Role of patient education level in predicting macrosomia among women with gestational diabetes mellitus.

OBJECTIVE: To evaluate the role of education level in predicting the risk of macrosomia among women with gestational diabetes mellitus. STUDY DESIGN: Women with gestational diabetes, who were referred to the California Diabetes and Pregnancy Sweet Success Program between June 2001 and December 2002, were included in the study. Multiple logistic regression was used estimate the risk of macrosomia, defined as a birth weight >4000 g. RESULTS: Compared to college-educated women, high school- and middle school-educated women were 21% (relative risk (RR), 1.21; 95% confidence intervals (CI), 1.01-1.44) and 35% (RR, 1.35; 95% CI, 1.09-1.70) more likely to deliver a macrosomic infant, respectively. CONCLUSION: Gestational diabetics with a lower level of educational attainment appear to have an increased risk of macrosomia. Future studies are necessary to determine whether this finding reflects a variation in adherence to recommended treatments by education/literacy level, or if it is a surrogate marker for intrinsic, biological differences or differences in lifestyle.

Instrument to measure the bidirectional reflectance distribution function of surfaces.

A new instrument to measure the in situ bidirectional reflectance distribution function (BRDF) of surfaces is described. This instrument measures the BRDF for eight illumination angles from 0 to 65 deg, three colors (475, 570, and 658 nm), and at over 100 selected viewing angles. The viewing zenith angles range from 5 to 65 deg, and the azimuth angles, relative to the illumination direction, range from 0 to ?180 deg. Many tests of the system have been run and show that for flat surfaces the BRDF of a sample surface can be measured with a precision of 1-5% and an accuracy of 10% of the measured reflectance. The BRDF for a dry and wet sand sample is presented as a demonstration of the instrument.

Raman scattering by pure water and seawater.

Measurements of the magnitude and spectral distribution of the Raman-scattering coefficients of pure water (b(rw)) and seawater (b(rs)) are presented. Two independent measurements of the spectral distribution of the Raman-scattering coefficient of pure water were made for incident wavelengths ranging from 250 to 500 nm. These measurements revealed a strong dependence of b(rw) on wavelength that could be represented by a (lambda')(-5.3+/-0.3) relationship, where lambda' is the incident wavelength, or a lambda(-4.6+/-0.3) relationship, where lambda is the Raman-scattered wavelength, when normalized to units of photons. The corresponding relationships for normalization to energy are (lambda')(-5.5+/-0.4) and lambda(-4.8+/-0.3), respectively. These relationships are found to be consistent with resonance Raman theory for an absorption wavelength of 130 nm. The absolute value of b(rw) for the 3400-cm(-1) line was found to be (2.7 +/- 0.2) x 10(-4) m(-1) for an incident wavelength of 488 nm, which is consistent with a number of earlier reports. The difference between the magnitudes of the Raman-scattering coefficients for pure water and seawater was statistically insignificant.

Polarized radiance distribution measurements of skylight. I. System description and characterization.

A new system to measure the natural skylight polarized radiance distribution has been developed. The system is based on a fish-eye lens, CCD camera system, and filter changer. With this system sequences of images can be combined to determine the linear polarization components of the incident light field. Calibration steps to determine the system 's polarization characteristics are described. Comparisons of the radiance measurements of this system and a simple pointing radiometer were made in the field and agreed within 10 % for measurements at 560 and 670 nm and 25 % at 860 nm. Polarization tests were done in the laboratory. The accuracy of the intensity measurements is estimated to be 10 %, while the accuracy of measurements of elements of the Mueller matrix are estimated to be 2 %.

Measurement of the point-spread function in a layered system.

A laboratory facility to measure the point-spread function (PSF) of water with the addition of scattering layers is described. The PSF was measuredby using an approximately Lambertian source and a camera that viewed this source but focused at infinity. Measurements for various optical path lengths with the scattering layer in three separate regions, i.e., near the source, near the camera, and an intermediate case, were performed. The PSF was found to depend strongly on the location of the scattering layer. For the same optical path length, the most diffuse PSF was found for the case of a scattering layer near the camera.

In situ measurements of Raman scattering in clear ocean water.

We have further developed and improved the prototype oceanic Fraunhofer line discriminator by using a well-protected fiber-optic-wire cable and in-water electronic housing. We conducted a series of in situ measurements in clear ocean water in the Florida Straits. By comparing the reduced data with the Monte Carlo simulation results, we verify the Raman scattering coefficient B(r) with an excitation wavelength at 488 nm to be 2.6 x 10(-4) m(-1) [Appl. Opt. 29, 71-84 (1990)], as opposed to 14.4 x 10(-4) m(-1) [Appl. Opt.14, 2116-2120 (1975)]. The wavelength dependence of the Raman scattering coefficient is found to have an insignificant effect on the in-water light field. We also discuss factors that lead to errors. This study can be used as a basis for inelastic light scattering in the radiative transfer theory and will allow other inelastic light, e.g., fluorescence, to be detected with in situ measurements.

