| 1. |
- Andreoni, I., et al.
(författare)
-
Follow Up of GW170817 and Its Electromagnetic Counterpart by Australian-Led Observing Programmes
- 2017
-
Ingår i: Publications Astronomical Society of Australia. - : Cambridge University Press (CUP). - 1323-3580 .- 1448-6083. ; 34
-
Forskningsöversikt (refereegranskat)abstract
- The discovery of the first electromagnetic counterpart to a gravitational wave signal has generated follow-up observations by over 50 facilities world-wide, ushering in the new era of multi-messenger astronomy. In this paper, we present follow-up observations of the gravitational wave event GW170817 and its electromagnetic counterpart SSS17a/DLT17ck (IAU label AT2017gfo) by 14 Australian telescopes and partner observatories as part of Australian-based and Australian-led research programs. We report early- to late-time multi-wavelength observations, including optical imaging and spectroscopy, mid-infrared imaging, radio imaging, and searches for fast radio bursts. Our optical spectra reveal that the transient source emission cooled from approximately 6 400 K to 2 100 K over a 7-d period and produced no significant optical emission lines. The spectral profiles, cooling rate, and photometric light curves are consistent with the expected outburst and subsequent processes of a binary neutron star merger. Star formation in the host galaxy probably ceased at least a Gyr ago, although there is evidence for a galaxy merger. Binary pulsars with short (100 Myr) decay times are therefore unlikely progenitors, but pulsars like PSR B1534+12 with its 2.7 Gyr coalescence time could produce such a merger. The displacement (similar to 2.2 kpc) of the binary star system from the centre of the main galaxy is not unusual for stars in the host galaxy or stars originating in the merging galaxy, and therefore any constraints on the kick velocity imparted to the progenitor are poor.
|
|
| 2. |
|
|
| 3. |
- Bradnam, K. R., et al.
(författare)
-
Assemblathon 2 : Evaluating de novo methods of genome assembly in three vertebrate species
- 2013
-
Ingår i: GigaScience. - : BioMed Central (BMC). - 2047-217X. ; 2:1
-
Tidskriftsartikel (refereegranskat)abstract
- Background: The process of generating raw genome sequence data continues to become cheaper, faster, and more accurate. However, assembly of such data into high-quality, finished genome sequences remains challenging. Many genome assembly tools are available, but they differ greatly in terms of their performance (speed, scalability, hardware requirements, acceptance of newer read technologies) and in their final output (composition of assembled sequence). More importantly, it remains largely unclear how to best assess the quality of assembled genome sequences. The Assemblathon competitions are intended to assess current state-of-the-art methods in genome assembly. Results: In Assemblathon 2, we provided a variety of sequence data to be assembled for three vertebrate species (a bird, a fish, and snake). This resulted in a total of 43 submitted assemblies from 21 participating teams. We evaluated these assemblies using a combination of optical map data, Fosmid sequences, and several statistical methods. From over 100 different metrics, we chose ten key measures by which to assess the overall quality of the assemblies. Conclusions: Many current genome assemblers produced useful assemblies, containing a significant representation of their genes and overall genome structure. However, the high degree of variability between the entries suggests that there is still much room for improvement in the field of genome assembly and that approaches which work well in assembling the genome of one species may not necessarily work well for another.
|
|
| 4. |
- Frisk, U., et al.
(författare)
-
The Odin satellite - I. Radiometer design and test
- 2003
-
Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 402:3, s. L27-L34
-
Tidskriftsartikel (refereegranskat)abstract
- The Sub-millimetre and Millimetre Radiometer (SMR) is the main instrument on the Swedish, Canadian, Finnish and French spacecraft Odin. It consists of a 1.1 metre diameter telescope with four tuneable heterodyne receivers covering the ranges 486-504 GHz and 541-581 GHz, and one fixed at 118.75 GHz together with backends that provide spectral resolution from 150 kHz to 1 MHz. This Letter describes the Odin radiometer, its operation and performance with the data processing and calibration described in Paper II.
|
|
| 5. |
|
|
| 6. |
- Bhat, N. D. R., et al.
