1,407 research outputs found
Testing the Hubble Law with the IRAS 1.2 Jy Redshift Survey
We test and reject the claim of Segal et al. (1993) that the correlation of
redshifts and flux densities in a complete sample of IRAS galaxies favors a
quadratic redshift-distance relation over the linear Hubble law. This is done,
in effect, by treating the entire galaxy luminosity function as derived from
the 60 micron 1.2 Jy IRAS redshift survey of Fisher et al. (1995) as a distance
indicator; equivalently, we compare the flux density distribution of galaxies
as a function of redshift with predictions under different redshift-distance
cosmologies, under the assumption of a universal luminosity function. This
method does not assume a uniform distribution of galaxies in space. We find
that this test has rather weak discriminatory power, as argued by Petrosian
(1993), and the differences between models are not as stark as one might expect
a priori. Even so, we find that the Hubble law is indeed more strongly
supported by the analysis than is the quadratic redshift-distance relation. We
identify a bias in the the Segal et al. determination of the luminosity
function, which could lead one to mistakenly favor the quadratic
redshift-distance law. We also present several complementary analyses of the
density field of the sample; the galaxy density field is found to be close to
homogeneous on large scales if the Hubble law is assumed, while this is not the
case with the quadratic redshift-distance relation.Comment: 27 pages Latex (w/figures), ApJ, in press. Uses AAS macros,
postscript also available at
http://www.astro.princeton.edu/~library/preprints/pop682.ps.g
On the Fixed-Point Structure of Scalar Fields
In a recent Letter (K.Halpern and K.Huang, Phys. Rev. Lett. 74 (1995) 3526),
certain properties of the Local Potential Approximation (LPA) to the Wilson
renormalization group were uncovered, which led the authors to conclude that
dimensional scalar field theories endowed with {\sl non-polynomial}
interactions allow for a continuum of renormalization group fixed points, and
that around the Gaussian fixed point, asymptotically free interactions exist.
If true, this could herald very important new physics, particularly for the
Higgs sector of the Standard Model. Continuing work in support of these ideas,
has motivated us to point out that we previously studied the same properties
and showed that they lead to very different conclusions. Indeed, in as much as
the statements in hep-th/9406199 are correct, they point to some deep and
beautiful facts about the LPA and its generalisations, but however no new
physics.Comment: Typos corrected. A Comment - to be published in Phys. Rev. Lett. 1
page, 1 eps figure, uses LaTeX, RevTex and eps
Possible effect of collective modes in zero magnetic field transport in an electron-hole bilayer
We report single layer resistivities of 2-dimensional electron and hole gases
in an electron-hole bilayer with a 10nm barrier. In a regime where the
interlayer interaction is stronger than the intralayer interaction, we find
that an insulating state () emerges at or
lower, when both the layers are simultaneously present. This happens deep in
the metallic" regime, even in layers with , thus making
conventional mechanisms of localisation due to disorder improbable. We suggest
that this insulating state may be due to a charge density wave phase, as has
been expected in electron-hole bilayers from the Singwi-Tosi-Land-Sj\"olander
approximation based calculations of L. Liu {\it et al} [{\em Phys. Rev. B},
{\bf 53}, 7923 (1996)]. Our results are also in qualitative agreement with
recent Path-Integral-Monte-Carlo simulations of a two component plasma in the
low temperature regime [ P. Ludwig {\it et al}. {\em Contrib. Plasma Physics}
{\bf 47}, No. 4-5, 335 (2007)]Comment: 5 pages + 3 EPS figures (replaced with published version
Subleading critical exponents from the renormalisation group
We study exact renormalisation group equations for the 3d Ising universality
class. At the Wilson-Fisher fixed point, symmetric and antisymmetric
correction-to-scaling exponents are computed with high accuracy for an
optimised cutoff to leading order in the derivative expansion. Further results
are derived for other cutoffs including smooth, sharp and background field
cutoffs. An estimate for higher order corrections is given as well. We
establish that the leading antisymmetric corrections to scaling are strongly
subleading compared to the leading symmetric ones.Comment: 10 pages, 5 figure
Parallel quantized charge pumping
Two quantized charge pumps are operated in parallel. The total current
generated is shown to be far more accurate than the current produced with just
one pump operating at a higher frequency. With the application of a
perpendicular magnetic field the accuracy of quantization is shown to be 20
ppm for a current of pA. The scheme for parallel pumping presented in
this work has applications in quantum information processing, the generation of
single photons in pairs and bunches, neural networking and the development of a
quantum standard for electrical current. All these applications will benefit
greatly from the increase in output current without the characteristic decrease
in accuracy as a result of high-frequency operation
The buddy bench and beyond: Exploring complexity-informed approaches to wellbeing education
