729 research outputs found

    Development of an annoyance model based upon elementary auditory sensations for steady-state aircraft interior noise containing tonal components

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    The purpose of this investigation was to develop a noise annoyance model, superior to those already in use, for evaluating passenger response to sounds containing tonal components which may be heard within current and future commercial aircraft. The sound spectra investigated ranged from those being experienced by passengers on board turbofan powered aircraft now in service to those cabin noise spectra passengers may experience within advanced propeller-driven aircraft of the future. A total of 240 sounds were tested in this experiment. Sixty-six of these 240 sounds were steady state, while the other 174 varied temporally due to tonal beating. Here, the entire experiment is described, but the analysis is limited to those responses elicited by the 66 steady-state sounds

    MetaIPM: Placing Integral Projection Models Into a Metapopulation Framework

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    1. Metapopulation models include spatial population dynamics such as dispersion and migration between subpopulations. Integral projection models (IPMs) can include demographic rates as a function of size. Traditionally, metapopulation models do not included detailed populaiton models such as IPMs. In some situations, both local population dynamics (e.g. size-based survival) and spatial dynamics are important. 2. We present a Python package, MetaIPM, which places IPMs into a metapopulation framework, and allow users to readily construct and apply these models that combine local population dynamics within a metapopulation framework. 3. MetaIPM includes an IPM for each subpopulation that is connected to other subpopulations via a metapopulation movement model. These movements can include dispersion, migration or other patterns. The IPM can include for size-specific demographic rates (e.g. survival, recruitment) as well as management actions, such as length-based harvest (e.g. gear specific capture sizes, varying slot limits across political boundaries). The model also allows for changes in metapopulation connectivity between locations, such as a fish passage ladders to enhance movement or deterrents to reduce movement. Thus, resource managers can use MetaIPM to compare different management actions such as the harvest gear type (which can be length-specific) and harvest locations. 4. We demonstrate how MetaIPM may be applied to inform managers seeking to limit the spread of an invasive species in a system with important metapopulation dynamics. Specifically, we compared removal lengths (all length fish versus longer fish only) for an invasive fish population in a fragmented, inland river system. MetaIPM allowed users to compare the importance of harvesting source populations away from the invasion front, as well as species at the invasion front. The model would also allow for future comparisons of different deterrent placement locations in the system. 5. Moving beyond our example system, we describe how MetaIPM can be applied to other species, systems and management approaches. The MetaIPM packages includes Jupyter Notebooks documenting the package as well as a second set of JupyterNotebooks showing the application of the package to our example system

    Status review of Belding's Yellowthroat Geothlypis beldingi, and implications for its conservation

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    Summary Belding's Yellowthroat (Geothlypis beldingi) inhabits freshwater marshes the length of the state of Baja California Sur. A gap in occurrence from approximately 25u509N to 24u509N separates the subspecies goldmani to the north from beldingi to the south. According to BirdLife International's (2000International's ( , 2007 population estimates, the most important sites for the species are San Ignacio (537-648 birds) and La Purísima (203-450) in the north and San José del Cabo (219-480) and Punta San Pedro (70) in the south. Half of 12 presumed breeding sites in the north and five of 14 in the south were discovered within the last ten years. The species apparently no longer occurs at one historical site in the south. Since 2000, two records from Guerrero Negro and one from Bahía Tortugas approximately 140 km and . 200 km respectively northwest of the known breeding range demonstrate the species' dispersal ability. Belding's Yellowthroat is of utmost conservation concern, but the most recent conservation summaries exaggerated the species' plight, in particular by under-appreciating the bird's capacity for long-range dispersal and the ability of marsh habitat to regenerate quickly. Formal studies of the species should be undertaken and marsh creation should be incorporated in the state's development plans

    Analysis of Per Capita Contributions from a Spatial Model Provides Strategies for Controlling Spread of Invasive Carp

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    Metapopulation models may be applied to inform natural resource management to guide actions targeted at location-specific subpopulations. Model insights frequently help to understand which subpopulations to target and highlight the importance of connections among subpopulations. For example, managers often treat aquatic invasive species populations as discrete populations due to hydrological (e.g., lakes, pools formed by dams) or jurisdictional boundaries (e.g., river segments by country or jurisdictional units such as states or provinces). However, aquatic invasive species often have high rates of dispersion and migration among heterogenous locations, which complicates traditional metapopulation models and may not conform to management boundaries. Controlling invasive species requires consideration of spatial dynamics because local management activities (e.g., harvest, movement deterrents) may have important impacts on connected subpopulations. We expand upon previous work to create a spatial linear matrix model for an aquatic invasive species, Bighead Carp, in the Illinois River, USA, to examine the per capita contributions of specific subpopulations and impacts of different management scenarios on these subpopulations. Managers currently seek to prevent Bighead Carp from invading the Great Lakes via a connection between the Illinois Waterway and Lake Michigan by allocating management actions across a series of river pools. We applied the model to highlight how spatial variation in movement rates and recruitment can affect decisions about where management activities might occur. We found that where the model suggested management actions should occur depend crucially on the specific management goal (i.e., limiting the growth rate of the metapopulation vs. limiting the growth rate of the invasion front) and the per capita recruitment rate in downstream pools. Our findings illustrate the importance of linking metapopulation dynamics to management goals for invasive species control

