6,247 research outputs found
Optimal Learning in Detection Situations First Semiannual Status Report, Period Ending Jun. 30, 1966
Sensitization learning of humans in acoustical task
Optimal learning in detection situations Semiannual status report
Models for improvement of performance in psychophysical task
Mass loading of the Earth's magnetosphere by micron size lunar ejecta. 1: Ejecta production and orbital dynamics in cislunar space
Particulate matter possessing lunar escape velocity sufficient to enhance the cislunar meteroid flux was investigated. While the interplanetary flux was extensively studied, lunar ejecta created by the impact of this material on the lunar surface is only now being studied. Two recently reported flux models are employed to calculate the total mass impacting the lunar surface due to sporadic meteor flux. There is ample evidence to support the contention that the sporadic interplanetary meteoroid flux enhances the meteroid flux of cislunar space through the creation of micron and submicron lunar ejecta with lunar escape velocity
Mass loading of the Earth's magnetosphere by micron size lunar ejecta. 2: Ejecta dynamics and enhanced lifetimes in the Earth's magnetosphere
Extensive studies were conducted concerning the indivdual mass, temporal and positional distribution of micron and submicron lunar ejecta existing in the Earth-Moon gravitational sphere of influence. Initial results show a direct correlation between the position of the Moon, relative to the Earth, and the percentage of lunar ejecta leaving the Moon and intercepting the magnetosphere of the Earth at the magnetopause surface. It is seen that the Lorentz Force dominates all other forces, thus suggesting that submicron dust particles might possibly be magnetically trapped in the well known radiation zones
Bioactive ceramic-reinforced composites for bone augmentation
Biomaterials have been used to repair the human body for millennia, but it is only since the 1970s that man-made composites have been used. Hydroxyapatite (HA)-reinforced polyethylene (PE) is the first of the ‘second-generation’ biomaterials that have been developed to be bioactive rather than bioinert. The mechanical properties have been characterized using quasi-static, fatigue, creep and fracture toughness testing, and these studies have allowed optimization of the production method. The in vitro and in vivo biological properties have been investigated with a range of filler content and have shown that the presence of sufficient bioactive filler leads to a bioactive composite. Finally, the material has been applied clinically, initially in the orbital floor and later in the middle ear. From this initial combination of HA in PE other bioactive ceramic polymer composites have been developed
Bosonic spectral density of epitaxial thin-film La1.83Sr0.17CuO4 superconductors from infrared conductivity measurements
We use optical spectroscopy to investigate the excitations responsible for
the structure in the optical self-energy of thin epitaxial films of
La1.83Sr0.17CuO4. Using Eliashberg formalism to invert the optical spectra we
extract the electron-boson spectral function and find that at low temperature
it has a two component structure closely matching the spin excitation spectrum
recently measured by magnetic neutron scattering. We contrast the temperature
evolution of the spectral density and the two-peak behavior in La2-xSrxCuO4
with another high temperature superconductor Bi2Sr2CaCu2O8+d. The bosonic
spectral functions of the two materials account for the low Tc of LSCO as
compared to Bi-2212
Simulation of truncated normal variables
We provide in this paper simulation algorithms for one-sided and two-sided
truncated normal distributions. These algorithms are then used to simulate
multivariate normal variables with restricted parameter space for any
covariance structure.Comment: This 1992 paper appeared in 1995 in Statistics and Computing and the
gist of it is contained in Monte Carlo Statistical Methods (2004), but I
receive weekly requests for reprints so here it is
Effect of anisotropy on universal transport in unconventional superconductors
We investigate the universal electronic transport for a mixed
+s-wave superconductor in the presence of an anisotropic
elliptical Fermi surface. Similar to the universal low-temperature transport
predicted in a -wave superconductor with a circular Fermi surface,
anisotropic universal features are found in the low-temperature microwave
conductivity, and thermal conductivity in the anisotropic system. The effects
of anisotropy on the penetration depth, impurity induced suppression, and
the zero-frequency density of states are also considered. While a small amount
of anisotropy can lead to a strong suppression of the effective scattering rate
and hence the density of states at zero frequency, experimental data suggests
that large effects are restored by a negative -component gap admixture.Comment: 8 page
Maternal ethnobotanical knowledge is associated with multiple measures of child health in the Bolivian Amazon
Premi a l'excel·lència investigadora. Àmbit de les Ciències Socials. 2008Culture is a critical determinant of human behavior and health, and the intergenerational transmission of knowledge regarding the use of available plant resources has historically been an essential function of culture. Local ethnobotanical knowledge is important for health and nutrition, particularly in rural low-resource settings, but cultural and economic transitions associated with globalization threaten such knowledge. This prospective study investigates the association between parental ethnobotanical knowledge and child health among the Tsimane', a horticulturalist and foraging society in Amazonian Bolivia. Anthropometric data and capillary blood samples were collected from 330 Tsimane' 2- to 10-year-olds, and mothers and fathers were interviewed to assess ethnobotanical knowledge and skills. Comprehensive measures of parental schooling, acculturation, and economic activities were also collected. Dependent variables included three measures of child health: (i) C-reactive protein, assayed in whole-blood spots as an indicator of immunostimulation; (ii) skinfold thickness, to estimate subcutaneous fat stores necessary to fuel growth and immune function; and (iii) height-for-age, to assess growth stunting. Each child health measure was associated with maternal ethnobotanical knowledge, independent of a wide range of potentially confounding variables. Each standard deviation of maternal ethnobotanical knowledge increased the likelihood of good child health by a factor of >1.5. Like many populations around the world, the Tsimane' are increasingly facing the challenges and opportunities of globalization. These results underscore the importance of local cultural factors to child health and document a potential cost if ethnobotanical knowledge is lost
Electron Energy Loss Spectroscopy of strongly correlated systems in infinite dimensions
We study the electron-energy loss spectra of strongly correlated electronic
systems doped away from half-filling using dynamical mean-field theory
(). The formalism can be used to study the loss spectra in the
optical () limit, where it is simply related to the optical
response, and hence can be computed in an approximation-free way in .
We apply the general formalism to the one-band Hubbard model off , with
inclusion of site-diagonal randomness to simulate effects of doping. The
interplay between the coherence induced plasmon feature and the
incoherence-induced high energy continuum is explained in terms of the
evolution in the local spectral density upon hole doping. Inclusion of static
disorder is shown to result in qualitative changes in the low-energy features,
in particular, to the overdamping of the plasmon feature, resulting in a
completely incoherent response. The calculated EELS lineshapes are compared to
experimentally observed EELS spectra for the normal state of the high-
materials near optimal doping and good qualitative agreement is found.Comment: 5 pages, 3 figures, submitted to J. Phys. - Cond. Mat
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