2,431 research outputs found
Extreme Quantum Advantage for Rare-Event Sampling
We introduce a quantum algorithm for efficient biased sampling of the rare
events generated by classical memoryful stochastic processes. We show that this
quantum algorithm gives an extreme advantage over known classical biased
sampling algorithms in terms of the memory resources required. The quantum
memory advantage ranges from polynomial to exponential and when sampling the
rare equilibrium configurations of spin systems the quantum advantage diverges.Comment: 11 pages, 9 figures;
http://csc.ucdavis.edu/~cmg/compmech/pubs/eqafbs.ht
Optimizing Quantum Models of Classical Channels: The reverse Holevo problem
Given a classical channel---a stochastic map from inputs to outputs---the
input can often be transformed to an intermediate variable that is
informationally smaller than the input. The new channel accurately simulates
the original but at a smaller transmission rate. Here, we examine this
procedure when the intermediate variable is a quantum state. We determine when
and how well quantum simulations of classical channels may improve upon the
minimal rates of classical simulation. This inverts Holevo's original question
of quantifying the capacity of quantum channels with classical resources. We
also show that this problem is equivalent to another, involving the local
generation of a distribution from common entanglement.Comment: 13 pages, 6 figures;
http://csc.ucdavis.edu/~cmg/compmech/pubs/qfact.htm; substantially updated
from v
A procedure for assessing aircraft turbulence- penetration performance
Subsonic transport aircraft performance assessment during atmospheric turbulenc
Coupled Oscillators with Chemotaxis
A simple coupled oscillator system with chemotaxis is introduced to study
morphogenesis of cellular slime molds. The model successfuly explains the
migration of pseudoplasmodium which has been experimentally predicted to be
lead by cells with higher intrinsic frequencies. Results obtained predict that
its velocity attains its maximum value in the interface region between total
locking and partial locking and also suggest possible roles played by partial
synchrony during multicellular development.Comment: 4 pages, 5 figures, latex using jpsj.sty and epsf.sty, to appear in
J. Phys. Soc. Jpn. 67 (1998
CCD Readout Electronics for the Subaru Prime Focus Spectrograph
We present details of the design for the CCD readout electronics for the
Subaru Telescope Prime Focus Spectrograph (PFS). The spectrograph is comprised
of four identical spectrograph modules, each collecting roughly 600 spectra.
The spectrograph modules provide simultaneous wavelength coverage over the
entire band from 380 nm to 1260 nm through the use of three separate optical
channels: blue, red, and near infrared (NIR). A camera in each channel images
the multi-object spectra onto a 4k x 4k, 15 um pixel, detector format. The two
visible cameras use a pair of Hamamatsu 2k x 4k CCDs with readout provided by
custom electronics, while the NIR camera uses a single Teledyne HgCdTe 4k x 4k
detector and ASIC Sidecar to read the device.
The CCD readout system is a custom design comprised of three electrical
subsystems: the Back End Electronics (BEE), the Front End Electronics (FEE),
and a Pre-amplifier. The BEE is an off-the-shelf PC104 computer, with an
auxiliary Xilinx FPGA module. The computer serves as the main interface to the
Subaru messaging hub and controls other peripheral devices associated with the
camera, while the FPGA is used to generate the necessary clocks and transfer
image data from the CCDs. The FEE board sets clock biases, substrate bias, and
CDS offsets. It also monitors bias voltages, offset voltages, power rail
voltage, substrate voltage and CCD temperature. The board translates LVDS clock
signals to biased clocks and returns digitized analog data via LVDS. Monitoring
and control messages are sent from the BEE to the FEE using a standard serial
interface. The Pre-amplifier board resides behind the detectors and acts as an
interface to the two Hamamatsu CCDs. The Pre-amplifier passes clocks and biases
to the CCDs, and analog CCD data is buffered and amplified prior to being
returned to the FEE.Comment: 14 pages, 15 figures, SPIE ATI 2014, Montrea
Quantitative analysis of cell types during growth and morphogenesis in Hydra
Tissue maceration was used to determine the absolute number and the distribution of cell types in Hydra. It was shown that the total number of cells per animal as well as the distribution of cells vary depending on temperature, feeding conditions, and state of growth. During head and foot regeneration and during budding the first detectable change in the cell distribution is an increase in the number of nerve cells at the site of morphogenesis. These results and the finding that nerve cells are most concentrated in the head region, diminishing in density down the body column, are discussed in relation to tissue polarity
