5,400 research outputs found
Efficient and spectrally bright source of polarization-entangled photons
We demonstrate an efficient fiber-coupled source of nondegenerate
polarization entangled photons at 795 and 1609 nm using bidirectionally pumped
parametric down-conversion in bulk periodically poled lithium niobate. The
single-mode source has an inferred bandwidth of 50 GHz and a spectral
brightness of 300 pairs/s/GHz/mW of pump power that is suitable for narrowband
applications such as entanglement transfer from photonic to atomic qubits.Comment: 8 pages, 7 figures, submitted to Phys. Rev.
Applications of optical parametric downconversion : I. Self-phase locking, [and] II. Generation of entangled photon pairs in periodically-poled lithium niobate
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.Includes bibliographical references (p. 108-114).Nonlinear optics plays a key role in many applications not only as a means of frequency synthesis and control, but also as a source of twin photons and other nonclassical states of light. Advances in nonlinear materials, including engineered nonlinear interactions through the use of quasi-phase matching, have increased the flexibility and performance of many nonlinear optical devices. One of the devices presented in this thesis is a 2:1 frequency divider based on self-phase locking in a type-II phase matched optical parametric oscillator. This device is investigated both theoretically and experimentally. Results are also presented on fabrication of periodically-poled nonlinear crystals for quasi-phase matching in lithium niobate and barium magnesium fluoride. Finally, a high-efficiency frequency-nondegenerate twin photon source is implemented in periodically-poled lithium niobate.by Elliott J. Mason, III.Ph.D
Efficient generation of tunable photon pairs at 0.8 and 1.6 micrometer
We demonstrate efficient generation of collinearly propagating, highly
nondegenerate photon pairs in a periodically-poled lithium niobate cw
parametric downconverter with an inferred pair generation rate of 1.4*10^7/s/mW
of pump power. Detection of an 800-nm signal photon triggers a
thermoelectrically-cooled 20%-efficient InGaAs avalanche photodiode for the
detection of the 1600-nm conjugate idler photon. Using single-mode fibers as
spatial mode filters, we obtain a signal-conditioned idler-detection
probability of about 3.1%.Comment: 8 pages, 3 figure
Theology, News and Notes - Vol. 15, No. 04
Theology News & Notes was a theological journal published by Fuller Theological Seminary from 1954 through 2014.https://digitalcommons.fuller.edu/tnn/1036/thumbnail.jp
Lines, Circles, Planes and Spheres
Let be a set of points in , no three collinear and not
all coplanar. If at most are coplanar and is sufficiently large, the
total number of planes determined is at least . For similar conditions and
sufficiently large , (inspired by the work of P. D. T. A. Elliott in
\cite{Ell67}) we also show that the number of spheres determined by points
is at least , and this bound is best
possible under its hypothesis. (By , we are denoting the
maximum number of three-point lines attainable by a configuration of
points, no four collinear, in the plane, i.e., the classic Orchard Problem.)
New lower bounds are also given for both lines and circles.Comment: 37 page
'Reaching the hard to reach' - lessons learned from the VCS (voluntary and community Sector). A qualitative study.
Background The notion 'hard to reach' is a contested and ambiguous term that is commonly used within the spheres of social care and health, especially in discourse around health and social inequalities. There is a need to address health inequalities and to engage in services the marginalized and socially excluded sectors of society. Methods This paper describes a pilot study involving interviews with representatives from eight Voluntary and Community Sector (VCS) organisations . The purpose of the study was to explore the notion of 'hard to reach' and perceptions of the barriers and facilitators to accessing services for 'hard to reach' groups from a voluntary and community sector perspective. Results The 'hard to reach' may include drug users, people living with HIV, people from sexual minority communities, asylum seekers, refugees, people from black and ethnic minority communities, and homeless people although defining the notion of the 'hard to reach' is not straight forward. It may be that certain groups resist engaging in treatment services and are deemed hard to reach by a particular service or from a societal stance. There are a number of potential barriers for people who may try and access services, including people having bad experiences in the past; location and opening times of services and how services are funded and managed. A number of areas of commonality are found in terms of how access to services for 'hard to reach' individuals and groups could be improved including: respectful treatment of service users, establishing trust with service users, offering service flexibility, partnership working with other organisations and harnessing service user involvement.
