3,690 research outputs found

    A Regular Demand System with Commodity-Specific Demographic Effects

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    Regular consumer demand systems almost invariably employ specifications that involve common functional forms in all equations. When applications involve crosssectional data it is often the case that demographic effects are important. However it is plausible that demographic effects are commodity-specific. In this case, there may be a loss of efficiency if a common functional form across commodities is imposed artificially by entering redundant explanators in demand equations for which specific demographic influences are unwarranted. This paper explores an approach to specifying a complete system of demand equations which is fully regular but which nevertheless allows for commodity-specific variation in the functional form of the demand equations

    Using discrete Darboux polynomials to detect and determine preserved measures and integrals of rational maps

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    In this Letter we propose a systematic approach for detecting and calculating preserved measures and integrals of a rational map. The approach is based on the use of cofactors and Discrete Darboux Polynomials and relies on the use of symbolic algebra tools. Given sufficient computing power, all rational preserved integrals can be found. We show, in two examples, how to use this method to detect and determine preserved measures and integrals of the considered rational maps.Comment: 8 pages, 1 Figur

    The 25 November 1988 Saguenay, Quebec, Earthquake: Source Parameters and the Attenuation of Strong Ground Motion

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    The Saguenay earthquake of 25 November 1988 occurred close to the southern margin of the Saguenay Graben in southern Quebec. It was caused by almost purely dip-slip faulting centered at a depth of 26 km with a P axis oriented northeast-southwest. This faulting mechanism is similar to those of the larger historical earthquakes in eastern North America, but the focal depth is substantially greater than all but one of these events. The seismic moment estimated from regional PnI waves and teleseismic long-period body waves is 5 × 10^(24) dyne-cm., corresponding to a moment magnitude of 5.8. The source duration of the earthquake is estimated to be 1.8 sec, corresponding to a stress drop of 160 bars, which is not significantly higher than the average stress drop of 120 bars estimated from previous large earthquakes in eastern North America. In order to simultaneously match the recorded ground motion amplitudes of strong-motion acceleration, strong-motion velocity, and teleseismic short-period and long-period body waves, it is necessary to use a source function having a complex shape that implies the presence of asperities and larger local stress drops. The large set of strong-motion recordings of the Saguenay earthquake has been used to validate a procedure for estimating strong ground motion attenuation based on a simple wave propagation model. The most important feature of the recorded strong motions is that their peak amplitudes do not decay significantly with distance inside 120 km, but then decay abruptly beyond 120 km. Profiles of recorded accelerograms with absolute times indicate that at distances beyond 64 km the peak ground motions are due to strong postcritical reflections from velocity gradients in the lower crust. The principal shear-wave arrivals and the variation of their peak amplitudes with distance were reproduced in synthetic seismograms generated using a regional crustal structure model. The critical distances for the postcritical reflections were short because of the deep focal depth of the event, causing the elevation of ground motion amplitudes out to 120 km. Similar studies of earthquakes in other regions of eastern North America indicate that the strength of the postcritical reflections, and the distance ranges over which they are dominant, are controlled by the focal depth and crustal structure. Regional variations in crustal structure thus give rise to predictable regional variations in strong ground motion attenuation

    The morphogenesis of fast growth in plants

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    - Growth rate represents a fundamental axis of life history variation. Faster growth associated with C4 photosynthesis and annual life history has evolved multiple times, and the resulting diversity in growth is typically explained via resource acquisition and allocation. However, the underlying changes in morphogenesis remain unknown. - We conducted a phylogenetic comparative experiment with 74 grass species, conceptualising morphogenesis as the branching and growth of repeating modules. We aimed to establish whether faster growth in C4 and annual grasses, compared with C3 and perennial grasses, came from the faster growth of individual modules or higher rates of module initiation. - Morphogenesis produces fast growth in different ways in grasses using C4 and C3 photosynthesis, and in annual compared with perennial species. C4 grasses grow faster than C3 species through a greater enlargement of shoot modules and quicker secondary branching of roots. However, leaf initiation is slower and there is no change in shoot branching. Conversely, faster growth in annuals than perennials is achieved through greater branching and enlargement of shoots, and possibly faster root branching. - The morphogenesis of fast growth depends on ecological context, with C4 grasses tending to promote resource capture under competition, and annuals enhancing branching to increase reproductive potential

    The time of the Roma in times of crisis: Where has European neoliberal capitalism failed?

