11,857 research outputs found
Semi-Phenomenological Analysis of Dynamics of Nonlinear Excitations in One-Dimensional Electron-Phonon System
The structure of moving nonlinear excitations in one-dimensional
electron-phonon systems is studied semi-phenomenologically by using an
effective action in which the width of the nonlinear excitation is treated as a
dynamical variable. The effective action can be derived from Su, Schrieffer and
Heeger's model or its continuum version proposed by Takayama, Lin-Liu and Maki
with an assumption that the nonlinear excitation moves uniformly without any
deformation except the change of its width. The form of the action is
essentially the same as that discussed by Bishop and coworkers in studying the
dynamics of the soliton in polyacetylene, though some details are different.
For the moving excitation with a velocity , the width is determined by
minimizing the effective action. A requirement that there must be a minimum in
the action as a function of its width provides a maximum velocity. The velocity
dependence of the width and energy can be determined. The motions of a soliton
in p olyacetylene and an acoustic polaron in polydiacetylene are studied within
this formulation. The obtained results are in good agreement with those of
numerical simulations.Comment: 19 pages, LaTeX, 7 Postscript figures, to be published in J. Phys.
Soc. Jpn. vol.65 (1996) No.
AzTEC 1.1 mm Observations of the MBM12 Molecular Cloud
We present 1.1 mm observations of the dust continuum emission from the MBM12
high-latitude molecular cloud observed with the Astronomical Thermal Emission
Camera (AzTEC) mounted on the James Clerk Maxwell Telescope on Mauna Kea,
Hawaii. We surveyed a 6.34 deg centered on MBM12, making this the largest
area that has ever been surveyed in this region with submillimeter and
millimeter telescopes. Eight secure individual sources were detected with a
signal-to-noise ratio of over 4.4. These eight AzTEC sources can be considered
to be real astronomical objects compared to the other candidates based on
calculations of the false detection rate. The distribution of the detected 1.1
mm sources or compact 1.1 mm peaks is spatially anti-correlated with that of
the 100 micronm emission and the CO emission. We detected the 1.1 mm
dust continuum emitting sources associated with two classical T Tauri stars,
LkHalpha262 and LkHalpha264. Observations of spectral energy distributions
(SEDs) indicate that LkHalpha262 is likely to be Class II (pre-main-sequence
star), but there are also indications that it could be a late Class I
(protostar). A flared disk and a bipolar cavity in the models of Class I
sources lead to more complicated SEDs. From the present AzTEC observations of
the MBM12 region, it appears that other sources detected with AzTEC are likely
to be extragalactic and located behind MBM12. Some of these have radio
counterparts and their star formation rates are derived from a fit of the SEDs
to the photometric evolution of galaxies in which the effects of a dusty
interstellar medium have been included.Comment: 8 pages, 6 figures, The Astrophysical Journal, in pres
On verbal agreement variation in European Portuguese: syntactic conditions for the 3SG/3PL alternation
In this paper we scrutinize a case of concord variation in European Portuguese (EP)
concerning third plural vs. third singular verbal agreement in the co-presence of
an overt plural argument, which in the standard variety agrees with the in! ected
verb. " e paper is focused on the linguistic factors that correlate with singular
concord in this context. Going beyond previous proposals that emphasize the correlation
between agreement variation and particular morphological and phonological
factors, it is shown that the incidence of non-standard singulars in EP may
be straightforwardly explained within a syntactic account. " e empirical basis for
this investigation is CORDIAL-SIN, a dialect corpus of EP (600,000 words). " e
evidence from this corpus leads us to discuss and reconsider the role that di# erent
linguistic factors play in the manifestation of non-standard singulars. It is shown
that this case of third singular agreement occurs in the investigated EP varieties in
correlation with particular syntactic conditions, mainly in unaccusative-like con-
cation of (null) expletives.info:eu-repo/semantics/publishedVersio
Kondo Effect of a Magnetic Ion Vibrating in a Harmonic Potential
To discuss Kondo effects of a magnetic ion vibrating in the sea of conduction
electrons, a generalized Anderson model is derived. The model includes a new
channel of hybridization associated with phonon emission or absorption. In the
simplest case of the localized electron orbital with the s-wave symmetry,
hybridization with p-waves becomes possible. Interesting interplay among the
conventional s-wave Kondo effect and the p-wave one and the Yu-Anderson type
Kondo effect is found and the ground state phase diagram is determined by using
the numerical renormalization group method. Two different types of stable fixed
points are identified and the two-channel Kondo fixed points are generically
realized on the boundary.Comment: 15 pages, 17 figures, J. Phys. Soc. Jpn. 80 (2011) No.6 to be
