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K P Zimmermann

Publications and source records attributed to K P Zimmermann.

4 recordsLinked to original sources
PubMed1996

"Slinky" coils for neuromagnetic stimulation.

Future advances in neuromagnetic stimulation depend significantly on the design of coils with improved focality. Although in the absence of internal current sources, no true focusing of magnetically induced currents is possible, improvements in the focality of current concentrations passing through an area of biologic tissue are achievable through variations of the shape, orientation and size of neuromagnetic stimulating coils. The "butterfly" and the "4-leaf" coils are two examples of planar designs which achieve improved focality through centralization of the maximum coil current and peripheral distribution of the return currents. We introduce the "slinky" coil design as a 3-dimensional generalization of the principle of peripheral distribution of return currents and demonstrate its advantages over planar designs.

Electric Stimulation↗
PubMed1995

Post-stroke autonomic nervous system function: palmar sympathetic skin responses thirty or more days after cerebrovascular accident.

We studied sympathetic nervous system (SNS) function after cerebrovascular accident (CVA) by measuring hypothenar sympathetic skin responses (SSR) to normal or hemiplegic arm electrical stimulation. We anticipated SNS function after CVA to be asymmetric and selected null hypotheses of bilaterally symmetric SSR latencies and amplitudes irrespective of side of stimulation and/or recording. Thirteen patients between ages 44 and 77 years (median 59) were tested between 1 and 72 months (median 15) after CVA. Hypothenar recording and dorsal reference surface electrodes were used. Amplifier bandwidth was set from 0.5 to 100 Hz. Gain was adjusted to allow adequate recognition of the waveforms. Sweep speed was set to 500ms/div. Stimulus width was set to 0.2 ms and intensity was increased stepwise from 10mA initially until optimum responses were obtained. Nonparametric statistics were used to analyze the data. SSRs were present in all patients on both the normal and the hemiplegic sides irrespective of the side of stimulation. Median SSR latency recorded homolaterally to the stimulus site was found to be 80ms shorter than median SSR latency recorded heterolaterally. Median SSR latency in left hemiplegics was found to be 16% longer than in right hemiplegics. Otherwise, neither side of hemiplegia, side of stimulation, side of recording nor any paired combination thereof were found to be significant. Our finding of bilaterally obtainable SSRs after CVA diverges from that of Uncini and colleagues but presumably only reflects the difference in poststroke chronology between the respective samples.

Adult↗
PubMed1983

Ultrasound velocity in fixed human liver: empirical anova and regression modelling on histologically assessed abnormalities.

Anova and "dummy variables" least squares regression methods are used to investigate the dependence of ultrasound propagation velocity on the presence or absence of fat and on the rank ordered level of cirrhosis in fixed human liver. Cirrhosis is found to affect velocity in a nonlinear fashion, while fat depresses the velocities toward lower values. Quantifications of these effects and statistical analyses of their magnitudes are presented. The results represent a contribution toward the empirical understanding of the effects of tissue abnormalities on the velocity of ultrasound propagation in fixed human tissues.

Analysis of Variance↗