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Magnetic Characterization of Ferromagnetic Alloys for High Speed Electric Machines
No full textHigh speed electric machines operate at tens of thousands of revolutions per minute. The rotor and stator cores experience high frequency electromagnetic fields. While the magnetic characteristics are available at 50/60 Hz, magnetic characteristics are required over a wide range of frequency due to variable speed operation of high speed motor. In this paper tests are carried out on ferromagnetic alloys over a frequency range of 1 Hz to 5 kHz and flux densities ranging from 0.1 T to 2 T. The materials considered include the widely used M36 and 65C600 laminations. In applications where the rotor speed and shaft temperature are high, solid core rotors are more viable than laminated ones. Further, the application requires that the shaft and active magnetic parts of the rotor be made of a single material. Hence, EN353 and EN8 are the prospective rotor materials considered. An extensive experimental study on the magnetic characteristics of these materials over a wide frequency range is reported in this paper. The results include B-H curves, static magnetisation curves and power loss curves. The loss curves are useful to evaluate the loss density in the magnetic material at different frequencies and 14 various values of peak flux densities. These experimental data are essential for the analysis, design and performance evaluation of high speed electric machines
Contrasting Effects of Guanidinium Chloride and Urea on the Activity and Unfolding of Lysozyme
No full textCosolvents play an important role in regulating the stability and function of proteins present in the cell. We studied the role of cosolvents, urea and guanidinium chloride (GdmCl), which act as protein denaturants, in the catalytic activity and structural stability of the protein lysozyme using activity measurements, spectroscopy, and molecular dynamics simulations. We find that the activity of lysozyme increases on the addition of urea, whereas it decreases sharply on the addition of GdmCl. At low GdmCl concentrations (GdmCl] < 4 M), the activity of lysozyme decreases, even though there is no significant perturbation in the structure of the lysozyme folded state. We find that this is due to the strong interaction of the Gdm(+) ion with the residues Asp52 and Glu35, which are present in the lysozyme catalytic site. In contrast, urea interacts with Trp63 present in the loop region present near the active site of lysozyme, inducing minor conformational changes in lysozyme, which can increase the activity of lysozyme. At higher denaturant concentrations, experiments show that GdmCl completely denatures the protein, whereas the folded state is stable in the presence of urea. We further show that GdmCl denatures lysozyme with the disulfide bonds intact in the protein, whereas urea denatures the protein only when the disulfide bonds are broken using reducing agents
Retardation of Small Creep-Fatigue Crack in Gr. 91 Steel Through the Combined Effects of Stress Relaxation, Microstructural Evolution, and Oxidation
No full textThis investigation reports an unusual effect of hold time (up to 10seconds) on retardation in the growth of creep-fatigue small cracks at 550 degrees C in Grade 91 steel. The observed phenomenon was interpreted by elucidating multiple processes that are active in the plastic zone at the crack tip. To this effect, microstructural and mechanical responses of the crack tip plastic zone were compared with the mechanical and microstructural responses during low cycle fatigue/creep-fatigue. It is proposed that the stress relaxation that occurs during the hold time can reduce the stress intensity in the plastic zone of crack tip thus, contributing to retardation in the small crack growth rate. Aside from stress relaxation, stress intensity in the crack tip can be further reduced by the phenomenon of cyclic softening that occurs because of plasticity-induced microstructural coarsening. Separately, the contribution of oxidation-induced crack tip shielding is also considered to explain the observed effects of hold time on crack growth rates. Taken together, a combination of stress relaxation, enhanced rate of cyclic softening, and higher degree of oxidation with the introduction of a hold time is demonstrated to be responsible for reduction in the crack growth under creep-fatigue conditions
Spent embryo culture medium metabolites are related to the in vitro attachment ability of blastocysts
No full textThe metabolomic profile of an embryo culture medium can aid in the advanced prediction of embryonic developmental potential and genetic integrity. But it is not known if this technology can be used to determine the in vitro potential of inner cell mass (lCM) in adherence and proliferation. Here, we investigated the developmental potential of mouse 2-cell embryos carrying cisplatin-induced DNA lesions (lDL), beyond blastocyst stage using ICM outgrowth assay. The genetic integrity of ICM cells was determined by comet assay. The metabolic signatures of spent medium were recorded 84 hours post injection of hCG (hpi- hCG), and after 96 hours of extended in vitro culture (Ex 96) by NMR spectroscopy. We observed that blastocysts that lack the ability to adhere in vitro had an increased requirement of pyruvate (p < 0.01), lactate (p < 0.01), and were accompanied by a significant reduction of pyruvatealanine ratio in the culture medium. We propose that the aforementioned metabolites from 84 hpi-hCG spent medium be further explored using appropriate experimental models, to prove their potential as biomarkers in the prediction of implantation ability of in vitro derived human embryos in clinical settings
Evaporation From Layered Porous Medium in the Presence of Infrared Heating
