727 research outputs found
Stability of postmortem methemoglobin: Artifactual changes caused by storage conditions.
Hemoglobin is the protein in red blood cells that carries and distributes oxygen to the body. Methemoglobinemia is a blood disorder in which an abnormal amount of methemoglobin (MetHb), a form of hemoglobin (Hb), is produced from either inadequate MetHb reductase activity or too much MetHb production or by exposure to oxidizing agents. This could lead to anoxia and death if it is not treated. However, this parameter has not been investigated as a valid post-mortem indicator because random MetHb levels have been observed in various studies: MetHb increases can be observed due to autoxidation during storage, and MetHb decreases can be observed due to MetHb reductase or microbial activity in post-mortem samples. MetHb variations can also come from the blood state and can interfere in the optical measurements of MetHb. We have studied the post-mortem MetHb concentrations according to various storage conditions. Based on our results, both the post-mortem delay and the delay before analysis should be reduced whenever possible to avoid changes in MetHb. If the analysis is delayed for a short period of time (two weeks), the blood sample taken at autopsy should not be frozen but collected in EDTA preservative and stored under refrigeration (4-6°C) until analysis. If the analysis is delayed for a longer period (more than two weeks), the blood sample should be frozen with cryoprotectant at -80°C or -196°C
Ultra-low pressure sensor for neonatal resuscitator
AbstractA Venturi-type flow sensor has been designed and fabricated for neonatal respiratory assistance to control airway pressure and tidal volume. As the low flow range and sensing principle require the measurement of correspondingly very low pressures, a very responsive sensor, based on a polymer membrane acting onto a piezoresistive cantilever force sensor based on low-temperature co-fired ceramic (LTCC), was developed. This paper details the 3D modelling, manufacture, assembly and characterisation of the sensor. Compared to expensive and fragile MEMS-based devices, this sensor, based on LTCC, thick-film technology and polymer parts, provides an accurate and robust, yet low-cost alternative
Matrix permanent and quantum entanglement of permutation invariant states
We point out that a geometric measure of quantum entanglement is related to
the matrix permanent when restricted to permutation invariant states. This
connection allows us to interpret the permanent as an angle between vectors. By
employing a recently introduced permanent inequality by Carlen, Loss and Lieb,
we can prove explicit formulas of the geometric measure for permutation
invariant basis states in a simple way.Comment: 10 page
Temperatures experienced by fresh-cut leafy greens during retail storage and display
There has been limited published work in the United States on temperature profiling of fresh-cut, bagged leafy greens during their transport, retail storage, and retail display. This study utilized temperature monitors placed in backrooms and display cases at nine supermarkets located in southern California: the Central Coast (Santa Barbara to Los Osos), Greater Los Angeles (Burbank area), and Greater Palm Desert. Sensors were installed midway along each 8-foot display case section containing fresh-cut leafy greens. Monitors were placed at the front and back of shelves and in the lower bin. In storage rooms, sensors were placed 4 feet from the floor in each corner. High and low temperature abuse occurred in retail display cases, with slightly more than 40% of the sensors indicating temperatures \u3e7.22°C, and 17% of the sensors indicating temperatures \u3c-0.17°C, for at least 5% of the time. Temperatures in storage rooms were rarely too low, but were often too high: slightly more than 58% of the sensors indicated temperatures \u3e7.22°C more than 5% of the time, and five sensors measured continuous temperatures \u3e7.22°C for nearly a year. Overall, most temperature abuse of pre-cut leafy greens at the retail level occurred during backroom storage. This study should be expanded to include major grocery chains in cities across the United States in order to verify these results
Interpretable Anomaly Detection in Echocardiograms with Dynamic Variational Trajectory Models
We propose a novel anomaly detection method for echocardiogram videos. The
introduced method takes advantage of the periodic nature of the heart cycle to
learn three variants of a variational latent trajectory model (TVAE). While the
first two variants (TVAE-C and TVAE-R) model strict periodic movements of the
heart, the third (TVAE-S) is more general and allows shifts in the spatial
representation throughout the video. All models are trained on the healthy
samples of a novel in-house dataset of infant echocardiogram videos consisting
of multiple chamber views to learn a normative prior of the healthy population.
