6,343 research outputs found
Multiple origins of serpentine-soil endemism explained by preexisting tolerance of open habitats
Extra-gynoecial pollen-tube growth in apocarpous angiosperms is phylogenetically widespread and probably adaptive
The Racial Swamps of Reconstruction: Harriet Beecher Stoweâs Life in Post-Civil War Florida
Harriet Beecher Stowe, the internationally known U.S. author and abolitionist, whom President Abraham Lincoln famously called âthe little woman who wrote the book that started this great war,â referring to Uncle Tomâs Cabin (1852) and the American Civil War (1861-1865),[1] was also the author of numerous other works, many of them much lesser known today. Stoweâs Palmetto Leaves (1873), the subject of this essay, was, for example, a best-selling travel narrative about life in Florida after the American Civil War and is considered to have been an impetus behind the modern tourist industry in Florida. Today, however, Palmetto Leaves has been mostly overlooked or forgotten by scholars. In spite of this oversight, Stoweâs text about life in Florida during the post-war period of Reconstruction merits close evaluation because it exposes Stoweâs racial, political, and gendered views as they evolved after the Civil War. Because the author and her work were so popular in their day, Palmetto Leaves makes a significant contribution to our understanding of the politics of Northern White women writers and post-Civil War sentiment in the North. As I offer in this essay, Stowe, and her largely White and female readership in the North, increasingly saw the benefits of, and helped enable, a racially hierarchical society during the period of Reconstruction. Thus, in spite of Stoweâs âpioneeringâ decision to go south in the years after the war ended, my essay complicates our understanding of the proto-feminist author and shows how Stowe ultimately eschews new frontiers in Palmetto Leaves and instead embraces racially regressive views.
[1] For more on the memory and/or myth of President Lincolnâs comment about Harriet Beecher Stowe starting the Civil War, see Sachsman et al., 8
Microscopic Enhancement of Heavy-Element Production
Realistic fusion barriers are calculated in a macroscopic-microscopic model
for several soft-fusion heavy-ion reactions leading to heavy and superheavy
elements. The results obtained in such a realistic picture are very different
from those obtained in a purely macroscopic model. For reactions on 208:Pb
targets, shell effects in the entrance channel result in fusion-barrier
energies at the touching point that are only a few MeV higher than the ground
state for compound systems near Z = 110. The entrance-channel fragment-shell
effects remain far inside the touching point, almost to configurations only
slightly more elongated than the ground-state configuration, where the fusion
barrier has risen to about 10 MeV above the ground-state energy. Calculated
single-particle level diagrams show that few level crossings occur until the
peak in the fusion barrier very close to the ground-state shape is reached,
which indicates that dissipation is negligible until very late in the fusion
process. Whereas the fission valley in a macroscopic picture is several tens of
MeV lower in energy than is the fusion valley, we find in the
macroscopic-microscopic picture that the fission valley is only about 5 MeV
lower than the fusion valley for soft-fusion reactions leading to compound
systems near Z = 110. These results show that no significant
``extra-extra-push'' energy is needed to bring the system inside the fission
saddle point and that the typical reaction energies for maximum cross section
in heavy-element synthesis correspond to only a few MeV above the maximum in
the fusion barrier.Comment: 7 pages. LaTeX. Submitted to Zeitschrift fur Physik A. 5 figures not
included here. Complete preprint, including device-independent (dvi),
PostScript, and LaTeX versions of the text, plus PostScript files of the
figures, available at http://t2.lanl.gov/publications/publications.html or at
ftp://t2.lanl.gov/pub/publications/mehe
SN1987A - a Testing Ground for the KARMEN Anomaly
We show, that SN1987A can serve as an astrophysical laboratory for testing
the viability of the assertion that a new massive neutral fermion is implied by
the KARMEN data. We show that a wide range of the parameters characterizing the
proposed particle is ruled out by the above constraints making this
interpretation very unlikely.Comment: 12 pages, 1 eps figure embedded, to appear in Phys. Lett.
Sec24-Dependent Secretion Drives Cell-Autonomous Expansion of Tracheal Tubes in Drosophila
Epithelial tubes in developing organs, such as mammalian lungs and insect tracheae, need to expand their initially narrow lumina to attain their final, functional dimensions [1]. Despite its critical role for organ function, the cellular mechanism of tube expansion remains unclear. Tracheal tube expansion in Drosophila involves apical secretion and deposition of a luminal matrix [2,3,4,5], but the mechanistic role of secretion and the nature of forces involved in the process were not previously clear. Here we address the roles of cell-intrinsic and extrinsic processes in tracheal tube expansion. We identify mutations in the sec24 gene stenosis, encoding a cargo-binding subunit of the COPII complex [6,7,8]. Via genetic-mosaic analyses, we show that stenosis-dependent secretion drives tube expansion in a cell-autonomous fashion. Strikingly, single cells autonomously adjust both tube diameter and length by implementing a sequence of events including apical membrane growth, cell flattening, and taenidial cuticle formation. Known luminal components are not required for this process. Thus, a cell-intrinsic program, rather than nonautonomous extrinsic cues, controls the dimensions of tracheal tubes. These results indicate a critical role of membrane-associated proteins in the process and imply a mechanism that coordinates autonomous behaviors of individual cells within epithelial structures
Skyrme Hartree-Fock Calculations for the Alpha Decay Q Values of Super-Heavy Nuclei
Hartree-Fock calculations with the SKX Skyrme interaction are carried out to
obtain alpha-decay Q values for deformed nuclei above Pb assuming axial
symmetry. The results for even-even nuclei are compared with experiment and
with previous calculations. Predictions are made for alpha-decay Q values and
half-lives of even-even super-heavy nuclei. The results are also compared for
the recently discovered odd-even chain starting at Z=112 and N=165.Comment: 17 pages, 8 figures, 1 tabl
Sensitivity to the KARMEN Timing Anomaly at MiniBooNE
We present sensitivities for the MiniBooNE experiment to a rare exotic pion
decay producing a massive particle, Q^0. This type of decay represents one
possible explanation for the timing anomaly reported by the KARMEN
collaboration. MiniBooNE will be able to explore an area of the KARMEN signal
that has not yet been investigated
Phase Space Transport in Noisy Hamiltonian Systems
This paper analyses the effect of low amplitude friction and noise in
accelerating phase space transport in time-independent Hamiltonian systems that
exhibit global stochasticity. Numerical experiments reveal that even very weak
non-Hamiltonian perturbations can dramatically increase the rate at which an
ensemble of orbits penetrates obstructions like cantori or Arnold webs, thus
accelerating the approach towards an invariant measure, i.e., a
near-microcanonical population of the accessible phase space region. An
investigation of first passage times through cantori leads to three
conclusions, namely: (i) that, at least for white noise, the detailed form of
the perturbation is unimportant, (ii) that the presence or absence of friction
is largely irrelevant, and (iii) that, overall, the amplitude of the response
to weak noise scales logarithmically in the amplitude of the noise.Comment: 13 pages, 3 Postscript figures, latex, no macors. Annals of the New
York Academy of Sciences, in pres
- âŠ