991 research outputs found
Chromatin Preparation and Chromatin Immuno-precipitation from Drosophila Embryos
This protocol provides specific details on how to perform Chromatin immunoprecipitation (ChIP) from Drosophila embryos. ChIP allows the matching of proteins or histone modifications to specific genomic regions. Formaldehyde-cross-linked chromatin is isolated and antibodies against the target of interest are used to determine whether the target is associated with a specific DNA sequence. This can be performed in spatial and temporal manner and it can provide information about the genome-wide localization of a given protein or histone modification if coupled with deep sequencing technology (ChIP-Seq)
The DPOSS II distant compact group survey: the EMMI-NTT spectroscopic sample
This paper presents the results of the redshift survey of 138 candidate
compact groups from the DPOSS II catalog (Iovino et al., 2003; de Carvalho et
al. 2005), which extends the available redshift range of spectroscopically
confirmed compact groups of galaxies to z~0.2. The aims of the survey are to
confirm group membership via spectroscopic redshift information, to measure the
characteristic parameters of the confirmed groups, namely mass, radius,
luminosity, velocity dispersion and crossing time, and to compare them with
those of nearby compact groups. Using available information from the
literature, we also studied the surrounding group environment and searched for
additional, previously unknown, group members, or larger scale structures to
whom the group might be associated. Of the 138 observed groups, 96 had three or
more concordant galaxies, i.e. a 70% success rate. Of these 96, 62 are isolated
on the sky, while the other 34 are close on the sky to a larger scale
structure. The remaining objects turned out to be couple of pairs or chance
projection of galaxies on the sky. Group environment and the characteristics
parameters (mass, crossing time, velocity dispersion) are evaluated and
discussed.Comment: Accepted on A&A, version updated to match the printed one. The paper
will read well even without printing figures 8 and
Redshift-Space Distortions and the Real-Space Clustering of Different Galaxy Types
We study the distortions induced by peculiar velocities on the redshift-space
correlation function of galaxies of different morphological types in the
Pisces-Perseus redshift survey. Redshift-space distortions affect early- and
late-type galaxies in different ways. In particular, at small separations, the
dominant effect comes from virialized cluster cores, where ellipticals are the
dominant population. The net result is that a meaningful comparison of the
clustering strength of different morphological types can be performed only in
real space, i.e., after projecting out the redshift distortions on the
two-point correlation function xi(r_p,pi). A power-law fit to the projected
function w_p(r_p) on scales smaller than 10/h Mpc gives r_o =
8.35_{-0.76}^{+0.75} /h Mpc, \gamma = 2.05_{-0.08}^{+0.10} for the early-type
population, and r_o = 5.55_{-0.45}^{+0.40} /h Mpc, \gamma =
1.73_{-0.08}^{+0.07} for spirals and irregulars. These values are derived for a
sample luminosity brighter than M_{Zw} = -19.5. We detect a 25% increase of r_o
with luminosity for all types combined, from M_{Zw} = -19 to -20. In the
framework of a simple stable-clustering model for the mean streaming of pairs,
we estimate sigma_12(1), the one-dimensional pairwise velocity dispersion
between 0 and 1 /h Mpc, to be 865^{+250}_{-165} km/s for early-type galaxies
and 345^{+95}_{-65} km/s for late types. This latter value should be a fair
estimate of the pairwise dispersion for ``field'' galaxies; it is stable with
respect to the presence or absence of clusters in the sample, and is consistent
with the values found for non-cluster galaxies and IRAS galaxies at similar
separations.Comment: 17 LaTeX pages including 3 tables, plus 11 PS figures. Uses AASTeX
macro package (aaspp4.sty) and epsf.sty. To appear on ApJ, 489, Nov 199
Do Quasars Lens Quasars?
If the unexpectedly high frequency of quasar pairs with very different
component redshifts is due to the lensing of a population of background quasars
by the foreground quasar, typical lens masses must be \sim10^{12}M_{\sun} and
the sum of all such quasar lenses would have to contain times the
closure density of the Universe. It then seems plausible that a very high
fraction of all \sim10^{12} M_{\sun} gravitational lenses with redshifts
contain quasars. Here I propose that these systems have evolved to
form the present population of massive galaxies with M and M
>5\times10^{11} M_{\sun}.Comment: 6 pages, aas style, ams symbols, ApJL (accepted
Southern Sky Redshift Survey: Clustering of Local Galaxies
We use the two-point correlation function to calculate the clustering
properties of the recently completed SSRS2 survey. The redshift space
correlation function for the magnitude-limited SSRS2 is given by xi(s)=(s/5.85
h-1 Mpc)^{-1.60} for separations between 2 < s < 11 h-1 Mpc, while our best
estimate for the real space correlation function is xi(r) = (r/5.36 h-1
Mpc)^{-1.86}. Both are comparable to previous measurements using surveys of
optical galaxies over much larger and independent volumes. By comparing the
correlation function calculated in redshift and real space we find that the
redshift distortion on intermediate scales is small. This result implies that
the observed redshift-space distribution of galaxies is close to that in real
space, and that beta = Omega^{0.6}/b < 1, where Omega is the cosmological
density parameter and b is the linear biasing factor for optical galaxies. We
also use the SSRS2 to study the dependence of xi on the internal properties of
galaxies. We confirm earlier results that luminous galaxies (L>L*) are more
clustered than sub-L* galaxies and that the luminosity segregation is
scale-independent. We find that early types are more clustered than late types,
but that in the absence of rich clusters, the relative bias between early and
late types in real space, is not as strong as previously estimated.
Furthermore, both morphologies present a luminosity-dependent bias, with the
early types showing a slightly stronger dependence on luminosity. We also find
that red galaxies are significantly more clustered than blue ones, with a mean
relative bias stronger than that seen for morphology. Finally, we find that the
relative bias between optical and iras galaxies in real space is b_o/b_I
1.4.Comment: 43 pages, uses AASTeX 4.0 macros. Includes 8 tables and 16 Postscript
figures, updated reference
Foreign Body Reaction to Hyaluronic Acid (Restylane®): An Adverse Outcome of Lip Augmentation
Non-animal source hyaluronic acid (Restylane®) is a relatively new redefining dermal filler that is being employed with increasing frequency in the fields of dermatology and cosmetic/facial plastic surgery. We report a case of a 74-year-old woman who presented with a firm submucosal nodule of the lower lip, which clinically was thought to represent a benign neoplasm. An excisional biopsy revealed the presence of multiple cyst-like vacuolated areas surrounded by granulomatous tissue composed predominantly of histiocytes and foamy macrophages, consistent with a foreign body reaction. Subsequent to the pathology findings, the patient acknowledged that she had received injections of Restylane® to the lips approximately 6 months before discovering the nodule. She had not mentioned this to her dentist or oral and maxillofacial surgeon to whom she had been referred because she believed that these two events were not related. Although hyaluronic acid-based dermal fillers reportedly have a low incidence of long term side effects, clinicians should be aware of the possible development of foreign body reactions to these injectable agents
Acetylcholine downregulates the cough reflex in the caudal nucleus tractus solitarii of the rabbit
- …