| 1. |
- Abadie, J., et al.
(author)
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Implementation and testing of the first prompt search for gravitational wave transients with electromagnetic counterparts
- 2012
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In: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 539
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Journal article (peer-reviewed)abstract
- Aims. A transient astrophysical event observed in both gravitational wave (GW) and electromagnetic (EM) channels would yield rich scientific rewards. A first program initiating EM follow-ups to possible transient GW events has been developed and exercised by the LIGO and Virgo community in association with several partners. In this paper, we describe and evaluate the methods used to promptly identify and localize GW event candidates and to request images of targeted sky locations. Methods. During two observing periods (Dec. 17, 2009 to Jan. 8, 2010 and Sep. 2 to Oct. 20, 2010), a low-latency analysis pipeline was used to identify GW event candidates and to reconstruct maps of possible sky locations. A catalog of nearby galaxies and Milky Way globular clusters was used to select the most promising sky positions to be imaged, and this directional information was delivered to EM observatories with time lags of about thirty minutes. A Monte Carlo simulation has been used to evaluate the low-latency GW pipeline's ability to reconstruct source positions correctly. Results. For signals near the detection threshold, our low-latency algorithms often localized simulated GW burst signals to tens of square degrees, while neutron star/neutron star inspirals and neutron star/black hole inspirals were localized to a few hundred square degrees. Localization precision improves for moderately stronger signals. The correct sky location of signals well above threshold and originating from nearby galaxies may be observed with similar to 50% or better probability with a few pointings of wide-field telescopes.
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| 2. |
- Abadie, J., et al.
(author)
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Search for gravitational waves from low mass compact binary coalescence in LIGO's sixth science run and Virgo's science runs 2 and 3
- 2012
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In: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 85:8
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Journal article (peer-reviewed)abstract
- We report on a search for gravitational waves from coalescing compact binaries using LIGO and Virgo observations between July 7, 2009, and October 20, 2010. We searched for signals from binaries with total mass between 2 and 25M(circle dot); this includes binary neutron stars, binary black holes, and binaries consisting of a black hole and neutron star. The detectors were sensitive to systems up to 40 Mpc distant for binary neutron stars, and further for higher mass systems. No gravitational-wave signals were detected. We report upper limits on the rate of compact binary coalescence as a function of total mass, including the results from previous LIGO and Virgo observations. The cumulative 90% confidence rate upper limits of the binary coalescence of binary neutron star, neutron star-black hole, and binary black hole systems are 1.3 x 10(-4), 3.1 x 10(-5), and 6.4 x 10(-6) Mpc(-3) yr(-1), respectively. These upper limits are up to a factor 1.4 lower than previously derived limits. We also report on results from a blind injection challenge.
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| 3. |
- Abadie, J., et al.
(author)
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All-sky search for periodic gravitational waves in the full S5 LIGO data
- 2012
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In: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 85:2
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Journal article (peer-reviewed)abstract
- We report on an all-sky search for periodic gravitational waves in the frequency band 50-800 Hz and with the frequency time derivative in the range of 0 through -6 x 10(-9) Hz/s. Such a signal could be produced by a nearby spinning and slightly nonaxisymmetric isolated neutron star in our Galaxy. After recent improvements in the search program that yielded a 10x increase in computational efficiency, we have searched in two years of data collected during LIGO's fifth science run and have obtained the most sensitive all-sky upper limits on gravitational-wave strain to date. Near 150 Hz our upper limit on worst-case linearly polarized strain amplitude h(0) is 1 x 10(-24), while at the high end of our frequency range we achieve a worst-case upper limit of 3.8 x 10(-24) for all polarizations and sky locations. These results constitute a factor of 2 improvement upon previously published data. A new detection pipeline utilizing a loosely coherent algorithm was able to follow up weaker outliers, increasing the volume of space where signals can be detected by a factor of 10, but has not revealed any gravitational-wave signals. The pipeline has been tested for robustness with respect to deviations from the model of an isolated neutron star, such as caused by a low-mass or long-period binary companion.
