242 research outputs found
Characterization of a supercoil-dependent S1 sensitive site 5\u27 to the Drosophila melanogaster hsp 26 gene
We have analyzed the prominent supercoil-dependent S1 nuclease cleavage site 5\u27 to hsp 26 in the plasmid 88B13, which contains 11.7 kilobases from the Drosophila locus 67B1. The double stranded cleavage product is generated by initial nicking on the purine strand, six preferred sites occurring between positions -96 and -90 (relative to the start of transcription) with weaker ones extending to position -84, followed by cleavage on the pyrimidine strand at positions -86 and -84. A derivative of 88B13, 88B13-X, was generated by insertion of an Xho I linker at position -84; this does not affect the positions or strand specificity of the S1 cleavage in that region. A small deletion, delta 41.1, removes the homopurine/homopyrimidine stretch from positions -86 to -132 and is no longer sensitive to cleavage by S1 nuclease 5\u27 to hsp 26. Mung bean and P1 nucleases recognize the same site 5\u27 to hsp 26 and give the same general pattern of cleavage. All three nucleases show an initial cleavage of 88B13 DNA at this site at pH 5.5 but not at pH 6.5, indicating that the DNA structure there may be pH dependent in vitro
Social determinants of content selection in the age of (mis)information
Despite the enthusiastic rhetoric about the so called \emph{collective
intelligence}, conspiracy theories -- e.g. global warming induced by chemtrails
or the link between vaccines and autism -- find on the Web a natural medium for
their dissemination. Users preferentially consume information according to
their system of beliefs and the strife within users of opposite narratives may
result in heated debates. In this work we provide a genuine example of
information consumption from a sample of 1.2 million of Facebook Italian users.
We show by means of a thorough quantitative analysis that information
supporting different worldviews -- i.e. scientific and conspiracist news -- are
consumed in a comparable way by their respective users. Moreover, we measure
the effect of the exposure to 4709 evidently false information (satirical
version of conspiracy theses) and to 4502 debunking memes (information aiming
at contrasting unsubstantiated rumors) of the most polarized users of
conspiracy claims. We find that either contrasting or teasing consumers of
conspiracy narratives increases their probability to interact again with
unsubstantiated rumors.Comment: misinformation, collective narratives, crowd dynamics, information
spreadin
Reconstruction of the Primordial Power Spectrum by Direct Inversion
We introduce a new method for reconstructing the primordial power spectrum,
, directly from observations of the Cosmic Microwave Background (CMB). We
employ Singular Value Decomposition (SVD) to invert the radiation perturbation
transfer function. The degeneracy of the multipole to wavenumber
linear mapping is thus reduced. This enables the inversion to be carried out at
each point along a Monte Carlo Markov Chain (MCMC) exploration of the combined
and cosmological parameter space. We present best--fit obtained
with this method along with other cosmological parameters.Comment: 23 pages, 9 figure
Bounds from Primordial Black Holes with a Near Critical Collapse Initial Mass Function
Recent numerical evidence suggests that a mass spectrum of primordial black
holes (PBHs) is produced as a consequence of near critical gravitational
collapse. Assuming that these holes formed from the initial density
perturbations seeded by inflation, we calculate model independent upper bounds
on the mass variance at the reheating temperature by requiring the mass density
not exceed the critical density and the photon emission not exceed current
diffuse gamma-ray measurements. We then translate these results into bounds on
the spectral index n by utilizing the COBE data to normalize the mass variance
at large scales, assuming a constant power law, then scaling this result to the
reheating temperature. We find that our bounds on n differ substantially
(\delta n > 0.05) from those calculated using initial mass functions derived
under the assumption that the black hole mass is proportional to the horizon
mass at the collapse epoch. We also find a change in the shape of the diffuse
gamma-ray spectrum which results from the Hawking radiation. Finally, we study
the impact of a nonzero cosmological constant and find that the bounds on n are
strengthened considerably if the universe is indeed vacuum-energy dominated
today.Comment: 24 pages, REVTeX, 5 figures; minor typos fixed, two refs added,
version to be published in PR
First Results from the Arcminute Cosmology Bolometer Array Receiver