(författare)
-
Observations of Low-frequency Radio Emission from Millisecond Pulsars and Multipath Propagation in the Interstellar Medium
- 2018
-
Ingår i: Astrophysical Journal, Supplement Series. - : American Astronomical Society. - 1538-4365 .- 0067-0049. ; 238:1
-
Tidskriftsartikel (refereegranskat)abstract
- Studying the gravitational-wave sky with pulsar timing arrays (PTAs) is a key science goal for the Square Kilometre Array (SKA) and its pathfinder telescopes. With current PTAs reaching sub-microsecond timing precision, making accurate measurements of interstellar propagation effects and mitigating them effectively has become increasingly important to realize PTA goals. As these effects are much stronger at longer wavelengths, low-frequency observations are most appealing for characterizing the interstellar medium (ISM) along the sight lines toward PTA pulsars. The Murchison Widefield Array (MWA) and the Engineering Development Array (EDA), which utilizes MWA technologies, present promising opportunities for undertaking such studies, particularly for PTA pulsars located in the southern sky. Such pulsars are also the prime targets for PTA efforts planned with the South African MeerKAT, and eventually with the SKA. In this paper we report on observations of two bright southern millisecond pulsars, PSR J0437-4715 and PSR J2145-0750, made with these facilities; MWA observations sampled multiple frequencies across the 80-250 MHz frequency range, while the EDA provided direct-sampled baseband data to yield a large instantaneous usable bandwidth of similar to 200 MHz. Using these exploratory observations, we investigate various aspects relating to pulsar emission and ISM properties, such as spectral evolution of the mean pulse shape, scintillation as a function of frequency, chromaticity in interstellar dispersion, and flux density spectra at low frequencies. Systematic and regular monitoring observations will help ascertain the role of low-frequency measurements in PTA experiments, while simultaneously providing a detailed characterization of the ISM toward the pulsars, which will be useful in devising optimal observing strategies for future PTA experiments.
|
|
| 7. |
- Hammar, Arvid, 1986, et al.
(författare)
-
Optical designs for a multi-beam 340 and 625/640 GHz Spaceborne climate research instrument
- 2015
-
Ingår i: 26th International Symposium on Space Terahertz Technology, ISSTT 2015.
-
Konferensbidrag (refereegranskat)abstract
- We report on an ongoing study where different optical configurations for a multi-beam limb-viewing (four to eight receiver channels at 340 and two channels at 625 GHz) space-borne instrument for climate research are presented and compared. The optical configurations are analyzed in terms of optical performance (gain, side lobe levels, beam efficiency etc.), weight and size of the overall instrument envelope. Using ideal fundamental Gaussian beam modes and numerical tools relying on ray-tracing and physical optics methods, the different configurations are designed and evaluated. Preliminary results indicate that a 1.3 m × 0.65 m primary reflector can be used in a configuration that includes a relay optics system having two to four elements. In addition to the limb-viewing instrument, there will be an additional instrument operating at 640 GHz for observing clouds in nadir mode.
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
|
|
| 11. |
|
|
| 12. |
|
|
| 13. |
|
|
| 14. |
- Vassilev, Vessen, 1969, et al.
(författare)
-
MMIC-Based Components for MM-Wave Instrumentation
- 2010
-
Ingår i: IEEE Microwave and Wireless Components Letters. - 1558-1764 .- 1531-1309. ; 20:10, s. 578-580
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In this letter, we present results of fully integrated 90-130 GHz receiver based on 100 nm mHEMT technology. The receiver contains a low noise amplifier (LNA), mixer and LO multiplier chain integrated into a single monolithic microwave integrated circuit (MMIC). The circuit is packaged into a waveguide block, characterized and compared to on-wafer measurements. Waveguide to microstrip transitions are used to interface the MMIC to the waveguide. A breakout LNA circuit is also packaged, and its performance is compared to the receiver. The LNA noise was characterized on a wafer and after packaging. The packaged module is measured at both room and cryogenic temperatures, NF of 3.7 dB is measured at 300 K and 0.9 dB at 20 K.
|
|
| 15. |
- Vassilev, Vessen, 1969, et al.
