| 1. |
- Feugnet, G., et al.
(författare)
-
Improved laser-induced fluorescence method for bio-attack early warning detection system
- 2008
-
Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE.
-
Konferensbidrag (refereegranskat)abstract
- Laser Induced Fluorescence (LIF) could permit fast early warning systems either for point or standoff detection if a reliable classification of warfare biological agents versus biological or non-biological fluorescing background can be achieved. In order to improve LIF discrimination capability, a new system is described in which the fluorescence pattern is enriched by the use of multiple wavelength delayed excitation while usual spectral fluorescence analysis is extended to time domain to use both aspects as criteria for classification. General considerations and guidelines for the system design are given as well as results showing good discrimination between background and simulants.
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Blumer, P., et al.
(författare)
-
Positron accumulation in the GBAR experiment
- 2022
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 1040
-
Tidskriftsartikel (refereegranskat)abstract
- We present a description of the GBAR positron (e+) trapping apparatus, which consists of a three stage Buffer Gas Trap (BGT) followed by a High Field Penning Trap (HFT), and discuss its performance. The overall goal of the GBAR experiment is to measure the acceleration of the neutral antihydrogen (H¯) atom in the terrestrial gravitational field by neutralising a positive antihydrogen ion (H¯+), which has been cooled to a low temperature, and observing the subsequent H¯ annihilation following free fall. To produce one H¯+ ion, about 1010 positrons, efficiently converted into positronium (Ps), together with about 107 antiprotons (p¯), are required. The positrons, produced from an electron linac-based system, are accumulated first in the BGT whereafter they are stacked in the ultra-high vacuum HFT, where we have been able to trap 1.4(2) × 109 positrons in 1100 s.
|
|
| 5. |
- Charlton, M., et al.
(författare)
-
Positron production using a 9 MeV electron linac for the GBAR experiment
- 2021
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 985
-
Tidskriftsartikel (refereegranskat)abstract
- For the GBAR (Gravitational Behaviour of Antihydrogen at Rest) experiment at CERN's Antiproton Decelerator (AD) facility we have constructed a source of slow positrons, which uses a low-energy electron linear accelerator (linac). The driver linac produces electrons of 9 MeV kinetic energy that create positrons from bremsstrahlung-induced pair production. Staying below 10 MeV ensures no persistent radioactive activation in the target zone and that the radiation level outside the biological shield is safe for public access. An annealed tungsten-mesh assembly placed directly behind the target acts as a positron moderator. The system produces 5 x 10(7) slow positrons per second, a performance demonstrating that a low-energy electron linac is a superior choice over positron-emitting radioactive sources for high positron flux.
|
|
| 6. |
|
|
| 7. |
- Husson, A., et al.
(författare)
-
A pulsed high-voltage decelerator system to deliver low-energy antiprotons
- 2021
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 1002
-
Tidskriftsartikel (refereegranskat)abstract
- The GBAR (Gravitational Behavior of Antihydrogen at Rest) experiment at CERN requires efficient deceleration of 100 keV antiprotons provided by the new ELENA synchrotron ring to synthesize antihydrogen. This is accomplished using electrostatic deceleration optics and a drift tube that is designed to switch from -99 kV to ground when the antiproton bunch is inside – essentially a charged particle “elevator” – producing a 1 keV pulse. We describe the simulation, design, construction and successful testing of the decelerator device at -92 kV on-line with antiprotons from ELENA.
|
|
| 8. |
- Kim, B. H., et al.
(författare)
-
Development of a PbWO4 Detector for Single-Shot Positron Annihilation Lifetime Spectroscopy at the GBAR Experiment
- 2020
-
Ingår i: Acta Physica Polonica. A. - 0587-4246 .- 1898-794X. ; 137:2, s. 122-125
-
Tidskriftsartikel (refereegranskat)abstract
- We have developed a PbWO4 (PWO) detector with a large dynamic range to measure the intensity of a positron beam and the absolute density of the ortho-positronium (o-Ps) cloud it creates. A simulation study shows that a setup based on such detectors may be used to determine the angular distribution of the emission and reflection of o-Ps to reduce part of the uncertainties of the measurement. These will allow to improve the precision in the measurement of the cross-section for the (anti)hydrogen formation by (anti)proton-positronium charge exchange and to optimize the yield of antihydrogen ion which is an essential parameter in the GBAR experiment.
|
|
| 9. |
- Niang, S., et al.
