MARGINAL AGRICULTURAL LAND CLASSIFICATION: A NEW APPROACH

Land Economics/Use,

Simulating Star Formation and Feedback in Galactic Disk Models

We use a high-resolution grid-based hydrodynamics method to simulate the multi-phase interstellar medium in a Milky Way-size quiescent disk galaxy. The models are global and three-dimensional, and include a treatment of star formation and feedback. We examine the formation of gravitational instabilities and show that a form of the Toomre instability criterion can successfully predict where star formation will occur. Two common prescriptions for star formation are investigated. The first is based on cosmological simulations and has a relatively low threshold for star formation, but also enforces a comparatively low efficiency. The second only permits star formation above a number density of 1000 cm^-3 but adopts a high efficiency. We show that both methods can reproduce the observed slope of the relationship between star formation and gas surface density (although at too high a rate for our adopted parameters). A run which includes feedback from type II supernovae is successful at driving gas out of the plane, most of which falls back onto the disk. This feedback also substantially reduces the star formation rate. Finally, we examine the density and pressure distribution of the ISM, and show that there is a rough pressure equilibrium in the disk, but with a wide range of pressures at a given location (and even wider for the case including feedbackComment: 14 pages, 12 figures, accepted to Astrophysical Journa

A re-analysis of the three-year WMAP temperature power spectrum and likelihood

We analyze the three-year WMAP temperature anisotropy data seeking to confirm the power spectrum and likelihoods published by the WMAP team. We apply five independent implementations of four algorithms to the power spectrum estimation and two implementations to the parameter estimation. Our single most important result is that we broadly confirm the WMAP power spectrum and analysis. Still, we do find two small but potentially important discrepancies: On large angular scales there is a small power excess in the WMAP spectrum (5-10% at l<~30) primarily due to likelihood approximation issues between 13 <= l <~30. On small angular scales there is a systematic difference between the V- and W-band spectra (few percent at l>~300). Recently, the latter discrepancy was explained by Huffenberger et al. (2006) in terms of over-subtraction of unresolved point sources. As far as the low-l bias is concerned, most parameters are affected by a few tenths of a sigma. The most important effect is seen in n_s. For the combination of WMAP, Acbar and BOOMERanG, the significance of n_s =/ 1 drops from ~2.7 sigma to ~2.3 sigma when correcting for this bias. We propose a few simple improvements to the low-l WMAP likelihood code, and introduce two important extensions to the Gibbs sampling method that allows for proper sampling of the low signal-to-noise regime. Finally, we make the products from the Gibbs sampling analysis publically available, thereby providing a fast and simple route to the exact likelihood without the need of expensive matrix inversions.Comment: 14 pages, 7 figures. Accepted for publication in ApJ. Numerical results unchanged, but interpretation sharpened: Likelihood approximation issues at l=13-30 far more important than potential foreground issues at l <= 12. Gibbs products (spectrum and sky samples, and "easy-to-use" likelihood module) available from http://www.astro.uio.no/~hke/ under "Research

Estimation of Polarized Power Spectra by Gibbs sampling

Earlier papers introduced a method of accurately estimating the angular cosmic microwave background (CMB) temperature power spectrum based on Gibbs sampling. Here we extend this framework to polarized data. All advantages of the Gibbs sampler still apply, and exact analysis of mega-pixel polarized data sets is thus feasible. These advantages may be even more important for polarization measurements than for temperature measurements. While approximate methods can alias power from the larger E-mode spectrum into the weaker B-mode spectrum, the Gibbs sampler (or equivalently, exact likelihood evaluations) allows for a statistically optimal separation of these modes in terms of power spectra. To demonstrate the method, we analyze two simulated data sets: 1) a hypothetical future CMBPol mission, with the focus on B-mode estimation; and 2) a Planck-like mission, to highlight the computational feasibility of the method.Comment: 8 pages, 5 figures. High-resolution version available from http://www.astro.uio.no/~hke/docs/larson_et_al_2006.ps.gz; accepted for publication in Ap

