1,082 research outputs found
Liquid sheet radiator
A new external flow radiator concept, the liquid sheet radiator (LSR), is introduced. The LSR sheet flow is described and an expression for the length/width (l/w), ratio is presented. A linear dependence of l/w on velocity is predicted that agrees with experimental results. Specific power for the LSR is calculated and is found to be nearly the same as the specific power of a liquid droplet radiator, (LDR). Several sheet thicknesses and widths were experimentally investigated. In no case was the flow found to be unstable
Avoiding Irreversibility: Engineering Resonant Conversions of Quantum Resources
© 2019 American Physical Society. We identify and explore the intriguing property of resource resonance arising within resource theories of entanglement, coherence, and thermodynamics. While the theories considered are reversible asymptotically, the same is generally not true in realistic scenarios where the available resources are bounded. The finite-size effects responsible for this irreversibility could potentially prohibit small quantum information processors or thermal machines from achieving their full potential. Nevertheless, we show here that by carefully engineering the resource interconversion process any such losses can be greatly suppressed. Our results are predicted by higher order expansions of the trade-off between the rate of resource interconversion and the achieved fidelity, and are verified by exact numerical optimizations of the appropriate underlying approximate majorization conditions
The prevalence of maternal medication ingestion in the antenatal period
The prevalence of ingestion of medication by pregnant women was recorded in 236 patients attending the antenatal clinics at New Somerset and Peninsula Maternity Hospitals. Patients were interviewed over two periods, 23 - 26 July and 2 - 12 December 1991. Of these women, 168 (71,2%) took a total of 283 drugs from 18 different categories. One hundred and forty women (59%) took prescribed and 68 (28,8%) non-prescribed medications. The most commonly used medicines were analgesics, cough and cold medicines, antibiotics, laxatives and antacids. Analgesics that contain aspirin constituted 13,8% of self-administered medicines and 2% of prescribed medicines. The most common sources of non-prescribed medication were pharmacies (60%), followed by supermarkets (32,5%). One hundred and sixty-two women (68,6%) received no advice on medication during their pregnancy. Of those who received advice, formal sources (doctor/nurse/ pharmacist/midwife) accounted for 56,8% and informal sources (family/friends /magazines) for 43,3% of advice; 59,7% of women did not know that certain medicines are unsafe during pregnancy.Our data indicate that pregnant women in Cape Town take a large number of medicines, - often without being aware of the potential adverse effects. This study shows the need for education in this regard, especially at antenatal clinics, pharmacies and supermarkets
Tailoring surface codes for highly biased noise
The surface code, with a simple modification, exhibits ultra-high error
correction thresholds when the noise is biased towards dephasing. Here, we
identify features of the surface code responsible for these ultra-high
thresholds. We provide strong evidence that the threshold error rate of the
surface code tracks the hashing bound exactly for all biases, and show how to
exploit these features to achieve significant improvement in logical failure
rate. First, we consider the infinite bias limit, meaning pure dephasing. We
prove that the error threshold of the modified surface code for pure dephasing
noise is , i.e., that all qubits are fully dephased, and this threshold
can be achieved by a polynomial time decoding algorithm. We demonstrate that
the sub-threshold behavior of the code depends critically on the precise shape
and boundary conditions of the code. That is, for rectangular surface codes
with standard rough/smooth open boundaries, it is controlled by the parameter
, where and are dimensions of the surface code lattice. We
demonstrate a significant improvement in logical failure rate with pure
dephasing for co-prime codes that have , and closely-related rotated
codes, which have a modified boundary. The effect is dramatic: the same logical
failure rate achievable with a square surface code and physical qubits can
be obtained with a co-prime or rotated surface code using only
physical qubits. Finally, we use approximate maximum likelihood decoding to
demonstrate that this improvement persists for a general Pauli noise biased
towards dephasing. In particular, comparing with a square surface code, we
observe a significant improvement in logical failure rate against biased noise
using a rotated surface code with approximately half the number of physical
qubits.Comment: 18+4 pages, 24 figures; v2 includes additional coauthor (ASD) and new
results on the performance of surface codes in the finite-bias regime,
obtained with beveled surface codes and an improved tensor network decoder;
v3 published versio
Three-component modelling of O-rich AGB star winds I. Effects of drift using forsterite
Stellar winds of cool and pulsating asymptotic giant branch (AGB) stars
enrich the interstellar medium with large amounts of processed elements and
various types of dust. We present the first study on the influence of
gas-to-dust drift on ab initio simulations of stellar winds of M-type stars
driven by radiation pressure on forsterite particles. Our study is based on our
radiation hydrodynamic model code T-800 that includes frequency-dependent
radiative transfer, dust extinction based on Mie scattering, grain growth and
ablation, gas-to-dust drift using one mean grain size, a piston that simulates
stellar pulsations, and an accurate high spatial resolution numerical scheme.
