912 research outputs found
"Low-state" Black Hole Accretion in Nearby Galaxies
I summarize the main observational properties of low-luminosity AGNs in
nearby galaxies to argue that they are the high-mass analogs of black hole
X-ray binaries in the "low/hard" state. The principal characteristics of
low-state AGNs can be accommodated with a scenario in which the central engine
is comprised of three components: an optically thick, geometrically accretion
disk with a truncated inner radius, a radiatively inefficient flow, and a
compact jet.Comment: 8 pages. To appear in From X-ray Binaries to Quasars: Black Hole
Accretion on All Mass Scales, ed. T. J. Maccarone, R. P. Fender, and L. C. Ho
(Dordrecht: Kluwer
Presacral Teratocarcinoma Presenting as Anal Fistula and Rectal Adenocarcinoma: A Unique Case Presentation and Literature Review
Somatic malignancy arising from presacral or retroperitoneal primary teratoma is extremely rare. We report the case of a 37-year-old male patient with adenocarcinoma of respiratory type arising from primary presacral teratoma, but which first presented as anal fistula and rectal adenocarcinoma. The two tumors show the same morphology and immunophenotype (CK7–CK20+CDx2+). Malignant adenocarcinoma transformations from the normal respiratory epithelium are also found. To the best of our knowledge, this is the second case of respiratory type adenocarcinoma arising from primary presacral mature cystic teratoma
Persistent Currents and Dissipation in Narrow Bilayer Quantum Hall Bars
Bilayer quantum Hall states support a flow of nearly dissipationless
staggered current which can only decay through collective channels. We study
the dominant finite-temperature dissipation mechanism which in narrow bars is
driven by thermal nucleation of pseudospin solitons. We find the
finite-temperature resistivity, predict the resulting staggered current-voltage
characteristics, and calculate the associated zero-temperature critical
staggered current and gate voltage.Comment: 4 pgs. REVTeX, 3 eps figure
A P53-Independent DNA Damage Response Suppresses Oncogenic Proliferation and Genome Instability
The Mre11-Rad50-Nbs1 complex is a DNA double-strand break sensor that mediates a tumor-suppressive DNA damage response (DDR) in cells undergoing oncogenic stress, yet the mechanisms underlying this effect are poorly understood. Using a genetically inducible primary mammary epithelial cell model, we demonstrate that Mre11 suppresses proliferation and DNA damage induced by diverse oncogenic drivers through a p53-independent mechanism. Breast tumorigenesis models engineered to express a hypomorphic Mre11 allele exhibit increased levels of oncogene-induced DNA damage, R-loop accumulation, and chromosomal instability with a characteristic copy number loss phenotype. Mre11 complex dysfunction is identified in a subset of human triple-negative breast cancers and is associated with increased sensitivity to DNA-damaging therapy and inhibitors of ataxia telangiectasia and Rad3 related (ATR) and poly (ADP-ribose) polymerase (PARP). Thus, deficiencies in the Mre11-dependent DDR drive proliferation and genome instability patterns in p53-deficient breast cancers and represent an opportunity for therapeutic exploitation
Localizing fields on brane in magnetized backgound
To localize the scalar, fermion, and abelian gauge fields on our 3-brane, a
simple mechanism with a hypothetical "magnetic field" in the bulk is proposed.
This mechanism is to treat all fields in the equal footing without ad hoc
consideration. In addition, the machanism can be easily realized in a flat
dimension six Minkowski space and it works even in the weak coupling limit
The black-hole masses of Seyfert galaxies and quasars
The central black-hole masses of a sample of 30 luminous quasars are
estimated using H-beta FWHM measurements from a combination of new and
previously-published nuclear spectra. The quasar black-hole mass estimates are
combined with reverberation-mapping measurements for a sample of Seyfert
galaxies (Wandel 1999) in order to study AGN black-hole masses over a wide
range in nuclear luminosity. It is found that black-hole mass and bulge
luminosity are well correlated and follow a relation consistent with that
expected if black-hole and bulge mass are directly proportional. Contrary to
the results of Wandel (1999) no evidence is found that Seyfert galaxies follow
a different Mblack-Mbulge relation to quasars. However, the black-hole mass
distributions of the radio-loud and radio-quiet quasar sub-samples are found to
be significantly different, with the median black-hole mass of the radio-loud
quasars a factor of three larger than their radio-quiet counterparts. Finally,
utilizing the elliptical galaxy fundamental plane to provide stellar velocity
dispersion estimates, a comparison is performed between the virial H-beta
black-hole mass estimates and those of the Mblack-sigma correlations of
Gebhardt et al. (2000a) and Merritt & Ferrarese (2000). With the disc-like
geometry of the broad-line region adopted in this paper, the virial H-beta
black-hole masses indicate that the correct normalization of the black-hole vs.
