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Investigation of electrical, mechanical, and thermal properties of functionalized multiwalled carbon nanotubes-reduced graphene Oxide/PMMA hybrid nanocomposites
No full textElectrical, mechanical, and thermal properties of the poly(methyl methacrylate) (PMMA) composites containing functionalized multiwalled carbon nanotubes (f-MWCNTs) and reduced graphene oxide (rGO) hybrid nanofillers have been investigated. The observed electrical percolation threshold of FHC is 0.8 wt% with maximum conductivity of 1.21 x 10(-3) S/cm at 4 wt% of f-MWCNTs. The electrical transport mechanism and magneto resistance studied of hybrid composites have also been investigated. Progressive addition of f-MWCNTs in rGO/PMMA composite results increase in mechanical (tensile strength and Young's modulus) and thermal (thermal stability) properties of f-MWCNTs-rGO/PMMA hybrid nanocomposites (FHC). The increased mechanical properties are due to the efficient load transfer from PMMA matrix to f-MWCNTs and rGO through better chemical interaction. The strong interaction between PMMA and f-MWCNTs-rGO in FHC is the main cause for improved thermal stability. POLYM. ENG. SCI., 59:1075-1083, 2019. (c) 2019 Society of Plastics Engineer
All inorganic solution processed three terminal charge trapping memory device
No full textWe demonstrate charge trapping memory devices comprising aluminum oxide phosphate (ALPO) blocking/indium gallium zinc oxide charge-trapping/ALPO tunneling layers with a bottom-gated architecture fabricated by sol-gel process technique at temperatures as low as 300 degrees C. The memory device offers a large memory hysteresis of 13.5 V in the I-d-V-g curve when the gate voltage is swept from -20 to +30 V and back. The true program-erase (P/E) window of 7 V is established for the P/E square pulse of +/- 20 V s(-1). Good retention characteristic is confirmed within the experimental limit of 10(4) s. The P/E mechanism is illustrated by the complete band structure of the memory devices. We also demonstrate a control device without a charge trapping layer, which shows excellent thin film transistor characteristics. Published under license by AIP Publishing
Recent Advances in the Chemistry of Doubly Activated Cyclopropanes: Synthesis and Reactivity
No full textDiactivated cyclopropanes containing two geminal electron withdrawing groups, commonly called as `Doubly Activated Cyclopropanes' are useful synthons for the synthesis of many interesting natural products and functionalized molecules. These geminal electron withdrawing groups (EWG's) facilitate the regioselective ring opening of cyclopropanes by polarizing the C-C bond adjacent to it. This polarization also allows them to undergo 1,3 dipolar cycloaddition reactions when substituted with a suitable electron donor substituent at the adjacent carbon (donor-acceptor cyclopropanes) in the presence of suitable dipolarophiles. In this review, we discuss the recent advances in the chemistry of doubly activated cyclopropanes: their synthesis, reactions and applications in total synthesis
NUMERICAL AND EXPERIMENTAL STUDIES ON THE DEVELOPMENT OF VARIABLE DENSITY NANOCOMPOSITES FOR STRUCTURAL APPLICATIONS
No full textNumerical and experimental studies performed to develop nanocomposites with varying carbon nanotube (CNT) alignment density within an epoxy matrix are presented. A 3-D numerical model has been developed that looks at the behavior of CNTs in epoxy resin subjected to non-uniform electric fields by explicitly accounting for electric field coupled with fluid flow and particle motion considering the transient resin viscosity. The transient nature of resin viscosity has been incorporated into the simulation study with data related to resin viscosity variation with time and temperature generated experimentally. The response of CNTs due to the induced dielectrophoretic force was studied using the numerical model. The model facilitated the design of an optimal electrode configuration for the processing of variable density composites. A computer controlled Arduino UNO based circuitry was developed to control supply of voltage to the electrodes during sample fabrication. The circuit was then integrated with AC voltage supply units and the electrode set-up for fabricating the variable density composite samples. Low weight fractions of CNTs (0.05 wt.% and 0.1 wt.%) in epoxy resin were used for the experimental work and preliminary experimental studies were conducted. Electrical characterization results of the variable density nanocomposites indicate over 100% and 30% increase in electrical resistance measured across sample widths in 0.05 wt.% and 0,1 wt.% CNT samples, respectively. The measured sample resistance values confirmed that variation in CNT alignment density was achieved across the samples
Crystal structures of disordered Z-type helices
No full textThe X-ray crystal structures of a decamer sequence d(CGCGTACGCG)(2) and a tetradecamer sequence d(CGCGCGTACGCGCG)(2) are presented here. Both sequences are alternating pyrimidine-purine repeat sequences and they form disordered, pseudo-continuous left handed Z-type helices. They demonstrate interesting variants of the bundles of columns of helices' mode of packing
Search for dark matter in events with a leptoquark and missing transverse momentum in proton-proton collisions at 13 TeV
