3,514 research outputs found
Clementine Sensor Processing System
The design of the DSPSE Satellite Controller (DSC) is baselined as a single-string satellite controller. The DSC performs two main functions: health and maintenance of the spacecraft; and image capture, storage, and playback. The DSC contains two processors: a radiation-hardened Mil-Std-1750, and a commercial R3000. The Mil-Std-1750 processor performs all housekeeping operations, while the R3000 is mainly used to perform the image processing functions associated with the navigation functions, as well as performing various experiments. The DSC also contains a data handling unit (DHU) used to interface to various spacecraft imaging sensors and to capture, compress, and store selected images onto the solid-state data recorder. The development of the DSC evolved from several key requirements; the DSPSE satellite was to do the following: (1) have a radiation-hardened spacecraft control system and be immune to single-event upsets (SEU's); (2) use an R3000-based processor to run the star tracker software that was developed by SDIO (due to schedule and cost constraints, there was no time to port the software to a radiation-hardened processor); and (3) fly a commercial processor to verify its suitability for use in a space environment. In order to enhance the DSC reliability, the system was designed with multiple processing paths. These multiple processing paths provide for greater tolerance to various component failures. The DSC was designed so that all housekeeping processing functions are performed by either the Mil-Std-1750 processor or the R3000 processor. The image capture and storage is performed either by the DHU or the R3000 processor
Error bounds for compound quadrature of weakly singular integrals
Prediction of slow convergence rates for weakly singular numerical quadrature
Smoothness of solutions of Volterra integral equations with weakly singular kernels
Solution smoothness of Volterra integral equations with weakly singular kernel
The use of ultrasound in clinical setting for children affected by NAFLD. is it safe and accurate?
Non-alcoholic fatty liver disease (NAFLD) has become over the last decade the most common form of chronic liver disease in children and adults. Thus, establishing the diagnosis of NAFLD is of utmost importance and represents a major challenge as the disease is generally silent and the current gold standard for diagnosis is an invasive liver biopsy, a procedure that is not suitable for screening purposes. Many non-invasive diagnostic tools have been evaluated so far. Recently the utility of ultrasonography for non-invasive diagnosis and estimation of hepatic steatosis has been demonstrated in a large prospective pediatric study
System and method for moving a probe to follow movements of tissue
An apparatus is described for moving a probe that engages moving living tissue such as a heart or an artery that is penetrated by the probe, which moves the probe in synchronism with the tissue to maintain the probe at a constant location with respect to the tissue. The apparatus includes a servo positioner which moves a servo member to maintain a constant distance from a sensed object while applying very little force to the sensed object, and a follower having a stirrup at one end resting on a surface of the living tissue and another end carrying a sensed object adjacent to the servo member. A probe holder has one end mounted on the servo member and another end which holds the probe
About the relationship between auroral electrojets and ring currents
International audienceThe relationship between the storm-time ring current and the auroral electrojets is investigated using IMAGE magnetometer data, DSt and H-SYM, and solar wind data. Statistical results as well as the investigation of single events show that the auroral electrojets occur also during nonstorm conditions without storm-time ring current development and even during the storm recovery phase of increasing DSt. A close correlation between electrojet intensity and ring current intensity was not found. Though the eastward electrojet moves equatorward during the storm main phase there is no unequivocal relationship between the movement of the westward electrojet and the ring current development. All these results suggest that the auroral electrojets and the ring current develop more or less independently of each other
The Effective Field Theory of Dark Matter Direct Detection
We extend and explore the general non-relativistic effective theory of dark
matter (DM) direct detection. We describe the basic non-relativistic building
blocks of operators and discuss their symmetry properties, writing down all
Galilean-invariant operators up to quadratic order in momentum transfer arising
from exchange of particles of spin 1 or less. Any DM particle theory can be
translated into the coefficients of an effective operator and any effective
operator can be simply related to most general description of the nuclear
response. We find several operators which lead to novel nuclear responses.
These responses differ significantly from the standard minimal WIMP cases in
their relative coupling strengths to various elements, changing how the results
from different experiments should be compared against each other. Response
functions are evaluated for common DM targets - F, Na, Ge, I, and Xe - using
standard shell model techniques. We point out that each of the nuclear
responses is familiar from past studies of semi-leptonic electroweak
interactions, and thus potentially testable in weak interaction studies. We
provide tables of the full set of required matrix elements at finite momentum
transfer for a range of common elements, making a careful and fully
model-independent analysis possible. Finally, we discuss embedding
non-relativistic effective theory operators into UV models of dark matter.Comment: 32+23 pages, 5 figures; v2: some typos corrected and definitions
clarified; v3: some factors of 4pi correcte
Landscape Predictions for the Higgs Boson and Top Quark Masses
If the Standard Model is valid up to scales near the Planck mass, and if the
cosmological constant and Higgs mass parameters scan on a landscape of vacua,
it is well known that the observed orders of magnitude of these quantities can
be understood from environmental selection for large-scale structure and atoms.
If in addition the Higgs quartic coupling scans, with a probability
distribution peaked at low values, environmental selection for a phase having a
scale of electroweak symmetry breaking much less than the Planck scale leads to
a most probable Higgs mass of 106 GeV. While fluctuations below this are
negligible, the upward fluctuation is 25/p GeV, where p measures the strength
of the peaking of the a priori distribution of the quartic coupling. If the top
Yukawa coupling also scans, the most probable top quark mass is predicted to
lie in the range (174--178) GeV, providing the standard model is valid to at
least 10^{17} GeV. The downward fluctuation is 35 GeV/ \sqrt{p}, suggesting
that p is sufficiently large to give a very precise Higgs mass prediction.
While a high reheat temperature after inflation could raise the most probable
value of the Higgs mass to 118 GeV, maintaining the successful top prediction
suggests that reheating is limited to about 10^8 GeV, and that the most
probable value of the Higgs mass remains at 106 GeV. If all Yukawa couplings
scan, then the e,u,d and t masses are understood to be outliers having extreme
values induced by the pressures of strong environmental selection, while the s,
\mu, c, b, \tau Yukawa couplings span only two orders of magnitude, reflecting
an a priori distribution peaked around 10^{-3}. Extensions of these ideas allow
order of magnitude predictions for neutrino masses, the baryon asymmetry and
important parameters of cosmological inflation.Comment: 41 pages; v4: threshold corrrections for top Yukawa are correcte
A Simple Explanation for DAMA with Moderate Channeling
We consider the possibility that the DAMA signal arises from channeled events
in simple models where the dark matter interaction with nuclei is suppressed at
small momenta. As with the standard WIMP, these models have two parameters (the
dark matter mass and the size of the cross-section), without the need to
introduce an additional energy threshold type of parameter. We find that they
can be consistent with channeling fractions as low as about ~ 15%, so long as
at least ~70% of the nuclear recoil energy for channeled events is deposited
electronically. Given that there are reasons not to expect very large
channeling fractions, these scenarios make the channeling explanation of DAMA
much more compelling.Comment: 6 pages, 2 figure
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