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The Beagle landing site in Isidis Planitia
The Mars probe Beagle 2 will land in Isidis Planitia. This region satisfies the engineering constraints and has evidence for particularly volatile-rich subsoil. Isidis provides a suitable place for the lander to search for H2O and organic matter
MRI-based mechanical analysis of carotid atherosclerotic plaque using a material-property-mapping approach: A material-property-mapping method for plaque stress analysis
Background and objective
Atherosclerosis is a major underlying cause of cardiovascular conditions. In order to understand the biomechanics involved in the generation and rupture of atherosclerotic plaques, numerical analysis methods have been widely used. However, several factors limit the practical use of this information in a clinical setting. One of the key challenges in finite element analysis (FEA) is the reconstruction of the structure and the generation of a mesh. The complexity of the shapes associated with carotid plaques, including multiple components, makes the generation of meshes for biomechanical computation a difficult and in some cases, an impossible task. To address these challenges, in this study, we propose a novel material-property-mapping method for carotid atherosclerotic plaque stress analysis that aims to simplify the process.
Methods
The different carotid plaque components were identified and segmented using magnetic resonance imaging (MRI). For the mapping method, this information was used in conjunction with an in-house code, which provided the coordinates for each pixel/voxel and tissue type within a predetermined region of interest. These coordinates were utilized to assign specific material properties to each element in the volume mesh which provides a region of transition. The proposed method was subsequently compared to the traditional method, which involves creating a composed mesh for the arterial wall and plaque components, based on its location and size.
Results
The comparison between the proposed material-property-mapping method and the traditional method was performed in 2D, 3D structural-only, and fluid-structure interaction (FSI) simulations in terms of stress, wall shear stress (WSS), time-averaged WSS (TAWSS), and oscillatory shear index (OSI). The stress contours from both methods were found to be similar, although the proposed method tended to produce lower local maximum stress values. The WSS contours were also in agreement between the two methods. The velocity contours generated by the proposed method were verified against phase-contrast magnetic resonance imaging (MRI) measurements, for a higher level of confidence.
Conclusion
This study shows that a material-property-mapping method can effectively be used for analyzing the biomechanics of carotid plaques in a patient-specific manner. This approach has the potential to streamline the process of creating volume meshes for complex biological structures, such as carotid plaques, and to provide a more efficient and less labor-intensive method
The physiological and behavioral responses of steers to gaseous ammonia in simulated long distance transport by ship.
Ammonia (NH3) can accumulate in high density cattle accommodation during live export shipments and could potentially threaten the animals' health and welfare. The effects of 4 NH3 concentrations, control ( 0.05) on hematological parameters or body weight. Twenty-eight days after exposure to NH3, the steers' pulmonary macrophage activity and neutrophil levels had returned to normal. It was concluded that ammonia concentrations of 30 and 45 ppm induced temporary inflammatory responses which indicate an adverse effect on the welfare of steers
Usefulness of Parent-Completed ASQ for Neurodevelopmental Screening of Preterm Children at Five Years of Age.
International audienceINTRODUCTION: Preterm children are at greater risk of developmental impairment and require close follow-up for early and optimal medical care. Our goal was to examine use of the parent-completed Ages and Stages Questionnaire (ASQ) as a screening tool for neurodevelopmental disabilities in preterm infants at five years of age.PATIENTS AND METHODS: A total of 648 preterm children (285 were not distinctive for mild delay or normal development. In children with developmental delay, no difference was found when ASQ scores according to maternal education levels were analyzed.CONCLUSIONS: ASQ at five years is a simple and cost-effective tool that can detect severe developmental delay in preterm children regardless of maternal education level, while its capacity to identify children with mild delay appears to be more limited
A novel approach to Isoscaling: the role of the order parameter m = (N-Z)/A
Isoscaling is derived within a recently proposed modified Fisher model where
the free energy near the critical point is described by the Landau O(m^6)
theory. In this model m = (N-Z)/A is the order parameter, a consequence of (one
of) the symmetries of the nuclear Hamiltonian. Within this framework we show
that isoscaling depends mainly on this order parameter through the 'external
(conjugate) field' H. The external field is just given by the difference in
chemical potentials of the neutrons and protons of the two sources. To
distinguish from previously employed isoscaling relationships, this approach is
dubbed: m - scaling. We discuss the relationship between this framework and the
standard isoscaling formalism and point out some substantial differences in
interpretation of experimental results which might result. These should be
investigated further both theoretically and experimentally.Comment: 14 pages, 5 figure
Model of multifragmentation, Equation of State and phase transition
We consider a soluble model of multifragmentation which is similar in spirit
to many models which have been used to fit intermediate energy heavy ion
collision data. We draw a p-V diagram for the model and compare with a p-V
diagram obtained from a mean-field theory. We investigate the question of
chemical instability in the multifragmentation model. Phase transitions in the
model are discussed.Comment: Revtex, 9 pages including 6 figures: some change in the text and Fig.
