7,144 research outputs found
Online ready reference in the public library
Online computer databases can serve as excellent and cost effective resources
for ready reference in public libraries. In the following discussion
some philosophical and cost factors as well as staffing patterns connected
with online searching will be examined. The primary source for this
information comes from a three-year attempt to maximize usage of online
searching, given existing cost constraints, in a medium-sized public
library.published or submitted for publicatio
Time Dependence of Particle Creation from Accelerating Mirrors
Particle production due to a quantized, massless, minimally coupled scalar
field in two-dimensional flat spacetime with an accelerating mirror is
investigated, with a focus on the time dependence of the process. We analyze
first the classes of trajectories previously investigated by Carlitz and Willey
and by Walker and Davies. We then analyze four new classes of trajectories, all
of which can be expressed analytically and for which several ancillary
properties can be derived analytically. The time dependence is investigated
through the use of wave packets for the modes of the quantized field that are
in the out vacuum state. It is shown for most of the trajectories studied that
good time resolution of the particle production process can be obtained.Comment: 21 pages, 5 figure
Black Hole - Moving Mirror II: Particle Creation
There is an exact correspondence between the simplest solution to Einstein's
equations describing the formation of a black hole and a particular moving
mirror trajectory. In both cases the Bogolubov coefficients in 1+1 dimensions
are identical and can be computed analytically. Particle creation is
investigated by using wave packets. The entire particle creation history is
computed, incorporating the early-time non-thermal emission due to the
formation of the black hole (or the early-time acceleration of the moving
mirror) and the evolution to a Planckian spectrum.Comment: Contribution to MG14 Proceedings, 5 pages, 4 figure
Mirror Reflections of a Black Hole
An exact correspondence between a black hole and an accelerating mirror is
demonstrated. It is shown that for a massless minimally coupled scalar field
the same Bogolubov coefficients connecting the "in" and "out" states occur for
a (1+1)D flat spacetime with a particular perfectly reflecting accelerating
boundary trajectory and a (1+1)D curved spacetime in which a null shell
collapses to form a black hole. Generalization of the latter to the (3+1)D case
is discussed. The spectral dynamics is computed in both (1+1)-dimensional
spacetimes along with the energy flux in the spacetime with a mirror. It is
shown that the approach to equilibrium is monotonic, asymmetric in terms of the
rate, and there is a specific time which characterizes the system when it is
the most out-of-equilibrium.Comment: 25 pages, 7 figure
Black Hole - Moving Mirror I: An Exact Correspondence
An exact correspondence is shown between a new moving mirror trajectory in
(1+1)D and a spacetime in (1+1)D in which a black hole forms from the collapse
of a null shell. It is shown that the Bogolubov coefficients between the "in"
and "out" states are identical and the exact Bogolubov coefficients are
displayed. Generalization to the (3+1)D black hole case is discussed.Comment: Contribution to MG14 Proceedings, 5 pages, 1 figur
Expansion of Diplopterys at the Expense of Banisteriopsis (Malpighiaceae)
Phylogenetic analyses of molecular and morphological data have shown the genus Banisteriopsis to be polyphyletic and the genus Diplopterys to be nested within Banisteriopsis subg. Pleiopterys, which is not in the clade that contains the type of the name Banisteriopsis. Therefore, it is necessary to take up the name Diplopterys for the small genus formerly called that plus subg. Pleiopterys of Banisteriopsis. Adescription of the amplified genus Diplopterys is provided, two new species are described (D. bahianaand and D. carvalhoi), and the following new combinations in Diplopterysare proposed, with all combinations by W. R. Anderson and C. Cav. Davis: D. amplectens, D. cachimbensis, D. caduciflora, D. cristata,D. erianthera, D. heterostyla, D. hypericifolia, D. krukoffii, D. leiocarpa, D. longialata, D. lucida, D. lutea, D. nigrescens, D. nutans, D. patula, D. peruviana, D. platyptera, D. populifolia, D. pubipetala, D. rondoniensis, D. schunkei, D. sepium, D. valvata, D. virgultosa, and D. woytkowskii. Illustrations are provided for D. bahiana, D. cabrerana, D. carvalhoi, D. pauciflora, D. pubipetala, and D. valvata.Organismic and Evolutionary Biolog
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A Complete Generic Phylogeny of Malpighiaceae Inferred from Nucleotide Sequence Data and Morphology
Premise of the study: The Malpighiaceae include ∼1300 tropical flowering plant species in which generic definitions and intergeneric relationships have long been problematic. The goals of our study were to resolve relationships among the 11 generic segregates from the New World genus Mascagnia, test the monophyly of the largest remaining Malpighiaceae genera, and clarify the placement of Old World Malpighiaceae.
Methods: We combined DNA sequence data for four genes (plastid ndhF, matK, and rbcL and nuclear PHYC) from 338 ingroup accessions that represented all 77 currently recognized genera with morphological data from 144 ingroup species to produce a complete generic phylogeny of the family.
Key results and conclusions: The genera are distributed among 14 mostly well-supported clades. The interrelationships of these major subclades have strong support, except for the clade comprising the wing-fruited genera (i.e., the malpighioid+Amorimia, Ectopopterys, hiraeoid, stigmaphylloid, and tetrapteroid clades). These results resolve numerous systematic problems, while others have emerged and constitute opportunities for future study. Malpighiaceae migrated from the New to Old World nine times, with two of those migrants being very recent arrivals from the New World. The seven other Old World clades dispersed much earlier, likely during the Tertiary. Comparison of floral morphology in Old World Malpighiaceae with their closest New World relatives suggests that morphological stasis in the New World likely results from selection by neotropical oil-bee pollinators and that the morphological diversity found in Old World flowers has evolved following their release from selection by those bees.Organismic and Evolutionary Biolog
(2091) Proposal to conserve the name Mascagnia against Triopterys (Malpighiaceae)
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146928/1/tax615027.pd
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