publishe
On the Nonabelian Aharonov Bohm Scattering of Spinless Particles
The Aharonov Bohm scattering for spinless, isospin 1/2, particles interacting
through a nonabelian Chern-Simons field is studied. Starting from the
relativistic quantum field theory and using a Coulomb gauge formulation, the
one loop renormalization program is implemented. Through the introduction of an
intermediary cutoff, separating the regions of high and low integration
momentum, the nonrelativistic limit is derived. The next to leading
relativistic approximation is also determined. In this approach quantum field
theory vacuum polarization effects are automatically incorporated.Comment: 20 pages, 8 figures, revtex. Misspelled reference corrected and new
references adde
Deep 1.1 mm-wavelength imaging of the GOODS-S field by AzTEC/ASTE - I. Source catalogue and number counts
[Abridged] We present the first results from a 1.1 mm confusion-limited map
of the GOODS-S field taken with AzTEC on the ASTE telescope. We imaged a 270
sq. arcmin field to a 1\sigma depth of 0.48 - 0.73 mJy/beam, making this one of
the deepest blank-field surveys at mm-wavelengths ever achieved. Although our
GOODS-S map is extremely confused, we demonstrate that our source
identification and number counts analyses are robust, and the techniques
discussed in this paper are relevant for other deeply confused surveys. We find
a total of 41 dusty starburst galaxies with S/N >= 3.5 within this uniformly
covered region, where only two are expected to be false detections. We derive
the 1.1mm number counts from this field using both a "P(d)" analysis and a
semi-Bayesian technique, and find that both methods give consistent results.
Our data are well-fit by a Schechter function model with (S', N(3mJy), \alpha)
= (1.30+0.19 mJy, 160+27 (mJy/deg^2)^(-1), -2.0). Given the depth of this
survey, we put the first tight constraints on the 1.1 mm number counts at
S(1.1mm) = 0.5 mJy, and we find evidence that the faint-end of the number
counts at S(850\mu m) < 2.0 mJy from various SCUBA surveys towards lensing
clusters are biased high. In contrast to the 870 \mu m survey of this field
with the LABOCA camera, we find no apparent under-density of sources compared
to previous surveys at 1.1 mm. Additionally, we find a significant number of
SMGs not identified in the LABOCA catalogue. We find that in contrast to
observations at wavelengths < 500 \mu m, MIPS 24 \mu m sources do not resolve
the total energy density in the cosmic infrared background at 1.1 mm,
demonstrating that a population of z > 3 dust-obscured galaxies that are
unaccounted for at these shorter wavelengths potentially contribute to a large
fraction (~2/3) of the infrared background at 1.1 mm.Comment: 21 pages, 9 figures. Accepted to MNRAS
Cellular responses of Candida albicans to phagocytosis and the extracellular activities of neutrophils are critical to counteract carbohydrate starvation, oxidative and nitrosative stress
Acknowledgments We thank Alexander Johnson (yhb1D/D), Karl Kuchler (sodD/D mutants), Janet Quinn (hog1D/D, hog1/cap1D/D, trx1D/D) and Peter Staib (ssu1D/D) for providing mutant strains. We acknowledge helpful discussions with our colleagues from the Microbial Pathogenicity Mechanisms Department, Fungal Septomics and the Microbial Biochemistry and Physiology Research Group at the Hans Kno¨ll Institute (HKI), specially Ilse D. Jacobsen, Duncan Wilson, Sascha Brunke, Lydia Kasper, Franziska Gerwien, Sea´na Duggan, Katrin Haupt, Kerstin Hu¨nniger, and Matthias Brock, as well as from our partners in the FINSysB Network. Author Contributions Conceived and designed the experiments: PM HW IMB AJPB OK BH. Performed the experiments: PM CD HW. Analyzed the data: PM HW IMB AJPB OK BH. Wrote the paper: PM HW OK AJPB BH.Peer reviewedPublisher PD
Phosphorylated c-Src in the nucleus is associated with improved patient outcome in ER-positive breast cancer
Elevated c-Src protein expression has been shown in breast cancer and <i>in vitro</i> evidence suggests a role in endocrine resistance. To investigate whether c-Src is involved in endocrine resistance, we examined the expression of both total and activated c-Src in human breast cancer specimens from a cohort of oestrogen receptor (ER)-positive tamoxifen-treated breast cancer patients. Tissue microarray technology was employed to analyse 262 tumour specimens taken before tamoxifen treatment. Immunohistochemistry using total c-Src and activated c-Src antibodies was performed. Kaplan–Meier survival curves were constructed and log-rank test were performed. High level of nuclear activated Src was significantly associated with improved overall survival (<i>P</i>=0.047) and lower recurrence rates on tamoxifen (<i>P</i>=0.02). Improved patient outcome was only seen with activated Src in the nucleus. Nuclear activated Src expression was significantly associated with node-negative disease and a lower NPI (<i>P</i><0.05). On subgroup analysis, only ER-positive/progesterone receptor (PgR)-positive tumours were associated with improved survival (<i>P</i>=0.004). This shows that c-Src activity is increased in breast cancer and that activated Src within the nucleus of ER-positive tumours predicts an improved outcome. In ER/PgR-positive disease, activated Src kinase does not appear to be involved in <i>de novo</i> endocrine resistance. Further study is required in ER-negative breast cancer as this may represent a cohort in which it is associated with poor outcome
