430 research outputs found
Shaping and Defining the Public Experience at the President Lincoln and Soldiers\u27 Home National Monument: Site Conservation, Presentation and Preservation
Space-Praxis: Towards a Feminist Politics of Design
Outside of the academy and professionalized practice, design has long been central to the production of feminist, political projects. Taking what I have termed space-praxis as its central analytic, this project explores a suite of feminist interventions into the built environmentâranging from the late 1960s to present day.
Formulated in response to Michel de Certeauâs theory of spatial practices, space-praxis collapses formerly bifurcated definitions of âtacticâ/âstrategyâ and âtheoryâ/âpractice.â It gestures towards those unruly, situated undertakings that are embedded in an ever-evolving, liberative politics. In turning outwards, away from the so-called masters of architecture, this thesis orients itself toward everyday practitioners who are grounded in the environment-worlds they seek to reorganize and re-imagine. Though few of the space-practitioners discussed in this work would consider themselves architects, their work at the margin of design meaningfully expands contemporary definitions of architecture. Indeed, they exemplify the ways in which architecture could be retooled as a mode of activist engagement. The diverse array of spaces investigated include a handful of womenâs centers in New York City, Cambridge, MA, and Los Angeles; the first feminist self-help gynecology clinic; an empty house in Oakland that was reclaimed by a group of Black mothers in 2019; and a series of pop-up block parties in Chicago. While this thesis in no way operates as an encyclopedia of feminist space-praxes, it highlights an array of such projects held together by their mutual investment in building feminist commons and infrastructures of care
Terrestrial Effects Of Nearby Supernovae In The Early Pleistocene
Recent results have strongly confirmed that multiple supernovae happened at
distances ~100 pc consisting of two main events: one at 1.7 to 3.2 million
years ago, and the other at 6.5 to 8.7 million years ago. These events are said
to be responsible for excavating the Local Bubble in the interstellar medium
and depositing 60Fe on Earth and the Moon. Other events are indicated by
effects in the local cosmic ray (CR) spectrum. Given this updated and refined
picture, we ask whether such supernovae are expected to have had substantial
effects on the terrestrial atmosphere and biota. In a first cut at the most
probable cases, combining photon and cosmic ray effects, we find that a
supernova at 100 pc can have only a small effect on terrestrial organisms from
visible light and that chemical changes such as ozone depletion are weak.
However, tropospheric ionization right down to the ground due to the
penetration of TeV cosmic rays will increase by nearly an order of
magnitude for thousands of years, and irradiation by muons on the ground and in
the upper ocean will increase 20-fold, which will approximately triple the
overall radiation load on terrestrial organisms. Such irradiation has been
linked to possible changes in climate and increased cancer and mutation rates.
This may be related to a minor mass extinction around the Pliocene-Pleistocene
boundary, and further research on the effects is needed.Comment: Revised version accepted at ApJ
Cryopreserved homograft valves in the pulmonary position: Risk analysis for intermediate-term failure
AbstractObjective: The purpose of this study was to examine the durability of cryopreserved homografts used to replace the âpulmonaryâ valve and to identify factors associated with their late deterioration. Methods: We reviewed our entire experience (1985-1997) with 331 survivors in whom cryopreserved homograft valves (pulmonary, n = 304; aortic, n = 27) were used to reconstruct the pulmonary outflow tract. Median age was 14 years (range, 2 daysâ62 years). Operations included Ross operation (n = 259), tetralogy of Fallot (n = 41), truncus arteriosus (n = 14), Rastelli operation (n = 11), and others (n = 6). Median follow-up was 3.8 years (range, 0.2â11.2 years); late echographic follow-up was complete for 97% of patients. Homograft failure was defined as the need for explantation and valve-related death; homograft dysfunction was defined as a pulmonary insufficiency grade 3/4 or greater and a transvalvular gradient of 40 mm Hg or greater. Results: Homograft failure occurred in 9% (30 of 331 patients; Kaplan-Meier); freedom from failure was 82% ± 4% at 8 years. Homograft dysfunction occurred in 12% (39 of 331 patients), although freedom from dysfunction was 76% ± 4% at 8 years. For aortic homografts, this was 56% ± 11%, compared to 80% ± 4% for pulmonary homografts (P = .003). For patients aged less than 3 years (n = 38), this was 51% ± 12%, compared with 87% ± 4% for older patients (P = .0001). By multivariable analysis, younger age of homograft donors, non-Ross operation, and later year of operation were associated with homograft failure; younger age of homograft donors, later year of operation, and use of an aortic homograft were associated with homograft dysfunction. Conclusions: Homograft valves function satisfactorily in the pulmonary position at mid-term follow-up. The pulmonary homograft valve appears to be more durable than the aortic homograft valve in the pulmonary position. (J Thorac Cardiovasc Surg 1999;117:141-7
