2,088 research outputs found
Liquid Blood Phantoms to Validate NIRS Oximeters: Yeast Versus Nitrogen for Deoxygenation
Liquid blood phantoms are a tool to calibrate, test and compare near-infrared spectroscopy (NIRS) oximeters. They comprise a mixture of saline, blood and Intralipid, which is subsequently oxygenated and deoxygenated to assess the entire range of tissue oxygen saturation (StO) from 0% to 100%. The aim was to investigate two different deoxygenation methods: yeast versus nitrogen (N) bubbling. The phantom was oxygenated with pure O in both experiments, but deoxygenated by bubbling N in the first and by addition of yeast and glucose in the second experiment. A frequency domain NIRS instrument (OxiplexTS) was used as reference and to monitor changes in the reduced scattering coefficient (μ') of the phantom. Both deoxygenation methods yielded comparable StO values. The deoxygenation was slower by a factor 2.8 and μ' decreased faster when bubbling N. The constant bubbling of N mechanically stresses the Intralipid emulsion and causes a decrease in μ', probably due to aggregation of lipid droplets. Deoxygenation by N requires a more complex, air tight phantom. The gas flow cools the liquid and temperature needs to be monitored more closely. Consequently, we recommend using yeast for phantom deoxygenation
Complete classification of purely magnetic, non-rotating and non-accelerating perfect fluids
Recently the class of purely magnetic non-rotating dust spacetimes has been
shown to be empty (Wylleman, Class. Quant. Grav. 23, 2727). It turns out that
purely magnetic rotating dust models are subject to severe integrability
conditions as well. One of the consequences of the present paper is that also
rotating dust cannot be purely magnetic when it is of Petrov type D or when it
has a vanishing spatial gradient of the energy density. For purely magnetic and
non-rotating perfect fluids on the other hand, which have been fully classified
earlier for Petrov type D (Lozanovski, Class. Quant. Grav. 19, 6377), the fluid
is shown to be non-accelerating if and only if the spatial density gradient
vanishes. Under these conditions, a new and algebraically general solution is
found, which is unique up to a constant rescaling, which is spatially
homogeneous of Bianchi type , has degenerate shear and is of Petrov type
I( in the extended Arianrhod-McIntosh classification.
The metric and the equation of state are explicitly constructed and
properties of the model are briefly discussed. We finally situate it within the
class of normal geodesic flows with degenerate shear tensor.Comment: 12 pages; introduction partly rewritten, notation made more clear,
table of results adde
Diagnostic and predictive value of Doppler ultrasound for evaluation of the brain circulation in preterm infants: a systematic review
INTRODUCTION: Very and extremely preterm infants frequently have brain injury-related long-term neurodevelopmental problems. Altered perfusion, for example, seen in the context of a hemodynamically significant patent ductus arteriosus (PDA), has been linked to injury of the immature brain. However, a direct relation with outcome has not been reviewed systematically. METHODS: A systematic review was conducted to provide an overview of the value of different cerebral arterial blood flow parameters assessed by Doppler ultrasound, in relation to brain injury, to predict long-term neurodevelopmental outcome in preterm infants. RESULTS: In total, 23 studies were included. Because of heterogeneity of studies, a meta-analysis of results was not possible. All included studies on resistance index (RI) showed significantly higher values in subjects with a hemodynamically significant PDA. However, absolute differences in RI values were small. Studies using Doppler parameters to predict brain injury and long-term neurodevelopmental outcome were inconsistent. DISCUSSION: There is no clear evidence to support the routine determination of RI or other Doppler parameters in the cerebral arteries to predict brain injury and long-term neurodevelopmental outcome in the preterm infant. However, there is evidence that elevated RI can point to the presence of a hemodynamically significant PDA
Energetics of the Einstein-Rosen spacetime
A study covering some aspects of the Einstein--Rosen metric is presented. The
electric and magnetic parts of the Weyl tensor are calculated. It is shown that
there are no purely magnetic E--R spacetimes, and also that a purely electric
E--R spacetime is necessarily static. The geodesics equations are found and
circular ones are analyzed in detail. The super--Poynting and the