Tamm Review: Management of mixed-severity fire regime forests in Oregon, Washington, and Northern California

Increasingly, objectives for forests with moderate- or mixed-severity fire regimes are to restore successionally diverse landscapes that are resistant and resilient to current and future stressors. Maintaining native species and characteristic processes requires this successional diversity, but methods to achieve it are poorly explained in the literature. In the Inland Pacific US, large, old, early seral trees were a key historical feature of many young and old forest successional patches, especially where fires frequently occurred. Large, old trees are naturally fire-tolerant, but today are often threatened by dense understory cohorts that create fuel ladders that alter likely post-fire successional pathways. Reducing these understories can contribute to resistance by creating conditions where canopy trees will survive disturbances and climatic stressors; these survivors are important seed sources, soil protectors, and critical habitat elements. Historical timber harvesting has skewed tree size and age class distributions, created hard edges, and altered native patch sizes. Manipulating these altered forests to promote development of larger patches of older, larger, and more widely-spaced trees with diverse understories will increase landscape resistance to severe fires, and enhance wildlife habitat for underrepresented conditions. Closed-canopy, multi-layered patches that develop in hot, dry summer environments are vulnerable to droughts, and they increase landscape vulnerability to insect outbreaks and severe wildfires. These same patches provide habitat for species such as the northern spotted owl, which has benefited from increased habitat area. Regional and local planning will be critical for gauging risks, evaluating trade-offs, and restoring dynamics that can support these and other species. The goal will be to manage for heterogeneous landscapes that include variably-sized patches of (1) young, middle-aged, and old, closed canopy forests growing in upper montane, northerly aspect, and valley bottom settings, (2) a similar diversity of open-canopy, fire-tolerant patches growing on ridgetops, southerly aspects, and lower montane settings, and (3) significant montane chaparral and grassland areas. Tools to achieve this goal include managed wildfire, prescribed burning, and variable density thinning at small to large scales. Specifics on ‘‘how much and where?” will vary according to physiographic, topographic and historical templates, and regulatory requirements, and be determined by means of a socio-ecological process

Tamm Review: Management of mixed-severity fire regime forests in Oregon, Washington, and Northern California

Increasingly, objectives for forests with moderate- or mixed-severity fire regimes are to restore successionally diverse landscapes that are resistant and resilient to current and future stressors. Maintaining native species and characteristic processes requires this successional diversity, but methods to achieve it are poorly explained in the literature. In the Inland Pacific US, large, old, early seral trees were a key historical feature of many young and old forest successional patches, especially where fires frequently occurred. Large, old trees are naturally fire-tolerant, but today are often threatened by dense understory cohorts that create fuel ladders that alter likely post-fire successional pathways. Reducing these understories can contribute to resistance by creating conditions where canopy trees will survive disturbances and climatic stressors; these survivors are important seed sources, soil protectors, and critical habitat elements. Historical timber harvesting has skewed tree size and age class distributions, created hard edges, and altered native patch sizes. Manipulating these altered forests to promote development of larger patches of older, larger, and more widely-spaced trees with diverse understories will increase landscape resistance to severe fires, and enhance wildlife habitat for underrepresented conditions. Closed-canopy, multi-layered patches that develop in hot, dry summer environments are vulnerable to droughts, and they increase landscape vulnerability to insect outbreaks and severe wildfires. These same patches provide habitat for species such as the northern spotted owl, which has benefited from increased habitat area. Regional and local planning will be critical for gauging risks, evaluating trade-offs, and restoring dynamics that can support these and other species. The goal will be to manage for heterogeneous landscapes that include variably-sized patches of (1) young, middle-aged, and old, closed canopy forests growing in upper montane, northerly aspect, and valley bottom settings, (2) a similar diversity of open-canopy, fire-tolerant patches growing on ridgetops, southerly aspects, and lower montane settings, and (3) significant montane chaparral and grassland areas. Tools to achieve this goal include managed wildfire, prescribed burning, and variable density thinning at small to large scales. Specifics on ‘‘how much and where?” will vary according to physiographic, topographic and historical templates, and regulatory requirements, and be determined by means of a socio-ecological process

Cost-effectiveness of cryptococcal antigen screening at CD4 counts of 101-200 cells/µL in Botswana.

