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Mixed type I and type II superconductivity due to intrinsic electronic inhomogeneities in the type II Dirac semimetal PdTe2
No full textThe type 11 Dirac semimetal PdTe2 is unique in the family of topological parent materials because it displays a superconducting ground state below 1.7 K. Despite wide speculation on the possibility of an unconventional topological superconducting phase, tunneling and heat capacity measurements revealed that the superconducting phase of PdTe2 follows predictions of the microscopic theory of Bardeen, Cooper and Schrieffer for conventional superconductors. The superconducting phase in PdTe2 is further interesting because it also displays properties that are characteristic of type-I superconductors and are generally unexpected for binary compounds. Here, from scanning tunneling spectroscopic measurements we show that the surface of PdTe2 displays intrinsic electronic inhomogeneities in the normal state which leads to a mixed type I and type II superconducting behaviour along with a spatial distribution of critical fields in the superconducting state. Understanding of the origin of such inhomogeneities may be important for understanding the topological properties of PdTe2 in the normal state
UV to X-Ray Comptonization Delay in Mrk 493
No full textThe broadband X-ray emission from type 1 active galactic nuclei, dominated by a power-law continuum, is thought to arise from repeated inverse Compton scattering of seed optical/UV photons by energetic electrons in a hot corona. The seed optical/UV photons are assumed to arise from an accretion disk, but direct observational evidence has remained elusive. Here we report the discovery of variations in the UV emission preceding the variations in the X-ray emission based on similar to 100 ks XMM-Newton observations of the narrow-line Seyfert 1 galaxy Mrk. 493. We find that the UV emission leads by similar to 5 ks relative to the X-ray emission. The UV lead is consistent with the time taken by the UV photons to travel from the location of their origin in the accretion disk to the hot corona, and the time required for repeated inverse Compton scattering converting the UV photons into X-ray photons. Our findings provide the first direct observational evidence for the accretion disk being responsible for the seed photons for thermal Comptonization in the hot corona, and for constraining the size of the corona to similar to 20r(g)
Significance of tool offset and copper interlayer during friction stir welding of aluminum to titanium
No full textThis investigation highlights the influence of tool offset on the microstructural evolution, phase formation, and hardness distribution during friction stir welding (FSW) of commercially pure aluminum (Al) to commercially pure titanium (Ti) with a copper (Cu) interlayer (200-m thick). It was observed that tool offset position controls the mechanical mixing of materials in the weld nugget. The mechanical mixing also depends on the deformation, fragmentation, and distribution of each material in the weld nugget. The fragmentation of materials leads to the development of comparatively fine particles with variation in size and morphology. Insufficient mixing at higher tool offsets promotes the formation of root defects and produces inferior welds. On the other hand, when the tool offset is less than the optimum value, severe deformation and mechanical mixing lead to the formation of wormhole defects and evolution of intermetallic compounds in the weld. The spatial distribution of particles and intermetallics in the weld nugget leads to a large scatter in hardness values. Since mechanical mixing affects the morphology, phase evolution, and mechanical properties of the weld, tool offset is considered to be a very important parameter to be optimized for monitoring mechanical mixing and further development of the dissimilar weld with interlayer material
Waste Foundry Sand/Bauxite Residue for Enhanced NOx Reduction in Diesel Exhaust Pretreated With Plasma/O-3 Injection
No full textThe increased usage of diesel fuel of late has led the researchers to pay more attention toward abatement of increased emission of oxides of nitrogen (NOx) in the engine exhaust. The focus is, therefore, lies in providing a technique that is economical, feasible, and long lasting. The combination of electric discharge plasma with adsorbent/catalyst derived out of solid waste can be one such possible technique. In this paper, waste foundry sand from foundry industry and red mud or bauxite residue from aluminum industry have been used. Diesel engine exhaust under dry condition was exposed to an oxidizing discharge plasma environment. The plasma-treated exhaust was subjected to either adsorption over waste foundry sand or catalysis over red mud. Studies were carried out in the laboratory environment with 20% loading of diesel generator. The oxidizing plasma environment was either with direct plasma or with indirect plasma in which case ozone injection into the exhaust was accomplished. The ozone-adsorbent cascading system has resulted in about 87% NOx reduction in the dry exhaust case. The effect of O-3:NO ratio was discussed from the point of NO/NO2
Part I: Physical Insight Into Carbon-Doping-Induced Delayed Avalanche Action in GaN Buffer in AlGaN/GaN HEMTs
No full textPhysics behind the improvement in breakdown voltage of AlGaN/GaN HEMTs with carbon-doping of GaN buffer is discussed. Modeling of carbon as acceptor traps and self-compensating acceptor/donor traps is discussed with respect to their impact on avalanche breakdown. Impact of carbon behaving as a donor as well as acceptor traps on electric field relaxation and avalanche generation is discussed in detail to establish the true nature of carbon in GaN that delays the avalanche action. This understanding of the behavior of carbon-doping in GaN buffer is then utilized to discuss design parameters related to carbon doped buffer. Design parameters such as undoped channel thickness and relative trap concentration induced by carbon-doping are discussed with respect to the performance metrics of breakdown voltage, leakagecurrent, sheet charge density, and dynamic ON-resistance
