524 research outputs found
Graveyard For Britons, West Florida, 1763-1781
Today it is known as the Miracle Strip, and every spring its long white beaches beckon to sun-starved multitudes who flock to that stretch of coast centering upon Pensacola to the east and Mobile to the west. There lie warmth, relaxation, recreation, and health. Few of todayâs sun-worshipers remember that Pensacola was once the swampy, fever-infested capital of British West Florida, and that Mobile was known as a âgraveyard for Britons.
A Naval Visitor in British West Florida
The world-wide explansion of the British Empire in the eighteenth century was dependent upon a navy whose officers were, of necessity, the most widely travelled men of their times. No less than frontiersmen, the holders of His Majestyâs commission were empire-builders. Seldom, however, were they fully conscious of the broader significance of their work or capable of literary exploitation of their experiences. John Blankett was an exception to this generalization. His career extended from the inland waters of North America to the Indian Ocean, from Russia to South Africa, from the English Channel to the Red Sea where he last flew his broad pennant. Blankett possessed a keen eye for the unique and delighted in sharing his observations with any who might find them useful or interesting. He was the author of a brief book on Portugal and several lengthy descriptive and strategic memoranda addressed to such influential British statesmen as the Earl of Shelburne
Comparison of S-100 and OKT6 Antisera in Human Skin
The monoclonal antibody OKT6 and antisera against S-100 protein have both been advocated as immunologic markers of Langerhans cells in the skin. S-100 antiserum has an advantage in its ability to stain Langerhans cells in paraffin tissues. In order to evaluate whether these antibodies stain equivalent numbers of Langerhans cells in skin, we compared the staining patterns of S-100 antiserum and OKT6 antibody on biopsy specimens from 40 patients with leprosy using immunoperoxidase techniques. Utilizing OKT6 antibody, greater numbers of positive Langerhans cells were found in the epidermis in tuberculoid leprosy, reversal reaction, and erythema nodosum leprosum than in lepromatous leprosy. However, these differences were not observed with the S-100 antiserum and, overall, fewer cells were found as compared with the OKT6 antibody. In the dermis both antibodies stained âdendritic cellsâ that were found encircling granulomas in tuberculoid leprosy and reversal reaction. Staining in lepromatous leprosy granulomas, in contrast to the epidermal staining pattern, revealed rare OKT6-positive cells, while S-100 cells were numerous and were more diffusely distributed throughout the granuloma. Our results indicate that antiserum to S-100 protein and OKT6 antibody stain morphologically similar cells (dendritic cells), but do not provide comparable results concerning distribution and frequency of these cells
Superhumps in Cataclysmic Binaries. XXII. 1RXS J232953.9+062814
We report photometry of 1RXS J232953.9+062814, a recently discovered dwarf
nova with a remarkably short 64.2-minute orbital period. In quiescence, the
star's light curve is that of a double sinusoid, arising from the "ellipsoidal"
distortion of the Roche-lobe-filling secondary. During superoutburst, common
superhumps develop with a period 3-4% longer than P_orb. This indicates a mass
ratio M_2/M_1=0.19+-0.02, a surprisingly large value in so compact a binary.
This implies that the secondary star has a density 2-3 times higher than that
of other short-period dwarf novae, suggesting a secondary enriched by H-burning
prior to the common-envelope phase of evolution. We estimate i=50+-5 deg,
M_1=0.63 (+0.12, -0.09) M_sol, M_2=0.12 (+0.03, -0.02) M_sol, R_2=0.121
(+0.010, -0.007) R_sol, and a distance to the binary of 180+-40 pc.Comment: PDF, 17 pages, 3 tables, 5 figures; accepted, in press, to appear
June 2002, PASP; more info at http://cba.phys.columbia.edu
A High Fat Diet Increases Bone Marrow Adipose Tissue (MAT) But Does Not Alter Trabecular or Cortical Bone Mass in C57BL/6J Mice
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111767/1/jcp24954.pd
Superhumps in Cataclysmic Binaries. XXIII. V442 Ophiuchi and RX J1643.7+3402
We report the results of long observing campaigns on two novalike variables:
V442 Ophiuchi and RX J1643.7+3402. These stars have high-excitation spectra,
complex line profiles signifying mass loss at particular orbital phases, and
similar orbital periods (respectively 0.12433 and 0.12056 d). They are
well-credentialed members of the SW Sex class of cataclysmic variables. Their
light curves are also quite complex. V442 Oph shows periodic signals with
periods of 0.12090(8) and 4.37(15) days, and RX J1643.7+3402 shows similar
signals at 0.11696(8) d and 4.05(12) d. We interpret these short and long
periods respectively as a "negative superhump" and the wobble period of the
accretion disk. The superhump could then possibly arise from the heating of the
secondary (and structures fixed in the orbital frame) by inner-disk radiation,
which reaches the secondary relatively unimpeded since the disk is not
coplanar.
