Enceladus Plume Density from Cassini Spacecraft Attitude Control Data.

The plumes of Enceladus are of interest both as a geophysical phemonenon, and as an astrobiological opportunity for sampling internal material. Here we report measurements of the total mass density (gas plus dust, a combination not reported before except in the engineering literature) deduced from telemetry of Cassini's Attitude and Articulation Control System (AACS), as the spacecraft's thrusters or reaction wheels worked to maintain the desired attitude in the presence of gas drag torques during close flybys. The drag torque shows good agreement with the water vapor density measured by other instruments during the E5 encounter, but indicates a rather higher mass density on other passes (E3,E14), possibly indicating variations in gas composition and/or gas:dust ratio. The spacecraft appears to have intercepted about 0.2 grams of material, on flyby E21 in October 2015 indicating a peak mass density of ~5.5×10-11 kgm-3, the highest of all the flybys measured (E3,E5,E7,E9,E14,E21).

Saturn's magnetic field revealed by the Cassini Grand Finale.

During 2017, the Cassini fluxgate magnetometer made in situ measurements of Saturn's magnetic field at distances ~2550 ± 1290 kilometers above the 1-bar surface during 22 highly inclined Grand Finale orbits. These observations refine the extreme axisymmetry of Saturn's internal magnetic field and show displacement of the magnetic equator northward from the planet's physical equator. Persistent small-scale magnetic structures, corresponding to high-degree (>3) axisymmetric magnetic moments, were observed. This suggests secondary shallow dynamo action in the semiconducting region of Saturn's interior. Some high-degree magnetic moments could arise from strong high-latitude concentrations of magnetic flux within the planet's deep dynamo. A strong field-aligned current (FAC) system is located between Saturn and the inner edge of its D-ring, with strength comparable to the high-latitude auroral FACs.

Maximum Quantity of Bone Available for Harvest From the Anterior Iliac Crest, Posterior Iliac Crest, and Proximal Tibia Using a Standardized Surgical Approach: A Cadaveric Study.

PURPOSE: The 3 most common sites for obtaining autogenous bone grafts are the anterior iliac crest (AIC), posterior iliac crest (PIC), and proximal tibia (PT). The purpose of this study was to determine the maximum amount of corticocancellous bone that could be harvested from the AIC, PIC and PT when using a standardized surgical approach. MATERIALS AND METHODS: The maximum volume of cortical and cancellous bone from the AIC, PIC, and PT was harvested from 44 cadavers using approaches from a review of the literature. Uncompressed and compressed corticocancellous bone volumes were measured by water volume displacement. Bivariate analyses of bone volumes, gender, and medical comorbidities were performed using the exact Wilcoxon rank-sum test. A general linear model using ranks was used to assess the effect of gender, medical comorbidity, and site separately for total uncompressed and compressed bone measurements. RESULTS: Forty-two AIC corticocancellous grafts provided an uncompressed total average of 26.29 mL and a compressed total average of 20.58 mL. Thirty-three PIC grafts yielded a total average of 33.82 mL of uncompressed bone and 24.11 mL of compressed. Thirty-eight PT samples provided a total average of 18.11 mL of uncompressed bone and 9.03 mL of compressed bone. No statistically relevant correlations were found between compressed bone volumes and body mass index or age. No statistically relevant association was found between bone quantity and medical comorbidity for any of the graft sites. The average rank of bone volume per site after controlling for gender and medical comorbidity showed that the PIC yielded the most and the PT yielded the least compressed and uncompressed bone amounts (P < .001). CONCLUSION: Results indicate that the PIC has a larger maximum amount of corticocancellous bone than the AIC and PT with a standardized approach. The maximum volumes of attainable bone from the AIC, PIC, and PT were lower than commonly cited in the literature.

Assessment of graduate orthodontic programs in North America.

This study collected information on four main aspects of U.S. and Canadian orthodontic programs: demographic profiles of residents, requirements for graduation, graduate curriculum, and number of faculty and staff members. Program directors at seventy U.S. and Canadian orthodontic programs were invited to participate in a twenty-question survey and to distribute a ten-question survey to their residents. Twenty program directors and eighty-four residents completed the anonymous, online surveys on Qualtrics.com in July-August 2010. The average age of surveyed residents was 29.6 years of age; 73 percent were non-Hispanic white, with 14 percent Asian/Asian-American, 5 percent Hispanic, and 1 percent African American. A small percentage of residents (13 percent) were foreign-trained. The majority of residents (64 percent) were male. There was a wide variety of clinical and didactic requirements in the programs. Almost all programs emphasized treatment with functional appliances and clear aligners. An average of three full-time and ten part-time faculty members were dedicated to each residency program. This survey reveals a potential shortage of minority orthodontic residents currently being trained in orthodontic programs, in addition to several commonalities and differences among the programs' curricula, graduation requirements, and numbers of faculty and staff members. This preliminary survey will hopefully inspire measures to address the discrepancies revealed, particularly the lack of minority students and full-time faculty members.

Patellar metastatic melanoma in a 13-year-old boy.

The incidence of melanoma in US adults is approximately 1.5 per million, with 2% to 5% of patients developing metastatic disease. In children, melanoma is distinctly uncommon, and metastatic disease occurs even more seldom. This case report, the first of a patellar lesion as the initial presentation of metastatic melanoma in a pediatric patient, highlights use of patellectomy and intraoperative radiation therapy in obtaining palliative local control while avoiding periarticular functional morbidity.

A simulation study to assess the sensitivity of a forest health monitoring network to outbreaks of defoliating insects.

The sensitivity of the United States Forest Health Monitoring network to outbreaks of defoliating insects was examined by means of a simulation study. A model constructed specifically for the study was used to generate a wide variety of defoliation patterns in forested landscapes. Forest configuration was that of Minnesota, USA, as expressed by the GAP land cover classification. Combinations of model parameters were based on a Latin Hypercube sample. The relationship between the average number of plots defoliated and outbreak characteristics was then examined via multiple regression. Both theoretical and model results pointed to a strong, linear relationship between the average number of plots defoliated and outbreak size. Model results provided additional insight, suggesting a significant relationship between the average number of plots defoliated and other outbreak characteristics after outbreak size was taken into account.

Process-based models for forest ecosystem management: current state of the art and challenges for practical implementation.

Recent progress toward the application of process-based models in forestmanagement includes the development of evaluation and parameter estimation methods suitable for models with causal structure, and the accumulation of data that can be used in model evaluation. The current state of the art of process modeling is discussed in the context of forest ecosystem management. We argue that the carbon balance approach is readily applicable for projecting forest yield and productivity, and review several carbon balance models for estimating stand productivity and individual tree growth and competition. We propose that to develop operational models, it is necessary to accept that all models may have both empirical and causal components at the system level. We present examples of hybrid carbon balance models and consider issues that currently require incorporation of empirical information at the system level. We review model calibration and validation methods that take account of the hybrid character of models. The operational implementation of process-based models to practical forest management is discussed. Methods of decision-making in forest management are gradually moving toward a more general, analytical approach, and it seems likely that models that include some process-oriented components will soon be used in forestry enterprises. This development is likely to run parallel with the further development of ecophysiologically based models.