Measurement of the spectral absorption coefficient in the ocean with an isotropic source.

Closed-form equations that describe the vector irradiance from an isotropic source embedded in the oceanare rigorously derived from the steady-state radiative transfer equation. The equations are exact for a homogeneous medium and are believed to be an excellent approximation along the vertical axis for a plane-parallel ocean. The equations are solved for the absorption coefficient as a function of distance from the source. For clear ocean water, it is shown that vector irradiance measurements alone provide sufficient information for an accurate calculation of the absorption coefficient. Measurements in Pacificwater of the vector irradiance from an isotropic source are presented, and the absorption coefficient is computed. The estimated value of the absorption coefficient from a linear least-squares fit to the data has a standard error of ~ 1%.

Simulation of inelastic-scattering contributions to the irradiance field in the ocean: variation in Fraunhofer line depths.

Raman scattering and fluorescence are important processes in oceanic optics because of their influence on the natural light field in the water. Monte Carlo simulations are described that verify that measurements of the Fraunhofer line depth in the in-water irradiance can be used to separate the irradiance into elastic and inelastic components, i.e., components that are generated by elastic- and inelastic-scattering processes, respectively. Specifically, the upwelling and downwelling irradiances, including Raman scattering, are simulated for a variety of model oceans. The inherent optical properties of the ocean are derived from a bio-optical model in which the elastic-scattering and the absorption coefficients of the biological material depend only on the phytoplankton pigment concentration, C. The Fraunhofer line at 656 nm is found to fill in, i.e., disappear into, the background continuum rapidly with increasing depth. This indicates a rapid transition from a near-surface light field dominated by elastic s cattering to one composed of irradiance derived entirely from Raman scattering. Conversely the depth of the Fraunhofer line at 486 mm is nearly independent of depth in the water, indicating that Raman scattering never makes a significant contribution to the irradiance there. Between these two extremes, the lines at 518 and 589 nm show variations in line depths that depend significantly on C, e.g., at 518 nm the line fills in with increasing depth at low-C values but not at high-C values.

Temperature dependence of beam scattering in young sea ice.

Laboratory measurements of the upward intensity distribution in young thin sea ice illustrate the variation of this distribution and peak intensity with growth temperature and ice thickness.

Point spread function in ocean water: comparison between theory and experiment.

A new instrument to measure the point spread function (PSF) in the ocean has provided the opportunity for direct comparison between theoretical predictions and experimental measurement. Theoretical predictions are derived from small angle scattering theory using a simple algebraic fit to the single scattering phase function. The resulting predictions for the PSF are found to match the experimental measurements over a wide range of angles and optical depths.

Simple empirical model of the oceanic point spread function.

The point spread function (PSF) is an important property for predicting beam propagation and imaging system performance. Measurements of the PSF in three different locations (Pacific Ocean, Tongue of the Ocean, and Sargasso Sea) are presented. These measurements are used to validate extensive laboratory measurements [S. Q. Duntley, "Underwater Lighting by Submerged Lasers and Incandescent Sources," SIO Ref. 71-1, Scripps Institution of Oceanography, U. California, San Diego (1971)]. In all three locations a simple exponential expression describes the angular variation of the PSF in the 4-100-mrad range. The exponent in this relationship has a simple location specific dependence on attenuation length and the ratio of the absorption to beam attenuation coefficient. These relationships can be used to predict the PSF for an arbitrary path length.

Measurement of the point spread function in the ocean.

A new instrument to measure the point spread function (PSF) in the ocean is described. This instrument uses a CCD solid state camera to measure the angular radiance field due to a pulsed Lambertian source. In this way the PSF can be measured easily at sea, when precise alignments over ranges >10 m cannot be maintained. With the large dynamic range of the camera system, the PSF can be measured over short ranges (10 m), and the variation of the PSF with depth, or range, can be investigated.

Measurement of the Mueller matrix for ocean water.

The normalized light scattering polarization matrix has been measured for ocean water using an electrooptic light scattering polarimeter. Measurements were done on samples from the Atlantic and Pacific Oceans and the Gulf of Mexico. The polarization effects in the matrices were found to have, in general, a form which is similar to polarization effects in the Rayleigh scattering approximation; for example, all off-diagonal matrix elements except S12 and S21 were zero. Mueller matrix elements were calculated using a Mie computer code and compared to the measured matrices for ocean water. A simple one-component distribution was found to produce a reasonably good fit.