Managing Economic Risk from Invasive Species: Bug Options

Invasive insect species cause billions of dollars of direct and indirect damage to U.S. crops each year. The market for insuring insect damage is, however, far from complete. The objective of this study is to design and value insect derivatives, or "bug options," which would offer growers a market-based means for transferring risk of pest damage to speculators or others who may profit from higher insect populations. A bug option valuation model is developed and applied to Bemesia tabaci infestation in cotton. The results show that insect derivatives may become important risk management tools for a wide range of growers.Risk and Uncertainty,

Importance of locking plate positioning in proximal humeral fractures as predicted by computer simulations

Multifragmented proximal humeral fractures frequently require operative fixation. The locking plates commonly used are often placed relative to the greater tuberosity, however no quantitative data exists regarding the effect of positional changes. The aim of the study was to establish the effects from variations in proximal‐distal PHILOS humeral plate positioning on predicted fixation failure risk. Twenty‐one left‐sided low‐density virtual humeri models were created with a simulation framework from CT data of elderly donors and osteotomized to mimic an unstable three‐part malreduced AO/OTA 11‐B3.2 fracture with medial comminution. A PHILOS plate with either four or six proximal screws was used for fixation. Both configurations were modelled with plate repositioning 2 and 4 mm distally and proximally to its baseline position. Applying a validated computational model, three physiological loading situations were simulated and fixation failure predicted using average strain around the proximal screws – an outcome established as a surrogate for cycles to failure. Varying the craniocaudal plate position affected the peri‐implant strain for both four and six‐screw configurations. Even though significant changes were seen only in the latter, all tests suggested that more proximal plate positioning results in decreased peri‐screw strains whereas distalizing creates increases in strain. These results suggest that even a small distal PHILOS plate malpositioning may reduce fixation stability. Plate distalization increases the probability of being unable to insert all screws within the humeral head, which dramatically increases the forces acting on the remaining screws. Proximal plate shifting may be beneficial, especially for constructs employing calcar screws.This article is protected by copyright. All rights reserve

Importance of locking plate positioning in proximal humeral fractures as predicted by computer simulations

Multifragmented proximal humeral fractures frequently require operative fixation. The locking plates commonly used are often placed relative to the greater tuberosity, however no quantitative data exists regarding the effect of positional changes. The aim of the study was to establish the effects from variations in proximal‐distal PHILOS humeral plate positioning on predicted fixation failure risk. Twenty‐one left‐sided low‐density virtual humeri models were created with a simulation framework from CT data of elderly donors and osteotomized to mimic an unstable three‐part malreduced AO/OTA 11‐B3.2 fracture with medial comminution. A PHILOS plate with either four or six proximal screws was used for fixation. Both configurations were modelled with plate repositioning 2 and 4 mm distally and proximally to its baseline position. Applying a validated computational model, three physiological loading situations were simulated and fixation failure predicted using average strain around the proximal screws – an outcome established as a surrogate for cycles to failure. Varying the craniocaudal plate position affected the peri‐implant strain for both four and six‐screw configurations. Even though significant changes were seen only in the latter, all tests suggested that more proximal plate positioning results in decreased peri‐screw strains whereas distalizing creates increases in strain. These results suggest that even a small distal PHILOS plate malpositioning may reduce fixation stability. Plate distalization increases the probability of being unable to insert all screws within the humeral head, which dramatically increases the forces acting on the remaining screws. Proximal plate shifting may be beneficial, especially for constructs employing calcar screws.This article is protected by copyright. All rights reserve

Screw configuration in proximal humerus plating has a significant impact on fixation failure risk predicted by finite element models

Background: Proximal humeral fractures occur frequently, with fixed angle locking plates often being used for their treatment. No current quantitative evidence for the effect of different screw configurations exists, and the large number of variations makes biomechanical testing prohibitive. Therefore, we used an established and validated finite element osteosynthesis test kit to quantify the effect of variations in screw configuration on predicted failure risk of PHILOS plate fixation for unstable proximal humerus fractures. Methods: Twenty-six low-density humerus models were osteotomized to create malreduced unstable 3-part fractures that were virtually fixed with PHILOS plates. Twelve screw configurations were simulated: 6 using 2 screw rows, 4 using 3 rows, and 1 with either 8 or 9 screws. Three physiological loading cases were modeled and an established finite element analysis methodology was used. The average peri-screw bone strain, previously demonstrated to predict fatigue cutout failure, was used to compare the different configurations. Results: Significant differences in peri-screw strains, and thus predicted failure risk, were seen with different combinations. The 9-screw configuration demonstrated the lowest peri-screw strains. Fewer screw constructs showed lower strains when placed further apart. The calcar screws (row E) significantly (P &lt; .001) reduced fixation failure risk. Conclusion: Screw configurations significantly impact predicted cutout failure risk for locking plate fixations of unstable proximal humerus fractures in low-density bone. Although requiring clinical corroboration, the result of this study suggests that additional screws reduce peri-screw strains, the distance between them should be maximized whenever possible and the calcar screws should be used.</p

