1,056 research outputs found
The microscopic nature of localization in the quantum Hall effect
The quantum Hall effect arises from the interplay between localized and
extended states that form when electrons, confined to two dimensions, are
subject to a perpendicular magnetic field. The effect involves exact
quantization of all the electronic transport properties due to particle
localization. In the conventional theory of the quantum Hall effect,
strong-field localization is associated with a single-particle drift motion of
electrons along contours of constant disorder potential. Transport experiments
that probe the extended states in the transition regions between quantum Hall
phases have been used to test both the theory and its implications for quantum
Hall phase transitions. Although several experiments on highly disordered
samples have affirmed the validity of the single-particle picture, other
experiments and some recent theories have found deviations from the predicted
universal behaviour. Here we use a scanning single-electron transistor to probe
the individual localized states, which we find to be strikingly different from
the predictions of single-particle theory. The states are mainly determined by
Coulomb interactions, and appear only when quantization of kinetic energy
limits the screening ability of electrons. We conclude that the quantum Hall
effect has a greater diversity of regimes and phase transitions than predicted
by the single-particle framework. Our experiments suggest a unified picture of
localization in which the single-particle model is valid only in the limit of
strong disorder
On Induced Gravity in 2-d Topological Theories
We study 2-d gauge theories with the objective to understand, also
at the quantum level, the emergence of induced gravity. The wave functionals -
representing the eigenstates of a vanishing flat potential - are obtained in
the representation. The composition of the space they describe is then
analyzed: the state corresponding to the singlet representation of the gauge
group describes a topological universe. For other representations a metric
which is invariant under the residual gauge group is induced, apart from
possible topological obstructions. Being inherited from the group metric it is
rather rigid.Comment: 38, tex, 160/93/e
Multivisceral intestinal transplantation: Surgical pathology
We report the diagnostic surgical pathology of two children who underwent multivisceral abdominal transplantation and survived for 1 month and 6 months. There is little relevant literature, and diagnostic criteria for the various clinical possibilities are not established; this is made more complicated by the simultaneous occurrence of more than one process. We based our interpretations on conventional histology, augmented with immunohistology, including HLA staining that distinguished graft from host cells in situ. In some instances functional analysis of T cells propagated from the same biopsies was available and was used to corroborate morphological interpretations. A wide spectrum of changes was encountered. Graft-versus-host disease, a prime concern before surgery, was not seen. Rejection was severe in 1 patient, not present in the other, and both had evidence of lymphoproliferative disease, which was related to Epstein-Barr virus. Bacterial translocation through the gut wall was also a feature in both children. This paper documents and illustrates the various diagnostic possibilities.. © 1989 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted
Genetic polymorphisms of phase I metabolizing enzyme genes, their interaction with lifetime grilled and smoked meat intake, and breast cancer incidence
To examine associations between 22 CYP single nucleotide polymorphisms (SNPs) and breast cancer incidence and their interactions with grilled–smoked meat intake, a source of polycyclic aromatic hydrocarbons
Modular symbols in Iwasawa theory
This survey paper is focused on a connection between the geometry of
and the arithmetic of over global fields,
for integers . For over , there is an explicit
conjecture of the third author relating the geometry of modular curves and the
arithmetic of cyclotomic fields, and it is proven in many instances by the work
of the first two authors. The paper is divided into three parts: in the first,
we explain the conjecture of the third author and the main result of the first
two authors on it. In the second, we explain an analogous conjecture and result
for over . In the third, we pose questions for general
over the rationals, imaginary quadratic fields, and global function fields.Comment: 43 page
Environmental Tobacco Smoke Exposure and Survival Following Breast Cancer
Environmental tobacco smoke (ETS) exposure is hypothesized to influence survival after breast cancer, but few studies have examined this association
