440 research outputs found
Using Hubble Space Telescope Imaging of Nuclear Dust Morphology to Rule Out Bars Fueling Seyfert Nuclei
If AGN are powered by the accretion of matter onto massive black holes, how
does the gas in the host galaxy lose the required angular momentum to approach
the black hole? Gas easily transfers angular momentum to stars in strong bars,
making them likely candidates. Although ground-based searches for bars in
active galaxies using both optical and near infrared surface brightness have
not found any excess of bars relative to quiescent galaxies, the searches have
not been able to rule out small-scale nuclear bars. To look for these nuclear
bars we use HST WFPC2-NICMOS color maps to search for the straight dust lane
signature of strong bars. Of the twelve Seyfert galaxies in our sample, only
three have dust lanes consistent with a strong nuclear bar. Therefore, strong
nuclear bars cannot be the primary fueling mechanism for Seyfert nuclei. We do
find that a majority of the galaxies show an spiral morphology in their dust
lanes. These spiral arms may be a possible fueling mechanism.Comment: To be published in the Astronomical Journal, June 1999. 25 pages and
14 figures. Full resolution figures are available at
ftp://www.ciw.edu/pub/mregan/fullfigs.tar.g
Recommended from our members
Integrity of Evidence-Based Practice: Are Providers Modifying Practice Content or Practice Sequencing?
This study examined patterns of evidence-based treatment (EBT) implementation within community settings by evaluating integrity along separate dimensions of practice content (PC; a session included the prescribed procedure) and practice sequencing (a session occurred in the prescribed sequence) within a recent randomized effectiveness trial. We measured whether sessions showed integrity to PC and to flexible or linear practice sequences. Findings revealed that providers tended to incorporate content from the EBT protocol in most treatment sessions, but that the sequencing of the sessions was often modified, suggesting that providers are amenable to evidence-based procedures, but not necessarily their prescribed arrangement.Psycholog
Analogue mouse pointer control via an online steady state visual evoked potential (SSVEP) brain-computer interface
The steady state visual evoked protocol has recently become a popular paradigm in brain–computer interface (BCI) applications. Typically (regardless of function) these applications offer the user a binary selection of targets that perform correspondingly discrete actions. Such discrete control systems are appropriate for applications that are inherently isolated in nature, such as selecting numbers from a keypad to be dialled or letters from an alphabet to be spelled. However motivation exists for users to employ proportional control methods in intrinsically analogue tasks such as the movement of a mouse pointer. This paper introduces an online BCI in which control of a mouse pointer is directly proportional to a user's intent. Performance is measured over a series of pointer movement tasks and compared to the traditional discrete output approach. Analogue control allowed subjects to move the pointer faster to the cued target location compared to discrete output but suffers more undesired movements overall. Best performance is achieved when combining the threshold to movement of traditional discrete techniques with the range of movement offered by proportional control
Recommended from our members
The Revised Child Anxiety and Depression Scale-Short Version: Scale reduction via exploratory bifactor modeling of the broad anxiety factor.
Using a school-based (N = 1,060) and clinic-referred (N = 303) youth sample, the authors developed a 25-item shortened version of the Revised Child Anxiety and Depression Scale (RCADS) using Schmid-Leiman exploratory bifactor analysis to reduce client burden and administration time and thus improve the transportability characteristics of this youth anxiety and depression measure. Results revealed that all anxiety items primarily reflected a single “broad anxiety” dimension, which informed the development of a reduced 15-item Anxiety Total scale. Although specific DSM-oriented anxiety subscales were not included in this version, the items comprising the Anxiety Total scale were evenly pulled from the 5 anxiety-related content domains from the original RCADS. The resultant 15-item Anxiety Total scale evidenced significant correspondence with anxiety diagnostic groups based on structured clinical interviews. The scores from the 10-item Depression Total scale (retained from the original version) were also associated with acceptable reliability in the clinic-referred and school-based samples (α = .80 and .79, respectively); this is in contrast to the alternate 5-item shortened RCADS Depression Total scale previously developed by Muris, Meesters, and Schouten (2002), which evidenced depression scores of unacceptable reliability (α = .63). The shortened RCADS developed in the present study thus balances efficiency, breadth, and scale score reliability in a way that is potentially useful for repeated measurement in clinical settings as well as wide-scale screenings that assess anxiety and depressive problems. These future applications are discussed, as are recommendations for continued use of exploratory bifactor modeling in scale development.Psycholog
Metastatic Tumor Evolution and Organoid Modeling Implicate TGFBR2 as a Cancer Driver in Diffuse Gastric Cancer
Background: Gastric cancer is the second-leading cause of global cancer deaths, with metastatic disease representing the primary cause of mortality. To identify candidate drivers involved in oncogenesis and tumor evolution, we conduct an extensive genome sequencing analysis of metastatic progression in a diffuse gastric cancer. This involves a comparison between a primary tumor from a hereditary diffuse gastric cancer syndrome proband and its recurrence as an ovarian metastasis.
Results: Both the primary tumor and ovarian metastasis have common biallelic loss-of-function of both the CDH1 and TP53 tumor suppressors, indicating a common genetic origin. While the primary tumor exhibits amplification of the Fibroblast growth factor receptor 2 (FGFR2) gene, the metastasis notably lacks FGFR2 amplification but rather possesses unique biallelic alterations of Transforming growth factor-beta receptor 2 (TGFBR2), indicating the divergent in vivo evolution of a TGFBR2-mutant metastatic clonal population in this patient. As TGFBR2 mutations have not previously been functionally validated in gastric cancer, we modeled the metastatic potential of TGFBR2 loss in a murine three-dimensional primary gastric organoid culture. The Tgfbr2 shRNA knockdown within Cdh1-/-; Tp53-/- organoids generates invasion in vitro and robust metastatic tumorigenicity in vivo, confirming Tgfbr2 metastasis suppressor activity.
