227 research outputs found
The use of audio-visual aids in a public relations program for the Medford public schools
Thesis (M.S.)--Boston University, 195
Redshift-distance Survey of Early-type Galaxies: The D_n-sigma Relation
In this paper R-band photometric and velocity dispersion measurements for a
sample of 452 elliptical and S0 galaxies in 28 clusters are used to construct a
template D_n-sigma relation. This template relation is constructed by combining
the data from the 28 clusters, under the assumption that galaxies in different
clusters have similar properties. The photometric and spectroscopic data used
consist of new as well as published measurements, converted to a common system,
as presented in a accompanying paper. The resulting direct relation, corrected
for incompleteness bias, is log{D_n} =1.203 log{sigma} + 1.406; the zero-point
has been defined by requiring distant clusters to be at rest relative to the
CMB. This zero-point is consistent with the value obtained by using the
distance to Virgo as determined by the Cepheid period-luminosity relation. This
new D_n-sigma relation leads to a peculiar velocity of -72 (\pm 189) km/s for
the Coma cluster. The scatter in the distance relation corresponds to a
distance error of about 20%, comparable to the values obtained for the
Fundamental Plane relation. Correlations between the scatter and residuals of
the D_n-sigma relation with other parameters that characterize the cluster
and/or the galaxy stellar population are also analyzed. The direct and inverse
relations presented here have been used in recent studies of the peculiar
velocity field mapped by the ENEAR all-sky sample.Comment: 46 pages, 20 figures, and 7 tables. To appear in AJ, vol. 123, no. 5,
May 200
The Evolution of Early-Type Galaxies in Distant Clusters III.: M/L_V Ratios in the z=0.33 Cluster CL1358+62
Keck spectroscopy and Hubble Space Telescope WFPC2 imaging over a 1.5x1.5 Mpc
field of CL1358+62 at z=0.33 are used to study the Fundamental Plane of
galaxies based on a new, large sample of 53 galaxies. First, we have
constructed the Fundamental Plane for the 30 E and S0 galaxies and find that it
has the following shape: r_e = sigma**(1.31+-0.13) * _e**(-0.86+-0.10),
similar to that found locally. The 1-sigma intrinsic scatter about this plane
is 14% in M/L(V), comparable to that observed in Coma. We conclude that these E
and S0 galaxies are structurally mature and homogeneous, like those observed in
nearby clusters. The M/L(V) ratios of these early-type galaxies are offset from
the Coma Fundamental Plane by delta log M/L(V) = -0.13+- 0.03 (q0=0.1),
indicative of mild luminosity evolution. This evolution suggests a formation
epoch for the stars of z > 1. We have also analyzed the M/L(V) ratios of
galaxies of type S0/a and later. These early-type spirals follow a different
plane from the E and S0 galaxies, with a scatter that is twice as large as the
scatter for the E/S0s. The difference in the tilt between the plane of the
spirals and the plane of the E/S0s is shown to be due to a systematic
correlation of velocity dispersion with residual from the plane of the
early-type galaxies. These residuals also correlate with the residuals from the
Color-Magnitude relation. Thus for spirals in clusters, we see a systematic
variation in the luminosity-weighted mean properties of the stellar populations
with central velocity dispersion. If this is a relative age trend, then
luminosity-weighted age is positively correlated with dispersion. [abridged
version]Comment: 18 pages, 8 figures; revised version, accepted by ApJ on 13 August
199
Bleeding from ruptured hepatic metastases as a cause of syncope in an octogenarian: a case report
<p>Abstract</p> <p>Introduction</p> <p>Acute hemoperitoneum as a result of hemorrhage from liver metastases is an uncommon but serious condition. The use of appropriate imaging is important in the diagnosis and can have a profound impact on subsequent management. This case is important because the presentation was of recurrent syncopal episodes with an unusual underlying cause. This case highlights the need to consider this diagnosis in the differential in patients presenting with collapse in the acute setting.</p> <p>Case presentation</p> <p>We present the case of an 85-year-old Caucasian man who was admitted following a collapse episode and was found to be persistently hypotensive despite aggressive resuscitation. An acute intra-peritoneal bleed originating from hepatic metastases from an unknown primary was identified promptly with computed tomography imaging and was subsequently managed conservatively.</p> <p>Conclusions</p> <p>This case aims to convey key teaching points: (A) the need to consider intra-abdominal hemorrhage in the differential diagnosis when assessing patients with collapse; and (B) the use of appropriate imaging such as computed tomography can facilitate a prompt diagnosis and appropriate management steps can then be taken accordingly.</p
The Extragalactic Distance Scale Key Project XXVII. A Derivation of the Hubble Constant Using the Fundamental Plane and Dn-Sigma Relations in Leo I, Virgo, and Fornax