Detecting Weak Spectral Lines in Interferometric Data through Matched Filtering
Modern radio interferometers enable observations of spectral lines with unprecedented spatial resolution and sensitivity. In spite of these technical advances, many lines of interest are still at best weakly detected and therefore necessitate detection and analysis techniques specialized for the low signal-to-noise ratio (S/N) regime. Matched filters can leverage knowledge of the source structure and kinematics to increase sensitivity of spectral line observations. Application of the filter in the native Fourier domain improves S/N while simultaneously avoiding the computational cost and ambiguities associated with imaging, making matched filtering a fast and robust method for weak spectral line detection. We demonstrate how an approximate matched filter can be constructed from a previously observed line or from a model of the source, and we show how this filter can be used to robustly infer a detection significance for weak spectral lines. When applied to ALMA Cycle 2 observations of CH3OH in the protoplanetary disk around TW Hya, the technique yields a ≈53% S/N boost over aperture-based spectral extraction methods, and we show that an even higher boost will be achieved for observations at higher spatial resolution. A Python-based open-source implementation of this technique is available under the MIT license at http://github.com/AstroChem/VISIBLE
Chromospheric Variability in SDSS M Dwarfs. II. Short-Timescale H-alpha Variability
[Abridged] We present the first comprehensive study of short-timescale
chromospheric H-alpha variability in M dwarfs using the individual 15 min
spectroscopic exposures for 52,392 objects from the Sloan Digital Sky Survey.
Our sample contains about 10^3-10^4 objects per spectral type bin in the range
M0-M9, with a total of about 206,000 spectra and a typical number of 3
exposures per object (ranging up to a maximum of 30 exposures). Using this
extensive data set we find that about 16% of the sources exhibit H-alpha
emission in at least one exposure, and of those about 45% exhibit H-alpha
emission in all of the available exposures. Within the sample of objects with
H-alpha emission, only 26% are consistent with non-variable emission,
independent of spectral type. The H-alpha variability, quantified in terms of
the ratio of maximum to minimum H-alpha equivalent width (R_EW), and the ratio
of the standard deviation to the mean (sigma_EW/), exhibits a rapid rise
from M0 to M5, followed by a plateau and a possible decline in M9 objects. In
particular, R_EW increases from a median value of about 1.8 for M0-M3 to about
2.5 for M7-M9, and variability with R_EW>10 is only observed in objects later
than M5. For the combined sample we find that the R_EW values follow an
exponential distribution with N(R_EW) exp[-(R_EW-1)/2]; for M5-M9 objects the
characteristic scale is R_EW-1\approx 2.7, indicative of stronger variability.
In addition, we find that objects with persistent H-alpha emission exhibit
smaller values of R_EW than those with intermittent H-alpha emission. Based on
these results we conclude that H-alpha variability in M dwarfs on timescales of
15 min to 1 hr increases with later spectral type, and that the variability is
larger for intermittent sources.Comment: Submitted to ApJ; 20 pages, 15 figure
Public Benefits of Undeveloped Lands on Urban Outskirts: Non-Market Valuation Studies and their Role in Land Use Plans
Over the past three decades, the economics profession has developed methods for estimating the public benefits of green spaces, providing an opportunity to incorporate such information into land-use planning. While federal regulations routinely require such estimates for major regulations, the extent to which they are used in local land use plans is not clear. This paper reviews the literature on public values for lands on urban outskirts, not just to survey their methods or empirical findings, but to evaluate the role they have played--or have the potential to play-- in actual land use plans. Based on interviews with authors and representatives of funding agencies and local land trusts, it appears that academic work has had a mixed reception in the policy world. Reasons for this include a lack of interest in making academic work accessible to policy makers, emphasizing revealed preference methods which are inconsistent with policy priorities related to nonuse values, and emphasis on benefit-cost analyses. Nevertheless, there are examples of success stories that illustrate how such information can play a vital role in the design of conservation policies. Working Paper 07-2
- …