197,804 research outputs found
Charge and spin state readout of a double quantum dot coupled to a resonator
State readout is a key requirement for a quantum computer. For
semiconductor-based qubit devices it is usually accomplished using a separate
mesoscopic electrometer. Here we demonstrate a simple detection scheme in which
a radio-frequency resonant circuit coupled to a semiconductor double quantum
dot is used to probe its charge and spin states. These results demonstrate a
new non-invasive technique for measuring charge and spin states in quantum dot
systems without requiring a separate mesoscopic detector
The quest for stable circumbinary companions to post-common envelope sdB eclipsing binaries Does the observational evidence support their existence?
Context. Period variations have been detected in a number of eclipsing close
compact binary subdwarf B stars (sdBs) and these have often been interpreted as
caused by circumbinary massive planets or brown dwarfs. Various evolutionary
scenarios have been proposed for these stars, but a definite mechanism remains
to be established. Equally puzzling is the formation of these putative
circumbinary objects which must have formed either from the remaining post
common envelope circumbinary disk or survived its evolution. Aims. In this
paper we review the eclipse time variations (ETVs) exhibited by seven such
systems and explore if there is conclusive evidence that the ETVs observed over
the last two decades can reliably predict the presence of circumbinary bodies.
Methods. We report 246 new observations of the seven sdB systems made between
2013 September and 2017 July using a worldwide network of telescopes. We
combined our new data with previously published measurements to analyse the
ETVs of these systems. Results. Our data shows that period variations cannot be
modelled simply on the basis of circumbinary objects. This implies that more
complex processes may be taking place in these systems. From eclipse time
variations, it has historically been suggested that five of the seven binary
systems reported herein had circumbinary objects. Based on our recent
observations and analysis only three systems remain serious contenders. We find
agreement with other observers that at least a decade of observations is
required to establish reliable ephemeris. With longer observational baselines
it is quite conceivable that the data will support the circumbinary object
hypothesis of these binary systems. Also we generally agree with other
observers that larger values of (O-C) residuals are found with secondary
companions of spectral type M5/6 or earlier as a result of an Applegate type
mechanismComment: 15 pages, 13 figures, 4 tables. 3 tables archived on CD
Theoretical Interpretation of the Measurements of the Secondary Eclipses of TrES-1 and HD209458b
We calculate the planet-star flux-density ratios as a function of wavelength
from 0.5 microns to 25 microns for the transiting extrasolar giant planets
TrES-1 and HD209458b and compare them with the recent Spitzer/IRAC-MIPS
secondary eclipse data in the 4.5, 8.0, and 24 micron bands. With only three
data points and generic calibration issues, detailed conclusions are difficult,
but inferences regarding atmospheric composition, temperature, and global
circulation can be made. Our models reproduce the observations reasonably well,
but not perfectly, and we speculate on the theoretical consequences of
variations around our baseline models. One preliminary conclusion is that we
may be seeing in the data indications that the day side of a close-in
extrasolar giant planet is brighter in the mid-infrared than its night side,
unlike Jupiter and Saturn. This correspondence will be further tested when the
data anticipated in other Spitzer bands are acquired, and we make predictions
for what those data may show.Comment: 15 pages, including 3 color figures, submitted to the Astrophysical
Journa
Failure of non-vacuum steam sterilization processes for dental handpieces
Background:
Dental handpieces are used in critical and semi-critical operative interventions. Although a number of dental professional bodies recommend that dental handpieces are sterilized between patient use there is a lack of clarity and understanding of the effectiveness of different steam sterilization processes. The internal mechanisms of dental handpieces contain narrow lumens (0·8-2·3mm) which can impede the removal of air and ingress of saturated steam required to achieve sterilization conditions.
Aim:
To identify the extent of sterilization failure in dental handpieces using a non-vacuum process.
Methods:
In-vitro and in-vivo investigations were conducted on commonly used UK benchtop steam sterilizers and three different types of dental handpieces. The sterilization process was monitored inside the lumens of dental handpieces using thermometric (TM) methods (dataloggers), chemical indicators (CI) and biological indicators (BI).
