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No description available.

The United States Forest Service (USFS) Forest Inventory and Analysis (FIA) program provides a diverse selection of data used to assess the status of the nation’s forested areas using sample locations dispersed throughout the country. Airborne, and more recently, terrestrial lidar (light detection and ranging) systems are capable of producing accurate measurements of individual tree dimensions and also possess the ability to characterize three-dimensional vertical forest structure. This study investigates the potential of airborne and terrestrial scanning lidar systems for modeling forest volume and aboveground biomass on FIA subplots in the Malheur National Forest, eastern Oregon. A methodology for the creation of five airborne lidar metric sets (four point cloud-based and one individual tree based) and four terrestrial lidar metric sets (three height-based and one distance-based) is presented. Metrics were compared to estimates of subplot aboveground biomass and gross volume derived from FIA data using national and regional allometric equations respectively. Simple linear regression models from the airborne lidar data accounted for 15 percent of the variability in subplot biomass and 14 percent of the variability in subplot volume, while multiple linear regression models increased these amounts to 29 percent and 25 percent, respectively. When subplot estimates of biophysical parameters were scaled to the plot-level and compared with plot-level lidar metrics, simple linear regression models were able to account for 60 percent of the variability in biomass and 71 percent of the variation in volume. Terrestrial lidar metrics produced moderate results with simple linear regression models accounting for 41 percent of the variability in biomass and 46 percent of the variability in volume, with multiple linear regression models accounting for 71 percent and 84 percent, respectively. Results show that: (1) larger plot sizes help to mitigate errors and produce better models; and (2) a combination of height-based and distance-based terrestrial lidar metrics has the potential to estimate biomass and volume on FIA subplots.

GPU-based raycasting is the state-of-the-art rendering technique for interactive volume visualization. The ray traversal is usually implemented in a fragment shader, utilizing the hardware in a way that was not originally intended. New programming interfaces for stream processing, such as CUDA, support a more general programming model and the use of additional device features, which are not accessible through traditional shader programming. In this paper we propose a slab-based raycasting technique that is modeled specifically to use these features to accelerate volume rendering. This technique is based on experience gained from comparing fragment shader implementations of basic raycasting to implementations directly translated to CUDA kernels. The comparison covers direct volume rendering with a variety of optional features, e.g., gradient and lighting calculations. Our findings are supported by benchmarks of typical volume visualization scenarios. We conclude that new stream processing models can only gain a small performance advantage when directly porting the basic raycasting algorithm. However, they can be advantageous through novel acceleration methods which use the hardware features not available to shader implementations.

AIM: To contrast the effects of various modifications of body fluid volumes on thirst as reported by healthy volunteers. METHODS: Ten male volunteers aged between 19 and 37 years (mean 22 years) underwent four experiments each, which comprised infusion of 400-800 mL of acetated Ringer’s solution and intake of 600 mL of tap water. Half of the experiments were preceded by volume depletion (median 1.7 L) with furosemide. A visual analogue scale (0-100 mm) was used to assess perceived thirst during each experiment. RESULTS: Volume depletion (P < 0.001) and tap water (P < 0.03) both affected thirst by 13 mm per L of fluid, whereas spontaneous diuresis and infusion of Ringer’s acetate did not significantly change the thirst rating (multiple regressions). More detailed analyses showed that the volume depletion increased the median (25th-75th percentiles) thirst rating from 28 mm (21-43) to 59 mm (46-72, P < 0.001) while no change occurred in those who were only slightly thirsty (< 30 mm) before the volume depletion began. Ringer’s solution alleviated thirst in those who were very thirsty, but tended to increase thirst in the volunteers who were not thirsty before the infusion. Similarly, hydration with tap water decreased thirst (by 24 mm, P < 0.04) in those who were thirsty (> 60 mm) while the others reported no change. CONCLUSION: The change in thirst rating during volume depletion, administration of Ringer’s acetate, and ingestion of tap water were all dependent on the thirst rating obtained when the manipulation of the body fluid volume was initiated.

In this work, we describe our recent efforts aimed at determining the mechanism of signal change for a diffraction-based sensor (DBS) system. The DBS detects analyte-binding events by monitoring the change in diffraction efficiency that takes place when analyte molecules adsorb to target molecules that have been patterned onto a surface. The exact parameters that affect the intensity of the diffraction intensity are currently not well understood.<p>In this work, the formalism used to describe the behaviour of volume-phase holography is used to understand the parameters that effect the diffraction intensity. It is hypothesized that the major factors that effect the diffraction intensity are the differences in optical path length between the wave trains that reflect off the diffraction grating and those that reffect off the substrate surface. Also key is the difference in refractive index between the two media. Two approaches were developed to investigate this hypothesis; the first was to develop a series of gratings of varying thickness using polyelectrolyte multilayers. The indices of refraction of these gratings were adjusted by the incorporation of charged gold nanoparticles. Since DBS systems operate by monitoring the binding of analyte molecules, a second series of experiments were developed to investigate the changes in diffraction intensity as micometer sized carboxylated beads were loaded onto an avidin grating. The first aspect that was investigated was the effect of adding more particles onto the grating surface on diffraction intensity. Second, the extent to which the particles reduced the periodicity of the diffraction grating, and the effect on the observed intensity of the diffraction signal were also investigated. Finally, this work shows the first use of a DBS system to extract the rate of and the maximum surface coverage of a specific binding reaction.

