2,278 research outputs found
Holocene environmental change in coastal Denmark: interactions between land, sea and society
In this study a multiproxy approach (including sedimentary techniques, diatoms, molluscs,
foraminifera, sedimentary pigments, isotopes, pollen and plant macrofossils) has been adopted
to assess environmental change over the last ~9,000 years at three Danish coastal sites (Kilen,
Norsminde Fjord and Korup SĂž). Particular focus has been placed on periods of intense human
coastal occupation, identifiable in Denmarkâs rich coastal archaeological record (i.e. shell
midden accumulation periods), to test critically, hypotheses that changes in the marine
environment were contemporary with major cultural and societal changes over the last ~9,000
years. For example, it has been proposed that a decrease in salinity was responsible for the
widespread oyster decline, apparent in the Neolithic layers of a number of Danish shell
middens. This hypothesis, however, remains speculative to date, lacking any high-resolution
and quantitative salinity data covering the Mesolithic-Neolithic transition. Inside the
agricultural era, two more phases of shell midden accumulation occur (i.e. during the Pitted
Ware/Single Grave cultural period and the Iron Age), suggesting that people must have
returned to the sea at these times for increased exploitation of its resources. A diatom-based
salinity transfer function (WAPLS-C3 model, r2
boot = 0.923, RMSEP= 0.36 square root salinity
units) based on a trans-Baltic training set has been applied to fossil diatom datasets from each
site for quantitative assessment of salinity change over the study period. The multiproxy results
presented in this study demonstrate a close connection between environmental change and
human exploitation of marine resources over the Holocene. This relationship, however, is
complex, with the individual fjord systems often exhibiting spatially different responses (i.e.
variations in the sedimentary regime, salinity, productivity and nutrient status) to changes in
key forcing mechanisms such as sea level change, climate change and human impact upon the
catchment (following the introduction of agriculture). Environmental hypotheses for cultural
change are reviewed on the basis of the evidence presented in this study. Diatomenvironmental
relationships have also been modelled (using multivariate techniques) at Korup
SĂž and Norsminde Fjord using proxy data as âpredictorâ variables for changes in the terrestrial
and marine environment. These results suggest that a variety of marine, climatic, human and
catchment related processes are important in explaining a proportion of the variation in the
fossil diatom datasets, but these influences tend to vary temporally throughout the profile (e.g.
human impact becomes important after ~3,900 BC)
POSTURE PICTURES AND OTHER TORTURES: THE BATTLE TO CONTROL ESTHER GREENWOODâS BODY
Beginning in the 1940s and continuing into the 1960s, Dr. William H. Sheldon and his assistants took thousands of what became known as the âPosture Picturesâ at the Ivy League, Seven Sister, and other colleges as well as at hospitals, factories, and prisons. Sheldon believed that there were three basic factors in human body types and that any given body could be mapped and charted using a three-digit code he called the âsomatype.â[1] In the 1954 Atlas of Men, Sheldon published over one thousand examples of his eighty male somatypes at various ages and stages of life. Atlas of Men is a studbook as Sheldon identifies each somatype with a unique number and corresponding animal totem expressing the subjectâs strength, relative intelligence, and virility. Sheldon begins to reveal the depths of the projectâs duplicity when he states that âit may be a good thing, on the whole, that courses in somatyping are not yet generally taught in the womenâs collegesâ (209). While somatyping may not have been taught at the womenâs colleges, patriarchal control of womenâs bodies, enforced by fears of punishment for deviance from the norm, surely was. And that lesson stuck as evidenced by Sylvia Plathâs description of Posture Pictures in her autobiographical novel The Bell Jar (1963), published some thirteen years after she stood for her own Posture Picture as a new student at Smith College
The Lax conjecture is true
In 1958 Lax conjectured that hyperbolic polynomials in three variables are
determinants of linear combinations of three symmetric matrices. This
conjecture is equivalent to a recent observation of Helton and Vinnikov.Comment: 7 pages, Proceedings to the AMS, to appear. Added background materia
Oxygen isotopes in Molluscan shell: applications in environmental archaeology
Oxygen isotope geochemistry of Molluscan shell is an essential part of environmental archaeology and over the last decade has contributed significantly to the understanding of the past inhabitants of our planet. From the analysis of collected (and disposed of) shells we can gain information on environmental data from the species assemblages and also from the shell chemistry. In particular, intra-seasonal information can be gained from shells by analysing the isotope composition of the shell from successive growth increments. Here, we describe some of the recent developments in the use of oxygen isotopes in environmental archaeology. In particular, we consider preservation and sampling and describe how ÎŽ18O can provide us with information on seasonal climate, season of collection as well as changes in global climate
