PubMed · 11601401
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V E Kokhan, O Iu Gorbachev, N V Tret'iakov, F N Stupin. 2001. [The spine functional capability].. https://pubmed.ncbi.nlm.nih.gov/11601401/
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Our aim is to describe a method for detecting small deformations from a three-dimensional (3D) shape of large lateral dimensions. For this purpose the measurement method is based on the simultaneous utilization of several 3D optical systems and the phase-shifting technique. In this way, the following problems appear: optical distortion due to the large field observed, nonlinear phase-to-height conversion, conversion of image coordinates into object coordinates for each 3D optical system, and coordinate unification of all optical systems. The resolution is 50 microm with a field of view of 320 mm x 150 mm. We used this system to study the 3D human foot arch deformation under low loads in vivo. First results indicate the hysteresis behavior of the human foot under a low load (50 to 450 N).
We discuss the statistical mechanical properties of a single polymer chain that forms cross links among its monomers. Models of this type have served as prototypes in theories of RNA and protein folding. The chain is allowed to form pseudoknots and its monomers can each participate in multiple cross links. We demonstrate that the conformational free energy of such a chain can be estimated by using an algorithm that scales as a power of the number of cross links N(N1-N3, depending on the problem). Straightforward exact evaluation of the chain partition function via multidimensional integration scales exponentially with N and often is computationally prohibitive. Our approach can also be used to compute the "entropic force" generated by a cross-linked chain when it is stretched at its ends. Such forces can be directly measured by atomic force microscopy or by laser optical trap experiments performed on single RNA, DNA, and protein molecules.
Rotating cylindrical filtration displays significantly reduced plugging of filter pores and build-up of a cake layer, but the number and range of parameters that can be adjusted complicates the design of these devices. Twelve individual parameters were investigated experimentally by measuring the build-up of particles on the rotating cylindrical filter after a fixed time of operation. The build-up of particles on the filter depends on the rotational speed, the radial filtrate flow, the particle size and the gap width. Other parameters, such as suspension concentration and total flow rate are less important. Of the four mechanisms present in rotating filters to reduce pore plugging and cake build-up, axial shear, rotational shear, centrifugal sedimentation and vortical motion, the evidence suggests rotational shear is the dominant mechanism, although the other mechanisms still play minor roles. The ratio of the shear force acting parallel to the filter surface on a particle to the Stokes drag acting normal to the filter surface on the particle due to the difference between particle motion and filtrate flow can be used as a non-dimensional parameter that predicts the degree of particle build-up on the filter surface for a wide variety of filtration conditions.