594 research outputs found
Large-scale Oscillation of Structure-Related DNA Sequence Features in Human Chromosome 21
Human chromosome 21 is the only chromosome in human genome that exhibits
oscillation of (G+C)-content of cycle length of hundreds kilobases (500 kb near
the right telomere). We aim at establishing the existence of similar
periodicity in structure-related sequence features in order to relate this
(G+C)% oscillation to other biological phenomena. The following quantities are
shown to oscillate with the same 500kb periodicity in human chromosome 21:
binding energy calculated by two sets of dinucleotide-based thermodynamic
parameters, AA/TT and AAA/TTT bi-/tri-nucleotide density, 5'-TA-3' dinucleotide
density, and signal for 10/11-base periodicity of AA/TT or AAA/TTT. These
intrinsic quantities are related to structural features of the double helix of
DNA molecules, such as base-pair binding, untwisting/unwinding, stiffness, and
a putative tendency for nucleosome formation.Comment: submitted to Physical Review
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
Characterization of high finesse mirrors: loss, phase shifts and mode structure in an optical cavity
An extensive characterization of high finesse optical cavities used in cavity
QED experiments is described. Different techniques in the measurement of the
loss and phase shifts associated with the mirror coatings are discussed and
their agreement shown. Issues of cavity field mode structure supported by the
dielectric coatings are related to our effort to achieve the strongest possible
coupling between an atom and the cavity.Comment: 8 pages, 4 figure
Comparisons of binary black hole merger waveforms
This a particularly exciting time for gravitational wave physics.
Ground-based gravitational wave detectors are now operating at a sensitivity
such that gravitational radiation may soon be directly detected, and recently
several groups have independently made significant breakthroughs that have
finally enabled numerical relativists to solve the Einstein field equations for
coalescing black-hole binaries, a key source of gravitational radiation. The
numerical relativity community is now in the position to begin providing
simulated merger waveforms for use by the data analysis community, and it is
therefore very important that we provide ways to validate the results produced
by various numerical approaches. Here, we present a simple comparison of the
waveforms produced by two very different, but equally successful
approaches--the generalized harmonic gauge and the moving puncture methods. We
compare waveforms of equal-mass black hole mergers with minimal or vanishing
spins. The results show exceptional agreement for the final burst of radiation,
with some differences attributable to small spins on the black holes in one
case.Comment: Revtex 4, 5 pages. Published versio
Mobility of thorium ions in liquid xenon
We present a measurement of the Th ion mobility in LXe at 163.0 K and
0.9 bar. The result obtained, 0.2400.011 (stat) 0.011 (syst)
cm/(kV-s), is compared with a popular model of ion transport.Comment: 6.5 pages,
The theory of heating of the quantum ground state of trapped ions
Using a displacement operator formalism, I analyse the depopulation of the
vibrational ground state of trapped ions. Two heating times, one characterizing
short time behaviour, the other long time behaviour are found. The short time
behaviour is analyzed both for single and multiple ions, and a formula for the
relative heating rates of different modes is derived. The possibility of
correction of heating via the quantum Zeno effect, and the exploitation of the
suppression of heating of higher modes to reduce errors in quantum computation
is considered.Comment: 9 pages, 2 figure
Destabilization of dark states and optical spectroscopy in Zeeman-degenerate atomic systems
We present a general discussion of the techniques of destabilizing dark
states in laser-driven atoms with either a magnetic field or modulated laser
polarization. We show that the photon scattering rate is maximized at a
particular evolution rate of the dark state. We also find that the atomic
resonance curve is significantly broadened when the evolution rate is far from
this optimum value. These results are illustrated with detailed examples of
destabilizing dark states in some commonly-trapped ions and supported by
insights derived from numerical calculations and simple theoretical models.Comment: 14 pages, 10 figure
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