413 research outputs found
Systemic risk and severe economic downturns: A targeted and sparse analysis
No full textRecent studies indicate that systemic risk has predictive power over severe economic downturns. We propose a novel methodology that employs sparsity and targeting approaches to optimally select and combine systemic risk measures to forecast the tail of a given economic variable. Out-of-sample analysis shows that the optimal combination of systemic risk metrics may vary over time, forecasting horizons and economic proxies. Moreover, a few systemic risk measures contain all the important information for capturing the relation between systemic risk and real economy; therefore, a fixed and static combination approach may not be optimal, and the flexible parsimonious extension we introduce leads to improvement in forecasting performance
Omega Compatibility: A Meta-analysis
No full textThe Omega performance measure introduced by Keating and Shadwick (An introduction to Omega. AIMA Newsletter, 2002a; J Perform Meas 6(3):59-84, 2002b) is widely used in asset allocation and performance measurement. We contribute to the debates around this measure by focusing on its relation and compatibility with Second-order Stochastic Dominance, introducing two conditions of compatibility: the Non-Strict Dominance Compatibility and the Strict Dominance Compatibility conditions. We show that Omega is compatible with the First-order Stochastic Dominance criterion when using the Non-Strict Dominance Compatibility condition (as already shown), but also in the sense of the Strict Dominance Compatibility condition. We also prove again that Omega is compatible with Second-order Stochastic Dominance when using the Non-Strict Dominance Compatibility condition, but only under some conditions on the threshold used in the computation of the Omega measure, as usual. However, we finally also show that Omega is not compatible (i.e. incompatible) with Second-order Stochastic Dominance criterion when using the Strict Dominance Compatibility condition. We further provide a critical meta-analysis that separates good from approximate statements when comparing the views and results provided in many articles on the topic and point out that the use of Omega in asset selection and optimal asset allocation may entail real computational economics issues and may lead to unreasonable financial decisions. Finally, trying to avoid further disputes, ill-posed optimization procedures, and ultimately incorrect economic decisions in computational financial applications, we recall the main potential drawbacks of Omega that, in our opinion, mainly lies in its incompatibility with the Second-order Stochastic Dominance criterion under the Strict Dominance Compatibility condition
Mesoscopic simulations of shock-to-detonation transition in reactive liquid high explosive
No full textInternational audienceAn extension of the model described in a previous work (see Maillet J. B. et al., EPL, 78 (2007) 68001) based on Dissipative Particle Dynamics is presented and applied to a liquid high explosive (HE), with thermodynamic properties mimicking those of liquid nitromethane. Large scale nonequilibrium simulations of reacting liquid HE with model kinetic under sustained shock conditions allow a better understanding of the shock-to-detonation transition in homogeneous explosives. Moreover, the propagation of the reactive wave appears discontinuous since ignition points in the shocked material can be activated by the compressive waves emitted from the onset of chemical reactions
Jenningsina heddebauti Milhau 1983
