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Experimental investigation of heat transfer over double disk spike-blunt body at Mach 5.7
No full textThe forefront research in the territory to the regime of hypersonic flow is intended to focus on improving the overall performance of the existing aerospace vehicle. Two major hindrances for the development of an effective high speed vehicle are aerodynamic drag acts against the vehicle and heat transfer rate on the body. In this study, we explore the possibility of addressing this issue by placing an aerospike at the nose portion (Le., stagnation region) of the high speed vehicle and as a result, wave drag of vehicle is considerably reduced. However, this will lead to the increase in heat transfer at the localized spot of the main body. In an attempt to reduce this localized high heat transfer, the current study evaluates the variation in the heat transfer on the body, by modifying the spike through the addition of a smaller hemisphere on the mid-section of the aerodisk spike. In this regard, shock tunnel experiments and computational studies were carried out on this modified spike configuration, termed as ``double-disk spike'' or ``double spike''. The experimental results indicate that heat transfer near the localized spot of the blunt body with spike decreases for a double spike case in comparison to single disk spike. The decrease in heat transfer varies from 5% to 30% depending on the double spike configuration (i.e. varying cap radius and length of the spike). To supplement these results, 3D Finite Volume simulation, ``HiFUN'' (High Resolution Flow Solver on Unstructured), showed a good trend in heat transfer compared to that obtained from the experiment; it was found that simulated drag from the double spike is less than single spike case
An efficient and cost-effective method for purification of small sized DNAs and RNAs from human urine
No full textUrine holds great promise as a non-invasive sampling method for molecular diagnostics. The cell-free nucleic acids of urine however are small, labile, and difficult to purify. Here an efficient method for the purification of these nucleic acids is presented. An empirically derived protocol was devised by first identifying conditions that allowed recovery of a 100 base pair (bp) DNA, followed by optimization using a quantitative polymerase chain reaction (qPCR) assay. The resulting method efficiently purifies both small sized DNAs and RNAs from urine, which when combined with quantitative reverse transcription PCR (qRTPCR), demonstrably improves detection sensitivity. Fractionation experiments reveal that nucleic acids in urine exist both in the cell-free and cellular fraction, roughly in equal proportion. Consistent with previous studies, amplicons > 180bp show a marked loss in PCR sensitivity for cell-free nucleic acids. Finally, the lysis buffer developed here also doubles as an effective preservative, protecting against nucleic acid degradation for at least two weeks under simulated field conditions. With this method, volumes of up to 25ml of whole urine can be purified in a high-throughput and cost-effective manner. Coupled with its ability to purify both DNA and RNA, the described method may have broad applicability for improving the diagnostic utility of urine, particularly for the detection of low abundant targets
Development of sesbania mosaic virus nanoparticles for imaging
No full textThe capsids of viruses have a high degree of symmetry. Therefore, virus nanoparticles (VNPs) can be programmed to display many imaging agents precisely. Plant VNPs are biocompatible, biodegradable and non-infectious to mammals. We have carried out bioconjugation of sesbania mosaic virus (SeMV), a well characterized plant virus, with fluorophores using reactive lysine-N-hydroxysuccinimide ester and cysteine-maleimide chemistries. Monitoring of cellular internalization of labelled SeMV nanoparticles (NPs) by confocal microscopy and flow cytometry showed that the particles have a natural preference for entry into MDA-MB-231 (breast cancer) cells, although they could also enter various other cell lines. The fluorescence of SeMV NPs labelled via the cysteines with Cy5.5 dye was found to be more stable and was detectable with greater sensitivity than that of particles labelled via the lysines with Alexa Fluor. Live-cell imaging using SeMV internally labelled with Cy5.5 showed that it could bind to MDA-MB-231 cells in less than 5 minutes and enter the cells within 15 minutes. The particles undergo endolysosomal degradation by 6 h as evidenced by their co-localization with LAMP-1. Far-western blot analysis with a HeLa cell membrane protein fraction showed that SeMV interacts with 54-, 35- and 33-kDa proteins, which were identified by mass spectrometry as vimentin, voltage-dependent anion-selective channel protein (VDAC1), and annexin A2 isoform 2 (ANXA2), respectively, suggesting that the particles may bind and enter the cell through these proteins. The results presented here demonstrate that the SeMV NPs provide a new platform technology that could be used to develop in vivo imaging and targeted drug delivery agents for cancer diagnosis and therapy
