| 1. |
- Morokuma, Tomoki, et al.
(författare)
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Kiso Supernova Survey (KISS) : Survey strategy
- 2014
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Ingår i: Nippon Tenmon Gakkai obun kenkyu hokoku. - : Oxford University Press (OUP). - 0004-6264. ; 66:6
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Tidskriftsartikel (refereegranskat)abstract
- lThe Kiso Supernova Survey (KISS) is a high-cadence optical wide-field supernova (SN) survey. The primary goal of the survey is to catch the very early light of a SN, during the shock breakout phase. Detection of SN shock breakouts combined with multi-band photometry obtained with other facilities would provide detailed physical information on the progenitor stars of SNe. The survey is performed using a 2 degrees.2 x 2 degrees.2 field-of-view instrument on the 1.05-m Kiso Schmidt telescope, the Kiso Wide Field Camera (KWFC). We take a 3-min exposure in g-band once every hour in our survey, reaching magnitude g similar to 20-21. About 100 nights of telescope time per year have been spent on the survey since 2012 April. The number of the shock breakout detections is estimated to be of the order of 1 during our three-year project. This paper summarizes the KISS project including the KWFC observing setup, the survey strategy, the data reduction system, and CBET-reported SNe discovered so far by KISS.
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| 2. |
- Tanaka, Masaomi, et al.
(författare)
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DISCOVERY OF DRAMATIC OPTICAL VARIABILITY IN SDSS J1100+4421 : A PECULIAR RADIO-LOUD NARROW-LINE SEYFERT 1 GALAXY?
- 2014
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Ingår i: Astrophysical Journal Letters. - 2041-8205 .- 2041-8213. ; 793:2, s. L26-
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Tidskriftsartikel (refereegranskat)abstract
- We present our discovery of dramatic variability in SDSS J1100+4421 by the high-cadence transient survey Kiso Supernova Survey. The source brightened in the optical by at least a factor of three within about half a day. Spectroscopic observations suggest that this object is likely a narrow-line Seyfert 1 galaxy (NLS1) at z = 0.840, however, with unusually strong narrow emission lines. The estimated black hole mass of similar to 10(7) M-circle dot implies bolometric nuclear luminosity close to the Eddington limit. SDSS J1100+4421 is also extremely radio-loud, with a radio loudness parameter of R similar or equal to 4 x 10(2)-3 x 10(3), which implies the presence of relativistic jets. Rapid and large-amplitude optical variability of the target, reminiscent of that found in a few radio- and gamma-ray-loud NLS1s, is therefore produced most likely in a blazar-like core. The 1.4 GHz radio image of the source shows an extended structure with a linear size of about 100 kpc. If SDSS J1100+4421 is a genuine NLS1, as suggested here, this radio structure would then be the largest ever discovered in this type of active galaxies.
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| 3. |
- Bevilacqua, Stella, 1981, et al.
(författare)
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HEB mixers for THz radio astronomy
- 2014
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Ingår i: Swedish Microwave Days March 11-12, 2014.
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Konferensbidrag (refereegranskat)abstract
- Hot-Electron Bolometer (HEB) mixers made of 10 nm superconducting MgB2 films are discussed for high sensitivity high spectral resolution spectrometers for radio astronomy. The key advantage of the used MgB2 films is in achievement of wider Intermediate Frequency (IF) bandwidth.
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| 4. |
- Bevilacqua, Stella, 1981, et al.
(författare)
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Low noise MgB2 terahertz hot-electron bolometer mixers
- 2012
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 100:3
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Tidskriftsartikel (refereegranskat)abstract
- We report on low noise terahertz bolometric mixers made of MgB2 superconducting thin films. For a 10-nm-thick MgB2 film, the lowest mixer noise temperature was 600 K at 600 GHz. For 30 to 10-nm-thick films, the mixer gain bandwidth is an inverse function of the film thickness, reaching 3.4 GHz for the 10-nm film. As the critical temperature of the film decreases, the gain bandwidth also decreases, indicating the importance of high quality thin films for large gain bandwidth mixers. The results indicate the prospect of achieving a mixer gain bandwidth as large as 10-8 GHz for 3 to 5-nm-thick MgB2 films.
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| 5. |
- Bevilacqua, Stella, 1981, et al.
(författare)
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MgB2 Hot Electron Bolometers for THz radio astronomy
- 2012
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Ingår i: 23rd International Symposium on Space Terahertz Technology.
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Konferensbidrag (refereegranskat)abstract
- We discuss Hot Electron Bolometer (HEB) THz mixers made of superconducting Magnesium Diboride (MgB2) films. The films of 30 nm, 15 nm and 10 nm thick were deposited on sapphire substrates. The MgB2 HEBs were patterned as a bridge at the feed point of a spiral antenna. The performance of the devices was investigated with respect to the gain bandwidth (GBW) and the noise temperature. The GBW was measured via mixing two signal sources (BWOs at 600 GHz). For the given films thicknesses, the GBW was measured to be 1.3 GHz, 2.3 GHz and 3.4 GHz, which is larger than for the NbN HEB mixers made of the same films thicknesses. Using the Y-factor technique a noise temperature of 800 K at 600 GHz local oscillator (LO) frequency was measured for mixers made of 10 nm MgB2 film. Besides the films thickness, the gain and the noise bandwidths are functions of the films critical temperature, Tc. For 10nm films, with Tc=15K, a noise bandwidth on the order of 8GHz was measured. From these measurements and from the material parameters a GBWof 8 GHz (noise bandwidth >10GHz) is expected for 3-5 nm MgB2 films.
