2,996 research outputs found
The Linearity of the Cosmic Expansion Field from 300 to 30,000 km/s and the Bulk Motion of the Local Supercluster with Respect to the CMB
The meaning of "linear expansion" is explained. Particularly accurate
relative distances are compiled and homogenized a) for 246 SNe Ia and 35
clusters with v<30,000 km/s, and b) for relatively nearby galaxies with 176
TRGB and 30 Cepheid distances. The 487 objects define a tight Hubble diagram
from 300-30,000 km/s implying individual distance errors of <7.5%. Here the
velocities are corrected for Virgocentric steaming (locally 220 km/s) and - if
v_220>3500 km/s - for a 495 km/s motion of the Local Supercluster towards the
warm CMB pole at l=275, b=12; local peculiar motions are averaged out by large
numbers. A test for linear expansion shows that the corrected velocities
increase with distance as predicted by a standard model with q_0=-0.55
[corresponding to (Omega_M, Omega_Lambda)=(0.3,0.7)], but the same holds - due
to the distance limitation of the present sample - for a range of models with
q_0 between ~0.00 and -1.00. For these models H_0 does not vary systematically
by more than +/-2.3% over the entire range. Local, distance-dependent
variations are equally limited to 2.3% on average. In particular the proposed
Hubble Bubble of Zehavi et al. and Jha et al. is rejected at the 4sigma level.
- Velocity residuals in function of the angle from the CMB pole yield a
satisfactory apex velocity of 448+/-73 km/s and a coherence radius of the Local
Supercluster of ~3500 km/s (~56 Mpc), beyond which galaxies are seen on average
at rest in co-moving coordinates with respect to the CMB. Since no obvious
single accelerator of the Local Supercluster exists in the direction of the CMB
dipole its motion must be due to the integral gravitational force of all
surrounding structures. Most of the gravitational dipole comes probably from
within 5000 km/s.Comment: 52 pages, 12 figures, 6 tables; accepted for publication in The
Astrophysical Journal. v2: minor changes in both text and figure
Suppressing cyanobacterial dominance by UV-LED TiO2-photocatalysis in a drinking water reservoir: a mesocosm study.
Cyanobacteria and their toxic secondary metabolites present challenges for water treatment globally. In this study we have assessed TiO2 immobilized onto recycled foamed glass beads by a facile calcination method, combined in treatment units with 365 nm UV-LEDs. The treatment system was deployed in mesocosms within a eutrophic Brazilian drinking water reservoir. The treatment units were deployed for 7 days and suppressed cyanobacterial abundance by 85%, while at the same time enhancing other water quality parameters; turbidity and transparency improved by 40 and 81% respectively. Genomic analysis of the microbiota in the treated mesocosms revealed that the composition of the cyanobacterial community was affected and the abundance of Bacteroidetes and Proteobacteria increased during cyanobacterial suppression. The effect of the treatment on zooplankton and other eukaryotes was also monitored. The abundance of zooplankton decreased while Chrysophyte and Alveolata loadings increased. The results of this proof-of-concept study demonstrate the potential for full-scale, in-reservoir application of advanced oxidation processes as complementary water treatment processes
A giant bar induced by a merger event at z=0.4?
(Aims) We present a physical model of the formation of J033239.72-275154.7, a
galaxy observed at z=0.41 and characterized by a big young bar of size 6 kpc.
The study of this system is particularly interesting for understanding the
connection between mergers and bars as well as the properties and fate of this
system as it relates to disk galaxy formation. (Methods) We compare the
morphological and kinematic properties of J033239.72-275154.7, the latter
obtained by the GIRAFFE spectrograph, to those derived from the merger of two
spiral galaxies described by idealized N-body simulations including a star
formation prescription. (Results) We found that the general morphological shape
and most of the dynamical properties of the object can be well reproduced by a
model in which the satellite is initially put in a retrograde orbit and the
mass ratio of the system is 1:3. In such a scenario, a bar forms in the host
galaxy after the first passage of the satellite where an important fraction of
available gas is consumed in an induced burst. In its later evolution, however,
we find that J033239.72-275154.7, whose major progenitor was an Sab galaxy,
will probably become a S0 galaxy. This is mainly due to the violent relaxation
and the angular momentum loss experienced by the host galaxy during the merger
process, which is caused by the adopted orbital parameters. This result
suggests that the building of the Hubble sequence is significantly influenced
by the last major collision. In the present case, the merger leads to a severe
damage of the disk of the progenitor, leading to an evolution towards a more
bulge dominated galaxy.Comment: 6 pages, 5 figures. Accepted for publication in A&
Structural basis for the biological relevance of the invariant apical stem in IRES-mediated translation
RNA structure plays a fundamental role in internal initiation of translation. Picornavirus internal ribosome entry site (IRES) are long, efficient cis-acting elements that recruit the ribosome to internal mRNA sites. However, little is known about long-range constraints determining the IRES RNA structure. Here, we sought to investigate the functional and structural relevance of the invariant apical stem of a picornavirus IRES. Mutation of this apical stem revealed better performance of G:C compared with C:G base pairs, demonstrating that the secondary structure solely is not sufficient for IRES function. In turn, mutations designed to disrupt the stem abolished IRES activity. Lack of tolerance to accept genetic variability in the apical stem was supported by the presence of coupled covariations within the adjacent stem–loops. SHAPE structural analysis, gel mobility-shift and microarrays-based RNA accessibility revealed that the apical stem contributes to maintain IRES RNA structure through the generation of distant interactions between two adjacent stem–loops. Our results demonstrate that a highly interactive structure constrained by distant interactions involving invariant G:C base pairs plays a key role in maintaining the RNA conformation necessary for IRES-mediated translation
