Some viruses (e.g., human immunodeficiency virus 1 and severe acute respiratory syndrome coronavirus 2) have been experimentally proposed to accelerate features of human aging and of cellular senescence.
View Article and Find Full Text PDFThe genetic roots of the diverse paces and shapes of ageing and of the large variations in longevity observed across the tree of life are poorly understood. Indeed, pathways associated with ageing/longevity are incompletely known, both in terms of their constitutive genes/proteins and of their molecular interactions. Moreover, there is limited overlap between the genes constituting these pathways across mammals.
View Article and Find Full Text PDFCardiac imaging has a pivotal role in the prevention, diagnosis and treatment of ischaemic heart disease. SPECT is most commonly used for clinical myocardial perfusion imaging, whereas PET is the clinical reference standard for the quantification of myocardial perfusion. MRI does not involve exposure to ionizing radiation, similar to echocardiography, which can be performed at the bedside.
View Article and Find Full Text PDFPurpose: Bolus-based dynamic contrast agent (CA) perfusion measurements of the heart are subject to systematic errors due to CA bolus dispersion in the coronary arteries. To better understand these effects on quantification of myocardial blood flow and myocardial perfusion reserve (MPR), an in-silico model of the coronary arteries down to the pre-arteriolar vessels has been developed.
Methods: In this work, a computational fluid dynamics analysis is performed to investigate these errors on the basis of realistic 3D models of the left and right porcine coronary artery trees, including vessels at the pre-arteriolar level.
In this paper, I contrast two mathematically equivalent ways of modeling the evolution of altruism, namely the classical inclusive fitness approach and a more recent, "direct fitness" approach. Though both are usually considered by evolutionists as mere different ways of representing the same causal process (i.e.
View Article and Find Full Text PDFNatural selection is often envisaged as the ultimate cause of the apparent rationality exhibited by organisms in their specific habitat. Given the equivalence between selection and rationality as maximizing processes, one would indeed expect organisms to implement rational decision-makers. Yet, many violations of the clauses of rationality have been witnessed in various species such as starlings, hummingbirds, amoebas and honeybees.
View Article and Find Full Text PDFHamilton's original derivation of his rule for the spread of an altruistic gene (rb>c) assumed additivity of costs and benefits. Recently, it has been argued that an exact version of the rule holds under non-additive pay-offs, so long as the cost and benefit terms are suitably defined, as partial regression coefficients. However, critics have questioned both the biological significance and the causal meaning of the resulting rule.
View Article and Find Full Text PDFTranscranial magnetic stimulation has become an important field for both research in neuroscience and for therapy since Barker in 1985 showed that it was possible to stimulate the human motor cortex with an electromagnet. Today for instance, transcranial magnetic stimulation can be used to measure nerve conduction velocities and to create virtual lesions in the brain. The latter option creates the possibility to inactivate parts of the brain temporarily without permanent damage.
View Article and Find Full Text PDFOrganisms constitute one of the most remarkable features of our living world. However, they have not yet received any accepted characterization within the framework of the evolutionary theory. The reasons for this contrast between the saliency of organisms in the biological landscape and their theoretical status are multiple and they are analyzed in the first part of this paper.
View Article and Find Full Text PDFJ Chromatogr B Analyt Technol Biomed Life Sci
April 2002
When analyzing bio-matrix samples using capillary electrophoresis (CE) or micellar electrokinetic chromatography (MEKC), unwanted shifts in the time axis are often observed, both between samples and standards and between samples, thus hampering identification. These shifts are caused by either or both of two sample matrix-induced effects: variations in stacking conditions (effective field strength or migration length) and variations in electroosmotic flow. Based on elementary CE principles and provided that any two peaks in the pherograms can be linked, these variations can be separately accounted and quantitatively corrected for, so that perfectly overlapping pherograms of standards and samples can be obtained after normalization.
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