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| 4. |
- Johansson, Jonas, et al.
(author)
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Solar disinfection at low costs: an experimental approach towards up-scaled continuous flow systems
- 2022
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In: H2open Journal. - : IWA Publishing. - 2616-6518. ; 5:1, s. 153-165
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Journal article (peer-reviewed)abstract
- SOlar DISinfection (SODIS) systems have been studied with the aim of maintaining pathogen removal efficiencies and low costs. Such systems are useful for quickly improving the situation of more than 700 million people worldwide that lack access to an improved water source. Currently, SODIS is mainly used with PET-bottles that are exposed to UV-A radiation for 6 h in the sun. Up-scaled continuous flow SODIS systems could instead provide a continuous source of drinking water, whereas the use of plastic tubes, easily available on local markets, ensures a low construction cost of the systems. Such tubes (PVC) were tested and the best option showed a UV-A transparency ratio of similar to 50%, to be compared with similar to 60% for PET-bottles. By using static batches in samples of this tube, the residence time was investigated and the results show that E. coli concentrations of 0 CFU/ml are reached within less than 4 h of exposure to solar radiation, starting from an initial concentration of 10(6) CFU/ml. It can be concluded that cheap, easily available plastic tubes can be used for treating contaminated water with the SODIS technique, which is promising for future investigations towards constructing continuous flow SODIS systems at low costs.
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| 5. |
- Usachov, D. Yu, et al.
(author)
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Cubic Rashba Effect in the Surface Spin Structure of Rare-Earth Ternary Materials
- 2020
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In: Physical Review Letters. - 0031-9007. ; 124:23
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Journal article (peer-reviewed)abstract
- Spin-orbit interaction and structure inversion asymmetry in combination with magnetic ordering is a promising route to novel materials with highly mobile spin-polarized carriers at the surface. Spin-resolved measurements of the photoemission current from the Si-terminated surface of the antiferromagnet TbRh2Si2 and their analysis within an ab initio one-step theory unveil an unusual triple winding of the electron spin along the fourfold-symmetric constant energy contours of the surface states. A two-band k·p model is presented that yields the triple winding as a cubic Rashba effect. The curious in-plane spin-momentum locking is remarkably robust and remains intact across a paramagnetic-antiferromagnetic transition in spite of spin-orbit interaction on Rh atoms being considerably weaker than the out-of-plane exchange field due to the Tb 4f moments.
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| 6. |
- Londono, E. A. M., et al.
(author)
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Solid biofuels production from energy crops in Colombia: challenges and opportunities
- 2016
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In: Biofuels, Bioproducts and Biorefining. - : Wiley. - 1932-1031 .- 1932-104X. ; 10:4, s. 359-368
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Journal article (peer-reviewed)abstract
- Building on an extensive literature review that included peer-reviewed publications, grey literature, national statistics, official reports, and regulations enacted by the Colombian government, this paper identifies opportunities, challenges, and constraints faced by solid biofuels production from energy crops in Colombia. Our findings suggest that the solid biofuels industry currently lacks policy regulations and an adequate research framework. The paper notes the industry's market potential and addresses its dependency on a legal framework, political willingness, and technological developments. The legal framework includes land ownership formalization, job regulations, and the definition of environmental and administrative permits. Political willingness relates to governmental policies and financial incentives based on environmental and sustainability criteria, which can make the sector competitive compared to other energy sources at the local and international market scales. The technological aspects include public and private support for research and development programs and a strategic analysis of industry-specific requirements for infrastructure, conversion, and transportation within a life cycle assessment framework. The preliminary land-use analysis suggests the potential availability of land for solid biofuels production in the Caribbean, Andean, Inter-Andean Valley, and Orinoco regions. Furthermore, the results show that solid biofuels production can potentially supply internal demand and play a role in international markets with strategic development and government support.
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