Mapping tropospheric ozone profiles from an airborne ultraviolet-visible spectrometer

We present a novel technique for retrieving ozone (O3) profiles and especially tropospheric O3 from airborne UV/visible spectrometer measurements. This technique utilizes radiance spectra from one down-looking and two up-looking (85 degrees and 75 degrees) directions, taking advantage of the O3 absorption structure in the Huggins (300-340-nm) and Chappuis (530-650-nm) bands. This technique is especially sensitive to tropospheric O3 below and < or =8 km above the aircraft with a vertical resolution of 2-6 km and is sensitive to lower and middle stratospheric O3 with a vertical resolution of 8-15 km. It can measure tropospheric O3 at spatial resolutions of 2 km x 2 km or higher and is therefore well suited for regional air-quality studies and validation of satellite measurements.     

Occurrence of human pancreatic polypeptide in pancreatic endocrine tumors. Possible implication in the watery diarrhea syndrome

Eighteen endocrine pancreatic tumors were examined for the occurrence of cells producing insulin, glucagon, gastrin, human pancreatic polypeptide (HPP), and vasoactive intestinal polypeptide (VIP) and for A1 cells. More than half of the tumors were mixed, i.e., they contained more than one type of hormone-producing cell. The clinical symptoms were attributable only to one of the hormones produced by the mixed tumors. Three of four tumors causing the watery diarrhea syndrome contained both VIP and HPP cells. In one such tumor there was a strong predominance of HPP cells; the serum HPP levels of this patient were a thousandfold elevated, whereas her VIP levels were within the normal range. Several lines of evidence point to HPP as a possible agent causing the watery diarrhea syndrome. In many of our patients, HPP cells hyperplasia was present in the extratumoral pancreas. Such hyperplasia may give rise to the raised serum HPP levels seen in many patients having endocrine pancreatic tumors.     

Photon migration in the presence of a single defect: a perturbation analysis

We present an analytical perturbation analysis for studying the sensitivity of diffusive photon flux to the addition of a small spherical defect object in multiple-scattering media such as human tissues. As a first simple application of our perturbation method, we derive analytically the photon migration path distributions and the shapes of the so-called banana regions in which the photon migration paths are concentrated. We then derive analytically the sensitivity of detected photon flux densities to the inclusion of small spherical defects in the multiple-scattering medium for both single-source and two-source configurations, at both steady-state (dc) and frequency-modulation conditions, and compare the results with Monte Carlo simulations.     

Combined ultrasound and near infrared diffused light imaging in a test object

We have investigated the use of combining near infrared (NIR) diffuse light and ultrasound imaging methods to increase the detection sensitivity and to reduce the false alarm rate in small target detection. A line-of-sight optical projection through a test object is identified from an amplitude null and a sharp phase transition produced by diffusive waves originating from two in-phase (initial phase 0 degrees ) and out-of-phase (initial phase 180 degrees ) light emitting diode sources. This line-of-sight is scanned across a scattering phantom. A complete ultrasound B-scan image is recorded at each projected line in the optical scan. Each acoustic image plane is bisected by the optical beam path and lies in the optical scan plane. The scattering phantom simulates acoustic and optical properties of homogeneous tissue. A single small cylinder-like object simulating some acoustic and optical breast tumor properties is inserted at various places in the scattering phantom. With this single object, the optical scanning identifies the line-of-sight passing through the simulated tumor quite well. Most of these simulated tumors were at or below the threshold for acoustic detection and were not seen consistently with unguided ultrasound. For tests in which a target was apparently detected optically, the selected line-of-sight was indicated in each of three adjacent ultrasound images. Two radiologist observers were statistically more accurate (83%) in identifying the target location on the optically-selected ultrasound images than in the unmarked images (52%). That is, in these single-targets of homogeneous scattering background, the optical technique usually provided the correct line-of-sight, and ultrasound generally showed the location along that line.     

Interpreting satellite column observations of formaldehyde over tropical South America

Space-borne column measurements of formaldehyde (HCHO), a high-yield oxidation product of volatile organic compounds (VOCs), represent important constraints for quantifying net regional fluxes of VOCs. Here, we interpret observed distributions of HCHO columns from the Global Ozone Monitoring Experiment (GOME) over tropical South America during 1997-2001. We present the first comparison of year-long in situ isoprene concentrations and fire-free GOME HCHO columns over a tropical ecosystem. GOME HCHO columns and in situ isoprene concentrations are elevated in the wet and dry seasons, with the highest values in the dry season. Previous analysis of the in situ data highlighted the possible role of drought in determining the elevated concentrations during the dry season, inferring the potential of HCHO columns to provide regional-scale constraints for estimating the role of drought on isoprene emissions. The agreement between the observed annual cycles of GOME HCHO columns and Along-Track Scanning Radiometer firecount data over the Amazon basin (correlations typically greater than 0.75 for a particular year) illustrates the potential of HCHO column to provide quantitative information about biomass burning emissions.     

