| 1. |
- Veres, P., et al.
(författare)
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Observation of inverse Compton emission from a long gamma-ray burst
- 2019
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Ingår i: Nature. - : NATURE PUBLISHING GROUP. - 0028-0836 .- 1476-4687. ; 575:7783, s. 459-
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Tidskriftsartikel (refereegranskat)abstract
- Long-duration gamma-ray bursts (GRBs) originate from ultra-relativistic jets launched from the collapsing cores of dying massive stars. They are characterized by an initial phase of bright and highly variable radiation in the kiloelectron volt-to-mega electronvoltband, which is probably produced within the jet and lasts from milliseconds to minutes, known as the prompt emission(1,2). Subsequently, the interaction of the jet with the surrounding medium generates shock waves that are responsible for the afterglow emission, which lasts from days to months and occurs over a broad energy range from the radio to the gigaelectronvolt bands(1-6). The afterglow emission is generally well explained as synchrotron radiation emitted by electrons accelerated by the external shock(7-9). Recently, intense long-lasting emission between 0.2 and 1 teraelectronvolts was observed from GRB 190114C(10,11). Here we report multifrequency observations of GRB 190114C, and study the evolution in time of the GRB emission across 17 orders of magnitude in energy, from 5 x 10(-6) to 10(12) electronvolts. We find that the broadband spectral energy distribution is double-peaked, with the teraelectronvolt emission constituting a distinct spectral component with power comparable to the synchrotron component. This component is associated with the afterglow and is satisfactorily explained by inverse Compton up-scattering of synchrotron photons by high-energy electrons. We find that the conditions required to account for the observed teraelectronvolt component are typical for GRBs, supporting the possibility that inverse Compton emission is commonly produced in GRBs.
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| 2. |
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| 3. |
- Sung, Yun Ju, et al.
(författare)
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A multi-ancestry genome-wide study incorporating gene-smoking interactions identifies multiple new loci for pulse pressure and mean arterial pressure
- 2019
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Ingår i: Human Molecular Genetics. - : Oxford University Press. - 0964-6906 .- 1460-2083. ; 28:15, s. 2615-2633
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Tidskriftsartikel (refereegranskat)abstract
- Elevated blood pressure (BP), a leading cause of global morbidity and mortality, is influenced by both genetic and lifestyle factors. Cigarette smoking is one such lifestyle factor. Across five ancestries, we performed a genome-wide gene–smoking interaction study of mean arterial pressure (MAP) and pulse pressure (PP) in 129 913 individuals in stage 1 and follow-up analysis in 480 178 additional individuals in stage 2. We report here 136 loci significantly associated with MAP and/or PP. Of these, 61 were previously published through main-effect analysis of BP traits, 37 were recently reported by us for systolic BP and/or diastolic BP through gene–smoking interaction analysis and 38 were newly identified (P < 5 × 10−8, false discovery rate < 0.05). We also identified nine new signals near known loci. Of the 136 loci, 8 showed significant interaction with smoking status. They include CSMD1 previously reported for insulin resistance and BP in the spontaneously hypertensive rats. Many of the 38 new loci show biologic plausibility for a role in BP regulation. SLC26A7 encodes a chloride/bicarbonate exchanger expressed in the renal outer medullary collecting duct. AVPR1A is widely expressed, including in vascular smooth muscle cells, kidney, myocardium and brain. FHAD1 is a long non-coding RNA overexpressed in heart failure. TMEM51 was associated with contractile function in cardiomyocytes. CASP9 plays a central role in cardiomyocyte apoptosis. Identified only in African ancestry were 30 novel loci. Our findings highlight the value of multi-ancestry investigations, particularly in studies of interaction with lifestyle factors, where genomic and lifestyle differences may contribute to novel findings.
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| 4. |
- Hedman, E., et al.
(författare)
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Effectiveness of Internet-based cognitive behaviour therapy for panic disorder in routine psychiatric care
- 2013
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Ingår i: Acta Psychiatrica Scandinavica. - : Wiley. - 0001-690X .- 1600-0447. ; 128:6, s. 457-467
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Tidskriftsartikel (refereegranskat)abstract
- ObjectiveGuided Internet-based cognitive behaviour therapy (ICBT) for panic disorder has been shown to be efficacious in several randomized controlled trials. However, the effectiveness of the treatment when delivered within routine psychiatric care has not been studied. The aim of this study was to investigate the effectiveness of ICBT for panic disorder within the context of routine psychiatric care. MethodWe conducted a cohort study investigating all patients (n=570) who had received guided ICBT for panic disorder between 2007 and 2012 in a routine care setting at an out-patient psychiatric clinic providing Internet-based treatment. The primary outcome measure was the Panic Disorder Severity Scale-Self-report (PDSS-SR). ResultsParticipants made large improvements from screening and pretreatment assessments to posttreatment (Cohen's d range on the PDSS-SR=1.07-1.55). Improvements were sustained at 6-month follow-up. ConclusionThis study suggests that ICBT for panic disorder is as effective when delivered in a routine care context as in the previously published randomized controlled trials.
