757 research outputs found
A single photoelectron transistor for quantum optical communications
A single photoelectron can be trapped and its photoelectric charge detected
by a source/drain channel in a transistor. Such a transistor photodetector can
be useful for flagging the safe arrival of a photon in a quantum repeater. The
electron trap can be photo-ionized and repeatedly reset for the arrival of
successive individual photons. This single photoelectron transistor (SPT)
operating at the lambda = 1.3 mu m tele-communication band, was demonstrated by
using a windowed-gate double-quantum-well InGaAs/InAlAs/InP heterostructure
that was designed to provide near-zero electron g-factor. The g-factor
engineering allows selection rules that would convert a photon's polarization
to an electron spin polarization. The safe arrival of the photo-electric charge
would trigger the commencement of the teleportation algorithm
A comprehensive evaluation of rhythm monitoring strategies for the detection of atrial fibrillation recurrence: insights from 647 continuously monitored patients and implications for monitoring after therapeutic interventions
No description supplie
Chromosomal integration of an avian oncogenic herpesvirus reveals telomeric preferences and evidence for lymphoma clonality
Abstract Background Herpesviruses are a major health concern for numerous organisms, including humans, causing both acute and chronic infections recurrent over an individual's lifespan. Marek's disease virus (MDV) is a highly contagious herpesvirus which causes a neoplastic condition in chicken populations. Several vertebrate-infecting herpesviruses have been shown to exist in an integrated state during latent periods of infection. However the status of MDV during latency has been a topic of debate. Results Here we employed high-resolution multi-color fluorescence in situ hybridization (FISH) to show integration of MDV at the telomeres of chicken chromosomes. Cytogenomic mapping of the chromosomal integrations allowed us to examine the clonal relationships among lymphomas within individuals, whereas analysis of tumors from multiple individuals indicated the potential for chromosomal preferences. Conclusions Our data highlight that substantive genome-level interactions between the virus and host exist, and merit consideration for their potential impact and role in key aspects of herpesvirus pathobiology including infection, latency, cellular transformation, latency-breaks and viral evolution
Observations of the Hubble Deep Field with the Infrared Space Observatory. I. Data reduction, maps and sky coverage
We present deep imaging at 6.7 micron and 15 micron from the CAM instrument
on the Infrared Space Observatory (ISO), centred on the Hubble Deep Field
(HDF). These are the deepest integrations published to date at these
wavelengths in any region of sky. We discuss the observation strategy and the
data reduction. The observed source density appears to approach the CAM
confusion limit at 15 micron, and fluctuations in the 6.7 micron sky background
may be identifiable with similar spatial fluctuations in the HDF galaxy counts.
ISO appears to be detecting comparable field galaxy populations to the HDF, and
our data yields strong evidence that future IR missions (such as SIRTF, FIRST
and WIRE) as well as SCUBA and millimetre arrays will easily detect field
galaxies out to comparably high redshifts.Comment: 7 pages, LaTeX (using mn.sty), 9 figures included as GIFs. Gzipped
Postscipt version available from http://artemis.ph.ic.ac.uk/hdf/papers/ps/.
Further information on ISO-HDF project can be found at
http://artemis.ph.ic.ac.uk/hdf
Observations of the Hubble Deep Field with the Infrared Space Observatory V. Spectral energy distributions starburst models and star formation history
We have modelled the spectral energy distributions of the 13 Hubble Deep Field (HDF) galaxies reliably detected by the Infrared Space Observatoiy (ISO). For two galaxies the emission detected by ISO is consistent with being starlight or the infrared 'cirrus' in the galaxies. For the remaining 11 galaxies there is a clear mid-infrared excess, which we interpret as emission from dust associated with a strong starburst. 10 of these galaxies are spirals or interacting pairs, while the remaining one is an elliptical with a prominent nucleus and broad emission lines. We give a new discussion of how the star formation rate can be deduced from the far-infrared luminosity, and derive star formation rates for these galaxies of 8-1000ø M¿ yr-1, where ø takes account of the uncertainty in the initial mass function. The HDF galaxies detected by ISO are clearly forming stars at a prodigious rate compared with nearby normal galaxies. We discuss the implications of our detections for the history of star and heavy element formation in the Universe. Although uncertainties in the calibration, reliability of source detection, associations and starburst models remain, it is clear that dust plays an important role in star formation out to redshift 1 at least
The Robinson-Trautman Type III Prolongation Structure Contains K