During inference, maximum a posteriori (MAP) based anomaly detection is
performed to detect out-of-distribution samples in our dataset. The proposed
method reliably identifies severe congenital heart defects, such as Ebstein's
Anomaly or Shone-complex. Moreover, it achieves superior performance over
MAP-based anomaly detection with standard variational autoencoders when
detecting pulmonary hypertension and right ventricular dilation. Finally, we
demonstrate that the proposed method enables interpretable explanations of its
output through heatmaps highlighting the regions corresponding to anomalous
heart structures.Comment: accepted at IMLH workshop ICML 202
Families with infants: a general approach to solve hard partition problems
We introduce a general approach for solving partition problems where the goal
is to represent a given set as a union (either disjoint or not) of subsets
satisfying certain properties. Many NP-hard problems can be naturally stated as
such partition problems. We show that if one can find a large enough system of
so-called families with infants for a given problem, then this problem can be
solved faster than by a straightforward algorithm. We use this approach to
improve known bounds for several NP-hard problems as well as to simplify the
proofs of several known results.
For the chromatic number problem we present an algorithm with
time and exponential space for graphs of average
degree . This improves the algorithm by Bj\"{o}rklund et al. [Theory Comput.
Syst. 2010] that works for graphs of bounded maximum (as opposed to average)
degree and closes an open problem stated by Cygan and Pilipczuk [ICALP 2013].
For the traveling salesman problem we give an algorithm working in
time and polynomial space for graphs of average
degree . The previously known results of this kind is a polyspace algorithm
by Bj\"{o}rklund et al. [ICALP 2008] for graphs of bounded maximum degree and
an exponential space algorithm for bounded average degree by Cygan and
Pilipczuk [ICALP 2013].
For counting perfect matching in graphs of average degree~ we present an
algorithm with running time and polynomial
space. Recent algorithms of this kind due to Cygan, Pilipczuk [ICALP 2013] and
Izumi, Wadayama [FOCS 2012] (for bipartite graphs only) use exponential space.Comment: 18 pages, a revised version of this paper is available at
http://arxiv.org/abs/1410.220
Tunneling-percolation origin of nonuniversality: theory and experiments
A vast class of disordered conducting-insulating compounds close to the
percolation threshold is characterized by nonuniversal values of transport
critical exponent t, in disagreement with the standard theory of percolation
which predicts t = 2.0 for all three dimensional systems. Various models have
been proposed in order to explain the origin of such universality breakdown.
Among them, the tunneling-percolation model calls into play tunneling processes
between conducting particles which, under some general circumstances, could
lead to transport exponents dependent of the mean tunneling distance a. The
validity of such theory could be tested by changing the parameter a by means of
an applied mechanical strain. We have applied this idea to universal and
nonuniversal RuO2-glass composites. We show that when t > 2 the measured
piezoresistive response \Gamma, i. e., the relative change of resistivity under
applied strain, diverges logarithmically at the percolation threshold, while
for t = 2, \Gamma does not show an appreciable dependence upon the RuO2 volume
fraction. These results are consistent with a mean tunneling dependence of the
nonuniversal transport exponent as predicted by the tunneling-percolation
model. The experimental results are compared with analytical and numerical
calculations on a random-resistor network model of tunneling-percolation.Comment: 13 pages, 12 figure
Longitudinal and transversal piezoresistive response of granular metals
In this paper, we study the piezoresistive response and its anisotropy for a
bond percolation model of granular metals. Both effective medium results and
numerical Monte Carlo calculations of finite simple cubic networks show that
the piezoresistive anisotropy is a strongly dependent function of bond
probability p and of bond conductance distribution width \Delta g. We find that
piezoresistive anisotropy is strongly suppressed as p is reduced and/or \Delta
g is enhanced and that it vanishes at the percolation thresold p=p_c. We argue
that a measurement of the piezoresistive anisotropy could be a sensitive tool
to estimate critical metallic concentrations in real granular metals.Comment: 14 pages, 7 eps figure
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