5,809 research outputs found
Evidence for anisotropic motion of the clouds in broad-line regions of BL Lacertae objects
The masses of central massive black holes in BL Lac objects are estimated
from their host galaxy absolute magnitude at R-band by using the empirical
relation between absolute magnitude of host galaxy and black hole mass. Only a
small fraction of BL Lac objects exhibit weak broad-line emission, and we
derive the sizes of the broad-line regions (BLRs) in these BL Lac objects from
the widths of their broad emission lines on the assumption of the clouds being
virilized in BLRs. It is found that the sizes of the BLRs in these sources are
usually 2-3 orders of magnitude larger than that expected by the empirical
correlation between BLR size and optical luminosity defined by a sample of
Seyfert galaxies and quasars. We discuss a variety of possibilities and suggest
it may probably be attributed to anisotropic motion of the BLR clouds in these
BL Lac objects. If the BLR geometry of these sources is disk-like, the viewing
angles between the axis and the line of sight are in the range of 2-12 degrees,
which is consistent with the unification schemes.Comment: 5 pages, accepted for publication in Ap
International Society for Optics and Photonics
Abstract: Despite popular perception, the pixel, the smallest visible element used in digital expression, actually has a history that goes farther back than most of us realize. Although, contemporary generative art has evolved from the coalescence of artistic practices and technology, it is the added innate function of the human brain to form meaningful imagery from a variety of visual stimuli that has provided the primary environment in which the pixel is employed. Though a pixel can be viewed merely as a container for smaller digital elements (for example RGB color values), it is the smallest visible component a viewer interacts with in the digital world. It is the role of the pixels in a collection to provide the viewer with the necessary information required to create a meaningful image. The human brain has an incredible capacity to link, reference, and formulate meaningful structures from visual information even where the stimuli is limited, selective, random or meaningless. This is a phenomenon known as apophenia. Utilizing apophenia as the vehicle for exploration, this paper will trace the trajectory of pixel evolution from Bronze Age Mesopotamia (~1500 BC) through the early 20th century. The purpose of this investigation is to not only establish the greater history of the pixel in image construction, but to provide a greater context for understanding the inherent modes of human perception and how these ideas interact with, inform, and alter our experiences with works of generative art. Example Abstract Despite popular perception, the pixel, the smallest visible element used in digital expression, has a history that goes farther back than most of us realize. While contemporary generative art has evolved from the coalescence of artistic practices and technology, it is the human brain's ability to create comprehensible imagery from a variety of visual stimuli that provides the primary environment in which the pixel is employed. Although a pixel can be considered simply as a container for smaller digital elements, it is the smallest visible component a viewer interacts with in the digital world. The role of pixels in a collection is to provide a viewer with the necessary information required to create a meaningful image. The human brain has an incredible capacity to link, reference, and formulate coherent structures from visual information even in cases where the stimuli are limited, selective, random or meaningless. This phenomenon is known as apophenia. Utilizing apophenia as the vehicle for exploration, this paper will trace the trajectory of pixel evolution from Bronze Age Mesopotamia (~1500 BCE) through the early 20 th century. The purpose behind this investigation is to not only establish the greater history of the pixel in image construction, but also to provide a greater context for understanding the inherent modes of perception and how these ideas interact with, inform, and alter our experiences with works of generative art
Retrospective Assessment of a Potential Cadmium Hazard
Author Institution: Department of Geology, The University of AkronIn 1968 an accidental discharge of cadmium plating solution caused a significant fish kill near Ravenna, Ohio. Water (130 samples) from West Branch Reservoir in 1971 and 1973 contained up to 0.055 mg/l cadmium, and fish (nine species, muscle tissue) contained up to 0.34 mg/kg. As a control, water and fish were sampled from Nimisila Reservoir. Cadmium was not detected in water (eight samples, 0.001 mg/l detection limit) and was detected in only one of eight species of fish (0.21 mg/kg)
Positive interplay between FFAR4/GPR120, DPP-IV inhibition and GLP-1 in beta cell proliferation and glucose homeostasis in obese high fat fed mice
G-protein coupled receptor-120 (GPR120; FFAR4) is a free fatty acid receptor, widely researched for its glucoregulatory and insulin release activities. This study aimed to investigate the metabolic advantage of FFAR4/GPR120activation using combination therapy. C57BL/6 mice, fed a High Fat Diet (HFD) for 120 days to induce obesity-diabetes, were subsequently treated with a single daily oral dose of FFAR4/GPR120 agonist Compound A (CpdA) (0.1ÎŒmol/kg) alone or in combination with sitagliptin (50mg/kg) for 21 days. After 21-days, glucose homeostasis, islet morphology, plasma hormones and lipids, tissue genes (qPCR) and protein expression (immunocytochemistry) were assessed. Oral administration of CpdA improved glucose tolerance (34%
Markarian 421's Unusual Satellite Galaxy
We present Hubble Space Telescope (HST) imagery and photometry of the active
galaxy Markarian 421 and its companion galaxy 14 arcsec to the ENE. The HST
images indicate that the companion is a morphological spiral rather than
elliptical as previous ground--based imaging has concluded. The companion has a
bright, compact nucleus, appearing unresolved in the HST images. This is
suggestive of Seyfert activity, or possibly a highly luminous compact star
cluster. We also report the results of high dynamic range long-slit
spectroscopy with the slit placed to extend across both galaxies and nuclei. We
detect no emission lines in the companion nucleus, though there is evidence for
recent star formation. Velocities derived from a number of absorption lines
visible in both galaxies indicate that the two systems are probably tidally
bound and thus in close physical proximity. Using the measured relative