Multi‐dimensional biodiversity hotspots and the future of taxonomic, ecological and phylogenetic diversity: A case study of North American rodents
AimWe investigate geographic patterns across taxonomic, ecological and phylogenetic diversity to test for spatial (in)congruency and identify aggregate diversity hotspots in relationship to present land use and future climate. Simulating extinctions of imperilled species, we demonstrate where losses across diversity dimensions and geography are predicted.LocationNorth America.Time periodPresent day, future.Major taxa studiedRodentia.MethodsUsing geographic range maps for rodent species, we quantified spatial patterns for 11 dimensions of diversity: taxonomic (species, range weighted), ecological (body size, diet and habitat), phylogenetic (mean, variance, and nearest‐neighbour patristic distances, phylogenetic distance and genus‐to‐species ratio) and phyloendemism. We tested for correlations across dimensions and used spatial residual analyses to illustrate regions of pronounced diversity. We aggregated diversity hotspots in relationship to predictions of land‐use and climate change and recalculated metrics following extinctions of IUCN‐listed imperilled species.ResultsTopographically complex western North America hosts high diversity across multiple dimensions: phyloendemism and ecological diversity exceed predictions based on taxonomic richness, and phylogenetic variance patterns indicate steep gradients in phylogenetic turnover. An aggregate diversity hotspot emerges in the west, whereas spatial incongruence exists across diversity dimensions at the continental scale. Notably, phylogenetic metrics are uncorrelated with ecological diversity. Diversity hotspots overlap with land‐use and climate change, and extinctions predicted by IUCN status are unevenly distributed across space, phylogeny or ecological groups.Main conclusionsComparison of taxonomic, ecological and phylogenetic diversity patterns for North American rodents clearly shows the multifaceted nature of biodiversity. Testing for geographic patterns and (in)congruency across dimensions of diversity facilitates investigation into underlying ecological and evolutionary processes. The geographic scope of this analysis suggests that several explicit regional challenges face North American rodent fauna in the future. Simultaneous consideration of multi‐dimensional biodiversity allows us to assess what critical functions or evolutionary history we might lose with future extinctions and maximize the potential of our conservation efforts.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154236/1/geb13050.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154236/2/geb13050_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154236/3/geb13050-sup-0001-Supinfo1.pd
Behavioural stress responses predict environmental perception in European sea bass (Dicentrarchus labrax)
Individual variation in the response to environmental challenges depends partly on innate reaction norms, partly on experience-based cognitive/emotional evaluations that individuals make of the situation. The goal of this study was to investigate whether pre-existing differences in behaviour predict the outcome of such assessment of environmental cues, using a conditioned place preference/avoidance (CPP/CPA) paradigm. A comparative vertebrate model (European sea bass, Dicentrarchus labrax) was used, and ninety juvenile individuals were initially screened for behavioural reactivity using a net restraining test. Thereafter each individual was tested in a choice tank using net chasing as aversive stimulus or exposure to familiar conspecifics as appetitive stimulus in the preferred or non preferred side respectively (called hereafter stimulation side). Locomotor behaviour (i.e. time spent, distance travelled and swimming speed in each tank side) of each individual was recorded and analysed with video software. The results showed that fish which were previously exposed to appetitive stimulus increased significantly the time spent on the stimulation side, while aversive stimulus led to a strong decrease in time spent on the stimulation side. Moreover, this study showed clearly that proactive fish were characterised by a stronger preference for the social stimulus and when placed in a putative aversive environment showed a lower physiological stress responses than reactive fish. In conclusion, this study showed for the first time in sea bass, that the CPP/CPA paradigm can be used to assess the valence (positive vs. negative) that fish attribute to different stimuli and that individual behavioural traits is predictive of how stimuli are perceived and thus of the magnitude of preference or avoidance behaviour.European Commission [265957]; Portuguese Fundacao para a Ciencia e Tecnologia (FCT) [FRH/BPD/72952/2010]; FCT [SFRH/BD/80029/2011
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