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| 5. |
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| 6. |
- Hamed Abd El Mageed, Yasser, et al.
(författare)
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Comparison between rainfall simulator erosion and observed reservoir sedimentation in an erosion-sensitive semiarid catchment
- 2002
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Ingår i: Catena. - 0341-8162. ; 50:1, s. 1-16
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Tidskriftsartikel (refereegranskat)abstract
- Estimating catchment scale soil loss based on rainfall simulators is often hampered by the difficulty to scale up simulator results. Our objective was to develop and test a method for estimating catchment scale soil loss based on observed rainfall using a variable intensity rainfall simulator in an erosion-sensitive catchment in semiarid Tunisia. A 7-year period, 1992-1999, with observed sedimentation amounts in a downstream reservoir was chosen to test a methodology. The methodology was based on (1) energy adjustment for the used simulator due to the difference in kinetic energy of simulated and natural rainfall at equal intensities and (2) upscaling of simulated erosion in which rill erosion was estimated by adjusting the difference between slope lengths for the plots versus the catchment after onset of runoff. The comparison between calculated soil loss from rainfall simulator experiments and observed sedimentation in the downstream reservoir displayed good overall results. Calculated soil loss was found to be about 96%, 36%, and 80% for different observed subperiods, respectively. The observed low value for the second period was probably due an exceptionally intense rainfall event during this period, which appears to have led to gully erosion, soil slide, and riverbank collapse. Therefore, during this event, siltation in the reservoir may essentially be due to unaccounted erosion processes such as gully erosion. Overall, however, it appears that plot-scale variable intensity rainfall simulators can rather successfully estimate catchment scale soil losses. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 7. |
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| 8. |
- Nasri, Amin, et al.
(författare)
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Network-Constrained AC Unit Commitment Under Uncertainty : A Benders' Decomposition Approach
- 2016
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Ingår i: IEEE Transactions on Power Systems. - : IEEE. - 0885-8950 .- 1558-0679. ; 31:1, s. 412-422
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes an efficient solution approach based on Benders' decomposition to solve a network-constrained ac unit commitment problem under uncertainty. The wind power production is the only source of uncertainty considered in this paper, which is modeled through a suitable set of scenarios. The proposed model is formulated as a two-stage stochastic programming problem, whose first-stage refers to the day-ahead market, and whose second-stage represents real-time operation. The proposed Benders' approach allows decomposing the original problem, which is mixed-integer nonlinear and generally intractable, into a mixed-integer linear master problem and a set of nonlinear, but continuous subproblems, one per scenario. In addition, to temporally decompose the proposed ac unit commitment problem, a heuristic technique is used to relax the inter-temporal ramping constraints of the generating units. Numerical results from a case study based on the IEEE one-area reliability test system (RTS) demonstrate the usefulness of the proposed approach.
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| 9. |
- Nasri, S, et al.
(författare)
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Hydrological processes in macrocatchment water harvesting in the arid region of Tunisia: the traditional system of tabias
- 2004
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Ingår i: Hydrological Sciences Journal. - 0262-6667. ; 49:2, s. 261-272
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Tidskriftsartikel (refereegranskat)abstract
- In arid Tunisia, a tabia system is a traditional macrocatchment water harvesting system. It consists of a runoff area, which occupies two thirds of the slope arid is traditionally used for grazing; and one to five cropped plots within U-shaped soil banks arranged in a cascade in the third downstream area. These "run-on" areas accumulate and store the occasional runoff. Each soil bank is constructed with a discharge weir that allows modification of the flooded area and discharge of excess water towards downstream plots. Such a harvesting system, located in an area with 140 turn annual rainfall, was instrumented during four hydrological years (1995-1999) and 45 rainfall events were recorded. Eleven of these events gave a measurable inflow to at least one of the four plots. The observations showed that the traditional tabia system reduced total surface runoff from the catchment to essentially zero. The harvesting system significantly reduced peaks of surface runoff within the catchment, which also reduced erosion hazards. The cultivated area of about 5% of the total catchment could be supplied by a harvested water amount corresponding to about seven times the amount of each rainfall event larger than 20 mm.