Microstructure, morphology and electrochemical properties of ZnFe-Graphene composite coatings
No full textZinc-Iron (Zn-Fe) and Zn-Fe-Graphene (Zn-Fe-G) coatings were electrodeposited on mild steel from acidic sulphate electroplating bath. Electrochemically exfoliated graphene was dispersed in Zn-Fe plating bath to produce Zn-Fe-Graphene composite coatings containing different amount of graphene. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques were used to characterize the coatings. Addition of graphene refined the grain size and altered the morphology of the Zn-Fe-G coatings. Influence of change in morphology and microstructure on the electrochemical corrosion behavior of the coatings was studied by Tafel polarization and electrochemical impedance spectroscopic (EIS) methods. Incorporation of graphene into the Zn-Fe matrix enhanced the corrosion resistance of the coatings up to a certain concertation of graphene. Further addition of graphene, enhanced the corrosion rate indicating an ``optimum'' with respect to the addition of graphene into the composite coatings for enhancement in the corrosion resistance performance. (C) 2018 Elsevier B.V. All rights reserved
Bulk and few-layer MnPS3: a new candidate for field effect transistors and UV photodetectors
No full textLayered metal thiophosphates with the general formula MPX3 (M is a group VI element and X is a chalcogen) have been emerging as a novel group of tunable bandgap semiconductors. Herein, we report the synthesis of high quality MnPS3 crystals, and their mechanical exfoliation onto pre-fabricated devices. The use of atomic force microscopy and Raman spectroscopy yielded information on the number of layers. MnPS3-based field effect transistors (FETs) comprising few-layer and bulk crystals with gold contacts show p-type conductivity with an on-off ratio of approximate to 10(3). Temperature dependent electrical transport measurements yield a Schottky barrier height value of 0.34 eV for few-layer devices. FETs based on multilayer and bulk MnPS3 show very similar transport characteristics. The transistor devices have also been shown to be good ultraviolet photodetectors with photoresponsivity of 288 A W-1 at a wavelength of 365 nm. Density functional theory calculations reveal the parameters that affect the viability of electron/hole doping in MnPS3 and help understand the p-type nature of the FET device
Search for low-mass resonances decaying into bottom quark-antiquark pairs in proton-proton collisions at root s=13 TeV
No full textA search for narrow, low-mass, scalar, and pseudoscalar resonances decaying to bottom quark-antiquark pairs is presented. The search is based on events recorded in root s = 13 TeV proton-proton collisions with the CMS detector at the LHC, collected in 2016, and corresponding to an integrated luminosity of 35.9 fb(-1). The search selects events in which the resonance would be produced with high transverse momentum because of the presence of initial- or final-state radiation. In such events, the decay products of the resonance would be reconstructed as a single large-radius jet with high mass and two-prong substructure. A potential signal would be identified as a narrow excess in the jet invariant mass spectrum. No evidence for such a resonance is observed within the mass range from 50 to 350 GeV, and upper limits at 95% confidence level are set on the product of the cross section and branching fraction to a bottom quark-antiquark pair. These constitute the first constraints from the LHC on exotic bottom quark-antiquark resonances with masses below 325 GeV
Stable Hall voltages in presence of dynamic quasi-continuum bands in poly (3,4-ethylene-dioxythiophene)
No full textTopological and thermal disorder complicate the mobility characterization in poly(3,4-ethylenedioxythiophene) systems and presently leaves the exact transport mechanisms not fully understood. Here we show that ac-Hall measured by lock-in amplifier is able to resolve the Hall voltage in semimetallic polymers between room temperature and 32 K. These results are evaluated using an organic random phase model. This accounts for the role of tail states and, particularly, for thermal disorder of molecular semiconductors. We report band mobilities up to 3.7 cm(2) V-1 s(-1) in semimetallic polymers occurring in delocalized bands that originate from significant electron coherence across the polymer chains