Enhancing wellbeing in educational settings is a challenging endeavour as wellbeing education is inherently complex. This interdisciplinary conceptual paper aims to bridge the gap between psychological interventions and educational contexts by adopting a complexity lens to consider the puzzle of wellbeing in educational settings. We draw on the fields of positive psychology, educational theory, complexity thinking, and indigenous worldviews to conceptualise wellbeing education and illustrate the need to weave approaches together. Embracing a complexity lens, we offer ways of prompting emergent wellbeing change: incorporating diverse perspectives, trialling nudges, and attending to interactions across the system. We argue that complexity-informed approaches to wellbeing education have the potential to create emergent change in and across complex educational systems
Structure of the ovaries of the Nimba otter shrew, Micropotamogale lamottei, and the Madagascar hedgehog tenrec, Echinops telfairi
The otter shrews are members of the subfamily Potamogalinae within the family Tenrecidae. No description of the ovaries of any member of this subfamily has been published previously. The lesser hedgehog tenrec, Echinops telfairi, is a member of the subfamily Tenrecinae of the same family and, although its ovaries have not been described, other members of this subfamily have been shown to have ovaries with non-antral follicles. Examination of these two species illustrated that non-antral follicles were characteristic of the ovaries of both species, as was clefting and lobulation of the ovaries. Juvenile otter shrews range from those with only small follicles in the cortex to those with 300- to 400-mu m follicles similar to those seen in non-pregnant and pregnant adults. As in other species, most of the growth of the oocyte occurred when follicles had one to two layers of granulosa cells. When larger follicles became atretic in the Nimba otter shrew, hypertrophy of the theca interna produced nodules of glandular interstitial tissue. In the tenrec, the hypertrophying theca interna cells in most large follicles appeared to undergo degeneration. Both species had some follicular fluid in the intercellular spaces between the more peripheral granulosa cells. It is suggested that this fluid could aid in separation of the cumulus from the remaining granulosa at ovulation. The protruding follicles in lobules and absence of a tunica albuginea might also facilitate ovulation of non-antral follicles. Ovaries with a thin-absent tunica albuginea and follicles with small-absent antra are widespread within both the Eulipotyphla and in the Afrosoricida, suggesting that such features may represent a primitive condition in ovarian development. Lobulated and deeply crypted ovaries are found in both groups but are not as common in the Eulipotyphla making inclusion of this feature as primitive more speculative. Copyright (C) 2005 S. Karger AG, Basel
Increasing stair climbing in a train station: effects of contextual variables and visibility
Accumulation of physical activity during daily living is a current public health target that is
influenced by the layout of the built environment. This study reports how the layout of the
environment may influence responsiveness to an intervention. Pedestrian choices (n = 41 717)
between stairs and the adjacent escalators were monitored for seven weeks in a train station
(Birmingham, UK). After a 3.5 week baseline period, a stair riser banner intervention to increase
stair climbing was installed on two staircases adjacent to escalators and monitoring continued for
a further 3.5 weeks. Logistic regression analyses revealed that the visibility of the intervention,
defined as the area of visibility in the horizontal plane opposite to the direction of travel (termed
the isovist) had a major effect on success of the intervention. Only the largest isovist produced
an increase in stair climbing (isovist=77.6 m2, OR = 1.10, CIs 1.02-1.19; isovist=40.7 m2, OR =
0.98, CIs 0.91-1.06; isovist=53.2 m2, OR = 1.00, CIs 0.95-1.06). Additionally, stair climbing was
more common during the morning rush hour (OR = 1.56, CIs 1.80-2.59) and at higher levels of
pedestrian traffic volume (OR = 1.92, CIs 1.68-2.21). The layout of the intervention site can
influence responsiveness to point-of-choice interventions. Changes to the design of train stations
may maximize the choice of the stairs at the expense of the escalator by pedestrians leaving the
station
Crossover scaling from classical to nonclassical critical behavior
We study the crossover between classical and nonclassical critical behaviors.
The critical crossover limit is driven by the Ginzburg number G. The
corresponding scaling functions are universal with respect to any possible
microscopic mechanism which can vary G, such as changing the range or the
strength of the interactions. The critical crossover describes the unique flow
from the unstable Gaussian to the stable nonclassical fixed point. The scaling
functions are related to the continuum renormalization-group functions. We show
these features explicitly in the large-N limit of the O(N) phi^4 model. We also
show that the effective susceptibility exponent is nonmonotonic in the
low-temperature phase of the three-dimensional Ising model.Comment: 5 pages, final version to appear in Phys. Rev.
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