Using published photometry and spectroscopy, we construct the fundamental
plane and D_n-Sigma relations in Leo I, Virgo and Fornax. The published Cepheid
P-L relations to spirals in these clusters fixes the relation between angular
size and metric distance for both the fundamental plane and D_n-Sigma
relations. Using the locally calibrated fundamental plane, we infer distances
to a sample of clusters with a mean redshift of cz \approx 6000 \kms, and
derive a value of H_0=78+- 5+- 9 km/s/Mpc (random, systematic) for the local
expansion rate. This value includes a correction for depth effects in the
Cepheid distances to the nearby clusters, which decreased the deduced value of
the expansion rate by 5% +- 5%. If one further adopts the metallicity
correction to the Cepheid PL relation, as derived by the Key Project, the value
of the Hubble constant would decrease by a further 6%+- 4%. These two sources
of systematic error, when combined with a +- 6% error due to the uncertainty in
the distance to the Large Magellanic Cloud, a +- 4% error due to uncertainties
in the WFPC2 calibration, and several small sources of uncertainty in the
fundamental plane analysis, combine to yield a total systematic uncertainty of
+- 11%. We find that the values obtained using either the CMB, or a flow-field
model, for the reference frame of the distant clusters, agree to within 1%. The
Dn-Sigma relation also produces similar results, as expected from the
correlated nature of the two scaling relations. A complete discussion of the
sources of random and systematic error in this determination of the Hubble
constant is also given, in order to facilitate comparison with the other
secondary indicators being used by the Key Project.Comment: 21 pages, 3 figures, Accepted for publication in Ap
The Peculiar Motions of Early-Type Galaxies in Two Distant Regions. IV. The Photometric Fitting Procedure
The EFAR project is a study of 736 candidate early-type galaxies in 84
clusters lying in two regions towards Hercules-Corona Borealis and
Perseus-Cetus at distances km/s. In this paper we
describe a new method of galaxy photometry adopted to derive the photometric
parameters of the EFAR galaxies. The algorithm fits the circularized surface
brightness profiles as the sum of two seeing-convolved components, an
and an exponential law. This approach allows us to fit the large variety of
luminosity profiles displayed by the EFAR galaxies homogeneously and to derive
(for at least a subset of these) bulge and disk parameters. Multiple exposures
of the same objects are optimally combined and an optional sky-fitting
procedure has been developed to correct for sky subtraction errors. Extensive
Monte Carlo simulations are analyzed to test the performance of the algorithm
and estimate the size of random and {\it systematic} errors. Random errors are
small, provided that the global signal-to-noise ratio of the fitted profiles is
larger than . Systematic errors can result from 1) errors in the
sky subtraction, 2) the limited radial extent of the fitted profiles, 3) the
lack of resolution due to seeing convolution and pixel sampling, 4) the use of
circularized profiles for very flattened objects seen edge-on and 5) a poor
match of the fitting functions to the object profiles. Large systematic errors
are generated by the widely used simple law to fit luminosity
profiles when a disk component, as small as 20% of the total light, is present.Comment: 47 pages, Latex File, aaspp4.sty, flushrt.sty, 16 Postscript figures,
to appear in ApJ
Titanium dioxide particle – induced goblet cell hyperplasia : association with mast cells and IL-13
BACKGROUND: Inhalation of particles aggravates respiratory symptoms including mucus hypersecretion in patients with chronic airway disease and induces goblet cell hyperplasia (GCH) in experimental animal models. However, the underlying mechanisms remain poorly understood. METHODS: To understand this, the numbers of goblet cells, Muc5ac (+) expressing epithelial cells and IL-13 expressing mast cells were measured in the trachea of sham or TiO(2 )particles – treated rats using periodic acid-Schiff, toluidine blue and immunohistochemical staining. RT-PCR for Muc-1, 2 and 5ac gene transcripts was done using RNA extracted from the trachea. Differential cell count and IL-13 levels were measured in bronchoalveolar lavage (BAL) fluid. In pretreatment groups, cyclophosphamide (CPA) or dexamethasone (DEX) was given before instillation of TiO(2). TiO(2 )treatment markedly increased Muc5ac mRNA expression, and Muc5ac (+) or PAS (+) epithelial cells 48 h following treatment. RESULTS: The concentration of IL-13 in BAL fluids was higher in TiO(2 )treated – rats when compared to those in sham rats (p < 0.05). Pretreatment with cyclophosphamide (CPA) decreased the number of neutrophils and eosinophils in BAL fluid of TiO(2 )treated – rats (p < 0.05), but affected neither the percentage of PAS (+) cells, nor IL-13 levels in the BAL fluids (p > 0.05). In contrast, pretreatment with dexamethasone (DEX) diminished the percentage of PAS (+) cells and the levels of IL-13 (p < 0.05). TiO(2 )treatment increased the IL-13 (+) mast cells (p < 0.05) in the trachea, which was suppressed by DEX (p < 0.05), but not by CPA pretreatment (p > 0.05). In addition there were significant correlations of IL-13 (+) rate of mast cells in the trachea with IL-13 concentration in BAL fluid (p < 0.01) and with the percentage of Muc5ac (+) cells in the sham and TiO(2 )treated rats (p < 0.05). CONCLUSION: In conclusion, TiO(2 )instillation induces GCH and Muc5ac expression, and this process may be associated with increased production of IL-13 by mast cells