Highly sensitive fiber Bragg grating-based pressure sensor using side-hole packaging
No full textIn this work, an analysis of pressure response of a fiber Bragg grating (FBG) sensor in a side-hole package is presented using the finite element method. Various parameters of the side-hole packaging such as hole radius, the distance of separation between them, the radius and length of the package, and the choice of the package material are considered and optimized in order to promote maximum pressure sensitivity of the FBG sensor. This investigation on optimization of the side-hole package parameters gives rise to pressure sensitivity of nearly 10(5) times as compared with the bare FBG sensor, with the numerical values of 3 pm/MPa for a bare FBG sensor to similar to 280,000 pm/MPa for an optimized side-hole package FBG sensor. Such high-pressure sensitivity of an FBG sensor is being reported for the very first time in this work, to the best of our knowledge, and can be considered as the initial step toward the realization of a highly sensitive hydrophone based on FBG for sensing underwater acoustic signals. (C) 2018 Optical Society of Americ
Characterization of DNA double-strand break repair pathways in diffuse large B cell lymphoma
No full textEfficient DNA repair is indispensable for maintaining genomic integrity in humans. Cancer associated deletions and mutations are mainly due to misrepaired DNA double-strand breaks (DSBs). Classical nonhomologous end joining (c-NHEJ) and homologous recombination (HR) are two major DSB repair pathways in humans. An error prone, alternative NHEJ pathway that utilizes microhomology was also reported in cancer cells and to a lesser extent in normal cells. In the present study, we evaluated the efficiency of various DSB repair pathways in the most common lymphoma, the diffuse large B cell lymphoma (DLBCL). Here we show that DNA repair through c-NHEJ pathway is limited in SUDHL8, a cell line derived from a DLBCL patient. Unlike c-NHEJ, microhomology mediated end joining (MMEJ) was predominant at physiological temperature. Consistent with the observation, expression level of repair proteins such as LIGASE I, LIGASE III, PARP1, CtIP, and MRE11 was higher in DLBCL cells when compared to c-NHEJ proteins. Further, inhibition of LIGASE I or MRE11, led to reduction in the efficiency of MMEJ in DLBCL cells. Besides, HR-mediated DSB repair occurring through gene conversion was observed. Thus, our results reveal the predominance of MMEJ over c-NHEJ in repairing DSBs in DLBCL cells, while error-free repair through HR was also evident
A Holistic Approach to the Design of Hearing Aids for Children with Hearing Impairment in Resource Constrained Settings
No full textSpeech and language rehabilitation of hearing
impaired children is an economically and socially challenging
situation in resource constrained settings. The economic
challenge is due to the high costs of hearing aid and social
challenge is due to lack of adequate therapy personnel to
provide a framework in the community after starting therapy in
the hospital.
The paper describes an innovative smartphone-based
application integrated with an affordable hearing aid to provide
a community-based framework for parents to provide therapy
at home and update the therapist about ongoing progress.
Based on clinical immersion, stakeholder analysis and
habitat observation, acoustic requirements, ingredients for
scoring the progress of therapy and minimum technical
specifications of the application were derived.
The application was designed to integrate with a prototype
hearing aid. It has a hearing aid mode and therapy mode. The
hearing aid mode provides high quality amplification. The
therapy mode assists the parent to train the child in the first two
components of speech therapy, namely auditory localization and
discrimination. There is an in-built option to monitor progress
of therapy. One section was devoted to providing motivation to
parents by showcasing success stories of hearing impaired
children
Expert opinion rated the application high on novelty,
relevance and utility in resource limited settings of Indian
context. Experts recommended improving richness of content
and making all stimuli culturally appropriate.
Field trails of the application will examine its effectiveness in
providing a community-based framework for speech and
language rehabilitation and reducing drop outs form therapy
Quantitative vapour concentration measurements in n-dodecane and n-hexadecane sprays
No full textQuantitative vapour concentration measurements in evaporating sprays of n-dodecane and n-hexadecane at high pressure and temperature are presented in this paper. These two liquids have been selected as they represent realistic fuels such as diesel and biodiesel, and exhibit significantly different boiling points. The objective of this study is to understand the effect of boiling point on vapour distribution in evaporating sprays. The experiments are performed in a high pressure spray chamber with optical access filled with nitrogen and heated to reach a pressure of 50-bar and temperature of 900 K. Two injection pressures of 1000 and 1500-bar are considered. Planar laser induced fluorescence (PLIF) of an exciplex tracer system consisting of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) and a-methyl naphthalene has been used for vapour concentration measurements. A calibration point relating the TMPD concentration and PLIF signal is obtained by using a fuel vapour jet at a known temperature. Various corrections to the PLIF signal are performed. The vapour mixture fraction (or vapour mass fraction) obtained from the experimental data is compared for the two liquids. It is observed that the mixture fractions for both liquids are very close to each other. An analytical model is used to explain this trend by estimating the variation of mixture fraction along centerline for the two liquids. The model shows the predominance of the density ratio, which is similar for both liquids leading to similarity in the experimental data of mixture fraction. Also, the measurements provide a comprehensive dataset for assessment of CFD simulations of single component evaporating sprays in terms of predicting vapour-air mixing