(författare)
-
MMIC-based receivers for mm-wave radiometry
- 2010
-
Ingår i: IRMMW-THz 2010 - 35th International Conference on Infrared, Millimeter, and Terahertz Waves, Conference Guide. - 9781424466573
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We present results of packaged mm-wave receiver components based on 100nm mHEMT technology. The components are to be used for observations of the atmospheric lines at 118 GHz and 183 GHz. A 90-130 GHz single-chip receiver MMIC, including LNA, mixer and LO multiplier chain, is packaged in to a waveguide block, characterized and compared to on-wafer measurements. A breakout LNA circuit is also packaged and its performance is compared to the receiver. A 183 GHz source is designed to be used as a LO source.
|
|
| 16. |
- Chen, Tianhui, et al.
(författare)
-
Distribution and risk of the second discordant primary cancers combined after a specific first primary cancer in German and Swedish cancer registries.
- 2015
-
Ingår i: Cancer Letters. - : Elsevier BV. - 1872-7980 .- 0304-3835. ; 369:1, s. 152-166
-
Tidskriftsartikel (refereegranskat)abstract
- We aimed at investigating the distribution and risk of all second discordant primary cancers (SDPCs) after a specific first primary cancer in Germany and Sweden to provide etiological understanding of SDPCs and insight into their incidence rates and recording practices. Among 1,537,004 survivors of first primary cancers in Germany and 588,103 in Sweden, overall 80,162 and 32,544 SDPCs were recorded, respectively. Standardized incidence ratios (SIRs) of all SDPCs were elevated at levels between 1.1 and 2.1 after 23 (out of overall 29) cancers in Germany and at levels between 1.1 and 1.6 after 24 cancers in Sweden, and among them, elevated SIRs were found after 19 cancers in both populations. Decreased SIRs at levels ranging from 0.5 to 0.9 were found for some cancers with poor prognosis in Germany only. We found elevated risk after 19 out of 29 cancers in both countries, suggesting common etiology of SDPCs after most of first cancers and registration similarity. Decreased risks after some fatal cancers were found only in Germany, which may be attributed to reporting practices or missed death data in Germany.
|
|
| 17. |
- Chen, Tianhui, et al.
(författare)
-
Risk of Second Primary Cancers in Multiple Myeloma Survivors in German and Swedish Cancer Registries.
- 2016
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
-
Tidskriftsartikel (refereegranskat)abstract
- We aimed at investigating the distribution and risk of second primary cancers (SPCs) in multiple myeloma (MM) survivors in Germany and Sweden to provide etiological understanding of SPCs and insight into their incidence rates and recording practices. MM patients diagnosed in 1997-2010 at age ≥15 years were selected from the Swedish (nationwide) and 12 German cancer registries. Standardized incidence ratios (SIRs) were used to assess risk of a specific SPC compared to risk of the same first cancer in the corresponding background population. Among 18,735 survivors of first MM in Germany and 7,560 in Sweden, overall 752 and 349 SPCs were recorded, respectively. Significantly elevated SIRs of specific SPCs were observed for acute myeloid leukemia (AML; SIR = 4.9) in Germany and for kidney cancer (2.3), AML (2.3) and nervous system cancer (1.9) in Sweden. Elevated risk for AML was more pronounced in the earlier diagnosis period compared to the later, i.e., 9.7 (4.2-19) for 1997-2003 period versus 3.5 (1.5-6.9) for 2004-2010 in Germany; 3.8 (1.4-8.3) for 1997-2003 versus 2.2 (0.3-7.8) for 2004-2010 in Sweden. We found elevated risk for AML for overall, early diagnosis periods and longer follow-up times in both populations, suggesting possible side effects of treatment for MM patients.
|
|
| 18. |
- Cherednichenko, Serguei, 1970, et al.