Natural variation in abiotic stress responsive gene expression and local adaptation to climate in Arabidopsis thaliana.

Gene expression varies widely in natural populations, yet the proximate and ultimate causes of this variation are poorly known. Understanding how variation in gene expression affects abiotic stress tolerance, fitness, and adaptation is central to the field of evolutionary genetics. We tested the hypothesis that genes with natural genetic variation in their expression responses to abiotic stress are likely to be involved in local adaptation to climate in Arabidopsis thaliana. Specifically, we compared genes with consistent expression responses to environmental stress (expression stress responsive, "eSR") to genes with genetically variable responses to abiotic stress (expression genotype-by-environment interaction, "eGEI"). We found that on average genes that exhibited eGEI in response to drought or cold had greater polymorphism in promoter regions and stronger associations with climate than those of eSR genes or genomic controls. We also found that transcription factor binding sites known to respond to environmental stressors, especially abscisic acid responsive elements, showed significantly higher polymorphism in drought eGEI genes in comparison to eSR genes. By contrast, eSR genes tended to exhibit relatively greater pairwise haplotype sharing, lower promoter diversity, and fewer nonsynonymous polymorphisms, suggesting purifying selection or selective sweeps. Our results indicate that cis-regulatory evolution and genetic variation in stress responsive gene expression may be important mechanisms of local adaptation to climatic selective gradients

Comparative Ecology of Sarcobatus Baileyi and Sarcobatus Vermiculatus in Eastern California

Greasewood (Sarcobatus) is a succulent-leaved, halophytic shrub of North American origin. The genus comprises 2 species: Sarcobatus baileyi and Sarcobatus vermiculatus. Sarcobatus vermiculatus is common throughout much of western North America, but S. baileyi is much more limited in distribution and was previously thought to be endemic to Nevada. Here we document and describe a S. baileyi population in eastern California, comparing its morphology and ecology to an adjacent S. vermiculatus population. Morphologically, S. baileyi is smaller in stature but produces larger seeds; however, fewer S. baileyi seeds germinated and survived a 20-day laboratory incubation compared to seeds of S. vermiculatus. Sarcobatus baileyi has higher leaf Na concentrations and operates at much lower plant water potentials than S. vermiculatus under field conditions; however, no significant differences were observed between the 2 species in long-term water-use efficiency as measured by leaf delta(13)C. Leaf Na concentrations were very low in both species. Overall, these species differ greatly in a number of traits that are consistent with the upland, nonphreatophytic character of S. baileyi, which is in stark contrast to the phreatophytic character of S. vermiculatus. Both species, however, are very salt tolerant and have low leaf N concentrations, indicating the low nutrient availability and the potentially high salinity of their extreme habitats. Further investigation of comparable desert ridge environments should be conducted to determine the extent of S. baileyi in eastern California, and common garden comparisons of the 2 species should be conducted to compare their ecophysiological traits

A Perspective on Development Flight Instrumentation and Flight Test Analysis Plans for Ares I-X

NASA. s Constellation Program will take a significant step toward completion of the Ares I crew launch vehicle with the flight test of Ares I-X and completion of the Ares I-X post-flight evaluation. The Ares I-X flight test vehicle is an ascent development flight test that will acquire flight data early enough to impact the design and development of the Ares I. As the primary customer for flight data from the Ares I-X mission, Ares I has been the major driver in the definition of the Development Flight Instrumentation (DFI). This paper focuses on the DFI development process and the plans for post-flight evaluation of the resulting data to impact the Ares I design. Efforts for determining the DFI for Ares I-X began in the fall of 2005, and significant effort to refine and implement the Ares I-X DFI has been expended since that time. This paper will present a perspective in the development and implementation of the DFI. Emphasis will be placed on the process by which the list was established and changes were made to that list due to imposed constraints. The paper will also discuss the plans for the analysis of the DFI data following the flight and a summary of flight evaluation tasks to be performed in support of tools and models validation for design and development

Pleiotropy of FRIGIDA enhances the potential for multivariate adaptation.