We review the first science results from the Arcminute Cosmology Bolometer
Array Receiver (ACBAR); a multifrequency millimeter-wave receiver optimized for
observations of the Cosmic Microwave Background (CMB) and the
Sunyaev-Zel'dovich (SZ) effect in clusters of galaxies. ACBAR was installed on
the 2 m Viper telescope at the South Pole in January 2001 and the results
presented here incorporate data through July 2002. We present the power
spectrum of the CMB at 150 GHz over the range \ell = 150 - 3000 measured by
ACBAR as well as estimates for the values of the cosmological parameters within
the context of Lambda-CDM models. We find that the inclusion of Omega_Lambda
greatly improves the fit to the power spectrum. We also observe a slight excess
of small-scale anisotropy at 150 GHz; if interpreted as power from the SZ
effect of unresolved clusters, the measured signal is consistent with CBI and
BIMA within the context of the SZ power spectrum models tested.Comment: To be published in the proceedings of "The Cosmic Microwave
Background and its Polarization", New Astronomy Reviews, (eds. S. Hanany and
K.A. Olive). 10 pages, 2 figure
Measuring CMB Polarization with BOOMERANG
BOOMERANG is a balloon-borne telescope designed for long duration (LDB)
flights around Antarctica. The second LDB Flight of BOOMERANG took place in
January 2003. The primary goal of this flight was to measure the polarization
of the CMB. The receiver uses polarization sensitive bolometers at 145 GHz.
Polarizing grids provide polarization sensitivity at 245 and 345 GHz. We
describe the BOOMERANG telescope noting changes made for 2003 LDB flight, and
discuss some of the issues involved in the measurement of polarization with
bolometers. Lastly, we report on the 2003 flight and provide an estimate of the
expected results.Comment: 12 pages, 8 figures, To be published in the proceedings of "The
Cosmic Microwave Background and its Polarization", New Astronomy Reviews,
(eds. S. Hanany and K.A. Olive). Fixed typos, and reformatted citation
AEROgui: A graphical user interface for the optical properties of aerosols
Atmospheric aerosols have an uncertain effect on climate and serious impacts on human health. The uncertainty in the aerosols' role on climate has several sources. First, aerosols have great spatial and temporal variability. The spatial variability arises from the fact that aerosols emitted in a certain place can travel thousands of kilometers, swept by the winds to modify the destination region's climate. The spatial variability also means that aerosols are inhomogeneously distributed in the vertical direction, which can lead to a differential effect on the energy balance depending on the aerosols' altitude. On the other hand, aerosols experience physical and chemical transformations in the time they spend in the atmosphere, commonly known as aging, which modifies its optical properties. These factors make necessary the use of two approaches for the study of the aerosol impact on climate: global aerosol models and satellite- and ground-based measurements. The disagreement between the estimates of the two approaches is the main cause of the climate uncertainty. One way to reduce climate uncertainty is to create new tools to simulate more realistic aerosol scenarios. We present a graphical user interface to obtain aerosol optical properties: extinction, scattering, and absorption coefficients; single-scattering albedo; asymmetry parameter; and aerosol optical depth. The tool can be used to obtain the optical properties of the external and internal mixture of several aerosol components. Interface outputs have successfully been compared to a black carbon plume and to aging mineral dust
Bayesian joint estimation of non-Gaussianity and the power spectrum
We propose a rigorous, non-perturbative, Bayesian framework which enables one
jointly to test Gaussianity and estimate the power spectrum of CMB
anisotropies. It makes use of the Hilbert space of an harmonic oscillator to
set up an exact likelihood function, dependent on the power spectrum and on a
set of parameters , which are zero for Gaussian processes. The latter
can be expressed as series of cumulants; indeed they perturbatively reduce to
cumulants. However they have the advantage that their variation is essentially
unconstrained. Any truncation(i.e.: finite set of ) therefore still
produces a proper distribution - something which cannot be said of the only
other such tool on offer, the Edgeworth expansion. We apply our method to Very
Small Array (VSA) simulations based on signal Gaussianity, showing that our
algorithm is indeed not biased.Comment: 11pages, 4 figures, submitted to MNRA
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