112,667 research outputs found
Early human occupation and land use changes near the boundary of the Orinoco and the Amazon basins (SE Venezuela): Palynological evidence from El Paují record
No full text20 p., 5 fig.This paper shows a Holocene paleoecological reconstruction based on a peat bog sequence (El Paují, 4°28′N–61°35′ W, 865 m elevation) located in the transition zone between the Gran Sabana (SE Venezuela) savannas and the Amazon rainforests. Paleoecological trends are based on the analysis of pollen and pteridophyte spores, algal and animal remains, fungal spores, and charcoal particles. Thewhole record embraces the last ca. 8000 cal yr BP, and was subdivided into five pollen zones, representing the following vegetation succession: savanna/rainforest mosaic (8250–7715 yr BP), dense rainforests (7715–5040 yr BP), savanna/rainforestmosaic (5040–2690 yr BP), secondary dry forests (2690–1440 yr BP), and peat bog in an open savanna landscape (1440 yr BP–present). These vegetation changes have been attributed to the action of climate and/or land use changes, aswell as the corresponding synergies between them. Fire has been determinant in the landscape evolution. Based on the reconstructed fire and vegetation shifts, a changing land use pattern could have been recognized. Between the early and the mid Holocene (ca. 8.3–5.0 kyr BP), land use practices seemto have been more linked to shifting agriculture in a rainforest landscape – as is usual in Amazon cultures – with medium fire incidence affecting only local forest spots or surrounding savannas. More extensive forest burning was recorded between ca. 5.0 and 2.7 kyr BP, followed by land abandonment and the dominance of drier climates between 2.7 and 1.4 yr BP. The modern indigenous culture, which prefers open environments andmakes extensive use of fire thus preventing forest re-expansion, seem to have established during the last 1500 yr. Therefore, a significant cultural replacement has been proposed for the region, leading to the present-day situation. Changing human activities have been instrumental for ecological evolution in this savanna–rainforest transitional region, as well as for the shaping of modern landscapes.This work was supported by Spanish Ministry of Science and Innovation (projects CGL2006-00974 and CGL2009-07069/BOS to V. Rull, and grant BES-2007-16308 to E. Montoya), the BBVA Foundation (project BIOCON-08-031 to V. Rull), and the Spanish Council for Scientific Research (CSIC, project 200830I258 to V. Rull). Permits to develop the research in Venezuela were provided by the Ministry of Science and Technology (DM/0000013, 5 Jan 2007), and sampling permits were provided by the Ministry of Environment of the same country (no IE-085, 9 Feb 2007).Peer reviewe
Lake Sant Maurici (last 4000 years)
No full textRaw palynological counts of pollen, spores and non-pollen palynomorphs (NPP) utilized in the paper entitled: "Late-Holocene forest resilience in the central Pyrenean highlands as deduced from pollen analysis of Lake Sant Maurici sediments.". This paper has been published in The Holocene (2021, doi 10.1177/09596836211033207)
The Anthropozoic era revisited
No full textThis paper explains in some detail the poorly known proposal of Stoppani (1873) regarding the Anthropozoic era, whose beginning was defined by the first traces of human presence on Earth. This author set the stratigraphical bases for the definition of the ‘human era’, but the proposal had two main weaknesses: the dismissal of biological evolution and the lack of an absolute chronology. Further developments in radiometric/palaeomagnetic dating and the elucidation of the main trends and timing of human evolution have provided the necessary information to update the original Anthropocene proposal in chronological terms, maintaining Stoppani’s original definition and stratigraphic markers. This updated proposal follows the rules of the International Stratigraphic Guide and situates the beginning of the Anthropozoic era at the beginning of the Quaternary, the time at which the first human fossils, corresponding to the first species of the genus Homo and corresponding cultural manifestations have been identified and dated. Therefore, the new Anthropozoic era would follow the Cenozoic era, which ended with the Neogene period. Defined in this way, the Quaternary period and its Pleistocene and Holocene epochs would be situated in the new Anthropozoic era. The main strengths and weaknesses of the updated Anthropozoic version are discussed. It is suggested that the updated Anthropozoic proposal might be fully elaborated to evaluate whether it should be submitted to the International Commission on Stratigraphy and the International Union of Geological Sciences for formalization. © 2020 Lethaia Foundation. Published by John Wiley & Sons LtdPeer reviewe
