39,671 research outputs found
Reading Between the Lines
“Why do so many people come to our country? They come here and they take pictures, and then they go home and use them to show that we are a terrible place. Why do you do this?”
This question was posed to me by a sixteen-year old boy in Port-Au-Prince, Haiti while I was visiting his school on a post-earthquake relief trip in 2012. [excerpt
Fearless: Conor Brooks
Recently named College Democrat of the Year for the entire state of Pennsylvania, Conor Brooks ’15 fearlessly advocates for political awareness, involvement, and participation, uses his leadership skills to affect change in Adams County, and helps break down stereotypes people have about the apathy and political illiteracy of college students
Optimization of satellite altimeter and wave height measurements
Two techniques for simultaneously estimating altitude, ocean wave height, and signal-to-noise ratio from the GEOS-C satellite altimeter data are described. One technique was based on maximum likelihood estimation, MLE, and the other on minimum mean square error estimation, MMSE. Performance was determined by comparing the variance and bias of each technique with the variance and bias of the smoothed output from the Geos altimeter tracker. Ocean wave height tracking performance for the MLE and MMSE algorithms was measured by comparing the variance and bias of the wave height estimates with that of the expression for the return waveform obtained by a fit to the average output of the 16 waveform sampling gates
The Influence of high pressure on the bending rigidity of model membranes
Curvature is a fundamental lipid
membrane property that influences
many membrane-mediated biological processes and dynamic soft materials.
One of the key parameters that determines the energetics of curvature
change is the membrane bending rigidity. Understanding the intrinsic
effect of pressure on membrane bending is critical to understanding
the adaptation and structural behavior of biomembranes in deep-sea
organisms as well as soft material processing. However, it has not
previously been possible to measure the influence of high hydrostatic
pressure on membrane bending energetics, and this bottleneck has primarily
been due to a lack of technology platforms for performing such measurements.
We have developed a new high-pressure microscopy cell which, combined
with vesicle fluctuation analysis, has allowed us to make the first
measurements of membrane bending rigidity as a function of pressure.
Our results show a significant increase in bending rigidity at pressures
up to 40 MPa. Above 40 MPa, the membrane mechanics become more complex.
Corresponding small and wide-angle X-ray diffraction shows an increase
in density and thickness of the bilayer with increasing pressure which
correlates with the micromechanical measurements. These results are
consistent with recent theoretical predictions of the bending rigidity
as a function of hydrocarbon chain density. This technology has the
potential to transform our quantitative understanding of the role
of pressure in soft material processing, the structural behavior of
biomembranes, and the adaptation mechanisms employed by deep-sea organisms
Technical guidance and analytic services in support of SEASAT-A
The design of a high resolution radar for altimetry and ocean wave height estimation was studied. From basic principles, it is shown that a short pulse wide beam radar is the most appropriate and recommended technique for measuring both altitude and ocean wave height. To achieve a topographic resolution of + or - 10 cm RMS at 5.0 meter RMS wave heights, as required for SEASAT-A, it is recommended that the altimeter design include an onboard adaptive processor. The resulting design, which assumes a maximum likelihood estimation (MLE) processor, is shown to satisfy all performance requirements. A design summary is given for the recommended radar altimeter, which includes a full deramp STRETCH pulse compression technique followed by an analog filter bank to separate range returns as well as the assumed MLE processor. The feedback loop implementation of the MLE on a digital computer was examined in detail, and computer size, estimation accuracies, and bias due to range sidelobes are given for the MLE with typical SEASAT-A parameters. The standard deviation of the altitude estimate was developed and evaluated for several adaptive and nonadaptive split-gate trackers. Split-gate tracker biases due to range sidelobes and transmitter noise are examined. An approximate closed form solution for the altimeter power return is derived and evaluated. The feasibility of utilizing the basic radar altimeter design for the measurement of ocean wave spectra was examined
The Physics Inside Topological Quantum Field Theories
We show that the equations of motion defined over a specific field space are
realizable as operator conditions in the physical sector of a generalized Floer
theory defined over that field space. The ghosts associated with such a
construction are found not to be dynamical. This construction is applied to
gravity on a four dimensional manifold, ; whereupon, we obtain Einstein's
equations via surgery, along , in a five-dimensional topological quantum
field theory.Comment: LaTeX, 7 page
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