| 1. |
- Amanullah, Rahman, et al.
(författare)
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THE PECULIAR EXTINCTION LAW OF SN 2014J MEASURED WITH THE HUBBLE SPACE TELESCOPE
- 2014
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Ingår i: Astrophysical Journal Letters. - 2041-8205 .- 2041-8213. ; 788:2, s. L21-
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Tidskriftsartikel (refereegranskat)abstract
- The wavelength dependence of the extinction of Type Ia SN 2014J in the nearby galaxy M82 has been measured using UV to near-IR photometry obtained with the Hubble Space Telescope, the Nordic Optical Telescope, and the Mount Abu Infrared Telescope. This is the first time that the reddening of an SN Ia is characterized over the full wavelength range of 0.2-2 mu m. A total-to-selective extinction, R-V >= 3.1, is ruled out with high significance. The best fit at maximum using a Galactic type extinction law yields R-V = 1.4 +/- 0.1. The observed reddening of SN 2014J is also compatible with a power-law extinction, A(lambda)/A(V) = (lambda/lambda(V))(p) as expected from multiple scattering of light, with p = -2.1 +/- 0.1. After correcting for differences in reddening, SN 2014J appears to be very similar to SN 2011 fe over the 14 broadband filter light curves used in our study.
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| 2. |
- Goobar, Ariel, et al.
(författare)
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THE RISE OF SN 2014J IN THE NEARBY GALAXY M82
- 2014
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Ingår i: Astrophysical Journal Letters. - 2041-8205 .- 2041-8213. ; 784:1
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Tidskriftsartikel (refereegranskat)abstract
- We report on the discovery of SN 2014J in the nearby galaxy M82. Given its proximity, it offers the best opportunity to date to study a thermonuclear supernova (SN) over a wide range of the electromagnetic spectrum. Optical, near-IR, and mid-IR observations on the rising light curve, orchestrated by the intermediate Palomar Transient Factory, show that SN 2014J is a spectroscopically normal Type Ia supernova (SN Ia), albeit exhibiting high-velocity features in its spectrum and heavily reddened by dust in the host galaxy. Our earliest detections start just hours after the fitted time of explosion. We use high-resolution optical spectroscopy to analyze the dense intervening material and do not detect any evolution in the resolved absorption features during the light curve rise. Similar to other highly reddened SNe Ia, a low value of total-to-selective extinction, R-V less than or similar to 2, provides the best match to our observations. We also study pre-explosion optical and near-IR images from Hubble Space Telescope with special emphasis on the sources nearest to the SN location.
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| 3. |
- Boulo, S., et al.
(författare)
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First amyloid β1-42 certified reference material for re-calibrating commercial immunoassays
- 2020
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Ingår i: Alzheimer's and Dementia. - : Wiley. - 1552-5260 .- 1552-5279. ; 16:11, s. 1493-1503
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Reference materials based on human cerebrospinal fluid were certified for the mass concentration of amyloid beta (Aβ)1-42 (Aβ42). They are intended to be used to calibrate diagnostic assays for Aβ42. Methods: The three certified reference materials (CRMs), ERM-DA480/IFCC, ERM-DA481/IFCC and ERM-DA482/IFCC, were prepared at three concentration levels and characterized using isotope dilution mass spectrometry methods. Roche, EUROIMMUN, and Fujirebio used the three CRMs to re-calibrate their immunoassays. Results: The certified Aβ42 mass concentrations in ERM-DA480/IFCC, ERM-DA481/IFCC, and ERM-DA482/IFCC are 0.45, 0.72, and 1.22 μg/L, respectively, with expanded uncertainties (k = 2) of 0.07, 0.11, and 0.18 μg/L, respectively. Before re-calibration, a good correlation (Pearson's r > 0.97), yet large biases, were observed between results from different commercial assays. After re-calibration the between-assay bias was reduced to < 5%. Discussion: The Aβ42 CRMs can ensure the equivalence of results between methods and across platforms for the measurement of Aβ42. © 2020 the Alzheimer's Association
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| 4. |
- Marion, G. H., et al.