The Updated Zwicky Catalog (UZC)
The Zwicky Catalog of galaxies (ZC), with m_Zw<=15.5mag, has been the basis
for the Center for Astrophysics (CfA) redshift surveys. To date, analyses of
the ZC and redshift surveys based on it have relied on heterogeneous sets of
galaxy coordinates and redshifts. Here we correct some of the inadequacies of
previous catalogs by providing: (1) coordinates with <~2 arcsec errors for all
of the Nuzc catalog galaxies, (2) homogeneously estimated redshifts for the
majority (98%) of the data taken at the CfA (14,632 spectra), and (3) an
estimate of the remaining "blunder" rate for both the CfA redshifts and for
those compiled from the literature. For the reanalyzed CfA data we include a
calibrated, uniformly determined error and an indication of the presence of
emission lines in each spectrum. We provide redshifts for 7,257 galaxies in the
CfA2 redshift survey not previously published; for another 5,625 CfA redshifts
we list the remeasured or uniformly re-reduced value. Among our new
measurements, Nmul are members of UZC "multiplets" associated with the original
Zwicky catalog position in the coordinate range where the catalog is 98%
complete. These multiplets provide new candidates for examination of tidal
interactions among galaxies. All of the new redshifts correspond to UZC
galaxies with properties recorded in the CfA redshift compilation known as
ZCAT. About 1,000 of our new measurements were motivated either by inadequate
signal-to-noise in the original spectrum or by an ambiguous identification of
the galaxy associated with a ZCAT redshift. The redshift catalog we include
here is ~96% complete to m_Zw<=15.5, and ~98% complete (12,925 galaxies out of
a total of 13,150) for the RA(1950) ranges [20h--4h] and [8h--17h] and
DEC(1950) range [-2.5d--50d]. (abridged)Comment: 34 pp, 7 figs, PASP 1999, 111, 43
Recommended from our members
Automated Segmentation of HeLa Nuclear Envelope from Electron Microscopy Images
This paper describes an image-processing pipeline for the automatic segmentation of the nuclear envelope of HeLcells observed through Electron Microscopy. The pipeline was applied to a 3D stack of 300 images. The intermediate results of neighbouring slices are further combined to improve the final results. Comparison with a handsegmented ground truth reported Jaccard similarity values between 94-98% on the central slices with a decrease towards the edges of the cell where the structure was considerably more complex. The processing is unsupervised and each 2D slice is processed in about 5-10 seconds running on a MacBook Pro. No systematic attempt to make the code faster was made. These encouraging results could be further used to provide data for more complex segmentation techniques like Deep Learning, which require a considerable amount of data to train architectures like Convolutional Neural Networks. The code is freely available from https://github.com/reyesaldasoro/HeLa-Cell-Segmentatio
The Galactic Center with Roman
We advocate for a Galactic center (GC) field to be added to the Galactic
Bulge Time Domain Survey (GBTDS). The new field would yield high-cadence
photometric and astrometric measurements of an unprecedented 3.3
million stars toward the GC. This would enable a wide range of science cases,
such as finding star-compact object binaries that may ultimately merge as
LISA-detectable gravitational wave sources, constraining the mass function of
stars and compact objects in different environments, detecting populations of
microlensing and transiting exoplanets, studying stellar flares and variability
in young and old stars, and monitoring accretion onto the central supermassive
black hole. In addition, high-precision proper motions and parallaxes would
open a new window into the large-scale dynamics of stellar populations at the
GC, yielding insights into the formation and evolution of galactic nuclei and
their co-evolution with the growth of the supermassive black hole. We discuss
the possible trade-offs between the notional GBTDS and the addition of a GC
field with either an optimal or minimal cadence. Ultimately, the addition of a
GC field to the GBTDS would dramatically increase the science return of Roman
and provide a legacy dataset to study the mid-plane and innermost regions of
our Galaxy.Comment: 19 pages, 3 figures. Submitted to the NASA Roman Core Community
Surveys White Paper Cal
- …