Adapting western North American forests to climate change and wildfires: 10 common questions.

We review science-based adaptation strategies for western North American (wNA) forests that include restoring active fire regimes and fostering resilient structure and composition of forested landscapes. As part of the review, we address common questions associated with climate adaptation and realignment treatments that run counter to a broad consensus in the literature. These include the following: (1) Are the effects of fire exclusion overstated? If so, are treatments unwarranted and even counterproductive? (2) Is forest thinning alone sufficient to mitigate wildfire hazard? (3) Can forest thinning and prescribed burning solve the problem? (4) Should active forest management, including forest thinning, be concentrated in the wildland urban interface (WUI)? (5) Can wildfires on their own do the work of fuel treatments? (6) Is the primary objective of fuel reduction treatments to assist in future firefighting response and containment? (7) Do fuel treatments work under extreme fire weather? (8) Is the scale of the problem too great? Can we ever catch up? (9) Will planting more trees mitigate climate change in wNA forests? And (10) is post-fire management needed or even ecologically justified? Based on our review of the scientific evidence, a range of proactive management actions are justified and necessary to keep pace with changing climatic and wildfire regimes and declining forest heterogeneity after severe wildfires. Science-based adaptation options include the use of managed wildfire, prescribed burning, and coupled mechanical thinning and prescribed burning as is consistent with land management allocations and forest conditions. Although some current models of fire management in wNA are averse to short-term risks and uncertainties, the long-term environmental, social, and cultural consequences of wildfire management primarily grounded in fire suppression are well documented, highlighting an urgency to invest in intentional forest management and restoration of active fire regimes.

Wavefront aberration function in terms of R. V. Shack's vector product and Zernike polynomial vectors.

Previous papers have shown how, for rotationally symmetric optical imaging systems, nodes in the field dependence of the wavefront aberration function develop when a rotationally symmetric optical surface within an imaging optical system is decentered and/or tilted. In this paper, we show how Shack's vector product (SVP) can be used to express the wavefront aberration function and to define vectors in terms of the Zernike polynomials. The wavefront aberration function is then expressed in terms of the Zernike vectors. It is further shown that SVP fits within the framework of two-dimensional geometric algebra (GA). Within the GA framework, an equation for the third-order node locations for the binodal astigmatism term that emerge in the presence of tilts and decenters is then demonstrated. A computer model of a three-mirror telescope system is used to demonstrate the validity of the mathematical development.

Brugada syndrome in an active duty Air Force senior pilot.

INTRODUCTION: Brugada syndrome describes a subgroup of patients at risk for polymorphic ventricular tachycardia, ventricular fibrillation, and sudden cardiac death and is likely underdiagnosed among aviators. CASE REPORT: A 40-year-old male pilot presented to the clinic for his physical. He denied any symptoms on initial questioning. Subsequent electrocardiogram (ECG) revealed premature ventricular couplets with ST-segment elevation in V1 and V2 of the precordial leads with T-wave abnormalities. DISCUSSION: Special care must be taken if ECG demonstrates a Brugada pattern-especially in patients with a history of syncope or a family history of sudden death. Recent studies have confirmed a significant risk reduction in symptomatic patients with type 1 Brugada to as low as 0.8% to 3% with an implantable cardioverter defibrillator. CONCLUSION: Symptomatic patients displaying type 1 Brugada ECG (spontaneous or after sodium channel blockade) should receive an implantable cardioverter defibrillator and must be permanently disqualified. The Aeromedical Consultation Service should review all cases of Brugada syndrome and render a return to fly for asymptomatic nondiagnostic Brugada types.

Simple design changes to wires to substantially reduce MRI-induced heating at 1.5 T: implications for implanted leads.

Reductions in MRI-induced heating at 1.5 T resulting from a simple design change to coiled wires were investigated. MRI-induced heating was assessed for two different coiled wire forms (length, 26 cm): (1) multi-filar coiled wire form and (2) multi-filar coiled wire form having a different coiled pitch, providing an air gap spacing between adjacent five-filar coil loops. Each wire had an electrode and was insulated to create a lead, similar to that which would be used for a medical implant. The wire forms were placed in a gelled-saline-filled head/torso phantom and imaged at 1.5 T [whole-body average specific absorption rate (SAR), 1.79 W/kg]. Fluoroptic thermometry probes were used to measure temperatures at the distal ends of the wires. The experiments demonstrated a substantial reduction in MRI-induced heating for the modified wire compared to the unmodified wire (i.e., 10.5 degrees C difference observed in one experiment and 26 degrees C difference in another). These findings have important implications for MRI-induced heating of leads used for medical implants.

An innovative methodology for analyzing digital visibility images in an urban environment.

A novel methodology combining digital imaging, conventional fixed visibility monitors, and solar radiation monitors has been developed to characterize the visual air quality of the El Paso and Ciudad Juarez urban vista. The authors have found that the digital image quality is reproducible and useful for quantitative analysis of visibility conditions. Regions of interest were selected in images along view paths of interest and values for a contrast variable of interest, typically the coefficient of variation or contrast ratio (CR) for discrete targets, were computed. Both of these indices are bounded at 0 and 1 and are scaled to the "clean day" maxima for a given date, time, and selected view paths. This produces a relative visibility index for various view paths. With the siting of a Belfort (6230A) visibility monitor at a central location, it has been possible to initiate contrast analysis of various targets in current and archived camera images obtained near this monitor. For uniformly "clean" days, as indicated by fine particulate matter observations and visual inspection, the authors have been able to use the extinction coefficient (Bext) derived from the 6230A to put the relative visibility index, based on CR, on an absolute basis in terms of an ideal target located at a given distance. This permits the generation of contrast extinction, Bext/C, for each view path that is independent of the actual target intrinsic contrast (within limits) and allows the comparison of Bext/C along different view paths with other air quality indices. Multiple linear regression was used to derive a relationship between the CR-based Bext/C value and air quality parameters. Visibility attenuation because of sulfate particles was found to have the highest correlation with Bext/C. In addition, solar radiation was observed to be a significant predictor of visibility in the urban region.

Can pacemakers, neurostimulators, leads, or guide wires be MRI safe? Technological concerns and possible resolutions.

The substantial benefits of magnetic resonance imaging are often denied to patients known to have implanted medical devices such as pacemakers and neurostimulators. Other patients are put at potential risk when they undergo an MRI procedure, even though specific informed consent is required regarding the possible MRI interactions with the implanted device. The medical community is currently divided over the actual extent of the MRI safety problem. In this report, insight is provided into the wide array of results achieved by many researchers; also, several options for producing medical devices that are inherently safe under worst-case MRI conditions are presented. As the problem is very complex and the variety of implants is large, this paper focuses on the problems of MRI-induced lead heating.