11,027 research outputs found
Towards predicting post-editing productivity
Machine translation (MT) quality is generally measured via automatic metrics, producing scores that have no meaning for translators who are required to post-edit MT output or for project managers who have to plan and budget for transla- tion projects. This paper investigates correlations between two such automatic metrics (general text matcher and translation edit rate) and post-editing productivity. For the purposes of this paper, productivity is measured via processing speed and cognitive measures of effort using eye tracking as a tool. Processing speed, average fixation time and count are found to correlate well with the scores for groups of segments. Segments with high GTM and TER scores require substantially less time and cognitive effort than medium or low-scoring segments. Future research involving score thresholds and confidence estimation is suggested
Observation of quantum interference as a function of Berry's phase in a complex Hadamard optical network
Emerging models of quantum computation driven by multi-photon quantum
interference, while not universal, may offer an exponential advantage over
classical computers for certain problems. Implementing these circuits via
geometric phase gates could mitigate requirements for error correction to
achieve fault tolerance while retaining their relative physical simplicity. We
report an experiment in which a geometric phase is embedded in an optical
network with no closed-loops, enabling quantum interference between two photons
as a function of the phase.Comment: Comments welcom
An All Optical Fibre Quantum Controlled-NOT Gate
We report the first experimental demonstration of an optical controlled-NOT
gate constructed entirely in fibre. We operate the gate using two heralded
optical fibre single photon sources and find an average logical fidelity of 90%
and an average process fidelity of 0.83<F<0.91. On the basis of a simple model
we are able to conclude that imperfections are primarily due to the photon
sources, meaning that the gate itself works with very high fidelity.Comment: 4 pages, 4 figures, comments welcom
Dynamics of the Lyman alpha and C IV emitting gas in 3C 273
In this paper we study the variability properties of the Lyman alpha and C IV
emission lines in 3C273 using archival IUE observations. Our data show for the
first time the existence of variability on time scales of several years. We
study the spatial distribution and the velocity field of the emitting gas by
performing detailed analyses on the line variability using correlations, 1D and
2D response functions, and principal component analysis. In both lines we find
evidence for two components, one which has the dynamic properties of gas in
Keplerian motion around a black hole with a mass of the order of 10^9 Mo, and
one which is characterized by high, blue-shifted velocities at large lag. There
is no indication of the presence of optically thick emission medium neither in
the Lya, nor in the Civ response functions. The component characterized by
blue-shifted velocities, which is comparatively much stronger in Civ than in
Lya, is more or less compatible with being the result of gas falling towards
the central black hole with free-fall acceleration. We propose however that the
line emission at high, blue-shifted velocities is better explained in terms of
entrainment of gas clouds by the jet. This gas is therefore probably
collisionally excited as a result of heating due to the intense infrared
radiation from the jet, which would explain the strength of this component in
Civ relative to Lya. This phenomenon might be a signature of disk-jet
interaction.Comment: 16 pages, 10 figures. Accepted for publication in ApJ. Uses aaste
A study of sex difference in infant mortality in UK pediatric intensive care admissions over an 11-year period
Within the UK, child mortality from all causes has declined for all ages over the last three decades. However, distinct inequality remains, as child mortality rates are generally found to be higher in males. A significant proportion of childhood deaths in the UK occur in Paediatric Intensive Care Units (PICU). We studied the association of sex with infant mortality in PICUs. We included all infants (0 to 12 months old) admitted to UK PICUs from 01/01/2005 to 31/12/2015 using the Paediatric Intensive Care Audit Network (PICANet) dataset. We considered first admissions to PICU and fitted a cause-specific-hazard-ratio (CSHR) model, and a logistic model to estimate the adjusted association between sex and mortality in PICU. Pre-defined subgroups were children less than 56-days old, and those with a primary diagnosis of infection. Of 71,243 cases, 1,411/29,520 (4.8%) of females, and 1,809/41,723 (4.3%) of males died. The adjusted male/female CSHR was 0.87 (95%-CI 0.81 to 0.92) representing a 13% higher risk of death for females. The adjusted OR for male to female mortality is 0.86 (95%-CI 0.80 to 0.93). Analyses in subgroups yielded similar findings. In our analysis, female infants have a higher rate of PICU mortality compared to male infants