Astrocytes, the major type of non-neuronal cells in the brain, play an important functional role in the brains extracellular potassium (K+) and pH homeostasis. Pathological brain states have been shown to cause astrocyte swelling. However, these volume changes have never before been verified to occur in response to physiological activity. In the present thesis, two-photon laser scanning microscopy was used to visualize real-time astrocyte volume changes in the stratum radiatum of the CA1 region of the hippocampus. Astrocyte somas and primary processes were observed to swell by 19.0±0.9% in response to a physiological (3 mM) increase in the concentration of extracellular K+. Astrocyte swelling was partially mediated by K+ influx through inwardly rectifying K+ channels (Kir), as their inhibition resulted in a significant decrease of the increased K+ induced astrocyte swelling (13.9±0.9%). In addition, the bicarbonate ion (HCO3-) was found to play a significant role in the increased K+ induced astrocyte swelling. The astrocyte swelling was significantly decreased when the influx of HCO3- was decreased in 1) a HCO3- free extracellular solution (5.4±0.7%), 2) in the presence of an extracellular carbonic anhydrase inhibitor (11.4±0.6% ), and 3) when the activity of the sodium-bicarbonate cotransporter (NBC) was blocked (8.3±0.7%) . Conversely, astrocytes were found to shrink by 7.7±0.5% in response to ã-Amino-butyric Acid (GABA) receptor activation. GABAA receptor mediated astrocyte shrinkage was significantly decreased to 5.0±0.6% when HCO3- efflux was reduced. Furthermore, in this thesis it was shown for the first time that astrocytes swell in response to neuronal stimulation (4.0±0.4%). This activity induced astrocyte swelling was significantly decreased to 1.5±0.2% in a HCO3- free extracellular solution. These astrocyte volume changes may have important implications for the regulation of brain activity under both physiological and pathological brain states.

In this work, we describe our recent efforts aimed at determining the mechanism of signal change for a diffraction-based sensor (DBS) system. The DBS detects analyte-binding events by monitoring the change in diffraction efficiency that takes place when analyte molecules adsorb to target molecules that have been patterned onto a surface. The exact parameters that affect the intensity of the diffraction intensity are currently not well understood.<p>In this work, the formalism used to describe the behaviour of volume-phase holography is used to understand the parameters that effect the diffraction intensity. It is hypothesized that the major factors that effect the diffraction intensity are the differences in optical path length between the wave trains that reflect off the diffraction grating and those that reffect off the substrate surface. Also key is the difference in refractive index between the two media. Two approaches were developed to investigate this hypothesis; the first was to develop a series of gratings of varying thickness using polyelectrolyte multilayers. The indices of refraction of these gratings were adjusted by the incorporation of charged gold nanoparticles. Since DBS systems operate by monitoring the binding of analyte molecules, a second series of experiments were developed to investigate the changes in diffraction intensity as micometer sized carboxylated beads were loaded onto an avidin grating. The first aspect that was investigated was the effect of adding more particles onto the grating surface on diffraction intensity. Second, the extent to which the particles reduced the periodicity of the diffraction grating, and the effect on the observed intensity of the diffraction signal were also investigated. Finally, this work shows the first use of a DBS system to extract the rate of and the maximum surface coverage of a specific binding reaction.

Astrocytes, the major type of non-neuronal cells in the brain, play an important functional role in the brains extracellular potassium (K+) and pH homeostasis. Pathological brain states have been shown to cause astrocyte swelling. However, these volume changes have never before been verified to occur in response to physiological activity. In the present thesis, two-photon laser scanning microscopy was used to visualize real-time astrocyte volume changes in the stratum radiatum of the CA1 region of the hippocampus. Astrocyte somas and primary processes were observed to swell by 19.0±0.9% in response to a physiological (3 mM) increase in the concentration of extracellular K+. Astrocyte swelling was partially mediated by K+ influx through inwardly rectifying K+ channels (Kir), as their inhibition resulted in a significant decrease of the increased K+ induced astrocyte swelling (13.9±0.9%). In addition, the bicarbonate ion (HCO3-) was found to play a significant role in the increased K+ induced astrocyte swelling. The astrocyte swelling was significantly decreased when the influx of HCO3- was decreased in 1) a HCO3- free extracellular solution (5.4±0.7%), 2) in the presence of an extracellular carbonic anhydrase inhibitor (11.4±0.6% ), and 3) when the activity of the sodium-bicarbonate cotransporter (NBC) was blocked (8.3±0.7%) . Conversely, astrocytes were found to shrink by 7.7±0.5% in response to ã-Amino-butyric Acid (GABA) receptor activation. GABAA receptor mediated astrocyte shrinkage was significantly decreased to 5.0±0.6% when HCO3- efflux was reduced. Furthermore, in this thesis it was shown for the first time that astrocytes swell in response to neuronal stimulation (4.0±0.4%). This activity induced astrocyte swelling was significantly decreased to 1.5±0.2% in a HCO3- free extracellular solution. These astrocyte volume changes may have important implications for the regulation of brain activity under both physiological and pathological brain states.

A VOF based multiphase Lattice Boltzmann method that explicitly prescribes kinematic boundary conditions at the interface is developed. The advantage of the method is the direct control over the surface tension value. The details of the numerical method are presented. The Saffman instability, Taylor instability, and flow of deformable suspensions in a channel are used as example-problems to demonstrate the accuracy of the method. The method allows for relatively large viscosity and density ratios.