Neutering of cats and dogs in Ireland; pet owner self-reported perceptions of enabling and disabling factors in the decision to neuter
The paradox of poverty in rich ecosystems: impoverishment and development in the Amazon of Brazil and Bolivia
The article offers an examination of poverty and development in the Amazon, moving beyond the conventional view which places the blame on infrastructure deficiencies, economic isolation or institutional failures. It examines synergistically connected processes that form the persistent poverty-making geography of the Amazon region. The discussion is based on qualitative research conducted in two emblematic areas in Bolivia (Pando) and Brazil (Pará). The immediate and long-term causes of socioeconomic problems have been reinterpreted through a politico-ecological perspective required to investigate the apparent paradox of impoverished areas within rich ecosystems and abundant territorial resources. Empirical results demonstrate that, first, development is enacted through the exercise of hegemony over the entirety of socionature and, second, because poverty is the lasting materiality of development it cannot be alleviated through conventional mechanisms of economic growth based on socionatural hegemony. The main conclusion is that overcoming the imprint of poverty on Amazonian ecosystem entails a radical socioecological reaction. Additionally, the multiple and legitimate demands of low-income groups do not start from a state of hopeless destitution, but from a position of strength provided by their interaction with the forest ecosystems and with other comparable groups in the Amazon and elsewhere
Search for the glueball candidates f0(1500) and fJ(1710) in gamma gamma collisions
Data taken with the ALEPH detector at LEP1 have been used to search for gamma
gamma production of the glueball candidates f0(1500) and fJ(1710) via their
decay to pi+pi-. No signal is observed and upper limits to the product of gamma
gamma width and pi+pi- branching ratio of the f0(1500) and the fJ(1710) have
been measured to be Gamma_(gamma gamma -> f0(1500)). BR(f0(1500)->pi+pi-) <
0.31 keV and Gamma_(gamma gamma -> fJ(1710)). BR(fJ(1710)->pi+pi-) < 0.55 keV
at 95% confidence level.Comment: 10 pages, 3 figure
Identifying Suitable Representation Techniques for the Prioritization of Requirements and Their Interdependencies for Multiple Software Product Lines
Software requirements typically do not exist independently of each
other, rather most requirements have some type of dependency on another
requirement [4]. For companies developing software products, which depend on
each other, in so-called multiple software product lines (SPLs), systematic
requirements management, including consideration for prioritization and inter‐
dependencies, is a time-consuming and convoluted task. Representation techniques for complex requirements can convey critical requirements interdependency
information to make prioritization of requirements quicker and more accurate [1].
Based on reviewing the foremost literature, this paper identifies the representation
techniques for requirements management which are most suitable for multiple
software product lines (SPLs
Search for supersymmetry with a dominant R-parity violating LQDbar couplings in e+e- collisions at centre-of-mass energies of 130GeV to 172 GeV
A search for pair-production of supersymmetric particles under the assumption
that R-parity is violated via a dominant LQDbar coupling has been performed
using the data collected by ALEPH at centre-of-mass energies of 130-172 GeV.
The observed candidate events in the data are in agreement with the Standard
Model expectation. This result is translated into lower limits on the masses of
charginos, neutralinos, sleptons, sneutrinos and squarks. For instance, for
m_0=500 GeV/c^2 and tan(beta)=sqrt(2) charginos with masses smaller than 81
GeV/c^2 and neutralinos with masses smaller than 29 GeV/c^2 are excluded at the
95% confidence level for any generation structure of the LQDbar coupling.Comment: 32 pages, 30 figure
Search for Gravitational Wave Bursts from Soft Gamma Repeaters
We present the results of a LIGO search for short-duration gravitational
waves (GWs) associated with Soft Gamma Repeater (SGR) bursts. This is the first
search sensitive to neutron star f-modes, usually considered the most efficient
GW emitting modes. We find no evidence of GWs associated with any SGR burst in
a sample consisting of the 27 Dec. 2004 giant flare from SGR 1806-20 and 190
lesser events from SGR 1806-20 and SGR 1900+14 which occurred during the first
year of LIGO's fifth science run. GW strain upper limits and model-dependent GW
emission energy upper limits are estimated for individual bursts using a
variety of simulated waveforms. The unprecedented sensitivity of the detectors
allows us to set the most stringent limits on transient GW amplitudes published
to date. We find upper limit estimates on the model-dependent isotropic GW
emission energies (at a nominal distance of 10 kpc) between 3x10^45 and 9x10^52
erg depending on waveform type, detector antenna factors and noise
characteristics at the time of the burst. These upper limits are within the
theoretically predicted range of some SGR models.Comment: 6 pages, 1 Postscript figur
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