The minimal prolongation structure for the Robinson-Trautman equations of
Petrov type III is shown to always include the infinite-dimensional,
contragredient algebra, K, which is of infinite growth. Knowledge of
faithful representations of this algebra would allow the determination of
B\"acklund transformations to evolve new solutions.Comment: 20 pages, plain TeX, no figures, submitted to Commun. Math. Phy
Photoconductance Quantization in a Single-Photon Detector
We have made a single-photon detector that relies on photoconductive gain in
a narrow electron channel in an AlGaAs/GaAs 2-dimensional electron gas. Given
that the electron channel is 1-dimensional, the photo-induced conductance has
plateaus at multiples of the quantum conductance 2e/h. Super-imposed on
these broad conductance plateaus are many sharp, small, conductance steps
associated with single-photon absorption events that produce individual
photo-carriers. This type of photoconductive detector could measure a single
photon, while safely storing and protecting the spin degree of freedom of its
photo-carrier. This function is valuable for a quantum repeater that would
allow very long distance teleportation of quantum information.Comment: 4 pages, 4 figure
How often should we monitor for reliable detection of atrial fibrillation recurrence? Efficiency considerations and implications for study design
OBJECTIVE: Although atrial fibrillation (AF) recurrence is unpredictable in terms of onset and duration, current intermittent rhythm monitoring (IRM) diagnostic modalities are short-termed and discontinuous. The aim of the present study was to investigate the necessary IRM frequency required to reliably detect recurrence of various AF recurrence patterns. METHODS: The rhythm histories of 647 patients (mean AF burden: 12±22% of monitored time; 687 patient-years) with implantable continuous monitoring devices were reconstructed and analyzed. With the use of computationally intensive simulation, we evaluated the necessary IRM frequency to reliably detect AF recurrence of various AF phenotypes using IRM of various durations. RESULTS: The IRM frequency required for reliable AF detection depends on the amount and temporal aggregation of the AF recurrence (p<0.0001) as well as the duration of the IRM (p<0.001). Reliable detection (>95% sensitivity) of AF recurrence required higher IRM frequencies (>12 24-hour; >6 7-day; >4 14-day; >3 30-day IRM per year; p<0.0001) than currently recommended. Lower IRM frequencies will under-detect AF recurrence and introduce significant bias in the evaluation of therapeutic interventions. More frequent but of shorter duration, IRMs (24-hour) are significantly more time effective (sensitivity per monitored time) than a fewer number of longer IRM durations (p<0.0001). CONCLUSIONS: Reliable AF recurrence detection requires higher IRM frequencies than currently recommended. Current IRM frequency recommendations will fail to diagnose a significant proportion of patients. Shorter duration but more frequent IRM strategies are significantly more efficient than longer IRM durations. CLINICAL TRIAL REGISTRATION URL: Unique identifier: NCT00806689
The Mass Function of an X-Ray Flux-Limited Sample of Galaxy Clusters
A new X-ray selected and X-ray flux-limited galaxy cluster sample is
presented. Based on the ROSAT All-Sky Survey the 63 brightest clusters with
galactic latitude |bII| >= 20 deg and flux fx(0.1-2.4 keV) >= 2 * 10^{-11}
ergs/s/cm^2 have been compiled. Gravitational masses have been determined
utilizing intracluster gas density profiles, derived mainly from ROSAT PSPC
pointed observations, and gas temperatures, as published mainly from ASCA
observations, assuming hydrostatic equilibrium. This sample and an extended
sample of 106 galaxy clusters is used to establish the X-ray
luminosity--gravitational mass relation. From the complete sample the galaxy
cluster mass function is determined and used to constrain the mean cosmic
matter density and the amplitude of mass fluctuations. Comparison to
Press--Schechter type model mass functions in the framework of Cold Dark Matter
cosmological models and a Harrison--Zeldovich initial density fluctuation
spectrum yields the constraints OmegaM = 0.12^{+0.06}_{-0.04} and sigma8 =
0.96^{+0.15}_{-0.12} (90% c.l.). Various possible systematic uncertainties are
quantified. Adding all identified systematic uncertainties to the statistical
uncertainty in a worst case fashion results in an upper limit OmegaM < 0.31.
For comparison to previous results a relation sigma8 = 0.43 OmegaM^{-0.38} is
derived. The mass function is integrated to show that the contribution of mass
bound within virialized cluster regions to the total matter density is small,
i.e., OmegaCluster = 0.012^{+0.003}_{-0.004} for cluster masses larger than
6.4^{+0.7}_{-0.6} * 10^{13} h_{50}^{-1} Msun.Comment: 35 pages; accepted for publication in The Astrophysical Journal; this
and related papers, supplementary information, as well as electronic files of
the tables given in this paper are available at
http://www.astro.virginia.edu/~thr4f
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