RESUMEN
An estimation of the measurand in dynamic metrology usually requires a deconvolution based on a dynamic calibration of the measuring system. Since deconvolution is, mathematically speaking, an ill-posed inverse problem, some kind of regularization is required to render the problem stable and obtain usable results. Many approaches to regularized deconvolution exist in the literature, but the corresponding evaluation of measurement uncertainties is, in general, an unsolved issue. In particular, the uncertainty contribution of the regularization itself is a topic of great importance, because it has a significant impact on the estimation result. Here, a versatile approach is proposed to express prior knowledge about the measurand based on a flexible, low-dimensional modeling of an upper bound on the magnitude spectrum of the measurand. This upper bound allows the derivation of an uncertainty associated with the regularization method in line with the guidelines in metrology. As a case study for the proposed method, hydrophone measurements in medical ultrasound with an acoustic working frequency of up to 7.5 MHz are considered, but the approach is applicable for all kinds of estimation methods in dynamic metrology, where regularization is required and which can be expressed as a multiplication in the frequency domain.
RESUMEN
An optical multilayer detection array for ultrasonic measurements is presented. The probe comprises a dielectric interference filter structure that is evaporated onto a glass plate. An incident acoustic pressure signal deforms the layer system, and the induced modulation of the optical reflectance is determined by a simple optical detection scheme. The principle of measurement is demonstrated by a line scan through the focus of a broadband transducer and can be applied to rapid two-dimensional characterization of ultrasonic fields. The high temporal and spatial resolution of the measurements is combined with high sensitivity and durability of the probe, and, in contrast with fiber-tip multilayer hydrophones, the multilayer detection array provides signals that are not influenced by acoustic resonances and diffraction phenomena.
RESUMEN
The total mercury (Hg) in hair and blood of 45 young healthy adult female Macaque fascicularis given 0, 50, 70, or 90 micrograms MeHg/kg body wt orally in apple juice daily revealed a close and constant ratio between blood Hg and hair. The amount of hair Hg does not increase with time (maximum period of observation 490 days) at a given dose level. Also the ratio was unchanged between background and subtoxic dose levels. Individuals at a given dose level with a higher-than-average blood level had a proportionately higher hair level. The Macaque blood/hair ratio is markedly lower than that reported for humans. Pregnancy did not have an appreciable effect on the hair mercury level. Review of the known variables in human and Macaque hair growth and structure does not provide an explanation for the difference. We suggest that an as yet unidentified biological variable(s), possibly circumfollicular blood flow, could account for the difference. This ratio difference notwithstanding, controlled studies on Macaque hair such as this add support for the validity of terminal hair as a trace metal exposure indicator.