The use of fish as test animals for the study of insecticides

This article does not have an abstract

Synthetic experiments in the benzo-pyrone series. Part VI. Action of aluminium chloride on angelicin, psoralen and related compounds

This article does not have an abstract

Reference-free removal of EEG-fMRI ballistocardiogram artifacts with harmonic regression

Combining electroencephalogram (EEG) recording and functional magnetic resonance imaging (fMRI) offers the potential for imaging brain activity with high spatial and temporal resolution. This potential remains limited by the significant ballistocardiogram (BCG) artifacts induced in the EEG by cardiac pulsation-related head movement within the magnetic field. We model the BCG artifact using a harmonic basis, pose the artifact removal problem as a local harmonic regression analysis, and develop an efficient maximum likelihood algorithm to estimate and remove BCG artifacts. Our analysis paradigm accounts for time-frequency overlap between the BCG artifacts and neurophysiologic EEG signals, and tracks the spatiotemporal variations in both the artifact and the signal. We evaluate performance on: simulated oscillatory and evoked responses constructed with realistic artifacts; actual anesthesia-induced oscillatory recordings; and actual visual evoked potential recordings. In each case, the local harmonic regression analysis effectively removes the BCG artifacts, and recovers the neurophysiologic EEG signals. We further show that our algorithm outperforms commonly used reference-based and component analysis techniques, particularly in low SNR conditions, the presence of significant time-frequency overlap between the artifact and the signal, and/or large spatiotemporal variations in the BCG. Because our algorithm does not require reference signals and has low computational complexity, it offers a practical tool for removing BCG artifacts from EEG data recorded in combination with fMRI.National Institutes of Health (U.S.) (Award DP1-OD003646)National Institutes of Health (U.S.) (Award TR01-GM104948)National Institutes of Health (U.S.) (Grant R44NS071988)National Institute of Neurological Diseases and Stroke (U.S.) (Grant Grant R44NS071988

Sub-Diffusive Scattering Parameter Maps Recovered Using Wide-Field High-Frequency Structured Light Imaging

This study investigates the hypothesis that structured light reflectance imaging with high spatial frequency patterns (fx) can be used to quantitatively map the anisotropic scattering phase function distribution (P(θs)) in turbid media. Monte Carlo simulations were used in part to establish a semi-empirical model of demodulated reflectance (Rd) in terms of dimensionless scattering (μ′sf−1x) and γ, a metric of the first two moments of the P(θs) distribution. Experiments completed in tissue-simulating phantoms showed that simultaneous analysis of Rd spectra sampled at multiple fx in the frequency range [0.05-0.5] mm−1 allowed accurate estimation of both μ′s(λ) in the relevant tissue range [0.4-1.8] mm−1, and γ(λ) in the range [1.4-1.75]. Pilot measurements of a healthy volunteer exhibited γ-based contrast between scar tissue and surrounding normal skin, which was not as apparent in wide field diffuse imaging. These results represent the first wide-field maps to quantify sub-diffuse scattering parameters, which are sensitive to sub-microscopic tissue structures and composition, and therefore, offer potential for fast diagnostic imaging of ultrastructure on a size scale that is relevant to surgical applications

Structured Light Scatteroscopy

A new imaging approach, structured light scatteroscopy (SLS), is demonstrated, which offers rapid wide-field imaging of microscopic morphological variations in bulk tissue surfaces. Elastic scattering of light offers exquisite sensitivity to ultrastructural changes at multiple size scales ranging from nanometers to millimeters, but in bulk tissues the confounding effects of molecular absorption and strong multiple scattering of light often lead to a dramatic reduction in scatter contrast and specificity. It is demonstrated that the SLS using structured high spatial frequency illumination and detection to probe the tissue achieves direct, absorption-independent, high-resolution maps of the scattering response. The scattering response is observed to be dependent on both the wavelength and spatial frequency of choice, indicating a potential for multiscale probing of ultrastructural changes in superficial tissue layers. This methodology can be easily applied in most wide-field imaging systems