Surface functionalization of 3D printed polymer scaffolds to augment stem cell response
No full textThree-dimensional (3D) printing by material extrusion is being widely explored to prepare patient-specific scaffolds from biodegradable polyesters such as poly(lactic acid) (PLA). Although they provide the desired mechanical support, PLA scaffolds lack bioactivity to promote bone regeneration. The aim of this work was to develop a surface engineering approach for enhancing the osteogenic activity of 3D printed PLA scaffolds. Macro-porous PLA scaffolds were prepared by material extrusion with 70.2% porosity. Polyethyleneimine was chemically conjugated to the alkali-treated PLA scaffolds followed by conjugation of citric acid. These polymer-grafted scaffolds were immersed in the simulated body fluid to yield scaffolds coated with calcium-deficient hydroxyapatite (PLA-HaP). Surface roughness and water wettability were enhanced after surface modification. PLA-HaP scaffolds exhibited a steady release of calcium ions in an aqueous medium for 10 days. The adhesion and proliferation of human mesenchymal stem cells (hMSCs) on PLA-HaP was similar to 50% higher than on PLA. Mineral deposition resulting from hMSC osteogenesis on PLA-HaP scaffolds was nearly twice that on PLA scaffolds. This was corroborated by the increase in alkaline phosphatase activity and expression of several osteogenic genes. Thus, this work presents a surface modification strategy to enhance the bioactivity of 3D printed scaffolds for bone tissue regeneration. (C) 2018 Elsevier Ltd
ON SOME GEOMETRIC PROPERTIES OF OPERATOR SPACES
No full textIn this article, we study some geometric properties like parallelism, orthogonality, and semirotundity in the space of bounded linear operators. We completely characterize parallelism of two compact linear operators between normed linear spaces X and Y, assuming X to be reflexive. We also characterize parallelism of two bounded linear operators between normed linear spaces X and Y. We investigate parallelism and approximate parallelism in the space of bounded linear operators defined on a Hilbert space. Using the characterization of operator parallelism, we study Birkhoff James orthogonality in the space of compact linear operators as well as bounded linear operators. Finally, we introduce the concept of semirotund points (semirotund spaces) which generalizes the notion of exposed points (strictly convex spaces). We further study semirotund operators and prove that M (X, Y) is a semirotund space which is not strictly convex if X, Y are finite-dimensional Banach spaces and Y is strictly convex
Effect of Ca2+ ion co-doping on radiative properties via tuning the local symmetry around the Eu3+ ions in orange red light emitting GdPO4:Eu3+ phosphors
No full textA series of Ca2+ substituted GdPO4:Eu3+ novel phosphors were prepared via the solid state method. Rietveld refinement of the XRD data and transmission electron microscopy results confirmed that all these compounds adopted the monazite phase with space group P21/n. Fourier transform infrared spectroscopy (FTIR) analysis confirmed the presence of the characteristic vibrational bands for host matrix of GdPO4, and field emission scanning electron microscopy (FESEM) results revealed that the particles possess agglomerated granular morphology. Photo-luminescent spectra displayed the representative luminescence D-5(0) F-7(J) (J = 0-4) intra-4f shell Eu3+ ion transitions. The magnetic dipole (D-5(0) F-7(1)) transition was stronger than the electric dipole (D-5(0) F-7(2)) transition. On co-doping Ca2+ content to Gd0.93Eu0.07PO4 phosphor, we observed the enhanced PL intensity as a function of Ca2+ content; the maximum intensity of 1.5 times was observed for 7 mol% of calcium doped Gd0.93Eu0.07PO4 phosphor. The enhancement of the PL intensity owing to the effective ionic radius and the mismatch in Pauling's electronegativity between co-dopant and host cations causes distortion of local crystal field surrounding the Eu3+ ions. Furthermore, this local distortion or reduced symmetry effect around the Eu3+ ions was reconfirmed by the Judd-Ofelt and life time decay analyses. The evaluated 1931 Commission International de l'Eclairage (CIE) chromaticity color coordinates exhibit orange red emission (x = 0.6247, y = 0.3748) with minimal CCT values and high color purity. This class of phosphors possessed excellent thermal stability at high temperature, and the integrated emission intensity at 423 K was about 66% of that at 303 K. Considering the above results, the Eu3+/Ca2+ co-doped GdPO4 phosphors have potential applications in the near-UV excited white light emitting diodes