(författare)
-
Accumulation of Positrons from a LINAC Based Source
- 2020
-
Ingår i: Acta Physica Polonica. A. - 0587-4246 .- 1898-794X. ; 137:2, s. 164-166
-
Tidskriftsartikel (refereegranskat)abstract
- The GBAR experiment aims to measure the gravitational acceleration of antihydrogen (H) over bar. It will use (H) over bar (+) ions formed by the interaction of antiprotons with a dense positronium cloud, which will require about 1010 positrons to produce one (H) over bar (+). We present the first results on the positron accumulation, reaching 3.8 +/- 0.4x10(8) e(+) collected in 560 s.
|
|
| 10. |
|
|
| 11. |
|
|
| 12. |
|
|
| 13. |
|
|
| 14. |
|
|
| 15. |
- Abellán, F. J., et al.
(författare)
-
Very Deep inside the SN 1987A Core Ejecta : Molecular Structures Seen in 3D
- 2017
-
Ingår i: Astrophysical Journal Letters. - : Institute of Physics Publishing. - 2041-8205 .- 2041-8213. ; 842:2
-
Tidskriftsartikel (refereegranskat)abstract
- Most massive stars end their lives in core-collapse supernova explosions and enrich the interstellar medium with explosively nucleosynthesized elements. Following core collapse, the explosion is subject to instabilities as the shock propagates outward through the progenitor star. Observations of the composition and structure of the innermost regions of a core-collapse supernova provide a direct probe of the instabilities and nucleosynthetic products. SN 1987A in the Large Magellanic Cloud is one of very few supernovae for which the inner ejecta can be spatially resolved but are not yet strongly affected by interaction with the surroundings. Our observations of SN 1987A with the Atacama Large Millimeter/submillimeter Array are of the highest resolution to date and reveal the detailed morphology of cold molecular gas in the innermost regions of the remnant. The 3D distributions of carbon and silicon monoxide (CO and SiO) emission differ, but both have a central deficit, or torus-like distribution, possibly a result of radioactive heating during the first weeks ("nickel heating"). The size scales of the clumpy distribution are compared quantitatively to models, demonstrating how progenitor and explosion physics can be constrained.
|
|
| 16. |
|
|
| 17. |
- Grigoras, K., et al.
(författare)
-
Qubit-Compatible Substrates With Superconducting Through-Silicon Vias
- 2022
-
Ingår i: IEEE Transactions on Quantum Engineering. - 2689-1808. ; 3
-
Tidskriftsartikel (refereegranskat)abstract
- We fabricate and characterize superconducting through-silicon vias and electrodes suitable for superconducting quantum processors. We measure internal quality factors of a million for test resonators excited at single-photon levels, on chips with superconducting vias used to stitch ground planes on the front and back sides of the chips. This resonator performance is on par with the state of the art for silicon-based planar solutions, despite the presence of vias. Via stitching of ground planes is an important enabling technology for increasing the physical size of quantum processor chips, and is a first step toward more complex quantum devices with three-dimensional integration.
|
|
| 18. |
|
|
| 19. |
- Nachman, James B, et al.
(författare)
-
Outcome of treatment in children with hypodiploid acute lymphoblastic leukemia.
- 2007
-
Ingår i: Blood. - 0006-4971. ; 110:4, s. 1112-5
-
Tidskriftsartikel (refereegranskat)abstract
- One-hundred thirty-nine patients with acute lymphoblastic leukemia (ALL) and hypodiploidy (fewer than 45 chromosomes) were collected from 10 different national ALL study groups and single institutions. Patients were stratified by modal chromosome number into 4 groups: 24 to 29 (N = 46); 33 to 39 (N = 26); 40 to 43 (N = 13); and 44 (N = 54) chromosomes. Nine patients were Philadelphia chromosome (Ph) positive (4 cases: 44 chromosomes; 5 cases: 40-43 chromosomes) and were not considered further. Event-free survival (EFS) and overall survival (OS) of the remaining 130 patients were 38.5% +/- 4.4% and 49.8% +/- 4.2% at 8 years, respectively. There were no significant differences in outcome between patients with 24 to 29, 33 to 39, or 40 to 43 chromosomes. Compared with patients with fewer than 44 chromosomes, patients with 44 chromosomes had a significantly better EFS (P = .01; 8-year estimate, 52.2% vs 30.1%) and OS (P = .017; 69% vs 37.5%). For patients with 44 chromosomes, monosomy 7, the presence of a dicentric chromosome, or both predicted a worse EFS but similar OS. Doubling of the hypodiploid clone occurred in 32 patients (24-29 chromosomes [n = 25] and 33-39 chromosomes [n = 7]) and had no prognostic implication. Children and adolescents with ALL and hypodiploidy with fewer than 44 chromosomes have a poor outcome despite contemporary therapy.
|
|
| 20. |
- O'Connor, Evan, et al.