Variations in water use by a mature mangrove of Avicennia germinans, French Guiana
In the tropical intertidal zones, little is known on water uptake by mangroves. Transpiration rates are generally measured at leaf level, but few studies exist on water use at tree or stand levels. The objective of this study was to measure sap flow in trees of different sizes to appreciate the range of variation in water use that may exist in a site dominated by 80% mature Avicennia germinans. The results showed that from the dry to the wet season the mean water use increased from 3.2 to 5.3 dm3 d−1 in small trees (DBH ∼ 13 cm), from 11.5 to 30.8 dm3 d−1 in medium trees (∼24 cm) and from 40.8 to 64.1 dm3 d−1 in large ones (∼45 cm). Sapwood remained active up to a depth of 8 cm with radial variations within the stem. Weak correlations were obtained with VPD and net radiation. This study confirmed that transpiration was larger under low levels of salinity. Water use at stand level (∼1900 living stems ha−1) was estimated to be in the range of 5.8 to 11.8 m3 ha−1 d−1 according to the season
Phase-Space analysis of Teleparallel Dark Energy
We perform a detailed dynamical analysis of the teleparallel dark energy
scenario, which is based on the teleparallel equivalent of General Relativity,
in which one adds a canonical scalar field, allowing also for a nonminimal
coupling with gravity. We find that the universe can result in the
quintessence-like, dark-energy-dominated solution, or to the stiff dark-energy
late-time attractor, similarly to standard quintessence. However, teleparallel
dark energy possesses an additional late-time solution, in which dark energy
behaves like a cosmological constant, independently of the specific values of
the model parameters. Finally, during the evolution the dark energy
equation-of-state parameter can be either above or below -1, offering a good
description for its observed dynamical behavior and its stabilization close to
the cosmological-constant value.Comment: 23 pages, 4 figures, 5 tables, version published at JCA
Search for varying constants of nature from astronomical observation of molecules
The status of searches for possible variation in the constants of nature from
astronomical observation of molecules is reviewed, focusing on the
dimensionless constant representing the proton-electron mass ratio
. The optical detection of H and CO molecules with large
ground-based telescopes (as the ESO-VLT and the Keck telescopes), as well as
the detection of H with the Cosmic Origins Spectrograph aboard the Hubble
Space Telescope is discussed in the context of varying constants, and in
connection to different theoretical scenarios. Radio astronomy provides an
alternative search strategy bearing the advantage that molecules as NH
(ammonia) and CHOH (methanol) can be used, which are much more sensitive to
a varying than diatomic molecules. Current constraints are
for redshift , corresponding to
look-back times of 10-12.5 Gyrs, and for
, corresponding to half the age of the Universe (both at 3
statistical significance). Existing bottlenecks and prospects for future
improvement with novel instrumentation are discussed.Comment: Contribution to Workshop "High Performance Clocks in Space" at the
International Space Science Institute, Bern 201
Functional diversity of chemokines and chemokine receptors in response to viral infection of the central nervous system.
Encounters with neurotropic viruses result in varied outcomes ranging from encephalitis, paralytic poliomyelitis or other serious consequences to relatively benign infection. One of the principal factors that control the outcome of infection is the localized tissue response and subsequent immune response directed against the invading toxic agent. It is the role of the immune system to contain and control the spread of virus infection in the central nervous system (CNS), and paradoxically, this response may also be pathologic. Chemokines are potent proinflammatory molecules whose expression within virally infected tissues is often associated with protection and/or pathology which correlates with migration and accumulation of immune cells. Indeed, studies with a neurotropic murine coronavirus, mouse hepatitis virus (MHV), have provided important insight into the functional roles of chemokines and chemokine receptors in participating in various aspects of host defense as well as disease development within the CNS. This chapter will highlight recent discoveries that have provided insight into the diverse biologic roles of chemokines and their receptors in coordinating immune responses following viral infection of the CNS
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