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Federal Holidays: Evolution and Current Practices
[Excerpt] Since 1870, numerous proposals have been introduced in Congress to establish permanent federal holidays. Only 11, however, have thus far become law. Although these patriotic celebrations are frequently referred to as “national holidays,” legally they are only applicable to federal employees and the District of Columbia. Neither Congress nor the President has asserted the authority to declare a “national holiday” that would be binding on the 50 states, as each state individually determines its legal holidays. Creating a holiday for federal employees does, however, affect each state in a variety of ways, including the delivery of mail and conduct of business with federal agencies.
Federal holidays have been created for a number of reasons. In several instances, Congress created federal holidays after a sizeable number of states created state holidays. In other instances, Congress took the lead. Additionally, each holiday was designed to emphasize a particular aspect of American heritage or to celebrate an event in American history. particular aspect of American heritage or to celebrate an event in American history
The evolution of planetary nebulae. VIII. True expansion rates and visibility times
The visibility time of planetary nebulae (PNe) in stellar systems is an
essential quantity for estimating the size of a PN population in the context of
general population studies. For instance, it enters directly into the PN death
rate determination. The basic ingredient for determining visibility times is
the typical nebular expansion velocity, as a suited average over all PN sizes
of a PN population within a certain volume or stellar system. The true
expansion speed of the outer nebular edge of a PN is, however, not accessible
by spectroscopy -- a difficulty that we surmount by radiation-hydrodynamics
modelling. We find a mean true expansion velocity of 42 km/s, i.e. nearly twice
as high as the commonly adopted value to date. Accordingly, the time for a PN
to expand to a radius of, say 0.9 pc, is only 21000 +/- 5000 years. This
visibility time of a PN holds for all central star masses since a nebula does
not become extinct as the central star fades. There is, however, a dependence
on metallicity in the sense that the visibility time becomes shorter for lower
nebular metal content. With the higher expansion rate of PNe derived here we
determined their local death-rate density as (1.4 +/- 0.5) x E-12 PN pc^{-3}
yr^{-1}, using the local PN density advocated by Frew (2008).Comment: 20 pages, 10 Figures; accepted for publication in Astronomy &
Astrophysics / Note added in proo
A Sub-block Based Image Retrieval Using Modified Integrated Region Matching
This paper proposes a content based image retrieval (CBIR) system using the
local colour and texture features of selected image sub-blocks and global
colour and shape features of the image. The image sub-blocks are roughly
identified by segmenting the image into partitions of different configuration,
finding the edge density in each partition using edge thresholding followed by
morphological dilation. The colour and texture features of the identified
regions are computed from the histograms of the quantized HSV colour space and
Gray Level Co- occurrence Matrix (GLCM) respectively. The colour and texture
feature vectors is computed for each region. The shape features are computed
from the Edge Histogram Descriptor (EHD). A modified Integrated Region Matching
(IRM) algorithm is used for finding the minimum distance between the sub-blocks
of the query and target image. Experimental results show that the proposed
method provides better retrieving result than retrieval using some of the
existing methods.Comment: 7 page
Diapause in the Boll Weevil, Anthonontus grandis Boheman, As Related to Fruiting Activity in the Cotton Plant
Studies in Arkansas show that boll weevil diapause is related to changes in fruiting activity of the cotton plant. Generally, when larval development took place while fruiting levels were increasing or being held at a high level, diapause in resulting adults was low (0-20%). Diapause was approximately 20-50% when larval development coincided with decreasing fruiting levels, and was 50-100% as true cut-out approached. Regrowth cotton generally lowered diapause incidence and as fruiting levels decreased, diapause increased. Therefore, the boll weevil not only responds to short photoperiods that are characteristic during the fall in the temperate zone, but also may respond throughout the season to changes in fruiting activity of the cotton plant
A Proposal to Measure the Quasiparticle Poisoning Time of Majorana Bound States
We propose a method of measuring the fermion parity lifetime of Majorana
fermion modes due to quasiparticle poisoning. We model quasiparticle poisoning
by coupling the Majorana modes to electron reservoirs, explicitly breaking
parity conservation in the system. This poisoning broadens and shortens the
resonance peak associated with Majorana modes. In a two lead geometry, the
poisoning decreases the correlation in current noise between the two leads from
the maximal value characteristic of crossed Andreev reflection. The latter
measurement allows for calculation of the poisoning rate even if temperature is
much higher than the resonance width.Comment: 5 pages, 5 figure
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