Findings:
All three methods of assessing achievement of sterility within dental handpieces that had been exposed to non-vacuum sterilization conditions demonstrated a significant number of failures (CI=8/3,024(fails/n tests); BI=15/3,024; TM=56/56) compared to vacuum sterilization conditions (CI=2/1,944; BI=0/1,944; TM=0/36). The dental handpiece most likely to fail sterilization in the non-vacuum process was the surgical handpiece. Non-vacuum sterilizers located in general dental practice had a higher rate of sterilization failure (CI=25/1,620; BI=32/1,620; TM=56/56) with no failures in vacuum process.
Conclusion:
Non-vacuum downward/gravity displacement, type-N steam sterilizers are an unreliable method for sterilization of dental handpieces in general dental practice. The handpiece most likely to fail sterilization is the type most frequently used for surgical interventions
Observation of Entanglement-Dependent Two-Particle Holonomic Phase
Holonomic phases---geometric and topological---have long been an intriguing
aspect of physics. They are ubiquitous, ranging from observations in particle
physics to applications in fault tolerant quantum computing. However, their
exploration in particles sharing genuine quantum correlations lack in
observations. Here we experimentally demonstrate the holonomic phase of two
entangled-photons evolving locally, which nevertheless gives rise to an
entanglement-dependent phase. We observe its transition from geometric to
topological as the entanglement between the particles is tuned from zero to
maximal, and find this phase to behave more resilient to evolution changes with
increasing entanglement. Furthermore, we theoretically show that holonomic
phases can directly quantify the amount of quantum correlations between the two
particles. Our results open up a new avenue for observations of holonomic
phenomena in multi-particle entangled quantum systems.Comment: 8 pages, 6 figure
The 50-horsepower solar-powered irrigation facility located near Gila Bend, Arizona
The 50 horsepower solar powered irrigation facility near Gila Bend, Arizona which includes a Rankine cycle demonstrates the technical feasibility of solar powered pumping. The design of a facility specifically for the irrigation farmer using the technology that has been developed over the last four years is proposed
Investigating steam penetration using thermometric methods in dental handpieces with narrow internal lumens during sterilizing processes with non-vacuum or vacuum processes
Background:
Dental handpieces are required to be sterilized between patient use. Vacuum steam sterilization processes with fractionated pre/post-vacuum phases or unique cycles for specified medical devices, are required for hollow instruments with internal lumens to assure successful air removal. Entrapped air will compromise achievement of required sterilization conditions. Many countries and professional organisations still advocate non-vacuum sterilization processes for these devices.
Aim:
To investigate non-vacuum downward/gravity displacement, type-N steam sterilization of dental handpieces, using thermometric methods to measure time to achieve sterilization temperature at different handpiece locations.
Methods:
Measurements at different positions within air turbines were undertaken with thermocouples and dataloggers. Two examples of commonly used UK benchtop steam sterilizers were tested; a non-vacuum benchtop sterilizer (Little Sister 3, Eschmann, UK) and a vacuum benchtop sterilizer (Lisa, W&H, Austria). Each sterilizer cycle was completed with three handpieces and each cycle in triplicate.
Findings:
A total of 140 measurements inside dental handpiece lumens were recorded. We demonstrate that the non-vacuum process fails (time range 0-150 seconds) to reliably achieve sterilization temperatures within the time limit specified by the International standard (15 seconds equilibration time). The measurement point at the base of the handpiece failed in all test runs (n=9) to meet the standard. No failures were detected with the vacuum steam sterilization type B process with fractionated pre-vacuum and post-vacuum phases.
Conclusion:
Non-vacuum downward/gravity displacement, type-N steam sterilization processes are unreliable in achieving sterilization conditions inside dental handpieces and the base of the handpiece is the site most likely to fail
A rocket-borne electrostatic analyzer for measurement of energetic particle flux
A rocket-borne electrostatic analyzer experiment is described. It is used to measure energetic particle flux (0.9 to 14 keV) in the nighttime midlatitude E region. Energetic particle precipitation is believed to be a significant nighttime ionization source, particularly during times of high geomagnetic activity. The experiment was designed for use in the payload of a Nike Apache sounding rocket. The electrostatic analyzer employs two cylindrical parallel plates subtending a central angle of 90 deg. The voltage waveform supplied to the plates is a series of steps synchronized to the spin of the payload during flight. Both positive and negative voltages are provided, extending the detection capabilities of the instrument to both electrons and protons (and positive ions). The development, construction and operation of the instrument is described together with a preliminary evaluation of its performance in a rocket flight
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