11,511 research outputs found
An extreme ultraviolet photoemission study Final report
Photoelectric emission properties of iron, copper, nickel, aluminum, and molybdenu
Recommended from our members
Addressing School Dropout in Texas: A Summary for Administrators and Policymakers of "Dropout Prevention: A Practice Guide"
This booklet summarizes the information from: Dropout Prevention: A Practice Guide, available on the Institute of Education Sciences web site at http://ies.ed.gov/ncee/wwc.Educatio
Productive tensions - engaging geography students in participatory action research with communities
ArticleCopyright © 2013 copyright Taylor & Francis.This study discusses the benefits and challenges of an undergraduate module on participatory geographies, involving students in co-producing research with community partners. The module challenges the knowledge production model predominant in Geography curricula. We argue that it develops students' skills and understanding through engaging them intellectually, socially and emotionally outside the university. As a student, two community partners and a professor, we offer our perspectives on the opportunities and conflicts that arose. We do not gloss over tensions in achieving the module's diverse aims, but suggest that these are productive for teaching, learning, research and the needs of community organizations
The Origin of Black Hole Entropy in String Theory
I review some recent work in which the quantum states of string theory which
are associated with certain black holes have been identified and counted. For
large black holes, the number of states turns out to be precisely the
exponential of the Bekenstein-Hawking entropy. This provides a statistical
origin for black hole thermodynamics in the context of a potential quantum
theory of gravity.Comment: 18 pages (To appear in the proceedings of the Pacific Conference on
Gravitation and Cosmology, Seoul, Korea, February 1-6, 1996.
Relativistic corrections to the Pionium Lifetime
Next to leading order contributions to the pionium lifetime are considered
within non-relativistic effective field theory. A more precise determination of
the coupling constants is then needed in order to be consistent with the
relativistic pion-pion scattering amplitude which can be obtained from chiral
perturbation theory. The relativistic correction is found to be 4.1% and
corresponds simply to a more accurate value for the non-relativistic decay
momentum.Comment: 5 pages, Latex. Includes corrections based on a more precise matching
to the pion-pion scattering amplitude from chiral perturbation theor
Topological Entropy of Braids on the Torus
A fast method is presented for computing the topological entropy of braids on
the torus. This work is motivated by the need to analyze large braids when
studying two-dimensional flows via the braiding of a large number of particle
trajectories. Our approach is a generalization of Moussafir's technique for
braids on the sphere. Previous methods for computing topological entropies
include the Bestvina--Handel train-track algorithm and matrix representations
of the braid group. However, the Bestvina--Handel algorithm quickly becomes
computationally intractable for large braid words, and matrix methods give only
lower bounds, which are often poor for large braids. Our method is
computationally fast and appears to give exponential convergence towards the
exact entropy. As an illustration we apply our approach to the braiding of both
periodic and aperiodic trajectories in the sine flow. The efficiency of the
method allows us to explore how much extra information about flow entropy is
encoded in the braid as the number of trajectories becomes large.Comment: 19 pages, 44 figures. SIAM journal styl
Gratitude while Drinking, Gratitude while Recovering
Background. For decades researchers have debated whether those diagnosed with alcohol use disorders can return to non-problematic drinking. Now, recovery researchers are measuring aspects of wellbeing in addition to aspects of pathology, producing surprising findings that have added to the debate. Recent studies show that some who continue to drink endorse high levels of psychosocial functioning. Objectives. Employ trait gratitude to answer the following questions: how do individuals who continue to drink but endorse high gratitude at follow-up differ from peers at baseline? Does trait gratitude correlate differently with demographic, psychosocial, and clinical factors for abstinent members of Alcoholics Anonymous (AA) versus drinking non-AAs? Methods. 275 individuals with alcohol dependence were assessed for trait gratitude at 2.5-3 year follow-up in a naturalistic, longitudinal study. Psychosocial and clinical indicators were assessed at baseline and follow-up. Results. Drinkers who endorsed high gratitude had higher socioeconomic status, greater levels of positive spirituality, more stable personality indicators, less addiction severity, fewer negative life events, and fewer psychiatric symptoms than their peers at baseline. For actively drinking non-AAs, trait gratitude correlated differently, and positively, with years of education, income, and purpose in life compared with sober AAs. For AA members, gratitude correlated positively with AA involvement and length of sobriety. Discussion. A subset of drinkers report doing relatively well despite meeting criteria for alcohol dependence. Trait gratitude correlated differently with other constructs for AAs versus non-AAs, indicating that gratitude for recovery might be contextually sensitive, operating differently within and without the structure of AA
Minimum Requirements for Detecting a Stochastic Gravitational Wave Background Using Pulsars
We assess the detectability of a nanohertz gravitational wave (GW) background
with respect to additive red and white noise in the timing of millisecond
pulsars. We develop detection criteria based on the cross-correlation function
summed over pulsar pairs in a pulsar timing array. The distribution of
correlation amplitudes is found to be non-Gaussian and highly skewed, which
significantly influences detection and false-alarm probabilities. When only
white noise and GWs contribute, our detection results are consistent with those
found by others. Red noise, however, drastically alters the results. We discuss
methods to meet the challenge of GW detection ("climbing mount significance")
by distinguishing between GW-dominated and red or white-noise limited regimes.
We characterize detection regimes by evaluating the number of millisecond
pulsars that must be monitored in a high-cadence, 5-year timing program for a
GW background spectrum with yr.
Unless a sample of 20 super-stable millisecond pulsars can be found --- those
with timing residuals from red-noise contributions ns
--- a much larger timing program on MSPs will be needed. For
other values of , the constraint is . Identification of suitable MSPs itself requires
an aggressive survey campaign followed by characterization of the level of spin
noise in the timing residuals of each object. The search and timing programs
will likely require substantial fractions of time on new array telescopes in
the southern hemisphere as well as on existing ones.Comment: Submitted to the Astrophysical Journa
Measurement of Critical Contact Angle in a Microgravity Space Experiment
Mathematical theory predicts that small changes in container shape or in contact angle can give rise to large shifts of liquid in a microgravity environment. This phenomenon was investigated in the Interface Configuration Experiment on board the USML-2 Space Shuttle flight. The experiment's "double proboscis" containers were designed to strike a balance between conflicting requirements of sizable volume of liquid shift (for ease of observation) and abruptness of the shift (for accurate determination of critical contact angle). The experimental results support the classical concept of macroscopic contact angle and demonstrate the role of hysteresis in impeding orientation toward equilibrium
- …