1,979 research outputs found

    Developing an online environmental landscape certification program

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    Landscape maintenance is a large, rapidly growing, and unregulated small business sector South Carolina (SC). Beyond a pesticides applicators license, no experience or training is currently required in SC. A Lever-Initiative grant was awarded to develop an online Environmental Landscape Certification Program to help landscape professionals meet client expectations and protect SC natural resources. A survey was conducted to identify stakeholder buy-in including content, cost, and preference on learning style. In order to increase adoption by contractors and technicians, specific strategic areas throughout SC were selected to spearhead the program. Stakeholder meetings were held in March to identify barriers to success, fine-tune logistics and develop critical program content. Modules in development give detailed information on pertinent landscaping practices. This certification should help to increase the economic viability of the SC landscape industry while helping to protect natural resources

    Casimir Force between a Dielectric Sphere and a Wall: A Model for Amplification of Vacuum Fluctuations

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    The interaction between a polarizable particle and a reflecting wall is examined. A macroscopic approach is adopted in which the averaged force is computed from the Maxwell stress tensor. The particular case of a perfectly reflecting wall and a sphere with a dielectric function given by the Drude model is examined in detail. It is found that the force can be expressed as the sum of a monotonically decaying function of position and of an oscillatory piece. At large separations, the oscillatory piece is the dominant contribution, and is much larger than the Casimir-Polder interaction that arises in the limit that the sphere is a perfect conductor. It is argued that this enhancement of the force can be interpreted in terms of the frequency spectrum of vacuum fluctuations. In the limit of a perfectly conducting sphere, there are cancellations between different parts of the spectrum which no longer occur as completely in the case of a sphere with frequency dependent polarizability. Estimates of the magnitude of the oscillatory component of the force suggest that it may be large enough to be observable.Comment: 18pp, LaTex, 7 figures, uses epsf. Several minor errors corrected, additional comments added in the final two sections, and references update

    Neurons Responsive to Global Visual Motion Have Unique Tuning Properties in Hummingbirds

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    Neurons in animal visual systems that respond to global optic flow exhibit selectivity for motion direction and/or velocity. The avian lentiformis mesencephali (LM), known in mammals as the nucleus of the optic tract (NOT), is a key nucleus for global motion processing [1–4]. In all animals tested, it has been found that the majority of LM and NOT neurons are tuned to temporo-nasal (back-to-front) motion [4–11]. Moreover, the monocular gain of the optokinetic response is higher in this direction, compared to naso-temporal (front-to-back) motion [12, 13]. Hummingbirds are sensitive to small visual perturbations while hovering, and they drift to compensate for optic flow in all directions [14]. Interestingly, the LM, but not other visual nuclei, is hypertrophied in hummingbirds relative to other birds [15], which suggests enhanced perception of global visual motion. Using extracellular recording techniques, we found that there is a uniform distribution of preferred directions in the LM in Anna’s hummingbirds, whereas zebra finch and pigeon LM populations, as in other tetrapods, show a strong bias toward temporo-nasal motion. Furthermore, LM and NOT neurons are generally classified as tuned to ‘‘fast’’ or ‘‘slow’’ motion [10, 16, 17], and we predicted that most neurons would be tuned to slow visual motion as an adaptation for slow hovering. However, we found the opposite result: most hummingbird LM neurons are tuned to fast pattern velocities, compared to zebra finches and pigeons. Collectively, these results suggest a role in rapid responses during hovering, as well as in velocity control and collision avoidance during forward flight of hummingbirds

    Advanced InSAR atmospheric correction: MERIS/MODIS combination and stacked water vapour models

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    A major source of error for repeat-pass Interferometric Synthetic Aperture Radar (InSAR) is the phase delay in radio signal propagation through the atmosphere (especially the part due to tropospheric water vapour). Based on experience with the Global Positioning System (GPS)/Moderate Resolution Imaging Spectroradiometer (MODIS) integrated model and the Medium Resolution Imaging Spectrometer (MERIS) correction model, two new advanced InSAR water vapour correction models are demonstrated using both MERIS and MODIS data: (1) the MERIS/MODIS combination correction model (MMCC); and (2) the MERIS/MODIS stacked correction model (MMSC). The applications of both the MMCC and MMSC models to ENVISAT Advanced Synthetic Aperture Radar (ASAR) data over the Southern California Integrated GPS Network (SCIGN) region showed a significant reduction in water vapour effects on ASAR interferograms, with the root mean square (RMS) differences between GPS- and InSAR-derived range changes in the line-of-sight (LOS) direction decreasing from ,10mm before correction to ,5mm after correction, which is similar to the GPS/MODIS integrated and MERIS correction models. It is expected that these two advanced water vapour correction models can expand the application of MERIS and MODIS data for InSAR atmospheric correction. A simple but effective approach has been developed to destripe Terra MODIS images contaminated by radiometric calibration errors. Another two limiting factors on the MMCC and MMSC models have also been investigated in this paper: (1) the impact of the time difference between MODIS and SAR data; and (2) the frequency of cloud-free conditions at the global scale

