16,898 research outputs found
Gypsy moths and American dog ticks: Space partners
An experiment intended for the space shuttle and designed to investigate the effects of weightlessness and total darkness on gypsy moth eggs and engorged American dog ticks is described. The objectives are: (1) to reevaluate the effects of zero gravity on the termination of diapause/hibernation of embryonated gypsy moth eggs, (2) to determine the effect of zero gravity on the ovipositions and subsequent hatch from engorged female American dog ticks that have been induced to diapause in the laboratory, and (3) to determine whether morphological or biochemical changes occur in the insects under examination. Results will be compared with those from a similar experiment conducted on Skylab 4
What metrics of harm are being captured in clinical trials involving talking treatments for young people? A systematic review of registered studies on the ISRCTN
Objective: The recording of harm and adverse events in psychological trials is essential, yet the types of harm being captured in trials for talking treatments involving children and young people have not been systematically investigated. The aim of this review was to determine how often harm and adverse events are recorded in talking treatments for children and young people, as well as the metrics that are being collected. Method: The ISRCTN was searched for trials involving talking therapies and young people. Of 355 entries, 69 met inclusion criteria. The authors of these records were contacted for further information, and additional searches were conducted of protocols and papers. Results: Findings show that around half of all records mentioned harm or adverse events in at least one piece of study documentation. Overall, metrics commonly collected are as follows: suicide, suicidal ideation and intent, self-harm, changes to clinical symptomology, and the need for further or additional care. Conclusions: Similar to the wider field of psychological interventions for mental health, the recording of harm and adverse events in children and young people tends to rely on a few key metrics, many of which are borrowed from drug trials. Examples of best practice have been highlighted, as well as recommendations for the progression of this research area
A heralded quantum gate between remote quantum memories
We demonstrate a probabilistic entangling quantum gate between two distant
trapped ytterbium ions. The gate is implemented between the hyperfine "clock"
state atomic qubits and mediated by the interference of two emitted photons
carrying frequency encoded qubits. Heralded by the coincidence detection of
these two photons, the gate has an average fidelity of 90+-2%. This entangling
gate together with single qubit operations is sufficient to generate large
entangled cluster states for scalable quantum computing
Nonlinear propagation of light in Dirac matter
The nonlinear interaction between intense laser light and a quantum plasma is
modeled by a collective Dirac equation coupled with the Maxwell equations. The
model is used to study the nonlinear propagation of relativistically intense
laser light in a quantum plasma including the electron spin-1/2 effect. The
relativistic effects due to the high-intensity laser light lead, in general, to
a downshift of the laser frequency, similar to a classical plasma where the
relativistic mass increase leads to self-induced transparency of laser light
and other associated effects. The electron spin-1/2 effects lead to a frequency
up- or downshift of the electromagnetic (EM) wave, depending on the spin state
of the plasma and the polarization of the EM wave. For laboratory solid density
plasmas, the spin-1/2 effects on the propagation of light are small, but they
may be significant in super-dense plasma in the core of white dwarf stars. We
also discuss extensions of the model to include kinetic effects of a
distribution of the electrons on the nonlinear propagation of EM waves in a
quantum plasma.Comment: 9 pages, 2 figure
Entanglement of Atomic Qubits using an Optical Frequency Comb
We demonstrate the use of an optical frequency comb to coherently control and
entangle atomic qubits. A train of off-resonant ultrafast laser pulses is used
to efficiently and coherently transfer population between electronic and
vibrational states of trapped atomic ions and implement an entangling quantum
logic gate with high fidelity. This technique can be extended to the high field
regime where operations can be performed faster than the trap frequency. This
general approach can be applied to more complex quantum systems, such as large
collections of interacting atoms or molecules.Comment: 4 pages, 5 figure
Identifying influential spreaders and efficiently estimating infection numbers in epidemic models: a walk counting approach
We introduce a new method to efficiently approximate the number of infections
resulting from a given initially-infected node in a network of susceptible
individuals. Our approach is based on counting the number of possible infection
walks of various lengths to each other node in the network. We analytically
study the properties of our method, in particular demonstrating different forms
for SIS and SIR disease spreading (e.g. under the SIR model our method counts
self-avoiding walks). In comparison to existing methods to infer the spreading
efficiency of different nodes in the network (based on degree, k-shell
decomposition analysis and different centrality measures), our method directly
considers the spreading process and, as such, is unique in providing estimation
of actual numbers of infections. Crucially, in simulating infections on various
real-world networks with the SIR model, we show that our walks-based method
improves the inference of effectiveness of nodes over a wide range of infection
rates compared to existing methods. We also analyse the trade-off between
estimate accuracy and computational cost, showing that the better accuracy here
can still be obtained at a comparable computational cost to other methods.Comment: 6 page
Exoplanetary atmosphere target selection in the era of comparative planetology
The large number of new planets expected from wide-area transit surveys means
that follow-up transmission spectroscopy studies of their atmospheres will be
limited by the availability of telescope assets. We argue that telescopes
covering a broad range of apertures will be required, with even 1m-class
instruments providing a potentially important contribution. Survey strategies
that employ automated target selection will enable robust population studies.
