68,575 research outputs found
A Method for Establishing Outdoor Recreation Project Priorities in Alaska
The authors thank Theodore Smith, Edward Kramer and Nat Goodhue
of the Division of Parks for information and comments supplied during this
study, and Frank Orth, Charles Marsh, Ed Kramer, C.E. Logsdon, and Frank
Wooding for reviewing the manuscript.
Thanks is also due the Department of Business Administration,
University of Alaska, Fairbanks, Dale Swanson, Head, for their cooperation
in this research project.The objectives of this study are to define outdoor recreation benefits to
the public and to develop a priority ranking method for proposed outdoor
recreation projects. A careful analysis of the benefits which people derive
from outdoor recreation provides a frame of reference for evaluating a
recreational facility. A project should supply those benefits which are most
highly demanded by the public. Fifteen benefits of recreation are defined
and discussed. They are divided into two major categories; those which
accrue to recreational participants and those which accrue to
non-participants.This research was supported by a grant from the Division of Parks,
State of Alaska
Theory of the correction of celestial observations made for space navigation or training
Theory of correction of celestial observations made for space navigation or trainin
Comment on "Kagome Lattice Antiferromagnet Stripped to Its Basics"
Density matrix renormalization group (DMRG) calculations on large systems (up
to 3096 spins) indicate that the ground state of the Heisenberg model on a
3-chain Kagome strip is spontaneously dimerized. This system has degenerate
ground states and a gap to triplet and singlet excitations. These results are
in direct contradiction with recent results of Azaria et al (Phys. Rev. Lett.
81, 1694 (1998)) and suggest a need for a reexamination of the underlying field
theory.Comment: 1 page, submitted to PR
Future of V/STOL aircraft systems: A survey of opinions
The recent success of the British Harriers in the Falkland Islands conflict vividly underscored the potential of V/STOL aircraft in military operations in a difficult environment. Despite this apparent success of the Harrier, there has been a major decline of V/STOL funding in the research and development budgets of the U.S. government and industry. The recent funding history of V/STOL systems is examined. Responses to a questionnaire which asked the question, Should there be an operational V/STOL aircraft other than the AV-8A and AV-8B in the military aircraft fleet of the U.S.A.? are presented and discussed
What do gas-rich galaxies actually tell us about modified Newtonian dynamics?
It has recently been claimed that measurements of the baryonic Tully-Fisher
relation (BTFR), a power-law relationship between the observed baryonic masses
and outer rotation velocities of galaxies, support the predictions of modified
Newtonian dynamics for the slope and scatter in the relation, while challenging
the cold dark matter (CDM) paradigm. We investigate these claims, and find
that: 1) the scatter in the data used to determine the BTFR is in conflict with
observational uncertainties on the data; 2) these data do not make strong
distinctions regarding the best-fit BTFR parameters; 3) the literature contains
a wide variety of measurements of the BTFR, many of which are discrepant with
the recent results; and 4) the claimed CDM "prediction" for the BTFR is a gross
oversimplification of the complex galaxy-scale physics involved. We conclude
that the BTFR is currently untrustworthy as a test of CDM.Comment: 5 pages, 2 figures; minor revisions to match published versio
Cutting Ties with Pro-Ana: A Narrative Inquiry Concerning the Experiences of Pro-Ana Disengagement from Six Former Site Users.
Websites advocating the benefits of eating disorders (“Pro-Ana”) tend to reinforce and maintain restrictive eating and purging behaviors. Yet remarkably, no study has explored individual accounts of disengagement from these sites and the associated meanings. Using narrative inquiry, this study sought to address this gap. From the interviews of six women, two overarching storylines emerged. The first closely tied disengagement to recovery with varying positions of personal agency claimed: this ranged from enforced and unwelcomed breaks that ignited change, to a personal choice that became viable through the development of alternative social and personal identities. A strong counternarrative to “disengagement as recovery” also emerged. Here, disengagement from Pro-Ana was storied alongside a need to retain an ED lifestyle. With “recovery” being just one reason for withdrawal from Pro-Ana sites, clinicians must remain curious about the meanings individuals ascribe to this act, without assuming it represents a step toward recovery.Peer reviewedFinal Accepted Versio
Resolving the virial discrepancy in clusters of galaxies with modified Newtonian dynamics
A sample of 197 X-ray emitting clusters of galaxies is considered in the
context of Milgrom's modified Newtonian dynamics (MOND). It is shown that the
gas mass, extrapolated via an assumed model to a fixed radius of 3 Mpc,
is correlated with the gas temperature as predicted by MOND (). The observed temperatures are generally consistent with the inferred
mass of hot gas; no substantial quantity of additional unseen matter is
required in the context of MOND. However, modified dynamics cannot resolve the
strong lensing discrepancy in those clusters where this phenomenon occurs. The
prediction is that additional baryonic matter may be detected in the central
regions of rich clusters.Comment: Submitted to A&A, 4 pages, 3 figures, A&A macro
Efficient slow-light coupling in a photonic crystal waveguide without transition region
We consider the coupling into a slow mode that appears near an inflection point in the band structure of a photonic crystal waveguide. Remarkably, the coupling into this slow mode, which has a group index n(g) > 1000, can be essentially perfect without any transition region. We show that this efficient coupling occurs thanks to an evanescent mode in the slow medium, which has appreciable amplitude and helps satisfy the boundary conditions but does not transport any energy. (C) 2008 Optical Society of AmericaPublisher PDFPeer reviewe
Preliminary measurements of aircraft airframe noise with the NASA CV-990 aircraft
Flight tests were conducted in a CV-990 jet transport with engines at idle power to investigate aircraft airframe noise. Test results showed that airframe noise was measured for the aircraft in the landing configuration. The results agreed well with the expected variation with the fifth power of velocity. For the aircraft in the clean configuraton, it was concluded that airframe noise was measured only at higher airspeeds with engine idle noise present at lower speeds. The data show that landing gear and flaps make a significant contribution to airframe noise
Indefinite Causal Order in a Quantum Switch
In quantum mechanics events can happen in no definite causal order: in
practice this can be verified by measuring a causal witness, in the same way
that an entanglement witness verifies entanglement. Indefinite causal order can
be observed in a quantum switch, where two operations act in a quantum
superposition of the two possible orders. Here we realise a photonic quantum
switch, where polarisation coherently controls the order of two operations,
and , on the transverse spatial mode of the photons. Our
setup avoids the limitations of earlier implementations: the operations cannot
be distinguished by spatial or temporal position. We show that our quantum
switch has no definite causal order, by constructing a causal witness and
measuring its value to be 18 standard deviations beyond the definite-order
bound
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