Constant propellant use rendezvous scenario across a launch window for refueling missions

Active rendezvous of an unmanned spacecraft with the Space Transportation System (STS) Shuttle for refueling missions is investigated. The operational constraints facing both the maneuvering spacecraft and the Shuttle during a rendezvous sequence are presented. For example, the user spacecraft must arrive in the generic Shuttle control box at a specified time after Shuttle launch. In addition, the spacecraft must be able to initiate the transfer sequence from any point in its orbit. The standard four-burn rendezvous sequence, consisting of two Hohmann transfers and an intermediate phasing orbit, is presented as a low-energy solution for rendezvous and retrieval missions. However, for refueling missions, the Shuttle must completely refuel the spacecraft and return to Earth with no excess fuel. This additional constraint is not satisfied by the standard four-burn sequence. Therefore, a variation of the four-burn rendezvous, the constant delta-V scenario, was developed to satisfy the added requirement

Breeding and genetics (1993)

New 9/93/7M

Crossbreeding systems for small herds of beef cattle (1993)

Crossbreeding in commercial beef cattle production improves efficiency through heterosis and breed complementation. Heterosis or hybrid vigor is an advantage in performance of crossbreds compared to the average performance of the parental breeds. Heterosis is particularly strong for traits that are lowly heritable such as conception rate, preweaning livability of calves and preweaning growth.Reviewed December 1993 -- Extension website

An optical coherence microscope for 3-dimensional imaging in developmental biology

An optical coherence microscope (OCM) has been designed and constructed to acquire 3-dimensional images of highly scattering biological tissue. Volume-rendering software is used to enhance 3-D visualization of the data sets. Lateral resolution of the OCM is 5 mm (FWHM), and the depth resolution is 10 mm (FWHM) in tissue. The design trade-offs for a 3-D OCM are discussed, and the fundamental photon noise limitation is measured and compared with theory. A rotating 3-D image of a frog embryo is presented to illustrate the capabilities of the instrument

Teaching Complex, In-Depth Programs

Changing demographics of rural Extension audiences create challenges to program delivery, and multiple delivery methods may be needed to effectively improve skills and knowledge of clients. We examined the effectiveness of different delivery methods and changes in client skills, knowledge and abilities as a result of a complex, in-depth program, the Virginia Cow/Calf Management Course. Almost 500 producers took the 5-month course. Changes were measured from pre- and post-course surveys. Skills easily employed by the producers were readily adopted. Experiential learning opportunities and written materials had the greatest impact on producers, while Web-based information and discussion groups were marginally effective

Tree mortality based fire severity classification for forest inventories: A Pacific Northwest national forests example

Determining how the frequency, severity, and extent of forest fires are changing in response to changes in management and climate is a key concern in many regions where fire is an important natural disturbance. In the USA the only national-scale fire severity classification uses satellite image change-detection to produce maps for large (>400 ha) fires, and is generated by the Monitoring Trends in Burn Severity (MTBS) program. It is not clear how much forested area burns in smaller fires or whether ground-based fire severity estimates from a statistical sample of all forest lands might provide additional, useful information. We developed a tree mortality based fire severity classification using remeasured tree data from 10,008 plots in a probabilistic survey of National Forests System (NFS) lands in Oregon and Washington, using 8 tree mortality and abundance metrics. We estimate that 12.5% (±0.7% SE) of NFS forest lands in the region experienced a fire event during 1993–2007, with an annual rate of 0.96% (±0.05%). An estimated 6.5% of forest lands burned at High Severity or Moderate Severity; 2.1% burned at Very Low severity or only experienced surface or understory fire. A total of 358 of the 507 burned plots were within the MTBS perimeters, with ∼45% having equivalent severity classifications; but for ∼51% of the plots the MTBS classifications suggested lower severity than the tree-mortality based classes. Based on events recorded on plots and the inventory design, we estimate that 20.9% of the forested NFS lands experiencing fires, either wildfires or prescribed burns, were not in the MTBS maps. Tree mortality based fire severity classifications, combined with remotely-sensed and management information on timing and treatments, could be readily applied to nationally-consistent Forest Inventory and Analysis (FIA) data to provide improved monitoring of fire effects anywhere in the USA sampled by remeasured FIA inventories.Keywords: Fire effects, Tree remeasurement, Wildfire, Probabilistic sampling, Forest monitoring, Forest Inventory and Analysis (FIA

Carbon stocks and changes on Pacific Northwest national forests and the role of disturbance, management, and growth