(författare)
-
Global comparison of core-collapse supernova simulations in spherical symmetry
- 2018
-
Ingår i: Journal of Physics G. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 45:10
-
Tidskriftsartikel (refereegranskat)abstract
- We present a comparison between several simulation codes designed to study the core-collapse supernova mechanism. We pay close attention to controlling the initial conditions and input physics in order to ensure a meaningful and informative comparison. Our goal is three-fold. First, we aim to demonstrate the current level of agreement between various groups studying the corecollapse supernova central engine. Second, we desire to form a strong basis for future simulation codes and methods to compare to. Lastly, we want this work to be a stepping stone for future work exploring more complex simulations of core-collapse supernovae, i.e., simulations in multiple dimensions and simulations with modern neutrino and nuclear physics. We compare the early (first similar to 500 ms after core bounce) spherically-symmetric evolution of a 20 M-circle dot progenitor star from six different core-collapse supernovae codes: 3DnSNeIDS A, AGILE-BOLTZTRAN, FLASH, FORNAX, GR1D, and PROMETHEUS-VERTEX. Given the diversity of neutrino transport and hydrodynamic methods employed, we find excellent agreement in many critical quantities, including the shock radius evolution and the amount of neutrino heating. Our results provide an excellent starting point from which to extend this comparison to higher dimensions and compare the development of hydrodynamic instabilities that are crucial to the supernova explosion mechanism, such as turbulence and convection.
|
|
| 21. |
|
|
| 22. |
|
|
| 23. |
|
|
| 24. |
|
|
| 25. |
|
|
| 26. |
|
|
| 27. |
|
|
| 28. |
- Verbeeck, J., et al.
(författare)
-
JC viral loads in patients with Crohn's disease treated with immunosuppression: can we screen for elevated risk of progressive multifocal leukoencephalopathy?
- 2008
-
Ingår i: Gut. - : BMJ. - 1468-3288 .- 0017-5749. ; 57:10, s. 1393-1397
-
Tidskriftsartikel (refereegranskat)abstract
- Background and aims: Anti-alpha 4 integrin therapy with natalizumab is efficacious in refractory Crohn's disease and in multiple sclerosis, but carries an estimated 1/1000 risk of progressive multifocal leukoencephalopathy (PML) caused by reactivation of latent JC virus infection. Athough anti-alpha 4 integrin therapies are likely to be introduced in the clinic, screening for the risk of PML has not been developed. Methods: We prospectively collected urine, serum, plasma and buffy coats from 125 patients with Crohn's disease, 100 control subjects with gastrointestinal (GI) disease, and 106 healthy volunteers. Four to eight weeks after this first sample collection, we additionally collected a set of urine, serum, plasma and buffy coat samples from the 125 patients with Crohn's disease, and a next set of samples was collected 12-16 weeks after the first collection. JC viral loads were determined with quantitative real-time polymerase chain reaction (PCR), and JC virus seroprevalence with a specific enzyme-linked immunosorbant assay ( ELISA). Results: The overall JC virus seroprevalence was 65%. JC virus DNA copies were detected in the urine from 29-44% of subjects, both those with Crohn's disease and controls. Median viral loads were significantly higher in patients with Crohn's disease who were immunosuppressed (7.36x10(6) copies/ml) compared to healthy volunteers (2.77x10(5) copies/ml) and compared to GI controls (1.8x10(6) copies/ml). Clearance at any time point occurred in 4/107 (3.7%) subjects only. JC viraemia was found in two patients with Crohn's disease. Conclusions: The natural history of JC virus in patients with Crohn's disease is still unknown. Our study results show that JC virus latency and urine viral shedding is frequent in immunosuppressed patients with Crohn's disease. More prospective studies are needed in order to agree on possible recommendations concerning the exclusion of patients with JCV viraemia from anti-alpha 4 integrin treatment.
|
|
| 29. |
|
|