To enable this study, we calculated new gas opacities based on the ExoMol
database, and we extended the model code to handle the formation of minerals
that may form in M-type stars. We determine the effects of drift by comparing
drift models to our new and extant non-drift models. Three out of four new
drift models show high drift velocities, 87-310 km/s. Our new drift model
mass-loss rates are 1.7-13 per cent of the corresponding values of our
non-drift models, but compared to the results of two extant non-drift models
that use the same stellar parameters, these same values are 0.33-1.5 per cent.
Meanwhile, a comparison of other properties such as the expansion velocity and
grain size show similar values. Our results, which are based on
single-component forsterite particles, show that the inclusion of gas-to-drift
is of fundamental importance in stellar wind models driven by such transparent
grains. Assuming that the drift velocity is insignificant, properties such as
the mass-loss rate may be off from more realistic values by a factor of 50 or
more.Comment: 15 pages, 6 figures, accepted and in pres
Infrared spectra of TiO2 clusters for hot Jupiter atmospheres
Context. Clouds seem unavoidable in cool and dense environments, and hence,
are necessary to explain observations of exoplanet atmospheres, most recently
of WASP 96b with JWST. Understanding the formation of cloud condensation nuclei
in non-terrestrial environments is therefore crucial to develop accurate models
to interpret present and future observations. Aims. The goal of the paper is to
support observations with infrared spectra for (TiO2)N clusters in order to
study cloud formation in exoplanet atmospheres. Methods. Vibrational
frequencies are derived from quantum-chemical calculations for 123
(TiO2)-clusters and their isomers, and line-broadening mechanisms are
evaluated. Cluster spectra are calculated for several atmospheric levels for
two example exoplanet atmospheres (WASP 121b-like and WASP 96b-like) to
identify possible spectral fingerprints for cloud formation. Results.
Rotational motion of and transitions in the clusters cause significant line
broadening, so that individual vibrational lines are broadened beyond the
spectral resolution of the medium resolution mode of the JWST mid-infrared
instrument MIRI at R = 3000. However, each individual cluster isomer exhibits a
"fingerprint" IR spectrum. In particular, larger (TiO2)-clusters have
distinctly different spectra from smaller clusters. Morning and evening
terminator for the same planet can exhibit different total absorbances due to
different cluster sizes being more abundant. Conclusions. The largest
(TiO2)-clusters are not necessarily the most abundant (TiO2)-clusters in the
high-altitude regions of ultra-hot Jupiters, and the different cluster isomers
will contribute to the local absorbance. Planets with a considerable day-night
asymmetry will be most suitable to search for (TiO2)-cluster isomers in order
to improve cloud formation modelling.Comment: 8 pages, 8 figures, 1 table, accepted for publication in A&
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Analysis of differential protein expression in normal and neoplastic human breast epithelial cell lines
High resolution two dimensional get electrophoresis (2DE) and database analysis was used to establish protein expression patterns for cultured normal human mammary epithelial cells and thirteen breast cancer cell lines. The Human Breast Epithelial Cell database contains the 2DE protein patterns, including relative protein abundances, for each cell line, plus a composite pattern that contains all the common and specifically expressed proteins from all the cell lines. Significant differences in protein expression, both qualitative and quantitative, were observed not only between normal cells and tumor cells, but also among the tumor cell lines. Eight percent of the consistently detected proteins were found in significantly (P < 0.001) variable levels among the cell lines. Using a combination of immunostaining, comigration with purified protein, subcellular fractionation, and amino-terminal protein sequencing, we identified a subset of the differentially expressed proteins. These identified proteins include the cytoskeletal proteins actin, tubulin, vimentin, and cytokeratins. The cell lines can be classified into four distinct groups based on their intermediate filament protein profile. We also identified heat shock proteins; hsp27, hsp60, and hsp70 varied in abundance and in some cases in the relative phosphorylation levels among the cell lines. Finally, we identified IMP dehydrogenase in each of the cell lines, and found the levels of this enzyme in the tumor cell lines elevated 2- to 20-fold relative to the levels in normal cells
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