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| 6. |
- Bevilacqua, Stella, 1981, et al.
(författare)
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Study of IF bandwidth of MgB2 phonon-cooled hot-electron bolometer mixers
- 2013
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Ingår i: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 3:4, s. 409-415
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Tidskriftsartikel (refereegranskat)abstract
- A noise bandwidth (NBW) of 6-7 GHz was obtained for Hot-Electron Bolometer (HEB) mixers made of 10 nm MgB2 films. A systematic investigation of the (IF) gain bandwidth as a function of the MgB2 film thickness (30 nm, 15 nm and 10 nm) is also presented. The gain bandwidth (GBW) of 3.4 GHz was measured for a 10 nm film, corresponding to a mixer time constant of 47 ps. For 10 nm films a reduction of the GBW was observed with the reduction of the critical temperature (Tc). Experimental data were analyzed using the two-temperature model. From the theoretical analysis, the electron-phonon time (τe-ph), the phonon escape time (τesc) and the electron and phonon specific heats (ce, cph) were extrapolated giving the first model for HEB mixers of MgB2 films.
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| 7. |
- Bevilacqua, Stella, 1981, et al.
(författare)
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Submicrometer MgB2 hot electron bolometer mixers
- 2013
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Ingår i: The 24th International Symposium on Space Terahertz Technology.
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Konferensbidrag (refereegranskat)abstract
- Phonon-cooled hot electron bolometer mixers based on MgB2 film are promising candidates for THz radio astronomy at frequency above 1 THz. The short electron-phonon interaction time and the high critical temperature of the MgB2 (39 K in the bulk), compared to other intermetallic compounds, make it suitable for applications where wide IF bandwidth and low noise are needed. The currently achieved gain and noise bandwidths are 3.4 GHz and 7 GHz for HEBs fabricated in 10 nm MgB2 films. The noise temperature of 800 K was measured at 600 GHz local oscillator (LO) frequency using the Y-factor technique.MgB2 has been demonstrated to be sensitive to the oxygen as well as water, therefore it makes the fabrication of sub-µm HEBs very challenging. HEBs were fabricated using electron beam lithography in 10 nm MgB2 films with a bolometer area in the range of 0.09 and 0.25 µm2. We report the performance of the devices respect to the noise temperature at LO frequency up to 2.5 THz. Using the isothermal technique the LO power requirement was estimated respect to the bolometer area. Based on the material parameters obtained from the experiments, the two temperature model simulations showed a gain bandwidth as large as 8-10 GHz for thin MgB2 films.
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| 8. |
- Hudson, Thomas J., et al.
(författare)
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International network of cancer genome projects
- 2010
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 464:7291, s. 993-998
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Tidskriftsartikel (refereegranskat)abstract
- The International Cancer Genome Consortium (ICGC) was launched to coordinate large-scale cancer genome studies in tumours from 50 different cancer types and/or subtypes that are of clinical and societal importance across the globe. Systematic studies of more than 25,000 cancer genomes at the genomic, epigenomic and transcriptomic levels will reveal the repertoire of oncogenic mutations, uncover traces of the mutagenic influences, define clinically relevant subtypes for prognosis and therapeutic management, and enable the development of new cancer therapies.
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| 9. |
- Janis, Jesper, et al.
(författare)
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An experimental study on the influence of particles on grain boundary migration
- 2010
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Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 45:8, s. 2233-2238
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Tidskriftsartikel (refereegranskat)abstract
- The pinning effect of particles on grain boundary migration was studied in a Fe-20 mass % Cr alloy deoxidised with Ti and Zr. The different nitrogen contents (65, 248 and 490 ppm) were used to vary the number of precipitated inclusions. The specimens from equiaxed zones of metal samples with different particle densities were examined by in situ observations during a 60-min holding time at 1200 and 1400 degrees C in a Confocal Scanning Laser Microscope. The change of particles pinning effect on the grain growth was described by an average grain size, (D) over bar (A), and the ratio between the perimeter and area of grains, P-GB/A(G). It was found that the pinning effect of particles (mostly complex Ti-Zr oxynitrides) on grain growth decreased with a decreased nitrogen content in the metal. Furthermore, the effect of particles decreased with an increased temperature of treatment, due to the reduction of the number of particles on the grain boundaries.
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| 10. |
- Liu, Qiang, et al.
(författare)
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Dynamic Precipitation Behavior of Secondary M7C3 Carbides in Ti-alloyed High Chromium Cast Iron
- 2013
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Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 53:7, s. 1237-1244
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Tidskriftsartikel (refereegranskat)abstract
- In-situ observations on the dynamic precipitation behavior of secondary carbides in Ti-alloyed High Chromium Cast Iron (HCCI) were performed by using a Confocal Laser Scanning Microscope (CLSM). Moreover, the detailed characterization of the microstructure before and after heat treatment was performed by using scanning electron microscopy (SEM). The secondary carbides, which precipitate from the matrix during heat treatment, were identified as M7C3 type carbides by using transmission electron microscopy (TEM). The number, size and volume of secondary carbides during heating, holding and cooling process were quantitatively evaluated based on the in-situ observation and SEM results. It was found that ferrite (alpha) and secondary carbides start to precipitate from the matrix at around 575 degrees C and 840 degrees C, respectively, during the heating process. In addition, the in-situ results showed that the number of secondary carbides increase with an increased heating temperature and time. Moreover, it was found that the size of these secondary carbides increase at higher temperatures and longer holding times. However, the number of secondary carbides increased with a decreased temperature. Finally, it was found that the volume fraction (similar to 5%) of secondary carbides was not changed to a large extent for the different heat treatment conditions being investigated.
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