2,529 research outputs found
Microwave-to-optical conversion in a room-temperature Rb vapor with frequency-division multiplexing control
Coherent microwave-to-optical conversion is crucial for transferring quantum
information generated in the microwave domain to optical frequencies, where
propagation losses can be minimised. Among the various physical platforms that
have realized coherent microwave-to-optical transduction, those that use atoms
as transducers have shown rapid progress in recent years. In this paper we
report an experimental demonstration of coherent microwave-to-optical
conversion that maps a microwave signal to a large, tunable 550(30) MHz range
of optical frequencies using room-temperature Rb atoms. The
inhomogeneous Doppler broadening of the atomic vapor advantageously supports
the tunability of an input microwave channel to any optical frequency channel
within the Doppler width, along with simultaneous conversion of a multi-channel
input microwave field to corresponding optical channels. In addition, we
demonstrate phase-correlated amplitude control of select channels, resulting in
complete extinction of one of the channels, providing an analog to a frequency
domain beam splitter across five orders of magnitude in frequency. With
frequency-division multiplexing capability, multi-channel conversion, and
amplitude control of frequency channels, neutral atomic systems may be
effective quantum processors for quantum information encoded in frequency-bin
qubits
Maternal thyroid function and child educational attainment: prospective cohort study
Objective: To determine if first trimester maternal thyroid dysfunction is a critical determinant of child scholastic performance and overall educational attainment.
Design: Prospective cohort study.
Setting: Avon Longitudinal Study of Parents and Children cohort in the UK.
Participants: 4615 mother-child pairs with an available first trimester sample (median 10 weeks gestation, interquartile range 8-12).
Exposures: Free thyroxine, thyroid stimulating hormone, and thyroid peroxidase antibodies assessed as continuous measures and the seven clinical categories of maternal thyroid function.
Main outcome measures: Five age-specific national curriculum assessments in 3580 children at entry stage assessment at 54 months, increasing up to 4461 children at their final school assessment at age 15.
Results: No strong evidence of clinically meaningful associations of first trimester free thyroxine and thyroid stimulating hormone levels with entry stage assessment score or Standard Assessment Test scores at any of the key stages was found. Associations of maternal free thyroxine or thyroid stimulating hormone with the total number of General Certificates of Secondary Education (GCSEs) passed (range 0-16) were all close to the null: free thyroxine, rate ratio per pmol/L 1.00 (95% confidence interval 1.00 to 1.01); and thyroid stimulating hormone, rate ratio 0.98 (0.94 to 1.02). No important relationship was observed when more detailed capped scores of GCSEs allowing for both the number and grade of pass or when language, mathematics, and science performance were examined individually or when all educational assessments undertaken by an individual from school entry to leaving were considered. 200 (4.3%) mothers were newly identified as having hypothyroidism or subclinical hypothyroidism and 97 (2.1%) subclinical hyperthyroidism or hyperthyroidism. Children of mothers with thyroid dysfunction attained an equivalent number of GCSEs and equivalent grades as children of mothers with euthyroidism.
Conclusions: Maternal thyroid dysfunction in early pregnancy does not have a clinically important association with impaired child performance at school or educational achievement
An improved ontological representation of dendritic cells as a paradigm for all cell types
The Cell Ontology (CL) is designed to provide a standardized representation of cell types for data annotation. Currently, the CL employs multiple is_a relations, defining cell types in terms of histological, functional, and lineage properties, and the majority of definitions are written with sufficient generality to hold across multiple species. This approach limits the CLâs utility for cross-species data integration. To address this problem, we developed a method for the ontological representation of cells and applied this method to develop a dendritic cell ontology (DC-CL). DC-CL subtypes are delineated on the basis of surface protein expression, systematically including both species-general and species-specific types and optimizing DC-CL for the analysis of flow cytometry data. This approach brings benefits in the form of increased accuracy, support for reasoning, and interoperability with other ontology resources.
