40,781 research outputs found
Response of Saddled Prominent (Lepidoptera: Notodontidae) Pupae to Desiccation, Cold Treatment, and Post-Cold Treatment Incubation Temperature
Saddled prominent, Heterocampa guttivitta, pupae were placed at 1.5oC for 50 to 200 days, then incubated at one of four post-cold temperatures ranging from 10° to 26.7°C. Adults emerged from pupae exposed to all cold treatment periods. A few adults also emerged from pupae that were not exposed to cold. The time required for adult emergence following cold treatment declined with longer periods of cold treatment and higher post-cold incubation temperature. The interaction between these two main effects was also significant. Adult morphogenesis begins immediately after pupation, and continues until interrupted by cold temperature. When pupae were subjected to desiccating conditions prior to cold treatment, weight loss due to desiccation was accompanied by increased mortality. Desiccation occurred faster at IS.6° than at 18.0°C. Our results identify a physical factor which might contribute to pupal overwintering mortality: prolonged excessive drought conditions between time of pupation and the onset of cold
Assessing Friction Characteristics of Liquid Lubricants
The decline of fossil fuel reserves and the increasing awareness of greenhouse gas emissions have been the primary driving forces behind the need to conserve energy. To improve fuel efficiency friction modifiers are commonly blended into lubricants. Reduction of friction will clearly lead to less energy requirements. However, an accurate evaluation of lubricant performance is not possible using existing test equipment. The main reason is that current test rigs require operating conditions that induce wear so that the measurement of friction in these rigs is not a real evaluation of friction. The paper will detail the design and commissioning of a purpose built test rig to measure frictional characteristics of various oils as well as the results of the tests performed
Performance of transducers with segmented piezoelectric stacks using materials with high electromechanical coupling coefficient
Underwater acoustic transducers often include a stack of thickness polarized
piezoelectric material pieces of alternating polarity interspersed with
electrodes, bonded together and electrically connected in parallel. The stack
is normally much shorter than a quarter wavelength at the fundamental resonance
frequency, so that the mechanical behavior of the transducer is not affected by
the segmentation. When the transducer bandwidth is less than a half octave, as
has conventionally been the case, stack segmentation has no significant effect
on the mechanical behavior of the device. However, when a high coupling
coefficient material such as PMN-PT is used to achieve a wider bandwidth, the
difference between a segmented stack and a similar piezoelectric section with
electrodes only at the two ends can be significant. This paper investigates the
effects of stack segmentation on the performance of wideband underwater
acoustic transducers, particularly tonpilz transducer elements. Included is
discussion of transducer designs using single crystal piezoelectric material
with high coupling coefficient compared with more traditional PZT ceramics.Comment: 26 pages including 14 figures, one table and one appendi
Exploring taboo issues in professional sport through a fictional approach
While the need to consider life course issues in elite sport research and practice is increasingly recognised, some experiences still seem to be considered too dangerous to explore. Consequently, stories of these experiences are silenced and the ethical and moral questions they pose fail to be acknowledged, understood or debated. This paper presents an ethnographic fiction through which we explore a sensitive set of experiences that were uncovered during our research with professional sportspeople. Through a multiâlayered reconstruction, the story reveals the complex, but significant, relationships that exist between identity, cultural narratives and embodied experiences. After the telling we consider how the story has stimulated reflective practice among students, researchers and practitioners. While there are risks involved in writing and sharing taboo stories, the feedback we have received suggests that storytelling can be an effective pedagogical tool in education and professional development
Abundance of Belugas, Delphinapterus leucas, in Cook Inlet, Alaska, 1994â2000
Annual abundance estimates of belugas, Delphinapterus leucas, in Cook Inlet were calculated from counts made by aerial observers and aerial video recordings. Whale group-size estimates were corrected for subsurface whales (availability bias) and whales that were at the surface but were missed (detection bias). Logistic regression was used to estimate the probability that entire groups were missed during the systematic surveys, and the results were used to calculate a correction to account for the whales in these missed groups (1.015, CV = 0.03 in 1994â98; 1.021, CV = 0.01 in 1999â 2000). Calculated abundances were 653 (CV = 0.43) in 1994, 491 (CV = 0.44) in 1995, 594 (CV = 0.28) in 1996, 440 (CV = 0.14) in 1997, 347 (CV = 0.29) in 1998, 367 (CV = 0.14) in 1999, and 435 (CV = 0.23, 95% CI=279â679) in 2000. For management purposes the current Nbest = 435 and Nmin = 360. These estimates replace preliminary estimates of 749 for 1994 and 357 for 1999. Monte Carlo simulations indicate a 47% probability that from June 1994 to June 1998 abundance of the Cook Inlet stock of belugas was depleted by 50%. The decline appears to have stopped in 1998
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