Studies of stratospheric particulates

A sophisticated computer model of polar stratospheric clouds was developed and used to study the properties of ice clouds. The model has recently been extended to investigate nitric acid clouds and ice clouds as well as their interactions with stratospheric gases. The model is now being applied to interpret data collected during recent expeditions to the Antarctic and the Arctic. Some work has also been done to understand the properties of noctilucent clouds and their implications for the chemistry and dynamics of the upper stratosphere

Stratospheric aerosol modification by supersonic transport operations with climate implications

The potential effects on stratospheric aerosois of supersonic transport emissions of sulfur dioxide gas and submicron size soot granules are estimated. An interactive particle-gas model of the stratospheric aerosol is used to compute particle changes due to exhaust emissions, and an accurate radiation transport model is used to compute the attendant surface temperature changes. It is shown that a fleet of several hundred supersonic aircraft, operating daily at 20 km, could produce about a 20% increase in the concentration of large particles in the stratosphere. Aerosol increases of this magnitude would reduce the global surface temperature by less than 0.01 K

The NASA-Ames Research Center stratospheric aerosol model. 2. Sensitivity studies and comparison with observatories

Sensitivity tests were performed on a one-dimensional, physical-chemical model of the unperturbed stratospheric aerosols, and model calculations were compared with observations. The tests and comparisons suggest that coagulation controls the particle number mixing ratio, although the number of condensation nuclei at the tropopause and the diffusion coefficient at high altitudes are also important. The sulfur gas source strength and the aerosol residence time are much more important than the supply of condensation nuclei in establishing mass and large particle concentrations. The particle size is also controlled mainly by gas supply and residence time. In situ observations of the aerosols and laboratory measurements of aerosols, parameters that can provide further information about the physics and chemistry of the stratosphere and the aerosols found there are provided

The NASA-AMES Research Center Stratospheric Aerosol Model. 1. Physical Processes and Computational Analogs

A time-dependent one-dimensional model of the stratospheric sulfate aerosol layer is presented. In constructing the model, a wide range of basic physical and chemical processes are incorporated in order to avoid predetermining or biasing the model predictions. The simulation, which extends from the surface to an altitude of 58 km, includes the troposphere as a source of gases and condensation nuclei and as a sink for aerosol droplets. The size distribution of aerosol particles is resolved into 25 categories with particle radii increasing geometrically from 0.01 to 2.56 microns such that particle volume doubles between categories

SPECTRAL DECOMPOSITION OF VERTICAL GROUND REACTION FORCE CURVES

INTRODUCTION - The vertical ground re- action force component typically has two peaks. The first peak (impact peak) is caused by the impact between the foot and the ground while the lower frequency second peak (active peak) is caused by the vertical braking of the body followed by vertical push-off. Bobbert et al. (1991) pro- posed a method of decomposing the VGRF into the contribution of the support leg and the rest of the body by double differentiation of segment center of mass position data. This decomposition allowed them to determine the magnitude of the impact peak independent of the rest of the curve. The purpose of this study was to investigate a method of decomposing the VGRF curve that does not require differentiation of position data. METHODOLOGY - Five male recreational runners completed 5 trials in 3 different run- ning shoes that differed only in the density of the midsole material. VGRF data were recorded from a force platform at 1000 Hz using an analogue to digital converter. A Fourier transform was performed on each trial An inverse transform was then per- formed twice - once using the frequencies below 3 Hz and once using the frequencies above 3 Hz. Figure 1 illustrates a typical decomposition of the force curve. Peak (PK) and time to peak (TPK) values were recorded for each curve of the decomposed VGRF curve. RESULTS AND DISCUSSION - The magnitudes and times of the impact and active peaks for the decomposed VGRF are presented in Table 1. The impact peak for the soft shoe had a greater magnitude than the medium or hard shoes. This may indi- cate that this shoe midsole experienced maximum compression or that the subjects perceived the soft midsole and adjusted their kinematics. There were essentially no differences in the active PK between the soft, medium and hard midsoles. Table 1. Mean values for decomposed VGRF variables. Midsole Soft Medium Hard Impact PK 240.1 212.8 238.7 Impact TPK 28.3 26.1 26.6 Active PK 1241.2 1233.4 1244.7 Active TPK 107.9 108.7 104.0 Since the impact peak component is of a higher frequency than the active compo- nent, the decomposed VGRF curves are comparable lo the curves of Bobbert et el. (1991). These results indicate that this pro-cedure can be used to separate the true impact characteristics of the VGRF from the remainder of the curve. REFERENCES Bobbert, M.F. et al. (1991). Calculation of vertical ground reaction force estimates during running from positional data. J Biomech, Vol 24: 12 pp. 1095-1 105