104. Barry Smith, âToward a Realistic Science of Environmentsâ, Ecological Psychology, 2009, 21 (2), April-June, 121-130.
Abstract: The perceptual psychologist J. J. Gibson embraces a radically externalistic view of mind and action. We have, for Gibson, not a Cartesian mind or soul, with its interior theater of contents and the consequent problem of explaining how this mind or soul and its psychological environment can succeed in grasping physical objects external to itself. Rather, we have a perceiving, acting organism, whose perceptions and actions are always already tuned to the parts and moments, the things and surfaces, of its external environment. We describe how on this basis Gibson sought to develop a realist science of environments which will be âconsistent with physics, mechanics, optics, acoustics, and chemistryâ
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Radiative absorption enhancements by black carbon controlled by particle-to-particle heterogeneity in composition.
Black carbon (BC) absorbs solar radiation, leading to a strong but uncertain warming effect on climate. A key challenge in modeling and quantifying BC's radiative effect on climate is predicting enhancements in light absorption that result from internal mixing between BC and other aerosol components. Modeling and laboratory studies show that BC, when mixed with other aerosol components, absorbs more strongly than pure, uncoated BC; however, some ambient observations suggest more variable and weaker absorption enhancement. We show that the lower-than-expected enhancements in ambient measurements result from a combination of two factors. First, the often used spherical, concentric core-shell approximation generally overestimates the absorption by BC. Second, and more importantly, inadequate consideration of heterogeneity in particle-to-particle composition engenders substantial overestimation in absorption by the total particle population, with greater heterogeneity associated with larger model-measurement differences. We show that accounting for these two effects-variability in per-particle composition and deviations from the core-shell approximation-reconciles absorption enhancement predictions with laboratory and field observations and resolves the apparent discrepancy. Furthermore, our consistent model framework provides a path forward for improving predictions of BC's radiative effect on climate
A Double-Mode RR Lyrae Star with a Strong Fundamental Mode Component
NSVS 5222076, a thirteenth magnitude star in the Northern Sky Variability
Survey, was identified by Oaster as a possible new double-mode RR Lyrae star.
We confirm the double-mode nature of NSVS 5222076, supplementing the survey
data with new V band photometry. NSVS 5222076 has a fundamental mode period of
0.4940 day and a first overtone period of 0.3668 day. Its fundamental mode
light curve has an amplitude twice as large as that of the first overtone mode,
a ratio very rarely seen. Data from the literature are used to discuss the
location in the Petersen diagram of double-mode RR Lyrae stars having strong
fundamental mode pulsation. Such stars tend to occur toward the short period
end of the Petersen diagram, and NSVS 5222976 is no exception to this rule.Comment: 14 pages, 4 figures, To be published in the March, 2006, issue of
PAS
Parameters affecting ion intensities in transmission-mode Direct Analysis in Real-Time mass spectrometry
A survey of the effect of temperature, transmission module material and analysis time on ion intensities in transmission mode direct analysis in real time mass spectrometry is presented. Ion intensity profiles obtained for two related compounds are similar when analysed separately but are very different when analysed as a mixture
Discovery of a new Transient X-ray Pulsar in the Small Magellanic Cloud
Rossi X-Ray Timing Explorer observations of the Small Magellanic Cloud have
revealed a previously unknown transient X-ray pulsar with a pulse period of
95s. Provisionally designated XTE SMC95, the pulsar was detected in three
Proportional Counter Array observations during an outburst spanning 4 weeks in
March/April 1999. The pulse profile is double peaked reaching a pulse fraction
\~0.8. The source is proposed as a Be/neutron star system on the basis of its
pulsations, transient nature and characteristically hard X-ray spectrum. The
2-10 keV X-ray luminosity implied by our observations is > 2x10^37 erg/s which
is consistent with that of normal outbursts seen in Galactic systems. This
discovery adds to the emerging picture of the SMC as containing an extremely
dense population of transient high mass X-ray binaries.Comment: Accepted by A&A. 7 pages, 6 figure
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