velocities, we derive a lower limit on the MKN 421 mass within the companion
orbit (R \sim 10 kpc) of 5.9 \times 10^{11} solar masses, and a mass-to-light
ratio of >= 17. Our spectroscopy also shows for the first time the presence of
H\alpha and [NII] emission lines from the nucleus of MKN 421, providing another
example of the appearance of new emission features in the previously
featureless spectrum of a classical BL Lac object. We see both broad and narrow
line emission, with a velocity dispersion of several thousand km s^{-1} evident
in the broad lines.Comment: LaTeX (aaspp4 style), 28 pages, 8 figures, to appear in AJ. Revised
text from ref. comments; new & modified figures; new photometry included;
minor corrections of typos. Color version of Fig. 1 to appear in Feb. 2000
Sky & Telescop
Moving from a Product-Based Economy to a Service-Based Economy for a More Sustainable Future
Traditionally, economic growth and prosperity have been linked with the availability, production and distribution of tangible goods as well as the ability of consumers to acquire such goods. Early evidence regarding this connection dates back to Adam Smith's Wealth of Nations (1776), in which any activity not resulting in the production of a tangible good is characterized as unproductive of any value." Since then, this coupling of economic value and material production has been prevalent in both developed and developing economies throughout the world. One unintended consequence of this coupling has been the exponential increase in the amount of solid waste being generated. The reason is that any production and consumption of material goods eventually generates the equivalent amount of (or even more) waste. Exacerbating this problem is the fact that, with today's manufacturing and supply chain management technologies, it has become cheaper to dispose and replace most products rather than to repair and reuse them. This has given rise to what some call a disposable society." To put things in perspective: In 2012 households in the U.K. generated approximately 22 thousand tons of waste, which amounted to 411 kg of waste generated per person (Department for Environment, Food & Rural Affairs, 2015). During the same time period, households in the U.S. generated 251 million tons of waste, which is equivalent to a person generating approximately 2 kg of waste every day (U.S. Environmental Protection Agency, 2012). Out of these 251 million tons of total waste generated, approximately 20% of the discarded items were categorized as durable goods. The disposal of durable goods is particularly worrisome because they are typically produced using material from non- renewable resources such as iron, minerals, and petroleum-based raw materials
ASCA and contemporaneous ground-based observations of the BL Lacertae objects 1749+096 and 2200+420 (BL Lac)
We present ASCA observations of the radio-selected BL Lacertae objects
1749+096 (z=0.32) and 2200+420 (BL Lac, z=0.069) performed in 1995 Sept and
Nov, respectively. The ASCA spectra of both sources can be described as a first
approximation by a power law with photon index Gamma ~ 2. This is flatter than
for most X-ray-selected BL Lacs observed with ASCA, in agreement with the
predictions of current blazar unification models. While 1749+096 exhibits
tentative evidence for spectral flattening at low energies, a concave continuum
is detected for 2200+420: the steep low-energy component is consistent the
high-energy tail of the synchrotron emission responsible for the longer
wavelengths, while the harder tail at higher energies is the onset of the
Compton component. The spectral energy distributions from radio to gamma-rays
are consistent with synchrotron-self Compton emission from a single homogeneous
region shortward of the IR/optical wavelengths, with a second component in the
radio domain related to a more extended emission region. For 2200+420,
comparing the 1995 Nov state with the optical/GeV flare of 1997 July, we find
that models requiring inverse Compton scattering of external photons provide a
viable mechanism for the production of the highest (GeV) energies during the
flare. An increase of the external radiation density and of the power injected
in the jet can reproduce the flat gamma-ray continuum observed in 1997 July. A
directly testable prediction of this model is that the line luminosity in
2200+420 should vary shortly after (~1 month) a non-thermal synchrotron flare.Comment: 28 pages,6 figures, 5 tables; LaTeX document. accepted for
publication in the Astrophysical Journa
An analysis of likes and dislikes for history and geography of 3360 sixth grade children
Thesis (Ed.M.)--Boston Universit
Does Every Quasar Harbor A Blazar?
Assuming there is a blazar type continuum in every radio-loud quasar, we find
that the free-free heating due to the beamed infrared continuum can greatly
enhance collisionally excited lines, and thus explain the stronger CIV
1549 line emission observed in radio loud quasars. We further predict
that the CIV line should show variability {\it not} associated with observed
continuum or Ly variability.Comment: 15 pages, 3 figures; to appear in Astrophys. J. Let
The Accretion Rates and Spectral Energy Distributions of BL Lacertae Objects
We investigate the relationship between accretion rates and the spectral
energy distributions (SEDs) of BL Lac objects, using a sample of objects for
which published information on the host galaxies, emission-line luminosities,
and peak frequencies and luminosities of their SEDs are available. The sample
is composed of 43 BL Lac objects which have a relatively continuous
distribution of peak frequencies. Under the assumption that the observed
emission lines are photoionized by the central accretion disk, we use the line
luminosities to estimate the accretion luminosities and hence accretion rates.
We find that low frequency-peaked BL Lac objects (LBLs) span a wide range of
accretion rates, whereas high frequency-peaked BL Lac objects (HBLs) cover a
more restricted range of lower values. There appears to be a continuous
distribution of accretion rates between the two subclasses of BL Lac objects.
We find that the peak frequency of the SED, \pknu, correlates with the
accretion rate, approximately with the form \pknu\propto \Lambda^{-3} in HBLs
and \pknu \propto \Lambda^{-0.25} in LBLs, where . The peak luminosity of the SED is also correlated with .
These results suggest that the accretion rate influences the shape of the SED
in BL Lac objects. They also support models which couple the jet and the
accretion disk. We present a physical scenario to account for the empirical
trends.Comment: 6 pages in emulateapj.sty, 3 figures 1 table. The Astrophysical
Journal (in press
- âŠ