16,870 research outputs found
Optimising the assessment of cerebral autoregulation from black box models
Cerebral autoregulation (CA) mechanisms maintain blood flow approximately stable despite changes in arterial blood pressure. Mathematical models that characterise this system have been used extensively in the quantitative assessment of function/impairment of CA. Using spontaneous fluctuations in arterial blood pressure (ABP) as input and cerebral blood flow velocity (CBFV) as output, the autoregulatory mechanism can be modelled using linear and non-linear approaches, from which indexes can be extracted to provide an overall assessment of CA. Previous studies have considered a single – or at most a couple of measures, making it difficult to compare the performance of different CA parameters. We compare the performance of established autoregulatory parameters and propose novel measures. The key objective is to identify which model and index can best distinguish between normal and impaired CA. To this end 26 recordings of ABP and CBFV from normocapnia and hypercapnia (which temporarily impairs CA) in 13 healthy adults were analysed. In the absence of a ‘gold’ standard for the study of dynamic CA, lower inter- and intra-subject variability of the parameters in relation to the difference between normo- and hypercapnia were considered as criteria for identifying improved measures of CA. Significantly improved performance compared to some conventional approaches was achieved, with the simplest method emerging as probably the most promising for future studies
A study of the usefulness of Skylab EREP data for earth resources studies in Australia
There are no author-identified significant results in this report
A Minimum-Labeling Approach for Reconstructing Protein Networks across Multiple Conditions
The sheer amounts of biological data that are generated in recent years have
driven the development of network analysis tools to facilitate the
interpretation and representation of these data. A fundamental challenge in
this domain is the reconstruction of a protein-protein subnetwork that
underlies a process of interest from a genome-wide screen of associated genes.
Despite intense work in this area, current algorithmic approaches are largely
limited to analyzing a single screen and are, thus, unable to account for
information on condition-specific genes, or reveal the dynamics (over time or
condition) of the process in question. Here we propose a novel formulation for
network reconstruction from multiple-condition data and devise an efficient
integer program solution for it. We apply our algorithm to analyze the response
to influenza infection in humans over time as well as to analyze a pair of ER
export related screens in humans. By comparing to an extant, single-condition
tool we demonstrate the power of our new approach in integrating data from
multiple conditions in a compact and coherent manner, capturing the dynamics of
the underlying processes.Comment: Peer-reviewed and presented as part of the 13th Workshop on
Algorithms in Bioinformatics (WABI2013
Effectiveness of Hindman's theorem for bounded sums
We consider the strength and effective content of restricted versions of
Hindman's Theorem in which the number of colors is specified and the length of
the sums has a specified finite bound. Let denote the
assertion that for each -coloring of there is an infinite
set such that all sums for and have the same color. We prove that there is a
computable -coloring of such that there is no infinite
computable set such that all nonempty sums of at most elements of
have the same color. It follows that is not provable
in and in fact we show that it implies in
. We also show that there is a computable instance of
with all solutions computing . The proof of this
result shows that implies in
Signals from the silent: online predictors of non-success
Changes to student funding, in parallel with the introduction of new technologies into teaching and learning, and a blurring of traditional boundaries between full and part time study have brought an increased focus on retention in higher education. As more providers look towards offering online portfolio options, this is likely to increase; with some evidence that drop-out on online-led modules can be higher.
As many classroom-based behavioural indicators of student retention are reduced or absent in the online environment, institutions can be slower to understand that students are considering dropping out, with the first indication of problems being when withdrawal takes place.
This paper draws on data from online interactions among 3000 students studying an introductory Business Studies module at the Open University to identify early online indicators of potential drop-out. Findings suggest that both erratic interactions, and/or marked reduction in activity level from previously active students are predictors of subsequent withdrawal.
Existing demographic data (on age, gender, etc) used by the institution has historically allowed broad ‘at risk’ categories of student to be identified; coupling this information to some of the online behavioural indicators revealed through new tracking technology allows more precise targeting of individuals more promptly than historically. This may potentially change a student support model from reactive to proactive; allowing the institution to offer additional support as soon as such signs emerge which improve student retention.
Universities seeking to increase student retention may find early warning of vulnerable students useful in targeting appropriate interventions
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Time-constrained scenario-based practical examinations (TSPEs) – an alternative to OSCEs?
Assessing clinical competence in medical professionals typically involves both work-based assessment and simulated clinical examinations. Student veterinary nurses are assessed through the Nursing Progress Log during placement, then by means of practical examinations – objective structured clinical examinations (OSCEs). Time-constrained scenario-based practical examinations (TSPEs) are adapted from traditional OSCEs, including assessment of similar practical skills, but by means of a single patient scenario. This article introduces the theory behind using TSPEs and covers practical considerations for course teams considering adopting this assessment style
Measurements of positive ions and air-earth current density at Maitri, Antarctica
Simultaneous measurements of the small-, intermediate- and large- positive
ions and air earth current density made at a coastal station, Maitri at
Antarctica during January to February 2005, are reported. Although, small and
large positive ion concentrations do not show any systematic diurnal
variations, variations in them are almost similar to each other. On the other
hand, variations in intermediate positive ion concentrations are independent of
variations in the small/large positive ions and exhibit a diurnal variation
which is similar to that in atmospheric temperature on fair weather days with a
maximum during the day and minimum during the night hours. No such diurnal
variation in intermediate positive ion concentration is observed on cloudy days
when variations in them are also similar to those insmall/large positive ion
concentrations. Magnitude of diurnal variation in intermediate positive ion
concentration on fair weather days increases with the lowering of atmospheric
temperature in this season. Scavenging of ions by snowfall and trapping of Alha
- rays from the ground radioactivity by a thin layer of snow on ground, is
demonstrated from observations. Variations in intermediate positive ion
concentration are explained on the basis of the formation of new particles by
the photolytic nucleation process.Comment: 38 pages, 11 figure and 2 tabl
Optical alignment and spinning of laser-trapped microscopic particles
Light-induced rotation of absorbing microscopic particles by transfer of
angular momentum from light to the material raises the possibility of optically
driven micromachines. The phenomenon has been observed using elliptically
polarized laser beams or beams with helical phase structure. But it is
difficult to develop high power in such experiments because of overheating and
unwanted axial forces, limiting the achievable rotation rates to a few hertz.
This problem can in principle be overcome by using transparent particles,
transferring angular momentum by a mechanism first observed by Beth in 1936,
when he reported a tiny torque developed in a quartz waveplate due to the
change in polarization of transmitted light. Here we show that an optical
torque can be induced on microscopic birefringent particles of calcite held by
optical tweezers. Depending on the polarization of the incident beam, the
particles either become aligned with the plane of polarization (and thus can be
rotated through specified angles) or spin with constant rotation frequency.
Because these microscopic particles are transparent, they can be held in
three-dimensional optical traps at very high power without heating. We have
observed rotation rates in excess of 350 Hz.Comment: 4 pages, 4 figure
The nuclear spectrum of the radio galaxy NGC 5128 (Centaurus A)
We present near-infrared spectra of the nuclear disk in the nearby radio
galaxy NGC 5128 (Centaurus A). On the basis of the observed strengths of the [S
III] 0.9532um and [Fe II] 1.2567um lines, we classify NGC 5128 as a LINER.
Modeling of the strengths of these and additional lines suggests that the
nuclear region is powered by shocks rather than photoionization.Comment: 12 pages including 2 figures, accepted by ApJ Letter
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