Why We Sleep?

Fatigue after major joint arthroplasty: Relationship to preoperative fatigue and postoperative emotional state

In earlier chapters we saw how Greek thinkers, from Thales to Plato, developed an elaborate picture of the universe we live in. Though of great historic interest, their physical theories have been superseded by the progress of science, and can no longer offer us enlightenment about the world. The same is true of Aristotle’s world-picture; but in addition to physical speculation, Aristotle offered, to a much greater extent than any of his predecessors, a philosophical examination of underlying concepts that are basic to physical explanation of many different kinds. His philosophy of physics, unlike his physical system itself, contains much that remains of abiding interest.

Temperature effect on apple biospeckle activity evaluated with different indices

Explaining human movements and actions: Children's understanding of the limits of psychological explanation

Biological processes, from morphogenesis to tumor invasion, spontaneously generate shear stresses inside living tissue. The mechanisms that govern the transmission of mechanical forces in epithelia and the collective response of the tissue to bulk shear deformations remain, however, poorly understood. Using a minimal cell-based computational model, we investigate the constitutive relation of confluent tissues under simple shear deformation. We show that an initially undeformed fluidlike tissue acquires finite rigidity above a critical applied strain. This is akin to the shear-driven rigidity observed in other soft matter systems. Interestingly, shear-driven rigidity can be understood by a critical scaling analysis in the vicinity of the second order critical point that governs the liquid-solid transition of the undeformed system. We further show that a solidlike tissue responds linearly only to small strains and but then switches to a nonlinear response at larger stains, with substantial stiffening. Finally, we propose a mean-field formulation for cells under shear that offers a simple physical explanation of shear-driven rigidity and nonlinear response in a tissue.

The sensitive detection and quantitative measurement of biological nanoparticles such as viruses or exosomes is of growing importance in biology and medicine since these structures are implicated in many biological processes and diseases. Interferometric reflectance imaging is a label-free optical biosensing method which can directly detect individual biological nanoparticles when they are immobilized onto a protein microarray. Previous efforts to infer bio-nanoparticle size and shape have relied on empirical calibration using a 'ruler' of particle samples of known size, which was inconsistent and qualitative. Here, we present a mechanistic physical explanation and experimental approach by which interferometric reflectance imaging may be used to not only detect but also quantitatively measure bio-nanoparticle size and shape. We introduce a comprehensive optical model that can quantitatively simulate the scattering of arbitrarily-shaped nanoparticles such as rod-shaped or filamentous virions. Finally, we optimize the optical design for the detection and quantitative measurement of small and low-index bio-nanoparticles immersed in water.

Charge transfer in convective thunderclouds induced by molecular interface crossing and free energy reduction

The application of the principles of biological information processing to real technical tasks has not been attempted very often except in a few cases of without promising any generality. However, the results of psychological and neurological research on the human brain are not only interesting from the point of view of providing physical explanations to mental effects, but also from a cybernetical viewpoint of providing design principles for man-made systems.