847 research outputs found
Learning about compact binary merger: the interplay between numerical relativity and gravitational-wave astronomy
Activities in data analysis and numerical simulation of gravitational waves
have to date largely proceeded independently. In this work we study how
waveforms obtained from numerical simulations could be effectively used within
the data analysis effort to search for gravitational waves from black hole
binaries. We propose measures to quantify the accuracy of numerical waveforms
for the purpose of data analysis and study how sensitive the analysis is to
errors in the waveforms. We estimate that ~100 templates (and ~10 simulations
with different mass ratios) are needed to detect waves from non-spinning binary
black holes with total masses in the range 100 Msun < M < 400 Msun using
initial LIGO. Of course, many more simulation runs will be needed to confirm
that the correct physics is captured in the numerical evolutions. From this
perspective, we also discuss sources of systematic errors in numerical waveform
extraction and provide order of magnitude estimates for the computational cost
of simulations that could be used to estimate the cost of parameter space
surveys. Finally, we discuss what information from near-future numerical
simulations of compact binary systems would be most useful for enhancing the
detectability of such events with contemporary gravitational wave detectors and
emphasize the role of numerical simulations for the interpretation of eventual
gravitational-wave observations.Comment: 19 pages, 12 figure
Exohedral Physisorption of Ambient Moisture Scales Non-monotonically with Fiber Proximity in Aligned Carbon Nanotube Arrays
Here we present a study on the presence of physisorbed water on the surface of aligned carbon nanotubes (CNTs) in ambient conditions, where the wet CNT array mass can be more than 200% larger than that of dry CNTs, and modeling indicates that a water layer >5 nm thick can be present on the outer CNT surface. The experimentally observed nonlinear and non-monotonic dependence of the mass of adsorbed water on the CNT packing (volume fraction) originates from two competing modes. Physisorbed water cannot be neglected in the design and fabrication of materials and devices using nanowires/nanofibers, especially CNTs, and further experimental and ab initio studies on the influence of defects on the surface energies of CNTs, and nanowires/nanofibers in general, are necessary to understand the underlying physics and chemistry that govern this system.National Science Foundation (U.S.) (NSF Grant No. CMMI-1130437)National Science Foundation (U.S.) (NSF Award Number ECS-0335765)United States. Army Research Office (contract W911NF-07-D-0004
142: Low dose thalidomide maintenance in myeloma patients after autologous stem cell transplantation
Impact of carbon nanotube length on electron transport in aligned carbon nanotube networks
Here, we quantify the electron transport properties of aligned carbon nanotube (CNT) networks as a function of the CNT length, where the electrical conductivities may be tuned by up to 10× with anisotropies exceeding 40%. Testing at elevated temperatures demonstrates that the aligned CNT networks have a negative temperature coefficient of resistance, and application of the fluctuation induced tunneling model leads to an activation energy of ≈14 meV for electron tunneling at the CNT-CNT junctions. Since the tunneling activation energy is shown to be independent of both CNT length and orientation, the variation in electron transport is attributed to the number of CNT-CNT junctions an electron must tunnel through during its percolated path, which is proportional to the morphology of the aligned CNT network.United States. Army Research Office (contract W911NF-07-D-0004)United States. Army Research Office (contract W911NF-13-D-0001)United States. Air Force Office of Scientific Research (AFRL/RX contract FA8650-11-D-5800, Task Order 0003)National Science Foundation (U.S.) (NSF Award No. ECS-0335765)United States. Dept. of Defense (National Defense Science and Engineering Graduate Fellowship
A microfabricated sensor for thin dielectric layers
We describe a sensor for the measurement of thin dielectric layers capable of
operation in a variety of environments. The sensor is obtained by
microfabricating a capacitor with interleaved aluminum fingers, exposed to the
dielectric to be measured. In particular, the device can measure thin layers of
solid frozen from a liquid or gaseous medium. Sensitivity to single atomic
layers is achievable in many configurations and, by utilizing fast, high
sensitivity capacitance read out in a feedback system onto environmental
parameters, coatings of few layers can be dynamically maintained. We discuss
the design, read out and calibration of several versions of the device
optimized in different ways. We specifically dwell on the case in which
atomically thin solid xenon layers are grown and stabilized, in cryogenic
conditions, from a liquid xenon bath
Two-atom dark states in electromagnetic cavities
The center-of-mass motion of two two-level atoms coupled to a single damped
mode of an electromagnetic resonator is investigated. For the case of one atom
being initially excited and the cavity mode in the vacuum state it is shown
that the atomic time evolution is dominated by the appearance of dark states.
These states, in which the initial excitation is stored in the internal atomic
degrees of freedom and the atoms become quantum mechanically entangled, are
almost immune against photon loss from the cavity. Various properties of the
dark states within and beyond the Raman-Nath approximation of atom optics are
worked out.Comment: 8 pages, 4 figure
Sympathetic Cooling of Trapped Cd+ Isotopes
We sympathetically cool a trapped 112Cd+ ion by directly Doppler-cooling a
114Cd+ ion in the same trap. This is the first demonstration of optically
addressing a single trapped ion being sympathetically cooled by a different
species ion. Notably, the experiment uses a single laser source, and does not
require strong focusing. This paves the way toward reducing decoherence in an
ion trap quantum computer based on Cd+ isotopes.Comment: 4 figure
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