudogap. These findings point to a concealed QCP.</P>

Characterisation of PMMA microfluidic channels and devices fabricated by hot embossing and sealed by direct bonding

A. Mathur,S.S. Roy,M. Tweedie,S. Mukhopadhyay,S.K. Mitra,J.A. McLaughlin 한국물리학회 2009 Current Applied Physics Vol.9 No.6

In this study we fabricated a silicon-based stamp with various microchannel arrays, and demonstrated successful replication of the stamp microstructure on poly methyl methacrylate (PMMA) substrates. We used maskless UV lithography for the production of the micro-structured stamp. Thermal imprint lithography was used to fabricate microfeatured fluidic platforms on PMMA substrates, as well as to bond PMMA lids on the fluidic platforms. The microfeature in the silicon-based (silicon wafer coated with SU- 8) stamp includes microchannel arrays of approximately 30 ㎛ in depth and 5 mm in width. We produced various channels without pillars, as well as with SU-8 pillars in the range of 50–100 ㎛ wide and 6 ㎛ in height. PMMA discs of 1 mm thickness were utilized as the molding substrate. We found 10 kN applied force and 100 ℃ embossing temperature were optimum for transferring the microstructure to the PMMA substrate. In this study we fabricated a silicon-based stamp with various microchannel arrays, and demonstrated successful replication of the stamp microstructure on poly methyl methacrylate (PMMA) substrates. We used maskless UV lithography for the production of the micro-structured stamp. Thermal imprint lithography was used to fabricate microfeatured fluidic platforms on PMMA substrates, as well as to bond PMMA lids on the fluidic platforms. The microfeature in the silicon-based (silicon wafer coated with SU- 8) stamp includes microchannel arrays of approximately 30 ㎛ in depth and 5 mm in width. We produced various channels without pillars, as well as with SU-8 pillars in the range of 50–100 ㎛ wide and 6 ㎛ in height. PMMA discs of 1 mm thickness were utilized as the molding substrate. We found 10 kN applied force and 100 ℃ embossing temperature were optimum for transferring the microstructure to the PMMA substrate.

Subfertility in Males: An Important Cause of Bull Disposal in Bovines

Mukhopadhyay, C.S.,Gupta, A.K.,Yadav, B.R.,Khate, K.,Raina, V.S.,Mohanty, T.K.,Dubey, P.P. Asian Australasian Association of Animal Productio 2010 Animal Bioscience Vol.23 No.4

The study had two objectives, namely, to estimate the andrological disorders leading to disposal of Karan Fries (KF), Sahiwal cattle and Murrah buffalo bulls and to study the effect of various factors (species/breeds, season of birth and period of birth) on male reproductive parameters. Records on occurrence of subfertility problems and disposal pattern of bulls maintained at the National Dairy Research Institute herd were collected for 15 years (1991 to 2005). Percentage of bulls producing freezable semen was less in the crossbred cattle (58.46%) as compared to Sahiwal (81.69%) and Murrah bulls (81.05%). Various subfertility traits like poor libido and unacceptable seminal profile were found to be the significant reasons (p<0.01) for culling of the breeding bulls. Inadequate sex drive was the main contributing factor for bull disposal in Sahiwal (22.55%) and Murrah bulls (15.12%) whereas poor semen quality and freezability were most frequently observed in KF bulls (24.29 and 7.29 percent, respectively). Least squares analyses of different male reproductive parameters showed that species/breeds had significant effect (p<0.05) on all traits except for frozen semen production periods (FSPP). Periods of birth were significantly different (p<0.05) for all traits except for semen volume. Age at first semen collection (AFSC), age at first semen freezing (AFSF) and age at disposal (AD) were highest in Murrah, while frozen semen production period (FSPP) and semen production period (SPP) were highest in KF and lowest in Sahiwal. The age at first semen donation and breeding period could be reduced by introducing the bulls to training at an early age. These results revealed a declining trend in AFSC, AFSF, FSPP, SPP and AD, thereby indicating an improvement in reproductive performance over the years. The age at first semen donation in bovines can be reduced by introducing the young male calves to training at an early age, which could increase the dosage of semen obtained from each male.