Conclusions: We document the metastatic differentiation and genetic heterogeneity of diffuse gastric cancer and reveal the potential metastatic role of TGFBR2 loss-of-function. In support of this study, we apply a murine primary organoid culture method capable of recapitulating in vivo metastatic gastric cancer. Overall, we describe an integrated approach to identify and functionally validate putative cancer drivers involved in metastasi
Recommended from our members
Ulcerative colitis-risk loci on chromosomes 1p36 and 12q15 found by genome-wide association study.
Ulcerative colitis is a chronic inflammatory disease of the colon that presents as diarrhea and gastrointestinal bleeding. We performed a genome-wide association study using DNA samples from 1,052 individuals with ulcerative colitis and preexisting data from 2,571 controls, all of European ancestry. In an analysis that controlled for gender and population structure, ulcerative colitis loci attaining genome-wide significance and subsequent replication in two independent populations were identified on chromosomes 1p36 (rs6426833, combined P = 5.1 x 10(-13), combined odds ratio OR = 0.73) and 12q15 (rs1558744, combined P = 2.5 x 10(-12), combined OR = 1.35). In addition, combined genome-wide significant evidence for association was found in a region spanning BTNL2 to HLA-DQB1 on chromosome 6p21 (rs2395185, combined P = 1.0 x 10(-16), combined OR = 0.66) and at the IL23R locus on chromosome 1p31 (rs11209026, combined P = 1.3 x 10(-8), combined OR = 0.56; rs10889677, combined P = 1.3 x 10(-8), combined OR = 1.29)
Outer-Sphere Contributions to the Electronic Structure of Type Zero Copper Proteins
Bioinorganic canon states that active-site
thiolate coordination promotes rapid electron transfer (ET)
to and from type 1 copper proteins. In recent work, we have
found that copper ET sites in proteins also can be constructed
without thiolate ligation (called “type zero” sites). Here we
report multifrequency electron paramagnetic resonance
(EPR), magnetic circular dichroism (MCD), and nuclear
magnetic resonance (NMR) spectroscopic data together with
density functional theory (DFT) and spectroscopy-oriented
configuration interaction (SORCI) calculations for type zero Pseudomonas aeruginosa azurin variants. Wild-type (type 1) and type
zero copper centers experience virtually identical ligand fields. Moreover, O-donor covalency is enhanced in type zero centers
relative that in the C112D (type 2) protein. At the same time, N-donor covalency is reduced in a similar fashion to type 1
centers. QM/MM and SORCI calculations show that the electronic structures of type zero and type 2 are intimately linked to the
orientation and coordination mode of the carboxylate ligand, which in turn is influenced by outer-sphere hydrogen bonding
Barred Galaxies in the Abell 901/2 Supercluster with STAGES
We present a study of bar and host disk evolution in a dense cluster
environment, based on a sample of ~800 bright (MV <= -18) galaxies in the Abell
901/2 supercluster at z~0.165. We use HST ACS F606W imaging from the STAGES
survey, and data from Spitzer, XMM-Newton, and COMBO-17. We identify and
characterize bars through ellipse-fitting, and other morphological features
through visual classification. (1) We explore three commonly used methods for
selecting disk galaxies. We find 625, 485, and 353 disk galaxies, respectively,
via visual classification, a single component S'ersic cut (n <= 2.5), and a
blue-cloud cut. In cluster environments, the latter two methods miss 31% and
51%, respectively, of visually-identified disks. (2) For moderately inclined
disks, the three methods of disk selection yield a similar global optical bar
fraction (f_bar-opt) of 34% +10%/-3%, 31% +10%/-3%, and 30% +10%/-3%,
respectively. (3) f_bar-opt rises in brighter galaxies and those which appear
to have no significant bulge component. Within a given absolute magnitude bin,
f_bar-opt is higher in visually-selected disk galaxies that have no bulge as
opposed to those with bulges. For a given morphological class, f_bar-opt rises
at higher luminosities. (4) For bright early-types, as well as faint late-type
systems with no evident bulge, the optical bar fraction in the Abell 901/2
clusters is comparable within a factor of 1.1 to 1.4 to that of field galaxies
at lower redshifts (5) Between the core and the virial radius of the cluster at
intermediate environmental densities, the optical bar fraction does not appear
to depend strongly on the local environment density and varies at most by a
factor of ~1.3. We discuss the implications of our results for the evolution of
bars and disks in dense environments.Comment: accepted for publication in ApJ, abstract abridged, for high
resolution figures see
http://www.as.utexas.edu/~marinova/STAGES/STAGES_bars.pd
A New Parametrization of the Seesaw Mechanism and Applications in Supersymmetric Models
We present a new parametrization of the minimal seesaw model, expressing the
heavy-singlet neutrino Dirac Yukawa couplings and Majorana
masses in terms of effective light-neutrino observables and an
auxiliary Hermitian matrix In the minimal supersymmetric version of the
seesaw model, the latter can be related directly to other low-energy
observables, including processes that violate charged lepton flavour and CP.
This parametrization enables one to respect the stringent constraints on
muon-number violation while studying the possible ranges for other observables
by scanning over the allowed parameter space of the model. Conversely, if any
of the lepton-flavour-violating process is observed, this measurement can be
used directly to constrain and As applications, we
study flavour-violating decays and the electric dipole moments of
leptons in the minimal supersymmetric seesaw model.Comment: Important references adde
- …