Absorption spectra ( ∼ 600 to 1064 nm) of six tissues in three healthy volunteers were measured by combining dual-slope continuous-wave broadband spectroscopy with self-calibrated frequency-domain measurements of scattering at two wavelengths (690 and 830 nm). The spectral fit with a linear combination of oxy- and deoxyhemoglobin, water, and lipids extinction spectra is improved by a wavelength-independent absorption background. The need to introduce this background is assigned to the inhomogeneous distribution of absorbers in tissue. By using a two-layer model, the relationship between recovered concentrations and their two-layer values was investigated, and the implications for non-invasive tissue spectroscopy are discussed.

We present a calibration-free instrument to measure absolute broadband absorption spectra of biological tissue. Initial measurements in skeletal muscle show that the fit to the data improves by introducing a spectrally flat absorption background.

The following is a foundationalist exercise based upon a single observation or postulate distinguishing one's knowledge of information versus one's knowledge of one's former unknowing of that information. This postulate is titled the "principle of implicit ignorance." Utilizing this postulate, several theorems are constructed including the equivalence to Hume's thesis regarding the absence of knowledge of a necessary connection. The postulate is then negated, demonstrating equivalence to Kant's thesis regarding the presence of synthetic a priori statements. The final result is a single general epistemic postulate that brokers between the two respective positions. Because both systems are the result of this general principle, rejecting the results of one system necessarily forces one into the contrary position.

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The following is a foundationalist exercise based upon a single observation or postulate distinguishing one’s knowledge of information versus one’s knowledge of one’s former unknowing of that information. This postulate is titled the “principle of implicit ignorance.” Utilizing this postulate, several theorems are constructed including the equivalence to Hume’s thesis regarding the absence of knowledge of a necessary connection. The postulate is then negated, demonstrating equivalence to Kant’s thesis regarding the presence of synthetic a priori statements. The final result is a single general epistemic postulate that brokers between the two respective positions. Because both systems are the result of this general principle, rejecting the results of one system necessarily forces one into the contrary position.