| 1. |
- Alessandro, B., et al.
(author)
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Vector boson scattering : Recent experimental and theory developments
- 2018
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In: Reviews in Physics. - : Elsevier BV. - 2405-4283. ; 3, s. 44-63
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Journal article (peer-reviewed)abstract
- This document summarises the talks and discussions happened during the VBSCan Split17 workshop, the first general meeting of the VBSCan COST Action network. This collaboration is aiming at a consistent and coordinated study of vector-boson scattering from the phenomenological and experimental point of view, for the best exploitation of the data that will be delivered by existing and future particle colliders.
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| 2. |
- Jain, Vishal, 1989-, et al.
(author)
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Processing and Characterization of Nanowire Arrays for Photodetectors
- 2015
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In: Nano-Structures for Optics and Photonics. - Dordrecht : Springer. - 9789401791427 - 9789401791328 - 9789401791335 ; , s. 511-512
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Conference paper (peer-reviewed)abstract
- We present a fabrication scheme of contacting arrays of vertically standing nanowires (NW) for LEDs (Duan et al. Nature 409:66–69, 2001), photodetectors (Wang et al. Science (NY) 293:1455–1457, 2001) or solar cell applications (Wallentin et al. Science (NY) 339:1057–1060, 2013). Samples were prepared by depositing Au films using nano-imprint lithography (Må rtensson et al. Nano Lett 4:699–702, 2004) which are used as catalysts for NW growth in a low-pressure metal organic vapour phase epitaxy system where III-V precursors and dopant gases are flown at elevated temperatures which lead to the formation of NWs with different segments (Borgström et al. Nano Res 3:264–270, 2010). An insulating SiO2 layer is then deposited and etched from the top segments of the NWs followed by sputtering of a transparent top conducting oxide and opening up 1 × 1 mm2 device areas through a UV lithography step and etching of the top contact from non-device areas. A second UV lithography step was subsequently carried out to open up smaller windows on the ITO squares for bond pad definition, followed by metallization and lift-off; and the substrate is used as back contact. We also report on the electrical and optical properties of near-infrared p+−i−n+ photodetectors/solar cells based on square millimeter ensembles of InP nanowires grown on InP substrates. The study includes a sample series where the p +-segment length was varied between 0 and 250 nm, as well as solar cell samples with 9.3 % efficiency with similar design. The NWs have a complex modulated crystal structure of alternating wurtzite and zincblende segments, a polytypism that depends on dopant type. The electrical data for all samples display excellent rectifying behavior with an ideality factor of about 2 at 300 K. From spectrally resolved photocurrent measurements, we conclude that the photocurrent generation process depends strongly on the p +-segment length. Without p +-segment in the NWs, photogenerated carriers funneled from the substrate into the NWs contribute significantly to the photocurrent. Adding a p +-segment shifts the depletion region up into the i-region of the NWs reducing the substrate contribution to photocurrent while strongly improving the collections of carriers generated in the NWs, in agreement with theoretical modeling (Fig. 48.1). © Springer Science+Business Media Dordrecht 2015.
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| 3. |
- Karmin, Monika, et al.
(author)
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A recent bottleneck of Y chromosome diversity coincides with a global change in culture.
- 2015
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In: Genome Research. - : Cold Spring Harbor Laboratory. - 1088-9051 .- 1549-5469. ; 25:4
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Journal article (peer-reviewed)abstract
- It is commonly thought that human genetic diversity in non-African populations was shaped primarily by an out-of-Africa dispersal 50-100 thousand yr ago (kya). Here, we present a study of 456 geographically diverse high-coverage Y chromosome sequences, including 299 newly reported samples. Applying ancient DNA calibration, we date the Y-chromosomal most recent common ancestor (MRCA) in Africa at 254 (95% CI 192-307) kya and detect a cluster of major non-African founder haplogroups in a narrow time interval at 47-52 kya, consistent with a rapid initial colonization model of Eurasia and Oceania after the out-of-Africa bottleneck. In contrast to demographic reconstructions based on mtDNA, we infer a second strong bottleneck in Y-chromosome lineages dating to the last 10 ky. We hypothesize that this bottleneck is caused by cultural changes affecting variance of reproductive success among males.
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| 4. |
- Liberman, M. A., et al.
(author)
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Numerical Simulation of Deflagration-to-Detonation Transition : the Role of Hydrodynamic Instability
- 2006
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In: International Journal of Transport Phenomena. - 1028-6578. ; 8, s. 253-277
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Journal article (peer-reviewed)abstract
- The role of the flame folding, induced by the classical Darrieus-Landau instability, on the transition from deflagration to detonation is studied by numerical simulations of premixed gas combustion spreading from the closed end of a semi-infinite, smooth-walled channel. It is found that in sufficiently wide channels the Darrieus-Landau instability may invoke nucleation of hot spots within the folds of the developing wrinkled flame, triggering an abrupt transition from deflagrative to detonative combustion. The mechanism of the transition is the temperature increase due to the influx of heat from the folded reaction zone, followed by autoignition. The transition occurs when the pressure elevation at the accelerating reaction front becomes high enough to produce a shock capable of supporting detonation. This requires the fold to be sufficiently narrow and deep. The influence of adhesive and rough walls on the transition is discussed.