An evolutionary response to selection requires genetic variation; however, even if it exists, then the genetic details of the variation can constrain adaptation. In the simplest case, unlinked loci and uncorrelated phenotypes respond directly to multivariate selection and permit unrestricted paths to adaptive peaks. By contrast, 'antagonistic' pleiotropic loci may constrain adaptation by affecting variation of many traits and limiting the direction of trait correlations to vectors that are not favoured by selection. However, certain pleiotropic configurations may improve the conditions for adaptive evolution. Here, we present evidence that the Arabidopsis thaliana gene FRI (FRIGIDA) exhibits 'adaptive' pleiotropy, producing trait correlations along an axis that results in two adaptive strategies. Derived, low expression FRI alleles confer a 'drought escape' strategy owing to fast growth, low water use efficiency and early flowering. By contrast, a dehydration avoidance strategy is conferred by the ancestral phenotype of late flowering, slow growth and efficient water use during photosynthesis. The dehydration avoidant phenotype was recovered when genotypes with null FRI alleles were transformed with functional alleles. Our findings indicate that the well-documented effects of FRI on phenology result from differences in physiology, not only a simple developmental switch

The influence of screw length on predicted cut-out failures for proximal humeral fracture fixations predicted by finite element simulations

Background: The aim of this study was to identify the effect of screw length on predictions of fixation failure in three-part proximal humeral fractures using a finite element-based osteosynthesis modelling toolkit. Methods: A mal-reduced unstable three-part AO/OTA 11-B3.2 fracture with medial comminution was simulated in forty-two digitally processed proximal humeri covering a spectrum of bone densities and fixed with the PHILOS plate using three distal and six proximal locking screws. Four test groups were generated based on the screw tip to joint surface distance (TJD), with all proximal screws being shortened from 4 mm TJD to be 8, 12 or 16 mm TJD. Average bone strains around the screw tips, correlating with biomechanical cyclic cut-out-type failure, were evaluated in three physiological loading protocols representing simple shoulder motions. Six further groups were tested, where five of the proximal screws were inserted to 4 mm TJD and the sixth screw to 8 mm TJD. Results: Exponential increases in the predicted risk of fixation failure were seen with increased tip-to-joint distances (p &lt; 0.001). When one of the proximal screws was placed 8 mm from the joint, with the remaining five at 4 mm distance, significant increases (p &lt; 0.001) were registered in the strains around the screw tips in all except the two superior screws. This effect was maximal around the calcar screws (p &lt; 0.001) and for lower density samples (p &lt; 0.001). Conclusions: These results suggest that longer screws provide reduced risk of cut-out failure, i.e. distalisation and/or varisation of the head fragment, and thus may decrease failure rates in proximal humeral fractures treated with angular stable plates. These findings require clinical corroboration and further studies to investigate the risk of screw perforation.</p

Confirmation of co-denitrification in grazed grassland

peer-reviewedPasture-based livestock systems are often associated with losses of reactive forms of nitrogen (N) to the environment. Research has focused on losses to air and water due to the health, economic and environmental impacts of reactive N. Di-nitrogen (N2) emissions are still poorly characterized, both in terms of the processes involved and their magnitude, due to financial and methodological constraints. Relatively few studies have focused on quantifying N2 losses in vivo and fewer still have examined the relative contribution of the different N2 emission processes, particularly in grazed pastures. We used a combination of a high 15N isotopic enrichment of applied N with a high precision of determination of 15N isotopic enrichment by isotope-ratio mass spectrometry to measure N2 emissions in the field. We report that 55.8 g N m−2 (95%, CI 38 to 77 g m−2) was emitted as N2 by the process of co-denitrification in pastoral soils over 123 days following urine deposition (100 g N m−2), compared to only 1.1 g N m−2 (0.4 to 2.8 g m−2) from denitrification. This study provides strong evidence for co-denitrification as a major N2 production pathway, which has significant implications for understanding the N budgets of pastoral ecosystems.The authors are grateful for the funding that was provided through the Research Stimulus Fund Program administered by the Department of Agriculture & Food under the National Development Plan 2007–2013 RSF 07536. The first author is grateful for the funding provided by Teagasc through the Walsh Fellowship Scheme