Novel Design of a Model Reference Adaptive Controller for Soft Tissue Operations

Model Reference Adaptive Controllers (MRAC) have dual functionality: besides guaranteeing precise trajectory track- ing of the controlled system, they have to provide an “external control loop” with the illusion that it controls a physical system of prescribed dynamic properties, i.e., the “reference system”. The MRACs are designed traditionally by Lyapunov’s 2 nd method that is mathematically complicated, requiring strong skills from the designer. Adaptive controllers alternatively designed by the use of Robust Fixed Point Transformations (RFPT) operate according to Banach’s Fixed Point Theorem , and are normally simple iterative constructions that also have a standard variant for MRAC design. This controller assumes a single actuator that is driven adaptively. Master–Slave Systems form a distinct class of practical applications, in which two arms—the master and the slave—operate simultaneously. The movement of the master must be tracked precisely by the slave in spite of the quite different forces exerted by them. In the present paper, a soft tissue-cutting operation by a master–slave structure is simulated. The master arm has a simple torque–reference friction model, and is driven by the surgeon. The obtained master arm trajectory has to be precisely tracked by the electric DC motor driven slave system, which is in dynamic interaction with the actual tissue under operation. It is shown via simulations that the RFPT-based design can efficiently solve such tasks without considerable mathematical complexity

Quantitative Estimation of the Ratio of GABA-Immunoreactive Cells in Neocortical Grafts

Somatosensory anlage from 17-18 day old rat embryos were transplanted in place of the removed barrel cortex in adult rats. Six to eight months after transplantation, the grafts were either completely separated by glial scar or partly separated and partly confluent with the host neocortex. Each was studied histologically and immunostained for GABA. It was found that in partly confluent grafts the neuronal density was similar or even higher than in the host cortex, while the cell number in the separate grafts was much lower than in the nearby host cortex. The number of GABA-positive cells, however, was in all grafts significantly lower (2.9% on average) than in the normal cortex (11.8% on average).The decline in GABA-stained nerve cells was highest in separated grafts, but was somewhat less marked in transplants partly confluent with the host tissue. The possible role of partial or total deafferentation as well as the relative vulnerability of the transplanted tissue by temporary hypoxia and other metabolic disturbances are discussed as the probable factors in selective decline of GABA-ergic cells in the transplanted somatosensory cortex

Age-Related Loss of GABA-Positive and GABA-Negative Neurons in Neocortical Transplants

The numerical density of GABA immunopositive and GABA immunonegative neurons was quantitatively determined in 0, 12, 30 and 90 day-old neocortical transplants, derived from E17 rat embryos and transplanted into adult hosts. It was found that the original, very high neuronal density in the fetal transplant declined steadily after transplantation to the somatosensory cortex of adult rat. The decline in numerical density of GABA-positive neurons, however, was disproportionately larger than that of GABA-negative nerve cells: At 90 days the proportion of GABA-positive cells was 2.3% (in contrast to the 11.8% in the adult host cortex). The density of GABA-negative neurons, on the other hand, remained slightly higher than comparable values in the control cortex. The decline in density Of GABA-positive neurons was continuous until the 90th post-transplantation day, while final, close to normal density values of GABA-negative nerve cells were already reached in 30 day-old grafts, with no significant change afterwards

Compilation of isomeric ratios of light particle induced nuclear reactions

Experimental isomeric ratios of light (A$\le$4) particle-induced nuclear reactions were compiled for the product nuclides having metastable states with half-lives longer than 0.1 sec. The experimental isomeric ratio data were taken from the EXFOR library and reviewed. When an experiment reports isomer production cross sections instead of isomeric ratios, the cross sections taken from the EXFOR library were converted to the isomeric ratios by us. During compilation, questionable data (e.g.,preliminary data compiled in EXFOR in parallel with their final data, sum of isomer production cross sections larger than the total production cross sections) were excluded. As an application of the new compilation, goodness-of-fit was studied for the isomeric ratios predicted by the reaction model code TALYS-1.96

Determining matrix elements and resonance widths from finite volume: the dangerous mu-terms

The standard numerical approach to determining matrix elements of local operators and width of resonances uses the finite volume dependence of energy levels and matrix elements. Finite size corrections that decay exponentially in the volume are usually neglected or taken into account using perturbation expansion in effective field theory. Using two-dimensional sine-Gordon field theory as "toy model" it is shown that some exponential finite size effects could be much larger than previously thought, potentially spoiling the determination of matrix elements in frameworks such as lattice QCD. The particular class of finite size corrections considered here are mu-terms arising from bound state poles in the scattering amplitudes. In sine-Gordon model, these can be explicitly evaluated and shown to explain the observed discrepancies to high precision. It is argued that the effects observed are not special to the two-dimensional setting, but rather depend on general field theoretic features that are common with models relevant for particle physics. It is important to understand these finite size corrections as they present a potentially dangerous source of systematic errors for the determination of matrix elements and resonance widths.Comment: 26 pages, 13 eps figures, LaTeX2e fil