4,802 research outputs found
Using Ecological Niche Modeling and Genetics to Evaluate the Conservation Status of the Texas Gartersnake, Thamnophis Sirtalis Annectens
The definition of a species has been argued extensively by philosophers and biologists resulting in the development of many different concepts which often contradict each other. An integrative approach using multiple types of data (e.g, morphological, ecological, behavioral, genetic) may be the most successful at correctly assigning taxonomic levels.Here, we use an integrative approach of ecological niche modeling and molecular genetics to investigate the taxonomy of a state imperiled gartersnake subspecies, Thamnophis sirtalis annectens, using ecological niche modeling and molecular phylogenetics analyses. Recently, it was given a conservation rank of S2 (imperiled) in the state of Texas and those that are familiar with it have suggested that its numbers are dwindling. Using ecological niche modeling and mtDNA sequence data we begin to understand the natural and evolutionary history of T. s. annectens. The results of this study provided additional information on the ecology and potential habitat range of T. s. annectens as well as information on the phylogenetic systematics of this subspecies. Our ecological niche model indicates areas where conservation efforts for T. s. annectens should be focused as well as important environmental variable such as landcover and geology that T. s. annectens prefers. When including T. s. annectens in a comparative niche model, this subspecies primarily occupies distinctly different habitat than the red-sided gartersnake, T. s. parietalis, which also occurs in Texas. Statistical analysis indicated that T. s. annectens occupies as significantly different ecological niche than T. s. parietalis. Similarly, the genetic data indicate that T. s. annectens can be differentiated from T. s. parietalis and T. s. sirtalis, however this difference is greatest between T. s. sirtalis. While this work has told us much about T. s. annectens, more is left to be learned including ground-truthing our ecological niche model. Collecting additional genetic data to verify the phylogenetic relationships we have hypothesized here should also be done in the future. Regardless, this work indicates T. s. annectens may be distinct both genetically and ecologically and provides conservation managers with niche models that will assist in locating the optimal habitat required by this subspecies
The 1996 Federal Agriculture Improvement and Reform Act: Correcting a Distortion?
This study makes use of farm-level data from the Agricultural Census to evaluate the effects of the 1996 Federal Agriculture Improvement and Reform (FAIR) Act, which intended to "decouple" commodity payments from production decisions. Prior to this Act, agricultural support payments were linked to production decisions via prices and a complex set of restrictions that acted to control the supply of agricultural commodities. We compare farm-level 1992-to-1997 changes in commodity crop plantings of farms that participated in government programs with farms that did not participate. We find that the growth rate of program-crop acreage of non-participants was 19 percentage points below that of participants. This estimated difference remains unchanged after we account for unobserved effects relating to farm size, type, location, and interactions of these factors using over 1900 fixed-effects variables. These results may imply that program participation rules associated with pre-1996 programs effectively acted to limit program acreage in 1992. An alternative explanation is that payments associated with decoupled programs instituted with the 1996 Act were in fact distortionary and induced farmers to produce more than they would have without the payments. Additional research would be needed to test these competing theories.Agricultural and Food Policy,
Expression of the inhibitory receptor NKG2A correlates with increased liver and splenic NK cell response to activating receptor engagement
Rotorcraft handling-qualities design criteria development
Joint NASA/Army efforts at the Ames Research Center to develop rotorcraft handling-qualities design criteria began in earnest in 1975. Notable results were the UH-1H VSTOLAND variable stability helicopter, the VFA-2 camera-and-terrain-board simulator visual system, and the generic helicopter real-time mathematical model, ARMCOP. An initial series of handling-qualities studies was conducted to assess the effects of rotor design parameters, interaxis coupling, and various levels of stability and control augmentation. The ability to conduct in-flight handling-qualities research was enhanced by the development of the NASA/Army CH-47 variable-stability helicopter. Research programs conducted using this vehicle include vertical-response investigations, hover augmentation systems, and the effects of control-force characteristics. The handling-qualities data base was judged to be sufficient to allow an update of the military helicopter handling-qualities specification, MIL-H-8501. These efforts, including not only the in-house experimental work but also contracted research and collaborative programs performed under the auspices of various international agreements. The report concludes by reviewing the topics that are currently most in need of work, and the plans for addressing these topics
Cancer incidence in British vegetarians
Background:
Few prospective studies have examined cancer incidence among vegetarians.
Methods:
We studied 61 566 British men and women, comprising 32 403 meat eaters, 8562 non-meat eaters who did eat fish ('fish eaters') and 20 601 vegetarians. After an average follow-up of 12.2 years, there were 3350 incident cancers of which 2204 were among meat eaters, 317 among fish eaters and 829 among vegetarians. Relative risks (RRs) were estimated by Cox regression, stratified by sex and recruitment protocol and adjusted for age, smoking, alcohol, body mass index, physical activity level and, for women only, parity and oral contraceptive use.
Results:
There was significant heterogeneity in cancer risk between groups for the following four cancer sites: stomach cancer, RRs (compared with meat eaters) of 0.29 (95% CI: 0.07–1.20) in fish eaters and 0.36 (0.16–0.78) in vegetarians, P for heterogeneity=0.007; ovarian cancer, RRs of 0.37 (0.18–0.77) in fish eaters and 0.69 (0.45–1.07) in vegetarians, P for heterogeneity=0.007; bladder cancer, RRs of 0.81 (0.36–1.81) in fish eaters and 0.47 (0.25–0.89) in vegetarians, P for heterogeneity=0.05; and cancers of the lymphatic and haematopoietic tissues, RRs of 0.85 (0.56–1.29) in fish eaters and 0.55 (0.39–0.78) in vegetarians, P for heterogeneity=0.002. The RRs for all malignant neoplasms were 0.82 (0.73–0.93) in fish eaters and 0.88 (0.81–0.96) in vegetarians (P for heterogeneity=0.001).
Conclusion:
The incidence of some cancers may be lower in fish eaters and vegetarians than in meat eaters
How Smokers Became Outlaws: An Application Of The Stakeholder Salience Model To A Social Problem
Smoking bans have gone from being essentially non-existent to being the norm over the course of the last 50 years. When some of these authors started teaching, it was the norm to smoke in the classroom, in hospitals, on airplanes, in prison and in the office. Times have changed—smoking is no longer allowed in these locations in the United States. In this paper, an overview of the history of smoking advocacy, the impacts of smoke-free legislation on different stakeholders, and changes in public perceptions of smoking are provided. Mitchell and Agle’s 1997 Stakeholder Salience Model are used to illustrate the changes over time in stakeholder status for both smokers and nonsmokers. The Mitchell Model could have been useful to predict the change in status that the two stakeholder groups experienced and the authors suggest that management should note the emergence of urgent stakeholders in the future, as they may gain salience in other matters that can impact company wealth. Firms have to be aware of both their customers’ needs (smokers) as well as other social movements that may affect the use of their product, such as nonsmoking legislation. This is the first paper to apply stakeholder salience, including the concepts of urgency, power, and legitimacy, to the changing fortunes of smokers. It looks at how smoking and smokers have gone from the norm in U.S. society to outlaw status
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