STM characterization of the Si-P heterodimer
We use scanning tunneling microscopy (STM) and Auger electron spectroscopy to
study the behavior of adsorbed phosphine (PH) on Si(001), as a function
of annealing temperature, paying particular attention to the formation of the
Si-P heterodimer. Dosing the Si(001) surface with 0.002 Langmuirs of
PH results in the adsorption of PH (x=2,3) onto the surface and
some etching of Si to form individual Si ad-dimers. Annealing to 350C
results in the incorporation of P into the surface layer to form Si-P
heterodimers and the formation of short 1-dimensional Si dimer chains and
monohydrides. In filled state STM images, isolated Si-P heterodimers appear as
zig-zag features on the surface due to the static dimer buckling induced by the
heterodimer. In the presence of a moderate coverage of monohydrides this static
buckling is lifted, rending the Si-P heterodimers invisible in filled state
images. However, we find that we can image the heterodimer at all H coverages
using empty state imaging. The ability to identify single P atoms incorporated
into Si(001) will be invaluable in the development of nanoscale electronic
devices based on controlled atomic-scale doping of Si.Comment: 6 pages, 4 figures (only 72dpi
A simple scheme for expanding photonic cluster states for quantum information
We show how an entangled cluster state encoded in the polarization of single
photons can be straightforwardly expanded by deterministically entangling
additional qubits encoded in the path degree of freedom of the constituent
photons. This can be achieved using a polarization--path controlled-phase gate.
We experimentally demonstrate a practical and stable realization of this
approach by using a Sagnac interferometer to entangle a path qubit and
polarization qubit on a single photon. We demonstrate precise control over
phase of the path qubit to change the measurement basis and experimentally
demonstrate properties of measurement-based quantum computing using a 2 photon,
3 qubit cluster state
Molecular Line Observations of Infrared Dark Clouds: Seeking the Precursors to Intermediate and Massive Star Formation
We have identified 41 infrared dark clouds from the 8 micron maps of the
Midcourse Space Experiment (MSX), selected to be found within one square degree
areas centered on known ultracompact HII regions. We have mapped these infrared
dark clouds in N2H+(1-0), CS(2-1) and C18O(1-0) emission using the Five College
Radio Astronomy Observatory. The maps of the different species often show
striking differences in morphologies, indicating differences in evolutionary
state and/or the presence of undetected, deeply embedded protostars. We derive
an average mass for these clouds using N2H+ column densities of ~2500 solar
masses, a value comparable to that found in previous studies of high mass star
forming cores using other mass tracers. The linewidths of these clouds are
typically ~2.0 - 2.9 km/s. Based on the fact that they are dark at 8 micron,
compact, massive, and have large velocity dispersions, we suggest that these
clouds may be the precursor sites of intermediate and high mass star formation.Comment: Accepted to ApJS, 22 pages, 10 pages of figures. For full-resolution
images, see http://www.astro.lsa.umich.edu/~seragan/pubs/fcrao/figures.tar.g
Geochronological constraints from zircon on the evolution of Himalayan UHP rocks
Abstract HKT-ISTP 2013
A
Optimal search strategies for hidden targets
What is the fastest way of finding a randomly hidden target? This question of
general relevance is of vital importance for foraging animals. Experimental
observations reveal that the search behaviour of foragers is generally
intermittent: active search phases randomly alternate with phases of fast
ballistic motion. In this letter, we study the efficiency of this type of two
states search strategies, by calculating analytically the mean first passage
time at the target. We model the perception mecanism involved in the active
search phase by a diffusive process. In this framework, we show that the search
strategy is optimal when the average duration of "motion phases" varies like
the power either 3/5 or 2/3 of the average duration of "search phases",
depending on the regime. This scaling accounts for experimental data over a
wide range of species, which suggests that the kinetics of search trajectories
is a determining factor optimized by foragers and that the perception activity
is adequately described by a diffusion process.Comment: 4 pages, 5 figures. to appear in Phys. Rev. Let
- …