Conclusions: If health services are to engage with groups that are deemed 'hard to reach' and marginalised from mainstream health services, the experiences and practices for engagement from within the VCS may serve as useful lessons for service improvement for statutory health services
Communication: Analytic continuation of the virial series through the critical point using parametric approximants
The mathematical structure imposed by the thermodynamic critical point motivates an approximant that synthesizes two theoretically sound equations of state: the parametric and the virial. The former is constructed to describe the critical region, incorporating all scaling laws; the latter is an expansion about zero density, developed from molecular considerations. The approximant is shown to yield an equation of state capable of accurately describing properties over a large portion of the thermodynamic parameter space, far greater than that covered by each treatment alone
Exile Vol. XXXI No. 2
Plenty of Space by Carol Contiguglia (cover)
DĂ©nouement by Jeff Masten 3
The Ballad of Old Bill Brown by Amy Becker 4-5
Elegy by Ann Townsend 6
Untitled by Karen Koch 7
DĂ©nouement by Carol Mason 9-14
Untitled by N. R. B. III 15
A Lot in Common We Two, by David Zivan 17
The Sidewalk Taken, Kate Anthony 18
Upon Hearing Two Male Poets Read by Karen J. Hall 19
Leaves by Amy Becker 20
To Dad by Carrie Jordan 21
Attie Mae by Theresa Copeland 23-25
Oh, Henry by T. S. Elliott 26-38
Solitude; Normandy, France by Margie Boll 39
In Edgartown, Drunk, Stranded in the A.M. by Karen Kearney 41
Pink Feet by Catherine DuBois 42
Ensign in the Naval Corps of Engineers by Betsy Oster 43
Morning Haze by Stephanie Athey 44-45
Just Thought You\u27d Like to Know by Joan DeWitt 46-53
Art Class, A Study of Still-Lifes by Margie Boll 55
Contributor Notes 57
Editorial decision is shared equally among the Editorial Board members -cover page (credited here as editors )
PRINTING BY / PRINTING ARTS PRESS / MOUNT VERNON, OHIO -back cove
Optical Propagation and Communication
Contains an introduction and reports on three research projects.Maryland Procurement Office Contract MDA 904-93-C4169Maryland Procurement Office Contract MDA 903-94-C6071U.S. Air Force - Office of Scientific Research Grant F49620-93-1-0604MIT Lincoln Laboratory Advanced Concepts Program Contract CX-16335U.S. Army Research Office Grant DAAH04-93-G-0399U.S. Army Research Office Grant DAAH04-93-G-018
Teachersâ perspectives on collaboration with didacticians to create an inquiry community
This article was published in the journal, Research in Mathematics Education [Routledge © British Society for Research into Learning Mathematics]. The definitive version is available at: http://www.tandfonline.com/doi/abs/10.1080/14794800902732209A research and development project, Learning Communities in Mathematics
(LCM) was designed to create opportunities for âco-learning inquiryâ between
mathematics teachers in eight schools and didacticians in a university in Norway
(UiA). The focus has been on improving mathematics teaching and learning at
school levels from lower primary to upper secondary and on the developmental
processes and partnerships involved. A central aim was to create a community of
inquiry through which aspects of mathematics teaching and learning could be
explored, and through which both teachers and didacticians could learn in
practice. Theoretically, âCommunity of Inquiryâ derives from âCommunity of
Practiceâ as expounded by Lave andWenger, and particularlyWengerâs concept of
âbelongingâ. The project included three, one-year phases of joint activity. At the
end of Phase II, didacticians led focus group interviews with teacher teams to gain
insights into schoolsâ and teachersâ perceptions of the project and its activity. We
report on insights into how teachers thought about the activities of the project
and what an inquiry community looks like in terms of the learning of those
involved. We relate this back to the theoretical perspectives of communities of
practice and inquiry
- âŠ