(författare)
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Early Observations and Analysis of the Type Ia SN 2014J in M82
- 2015
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 798:1, s. 39-
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Tidskriftsartikel (refereegranskat)abstract
- We present optical and near infrared (NIR) observations of the nearby Type Ia SN 2014J. Seventeen optical and 23 NIR spectra were obtained from 10 days before (–10d) to 10 days after (+10d) the time of maximum B-band brightness. The relative strengths of absorption features and their patterns of development can be compared at one day intervals throughout most of this period. Carbon is not detected in the optical spectra, but we identify C I λ1.0693 in the NIR spectra. Mg II lines with high oscillator strengths have higher initial velocities than other Mg II lines. We show that the velocity differences can be explained by differences in optical depths due to oscillator strengths. The spectra of SN 2014J show that it is a normal SN Ia, but many parameters are near the boundaries between normal and high-velocity subclasses. The velocities for O I, Mg II, Si II, S II, Ca II, and Fe II suggest that SN 2014J has a layered structure with little or no mixing. That result is consistent with the delayed detonation explosion models. We also report photometric observations, obtained from –10d to +29d, in the UBVRIJH and Ksbands. The template fitting package SNooPy is used to interpret the light curves and to derive photometric parameters. UsingRV = 1.46, which is consistent with previous studies, SNooPy finds that AV = 1.80 for E(B – V)host = 1.23 ± 0.06 mag. The maximum B-band brightness of –19.19 ± 0.10 mag was reached on February 1.74 UT ± 0.13 days and the supernova has a decline parameter, Δm 15, of 1.12 ± 0.02 mag.
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| 5. |
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| 6. |
- Kovács, András, et al.
(författare)
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Role of heterophase interfaces on local coercivity mechanisms in the magnetic Al0.3CoFeNi complex concentrated alloy
- 2023
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Ingår i: Acta Materialia. - : Elsevier BV. - 1359-6454. ; 246
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Tidskriftsartikel (refereegranskat)abstract
- Microstructural features across different length scales have a profound influence on the coercivity of magnetic alloys. Whereas the role of homophase boundaries on the pinning of magnetic domain walls is well established, the influence of heterophase interfaces on domain wall motion is complex and poorly understood. Here, we use state-of-the-art electron microscopy techniques to show that the magnetization reversal process in an Al0.3CoFeNi magnetic complex concentrated alloy (CCA), which is responsible for its coercivity, changes dramatically from a nucleation-type mechanism in the FCC+L12 state of the CCA, with a domain wall width of 171 nm, to a pinning type mechanism in the microstructure with colonies of FCC/L12 nanorods embedded in a BCC/B2 matrix, with a domain wall width of 35 nm. Our work reveals that heterophase FCC/BCC interfaces have a much stronger effect on coercivity than isostructural chemically ordered/disordered interfaces and provides a powerful guide to the rational design of microstructure to tune magnetic properties in both complex concentrated alloys and conventional magnetic alloys.
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| 7. |
- Ray, A. K., et al.
(författare)
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Mechanical property and characterization of a NiCoCrAlY type metallic bond coat used in turbine blade
- 2009
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Ingår i: Materials Science and Engineering A. - : Elsevier BV. - 0921-5093. ; 505:1-2, s. 96-104
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Tidskriftsartikel (refereegranskat)abstract
- This paper highlights some of the results obtained while studying Ni20Co18Cr12.5Al0.6Y (NiCoCrAlY) type metallic bond-coat properties of a thermal-barrier coated (TBC), AE-437A Ni base superalloy mostly employed for manufacturing compressor and stationary stator blades in aero turbines. Experiments were mainly focused in the area of evaluation of microstructure, residual stress, shear strength, hardness and with special emphasis in establishing the ductile to brittle transition temperature (DBTT) of the bond coat by using acoustic emission technique during room temperature and high temperature tensile tests. Results reveal that the residual stress was tensile in nature in the TBC layer and compressive in the bond coat as well as in the substrate. The DBTT of this bond coat is around 650 °C, which is in close proximity to the value reported in literature for CoCrAlY type of bond coat. Finite element technique was used to analyze the equivalent stresses in the bond coat, the result of which revealed the highest order of equivalent stress 800 °C, as the bond coat is ductile above 650 °C. Shear strength of the bond coat is in close proximity with that of the bond strength reported in literature for CoCrAlY and Ni22Co17Cr12.5Al0.6Y types of bond coat. © 2009 Elsevier B.V. All rights reserved.
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| 8. |
- Reddy, S. S., et al.