(författare)
-
Water vapor radiometer for ALMA: Optical design and verification
- 2010
-
Ingår i: 21st International Symposium on Space Terahertz Technology 2010, ISSTT 2010; Oxford; United Kingdom; 23 March 2010 through 25 March 2010. - 9781617823626 ; , s. 340-
-
Konferensbidrag (refereegranskat)abstract
- Atacama Large Millimeter wave Array (ALMA) is being built at a high altitude Atacama Desert in Chile. It will consist of 50 12m telescopes with heterodyne instruments to cover a large frequency range from about 30GHz to nearly 1THz. In order to facilitate the interferometer mode of operation all receivers have to be phase synchronized. It will be accomplished by phase locking of all local oscillators from a single reference source. However, a noticeable part of the phase error is caused as the signal propagates through the Earth atmosphere. Since this effect originates from the fluctuations of water vapors, it can be accounted for by carefully measuring the spectral width of one of water vapor resonance absorption lines. This will be done with a submillimeter heterodyne radiometer, Water Vapor Radiometer (WVR) [1]. WVR will measure the sky brightness temperature in the beam path of every telescope across the 183GHz water line with a spectral resolution of about 1GHz. Accuracy of the calculated optical delay is determined by the combination of the radiometric accuracy of the WVR and of the errors originated in the WVR illumination of the telescope. We will describe major challenges in the design of the WVR to comply with the stringent requirements set to the WVR. Several approaches to simulate the quasioptical waveguide which brings the signal from the telescope's subreflector to the mixer horn, were used: fundamental mode Gaussian beam propagation, combined ray tracing with diffraction effects (using package ZEMAX), and a full vector electromagnetic simulations (using GRASP). The computational time increases rapidly from the first method to the last one. We have found that ZEMAX results are quite close to the one from GRASP, however obtained with nearly instant computation, which allows multiple iterations during system optimization. The beam pattern of the WVR and of WVR with the optical Relay (used to bring the signal from the telescope's main axis to the WVR input window) was measured by a scalar beam scan at four planes in the far field. The experimental results correspond to the simulated ones with a high accuracy. The WVR illuminates the telescope subreflector with a spillover of less than 1.5% while maintaining high aperture efficiency. We developed an approach to calculate the beam center position at the subreflector (with is at 6m from the WVR) from our test data (at maximum 2m from the WVR) in order confirm the maximum beam deviation does not exceed 20mm, i.e. 1/15 of the beam width.
|
|
| 19. |
- Edman, Anders, 1966-, et al.
(författare)
-
A low-power 416-lag 1.5-b 0.5-TMAC correlator in 0.6um CMOS.
- 2001
-
Ingår i: IEEE Journal of Solid-State Circuits. - 0018-9200 .- 1558-173X. ; 36, s. 258-265
-
Tidskriftsartikel (refereegranskat)abstract
- The autocorrelation spectrometer is an important instrument for radio astronomy. In satellite-based spectrometers, low power consumption is essential. The correlator chip presented in this paper reduces the power consumption more than five times compared to other full-custom designs. This has been achieved by reducing the number of clocked transistors, using a compact layout of cells, which reduces wire lengths, and using parallel processing of data. Also, the low power performance is combined with a large number of lags and a high data throughput. The correlator performs 0.5-TMAC operations in 416 lags at a sample rate of 1.28-GSample/s with an input data precision of 1.5-b and a correlation period of one second. The chip is also designed to reduce noise generation by using multiple internal clock phases.
|
|
| 20. |
- Jacob, Karl, et al.
(författare)
-
Radiometric performance of the 530 to 625 GHz receiver unit of the submillimetre wave instrument on juice
- 2019
-
Ingår i: ISSTT 2019 - 30th International Symposium on Space Terahertz Technology, Proceedings Book. ; , s. 28-31
-
Konferensbidrag (refereegranskat)abstract
- The upcoming Submillimeter Wave Instrument on the JUICE spacecraft is a passive radiometer/spectrometer instrument with two heterodyne receivers which are independently tunable in the frequency bands 530 to 625 GHz and 1080 to 1275 GHz. It will study Jupiter’s atmosphere as well as the atmospheres and surface properties of the Galilean moons. This work presents the results of first radiometric tests with a prototype of the 600 GHz receiver. In this context, the baseline ripples caused by the internal calibration target have been characterized using two conical prototypes with a linear and an exponential absorber coating profile. A significant reduction of the baseline ripple amplitude has been measured with the target having the exponential cone profile. The spectroscopic baseline has been characterized for various frequency steps when applying frequency switching as an alternative calibration mode. At some operating frequencies a very flat switching baseline has been measured for frequency throws up to 90 MHz, while at other frequencies significant spectral distortions are measured even with a step size of 22.5 MHz. The first radiometric tests of the sideband gain ratio with a passive Fourier Transform Spectroscopy method demonstrate the general applicability in the 530 to 625 GHz band.
|
|
| 21. |
|
|
| 22. |
- Ryman, Erik J, 1982, et al.