No full textWe report an experimental study of evaporation of two configurations of layered porous media that are heated from above by infrared (IR) radiation having -1,000 W/m(2) intensity. We used nearly monodisperse glass beads in each of the layers. The two configurations are (1) coarse and fine beads, stacked side by side and (2) fine beads over coarse beads (FoC). The IR heater mimics the natural evaporation process in soils, and the aim is to study, using three diagnostic tools, how the layering affects the evaporation process, and compare it with the homogeneous porous medium case. For each experiment we use three diagnostics simultaneously, evaporation rate measurement using a precision balance, surface temperature imaging using an IR camera, and visualization of the evaporation process with fluorescein dye. The constant (evaporation) rate period (CRP) regime, found in homogeneous porous media, is drastically changed for the two layered configurations. We show new results for side-by-side configuration. In the FoC configuration we show that the near-surface water content in the finer particles does not change in CRP and a true constant evaporation rate is possible. The average water depth at end of CRP in the porous medium, for a wide range of diameter ratios for the FoC configuration are compared with the predictions from theoretical relations proposed by Shokri et al. (2010, https://doi.org/10.1029/2009JB006743) and Assouline et al. (2014, https://doi.org/10.1002/2013WR014489). Using a simple surface energy budget, we show that knowing the surface temperature, the evaporation rate can be estimated with reasonable accuracy (+/- 5%) during drying of a porous medium. Plain Language Summary We show the movement of water from larger particle sizes to the smaller in different combinations of texturally layered systems. Temperature, measured using an infrared camera, was used as a tracer to track surface water content. In the subsurface we tracked the drying front using a unique fluorescein dye visualization technique. The dye particles are red when dry but appear green in solution with water
Pyriplatin-Boron-Dipyrromethene Conjugates for Imaging and Mitochondria-Targeted Photodynamic Therapy
No full textMonofunctional pyriplatin analogues cis-Pt(NH3)(2)(L)Cl](NO3) (1-3) having boron-dipyrromethene (BODIPY) pendants (L) with 1,3,5,7-tetramethy1-8-(4-pyridyl)-4,4'-difluoroboradiazaindacene moieties were designed and synthesized, and their photocytotoxic properties were studied. The Pt-BODIPY conjugates displayed an absorption band within 505-550 nm and a green emissive band near 535 nm in 1% DMSO/DMEM (Dulbecco's modified Eagle's medium) buffer. Complex cis-Pt(NH3)(2)(4-Me-py)Cl](NO3) (4) was used as a control for determining the structural aspects by X-ray crystallography. The mono- and diiodinated BODIPY complexes 2 and 3 showed generation of singlet oxygen on light activation as evidenced from the 1,3-diphenylisobenzofuran (DPBF) titration experiments. The cytotoxicity of the BODIPY complexes was tested against A549 (human lung cancer), MCF-7 (human breast cancer), and HaCaT (human skin keratinocyte) cells in dark and visible light (400-700 nm, 10 J cm(-2)). While complexes 2 and 3 showed excellent photocytotoxicity (IC50 approximate to 0.05 mu M), they remained essentially nontoxic in the dark (IC50 > 100 mu M). The emissive bands of 1 and 2 were used for cellular imaging by confocal microscopy study, which showed their mitochondria] localization. This was further supported by platinum estimation from isolated mitochondria and mitochondrial depolarization through a JC-1 assay. The photomediated apoptotic cell death was evidenced from flow cytometric assays, annexin-V/FITC-PI (fluorescein isothiocyanate-propidium iodide) and cell cycle arrest in sub-G1 and G2/M phases. The complexes bind to 9-ethylguanine as a model nucleobase to form monoadducts. A mechanistic study on DNA photocleavage activity using pUC19 DNA showed singlet oxygen as the reactive oxygen species (ROS). The combination of photodynamic therapy with DNA cross-linking property enhanced the anticancer potential of the monofunctional BODIPY-conjugates of pyriplatins
Transport in a thin topological insulator with potential and magnetic barriers
No full textWe study transport across either a potential or a magnetic barrier which is placed on the top surface of a three-dimensional thin topological insulator (TI). For such thin TIs, the top and bottom surfaces interact via a coupling lambda which influences the transport properties of junctions constructed out of them. We find that for junctions hosting a potential barrier, the differential conductance oscillates with the barrier strength. The period of these oscillations doubles as the coupling lambda changes from small values to a value close to the energy of the incident electrons. In contrast, for junctions with a magnetic barrier, the conductance approaches a nonzero constant as the barrier strength is increased. This feature is in contrast to the case of transport across a single TI surface where the conductance approaches zero as the strength of a magnetic barrier is increased. We also study the spin currents for these two kinds of barriers; in both cases, the spin current is found to have opposite signs on the top and bottom surfaces. Thus this system can be used to split applied charge currents to spin currents with opposite spin orientations which can be collected by applying opposite spin-polarized leads to the two surfaces. We show that several of these features of transport across finite width barriers can be understood analytically by studying the delta-function barrier limit. We discuss experiments which may test our theory
Semi-equivelar maps on the torus and the Klein bottle are Archimedean
No full textIf the face-cycles at all the vertices in a map on a surface are of same type then the map is called semi-equivelar. There are eleven types of Archimedean tilings on the plane. All the Archimedean tilings are semi-equivelar maps. If a map X on the torus is a quotient of an Archimedean tiling on the plane then the map X is semi-equivelar. We show that each semi-equivelar map on the torus or on the Klein bottle is a quotient of an Archimedean tiling on the plane. Vertex-transitive maps are semi-equivelar maps. We know that four types of semi-equivelar maps on the torus are always vertex-transitive and there are examples of other seven types of semi-equivelar maps which are not vertex-transitive. We show that the number of Aut(Y)-orbits of vertices for any semi-equivelar map Y on the torus is at most six. In fact, the number of orbits is at most three except one type of semi-equivelar maps. Our bounds on the number of orbits are sharp. (C) 2018 Elsevier B.V. All rights reserved
Challenges & Physical Insights Into the Design of Fin-Based SCRs and a Novel Fin-SCR for Efficient On-Chip ESD Protection
No full textThis paper presents the detailed physical insights into the silicon-controlled rectifier (SCR) phenomena in planar equivalent Fin SCR devices. The complexity and roadblocks for SCR triggering in FinFET technology are explored. Implication of contact silicidation on Fin SCR turn-oN is discussed in detail. Device design approaches are discussed for efficient Fin-enabled SCRs. In this direction, a novel contact engineering scheme in Fin technology is disclosed for improved SCR action. Moreover, a novel Fin SCR is presented, which offers area-efficient electrostatic discharge current carrying capability