    Effect of Calving Season and Wintering System on Cow Performance

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    Four years of data from three different calving seasons and two different cow wintering systems were evaluated utilizing 218 cows/year. Cows calved in spring, summer, or fall and were wintered on native Sandhills range or cornstalks. Calving season affected cow body weight (BW) and body condition score (BCS) throughout the production year; calving in the fall reduced number of calves weaned per cow. No differences were observed between cows wintered on Sandhills range and those wintered on cornstalks

    Multi-ingredient pre-workout supplements, safety implications, and performance outcomes: a brief review

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    In recent years, a new class of dietary supplements called multi-ingredient pre-workout supplements (MIPS) has increased in popularity. These supplements are intended to be taken prior to exercise and typically contain a blend of ingredients such as caffeine, creatine, beta-alanine, amino acids, and nitric oxide agents, the combination of which may elicit a synergistic effect on acute exercise performance and subsequent training adaptations compared to single ingredients alone. Therefore, the purpose of this article was to review the theoretical rationale and available scientific evidence assessing the potential ergogenic value of acute and chronic ingestion of MIPS, to address potential safety concerns surrounding MIPS supplementation, and to highlight potential areas for future research. Though direct comparisons between formulations of MIPS or between a MIPS and a single ingredient are challenging and often impossible due to the widespread use of “proprietary blends” that do not disclose specific amounts of ingredients in a given formulation, a substantial body of evidence suggests that the acute pre-exercise consumption of MIPS may positively influence muscular endurance and subjective mood, though mixed results have been reported regarding the acute effect of MIPS on force and power production. The chronic consumption of MIPS in conjunction with a periodized resistance training program appears to augment beneficial changes in body composition through increased lean mass accretion. However, the impact of long-term MIPS supplementation on force production, muscular endurance, aerobic performance, and subjective measures is less clear. MIPS ingestion appears to be relatively safe, though most studies that have assessed the safety of MIPS are relatively short (less than eight weeks) and thus more information is needed regarding the safety of long-term supplementation. As with any dietary supplement, the use of MIPS carries implications for the athlete, as many formulations may intentionally contain banned substances as ingredients or unintentionally as contaminants. We suggest that athletes thoroughly investigate the ingredients present in a given MIPS prior to consumption. In conclusion, it appears that multi-ingredient pre-workout supplements have promise as an ergogenic aid for active individuals, though further information is required regarding long-term efficacy and safety in a wider variety of populations

    Safety of Creatine Supplementation in Active Adolescents and Youth: A Brief Review

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    Creatine has been extensively researched and is well-supported as one of the most effective dietary supplements available. There is overwhelming support within the literature regarding the ability of creatine to augment performance following short term (5–7 days) and long-duration supplementation periods. There is also strong support for creatine regarding its safety profile and minimal risk for adverse events or any negative influence on markers of clinical health and safety. Recent research has also highlighted the ability of creatine to confer several health-related benefits in select clinical populations in addition to offering cognitive benefits. Creatine is also a popular supplement of choice for adolescent athletes; however, research in this area is extremely limited, particularly when examining the safety and efficacy of creatine supplementation in this population. Therefore, the purpose of this review was to highlight the limited number of studies available in adolescent populations and systematically discuss the topic of safety of creatine supplementation in a younger population

    Case Study: Producer concerns and perceptions regarding the effect of methane on cattle production and the environment: A survey of Nebraska producers

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    Enteric methane production from cattle and its effect on climate change has been a topic of debate. Multiple studies have explored methods to reduce cattle enteric methane production while simultaneously improving performance. However, most strategies developed have not been widely implemented by cattle producers. Knowledge of producer concerns and perceptions on methane production from cattle and its effect on the environment may be limited. Therefore, the objectives of this survey were to determine what Nebraska producers know about methane production by cattle and how it affects performance and to determine whether different age groups, regions of Nebraska, and production size and type affects producer opinions on enteric methane production and climate change. The survey had a response rate of 22%. Regarding climate change, approximately 39% of producers disagreed, 33% were neutral, and 28% agreed they were concerned. However, producers in central and eastern Nebraska were closer to neutral than producers in western Nebraska (P \u3c 0.05). Younger producers perceived cattle to have a more positive effect on the environment and reported that they were more likely to adopt new management techniques that have been shown to improve animal performance than older producers (P \u3c 0.05). Most producers reported receiving production-related information from veterinarians (47.6%), followed by the “other” category (34.9%), the University of Nebraska (15.6%), and state and federal governments, which were the lowest (1.4 and 0.6%, respectively). In the last 3 yr, approximately 57% of producers attended one or fewer extension meetings, but 37% had not attended any extension meetings
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