25,165 research outputs found

    Automated tracking of the Florida manatee (Trichechus manatus)

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    The electronic, physical, biological and environmental factors involved in the automated remote tracking of the Florida manatee (Trichechus manatus) are identified. The current status of the manatee as an endangered species is provided. Brief descriptions of existing tracking and position locating systems are presented to identify the state of the art in these fields. An analysis of energy media is conducted to identify those with the highest probability of success for this application. Logistic questions such as the means of attachment and position of any equipment to be placed on the manatee are also investigated. Power sources and manateeborne electronics encapsulation techniques are studied and the results of a compter generated DF network analysis are summarized

    Fluctuations and the Effective Moduli of an Isotropic, Random Aggregate of Identical, Frictionless Spheres

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    We consider a random aggregate of identical frictionless elastic spheres that has first been subjected to an isotropic compression and then sheared. We assume that the average strain provides a good description of how stress is built up in the initial isotropic compression. However, when calculating the increment in the displacement between a typical pair of contaction particles due to the shearing, we employ force equilibrium for the particles of the pair, assuming that the average strain provides a good approximation for their interactions with their neighbors. The incorporation of these additional degrees of freedom in the displacement of a typical pair relaxes the system, leading to a decrease in the effective moduli of the aggregate. The introduction of simple models for the statistics of the ordinary and conditional averages contributes an additional decrease in moduli. The resulting value of the shear modulus is in far better agreement with that measured in numerical simulations

    Decuplet baryon magnetic moments in a QCD-based quark model beyond quenched approximation

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    We study the decuplet baryon magnetic moments in a QCD-based quark model beyond quenched approximation. Our approach for unquenching the theory is based on the heavy baryon perturbation theory in which the axial couplings for baryon - meson and the meson-meson-photon couplings from the chiral perturbation theory are used together with the QM moment couplings. It also involves the introduction of a form factor characterizing the structure of baryons considered as composite particles. Using the parameters obtained from fitting the octet baryon magnetic moments, we predict the decuplet baryon magnetic moments. The Ω\Omega^- magnetic moment is found to be in good agreement with experiment: μΩ\mu_{\Omega^-} is predicted to be 1.97μN-1.97 \mu_N compared to the experimental result of (-2.02 ±\pm 0.05) μN\mu_N.Comment: 19 pages, 2 figure

    Critical Analysis of Baryon Masses and Sigma-Terms in Heavy Baryon Chiral Perturbation Theory

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    We present an analysis of the octet baryon masses and the πN\pi N and KNKN σ\sigma--terms in the framework of heavy baryon chiral perturbation theory. At next-to-leading order, O(q3){\cal O}(q^3), knowledge of the baryon masses and σπN(0)\sigma_{\pi N}(0) allows to determine the three corresponding finite low--energy constants and to predict the the two KNKN σ\sigma--terms σKN(1,2)(0)\sigma^{(1,2)}_{KN} (0). We also include the spin-3/2 decuplet in the effective theory. The presence of the non--vanishing energy scale due to the octet--decuplet splitting shifts the average octet baryon mass by an infinite amount and leads to infinite renormalizations of the low--energy constants. The first observable effect of the decuplet intermediate states to the baryon masses starts out at order q4q^4. We argue that it is not sufficient to retain only these but no other higher order terms to achieve a consistent description of the three--flavor scalar sector of baryon CHPT. In addition, we critically discuss an SU(2) result which allows to explain the large shift of σπN(2Mπ2)σπN(0)\sigma_{\pi N}(2M_\pi^2) - \sigma_{\pi N}(0) via intermediate Δ(1232)\Delta (1232) states.Comment: 18 pp, TeX, BUTP-93/05 and CRN-93-0

    Medication treatment perceptions, concerns and expectations among depressed individuals with Type I Bipolar Disorder

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    BACKGROUND: Subjective experience of illness affects outcomes among populations with bipolar disorder (BD). This cross-sectional study combined qualitative and quantitative approaches to evaluate perceived treatment effects, concerns and expectations among 90 individuals with BD. METHODS: Adults with type I BD, mean age 36.6 years, 51% women, completed a semi-structured interview that was audio taped, transcribed, coded and analyzed along emergent themes. Quantitative scales measured depressive symptoms (Hamilton Depression Scale/HAMD), psychopathology (Clinical Global Impression/CGI), and insight and treatment attitudes (Insight and Treatment Attitudes Questionnaire/ITAQ). RESULTS: Individuals had moderate depression and psychopathology with good insight into need for treatment. Drug treatment was perceived as beneficial, by “stabilizing” or “balancing” mood (42%, N=38), decreasing anxiety/depressive symptoms (19%, N=17) and improving sleep (10%, N=9). While 39%, (N=35) of individuals denied medication concerns, nearly 29%, (N=26) feared possible long-term effects, particularly diabetes or liver/kidney damage. Media stories and advertisements contributed to medication fears. Hopes and expectations for treatment ranged from those that were symptom or functional status-based, such as desiring mood stabilization and elimination of specific symptoms (23%, N=21), to more global hopes such as “being normal” (20%, N=18) or “cured” (18%, N=16). LIMITATIONS: Limitations include relatively small sample, lack of a comparator, inclusion of only depressed individuals and those willing to discuss their illness experience. CONCLUSIONS: While individuals with BD appreciate the effects of medications, concerns regarding adverse effects and discrepancy between actual and hoped-for outcomes can be substantial. Subjective experience with medications using qualitative and quantitative methods should be explored in order to optimize treatment collaboration and outcomes

    Sand as Maxwell's demon

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    We consider a dilute gas of granular material inside a box, kept in a stationary state by shaking. A wall separates the box into two identical compartments, save for a small hole at some finite height hh. As the gas is cooled, a second order phase transition occurs, in which the particles preferentially occupy one side of the box. We develop a quantitative theory of this clustering phenomenon and find good agreement with numerical simulations

    A comparison of measured and calculated thermal stresses in a hybrid metal matrix composite spar cap element

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    A hybrid spar of titanium with an integrally brazed composite, consisting of an aluminum matrix reinforced with boron-carbide-coated fibers, was heated in an oven and the resulting thermal stresses were measured. Uniform heating of the spar in an oven resulted in thermal stresses arising from the effects of dissimilar materials and anisotropy of the metal matrix composite. Thermal stresses were calculated from a finite element structural model using anisotropic material properties deduced from constituent properties and rules of mixtures. Comparisons of calculated thermal stresses with measured thermal stresses on the spar are presented. It was shown that failure to account for anisotropy in the metal matrix composite elements would result in large errors in correlating measured and calculated thermal stresses. It was concluded that very strong material characterization efforts are required to predict accurate thermal stresses in anisotropic composite structures

    The structure of lightning flashes HF-UHF: 12 September 1975, Atlanta, Georgia

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    Simultaneous measurement of sferics at 3, 30, 139, and 295 MHz were made during thunderstorms. Wideband electronics and an analogue tape recorder continuously recorded the radiation from lightning with about 300 kHz of bandwidth. The data were obtained during the passage of a cold front. Flashing rate, burst rate and the structure of individual flashes were recorded. The record of a typical flash begins with a sudden burst of closely spaced pulses whose temporal structure is typical of the stepped leader, and ends in a large pulse suggestive of a first return stroke. The remainder of the flash consists of a sequence of pulses of varying amplitude separated by quiet periods of the order of milliseconds. The shape of these pulses and the temporal structure suggest that the first few large pulses are return strokes. Other discharges begin with widely spaced discrete pulses and resemble the preceding discharge less the leader and return stroke phase. The radiation exhibits a similar structure, at each of the frequencies monitored
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