Background: Cryptococcal antigen (CrAg) screening in individuals with advanced HIV reduces cryptococcal meningitis (CM) cases and deaths. The World Health Organization recently recommended increasing screening thresholds from CD4 ≤100 cells/µL to ≤200 cells/µL. CrAg screening at CD4 ≤100 cells/µL is cost-effective; however, the cost-effectiveness of screening patients with CD4 101-200 cells/µL requires evaluation. Methods: Using a decision analytic model with Botswana-specific cost and clinical estimates, we evaluated CrAg screening and treatment among individuals with CD4 counts of 101-200 cells/µL. We estimated the number of CM cases and deaths nationally and treatment costs without screening. For screening we modeled the number of CrAg tests performed, number of CrAg-positive patients identified, proportion started on pre-emptive fluconazole, CM cases and deaths. Screening and treatment costs were estimated and cost per death averted or disability-adjusted life year (DALY) saved compared with no screening. Results: Without screening, we estimated 142 CM cases and 85 deaths annually among individuals with CD4 101-200 cells/µL, with treatment costs of $368,982. With CrAg screening, an estimated 33,036 CrAg tests are performed, and 48 deaths avoided (1,017 DALYs saved).  While CrAg screening costs an additional$155,601, overall treatment costs fall by $39,600 (preemptive and hospital-based CM treatment), yielding a net increase of$116,001. Compared to no screening, high coverage of CrAg screening and pre-emptive treatment for CrAg-positive individuals in this population avoids one death for $2440 and$114 per DALY saved. In sensitivity analyses assuming a higher proportion of antiretroviral therapy (ART)-naïve patients (75% versus 15%), cost per death averted was $1472;$69 per DALY saved. Conclusions: CrAg screening for individuals with CD4 101-200 cells/µL was estimated to have a modest impact, involve additional costs, and be less cost-effective than screening populations with CD4 counts ≤100 cells/µL. Additional CrAg screening costs must be considered against other health system priorities

Comparison of Francisella tularensis genomes reveals evolutionary events associated with the emergence of human pathogenic strains

.Sequencing of the non-pathogenic Francisella tularensis sub-species novicida U112, and comparison with two pathogenic sub-species, provides insights into the evolution of pathogenicity in these species

Identification and Molecular Characterization of a New Ovarian Cancer Susceptibility Locus at 17q21.31

Epithelial ovarian cancer (EOC) has a heritable component that remains to be fully characterized. Most identified common susceptibility variants lie in non-protein-coding sequences. We hypothesized that variants in the 3 ′ untranslated region at putative microRNA (miRNA) binding sites represent functional targets that influence EOC susceptibility. Here, we evaluate the association between 767 miRNA binding site single nucleotide polymorphisms (miRSNPs) and EOC risk in 18,174 EOC cases and 26,134 controls from 43 studies genotyped through the Collaborative Oncological Gene-environment Study. We identify several miRSNPs associated with invasive serous EOC risk (OR=1.12, P =10−8 ) mapping to an inversion polymorphism at 17q21.31. Additional genotyping of non-miRSNPs at 17q21.31 reveals stronger signals outside the inversion ( P =10−10 ). Variation at 17q21.31 associates with neurological diseases, and our collaboration is the first to report an association with EOC susceptibility. An integrated molecular analysis in this region provides evidence for ARHGAP27 and PLEKHM1 as candidate EOC susceptibility genes