SeaWiFS Calibration and Algorithm Validation

This is the fourth annual report on NASA grant NAGW 3543, titled 'Sea-viewing Wide Field of view Sensor (SeaWiFS) calibration and algorithm validation'. An extended field experiment was conducted at Lake Tahoe in late July 1996 that involved: experimental verification of radiative transfer computations for various viewing geometries; retrieval of an effective aerosol optical depth height; calibration of a large field of view (FOV) sensor; and an evaluation of spatial non-uniformities in surface reflectance. The investigation and development of novel methods for the calibration of field radiometers at a variety of signal levels has been continued during the past year

SeaWiFS calibration and algorithm validation

A substantial amount of field research has been completed during this period (1 October 1994 - 31 October 1995). The applicability of different in-flight calibration methods was studied. In addition, various field instruments and new equipment were tested to appraise their usefulness during such calibration activities. The purposes and (expected) results of these field experiments are detailed in separate sections of this report. One section contains a synopsis of calibrations conducted over both land and water targets. A second section contains the results of an experiment conducted to determine the spatial uniformity of surface reflectance at Lake Tahoe, the chosen water calibration site. Advances were also made in the area of radiative transfer software development. An existing exact radiative transfer code, Successive Orders (SO), was modified to provide outputs of the radiance distribution at arbitrary altitudes above a selected calibration target. These modifications were needed to utilize the SO software in radiance-based sensor calibrations. Serious thought was given to the general applicability of various calibration techniques to calibrations conducted over water surfaces. In particular, the practicality of the radiance-based and reflectance-based methods of in-flight radiometric calibration was evaluated

Visualization and 3D Reconstruction of Flame Cells of Taenia solium (Cestoda)

BACKGROUND: Flame cells are the terminal cells of protonephridial systems, which are part of the excretory systems of invertebrates. Although the knowledge of their biological role is incomplete, there is a consensus that these cells perform excretion/secretion activities. It has been suggested that the flame cells participate in the maintenance of the osmotic environment that the cestodes require to live inside their hosts. In live Platyhelminthes, by light microscopy, the cells appear beating their flames rapidly and, at the ultrastructural, the cells have a large body enclosing a tuft of cilia. Few studies have been performed to define the localization of the cytoskeletal proteins of these cells, and it is unclear how these proteins are involved in cell function. METHODOLOGY/PRINCIPAL FINDINGS: Parasites of two different developmental stages of T. solium were used: cysticerci recovered from naturally infected pigs and intestinal adults obtained from immunosuppressed and experimentally infected golden hamsters. Hamsters were fed viable cysticerci to recover adult parasites after one month of infection. In the present studies focusing on flame cells of cysticerci tissues was performed. Using several methods such as video, confocal and electron microscopy, in addition to computational analysis for reconstruction and modeling, we have provided a 3D visual rendition of the cytoskeletal architecture of Taenia solium flame cells. CONCLUSIONS/SIGNIFICANCE: We consider that visual representations of cells open a new way for understanding the role of these cells in the excretory systems of Platyhelminths. After reconstruction, the observation of high resolution 3D images allowed for virtual observation of the interior composition of cells. A combination of microscopic images, computational reconstructions and 3D modeling of cells appears to be useful for inferring the cellular dynamics of the flame cell cytoskeleton

Sedentary time and peripheral artery disease: The Hispanic Community Health Study/Study of Latinos

Experimental evidence suggests that sedentary time (ST) may contribute to cardiovascular disease by eliciting detrimental hemodynamic changes in the lower limbs. However, little is known about objectively measured ST and lower extremity peripheral artery disease (PAD). We included 7,609 Hispanic/Latinos (ages 45-74) from the Hispanic Community Health Study/Study of Latinos. PAD was measured using the ankle brachial index (≤0.9). ST was measured using accelerometry. We used multivariable logistic regression to assess associations of quartiles of ST and PAD, and then used the same logistic models with restricted cubic splines to investigate continuous nonlinear associations of ST and PAD. Models were sequentially adjusted for traditional PAD risk factors, leg pain, and moderate- to vigorous-intensity physical activity (MVPA). Median ST was 12.2 h/d, and 5.4% of individuals had PAD. In fully adjusted restricted cubic splines models accounting for traditional PAD risk factors, leg pain, and MVPA, ST had a significant overall (P = .048) and nonlinear (P = .024) association with PAD. A threshold effect was seen such that time spent above median ST was associated with higher odds of PAD. That is, compared to median ST, 1, 2, and 3 hours above median ST were associated with a PAD odds ratio of 1.16 (95% CI = 1.02-1.31), 1.44 (1.06-1.94), and 1.80 (1.11-2.90), respectively. Among Hispanic/Latino adults, ST was associated with higher odds of PAD, independent of leg pain, MVPA, and traditional PAD risk factors. Notably, we observed a threshold effect such that these associations were only observed at the highest levels of ST

Stable morphology, but dynamic internal reorganisation, of interphase human chromosomes in living cells

Despite the distinctive structure of mitotic chromosomes, it has not been possible to visualise individual chromosomes in living interphase cells, where chromosomes spend over 90% of their time. Studies of interphase chromosome structure and dynamics use fluorescence in-situ hybridisation (FISH) on fixed cells, which potentially damages structure and loses dynamic information. We have developed a new methodology, involving photoactivation of labelled histone H3 at mitosis, to visualise individual and specific human chromosomes in living interphase cells. Our data revealed bulk chromosome volume and morphology are established rapidly after mitosis, changing only incrementally after the first hour of G1. This contrasted with the behaviour of specific loci on labelled chromosomes, which showed more progressive reorganisation, and revealed that “looping out” of chromatin from chromosome territories is a dynamic state. We measured considerable heterogeneity in chromosome decondensation, even between sister chromatids, which may reflect local structural impediments to decondensation and could potentially amplify transcriptional noise. Chromosome structure showed tremendous resistance to inhibitors of transcription, histone deacetylation and chromatin remodelling. Together, these data indicate steric constraints determine structure, rather than innate chromosome architecture or function-driven anchoring, with interphase chromatin organisation governed primarily by opposition between needs for decondensation and the space available for this to happen