Effects of fuels treatments and wildfire on understory species and fuels in the ponderosa pine zone of the Colorado Front Range

The first clear indication that unnaturally dense forest conditions existed in ponderosa pine – Douglas-fir forests of the Colorado Front Range was the Buffalo Creek Fire, a large, catastrophic wildfire that burned in 1996. Ongoing research in the Front Range indicated that the Buffalo Creek Fire likely would have burned very differently under pre-settlement forest conditions; early photographs and written descriptions, as well as fire history and stand reconstruction data, all suggested that historically these forests were characterized by a matrix of low-density forests and shrubland or grassland openings that was created and maintained by a mixed-severity fire regime. As a result of the Buffalo Creek Fire and several other large and intense wildfires in the Colorado Front Range – Bobcat Gulch and Hi Meadows in 2000, and Schoonover, Snaking, and Hayman in 2002 – managers began to plan forest restoration treatments to reduce the risk of unnaturally large, stand-replacing fires, and to return ecological sustainability to the landscape through research-guided restoration actions. Managers and others are obviously concerned about how both forest restoration treatments and intense wildfires impact the forest overstory, and these impacts are widely studied. Less studied, though, are how these disturbances impact the forest floor – in terms of both understory species composition and surface fuels that would carry a future fire. As wildfires continue to occur in the Front Range, and as forest restoration treatments continue to expand to much larger land areas, it is becoming critical for forest managers to understand how both restoration actions and wildfire influence forest understories and fuel loadings. Our objective for this project was to conduct a holistic ecosystem evaluation of the changes in forest understory communities, fuel characteristics, and potential fire behavior that result from restoration activities and wildfires. To address this objective, we established one study area within a recently treated forest, one study area within a forest recently burned by wildfire, and three study areas within untreated, unburned reference forests. All study areas were located within the Upper South Platte Watershed of the Pike National Forest, Colorado, USA, approximately 60 km southwest of Denver. Our treated study area was located in an area that was mechanically thinned in late 2002 and early 2003. The primary management objective was to reduce the risk of crown fires and to restore sustainable and ecologically appropriate overstory conditions by decreasing stand density, minimizing fuel ladders, and increasing canopy openings. Small canopy trees were sheared near ground-level using a boom-mounted hot saw on a tracked vehicle. Downed tree tops and limbs were crushed and further broken apart by driving over them with the tracked vehicle. In early 2003, where terrain and financial resources permitted, hand crews used chain saws to create additional openings and further reduce basal areas. The hand-cut trees were subsequently cut-to-length, piled, and burned. Our wildfire study area was located within the Hayman Fire, which burned 55,800 ha in 2002. Approximately half of the Hayman Fire area burned as a stand-replacing crown fire, much of it in a single day of extreme weather. The other half of the area burned as a mixed-severity fire, creating a mosaic of burn severities on the landscape. Our study area was situated in a transitional zone between these two fire behaviors, and therefore contained components of each. Three reference study areas were established near the treated and wildfire study areas to provide information about the untreated and unburned condition. The reference sites had not been disturbed by fire or other agents in the preceding five years. Each study area contained fifteen 0.1-ha plots, which were stratified by aspect (north, south, and east/west) to minimize the potential effects of topography on our findings. In each plot we measured understory species composition and cover, surface fuel loading, and overstory structure. Understory data were measured in all plots in 2004, 2005, and 2006, while surface fuels and overstory data were generally only measured in one of the three years. Prefire understory, surface fuel, and overstory data collected in 1997 were also available for the Hayman Fire plots

A method to determine regional mechanical left ventricular dyssynchrony based on high temporal resolution short axis SSFP cine images

Left ventricular (LV) mechanical dyssynchrony has been proposed as a parameter to select patients for cardiac resynchronization therapy (CRT) [Bax et al JACC 2005].Several recent studies have shown that placing the LV pacing lead in the most delayed regions yields a better response to CRT [Ansalone et al JACC 2002]. However, most imaging-based methods assess global LV dyssynchrony providing a single value for the entire LV. Regional maps of LV dyssynchrony are required for planning LV lead placement. The objective of this study was to develop a method to create a map of regional left ventricular mechanical dyssynchrony based on short-axis SSFP cine images

Utilization of the Multiple Access Communications Satellite (MACSAT) in Support of Tactical Communications

Two MACSATs were launched on May 9, 1990 on a Scout launch vehicle from Vandenberg Air Force Base, California. After a short on-orbit check-out, these research and development satellites were placed into service providing operational communications support to 2d Marine Aircraft Wing units deployed to the Persian Gulf in support of Operations Desert Shield and Desert Storm. This support was provided from August 1990 until Operation Desert Storm was completed in April 1991. During this time, many lessons were learned that are directly applicable to the design and fielding of future small tactical communications satellites. This paper will highlight some of the lessons learned from supporting Operation Desert Shield, as well as other communications support missions

Characterization of the size and location of dyssynchronous regions in patients undergoing CRT

The amount and location of left ventricular (LV) mechanical dyssynchrony affects an individual’s ability to respond positively to cardiac resynchronization therapy (CRT) [Bax et al JACC 2005]. By using high temporal resolution short-axis cines, it is possible to derive radial motion curves throughout the LV. These radial motion curves can be used to create maps showing dyssynchronous regions in patients enrolled for CRT. The objective of this study was to characterize the size and location of areas of mechanical dyssynchrony in patients scheduled for CRT by comparing their radial wall motion curves to radial motion curves from normal subjects

Telemetric Blood Pressure Assessment in Angiotensin II-Infused ApoE\u3csup\u3e-/-\u3c/sup\u3e Mice: 28 Day Natural History and Comparison to Tail-Cuff Measurements

Abdominal aortic aneurysm (AAA) is a disease of the aortic wall, which can progress to catastrophic rupture. Assessment of mechanical characteristics of AAA, such as aortic distensibility, may provide important insights to help identify at-risk patients and understand disease progression. While the majority of studies on this topic have focused on retrospective patient data, recent studies have used mouse models of AAA to prospectively evaluate the evolution of aortic mechanics. Quantification of aortic distensibility requires accurate measurement of arterial blood pressure, particularly pulse pressure, which is challenging to perform accurately in murine models. We hypothesized that volume/pressure tail-cuff measurements of arterial pulse pressure in anesthetized mice would have sufficient accuracy to enable calculations of aortic distensibility with minimal error. Telemetry devices and osmotic mini-pumps filled with saline or angiotensin-II were surgically implanted in male apolipoprotein-E deficient (ApoE-/-) mice. Blood pressure in the aortic arch was measured continuously via telemetry. In addition, simultaneous blood pressure measurements with a volume/pressure tail-cuff system were performed under anesthesia at specific intervals to assess agreement between techniques. Compared to controls, mice infused with angiotensin-II had an overall statistically significant increase in systolic pressure, with no overall difference in pulse pressure; however, pulse pressure did increase significantly with time. Systolic measurements agreed well between telemetry and tail-cuff (coefficient of variation = 10%), but agreement of pulse pressure was weak (20%). In fact, group-averaged pulse pressure from telemetry was a better predictor of a subject\u27s pulse pressure on a given day than a simultaneous tail-cuff measurement. Furthermore, these approximations introduced acceptable errors (15.1 ± 12.8%) into the calculation of aortic distensibility. Contrary to our hypothesis, we conclude that tail-cuff measures of arterial pulse pressure have limited accuracy. Future studies of aneurysm mechanics using the ApoE-/-/angiotensin-II model would be better in assuming pulse pressure profiles consistent with our telemetry findings instead of attempting to measure pulse pressure in individual mice