No full textA search is presented for dark matter in proton-proton collisions at a center-of-mass energy of root s= 13 TeV using events with at least one high transverse momentum (p(T)) muon, at least one high-p(T) jet, and large missing transverse momentum. The data were collected with the CMS detector at the CERN LHC in 2016 and 2017, and correspond to an integrated luminosity of 77.4 fb(-1). In the examined scenario, a pair of scalar leptoquarks is assumed to be produced. One leptoquark decays to a muon and a jet while the other decays to dark matter and low-p(T) standard model particles. The signature for signal events would be significant missing transverse momentum from the dark matter in conjunction with a peak at the leptoquark mass in the invariant mass distribution of the highest p(T) muon and jet. The data are observed to be consistent with the background predicted by the standard model. For the first benchmark scenario considered, dark matter masses up to 500 GeV are excluded for leptoquark masses m(LQ) approximate to 1400 GeV, and up to 300 GeV for m(LQ) approximate to 1500 GeV. For the second benchmark scenario, dark matter masses up to 600 GeV are excluded for m(LQ) approximate to 1400 GeV
Noncovalent Catalysis for Enantioselective Direct Aldol Reaction of 3-Acetylcoumarins to Pyrazole-4,5-diones
No full textThe first catalytic enantioselective direct aldol reaction of 3-acetylcoumarins to pyrazole-4,5-diones is reported and shown to proceed through noncovalent substrate activation by a quinine-derived bifunctional tertiary amino-amide as the catalyst. The densely functionalized products, consisting of an oxygen-containing quaternary stereocenter and bearing two biologically relevant heterocycles, are generally obtained in high yields with moderate to excellent enantioselectivities
ON TWO EXTREMUM PROBLEMS RELATED TO THE NORM OF A BOUNDED LINEAR OPERATOR
No full textWe explore the norm attainment set and the minimum norm attainment set of a bounded linear operator between Hilbert spaces and Banach spaces. Indeed, we obtain a complete characterization of both the sets, separately for operators between Hilbert spaces and Banach spaces. We also study the interconnection between these two sets and prove that for operators between Hilbert spaces, these two sets are either equal or mutually orthogonal, provided both of them are non-empty. We also obtain separate complete characterizations of reflexive Banach spaces and Euclidean spaces in terms of the norm (minimum norm) attainment set, in order to illustrate the importance of our study
Small Cell Lung Cancer Therapeutic Responses Through Fractal Measurements: From Radiology to Mitochondrial Biology
No full textSmall cell lung cancer (SCLC) is an aggressive neuroendocrine disease with an overall 5 year survival rate of similar to 7%. Although patients tend to respond initially to therapy, therapy-resistant disease inevitably emerges. Unfortunately, there are no validated biomarkers for early-stage SCLC to aid in early detection. Here, we used readouts of lesion image characteristics and cancer morphology that were based on fractal geometry, namely fractal dimension (FD) and lacunarity (LC), as novel biomarkers for SCLC. Scanned tumors of patients before treatment had a high FD and a low LC compared to post treatment, and this effect was reversed after treatment, suggesting that these measurements reflect the initial conditions of the tumor, its growth rate, and the condition of the lung. Fractal analysis of mitochondrial morphology showed that cisplatin-treated cells showed a discernibly decreased LC and an increased FD, as compared with control. However, treatment with mdivi-1, the small molecule that attenuates mitochondrial division, was associated with an increase in FD as compared with control. These data correlated well with the altered metabolic functions of the mitochondria in the diseased state, suggesting that morphological changes in the mitochondria predicate the tumor's future ability for mitogenesis and motogenesis, which was also observed on the CT scan images. Taken together, FD and LC present ideal tools to differentiate normal tissue from malignant SCLC tissue as a potential diagnostic biomarker for SCLC
Signature of La Nina in interannual variations of the East India Coastal Current during spring
No full textWe have investigated interannual variations of the spring (February-April average) East India Coastal Current (EICC) magnitude between 2000 and 2018 using OSCAR (Ocean Surface Current Analysis Real-time) current and a linear, continuously stratified (LCS) model. Interannual variability of the EICC shows significant decrease in magnitude during spring of 2000, 2008 and 2011, the years when high negative ONI (Oceanic Nino Index for sea surface temperature) value has been observed due to dominance of strong La Nina events. Our LCS model also successfully simulates these interannual variability of the spring average EICC between 2000 and 2018. We carried out numerical experiments using LCS model related to local and remote forcing response on EICC. Dynamics of the EICC during spring are dominated by four different forcing processes; local wind along east coast of India, remote forcing response from the eastern and northern boundary of the BoB including islands, interior BoB and the Equatorial Indian Ocean (EIO). During El Nino and normal spring years, strong poleward interannual EICC are due to very weak negligible (order of 0-5 cm s-1) EICC from EIO remote response and in-phase poleward EICC formation using other three forcings. However, during La Nina spring years, weak (order of 0-10 cm s-1) poleward interannual EICC are formed due to destructive interference between equatorward current (order of 10-25 cm s-1) from EIO forcing and in-phase poleward current from other three forcings. We have also found propagation of interannual upwelling (downwelling) favorable Kelvin wave from EIO via eastern and western boundary of the BoB during spring in the El Nino (La Nina) years. The interannual variations in the propagation of EIO Kelvin wave are associated with the changes in the EIO zonal wind direction by climate mode like ENSO (El Nino-Southern Oscillation)