(författare)
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Evaluation of microstructural and dry sliding wear characteristics of pulsed Nd:YAG laser surface melted Al-Si alloys
- 2004
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Ingår i: Proceedings of the International Conference on Advances in Surface Treatment: Research and Applications, ASTRA. ; , s. 568-574
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Konferensbidrag (refereegranskat)abstract
- Aluminium-Silicon alloys are being increasingly considered for manufacture of wear prone components in automobile and aircraft industries owing to their light weight, superior corrosion resistance and high thermal conductivity, besides their amenability to processing methods such as casting. However, poor tribological characteristics have hampered industrial adoption of the above class of alloys. In principle, the tribological properties of these alloys can be improved by refining the microstructure by laser remelting techniques. Recently, Nd:YAG lasers have been used for processing of reflective materials such as Aluminium, as these lasers have better absorptivity compared to the CO2 lasers. The present study investigates the microstructural characteristics and improvements in sliding wear resistance that can result from surface melting of Al-Si alloys using a 400 W pursed Nd:YAG laser. Three different Al-Si alloys with varying Si content 5%, 12.5% and 20% have been investigated in the present study. The microstructures of the transverse cross sections of the treated samples were examined in detail and X-ray diffraction (XRD) studies carried out to ascertain changes in phase constitution. The surface melting and subsequent rapid solidification was found to cause considerable refinement of the microstructure, which in turn increased the hardness in the treated layer compared with that of bulk. The effect of laser beam scan speed on microhardness of the treated samples was evaluated. Dry sliding wear tests were conducted on treated and untreated samples of Al-12Si using a pin-on disc tribometer. The volume wear rates determined in case of the treated and untreated samples are discussed in the paper. The results have also been correlated with the morphological and microstructural characteristics noted in the laser treated specimens. Copyright © 2004 by Society for Advancement of Heat Treatment & Surface Engineering (SAHTSE).
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| 9. |
- Venkataraman, Nagaiyanallur V., et al.
(författare)
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Spatial tuning of the metal work function by means of alkanethiol and fluorinated alkanethiol gradients
- 2009
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 113:14, s. 5620-5628
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Tidskriftsartikel (refereegranskat)abstract
- Surface-chemical gradients composed of self-assembled monolayers (SAM) of deeanethiol (DT) and a partially fluorinated decanethiol (PFDT) on gold, exhibiting gradual changes in surface concentration of one or both components, have been prepared by a simple, controlled-immersion process. Infrared spectroscopic studies on a single-component PFDT gradient indicate a change in average molecular orientation with increasing surface coverage, whereas on a two-component gradient, the orientation remains invariant over the entire length of the gradient. X-ray photoelectron spectroscopic measurements on a single-component PFDT gradient show a systematic decrease in the fluorine (F Is) binding energy with increasing surface coverage, whereas a single-component DT gradient shows an increase in the carbon (C Is) binding energy. In two-component (DT-PFDT) gradients, the molar ratios of the two components at any particular location on the sample surface determine the magnitude of the binding-energy shifts at that location. Such shifts, which are on the order of 1 eV, are shown to be a consequence of work-function changes in the underlying gold upon SAM formation. These results are discussed in light of the surface-potential measurements on a DT-PFDT gradient by Kelvin Probe Force Microscopy and XP spectra acquired on "floating" and grounded samples.
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| 10. |
- Venkatesh, Lakshmi Narayanan, et al.
(författare)
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Room temperature and 600 °C erosion behaviour of various chromium carbide composite coatings
- 2019
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 422-423, s. 44-53
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the erosion behaviour of laser clad chromium carbide-Ni rich alloy composite coatings with a wide range of carbide contents at room temperature and 600 °C were investigated. The variation in carbide content of the coatings was due to dilution from the substrate and the high cooling rate in the laser cladding process preventing re-solidification of the molten carbides. Erosion rate was observed to be a function of carbide content alone and was significantly higher at 600 °C as compared to room temperature. Erosion wear ratio (E90/E30) was also dependent on carbide content but decreased at higher temperature and higher carbide contents. A comparison of erosion behaviour with detonation and plasma sprayed counterparts showed the superior performance of laser clad coatings at 600 °C. The poor erosion performance of the detonation and plasma sprayed coatings was due to weak splat bonding. Thick oxide layer formed on the steel substrate after pre-oxidation resulted in its poor erosion performance.
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