No full textJenningsina cf. heddebauti (Milhau, 1983) cf. 1983 b Jenningsina heddebauti nov. sp.; Milhau: 221, 225–226, 228 – 229, pl. 9, figs. 12–19. 2013 Jenningsina cf. heddebauti Milhau; Maillet: 122. cf. 2013 b Jenningsina heddebauti Milhau; Maillet in Maillet et al.: fig. 6 L. cf. 2013 Jenningsina heddebauti Milhau; Casier in Casier & Préat: 488, pl. IV, fig. 10. Material. 3 specimens (1 C, 2 F). Description. Medium-sized elongated carapace, sub-rectangular to bean-shaped and slender posteriorly in lateral view. Overlap of the larger LV over the smaller RV at free margins. Hmax at 1 / 3 anterior; Lmax median; Wmax posterior. Almost straight dorsal margin. Almost straight to slightly concave ventral margin. Convex anterior margin, more arched in its ventral part. Convex posterior margin, more arched in its dorsal part. Anterior part of the carapace higher than the posterior one. Posterior shoulders on each valve more or less marked. Surface ornamented with large reticles, with a pattern that runs more or less along the free margins. In ventral view, possible fine marginal ridules along the line of closure of the valves. Discussion. Although they well remind the morphology of J. heddebauti Milhau, 1983, none of these specimens is complete and well enough preserved to assign them without doubt to this species. Occurrences. Middle Givetian (Candás Fm, mb C), Asturias (Peran-Perlora section).Published as part of Maillet, Sebastien, Milhau, Bruno, Vreulx, Michel & Posada, Luis-Carlos Sánchez De, 2016, Givetian ostracods of the Candás Formation (Asturias, North-western Spain): taxonomy, stratigraphy, palaeoecology, relationship to global events and palaeogeographical implications, pp. 1-78 in Zootaxa 4068 (1) on page 44, DOI: 10.11646/zootaxa.4068.1.1, http://zenodo.org/record/27064
A rapid benchtop NMR method for determination of droplet size distributions in food emulsions
No full textThe determination of water and oil droplet size distributions in food emulsions by low-field NMR has the advantage of a simple and non-perturbing sample preparation. Furthermore, NMR performs very well with respect to precision. The current implementation on most benchtop NMR spectrometers deploys a variation of gradient duration and requires continuous corrections for gradient imbalances, thus making the whole procedure a time-consuming one. By using variation of gradient strength and further stretching the capability of commercial benchtop NMR spectrometers, both water and oil droplet sizes can be measured in a more rapid manner, typically two to three times faster. The measured droplet size distributions are equivalent to those assessed by the current (slow) method, for both O/W and W/O emulsions. Furthermore, the rapid method shows a good performance with respect to precision. In addition, the method is able to determine droplet sizes in samples with much smaller amounts of dispersed phase
Optimal Probabilistic Work Extraction beyond the Free Energy Difference with a Single-Electron Device
No full textWe experimentally realize protocols that allow us to extract work beyond the free energy difference from a single-electron transistor at the single thermodynamic trajectory level. With two carefully designed out-of-equilibrium driving cycles featuring kicks of the control parameter, we demonstrate work extraction up to large fractions of kBT or with probabilities substantially greater than 1/2, despite the zero free energy difference over the cycle. Our results are explained in the framework of nonequilibrium fluctuation relations. We thus show that irreversibility can be used as a resource for optimal work extraction even in the absence of feedback from an external operator
Uchtovia refrathensis Krommelbein 1954