Folding studies of immunoglobulin-like β-sandwich proteins suggest that they share a common folding pathway

AbstractBackground: Are folding pathways conserved in protein families? To test this explicitly and ask to what extent structure specifies folding pathways requires comparison of proteins with a common fold. Our strategy is to choose members of a highly diverse protein family with no conservation of function and little or no sequence identity, but with structures that are essentially the same. The immunoglobulin-like fold is one of the most common structural families, and is subdivided into superfamilies with no detectable evolutionary or functional relationship.Results: We compared the folding of a number of immunoglobulin-like proteins that have a common structural core and found a strong correlation between folding rate and stability. The results suggest that the folding pathways of these immunoglobulin-like proteins share common features.Conclusions: This study is the first to compare the folding of structurally related proteins that are members of different superfamilies. The most likely explanation for the results is that interactions that are important in defining the structure of immunoglobulin-like proteins are also used to guide folding

Accuracy of a Web-based System for Monitoring Chronic Wounds

This study evaluated the accuracy of a store-and-forward telemedicine system for assessing the status of chronic wounds, including those surgically repaired. Digital photos and other patient and wound data were collected by a nurse using a laptop and transmitted via the Internet to a database, which organized and posted the data onto a web page for access by the telemedicine physician. Two Veterans' Affairs (VA) medical centers and two specialties (plastic surgery, physical medicine and rehabilitation) participated in the study. Study patients included inpatients and outpatients with pressure ulcers of stage II, III, or IV, plus outpatients with diabetic foot ulcers or venous stasis ulcers. All patients were assessed both in-person (the "gold standard") and with the telemedicine system using yes/no responses and a 5-point scale, respectively, on four diagnostic questions concerning wound healing and infection, based on AHCPR guidelines. A total of 70 patients were enrolled, with data collected on 430 visits: up to 6 visits per wound. Percentage agreement for all visits ranged from 67.1 for "not healing" to 88.8 for "cellulitis present." Sensitivity ranged from 0.32 for cellulitis to 0.63 for necrosis; and specificity ranged from 0.80 for necrosis to 0.91 for cellulitis. Although agreement of the telemedicine system was not high, it was not significantly less than interphysician agreement on in-person assessments. A relatively inexpensive store-and-forward telemedicine system for monitoring the status of chronic wounds has the potential to improve access to specialty care for patients who are not currently receiving routine monitoring by specialized nurses or physicians.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63181/1/153056203766437471.pd

Deep Space Gateway Science Opportunities

The NASA Life Sciences Research Capabilities Team (LSRCT) has been discussing deep space research needs for the last two years. NASA's programs conducting life sciences studies - the Human Research Program, Space Biology, Astrobiology, and Planetary Protection - see the Deep Space Gateway (DSG) as affording enormous opportunities to investigate biological organisms in a unique environment that cannot be replicated in Earth-based laboratories or on Low Earth Orbit science platforms. These investigations may provide in many cases the definitive answers to risks associated with exploration and living outside Earth's protective magnetic field. Unlike Low Earth Orbit or terrestrial locations, the Gateway location will be subjected to the true deep space spectrum and influence of both galactic cosmic and solar particle radiation and thus presents an opportunity to investigate their long-term exposure effects. The question of how a community of biological organisms change over time within the harsh environment of space flight outside of the magnetic field protection can be investigated. The biological response to the absence of Earth's geomagnetic field can be studied for the first time. Will organisms change in new and unique ways under these new conditions? This may be specifically true on investigations of microbial communities. The Gateway provides a platform for microbiology experiments both inside, to improve understanding of interactions between microbes and human habitats, and outside, to improve understanding of microbe-hardware interactions exposed to the space environment