1,322 research outputs found
Fundamental investigation of losses of skeletal mineral in young adult human males and collaterally in young adult male pigtail monkeys /macacus nemestrima/ through immobilization for varying periods of time, coupled with a study of methods of preven
Skeletal mineral losses in young adult humans and monkeys resulting from immobilizatio
Effects of patent privateering on settlements and R&D under sequential market entry
We investigate patent litigation, settlements and R&D incentives on a market where two firms develop technologies in order to obtain patents and produce goods. Firms may sell IP rights to a Patent Assertion Entity (PAE) that acts as intermediary for patent monetization. We find that compared to simultaneous market entry, the effect of this so-called patent privateering is mitigated if firms enter sequentially. Furthermore, we show that privateering may decrease industry profits by distortion of R&D incentives even when there is no rent extraction by the PAE
The Viscous Nonlinear Dynamics of Twist and Writhe
Exploiting the "natural" frame of space curves, we formulate an intrinsic
dynamics of twisted elastic filaments in viscous fluids. A pair of coupled
nonlinear equations describing the temporal evolution of the filament's complex
curvature and twist density embodies the dynamic interplay of twist and writhe.
These are used to illustrate a novel nonlinear phenomenon: ``geometric
untwisting" of open filaments, whereby twisting strains relax through a
transient writhing instability without performing axial rotation. This may
explain certain experimentally observed motions of fibers of the bacterium B.
subtilis [N.H. Mendelson, et al., J. Bacteriol. 177, 7060 (1995)].Comment: 9 pages, 4 figure
Detection, isolation, and analysis of a released Bordetella pertussis product toxic to cultured tracheal cells.
Cultured hamster trachea epithelial cells were selected as an in vitro model system to study Bordetella pertussis in the respiratory tract. DNA synthesis by serum-stimulated tracheal cells, in contrast to other cell types tested, was inhibited by the supernatant from log-phase B. pertussis broth cultures. A sensitive microassay with these tracheal cells permitted the development of a chromatographic purification scheme based on aggregation of the biological activity under salt-free conditions. The active fraction from this first stage of purification caused a dose-dependent inhibition of DNA synthesis without a similar effect on RNA or protein synthesis. Organ cultures of hamster tracheal rings, when exposed to this partially purified fraction, developed epithelial cytopathology comparable to that seen during B. pertussis infection. Ciliary activity showed and eventually ceased as ciliated cells were extruded from the ring, leaving an intact but mostly nonciliated epithelium. Further purification of this biological activity was achieved with preparative-scale high-voltage paper electrophoresis. Based on ninhydrin staining and the radioactive profile of material purified from radiolabeled B. pertussis cultures, four fractions were eluted from the paper by descending chromatography. Only component B caused a dose-dependent inhibition of cultured tracheal cell DNA synthesis and epithelial cytopathology in tracheal rings. Combination experiments also demonstrated enhanced inhibition by component B in the presence of component G (oxidized glutathione), a copurifying molecule from the growth medium. Amino acid analysis (five residues), glycine (two residues), cysteine (two residues), and diaminopimelic acid (one residue), as well as muramic acid and glucosamine
Phagocyte-derived lactate stimulates oxygen consumption by Neisseria gonorrhoeae. An unrecognized aspect of the oxygen metabolism of phagocytosis.
L'acide lactique extra-cellulaire, libéré par suite de la glycolyse des neutrophiles, augmente le transfert des électrons et la consommation d'O2par les gonocoques. On discute les implications possibles de cette observation pour la pathogénie bactérienne
O18O and C18O observations of rho Oph A
Observations of the (N_J=1_1-1_0) ground state transition of O_2 with the
Odin satellite resulted in a about 5 sigma detection toward the dense core rho
Oph A. At the frequency of the line, 119 GHz, the Odin telescope has a beam
width of 10', larger than the size of the dense core, so that the precise
nature of the emitting source and its exact location and extent are unknown.
