7,141 research outputs found
Determining the equation of state of dark energy from angular size of compact radio sources and X-ray gas mass fraction of galaxy clusters
Using recent measurements of angular size of high-z milliarcsecond compact
radio sources compiled by Gurvits, Kellermann and Frey (1999) and X-ray gas
mass fraction of galaxy clusters published by Allen et al. (2002,2003), we
explore their bounds on the equation of state, omega_x = p_x/rho_x, of the dark
energy, whose existence has been congruously suggested by various cosmological
observations. We relaxe the usual constraint omega_x >= -1, and find that
combining the two databases yields a nontrivial lower bound on omega_x. Under
the assumption of a flat universe, we obtain a bound -2.22 < omega_x < -0.62 at
95.4% confidence level. The 95.4% confidence bound goes to -1 =< omega_x <
-0.60 when the constraint omega_x >= -1 is imposed.Comment: 10 pages, 4 figures, accepted for publication in A&
Cosmological Equation of State and Interacting Energies
In this paper we study a model of cosmic evolution, assuming that the
different components of the universe could interact between them any time. An
effective equation of state (EOS) for the universe has been used as well. A
particular function for w, which gives a good agreement between our results and
the experimental data, has been studied. Finally, the model obtained has been
applied to different important cases
Reading In-Between the Lines: An Analysis of Dissenter
Efforts by content creators and social networks to enforce legal and
policy-based norms, e.g. blocking hate speech and users, has driven the rise of
unrestricted communication platforms. One such recent effort is Dissenter, a
browser and web application that provides a conversational overlay for any web
page. These conversations hide in plain sight - users of Dissenter can see and
participate in this conversation, whereas visitors using other browsers are
oblivious to their existence. Further, the website and content owners have no
power over the conversation as it resides in an overlay outside their control.
In this work, we obtain a history of Dissenter comments, users, and the
websites being discussed, from the initial release of Dissenter in Feb. 2019
through Apr. 2020 (14 months). Our corpus consists of approximately 1.68M
comments made by 101k users commenting on 588k distinct URLs. We first analyze
macro characteristics of the network, including the user-base, comment
distribution, and growth. We then use toxicity dictionaries, Perspective API,
and a Natural Language Processing model to understand the nature of the
comments and measure the propensity of particular websites and content to
elicit hateful and offensive Dissenter comments. Using curated rankings of
media bias, we examine the conditional probability of hateful comments given
left and right-leaning content. Finally, we study Dissenter as a social
network, and identify a core group of users with high comment toxicity.Comment: Accepted at IMC 202
Progress in Three-Dimensional Coherent X-Ray Diffraction Imaging
The Fourier inversion of phased coherent diffraction patterns offers images
without the resolution and depth-of-focus limitations of lens-based tomographic
systems. We report on our recent experimental images inverted using recent
developments in phase retrieval algorithms, and summarize efforts that led to
these accomplishments. These include ab-initio reconstruction of a
two-dimensional test pattern, infinite depth of focus image of a thick object,
and its high-resolution (~10 nm resolution) three-dimensional image.
Developments on the structural imaging of low density aerogel samples are
discussed.Comment: 5 pages, X-Ray Microscopy 2005, Himeji, Japa
Thermal-assisted Anisotropy and Thermal-driven Instability in the Superfluidity state of Two-Species Polar Fermi Gas
We study the superfluid state of two-species heteronuclear Fermi gases with
isotropic contact and anisotropic long-range dipolar interactions. By
explicitly taking account of Fock exchange contribution, we derive
self-consistent equations describing the pairing states in the system.
Exploiting the symmetry of the system, we developed an efficient way of solving
the self-consistent equations by exploiting the symmetries. We find that the
temperature tends to increase the anisotropy of the pairing state, which is
rather counterintuitive. We study the anisotropic properties of the system by
examining the angular dependence of the number density distribution, the
excitation spectrum and the pair correlation function. The competing effects of
the contact interaction and the dipolar interaction upon the anisotropy are
revealed. We derive and compute the superfluid mass density for the
system. Astonishingly, we find that becomes negative above some
certain temperature (), signaling some instability of the system.
This suggests that the elusive FFLO state may be observed in experiments, due
to an anisotropic state with a spontaneously generated superflow.Comment: 7 pages, 5 figure
Phase 2 study of combination SPI-1620 with docetaxel as second-line advanced biliary tract cancer treatment
Two rapid assays for screening of patulin biodegradation
Artículo sobre distintos ensayos para comprobar la biodegradación de la patulinaThe mycotoxin patulin is produced by the blue
mould pathogen Penicillium expansum in rotting apples
during postharvest storage. Patulin is toxic to a wide range
of organisms, including humans, animals, fungi and bacteria.