Solanum viarum Dunal (Solanaceae), Primer Reporte para Honduras
La maleza invasora Solanum viarum Dunal (Solanaceae) es reportada por primera vez para Honduras. La planta, nativa de Sudamérica, fue localizada en un estacionamiento de la Escuela Agrícola Panamericana, El Zamorano, Honduras, el 26 de noviembre de 2007. Esta maleza es altamente invasora en pasturas debido a que el ganado puede transportar semillas en su tracto digestivo.DOI: http://dx.doi.org/10.5377/ceiba.v49i1.30
Temperature-dependent development, cold tolerance, and potential distribution of cricotopus lebetis (Diptera: Chironomidae), a tip miner of hydrilla verticillata (Hydrocharitaceae)
© The Author 2014. Published by Oxford University Press on behalf of the Entomological Society of America. A chironomid midge, Cricotopus lebetis (Sublette) (Diptera: Chironomidae), was discovered attacking the apical meristems of Hydrilla verticillata (L.f. Royle) in Crystal River, Citrus Co., Florida in 1992. The larvae mine the stems of H. verticillata and cause basal branching and stunting of the plant. Temperature-dependent development, cold tolerance, and the potential distribution of the midge were investigated. The results of the temperature-dependent development study showed that optimal temperatures for larval development were between 20 and 30°C, and these data were used to construct a map of the potential number of generations per year of C. lebetis in Florida. Data from the cold tolerance study, in conjunction with historical weather data, were used to generate a predicted distribution of C. lebetis in the United States. A distribution was also predicted using an ecological niche modeling approach by characterizing the climate at locations where C. lebetis is known to occur and then finding other locations with similar climate. The distributions predicted using the two modeling approaches were not significantly different and suggested that much of the southeastern United States was climatically suitable for C. lebetis
Testing the link between terrestrial climate change and Galactic spiral arm transit
We re-examine past suggestions of a close link between terrestrial climate
change and the Sun's transit of spiral arms in its path through the Milky Way
galaxy. These links produced concrete fits, deriving the unknown spiral pattern
speed from terrestrial climate correlations. We test these fits against new
data on spiral structure based on CO data that does not make simplifying
assumptions about symmetry and circular rotation. If we compare the times of
these transits to changes in the climate of Earth, not only do the claimed
correlations disappear, but also we find that they cannot be resurrected for
any reasonable pattern speed.Comment: Accepted for publication in ApJ Letters. Moderate revisions with
clarification, no change in conclusion
Atmospheric Consequences of Cosmic Ray Variability in the Extragalactic Shock Model II: Revised ionization levels and their consequences
It has been suggested that galactic shock asymmetry induced by our galaxy's
infall toward the Virgo Cluster may be a source of periodicity in cosmic ray
exposure as the solar system oscillates perpendicular to the galactic plane.
Here we investigate a mechanism by which cosmic rays might affect terrestrial
biodiversity, ionization and dissociation in the atmosphere, resulting in
depletion of ozone and a resulting increase in the dangerous solar UVB flux on
the ground, with an improved ionization background computation averaged over a
massive ensemble (about 7 x 10^5) shower simulations. We study minimal and full
exposure to the postulated extragalactic background. The atmospheric effects
are greater than with our earlier, simplified ionization model. At the lower
end of the range effects are too small to be of serious consequence. At the
upper end of the range, ~6 % global average loss of ozone column density
exceeds that currently experienced due to effects such as accumulated
chlorofluorocarbons. The intensity is less than a nearby supernova or galactic
gamma-ray burst, but the duration would be about 10^6 times longer. Present UVB
enhancement from current ozone depletion ~3% is a documented stress on the
biosphere, but a depletion of the magnitude found at the upper end of our range
would double the global average UVB flux. For estimates at the upper end of the
range of the cosmic ray variability over geologic time, the mechanism of
atmospheric ozone depletion may provide a major biological stress, which could
easily bring about major loss of biodiversity. Future high energy astrophysical
observations will resolve the question of whether such depletion is likely.Comment: 22 pages, 5 figures, to be published in Journal of Geophysical
Research--Planets. This is an update and replacement for our 2008 paper, with
a much more extensive simulation of air shower ionization. Ionization effects
and ozone depletion are somewhat large
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