The current investigation is intended to remedy this. Telluric absorption makes
ground based O_2 observations essentially impossible and observations had to be
done from space. mm-wave telescopes on space platforms were necessarily small,
which resulted in large, several arcminutes wide, beam patterns. Although the
Earth's atmosphere is entirely opaque to low-lying O_2 transitions, it allows
ground based observations of the much rarer O18O in favourable conditions and
at much higher angular resolution with larger telescopes. In addition, rho Oph
A exhibits both multiple radial velocity systems and considerable velocity
gradients. Extensive mapping of the region in the proxy C18O (J=3-2) line can
be expected to help identify the O_2 source on the basis of its line shape and
Doppler velocity. Line opacities were determined from observations of optically
thin 13C18O (J=3-2) at selected positions. During several observing periods,
two C18O intensity maxima in rho Oph A were searched for in the 16O18O
(2_1-0_1) line at 234 GHz with the 12m APEX telescope. Our observations
resulted in an upper limit on the integrated O18O intensity of < 0.01 K km/s (3
sigma) into the 26.5" beam. We conclude that the source of observed O_2
emission is most likely confined to the central regions of the rho Oph A cloud.
In this limited area, implied O_2 abundances could thus be higher than
previously reported, by up to two orders of magnitude.Comment: 7 pages, 6 figures (5 colour), Astronomy & Astrophysic
Evidence for a singularity in ideal magnetohydrodynamics: implications for fast reconnection
Numerical evidence for a finite-time singularity in ideal 3D
magnetohydrodynamics (MHD) is presented. The simulations start from two
interlocking magnetic flux rings with no initial velocity. The magnetic
curvature force causes the flux rings to shrink until they come into contact.
This produces a current sheet between them. In the ideal compressible
calculations, the evidence for a singularity in a finite time is that the
peak current density behaves like for a range of
sound speeds (or plasma betas). For the incompressible calculations consistency
with the compressible calculations is noted and evidence is presented that
there is convergence to a self-similar state. In the resistive reconnection
calculations the magnetic helicity is nearly conserved and energy is
dissipated.Comment: 4 pages, 4 figure
The multicovering radius problem for some types of discrete structures
The covering radius problem is a question in coding theory concerned with
finding the minimum radius such that, given a code that is a subset of an
underlying metric space, balls of radius over its code words cover the
entire metric space. Klapper introduced a code parameter, called the
multicovering radius, which is a generalization of the covering radius. In this
paper, we introduce an analogue of the multicovering radius for permutation
codes (cf. Keevash and Ku, 2006) and for codes of perfect matchings (cf. Aw and
Ku, 2012). We apply probabilistic tools to give some lower bounds on the
multicovering radii of these codes. In the process of obtaining these results,
we also correct an error in the proof of the lower bound of the covering radius
that appeared in Keevash and Ku (2006). We conclude with a discussion of the
multicovering radius problem in an even more general context, which offers room
for further research.Comment: To appear in Designs, Codes and Cryptography (2012
TIMASSS: The IRAS16293-2422 Millimeter And Submillimeter Spectral Survey. I. Observations, calibration and analysis of the line kinematics
While unbiased surveys observable from ground-based telescopes have
previously been obtained towards several high mass protostars, very little
exists on low mass protostars. To fill up this gap, we carried out a complete
spectral survey of the bands at 3, 2, 1 and 0.8 mm towards the solar type
protostar IRAS16293-2422. The observations covered about 200\,GHz and were
obtained with the IRAM-30m and JCMT-15m telescopes. Particular attention was
devoted to the inter-calibration of the obtained spectra with previous
observations. All the lines detected with more than 3 sigma and free from
obvious blending effects were fitted with Gaussians to estimate their basic
kinematic properties. More than 4000 lines were detected (with sigma \geq 3)
and identified, yielding a line density of approximatively 20 lines per GHz,
comparable to previous surveys in massive hot cores. The vast majority (~2/3)
of the lines are weak and due to complex organic molecules. The analysis of the
profiles of more than 1000 lines belonging 70 species firmly establishes the
presence of two distinct velocity components, associated with the two objects,
A and B, forming the IRAS16293-2422 binary system. In the source A, the line
widths of several species increase with the upper level energy of the
transition, a behavior compatible with gas infalling towards a ~1 Mo object.
The source B, which does not show this effect, might have a much lower central
mass of ~0.1 Mo. The difference in the rest velocities of both objects is
consistent with the hypothesis that the source B rotates around the source A.
This spectral survey, although obtained with single-dish telescope with a low
spatial resolution, allows to separate the emission from 2 different
components, thanks to the large number of lines detected. The data of the
survey are public and can be retrieved on the web site
http://www-laog.obs.ujf-grenoble.fr/heberges/timasss.Comment: 41 pages (26 pages of online Tables), 7 Tables and 6 Figure
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