350 research outputs found
A Concentration/Purification Scheme for Two Partially Entangled Photon Pairs
An experimental scheme for concentrating entanglement in partially entangled
photon pairs is proposed. In this scheme, two separated parties obtain one
maximally entangled photon pair from previously shared two partially entangled
photon pairs by local operations and classical communication. A practical
realization of the proposed scheme is discussed, which uses imperfect photon
detectors and spontaneous parametric down-conversion as a photon source. This
scheme also works for purifying a class of mixed states.Comment: 8 pages, 3 figure
Squeezed States for General Systems
We propose a ladder-operator method for obtaining the squeezed states of
general symmetry systems. It is a generalization of the annihilation-operator
technique for obtaining the coherent states of symmetry systems. We connect
this method with the minimum-uncertainty method for obtaining the squeezed and
coherent states of general potential systems, and comment on the distinctions
between these two methods and the displacement-operator method.Comment: 8 pages, LAUR-93-1721, LaTe
Generation of phase-coherent states
An interaction scheme involving nonlinear media is suggested for
the generation of phase-coherent states (PCS). The setup is based on parametric
amplification of vacuum followed by up-conversion of the resulting twin-beam.
The involved nonlinear interactions are studied by the exact numerical
diagonalization. An experimentally achievable working regime to approximate PCS
with high conversion rate is given, and the validity of parametric
approximation is discussed.Comment: To appear in PRA -- More info at http://enterprise.pv.infn.it
Algebraic approach in the study of time-dependent nonlinear integrable systems: Case of the singular oscillator
The classical and the quantal problem of a particle interacting in
one-dimension with an external time-dependent quadratic potential and a
constant inverse square potential is studied from the Lie-algebraic point of
view. The integrability of this system is established by evaluating the exact
invariant closely related to the Lewis and Riesenfeld invariant for the
time-dependent harmonic oscillator. We study extensively the special and
interesting case of a kicked quadratic potential from which we derive a new
integrable, nonlinear, area preserving, two-dimensional map which may, for
instance, be used in numerical algorithms that integrate the
Calogero-Sutherland-Moser Hamiltonian. The dynamics, both classical and
quantal, is studied via the time-evolution operator which we evaluate using a
recent method of integrating the quantum Liouville-Bloch equations \cite{rau}.
The results show the exact one-to-one correspondence between the classical and
the quantal dynamics. Our analysis also sheds light on the connection between
properties of the SU(1,1) algebra and that of simple dynamical systems.Comment: 17 pages, 4 figures, Accepted in PR
Sound archaeology: terminology, Palaeolithic cave art and the soundscape
This article is focused on the ways that terminology describing the study of music and sound within archaeology has changed over time, and how this reflects developing methodologies, exploring the expectations and issues raised by the use of differing kinds of language to define and describe such work. It begins with a discussion of music archaeology, addressing the problems of using the term ‘music’ in an archaeological context. It continues with an examination of archaeoacoustics and acoustics, and an emphasis on sound rather than music. This leads on to a study of sound archaeology and soundscapes, pointing out that it is important to consider the complete acoustic ecology of an archaeological site, in order to identify its affordances, those possibilities offered by invariant acoustic properties. Using a case study from northern Spain, the paper suggests that all of these methodological approaches have merit, and that a project benefits from their integration
Recommended from our members
Experiments in fireproofing wood : fifth progress report
Reviewed and reaffirmed November 1956
Recommended from our members
Experiments in fireproofing wood
Fourth progress report. Published in 1933 Proceedings of the American Wood Preservers Association
An empirical temperature calibration for the Delta a photometric system. I. The B-type stars
We establish an empirical effective temperature calibration of main sequence,
luminosity class V to III B-type stars for the Delta a photometric system which
was originally developed to detect magnetic chemically peculiar objects of the
upper main sequence (early B-type to early F-type) at 5200A. However, this
system provides the index (g1-y) which shows an excellent correlation with
(B-V) as well as (b-y) and can be used as an indicator of the effective
temperature. This is supplemented by a very accurate color-magnitude diagram, y
or V versus (g1-y), which can be used, for example, to determine the reddening,
distance and age of an open cluster. This makes the Delta a photometric system
an excellent tool to investigate the Hertzsprung-Russell-Diagram (HRD) in more
detail. Using the reddening-free parameters and already established
calibrations within the Stromgren uvbybeta, Geneva 7-color and Johnson UBV
systems, a polynomial fit of third degree for the averaged effective
temperatures to the individual (g1-y)0 values was derived. For this purpose,
data from the literature as well as new observations were taken resulting in
225 suitable bright normal B-type objects. The statistical mean of the error
for this sample is 238K which is sufficient to investigate the HRD of distant
galactic open clusters as well as extragalactic aggregates in the future.Comment: 7 pages, 5 figures, accepted by A&
Dysregulated Recruitment of the Histone Methyltransferase EZH2 to the Class II Transactivator (CIITA) Promoter IV in Breast Cancer Cells
One mechanism frequently utilized by tumor cells to escape immune system recognition and elimination is suppression of cell surface expression of Major Histocompatibility Class II (MHC II) molecules. Expression of MHC II is regulated primarily at the level of transcription by the Class II Transactivator, CIITA, and decreased CIITA expression is observed in multiple tumor types. We investigate here contributions of epigenetic modifications to transcriptional silencing of CIITA in variants of the human breast cancer cell line MDA MB 435. Significant increases in histone H3 lysine 27 trimethylation upon IFN-γ stimulation correlate with reductions in transcription factor recruitment to the interferon-γ inducible CIITA promoter, CIITApIV, and with significantly increased CIITApIV occupancy by the histone methyltransferase enhancer of zeste homolog 2 (EZH2). Most compelling is evidence that decreased expression of EZH2 in MDA MB 435 variants results in significant increases in CIITA and HLA-DRA mRNA expression, even in the absence of interferon-γ stimulation, as well as increased cell surface expression of MHC II. Together, these data add mechanistic insight to prior observations of increased EZH2 expression and decreased CIITA expression in multiple tumor types
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