5,981 research outputs found
EMPIRE: A robust empirical reconstruction of solar irradiance variability
We present a new empirical model of total and spectral solar irradiance (TSI
and SSI) variability entitled EMPirical Irradiance REconstruction (EMPIRE). As
with existing empirical models, TSI and SSI variability is given by the linear
combination of solar activity indices. In empirical models, UV SSI variability
is usually determined by fitting the rotational variability in activity indices
to that in measurements. Such models have to date relied on ordinary least
squares regression, which ignores the uncertainty in the activity indices. In
an advance from earlier efforts, the uncertainty in the activity indices is
accounted for in EMPIRE by the application of an error-in-variables regression
scheme, making the resultant UV SSI variability more robust. The result is
consistent with observations and unprecedentedly, with that from other
modelling approaches, resolving the long-standing controversy between existing
empirical models and other types of models. We demonstrate that earlier
empirical models, by neglecting the uncertainty in activity indices,
underestimate UV SSI variability. The reconstruction of TSI and visible and IR
SSI from EMPIRE is also shown to be consistent with observations. The EMPIRE
reconstruction is of utility to climate studies as a more robust alternative to
earlier empirical reconstructions.Comment: J. Geophys. Res. (2017
Solar cycle variation in solar irradiance
The correlation between solar irradiance and the 11-year solar activity cycle
is evident in the body of measurements made from space, which extend over the
past four decades. Models relating variation in solar irradiance to
photospheric magnetism have made significant progress in explaining most of the
apparent trends in these observations. There are, however, persistent
discrepancies between different measurements and models in terms of the
absolute radiometry, secular variation and the spectral dependence of the solar
cycle variability. We present an overview of solar irradiance measurements and
models, and discuss the key challenges in reconciling the divergence between
the two
Male Partners' Involvement Towards Prenatal Screening and Diagnostic Testing for Down Syndrome
Introduction: Now, male partners' involvement in prenatal screening and diagnostic testing for Down syndrome is becoming increasingly recognized as well to ensure that parents are well informed of the risks and benefits of screening. The aim of study was to understand the degree of male partners' involvement during pregnancy in Singapore population. Methods: A cross-sectional survey of male partners' attending prenatal counseling was performed. The instrument used to measure the level of involvement is a self-assessment questionnaire that identifies the role of male partners with a Likert scale. Descriptive statistics was used to analyze data gained. Result: A total of 107 participants completed the questionnaire. Sixty-seven percent of male partners were found to have a highlevel of involvement while 32.7% was found to have a medium level of involvement. Most of them stated that women can pursue prenatal testing without their permission. Male partners found it more important for them to accompany their spouse to amniocentesis or CVS than to the Down syndrome screening test. When participants were asked about how much information about Down syndrome they sought prior to the appointment, how much discussion they had with their spouse about Down syndrome testing, and about whether they or their spouse should be the first person to receive test results, most stated that they were undecided. Conclusion: These results revealed that male partners were very well involved in the Down syndrome testing during pregnancy and future studies should assess possible underlying factors that influence male partners' involvement
Recent, independent and anthropogenic origins of Trypanosoma cruzi hybrids.
The single celled eukaryote Trypanosoma cruzi, a parasite transmitted by numerous species of triatomine bug in the Americas, causes Chagas disease in humans. T. cruzi generally reproduces asexually and appears to have a clonal population structure. However, two of the six major circulating genetic lineages, TcV and TcVI, are TcII-TcIII inter-lineage hybrids that are frequently isolated from humans in regions where chronic Chagas disease is particularly severe. Nevertheless, a prevalent view is that hybridisation events in T. cruzi were evolutionarily ancient and that active recombination is of little epidemiological importance. We analysed genotypes of hybrid and non-hybrid T. cruzi strains for markers representing three distinct evolutionary rates: nuclear GPI sequences (nβ=β88), mitochondrial COII-ND1 sequences (nβ=β107) and 28 polymorphic microsatellite loci (nβ=β35). Using Maximum Likelihood and Bayesian phylogenetic approaches we dated key evolutionary events in the T. cruzi clade including the emergence of hybrid lineages TcV and TcVI, which we estimated to have occurred within the last 60,000 years. We also found evidence for recent genetic exchange between TcIII and TcIV and between TcI and TcIV. These findings show that evolution of novel recombinants remains a potential epidemiological risk. The clearly distinguishable microsatellite genotypes of TcV and TcVI were highly heterozygous and displayed minimal intra-lineage diversity indicative of even earlier origins than sequence-based estimates. Natural hybrid genotypes resembled typical meiotic F1 progeny, however, evidence for mitochondrial introgression, absence of haploid forms and previous experimental crosses indicate that sexual reproduction in T. cruzi may involve alternatives to canonical meiosis. Overall, the data support two independent hybridisation events between TcII and TcIII and a recent, rapid spread of the hybrid progeny in domestic transmission cycles concomitant with, or as a result of, disruption of natural transmission cycles by human activities