author-bios-SRD-19-0063.R1 – Supplemental material for The Network Structure of Police Misconduct
No full textSupplemental material, author-bios-SRD-19-0063.R1 for The Network Structure of Police Misconduct by George Wood, Daria Roithmayr and Andrew V. Papachristos in Socius</p
HABIT FORMATION: INPLICATIONS FOR THE WEALTH DISTRIBUTION
No full textIn this paper we study the role of habit formation in shaping the wealth distribution in an otherwise standard heterogeneous agents model economy with idiosyncratic uncertainty. We compare the inplications for precautionary savings and for wealth concentration between economies that only differ in the role played by habit formation. Once preferences are properly adjusted so that the Intertemporal Elasticity of Substituion is the same in all model economies studied, we find that habit formation brings a hefty increase in precautionary savings and very mild reductions in the coefficient of variation and in the Gini index of wealth. We also find that the reductions in these measures of inequality also hold when we adjust our economy so that aggregate savings are the same as in the economy without habit formation. These findings hold for both persistent and non persistent habits although for the former the quantitative size of the effects is much larger. We conclude that habit formation, while being a mechanism that increases the amount of precautionary savings generated in a model, does not change the implications for wealth inequality that arise from standard models.
Intrinsic frame transport for a model of nematic liquid crystal
No full textWe present a computer simulation study of the dynamical properties of a nematic liquid crystal model. The diffusional motion of the nematic director is taken into account in our calculations in order to give a proper estimate of the transport coefficients, Differently from other groups we do not attempt to stabilize the director through rigid constraints or applied external fields. We instead define an intrinsic frame which moves along with the director at each step of the simulation, The transport coefficients computed in the intrinsic frame are then compared against the ones calculated in the fixed laboratory frame, to show the inadequacy of the latter for systems with less than 500 molecules, Using this general scheme on the Gay-Berne liquid crystal model, we evidence the natural motion of the director and attempt to quantify its intrinsic time scale and size dependence. Through extended simulations of systems of different size we calculate the diffusion and viscosity coefficients of this model and compare our results with values previously obtained with fixed director
A Note on Entrepreneurial Risk, Capital Market Imperfections, and Heterogeneity
No full textEmpirical evidence shows that entrepreneurs hold a large fraction of wealth, have higher saving rates than workers, and face substantial uninsurable entrepreneurial and investment risks. This paper constructs a heterogeneous-agent general equilibrium model with uninsurable entrepreneurial risk and capital market imperfections to explore the implications of uninsurable entrepreneurial risk for wealth distribution and aggregate activity in an incomplete market economy. It is shown that entrepreurial risk can substantially affect both the wealth distribution and the macroeconomy.Wealth Distribution, Idiosyncratic Entrepreneurial Risk, Incomplete Capital Markets
Constrained efficiency in the neoclassical growth model with uninsurable idiosyncratic shocks
No full textWe investigate the welfare properties of the one-sector neoclassic growth model with uninsurable idiosyncratic shocks. We focus on the constrained efficiency notion of the general equilibrium literature, and we demonstrate constrained inefficiency for our model. We provide a characterization of constrained efficiency that uses the first-order condition of a constrained planner's problem that points to the margins of relevance for whether capital is too high or too low: the income composition of the (consumption-)poor. We calibrate our benchmark model parameters governing idiosyncratic risks to the U.S. earnings and wealth distribution, and for this distribution the income of the poor is mainly composed of labor earnings. We compute the constrained-efficient allocations - including transition dynamics - for our model economy, and we conclude that the long-run capital stock in a laissez-faire world is not only too low, but much too low. We also show that one can find parameterizations with different qualitative features: in one case, the steady-state capital stock is too high, and in another case no steady state exists.Constrained efficiency, idiosyncratic risks, neoclassical growth model
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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