1,231 research outputs found
Trialling body-worn video cameras for City of London Police: officer perceptions and justice outcomes
Repor
Control system design using optimization techniques Final report
Optimization techniques for control of fuel valve systems for air breathing jet engines and 40-60 inlet control problem
Terminal deoxynucleotidyl transferase is found in prothymocytes
Terminal deoxynucleotidyl transferase is an enzyme which has the unique property of polymerizing polydeoxynucleotides onto a primer in the absence of a template (1,2). This enzyme is found both in the thymus and the bone marrow of birds, rodents, and humans (3-7). Whether the marrow cells that contain terminal transferase are related to thymocytes, or are on a separate pathway of differentiation, is not yet known (7,8). To determine the lineage of the murine bone marrow cells that have terminal transferase, we have investigated whether these cells have the antigen Thy-1 induced on the cells by treatment with thymopoietin (9). Thymopoietin is known to induce a set of characteristic T-cell markers including the Thy-1 alloantigen on the surface of a subpopulation of bone marrow cells committed to T-cell differentiation (prothymocytes) (10). Destruction of Thy- 1-positive cells after exposure to thymopoietin allows elimination of a substantial fraction of those bone marrow cells that can repopulate an irradiated thymus (11). We find that such an elimination after induction with the thymic polypeptide removes a substantial amount of terminal transferase from the bone marrow cell population, suggesting that at least one-half of the marrow cells bearing this enzyme are related to those found in the thymus
Multi-wavelength modeling of the spatially resolved debris disk of HD 107146
(abridged) We aim to constrain the location, composition, and dynamical state
of planetesimal populations and dust around the young, sun-like (G2V) star HD
107146}. We consider coronagraphic observations obtained with the Advanced
Camera for Surveys (HST/ACS) onboard the HST in broad V and broad I filters, a
resolved 1.3mm map obtained with the Combined Array for Research in
Millimeter-Wave Astronomy (CARMA), Spitzer/IRS low resolution spectra, and the
spectral energy distribution (SED) of the object at wavelengths ranging from
3.5micron to 3.1mm. We complement these data with new coronagraphic high
resolution observations of the debris disk using the Near Infrared Camera and
Multi-Object Spectrometer (HST/NICMOS) aboard the HST in the F110W filter. The
SED and images of the disk in scattered light as well as in thermal reemission
are combined in our modeling using a parameterized model for the disk density
distribution and optical properties of the dust. A detailed analytical model of
the debris disk around HD 107146 is presented that allows us to reproduce the
almost entire set of spatially resolved and unresolved multi-wavelength
observations. Considering the variety of complementary observational data, we
are able to break the degeneracies produced by modeling SED data alone. We find
the disk to be an extended ring with a peak surface density at 131AU.
Furthermore, we find evidence for an additional, inner disk probably composed
of small grains released at the inner edge of the outer disk and moving inwards
due to Poynting-Robertson drag. A birth ring scenario (i.e., a more or less
broad ring of planetesimals creating the dust disk trough collisions) is found
to be the most likely explanation of the ringlike shape of the disk.Comment: 15 pages, 9 figures, accepted for publication in A&
The Formation and Evolution of Planetary Systems: Description of the Spitzer Legacy Science Database
We present the science database produced by the Formation and Evolution of
Planetary Systems (FEPS) Spitzer Legacy program. Data reduction and validation
procedures for the IRAC, MIPS, and IRS instruments are described in detail. We
also derive stellar properties for the FEPS sample from available broad-band
photometry and spectral types, and present an algorithm to normalize Kurucz
synthetic spectra to optical and near-infrared photometry. The final FEPS data
products include IRAC and MIPS photometry for each star in the FEPS sample and
calibrated IRS spectra.Comment: 64 pages, 12 figures, 5 tables; accepted for publication in ApJ
Resummation of Nonalternating Divergent Perturbative Expansions
A method for the resummation of nonalternating divergent perturbation series
is described. The procedure constitutes a generalization of the Borel-Pad\'{e}
method. Of crucial importance is a special integration contour in the complex
plane. Nonperturbative imaginary contributions can be inferred from the purely
real perturbative coefficients. A connection is drawn from the quantum field
theoretic problem of resummation to divergent perturbative expansions in other
areas of physics.Comment: 5 pages, LaTeX, 2 tables, 1 figure; discussion of the Carleman
criterion added; version to appear in Phys. Rev.
Discovery of a Nearly Edge-On Disk Around HD 32297
We report the discovery of a nearly edge-on disk about the A0 star HD 32297
seen in light scattered by the disk grains revealed in NICMOS PSF-subtracted
coronagraphic images. The disk extends to a distance of at least 400 AU (3.3")
along its major axis with a 1.1 micron flux density of 4.81 +/-0.57 mJy beyond
a radius of 0.3" from the coronagraphically occulted star. The fraction of 1.1
micron starlight scattered by the disk, 0.0033 +/- 0.0004, is comparable to its
fractional excess emission at 25 + 60 micron of ~ 0.0027 as measured from IRAS
data. The disk appears to be inclined 10.5 degrees +/- 2.5 degrees from an
edge-on viewing geometry, with its major axis oriented 236.5 degrees +/- 1
degree eastward of north. The disk exhibits unequal brightness in opposing
sides and a break in the surface brightness profile along NE-side disk major
axis. Such asymmetries might implicate the existence of one or more (unseen)
planetary mass companions.Comment: 12 pages, 2 figures, accepted for publication in ApJ
Witnessing eigenstates for quantum simulation of Hamiltonian spectra
The efficient calculation of Hamiltonian spectra, a problem often intractable
on classical machines, can find application in many fields, from physics to
chemistry. Here, we introduce the concept of an "eigenstate witness" and
through it provide a new quantum approach which combines variational methods
and phase estimation to approximate eigenvalues for both ground and excited
states. This protocol is experimentally verified on a programmable silicon
quantum photonic chip, a mass-manufacturable platform, which embeds entangled
state generation, arbitrary controlled-unitary operations, and projective
measurements. Both ground and excited states are experimentally found with
fidelities >99%, and their eigenvalues are estimated with 32-bits of precision.
We also investigate and discuss the scalability of the approach and study its
performance through numerical simulations of more complex Hamiltonians. This
result shows promising progress towards quantum chemistry on quantum computers.Comment: 9 pages, 4 figures, plus Supplementary Material [New version with
minor typos corrected.
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