Global behavior of the height/seasonal structure of tides between 40 deg and 60 deg latitude
The radars utilized are meteor (2), medium frequency (2) and the new low frequency (1) systems: analysis techniques were exhaustively studied internally and comparatively and are not thought to affect the results. Emphasis is placed upon the new height-time contours of 24-, 12-h tidal amplitudes and phases, which best display height and seasonal structures; where possible high resolution (10 d) is used (Saskatoon), but all stations provide monthly mean resolution. At these latitudes the diurnal tide is generally smaller than the semidiurnal, and displays more variability. However, there is a tendency for vertical wavelengths and amplitudes to be larger during summer months. On occasions in winter and fall, wavelengths may be less than 50 km. The dominant semidiurnal tide shows significant regular season structure; wavelengths are generally small (about 50 km) in winter, large in summer (equal to or greater than 100 km), and these states are separated by rapid equinoctial transitions. There is some evidence for less regularity toward 40 deg. Coupling with mean winds is apparent. Data from earlier ATMAP campaigns are mentioned, and reasons for their inadequacies presented
Multipolar Interactions in the Anderson Lattice with Orbital Degeneracy
Microscopic investigation is performed for intersite multipolar interactions
in the orbitally degenerate Anderson lattice, with CeB taken as an
exemplary target. In addition to the intermediate state,
Hund's-rule ground states are included as intermediate states for the
interactions. The conduction-band states are taken as plane waves and the
hybridization as spherically symmetric. The spatial dependences of multipolar
interactions are given by the relative weight of partial wave components along
the pair of sites. It is clarified how the the anisotropy arises in the
interactions depending on the orbital degeneracy and the spatial configuration.
The stability of the antiferro-quadrupole order in the phase II of
CeB is consistent with our model. Moreover, the pseudo-dipole interactions
follow a tendency required by the phenomenological model for the phase III.Comment: 30 pages, 4 figure
Modification of the association between recreational physical activity and survival after breast cancer by promoter methylation in breast cancer-related genes
Background: Mechanisms underlying the inverse association between physical activity and survival after breast cancer are unresolved, but DNA methylation may play a role. We hypothesized that promoter methylation of breast cancer-related genes, as well as global methylation, may modify the association between prediagnostic recreational physical activity (RPA) and breast cancer mortality.
Methods: Using a population-based sample of 1254 women diagnosed with first primary breast cancer, we examined modification of the RPA-mortality association by gene-specific promoter methylation and global methylation. Average lifetime RPA was assessed from menarche to diagnosis through structured in-home interviews. Promoter methylation of 13 breast cancer-related genes was evaluated in archived tumor by methylation-specific polymerase chain reaction and MethyLight assay. Global methylation in white blood cell DNA was determined at long interspersed nucleotide element 1 and by the luminometric methylation assay. After approximately 15 years of follow-up, 486 patients had died, and 186 of the deaths were breast cancer-related. We used Cox proportional hazards regression to estimate HRs and 95% CIs as well as likelihood ratio tests to assess multiplicative interactions.
Results: All-cause mortality was lower only among physically active women with methylated promoter of APC (HR 0.60, 95% CI 0.40–0.80), CCND2 (HR 0.56, 95% CI 0.32–0.99), HIN (HR 0.55, 95% CI 0.38–0.80), and TWIST1 (HR 0.28, 95% CI 0.14–0.56) in tumors, but not among those with unmethylated tumors (significant interaction p < 0.05). We found no interaction between RPA and global methylation.
Conclusions: The improved survival after breast cancer that is associated with RPA may be more pronounced in women with promoter tumor methylation in biologically plausible genes
The association of diabetes with breast cancer incidence and mortality in the Long Island Breast Cancer Study Project
Diabetes has been associated with increased risk of breast cancer in a number of epidemiologic studies, but its effects on survival among women diagnosed with breast cancer have been examined less frequently. Importantly, prior investigations have rarely considered the influence of factors associated with diabetes such as obesity, age at diabetes diagnosis, duration of diabetes, or diabetes treatments
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