[1] In September 2009 we observed a much different sea icescape in the Southern Beaufort Sea than anticipated, based on remotely sensed products. Radarsat derived ice charts predicted 7 to 9 tenths multi-year (MY) or thick first-year (FY) sea ice throughout most of the Southern Beaufort Sea in the deep water of the Canada Basin. In situ observations found heavily decayed, very small remnant MY and FY floes interspersed with new ice between floes, in melt ponds, thaw holes and growing over negative freeboard older ice. This icescape contained approximately 25% open water, predominantly distributed in between floes or in thaw holes connected to the ocean below. Although this rotten ice regime was quite different that the expected MY regime in terms of ice volume and strength, their near-surface physical properties were found to be sufficiently alike that their radiometric and scattering characteristics were almost identical.

IMPORTANCE Approximately 5% to 15% of patients with COVID-19 require invasive mechanical ventilation (IMV) and, at times, tracheostomy. Details regarding the safety and use of tracheostomy in treating COVID-19 continue to evolve.OBJECTIVE To evaluate the association of tracheostomy with COVID-19 patient outcomes and the risk of SARS-CoV-2 transmission among health care professionals (HCPs).

Geophysical controls on C band polarimetric backscatter from the discrete surface cover types which comprise advanced melt first‐year sea ice (FYI): snow covered ice, bare ice, and melt pond; are assessed using polarimetric radar scatterometry from test sites representing high Arctic and marginal ice zones in the Canadian Arctic. Surface characterization data is used to evaluate the interaction of polarized radiation with each feature, and dominant scattering mechanisms are assessed in a regional context. High‐resolution time series (diurnal) scatterometry and coincident atmospheric boundary layer profile data are used to explain linkages between ice‐atmosphere interactions and polarimetric backscatter in a marginal ice zone. The co‐polarization ratio for FYI melt ponds is shown to be distinct from snow covered ice or bare ice during early and peak phases of advanced melt, making it a candidate parameter for the unambiguous detection of pond formation and the inversion of melt pond fraction. The ratio displays an increasing trend with radar incidence angle in a manner consistent with Bragg surface scattering theory, though it is not predictable by a Bragg model. Cross‐polarization backscatter intensity shows potential for discriminating the onset and duration of freeze events in a marginal ice zone, due to dominant backscatter from the snow cover adjacent to melt ponds. Preliminary results here outline the potential of covariance matrix derived polarimetric measurements for the inversion of advanced melt sea ice geophysical parameters, and provide a basis for the investigation of distributed targets in late season spaceborne polarimetric SAR scenes.

A49sparse data structures. Separation often leads to failure in convergence of maximum likelihood models or unrealistic parameter estimates with wide confidence intervals. Therefore, the study objective is to compare the empirical performance of alternative methods for modeling sparse data in the context of small sample sizes: Firth-bias corrected logistic regression, exact logistic regression, penalized logistic regressions macro implemented in STATA, removal of the variable causing separation, and a Bayesian logistic model with a weakly informative prior (WIP). METHODS: HIPAA compliant diabetes patient records were used for determining factors associated with exposure to Medication Therapy Management (MTM) services at high frequency. Potential predictors of MTM visit frequency included age, gender, medication regimen complexities and presence of diabetes-related complications. This dataset had a small sample size (n=121) and exhibited separation problem; all patients in the high visit frequency group had diabetes with complexity. We compared the results of the Bayesian model with a WIP (coefficients are assigned a N(0,1.38) prior) to results of deleting the problematic variable, exact logistic regression and two different algorithms for penalized log likelihood functions (Firth's Bias-Correction in SAS and a STATA-Macro based routine). RESULTS: The Bayesian model with WIP produced odds ratio estimates of high frequency group membership based on diabetes complexity within expected range of treatment effects and plausible confidence intervals OR=4.64 (CI:0.98, 24.58). Among other models, only Firth-Bias model converged but parameter estimates and confidence intervals were unrealistically large OR=210.9 (CI:1.83, >999.99). Removal of the problematic variable (diabetes complexity) from the model prevented assessment of its effect on the probability of high visit frequency membership. CONCLUSIONS: Bayesian models with WIP represent a useful tool for modeling health outcomes sparse data with small sample size.

Sea ice dynamic and thermodynamic processes are important and highly variable elements of the marginal ice zone (MIZ). This study examines the detection and classification of statistically separable sea ice classes in the MIZ through a range of temporal and spatial scales. A helicopter‐based laser system was used to obtain large‐scale and a ship‐based laser profiler to identify small‐scale roughness types, respectively. The analysis of variance of surface height data from helicopter‐ and ship‐based laser systems, active microwave (AMW) C‐band backscattering data and passive microwave (PMW) (37 and 89 GHz) brightness temperature data reveal different classes that statistically differ from one another. We found significant statistical difference in variances in AMW data with six classes that differ in VV polarization, three classes in VH polarization, and five classes in HH polarization in the MIZ (e.g. snow‐covered first‐year ice, ice rubble, pancake ice, frost flowers, melt pond, flooded ice, and ice edge) of southeastern Beaufort Sea. The PMW emission was not as effective at discrimination, yielding only one statistically separable class. The results can potentially be extended to satellite‐based investigations of the MIZ at regional scales. Copyright © 2012 John Wiley & Sons, Ltd.