Diffuse optical tomography of highly heterogeneous media

We investigate the performance of diffuse optical tomography to image highly heterogeneous media, such as breast tissue, as a function of background heterogeneity. To model the background heterogeneity, we have employed the functional information derived from Gadolinium-enhanced magnetic resonance images of the breast. We demonstrate that overall image quality and quantification accuracy worsens as the background heterogeneity increases. Furthermore we confirm the appearance of characteristic artifacts at the boundaries that scale with background heterogeneity. These artifacts are very similar to the ones seen in clinical examinations and can be misinterpreted as actual objects if not accounted for. To eliminate the artifacts and improve the overall image reconstruction, we apply a data-correction algorithm that yields superior reconstruction results and is virtually independent of the degree of the background heterogeneity.     

A comparison of functional and structural consequences of the tyrosine B10 and glutamine E7 motifs in two invertebrate hemoglobins (Ascaris suum and Lucina pectinata)

The architecture of the distal heme pocket in hemoglobins and myoglobins can play an important role in controlling ligand binding dynamics. The size and polarity of the residues occupying the distal pocket may contribute steric and dielectric effects. In vertebrate systems, the distal pocket typically contains a "distal" histidine at position E7 and a leucine at position B10. There are several invertebrate organisms that have hemoglobins or myoglobins that display a pattern in which residues E7 and B10 are a glutamine and tyrosine, respectively. These proteins often have very high oxygen affinities stemming from very slow ligand off rates. In this study, two such hemoglobins, one from the nematode Ascaris suum and the other from the sulfide-fixing clam Lucina pectinata, are compared with respect to conformational and functional properties. Ultraviolet resonance Raman spectroscopy and visible resonance Raman spectroscopy are used to probe, respectively, the ligand-dependent hydrogen bonding pattern of the tyrosine residues and the proximal heme pocket interactions. Fourier transform infrared absorption spectroscopy is used to probe the dielectric properties of the distal heme pocket through the stretching frequency of carbon monoxide bound to the heme. Functionality is probed through the geminate rebinding of both CO and O2. The findings reveal two very different patterns indicative of two different mechanisms for achieving low oxygen off rates. In Hb Ascaris, a hydrogen bonding network that includes the E7 Gln, B10 Tyr, and oxygen bound to the heme results in a tight cage for the oxygen. Dissociation of the O2 requires a large amplitude conformational fluctuation that results both in a spontaneous dissociation of the oxygen through the loss of hydrogen bond stabilization and in an enhanced probability for ligand escape though the transient disruption and opening of the tight distal cage. In the case of the Hb from Lucina, there is no evidence for a tight cage. Instead the data support a model in which the hydrogen bonding network is far more tenuous and the equilibrium state of distal pocket is far more open and accessible than is the case in Ascaris. The results explain why Hb Ascaris has one of the highest oxygen affinities known (P50 approximately 10(-)3 Torr) while Hb Lucina II has an oxygen affinity comparable to that of Mb (P50 = 0.13 Torr) even though both of these Hbs contain the B10 Tyr and E7 Gln motif and display very low oxygen off rates. The roles of water and proximal strain are discussed.     

Microstructured Photopolymerization of Liquid Crystalline Elastomers in Oxygen‐Rich Environments

Liquid crystal elastomers (LCEs) are soft materials that undergo large anisotropic shape change in response to stimuli. Rational organization of the local director field can impart spatial control of the strain profile, enabling stretch‐based deformation capable of nearly 20 J kg^?1 of output force. LCEs are increasingly being considered in end‐use applications in robotics, therapeutics, and optics. Here, a new synthetic approach is introduced to prepare LCEs composed of main chain mesogens via the cationic photopolymerization of the epoxy liquid crystal monomer (LCM). This examination details the optical, mechanical, and thermal properties of epoxide‐based LCEs as a function of spacer length (3, 6, or 11 carbons). The oxygen insensitivity of the cationic photopolymerization of these monomers makes this approach particularly attractive for implementation with emerging additive manufacturing techniques. This contribution focuses on microstructuring LCEs via 2‐photon direct laser writing (2P‐DLW). A custom heated cell facilitated 2P‐DLW of the aligned LCE epoxy resin melts to fabricate diverse geometric arrays. Enabled by the orthogonality of the reaction chemistry, hybrid and microstructured material compositions are prepared via the encapsulation of LCE epoxy micropatterns with free‐radical polymerization of acrylate‐based LCEs. The distinct thermomechanical response of the hybridized and microstructured LCE composites enables local and spatially controlled actuation.