At higher frequencies, both stars show another type of variability:
quasi-periodic oscillations (QPOs) with a period near 1000 seconds. Underlying
these strong signals of low stability may be weak signals of higher stability.
Similar QPOs, and negative superhumps, are quite common features in SW Sex
stars. Both can in principle be explained by ascribing strong magnetism to the
white dwarf member of the binary; and we suggest that SW Sex stars are
borderline AM Herculis binaries, usually drowned by a high accretion rate. This
would provide an ancestor channel for AM Hers, whose origin is still
mysterious.Comment: PDF, 41 pages, 4 tables, 16 figures; accepted, in press, to appear
December 2002, PASP; more info at http://cba.phys.columbia.edu
Testing the areaâaltitude balance ratio (AABR) and accumulationâarea ratio (AAR) methods of calculating glacier equilibrium-line altitudes
In this study, we compare equilibrium-line altitudes (ELAs) calculated using the areaâaltitude balance ratio (AABR) and the accumulationâarea ratio (AAR) methods, with measured ELAs derived from direct field observations. We utilise a GIS toolbox to calculate the ELA for 64 extant glaciers by applying the AABR and AAR methods to DEMs and polygons of their geometry. The calculated ELAs (c-ELAs) are then compared to measured zero-net balance ELAs (znb-ELAs) obtained from mass-balance time series held by the WGMS for the same glaciers. The correlation between znb-ELAs and AABR (1.56)/AAR (0.58) c-ELAs is very strong, with an r2 = 0.99. The smallest median difference between znb-ELAs and c-ELAs (i.e. 65.5 m) is obtained when a globally representative AABR of 1.56 is used. When applied to palaeoglacier-climate applications, this difference translates to ~0.42°C, well within the uncertainty of palaeotemperature proxies used to determine mean summer temperature at the ELA. The more widely used mean AABR of 1.75 is shown to be statistically invalid due to the skewness of the dataset. On this basis, when calculating glacier ELAs, we recommend the use of a global AABR value of 1.56
60 million years of glaciation in the Transantarctic Mountains
The Antarctic continent reached its current polar location ~83âMa and became shrouded by ice sheets ~34âMa, coincident with dramatic global cooling at the Eocene-Oligocene boundary. However, it is not known whether the first Antarctic glaciers formed immediately prior to this or were present significantly earlier. Here we show that mountain glaciers were likely present in the Transantarctic Mountains during the Late Palaeocene (~60â56âMa) and middle Eocene (~48â40âMa). Temperate (warm-based) glaciers were prevalent during the Late Eocene (~40â34âMa) and, in reduced numbers, during the Oligocene (~34â23âMa), before larger, likely cold-based, ice masses (including ice sheets) dominated. Some temperate mountain glaciers were present during the Miocene Climatic Optimum (~15âMa), before a widespread switch to cold-based glaciation. Our findings highlight the longevity of glaciation in Antarctica and suggest that glaciers were present even during the Early-Cenozoic greenhouse world
Superhumps in Cataclysmic Binaries. XXV. q_crit, epsilon(q), and Mass-Radius
We report on successes and failures in searching for positive superhumps in
cataclysmic variables, and show the superhumping fraction as a function of
orbital period. Basically, all short-period systems do, all long-period systems
don't, and a 50% success rate is found at P_orb=3.1+-0.2 hr. We can use this to
measure the critical mass ratio for the creation of superhumps. With a
mass-radius relation appropriate for cataclysmic variables, and an assumed mean
white-dwarf mass of 0.75 M_sol, we find a mass ratio q_crit=0.35+-0.02.
We also report superhump studies of several stars of independently known mass
ratio: OU Virginis, XZ Eridani, UU Aquarii, and KV UMa (= XTE J1118+480). The
latter two are of special interest, because they represent the most extreme
mass ratios for which accurate superhump measurements have been made. We use
these to improve the epsilon(q) calibration, by which we can infer the elusive
q from the easy-to-measure epsilon (the fractional period excess of P_superhump
over P_orb). This relation allows mass and radius estimates for the secondary
star in any CV showing superhumps. The consequent mass-radius law shows an
apparent discontinuity in radius near 0.2 M_sol, as predicted by the disrupted
magnetic braking model for the 2.1-2.7 hour period gap. This is effectively the
"empirical main sequence" for CV secondaries.Comment: PDF, 45 pages, 9 tables, 12 figures; accepted, in press, to appear
November 2005, PASP; more info at http://cba.phys.columbia.edu
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