Relations between entanglement, Bell-inequality violation and teleportation fidelity for the two-qubit X states
Based on the assumption that the receiver Bob can apply any unitary
transformation, Horodecki {\it et al.} [Phys. Lett. A {\bf 222}, 21 (1996)]
proved that any mixed two spin-1/2 state which violates the Bell-CHSH
inequality is useful for teleportation. Here, we further show that any X state
which violates the Bell-CHSH inequality can also be used for nonclassical
teleportation even if Bob can only perform the identity or the Pauli rotation
operations. Moreover, we showed that the maximal difference between the two
average fidelities achievable via Bob's arbitrary transformations and via the
sole identity or the Pauli rotation is 1/9.Comment: 5 pages, to be published in "Quantum Information Processing
Extensional viscosity of copper nanowire suspensions in an aqueous polymer solution
Suspensions of copper nanowires are emerging as new electronic inks for
next-generation flexible electronics. Using a novel surface acoustic wave
driven extensional flow technique we are able to perform currently lacking
analysis of these suspensions and their complex buffer. We observe extensional
viscosities from 3 mPas (1 mPas shear viscosity) to 37.2
Pas via changes in the suspension concentration, thus capturing low
viscosities that have been historically very challenging to measure. These
changes equate to an increase in the relative extensional viscosity of nearly
12,200 times at a volume fraction of just 0.027. We also find that interactions
between the wires and the necessary polymer additive affect the rheology
strongly. Polymer-induced elasticity shows a reduction as the buffer relaxation
time falls from 819 to 59 s above a critical particle concentration. The
results and technique presented here should aid in the future formulation of
these promising nanowire suspensions and their efficient application as inks
and coatings.Comment: 7 pages, 5 figures, under review for Soft Matter RS
Solar Irradiance Variability is Caused by the Magnetic Activity on the Solar Surface
The variation in the radiative output of the Sun, described in terms of solar
irradiance, is important to climatology. A common assumption is that solar
irradiance variability is driven by its surface magnetism. Verifying this
assumption has, however, been hampered by the fact that models of solar
irradiance variability based on solar surface magnetism have to be calibrated
to observed variability. Making use of realistic three-dimensional
magnetohydrodynamic simulations of the solar atmosphere and state-of-the-art
solar magnetograms from the Solar Dynamics Observatory, we present a model of
total solar irradiance (TSI) that does not require any such calibration. In
doing so, the modeled irradiance variability is entirely independent of the
observational record. (The absolute level is calibrated to the TSI record from
the Total Irradiance Monitor.) The model replicates 95% of the observed
variability between April 2010 and July 2016, leaving little scope for
alternative drivers of solar irradiance variability at least over the time
scales examined (days to years).Comment: Supplementary Materials;
https://journals.aps.org/prl/supplemental/10.1103/PhysRevLett.119.091102/supplementary_material_170801.pd
Reconstruction of spectral solar irradiance since 1700 from simulated magnetograms
We present a reconstruction of the spectral solar irradiance since 1700 using
the SATIRE-T2 (Spectral And Total Irradiance REconstructions for the Telescope
era version 2) model. This model uses as input magnetograms simulated with a
surface flux transport model fed with semi-synthetic records of emerging
sunspot groups. We used statistical relationships between the properties of
sunspot group emergence, such as the latitude, area, and tilt angle, and the
sunspot cycle strength and phase to produce semi-synthetic sunspot group
records starting in the year 1700. The semisynthetic records are fed into a
surface flux transport model to obtain daily simulated magnetograms that map
the distribution of the magnetic flux in active regions (sunspots and faculae)
and their decay products on the solar surface. The magnetic flux emerging in
ephemeral regions is accounted for separately based on the concept of extended
cycles whose length and amplitude are linked to those of the sunspot cycles
through the sunspot number. The magnetic flux in each surface component
(sunspots, faculae and network, and ephemeral regions) was used to compute the
spectral and total solar irradiance between the years 1700 and 2009. This
reconstruction is aimed at timescales of months or longer although the model
returns daily values. We found that SATIRE-T2, besides reproducing other
relevant observations such as the total magnetic flux, reconstructs the total
solar irradiance (TSI) on timescales of months or longer in good agreement with
the PMOD composite of observations, as well as with the reconstruction starting
in 1878 based on the RGO-SOON data. The model predicts an increase in the TSI
of 1.2[+0.2, -0.3] Wm-2 between 1700 and the present. The spectral irradiance
reconstruction is in good agreement with the UARS/SUSIM measurements as well as
the Lyman-alpha composite.Comment: 13 pages, 10 figure
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