(författare)
-
1.6 GHz Low-Power Cross-Correlator System Enabling Geostationary Earth Orbit Aperture Synthesis
- 2014
-
Ingår i: IEEE Journal of Solid-State Circuits. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9200 .- 1558-173X. ; 49:11, s. 2720-2729
-
Tidskriftsartikel (refereegranskat)abstract
- We present a 64-channel cross-correlator system for space-borne synthetic aperture imaging. Two different types of ASICs were developed to fit into this system: An 8-channel comparator ASIC implemented in a 130 nm SiGe BiCMOS process technology performs A/D conversion, while a single 64-channel digital cross-correlator ASIC implemented in a 65 nm CMOS process performs the signal processing. The digital ASIC handles 2016 cross-correlations at up to 3.6 GS/s and has a power dissipation of only 0.13 mW/correlation/GHz at a supply voltage of 1 V. The comparator ASIC can handle sample rates of at least 4.5 GS/s with a power dissipation of 47 mW/channel or 1 GS/s with a power dissipation of 17 mW/channel. The assembled system consists of a single board measuring a mere 136 x 136 mm(2) and weighing only 135 g. The assembled system demonstrates crosstalk of 0.04% between neighboring channels and stability of 800 s. We provide ASIC and system-board measurement results that demonstrate that aperture synthesis can be a viable approach for Earth observation from a geostationary Earth orbit.
|
|
| 23. |
|
|
| 24. |
- Sobis, Peter, 1978, et al.
(författare)
-
A 170 GHz 45 degree Hybrid for Submillimeter Wave Sideband Separating Subharmonic Mixers
- 2008
-
Ingår i: IEEE Microwave and Wireless Components Letters. - 1558-1764 .- 1531-1309. ; 18:10, s. 680-682
-
Tidskriftsartikel (refereegranskat)abstract
- We present a 135/45 degree phase shifter hybrid intended to be used in subharmonic sideband separation mixer schemes at submillimeter-wave frequencies. The design consists of an increased height 90 degree 6-arm branch guide coupler with a three stub loaded differential line 45 degree phase shifter at the output. The device has been implemented at G-band in an E-plane WR-05 splitblock design with a center frequency of 170 GHz and 15% bandwidth. Measured S-parameter are in good agreement with simulations showing an isolation and return loss better than 20 dB and an amplitude and phase imbalance within 0.4 dB and 2 degree, respectively.
|
|
| 25. |
- Sobis, Peter, 1978, et al.
(författare)
-
Towards a THz Sideband Separating Subharmonic Schottky Mixer
- 2008
-
Ingår i: GigaHertz SympoSium 2008, p. 46.
-
Konferensbidrag (refereegranskat)abstract
- GaAs Schottky mixers with state of the art planar submicron diodes are used for THz-detection up to 3 THz today [1]. GaAs Schottky diodes can operate in room temperature which makes them good candidates for space applications and an interesting low cost alternative to low noise cryogenic SIS and HEB technologies. The main advantage of a sideband separation scheme besides that the lower and upper sidebands are indeed separated, is that the IF bandwidth is increased by a factor of two. Moreover, there is no need for image rejection filters on the RF input, which can be bulky and increase the weight and cost of the overall receiver system. Sideband separation mixers have been implemented at THz frequencies before [2], however up to this point they have never been tried with Schottky diodes in a subharmonic mixer configuration. We will present the current status of the development of a novel sideband separating subharmonic reciever topology operating at 340 GHz, see Fig1. The design of a subharmonic mixer and the LO and RF waveguide hybrids will be presented followed by an account of measured results of the individual components.
|
|