``Lagrangian'' Poynting vectors are calculated and their expressions are found
for two specific examples. It is shown that for a pulse--type solution, both
expressions describe an inward radially directed flow of energy, far behind the
wave front. The physical significance of such an effect is discussed.Comment: 19 pages Latex.References added and updated.To appear in
Int.J.Theor.Phy
Classical relativistic statistical mechanics: The case of a hot dilute plasma
Starting from predictive relativistic mechanics we develop a classical relativistic statistical mechanics. For a system of N particles, the basic distribution function depends, in addition to the 6N coordinates and velocities, on N times, instead of a single one as in the usual statistical mechanics. This generalized distribution function obeys N (instead of 1) continuity equations, which give rise to N Liouville equations in the case of a dilute plasma (i.e., to lowest, nonzero order in the charges). Hence, the Bogoliubov-Born-Green-Kirkwood-Yvon hierarchy for the reduced generalized distribution functions is derived. A relativistic Vlasov equation is obtained in this way. Thermal equilibrium is then considered for a dilute plasma. The calculation is explicitly worked out for a weakly relativistic plasma, up to order 1/c2, and known results are recovered
The sieve-element endoplasmic reticulum: A focal point of phytoplasma-host plant interaction?
The rough endoplasmic reticulum (r-ER) is of paramount importance for adaptive responses to biotic stresses due to an increased demand for de novo synthesis of immunity-related proteins and signaling components. In nucleate cells, disturbance of r-ER integrity and functionality leads to the “unfolded protein response” (UPR), which is an important component of innate plant immune signalling. In contrast to an abundance of reports on r-ER responses to biotic challenges, sieve-element endoplasmic reticulum (SE-ER) responses to phytoplasma infection have not been investigated. We found that morphological SE-ER changes, associated with phytoplasma infection, are accompanied by differential expression of genes encoding proteins involved in shaping and anchoring the reticulum. Phytoplasma infection also triggers an increased release of bZIP signals from the (SE-ER)/r-ER and consequent differential expression of UPR-related genes. The modified expression patterns seem to reflect a trade-off between survival of host cells, needed for the phytoplasmic biotrophic lifestyle, and phytoplasmas. Specialized plasmodesmata between sieve element and companion cell may provide a corridor for transfer of phytoplasma effectors inducing UPR-related gene expression in companion cells
Sexuality in patients with asthma and COPD
SummarySexual quality of life was examined in 55 outpatients with chronic obstructive pulmonary disease (COPD) and asthma, using disease-specific questionnaires. Compared to an age- and sex-matched norm group, male patients with COPD reported a significantly lower sexual quality of life on all dimensions of the questionnaire. Female patients with COPD reported a lower frequency of sexual intimacy and lower sexual quality of life overall. Patients with asthma reported sexual quality-of-life scores that were somewhat better than COPD patients but worse than the healthy control group. Patients reported that they did not discuss sexual quality-of-life issues with their physician. Sexuality needs to be discussed by the health care provider in the consultation in order to improve quality of life of patients with chronic respiratory disorders
Frame dragging, vorticity and electromagnetic fields in axially symmetric stationary spacetimes
We present a general study about the relation between the vorticity tensor
and the Poynting vector of the electromagnetic field for axially symmetric
stationary electrovacuum metrics. The obtained expressions allow to understand
the role of the Poynting vector in the dragging of inertial frames. The
particular case of the rotating massive charged magnetic dipole is analyzed in
detail. In addition, the electric and magnetic parts of the Weyl tensor are
calculated and the link between the later and the vorticity is established.
Then we show that, in the vacuum case, the necessary and sufficient condition
for the vanishing of the magnetic part is that the spacetime be static.Comment: 16 pages Latex. Some minor changes in the text and typos correcte
Maternal allopurinol during fetal hypoxia lowers cord blood levels of the brain injury marker S-100B
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