Wash water from apple packing and processing
houses often harbours patulin and fungal spores, which can
contaminate the environment. Ubiquitous epiphytic yeasts,
such as Rhodosporidium kratochvilovae strain LS11 which
is a biocontrol agent of P. expansum in apples, have the
capacity to resist the toxicity of patulin and to biodegrade
it. Two non-toxic products are formed. One is desoxypatulinic
acid. The aim of the work was to develop rapid,
high-throughput bioassays for monitoring patulin degradation
in multiple samples. Escherichia coli was highly
sensitive to patulin, but insensitive to desoxypatulinic acid.
This was utilized to develop a detection test for patulin,
replacing time-consuming thin layer chromatography or
high-performance liquid chromatography. Two assays for patulin degradation were developed, one in liquid medium
and the other in semi-solid medium. Both assays allow the
contemporary screening of a large number of samples. The
liquid medium assay utilizes 96-well microtiter plates and
was optimized for using a minimum of patulin. The semisolid
medium assay has the added advantage of slowing
down the biodegradation, which allows the study and isolation
of transient degradation products. The two assays are
complementary and have several areas of utilization, from
screening a bank of microorganisms for biodegradation
ability to the study of biodegradation pathways
Pseudomonas syringae Type III Effector HopBB1 Promotes Host Transcriptional Repressor Degradation to Regulate Phytohormone Responses and Virulence
Independently evolved pathogen effectors from three branches of life (ascomycete, eubacteria, and oomycete) converge onto the Arabidopsis TCP14 transcription factor to manipulate host defense. However, the mechanistic basis for defense control via TCP14 regulation is unknown. We demonstrate that TCP14 regulates the plant immune system by transcriptionally repressing a subset of the jasmonic acid (JA) hormone signaling outputs. A previously unstudied Pseudomonas syringae (Psy) type III effector, HopBB1, interacts with TCP14 and targets it to the SCFCOI1 degradation complex by connecting it to the JA signaling repressor JAZ3. Consequently, HopBB1 de-represses the TCP14-regulated subset of JA response genes and promotes pathogen virulence. Thus, HopBB1 fine-tunes host phytohormone crosstalk by precisely manipulating part of the JA regulon to avoid pleiotropic host responses while promoting pathogen proliferation
Improving understanding of the underlying physical process of sediment wash-off from urban road surfaces
Among the urban aquatic pollutants, the most common is sediment which also acts as a transport medium for many contaminants. Hence there is an increasing interest in being able to better predict the sediment wash–off from urban surfaces. The exponential wash-off model is the most widely used method to predict the sediment wash-off. Although a number of studies proposed various modifications to the original exponential wash-off equation, these studies mostly looked into one parameter in isolation thereby ignoring the interactions between the parameters corresponding to rainfall, catchment and sediment characteristics. Hence in this study we aim (a) to investigate the effect of rainfall intensity, surface slope and initial load on wash-off load in an integrated and systematic way and (b) to subsequently improve the exponential wash-off equation focusing on the effect of the aforementioned three parameters. A series of laboratory experiments were carried out in a full-scale setup, comprising of a rainfall simulator, a 1 m 2 bituminous road surface, and a continuous wash-off measuring system. Five rainfall intensities ranging from 33 to 155 mm/h, four slopes ranging from 2 to 16% and three initial loads ranging from 50 to 200 g/m 2 were selected based on values obtained from the literature. Fine sediment with a size range of 300–600 µm was used for all of the tests. Each test was carried out for one hour with at least 9 wash-off samples per test collected. Mass balance checks were carried out for all the tests as a quality control measure to make sure that there is no significant loss of sand during the tests. Results show that the washed off sediment load at any given time is proportional to initial load for a given combination of rainfall intensity and surface slope. This indicates the importance of dedicated modelling of build-up so as to subsequently predict wash-off load. It was also observed that the maximum fraction that is washed off from the surface increases with both rainfall intensity and the surface slope. This observation leads to the second part of the study where the existing wash-off model is modified by introducing a capacity factor which defines this maximum fraction. This capacity factor is derived as a function of wash-off coefficient, making use of the correlation between the maximum fraction and the wash-off rate. Values of the modified wash-off coefficient are presented for all combinations of rainfall intensities and surface slopes, which can be transferred to other urban catchments with similar conditions
Stabilizing the Complex Structure in Heterotic Calabi-Yau Vacua
In this paper, we show that the presence of gauge fields in heterotic
Calabi-Yau compacitifications causes the stabilisation of some, or all, of the
complex structure moduli of the Calabi-Yau manifold while maintaining a
Minkowski vacuum. Certain deformations of the Calabi-Yau complex structure,
with all other moduli held fixed, can lead to the gauge bundle becoming
non-holomorphic and, hence, non-supersymmetric. This leads to an F-term
potential which stabilizes the corresponding complex structure moduli. We use
10- and 4-dimensional field theory arguments as well as a derivation based
purely on algebraic geometry to show that this picture is indeed correct. An
explicit example is presented in which a large subset of complex structure
moduli is fixed. We demonstrate that this type of theory can serve as the
hidden sector in heterotic vacua and can co-exist with realistic particle
physics.Comment: 17 pages, Late
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