1,527 research outputs found
Summary of DSN (Deep Space Network) reimbursable launch support
The Deep Space Network is providing ground support to space agencies of foreign governments as well as to NASA and other agencies of the Federal government which are involved in space activities. DSN funding for support of missions other than NASA are on either a cooperative or a reimbursable basis. Cooperative funding and support are accomplished in the same manner as NASA sponsored missions. Reimbursable launch funding and support methods are described
Can a microscopic stochastic model explain the emergence of pain cycles in patients?
A stochastic model is here introduced to investigate the molecular mechanisms
which trigger the perception of pain. The action of analgesic drug compounds is
discussed in a dynamical context, where the competition with inactive species
is explicitly accounted for. Finite size effects inevitably perturb the
mean-field dynamics: Oscillations in the amount of bound receptors
spontaneously manifest, driven by the noise which is intrinsic to the system
under scrutiny. These effects are investigated both numerically, via stochastic
simulations and analytically, through a large-size expansion. The claim that
our findings could provide a consistent interpretative framework to explain the
emergence of cyclic behaviors in response to analgesic treatments, is
substantiated.Comment: J. Stat. Mech. (Proceedings UPON2008
Vascular Patterns in Cutaneous Ulcerated Basal Cell Carcinoma: A Retrospective Blinded Study Including Dermoscopy.
Abstract The aim of this retrospective study was to determine the type and prevalence of vascular patterns in the ulcerated and non-ulcerated portions of histologically proven basal cell carcinomas (BCCs) and correlate them with other dermoscopic and clinical features, including the clinically supposed diagnosis. Three authors retrospectively collected 156 clinical and 156 dermoscopic digital images of ulcerated BCCs (histologically confirmed); each image was blindly evaluated by 2 other authors, who did not know the histological diagnosis. Seventeen lesions were completely ulcerated, while 139 lesions presented ulcerated and non-ulcerated portions. Correct clinical diagnosis was associated with the type of lesion, in particular 90.6% of partially ulcerated lesions were correctly diagnosed with clinical-dermoscopic examination, compared with 11.8% of totally ulcerated lesions (χ2 = 64.00, p = 0.000). Presence of arborizing pattern in the ulcerated portion was associated with a correct diagnosis (Fisher's exact test, p = 0.015). Correct diagnosis was also associated with absence of dotted pattern in the non-ulcerated area (χ2 = 16.18, p = 0.000); the absence of hairpin (χ2 = 6.08, p = 0.000) and glomerular patterns were associated with correct diagnosis in the ulcerated areas (χ2 = 18.64, p = 0.000). In case of completely ulcerated BCC the clinician lacks the means to correctly identify the correct nature of the lesion, and is driven towards an incorrect diagnostic conclusion
Antibacterial activity of matrix-bound ovotransferrin
Ovotransferrin immobilized by covalent linkage to Sepharose 4B showed a bacteriostatic effect towards Escherichia coli similar to that of free ovotransferrin. The growth of the bacteria, after exposure to the gel-bound ovotransferrin and its removal, depended on the length of exposure. The results suggest that the antibacterial activity of transferrin is not due simply to the removal of iron from the medium
An IMU and USBL-aided buoy for underwater localization
Autonomous underwater navigation remains, as of today, a challenging task. The
marine environment limits the number of sensors available for precise localization, hence Au-
tonomous Underwater Vehicles (AUVs) usually rely on inertial and velocity sensors to obtain an
estimate of their position either through dead reckoning or by means of more sophisticated
navigation filters (such as Kalman filters and its extensions [1]). On the other hand, acoustic
localization makes possible the determination of a reliable vehicles pose estimate exploiting suit-
able acoustic modems [3]; such estimate can even be integrated within the navigation filter of the
vehicle in order to increase its accuracy. In this paper, the authors discuss the development and
the performance of an Ultra-Short BaseLine (USBL)-aided buoy to improve the localization of
underwater vehicles. At first, the components and the physical realization of the buoy will be