    Lasting organ-level bone mechanoadaptation is unrelated to local strain

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    Bones adapt to mechanical forces according to strict principles predicting straight shape. Most bones are, however, paradoxically curved. To solve this paradox, we used computed tomography–based, four-dimensional imaging methods and computational analysis to monitor acute and chronic whole-bone shape adaptation and remodeling in vivo. We first confirmed that some acute load-induced structural changes are reversible, adhere to the linear strain magnitude regulation of remodeling activities, and are restricted to bone regions in which marked antiresorptive actions are evident. We make the novel observation that loading exerts significant lasting modifications in tibial shape and mass across extensive bone regions, underpinned by (re)modeling independent of local strain magnitude, occurring at sites where the initial response to load is principally osteogenic. This is the first report to demonstrate that bone loading stimulates nonlinear remodeling responses to strain that culminate in greater curvature adjusted for load predictability without sacrificing strength

    Upper bounds on the first eigenvalue for a diffusion operator via Bakry-\'{E}mery Ricci curvature II

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    Let L=Δ−∇φ⋅∇L=\Delta-\nabla\varphi\cdot\nabla be a symmetric diffusion operator with an invariant measure dμ=e−φdxd\mu=e^{-\varphi}dx on a complete Riemannian manifold. In this paper we prove Li-Yau gradient estimates for weighted elliptic equations on the complete manifold with ∣∇φ∣≤θ|\nabla \varphi|\leq\theta and ∞\infty-dimensional Bakry-\'{E}mery Ricci curvature bounded below by some negative constant. Based on this, we give an upper bound on the first eigenvalue of the diffusion operator LL on this kind manifold, and thereby generalize a Cheng's result on the Laplacian case (Math. Z., 143 (1975) 289-297).Comment: Final version. The original proof of Theorem 2.1 using Li-Yau gradient estimate method has been moved to the appendix. The new proof is simple and direc

    Who I Am: The Meaning of Early Adolescents’ Most Valued Activities and Relationships, and Implications for Self-Concept Research

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    Self-concept research in early adolescence typically measures young people’s self-perceptions of competence in specific, adult-defined domains. However, studies have rarely explored young people’s own views of valued self-concept factors and their meanings. For two major self domains, the active and the social self, this mixed-methods study identified factors valued most by 526 young people from socioeconomically diverse backgrounds in Ireland (10-12 years), and explored the meanings associated with these in a stratified subsample (n = 99). Findings indicate that self-concept scales for early adolescence omit active and social self factors and meanings valued by young people, raising questions about content validity of scales in these domains. Findings also suggest scales may under-represent girls’ active and social selves; focus too much on some school-based competencies; and, in omitting intrinsically salient self domains and meanings, may focus more on contingent (extrinsic) rather than true (intrinsic) self-esteem

    Improving biodiesel yield of animal waste fats by combination of a pre-treatment technique and microwave technology Renewable Energy

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    Recently, due to its low cost there has been increased attention on Animal Waste Fats (AWFs) as a feedstock for biodiesel production. Advanced microwave technology has also been reported by many researchers to enhance the transesterification in biodiesel production. However, esterification of free fatty acids in the feedstock reported here has not attracted so much attention. AWFs come with its challenges namely, high free fatty acid (FFA) content and high water content. This study utilizes AWFs (tallow) containing very large amount of FFA; (25wt.%, 18 wt.%, and 9.4 wt.% FFA/AWFs) as feedstock for fatty acid methyl ester (FAME) production. A simple thermal pre-treatment technique followed microwave assisted esterification with methanol (MeOH) was conducted in a batch process to reduce the FFA content to as low as 1wt.% FFA, which is then suitable for the alkaline transesterification process. The pre-treatment of AWFs at 88°C to first reduce water and decrease viscosity, followed by an operating microwave power of 70W producing a power density 1.147mW/m3, achieved a 15% increase in reduction of FFA over 30W microwave power and conventional thermal method. Under optimum conditions, using 2.0 wt.wt% sulphuric acid catalyst/AWFs and 1:6 molar ratio AWF/MeOH, the FFA conversion of 93wt. % was achieved. The results indicated that the pre-treatment and microwave application provided a faster route to high FFA reduction of AWFs during esterification process. The proposed technology is promising for the potential scale up industrial application
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