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| 10. |
- Nasri, S, et al.
(författare)
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Use of a geomorphological transfer function to model design floods in small hillside catchments in semiarid Tunisia
- 2004
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 287:1-4, s. 197-213
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Tidskriftsartikel (refereegranskat)abstract
- In the beginning of the 1990s, the Tunisian Ministry of Agriculture launched an ambitious program for constructing small hillside reservoirs in the northern and-central region of the country. At present, more than 720 reservoirs have been created. They consist of small compacted earth dams supplied with a, horizontal overflow weir. Due to lack of hydrological data and the area's extreme floods, however, it is very difficult to design the overflow weirs. Also, catchments are very sensitive to erosion and the reservoirs are rapidly silted up. Consequently, prediction of flood volumes for important rainfall events becomes crucial. Few hydrological observations, however, exist for the catchment areas. For this purpose a geomorphological model methodology is presented to predict shape and volume of hydrographs for important floods. This model is built around a production function that defines the net storm rainfall (portion of rainfall during a storm which reaches a stream channel as direct runoff) from the total rainfall (observed rainfall in the catchment) and a transfer function based on the most complete possible definition of the surface drainage system. Observed rainfall during 5-min time steps was used in the model. The model runoff generation is based on surface drainage characteristics which can be easily extracted from maps. The model was applied to two representative experimental catchments in central Tunisia. The conceptual rainfall-runoff model based on surface topography and drainage. network was seen to reproduce observed runoff satisfactory. The calibrated model was used to estimate runoff from 5, 10, 20, and 50 year rainfall return periods regarding runoff volume, maximum runoff, as well as the general shape of the runoff hydrograph. Practical conclusions to design hill reservoirs and to extrapolate results using this model methodology for ungauged small catchments in semiarid Tunisia are made. (C) 2004 Elsevier B.V. All rights reserved.
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| 11. |
- Olsson, J, et al.
(författare)
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Multiscaling analysis and random cascade modeling of dye infiltration
- 2002
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Ingår i: Water Resources Research. - 0043-1397. ; 38:11
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Tidskriftsartikel (refereegranskat)abstract
- [1] We aimed at investigating whether the spatial variability of infiltration in field soils, as visualized through dye infiltration experiments, is characterized by a multiscaling behavior. Digitized high-resolution dye images from three sites in an experimental catchment in Tunisia were analyzed using three indicators of scaling: empirical probability distribution functions, power spectra, and raw statistical moments. The two former indicators suggested a general scaling behavior of the data, which through the moments' analysis was found to be of multiscaling type. Random cascade processes are frequently used to model multiscaling processes, and we fitted the "universal multifractal'' (UM) model of Schertzer and Lovejoy [1987] to our data. The UM model closely reproduced the empirical K(q) functions, and simulated fields reproduced key features in the observed ones. The results indicate that multiscaling random cascade modeling is useful for statistically describing flow processes and solute transport under field conditions.
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| 12. |
- Öhrström, Pernilla, et al.
(författare)
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Field-scale variation of preferential flow as indicated from dye coverage
- 2002
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Ingår i: Journal of Hydrology. - 0022-1694. ; 257:1-4, s. 164-173
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Tidskriftsartikel (refereegranskat)abstract
- Field investigations were performed in semiarid Tunisia to investigate spatial variability of preferential pathways in catchment- and plot-scales. A rainfall simulator with dye was used to simulate effects of a 20-year rainstorm. After infiltration into six one-meter square plots, vertical 2.5-cm thick soil sections were excavated, and dye penetrations were photographed, The results show that different catchment physiographic areas (nose, slope, and hollow) displayed significantly different responses to the infiltrating dye. Nose and hollow areas exhibited larger susceptibility to preferential flow. Here. infiltrated dye was transported to greater depths. Slopes had fewer deep cracks and fissures. The dye distribution within each plot was also investigated. The variability of the dye patterns increased with scale. Cross-correlations and power spectrum analyses indicated that the preferential pathways were randomly distributed. The power-law behavior of the dye patterns' spectral density suggested scale invariance and the possibility of random cascade modeling. (C) 2002 Elsevier Science B.V. All rights reserved.
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