No full textUchtovia refrathensis (Krömmelbein, 1954) (Pl. II: Figs. 9 & 10) 1954 a Sulcella refrathensis nov. sp.; Krömmelbein: 250, pl. 1, fig. 5. 1954 a Cavellina abundans Pokorńy, 1951; Krömmelbein: pl. 2, fig. 13. 1954 a Cavellina sulcelloides nov. sp.; Krömmelbein: pl. 1, fig. 4. 1959 Uchtovia abundans (Pokorńy, 1951); Rozhdestvenskaja: pl. 10, figs. 1–5. 1969 Sulcella refrathensis Krömmelbein; Groos: 53, pl. 9, fig. 2. 1982 Uchtovia ? sp. 1; Milhau: 23, pl. 6, fig. 159. 1983 a Uchtovia refrathensis (Krömmelbein); Milhau: 351. 1983 Uchtovia refrathensis (Krömmelbein); Żbikowska: 45, pl. 10, figs. 3–7. 1993 Uchtovia refrathensis (Krömmelbein); Malec & Racki: 362, 368, 374, 376, text-figs. 4 G–K.? 1993 Uchtovia refrathensis (Krömmelbein); Kasimi: pl. 17, fig. 2. 2009 Uchtovia refrathensis (Krömmelbein); Casier in Casier & Préat: pl. 4, fig. 19. non 2009 Uchtovia sp. A, aff. refrathensis (Krömmelbein); Casier in Casier & Préat: pl. 4, fig. 20. 2010 Uchtovia refrathensis (Krömmelbein); Maillet: 40, pl. 4, fig. 11. non 2011 b Uchtovia refrathensis (Krömmelbein); Casier in Casier et al.: pl. 2, fig. 8. 2013 Uchtovia refrathensis (Krömmelbein); Casier & Maillet in Casier et al.: 254, 264, fig. 9 E. 2013 Uchtovia refrathensis (Krömmelbein); Maillet: 88, pl. XI, figs. 7–9. 2013 b Uchtovia refrathensis (Krömmelbein); Maillet et al.: fig. 8 J. 2013 Uchtovia refrathensis (Krömmelbein); Casier in Casier & Préat: 488, pl. III, fig. 14. Material. 74 specimens (62 C, 7 V, 5 F). Diagnosis. Krömmelbein (1954 a, p. 252). Description. Medium-sized elongated and sub-oval carapace. The larger RV overlaps the LV on whole outline, except on the dorsal margin from ½ to ¾ of Lmax. Hmax at 1 / 3 anterior; Lmax almost median (slightly dorsal); Wmax almost median. Dorsal margin oblique both anteriorly (on 2 / 3) and posteriorly (on 1 / 3). Antero-dorsal long and narrow stragulum. Almost straight ventral margin, slightly concave at mid-length on the largest valve. Dorsal and ventral margins almost parallel (carapace slightly posteriorly slender). Well rounded anterior margin, regularly convex. Well rounded posterior margin, more arched than the anterior one. Anterior part slightly higher than the posterior one. Surface smooth. Shoulder in the posterior part, extending from dorsal to ventral margins and parallel to the posterior margin. Posterior end consequently sharp in dorsal view. Marked “U”-shaped adductorial sulcus at mid-dorsal, slightly oblique towards anterior, extending from the dorsal margin to the centre of valves. Another slighter sulcus in the antero-dorsal part. Discussion. A marked sexual dimorphism has been observed, with heteromorphic carapaces larger, more elongate and flatter than tecnomorphic ones, and with an indistinct shoulder. Occurrence. Upper Givetian to Lower Frasnian (Fromelennes Fm, Fort Hulobiet Mb, and Nismes Fm), Ardenne (Flohimont, Nismes, Sourd d’Ave, Cul d’Houille and Aisne sections), Upper Givetian to Lower Frasnian (Candás Fm, mbs C and D), Asturias (Peran-Perlora section); Middle Devonian, Eifel, Ruhr and Poland; Upper Devonian, Russia.Published as part of Maillet, Sebastien, Milhau, Bruno, Vreulx, Michel & Posada, Luis-Carlos Sánchez De, 2016, Givetian ostracods of the Candás Formation (Asturias, North-western Spain): taxonomy, stratigraphy, palaeoecology, relationship to global events and palaeogeographical implications, pp. 1-78 in Zootaxa 4068 (1) on pages 30-31, DOI: 10.11646/zootaxa.4068.1.1, http://zenodo.org/record/27064
Givetian ostracods of the Candás formation (Asturias, North-western Spain): Taxonomy, stratigraphy, palaeoecology, relationship to global events and palaeogeographical implications
No full textFIGURE 1. Location maps of the studied area. A. Devonian deposits cropping out in the Cantabrian Zone (adapted from García-Alcalde et al. 2012); B. Simplified geological map of the Luanco-Candás area showing the Naranco, the Candás and the Piñeres Fms (modified from García-López et al. 2002), with location of the Peran-Perlora and Carranques sections; C. Detailed location map of the Peran-Perlora section (adapted from García-López et al. 2002); D. Detailed location map of the Carranques section (adapted from Fernández et al. 1996).Published as part of Maillet, Sebastien, Milhau, Bruno, Vreulx, Michel & Posada, Luis-Carlos Sánchez De, 2016, Givetian ostracods of the Candás Formation (Asturias, North-western Spain): taxonomy, stratigraphy, palaeoecology, relationship to global events and palaeogeographical implications, pp. 1-78 in Zootaxa 4068 (1) on page 7, DOI: 10.11646/zootaxa.4068.1.1, http://zenodo.org/record/27064