discussed; then, the procedure to compute the position of the target will be analyzed. The
following part of the paper will be focused on the development of a recursive state estimation
algorithm to process the measurements computed by the buoy; specifically, Extended Kalman Filter
[4] has been adopted to deal with the nonlinearities of the sensors housed on the buoy. A
validation of the measurement filtering through experimental tests is also proposed
An IMU and USBL-aided buoy for underwater localization
Autonomous underwater navigation remains, as of today, a challenging task. The
marine environment limits the number of sensors available for precise localization, hence Au-
tonomous Underwater Vehicles (AUVs) usually rely on inertial and velocity sensors to obtain an
estimate of their position either through dead reckoning or by means of more sophisticated
navigation filters (such as Kalman filters and its extensions [1]). On the other hand, acoustic
localization makes possible the determination of a reliable vehicles pose estimate exploiting suit-
able acoustic modems [3]; such estimate can even be integrated within the navigation filter of the
vehicle in order to increase its accuracy. In this paper, the authors discuss the development and
the performance of an Ultra-Short BaseLine (USBL)-aided buoy to improve the localization of
underwater vehicles. At first, the components and the physical realization of the buoy will be
discussed; then, the procedure to compute the position of the target will be analyzed. The
following part of the paper will be focused on the development of a recursive state estimation
algorithm to process the measurements computed by the buoy; specifically, Extended Kalman Filter
[4] has been adopted to deal with the nonlinearities of the sensors housed on the buoy. A
validation of the measurement filtering through experimental tests is also proposed
Stochastic Turing patterns in the Brusselator model
A stochastic version of the Brusselator model is proposed and studied via the
system size expansion. The mean-field equations are derived and shown to yield
to organized Turing patterns within a specific parameters region. When
determining the Turing condition for instability, we pay particular attention
to the role of cross diffusive terms, often neglected in the heuristic
derivation of reaction diffusion schemes. Stochastic fluctuations are shown to
give rise to spatially ordered solutions, sharing the same quantitative
characteristic of the mean-field based Turing scenario, in term of excited
wavelengths. Interestingly, the region of parameter yielding to the stochastic
self-organization is wider than that determined via the conventional Turing
approach, suggesting that the condition for spatial order to appear can be less
stringent than customarily believed.Comment: modified version submitted to Phys Rev. E. 5. 3 Figures (5 panels)
adde
Far-Ultraviolet Color Gradients in Early-Type Galaxies
We discuss far-UV (1500 A) surface photometry and FUV-B color profiles for 8
E/S0 galaxies from images taken with the Ultraviolet Imaging Telescope,
primarily during the Astro-2 mission. In three cases, the FUV radial profiles
are more consistent with an exponential than a de Vaucouleurs function, but
there is no other evidence for the presence of a disk or of young, massive
stars. In all cases except M32 the FUV-B color becomes redder at larger radii.
There is a wide range of internal radial FUV-B color gradients. However, we
find no correlation between the FUV-B color gradients and internal metallicity
gradients based on Mg absorption features. We conclude that metallicity is not
the sole parameter controlling the "UV upturn component" in old populations.Comment: 11 pages; tar.gz file includes LaTeX text file, 3 PostScript figures.
Paper to be published in ApJ Letter
Irreversible dynamics of the phase boundary in U(Ru0.9)Rh0.04)2Si2 and implications for ordering
We report measurements and analysis of the specific heat and magnetocaloric
effect at the phase boundary into the single magnetic field-induced phase
(phase II) of U(Ru{0.96}Rh{0.04})2Si2, which yield striking similarities to the
valence transition of Yb{1-x}YxInCu4. To explain these similarities, we propose
a bootstrap mechanism by which a structural distortion causes an electric
quadrupolar order parameter within phase II to become coupled to the
5f-electron hybridization, giving rise to a valence change at the transition.Comment: 4 pages including 4 figure
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