bulge mass relation is Mblack=0.0025Mbulge, while the standard assumption of
purely random broad-line velocities leads to Mblack=0.0008Mbulge. The
normalization of Mblack=0.0025Mbulge provided by the disc model is in
remarkably good agreement with that inferred for our quasar sample using the
(completely independent) Mblack-sigma correlations.Comment: 10 pages, 6 figures, accepted for publication in MNRA
HCI as a means to prosociality in the economy
HCI research often involves intervening in the economic lives of people, but researchers only rarely give explicit consideration to what actually constitutes prosociality in the economy. Much has been said previously regarding sustainability but this has largely focused on environmental rather than interpersonal relations. This paper provides an analysis of how prosocial HCI has been discussed and continues to be defined as a research field. Based on a corpus of published works, we describe a variety of genres of work relating to prosocial HCI. Key intellectual differences are explored, including the epistemological and ethical positions involved in designing for prosocial outcomes as well as how HCI researchers posit economic decision-making. Finally, emerging issues and opportunities for further debate and collaboration are discussed in turn
On the Entropy of a Quantum Field in the Rotating Black Holes
By using the brick wall method we calculate the free energy and the entropy
of the scalar field in the rotating black holes. As one approaches the
stationary limit surface rather than the event horizon in comoving frame, those
become divergent. Only when the field is comoving with the black hole (i.e.
) those become divergent at the event horizon. In the
Hartle-Hawking state the leading terms of the entropy are , where is the cut-off in the radial coordnate near the
horizon. In term of the proper distance cut-off it is written as . The origin of the divergence is that the density of state
on the stationary surface and beyond it diverges.Comment: Latex, 23 pages, 7 eps figure
A lattice model for the kinetics of rupture of fluid bilayer membranes
We have constructed a model for the kinetics of rupture of membranes under
tension, applying physical principles relevant to lipid bilayers held together
by hydrophobic interactions. The membrane is characterized by the bulk
compressibility (for expansion), the thickness of the hydrophobic part of the
bilayer, the hydrophobicity and a parameter characterizing the tail rigidity of
the lipids. The model is a lattice model which incorporates strain relaxation,
and considers the nucleation of pores at constant area, constant temperature,
and constant particle number. The particle number is conserved by allowing
multiple occupancy of the sites. An equilibrium ``phase diagram'' is
constructed as a function of temperature and strain with the total pore surface
and distribution as the order parameters. A first order rupture line is found
with increasing tension, and a continuous increase in proto-pore concentration
with rising temperature till instability. The model explains current results on
saturated and unsaturated PC lipid bilayers and thicker artificial bilayers
made of diblock copolymers. Pore size distributions are presented for various
values of area expansion and temperature, and the fractal dimension of the pore
edge is evaluated.Comment: 15 pages, 8 figure
Reliability of the beamsplitter based Bell-state measurement
A linear 50/50 beamsplitter, together with a coincidence measurement, has
been widely used in quantum optical experiments, such as teleportation, dense
coding, etc., for interferometrically distinguishing, measuring, or projecting
onto one of the four two-photon polarization Bell-states . In
this paper, we demonstrate that the coincidence measurement at the output of a
beamsplitter cannot be used as an absolute identifier of the input state
nor as an indication that the input photons have projected to
the state.Comment: 4 pages, two-colum
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