Jenningsina paffrathensis Krommelbein 1954
No full textJenningsina paffrathensis Krömmelbein, 1954 (Pl. III: Fig. 2) 1954 a Jenningsina paffrathensis nov. sp.; Krömmelbein: 255–256, pl. 2, fig. 10. 1964 Jenningsina sp. F; Magne: pl. 24, figs. 175–177. ? 1964 Jenningsina cf. sp. F; Magne: pl. 23, figs. 144–145, pl. 24, figs. 172–174.? 1964 Jenningsina sp. G 2; Magne: pl. 22, fig. 132. 1982 Jenningsina sp. G 2 Magne; Milhau: 22, pl. 5, fig. 118. 1983 a Jenningsina lethiersi Becker; Milhau: 351, pl. 1, fig. 2. 1983 a Jenningsina sp. indet.; Milhau: 353. 1985 Jenningsina paffrathensis Krömmelbein; Coen: 20, pl. 6, fig. 7.? 1988 Jenningsina sp. G 2 Magne; Milhau: 486, pl. 56, fig. 21. 2009 Jenningsina paffrathensis Krömmelbein; Casier in Casier & Préat: pl. 5, fig. 13. 2010 Jenningsina paffrathensis Krömmelbein; Maillet: 40, pl. 2, fig. 29. 2013 Jenningsina paffrathensis Krömmelbein; Maillet: 120, pl. XV, figs. 22–23. 2013 b Jenningsina paffrathensis Krömmelbein; Maillet et al., fig. 6 M. Material. 64 specimens (43 C, 10 V, 11 F). Diagnosis. Krömmelbein (1954 a, p. 255). Description. Medium-sized elongated carapace, bean-shaped in lateral view. Very slight overlap of the larger LV over the RV dorsally. Hmax at 1 / 4 anterior; Lmax at 2 / 5 ventral; Wmax median. Dorsal margin oblique posteriorly to Hmax point. Almost straight (very slightly concave) ventral margin. Ventral and dorsal margins converging posteriorly. Well rounded anterior margin, regularly convex in its dorsal part, more arched in its ventral part. Well rounded posterior margin, oblique anteriorly from dorsal to ventral part. Free margins of the carapace flattened. Anterior part of the carapace higher than posterior one. Whole surface reticulated. Reticulation globally orientated longitudinally, with fine reticles diverging posteriorly from the median longitudinal line of the valves. Marked posterior vertical shoulder, with more nodular dorsal and ventral extremities, longing the posterior margin. Discussion. This species may be a synonym of Jenningsina lethiersi Becker, 1971 (ecomorphism?), whose morphology of carapace as well as the general pattern of reticulation are identical to J. paffrathensis, with the exception of the size of the reticules. Moreover, the two species are frequently associated within a same stratigraphical level (e.g. Maillet 2013 and Casier et al. 2013 for the Ardenne; this paper for the Asturias). Occurrences. Upper Givetian to Lower Frasnian (Fromelennes Fm, Fort Hulobiet Mb, and Nismes and Presles Fms), Ardenne (Flohimont, Cul d’Houille, Aisemont, Nismes and Aisne sections), Upper Givetian to Lower Frasnian (Candás Fm, mbs C and D), Asturias (Peran-Perlora and Carranques sections); Upper Givetian, Eifel and Boulonnais.Published as part of Maillet, Sebastien, Milhau, Bruno, Vreulx, Michel & Posada, Luis-Carlos Sánchez De, 2016, Givetian ostracods of the Candás Formation (Asturias, North-western Spain): taxonomy, stratigraphy, palaeoecology, relationship to global events and palaeogeographical implications, pp. 1-78 in Zootaxa 4068 (1) on page 41, DOI: 10.11646/zootaxa.4068.1.1, http://zenodo.org/record/27064
Démons parfumés en Étrurie, de l’époque orientalisante à l’époque hellénistique
No full textQuand on parle de démons en Étrurie, on pense à ces figures suggestives (Fig. 1, a et b) qui ornent les parois des tombes, des céramiques, des urnes et des sarcophages aux IVe et IIIe siècles av. J.-C. Figure 1 : Démons étrusques et médiévauxa) Tuchulcha. Tarquinia, tombe de l’Ogre II ; b) Charun. Tarquinia, tombe de l’Ogre ; c) scène de l’Apocalypse. Cambridge ; d) démon avec maillet. Stratford-sur-Avon. Ces créatures effrayantes qui ont donné lieu à plusieurs études importantes sont tellem..
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