Random topological defects in double-walled carbon nanotubes: On characterization and programmable defect-engineering of spatio-mechanical properties

A. Roy,K. K. Gupta,S. Dey,T. Mukhopadhyay Techno-Press 2024 Advances in nano research Vol.16 No.1

Carbon nanotubes are drawing wide attention of research communities and several industries due to their versatile capabilities covering mechanical and other multi-physical properties. However, owing to extreme operating conditions of the synthesis process of these nanostructures, they are often imposed with certain inevitable structural deformities such as single vacancy and nanopore defects. These random irregularities limit the intended functionalities of carbon nanotubes severely. In this article, we investigate the mechanical behaviour of double-wall carbon nanotubes (DWCNT) under the influence of arbitrarily distributed single vacancy and nanopore defects in the outer wall, inner wall, and both the walls. Large-scale molecular simulations reveal that the nanopore defects have more detrimental effects on the mechanical behaviour of DWCNTs, while the defects in the inner wall of DWCNTs make the nanostructures more vulnerable to withstand high longitudinal deformation. From a different perspective, to exploit the mechanics of damage for achieving defect-induced shape modulation and region-wise deformation control, we have further explored the localized longitudinal and transverse spatial effects of DWCNT by designing the defects for their regional distribution. The comprehensive numerical results of the present study would lead to the characterization of the critical mechanical properties of DWCNTs under the presence of inevitable intrinsic defects along with the aspect of defect-induced spatial modulation of shapes for prospective applications in a range of nanoelectromechanical systems and devices.

Friction Stir Welding of Thick AA2519 Alloy: Defect Elimination, Mechanical and Micro‑Structural Characterization

Mohammed Ubaid,Dhruv Bajaj,A. K. Mukhopadhyay,Arshad Noor Siddiquee 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.12

Friction stir welding (FSW) of thick aluminium sections will pave way for remarkable new defence applications, providedthe accompanying challenges are successfully addressed. These challenges include elimination of tunnel defects, loss ofstrength in heat-treatable aluminium alloys, tool design and excessive process forces. Accounts of defect elimination, detailedmicro-structural and mechanical characterization for thick section FSW are scarce in the published literature. Further, specialstrategies such as bobbin tool, pre-drilled hole for plunging and inverted double pass are generally deployed to overcomethese challenges. This makes the process less productive and complex. In the present work, armor grade aluminum alloyAA2519-T87 plates having a thickness of 15.4 mm have been successfully joined with a joint efficiency of greater than 75%without supplementary strategies. The disparity in the effects of tool rotational speed and welding speed in the formation ofa sound weld has been addressed in detail to enhance the understanding of FSW of thick sections. Micro-hardness measurementshave been carried out throughout the transverse cross-section of the welds and correlated with different zones andtheir corresponding microstructures. Scanning electron microscopy and X-ray energy dispersive spectroscopy have beenused to characterize the coarse phase particles present in the weld zones.

Dynamics of lockstitch sewing process

Midha, Vinay Kumar,Mukhopadhyay, A.,Chattopadhyay, R.,Kothari, V.K. 服飾文化學會 2013 服飾文化硏究 Vol.21 No.6

During high speed sewing, the needle thread is exposed to dynamic loading, short strike loading, inertia forces, friction, rubbing, force of check spring, bending, pressure, friction, impact, shock and thermal influence. The dynamic thread loading/tension alters throughout the stitch formation cycle and along its passage through the machine. The greatest tensile force occurs at the moment of stitch stretching, when the take up lever pulls for required thread length through the tension regulator. These stresses act on the thread repeatedly and the thread passes 50-80 times through the fabric, the needle eye and the bobbin case mechanism, before getting incorporated into the seam, which result in upto 40% loss in tensile strength of the sewing thread. This damage in the sewing thread adversely affects its processing and functional performance. In this paper, the contribution of dynamic loading, passage through needle and fabric, and bobbin thread interaction in the loss in tensile properties has been studied. It is observed that the loss in tensile properties occurs mainly due to the bobbin thread interaction. Dynamic loading due to the action of take up lever also causes substantial loss in tenacity and breaking elongation of cotton threads.

Influence of Retrogression and Re-aging on the Exfoliation Corrosion Behavior of AA 7085 Sheets

( Ajay Krishnan ),( V. S. Raja ),( A. K. Mukhopadhyay ) 한국부식방식학회(구 한국부식학회) 2016 Corrosion Science and Technology Vol.15 No.4

An attempt has been made to understand the influence of retrogression and re-aging (RRA) on the exfoliation corrosion behaviour of AA 7085 alloy in comparison with the peak aged condition (PA). Immersion tests using ASTM G34 and studies involving electrochemical impedance spectroscopy showed that the RRA treated alloy provided higher resistance to exfoliation corrosion than the PA treated alloy. The improved resistance was attributed to the enhanced Cu content and the discontinuous nature of the grain boundary precipitate, which was revealed through transmission electron microscopy.