The National Forest System (NFS) of the United States plays an important role in the carbon cycle because these lands make up a large proportion of the forested land in the country and commonly store more wood per unit area than other forest ownerships. In addition to sustaining natural resources, these lands are managed for multiple objectives that do not always align with maximizing carbon (C) sequestration. The objectives of this study were to determine C stocks and flux in measured pools on Pacific Northwest Region NFS lands and the major ecological drivers of C flux. We compiled tree, dead wood, and understory vegetation data from 11,435 systematically-placed inventory plots and estimated growth, mortality, decay, removals, and disturbance events based on two full measurements spanning 1993–2007. The area of NFS-administered lands increased by 0.3% during this period and the area in formally-designated protected status increased by 0.7%. There was 1293 Tg C (±11.2 Tg standard error) in non-soil C stocks at the first measurement, which increased by 45 ± 2.2 Tg (3.4%), with 59% of the increase in the live tree pool and the remainder in the dead tree pools. C stocks followed broad regional patterns in productivity while C flux varied at local scales. Fires affected <1% of the forested area per year and were most prevalent in Wilderness areas. Fires reduced C stocks on burned plots by only 9%, and had a negligible effect on the region as a whole. Most tree harvest on NFS lands in the region consisted of partial harvest and had comparable impacts to fire during this period. C sequestration rates were higher (1.2 ± 0.09 Mg/ha/yr) on the west side of the Cascade Mountains, and primarily stayed in the live tree pool, compared to lower rates (0.5 ± 0.04 Mg/ha/yr) east of the Cascades where most of the increase was seen in the down wood pool. We discuss challenges to estimating forest ecosystem carbon stocks, which requires the application of a large number of equations and parameters for measured and unmeasured components, some with scant empirical support. Improved measurements and biomass models applied to networks of permanent plots would enable improved ground-based estimates of the drivers and components of regional changes in C.Keywords: Carbon sequestration, Forest inventory, Harvest, Dead woodKeywords: Carbon sequestration, Forest inventory, Harvest, Dead woo

Precision of bone mechanoregulation assessment in humans using longitudinal high-resolution peripheral quantitative computed tomography in vivo.

Local mechanical stimuli in the bone microenvironment are essential for the homeostasis and adaptation of the skeleton, with evidence suggesting that disruption of the mechanically-driven bone remodelling process may lead to bone loss. Longitudinal clinical studies have shown the combined use of high-resolution peripheral quantitative computed tomography (HR-pQCT) and micro-finite element analysis can be used to measure load-driven bone remodelling in vivo; however, quantitative markers of bone mechanoregulation and the precision of these analyses methods have not been validated in human subjects. Therefore, this study utilised participants from two cohorts. A same-day cohort (n = 33) was used to develop a filtering strategy to minimise false detections of bone remodelling sites caused by noise and motion artefacts present in HR-pQCT scans. A longitudinal cohort (n = 19) was used to develop bone imaging markers of trabecular bone mechanoregulation and characterise the precision for detecting longitudinal changes in subjects. Specifically, we described local load-driven formation and resorption sites independently using patient-specific odds ratios (OR) and 99 % confidence intervals. Conditional probability curves were computed to link the mechanical environment to the remodelling events detected on the bone surface. To quantify overall mechanoregulation, we calculated a correct classification rate measuring the fraction of remodelling events correctly identified by the mechanical signal. Precision was calculated as root-mean-squared averages of the coefficient of variation (RMS-SD) of repeated measurements using scan-rescan pairs at baseline combined with a one-year follow-up scan. We found no significant mean difference (p < 0.01) between scan-rescan conditional probabilities. RMS-SD was 10.5 % for resorption odds, 6.3 % for formation odds, and 1.3 % for correct classification rates. Bone was most likely to be formed in high-strain and resorbed in low-strain regions for all participants, indicating a consistent, regulated response to mechanical stimuli. For each percent increase in strain, the likelihood of bone resorption decreased by 2.0 ± 0.2 %, and the likelihood of bone formation increased by 1.9 ± 0.2 %, totalling 38.3 ± 1.1 % of strain-driven remodelling events across the entire trabecular compartment. This work provides novel robust bone mechanoregulation markers and their precision for designing future clinical studies

Preparing tomorrow's teachers to use technology (PT3) at Boston University through faculty development: assessment of three years of the project

The Boston University PT3 grant project proposed first to train faculty to use technology and then to sustain the gained expertise in a curriculum development project. Education faculty gains in integrating technology into their teaching and their modeling of that use were clearly demonstrated in phase one of the project (the initial two years of the project). In phase two (the third year), faculty were challenged to produce innovative, interdisciplinary curriculum development projects investigating judgment in their discipline. Prototypes of the Judgment Curriculum produced in phase two of the project demonstrate an intersection of technology competence and innovative, question‐driven instruction. Preliminary data show strong gains in faculty use of technology in their teaching and in faculty requirements that their students use technology in education coursework. However, continued development of the Judgment Curriculum lessons remains a challenge