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    This paper argues that the economic and financial crisis that has ensnared Europe from the late 2000s has been instrumental in reshaping employment and social relations in a detrimental way for the majority of the European people. It argues that the crisis has exacerbated the socio-economic position of most Roma people, immigrants as well as of other vulnerable groups. This development is approached here as an outcome of the widening structural inequalities that underpin the crisis within an increasingly neoliberalised Europe. Through recent policy developments and public discourses from a number of European countries I show how rising inequalities nurture racialised social tensions. My account draws on classic and contemporary theoretical propositions that have been propounded about the nature of capitalism, its contemporary re-articulation as well as its ramification for the future of Europe

    An assessment of the strength of knots and splices used as eye terminations in a sailing environment

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    Research into knots, splices and other methods of forming an eye termination has been limited, despite the fact that they are essential and strongly affect the performance of a rope. The aim of this study was to carry out a comprehensive initial assessment of the breaking strength of eye terminations commonly used in a sailing environment, thereby providing direction for further work in the field. Supports for use in a regular tensile testing machine were specially developed to allow individual testing of each sample and a realistic spread of statistical data to be obtained. Over 180 break tests were carried out on four knots (the bowline, double bowline, figure-of-eight loop and perfection loop) and two splices (three-strand eye splice and braid-on-braid splice). The factors affecting their strength were investigated. A statistical approach to the analysis of the results was adopted. The type of knot was found to have a significant effect on the strength. This same effect was seen in both types of rope construction (three-strand and braid-on-braid). Conclusions were also drawn as to the effect of splice length, eye size, manufacturer and rope diameter on the breaking strength of splices. Areas of development and further investigation were identified

    Aircraft study of the impact of lake-breeze circulations on trace gases and particles during BAQS-Met 2007

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    High time-resolved aircraft data, concurrent surface measurements and air quality model simulations were explored to diagnose the processes influencing aerosol chemistry under the influence of lake-breeze circulations in a polluted region of southwestern Ontario, Canada. The analysis was based upon horizontal aircraft transects conducted at multiple altitudes across an entire lake-breeze circulation. Air mass boundaries due to lake-breeze fronts were identified in the aircraft meteorological and chemical data, which were consistent with the frontal locations determined from surface analyses. Observations and modelling support the interpretation of a lake-breeze circulation where pollutants were lofted at a lake-breeze front, transported in the synoptic flow, caught in a downdraft over the lake, and then confined by onshore flow. The detailed analysis led to the development of conceptual models that summarize the complex 3-D circulation patterns and their interaction with the synoptic flow. The identified air mass boundaries, the interpretation of the lake-breeze circulation, and the air parcel circulation time in the lake-breeze circulation (3.0 to 5.0 h) enabled formation rates of organic aerosol (OA/ΔCO) and SO<sub>4</sub><sup>2−</sup> to be determined. The formation rate for OA (relative to excess CO in ppmv) was found to be 11.6–19.4 μg m<sup>−3</sup> ppmv<sup>−1</sup> h<sup>−1</sup> and the SO<sub>4</sub><sup>2−</sup> formation rate was 5.0–8.8% h<sup>−1</sup>. The formation rates are enhanced relative to regional background rates implying that lake-breeze circulations are an important dynamic in the formation of SO<sub>4</sub><sup>2−</sup> and secondary organic aerosol. The presence of cumulus clouds associated with the lake-breeze fronts suggests that these enhancements could be due to cloud processes. Additionally, the effective confinement of pollutants along the shoreline may have limited pollutant dilution leading to elevated oxidant concentrations
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