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| 5. |
- Liberman, M. A., et al.
(author)
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Numerical studies of curved stationary flames in wide tubes
- 2003
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In: Combustion theory and modelling. - : Informa UK Limited. - 1364-7830 .- 1741-3559. ; 7:4, s. 653-676
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Journal article (peer-reviewed)abstract
- The nonlinear problem of the propagation of curved stationary flames in tubes of different widths is studied by means of direct numerical simulation of the complete system of hydrodynamic equations including thermal conduction, viscosity, fuel diffusion and chemical kinetics. While only a planar flame can propagate in a narrow tube of width smaller than half of the cut-off wavelength determined by the linear theory of the hydrodynamic instability of a flame front, in wider tubes stationary curved flames propagate with velocities considerably larger than the corresponding velocity of a planar flame. It is shown that only simple 'single-hump' slanted stationary flames are possible in wide tubes, and 'multi-hump' flames are possible in wide tubes only as a nonstationary mode of flame propagation. The stability limits of curved stationary flames in wider tubes and the secondary Landau-Darrieus instability are investigated. The dependence of the velocity of the stationary flame on the tube width is studied. The analytical theory describes the flame reasonably well when the tube width does not exceed some critical value. The dynamics of the flame in wider tubes is shown to be governed by a large-scale stability mechanism resulting in a highly slanted flame front. In wide tubes, the skirt of the slanted flame remains smooth with the length of the skirt and the flame velocity increasing progressively with the increase of the tube width above the second critical value. Results of the analytical theory and numerical simulations are discussed and compared with the experimental data for laminar flames in wide tubes.
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| 6. |
- Liberman, M. A., et al.
(author)
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Self-acceleration and fractal structure of outward freely propagating flames
- 2004
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In: Physics of fluids. - : AIP Publishing. - 1070-6631 .- 1089-7666. ; 16:7, s. 2476-2482
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Journal article (peer-reviewed)abstract
- Flame acceleration associated with development of the Landau-Darrieus hydrodynamic instability is studied by means of direct numerical simulation of the Navier-Stokes equations including chemical kinetics in the form of the Arrhenius law. The fractal excess for radially expanding flames in cylindrical geometry is evaluated. Two-dimensional (2-D) simulation of radially expanding flames in cylindrical geometry displays a radial growth with 1.25 power law temporal behavior after some transient time. It is shown that the fractal excess for 2-D geometry obtained in the numerical simulation is in good agreement with theoretical predictions. The difference in fractal dimension between 2-D cylidrical and three-dimensional spherical radially expanding flames is outlined. Extrapolation of the obtained results for the case of spherical expanding flames gives a radial growth power law that is consistent with temporal behavior obtained in the survey of experimental data.
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| 7. |
- Rutkowski, Lucile, et al.
(author)
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Detection of OH and H2O in an Atmospheric Flame by Near-Infrared Optical Frequency Comb Spectroscopy
- 2017
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In: 2017 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC). - : IEEE. - 9781509067367
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Conference paper (peer-reviewed)abstract
- Absorption spectroscopy is attractive for combustion diagnostics because it allows in-situ and calibration-free quantification of reactants/products and thermometry. However, spectra measured at atmospheric pressure in the near-infrared telecom range, where laser sources and optical components are readily available, suffer from strong water interference. Cavity-enhanced optical frequency comb spectroscopy (CE-OFCS) is well suited for detection of other species, as it provides broad bandwidth with high signal-to-noise ratio and resolution, and allows de-convolving the spectra hidden among water transitions. Here we report detection of OH in the presence of H2O in an atmospheric premixed methane/air flat flame by CE-OFCS at 1.57 μm. We demonstrate a new water line list that is more accurate than HITEMP [1] and we isolate the OH lines by dividing spectra taken at different heights above the burner (HABs) to retrieve OH concentration and flame temperature.
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| 8. |
- Rutkowski, Lucile, et al.
(author)
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Measurement of H2O and OH in a Flame by Optical Frequency Comb Spectroscopy
- 2016
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In: Proceedings Conference on Lasers and Electro-Optics. - Washington, D.C. : IEEE. - 9781943580118
-
Conference paper (peer-reviewed)abstract
- We measure broadband H2O and OH spectra in a flame using near-infrared cavity-enhanced Fourier transform optical frequency comb spectroscopy, we retrieve temperature and OH concentration, and compare water spectra to an improved line list.
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