12,843 research outputs found
Data users note: Apollo 17 lunar photography
The availability of Apollo 17 pictorial data is announced as an aid to the selection of the photographs for study. Brief descriptions are presented of the Apollo 17 flight, and the photographic equipment used during the flight. The following descriptions are also included: service module photography, command module photography, and lunar surface photography
Predicting wildlife reservoirs and global vulnerability to zoonotic Flaviviruses.
Flaviviruses continue to cause globally relevant epidemics and have emerged or re-emerged in regions that were previously unaffected. Factors determining emergence of flaviviruses and continuing circulation in sylvatic cycles are incompletely understood. Here we identify potential sylvatic reservoirs of flaviviruses and characterize the macro-ecological traits common to known wildlife hosts to predict the risk of sylvatic flavivirus transmission among wildlife and identify regions that could be vulnerable to outbreaks. We evaluate variability in wildlife hosts for zoonotic flaviviruses and find that flaviviruses group together in distinct clusters with similar hosts. Models incorporating ecological and climatic variables as well as life history traits shared by flaviviruses predict new host species with similar host characteristics. The combination of vector distribution data with models for flavivirus hosts allows for prediction of global vulnerability to flaviviruses and provides potential targets for disease surveillance in animals and humans
Recent advances in hepatic transplantation at the University of Pittsburgh.
FK506 undoubtedly improved the survival advantage of hepatic allotransplantation. Hepatic-intestinal and multivisceral transplantation has also become a feasible therapy for patients with combined intestinal and liver failure. With better understanding of the immunologic and metabolic aspects of allo- and xenotransplantation, further clinical attempts to transplant animal organs to humans may be considered with the hope for a better outcome in the very near future
Kramers-Kronig, Bode, and the meaning of zero
The implications of causality, as captured by the Kramers-Kronig relations
between the real and imaginary parts of a linear response function, are
familiar parts of the physics curriculum. In 1937, Bode derived a similar
relation between the magnitude (response gain) and phase. Although the
Kramers-Kronig relations are an equality, Bode's relation is effectively an
inequality. This perhaps-surprising difference is explained using elementary
examples and ultimately traces back to delays in the flow of information within
the system formed by the physical object and measurement apparatus.Comment: 8 pages; American Journal of Physics, to appea
Determining mean first-passage time on a class of treelike regular fractals
Relatively general techniques for computing mean first-passage time (MFPT) of
random walks on networks with a specific property are very useful, since a
universal method for calculating MFPT on general graphs is not available
because of their complexity and diversity. In this paper, we present techniques
for explicitly determining the partial mean first-passage time (PMFPT), i.e.,
the average of MFPTs to a given target averaged over all possible starting
positions, and the entire mean first-passage time (EMFPT), which is the average
of MFPTs over all pairs of nodes on regular treelike fractals. We describe the
processes with a family of regular fractals with treelike structure. The
proposed fractals include the fractal and the Peano basin fractal as their
special cases. We provide a formula for MFPT between two directly connected
nodes in general trees on the basis of which we derive an exact expression for
PMFPT to the central node in the fractals. Moreover, we give a technique for
calculating EMFPT, which is based on the relationship between characteristic
polynomials of the fractals at different generations and avoids the computation
of eigenvalues of the characteristic polynomials. Making use of the proposed
methods, we obtain analytically the closed-form solutions to PMFPT and EMFPT on
the fractals and show how they scale with the number of nodes. In addition, to
exhibit the generality of our methods, we also apply them to the Vicsek
fractals and the iterative scale-free fractal tree and recover the results
previously obtained.Comment: Definitive version published in Physical Review
Brands in international and multi‐platform expansion strategies: economic and management issues
Powerful media branding has historically facilitated successful international expansion on the part of magazine and other content forms including film and TV formats. Multi-platform expansion is now increasingly central to the strategies of media companies and, as this chapter argues, effective use of branding in order to engage audiences effectively and to secure a prominent presence across digital platforms forms a core part of this. Drawing on original research into the experience of UK media companies, this chapter highlights some of the key economic, management and socio-cultural issues raised by the ever-increasing role of brands and branding in the strategies of international and multi-platform expansion that are increasingly common- place across media
Properties of solar polar coronal plumes constrained by Ultraviolet Coronagraph Spectrometer data
We investigate the plasma dynamics (outflow speed and turbulence) inside
polar plumes. We compare line profiles (mainly of \ion{O}{6}) observed by the
UVCS instrument on SOHO at the minimum of solar cycle 22-23 with model
calculations. We consider Maxwellian velocity distributions with different
widths in plume and inter-plume regions. Electron densities are assumed to be
enhanced in plumes and to approach inter-plume values with increasing height.
Different combinations of the outflow and turbulence velocity in the plume
regions are considered. We compute line profiles and total intensities of the
\ion{H}{1} Ly and the \ion{O}{6} doublets. The observed profile shapes
and intensities are reproduced best by a small solar wind speed at low
altitudes in plumes that increases with height to reach ambient inter-plume
values above roughly 3-4 R_\sun combined with a similar variation of the
width of the velocity distribution of the scattering atoms/ions. We also find
that plumes very close to the pole give narrow profiles at heights above 2.5
R_\sun, which are not observed. This suggests a tendency for plumes to be
located away from the pole. We find that the inclusion of plumes in the model
computations provides an improved correspondence with the observations and
confirms previous results showing that published UVCS observations in polar
coronal holes can be roughly reproduced without the need for large temperature
anisotropy. The latitude distributions of plumes and magnetic flux
distributions are studied by analyzing data from different instruments on SOHO
and with SOLIS.Comment: 11 figure
Application of the Nuclear Microprobe to the Imaging of Single Event Upsets in Integrated Circuits
A new form of microscopy has been developed which produces micron-resolution maps of where single event upsets occur during ion irradiation of integrated circuits. Utilizing a nuclear microprobe, this imaging technique can irradiate, in isolation, individual components of an integrated circuit (e.g. transistor drains, gates, feedback resistors) and measure immediately the effect of a high energy ion strike on circuit performance. This detailed circuit characterization technique provides a precision diagnostic with which to evaluate the design of integrated circuits that are to be used in space or other radiation environments
Spectrotemporal modulation provides a unifying framework for auditory cortical asymmetries
The principles underlying functional asymmetries in cortex remain debated. For example, it is accepted that speech is processed bilaterally in auditory cortex, but a left hemisphere dominance emerges when the input is interpreted linguistically. The mechanisms, however, are contested, such as what sound features or processing principles underlie laterality. Recent findings across species (humans, canines and bats) provide converging evidence that spectrotemporal sound features drive asymmetrical responses. Typically, accounts invoke models wherein the hemispheres differ in time-frequency resolution or integration window size. We develop a framework that builds on and unifies prevailing models, using spectrotemporal modulation space. Using signal processing techniques motivated by neural responses, we test this approach, employing behavioural and neurophysiological measures. We show how psychophysical judgements align with spectrotemporal modulations and then characterize the neural sensitivities to temporal and spectral modulations. We demonstrate differential contributions from both hemispheres, with a left lateralization for temporal modulations and a weaker right lateralization for spectral modulations. We argue that representations in the modulation domain provide a more mechanistic basis to account for lateralization in auditory cortex
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