The ballistocardiogram (BCG) measures the reaction of the body to cardiac ejection forces, and is an effective, non-invasive means of evaluating cardiovascular function. A simple, robust method is presented for acquiring high-quality, repeatable BCG signals from a modified, commercially available scale. The measured BCG waveforms for all subjects qualitatively matched values in the existing literature and physiologic expectations in terms of timing and IJ amplitude. Additionally, the BCG IJ amplitude was shown to be correlated with diastolic filling time for a subject with premature atrial contractions, demonstrating the sensitivity of the apparatus to beat-by-beat hemodynamic changes. The signal-to-noise ratio (SNR) of the BCG was estimated using two methods, and the average SNR over all subjects was greater than 12 for both estimates. The BCG measurement was shown to be repeatable over 50 recordings taken from the same subject over a three week period. This approach could allow patients at home to monitor trends in cardiovascular health.

https://iopscience.iop.org/article/10.1088/0967-3334/30/2/005/pdf

Robust ballistocardiogram acquisition for home monitoring.

The effects of two kinds of experimental manipulation of semantic meaning were studied in Evoked Potentials (EPs), brain responses recorded from scalp monitors. Both kinds of semantic manipulation were based on Osgood's rating analyses which described three primary dimensions of connotative meaning: Evaluation, Potency, and Activity (E, P, and A). One kind of experimental variable was the semantic class of the stimulus word (E+, E-, P+, P-, A+, A-). The other kind of experimental variable was the semantic dimension of the rating scale (E, P, A) which the subject used to make semantic judgments ab out the stimulus words. These variables were experimentally combined in that for each trial the subject used adesignated semantic scale to judge a specified stimulus word while brain activity was recorded. Using multivariate procedures, both stimulus word class and scale dimension effects on the EPs were found. Individual subject analyses demonstrated the generality of the results by showing successful discrimination of word classes and scale dimensions for each of the ten subjects analyzed separately. Supported in part by NIH Research Grant 5 R01 EY01593 and the Advanced Research Projects Agency (Contract N00014-77-C-0037). The author thanks John W. McCrary and John A. Chapman for their collaboration in this research and Janice K. Martin for her assistance.

Evoked Brain Potentials and Behavior

Resolution measures in molecular electron microscopy provide means to evaluate quality of macromolecular structures computed from sets of their two-dimensional (2D) line projections. When the amount of detail in the computed density map is low there are no external standards by which the resolution of the result can be judged. Instead, resolution measures in molecular electron microscopy evaluate consistency of the results in reciprocal space and present it as a one-dimensional (1D) function of the modulus of spatial frequency. Here we provide description of standard resolution measures commonly used in electron microscopy. We point out that the organizing principle is the relationship between these measures and the spectral signal-to-noise ratio (SSNR) of the computed density map. Within this framework it becomes straightforward to describe the connection between the outcome of resolution evaluations and the quality of electron microscopy maps, in particular, the optimum filtration, in the Wiener sense, of the computed map. We also provide a discussion of practical difficulties of evaluation of resolution in electron microscopy, particularly in terms of its sensitivity to data processing operations used during structure determination process in single particle analysis and in electron tomography (ET).

/pdf/resolution-measures-in-molecular-electron-microscopy-54310xrlf6.pdf

Resolution measures in molecular electron microscopy

http://www.wriggers.biomachina.org/courses/structures/download/penczek_ssnr_02.pdf

Three-dimensional spectral signal-to-noise ratio for a class of reconstruction algorithms

Argon laser induced event related responses to pricking pain (first pain) were recorded. The different recording parameters (recording site, filter setting, averaging technique), quantification parameters (amplitude, power) and variability between successive recordings were studied. The single responses were large, and averaging of 16-32 single trials was sufficient to obtain reliable averaged responses. The power (0.5-7.5Hz) of the averaged vertex recorded response was, for the range of intensities considered, the most sensitive parameter to quantify the stimulus and hence the intensity of pain perceived.

https://jnnp.bmj.com/content/jnnp/53/5/398.full.pdf

First pain event related potentials to argon laser stimuli: recording and quantification.

Two versions of a Gaussian signal, corrupted by independent Gaussian noises, are available for estimating the signal-to-noise power ratio. This correspondence demonstrates that the sample correlation coefficient can be used to construct an unbiased estimator that is asymptotically efficient.

N. Bershad

Papers

On estimating signal-to-noise ratio using the sample correlation coefficient (Corresp.)