Monodisperse self-assembly in a model with protein-like interactions
We study the self-assembly behaviour of patchy particles with `protein-like'
interactions that can be considered as a minimal model for the assembly of
viral capsids and other shell-like protein complexes. We thoroughly explore the
thermodynamics and dynamics of self assembly as a function of the parameters of
the model and find robust assembly of all target structures considered. Optimal
assembly occurs in the region of parameter space where a free energy barrier
regulates the rate of nucleation, thus preventing the premature exhaustion of
the supply of monomers that can lead to the formation of incomplete shells. The
interactions also need to be specific enough to prevent the assembly of
malformed shells, but whilst maintaining kinetic accessibility. Free-energy
landscapes computed for our model have a funnel-like topography guiding the
system to form the target structure, and show that the torsional component of
the interparticle interactions prevents the formation of disordered aggregates
that would otherwise act as kinetic traps.Comment: 11 pages; 10 figure
THREE-DIMENSIONAL ATMOSPHERIC CIRCULATION OF WARM AND HOT JUPITERS: EFFECTS OF ORBITAL DISTANCE, ROTATION PERIOD, AND NONSYNCHRONOUS ROTATION
Efforts to characterize extrasolar giant planet (EGP) atmospheres have so far emphasized planets within 0.05 AU of their stars. Despite this focus, known EGPs populate a continuum of orbital separations from canonical hot Jupiter values (0.03â0.05 AU) out to 1 AU and beyond. Unlike typical hot Jupiters, these more distant EGPs will not generally be synchronously rotating. In anticipation of observations of this population, we here present three-dimensional atmospheric circulation models exploring the dynamics that emerge over a broad range of rotation rates and incident stellar fluxes appropriate for warm and hot Jupiters. We find that the circulation resides in one of two basic regimes. On typical hot Jupiters, the strong dayânight heating contrast leads to a broad, fast superrotating (eastward) equatorial jet and large dayânight temperature differences. At faster rotation rates and lower incident fluxes, however, the dayânight heating gradient becomes less important, and baroclinic instabilities emerge as a dominant player, leading to eastward jets in the midlatitudes, minimal temperature variations in longitude, and, often, weak winds at the equator. Our most rapidly rotating and least irradiated models exhibit similarities to Jupiter and Saturn, illuminating the dynamical continuum between hot Jupiters and the weakly irradiated giant planets of our own solar system. We present infrared (IR) light curves and spectra of these models, which depend significantly on incident flux and rotation rate. This provides a way to identify the regime transition in future observations. In some cases, IR light curves can provide constraints on the rotation rate of nonsynchronously rotating planets.United States. National Aeronautics and Space Administration (NASA Origins and Planetary Atmospheres grant NNX12AI79G))United States. National Aeronautics and Space Administration (NASA Origins and Planetary Atmospheres grant NNX10AB91G
Constraints on the Atmospheric Circulation and Variability of the Eccentric Hot Jupiter XO-3b
We report secondary eclipse photometry of the hot Jupiter XO-3b in the
4.5~m band taken with the Infrared Array Camera (IRAC) on the Spitzer
Space Telescope. We measure individual eclipse depths and center of eclipse
times for a total of twelve secondary eclipses. We fit these data
simultaneously with two transits observed in the same band in order to obtain a
global best-fit secondary eclipse depth of and a center of
eclipse phase of . We assess the relative magnitude of
variations in the dayside brightness of the planet by measuring the size of the
residuals during ingress and egress from fitting the combined eclipse light
curve with a uniform disk model and place an upper limit of 0.05. The new
secondary eclipse observations extend the total baseline from one and a half
years to nearly three years, allowing us to place an upper limit on the
periastron precession rate of degrees/day the tightest
constraint to date on the periastron precession rate of a hot Jupiter. We use
the new transit observations to calculate improved estimates for the system
properties, including an updated orbital ephemeris. We also use the large
number of secondary eclipses to obtain the most stringent limits to date on the
orbit-to-orbit variability of an eccentric hot Jupiter and demonstrate the
consistency of multiple-epoch Spitzer observations.Comment: 14 pages, 11 figures, published by Ap
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