As part of such a strategy, we propose a decision metric to pair the best
target to the most suitable telescope, and demonstrate its effectiveness even
when only primary transit observables are available. Transmission spectroscopy
target selection need not therefore be impeded by the bottle-neck of requiring
prior follow-up observations to determine the planet mass. The decision metric
can be easily deployed within a distributed heterogeneous network of telescopes
equipped to undertake either broadband photometry or spectroscopy. We show how
the metric can be used either to optimise the observing strategy for a given
telescope (e.g. choice of filter) or to enable the selection of the best
telescope to optimise the overall sample size. Our decision metric can also
provide the basis for a selection function to help evaluate the statistical
completeness of follow-up transmission spectroscopy datasets. Finally, we
validate our metric by comparing its ranked set of targets against lists of
planets that have had their atmospheres successfully probed, and against some
existing prioritised exoplanet lists.Comment: 20 pages, 16 figures, 3 tables. Revision 3, accepted by MNRAS.
Improvements include always using planetary masses where available and
reliable, treatment for sky backgrounds and out-of-transit noise and a use
case for defocused photometr
Langmuir Wave Generation Through A Neutrino Beam Instability
A standard version of a kinetic instability for the generation of Langmuir
waves by a beam of electrons is adapted to describe the analogous instability
due to a beam of neutrinos. The interaction between a Langmuir wave and a
neutrino is treated in the one-loop approximation to lowest order in an
expansion in in the standard electroweak model.
It is shown that this kinetic instability is far too weak to occur in a
suggested application to the reheating of the plasma behind a stalled shock in
a type II supernova (SN). This theory is also used to test the validity of a
previous analysis of a reactive neutrino beam instability and various
shortcomings of this theory are noted. In particular, it is noted that
relativistic plasma effects have a significant effect on the calculated growth
rates, and that any theoretical description of neutrino-plasma interactions
must be based directly on the electroweak theory. The basic scalings discussed
in this paper suggest that a more complete investigation of neutrino-plasma
processes should be undertaken to look for an efficient process capable of
driving the stalled shock of a type II SN.Comment: 23 pages, incl. 5 postscript figure
Quantum Teleportation Between Distant Matter Qubits
Quantum teleportation is the faithful transfer of quantum states between
systems, relying on the prior establishment of entanglement and using only
classical communication during the transmission. We report teleportation of
quantum information between atomic quantum memories separated by about 1 meter.
A quantum bit stored in a single trapped ytterbium ion (Yb+) is teleported to a
second Yb+ atom with an average fidelity of 90% over a replete set of states.
The teleportation protocol is based on the heralded entanglement of the atoms
through interference and detection of photons emitted from each atom and guided
through optical fibers. This scheme may be used for scalable quantum
computation and quantum communication.Comment: 5 pages, 4 figure
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