87 research outputs found
Charge Fractionalization on Quantum Hall Edges
We discuss the propagation and fractionalization of localized charges on the
edges of quantum Hall bars of variable widths, where interactions between the
edges give rise to Luttinger liquid behavior with a non-trivial interaction
parameter g. We focus in particular on the separation of an initial charge
pulse into a sharply defined front charge and a broader tail. The front pulse
describes an adiabatically dressed electron which carries a non-integer charge,
which is \sqrt{g} times the electron charge. We discuss how the presence of
this fractional charge can, in principle, be detected through measurements of
the noise in the current created by tunneling of electrons into the system. The
results are illustrated by numerical simulations of a simplified model of the
Hall bar.Comment: 15 page
Are there sharp fractional charges in Luttinger liquids?
We examine charge fractionalization by chiral separation in a one-dimensional
fermion system described by Luttinger liquid theory. The focus is on the
question of whether the fractional charges are quantum mechanically sharp, and
in the analysis we make a distinction between the global charge, which is
restricted by boundary conditions, and the local charge where a background
contribution is subtracted. We show, by way of examples, that fractional
charges of arbitrary values, all which are quantum mechanically sharp, can be
introduced by different initial conditions. Since the system is gapless,
excitations of arbitrary low frequency contribute to the fluctuations, it is
important to make a precise definition of sharp charges, and this we we do by
subtraction of the ground state contribution. We very briefly comment on the
relevance of our analysis for proposed experiments.Comment: One reference update
Equilibration and macroscopic quantum fluctuations in the Dicke model
We discuss the unitary quantum dynamics of the Dicke model (spin and
oscillator coupled). A suitable quasiprobabilty representing the quantum state
turns out to obey a Fokker-Planck equation, with drift terms representing the
underlying classical Hamiltonian flow and diffusion terms describing quantum
fluctuations. We show (by projecting the dynamics onto a co-moving Poincar\'e
section) how the interplay of deterministic drift and quantum diffusion
generates equilibration to the microcanonical density, under conditions of
global classical chaos. The pertinent photon statistics reveals macroscopic
quantum fluctuations.Comment: 12 pages, 5 figure
Unidentified transitions in one-photon intrashell dynamics in Rydberg atoms
One-photon intrashell transitions in strongly driven Li (n = 25) atoms are studied experimentally. Thedegeneracy of the n shell is lifted by orthogonal dc electric and magnetic fields, which also define the eccentricity of the initial coherent elliptic state. The transitions are driven by a radio frequency pulse linearly polarized parallel to the major axis of the ellipse. A small dc electric field component parallel to the magnetic field splits the one-photon resonance into two, and transitions in between are studied by state-selective field ionization. Unexpected lines in the ionization spectra relating to unknown transitions are found and discussed.Fil: PreclĂkovĂĄ, J.. University of Bergen; NoruegaFil: Waheed, A.. University of Bergen; NoruegaFil: Fregenal, Daniel Eduardo. Consejo Nacional de Investigaciones CientĂficas y TĂŠcnicas. Centro CientĂfico TecnolĂłgico Conicet - Patagonia Norte; Argentina. ComisiĂłn Nacional de EnergĂa AtĂłmica. Centro AtĂłmico Bariloche; ArgentinaFil: Frette, Ă.. University of Bergen; NoruegaFil: Hamre, B.. University of Bergen; NoruegaFil: Hjertaker, B.T.. University of Bergen; NoruegaFil: Horsdal, E.. University Aarhus; DinamarcaFil: Pilskog, I.. University of Bergen; NoruegaFil: Førre, M.. University of Bergen; Norueg
The Risk of Overall Mortality in Patients With Type 2 Diabetes Receiving Glipizide, Glyburide, or Glimepiride Monotherapy: A retrospective analysis
Genome-wide association study of school grades identifies genetic overlap between language ability, psychopathology and creativity
Cognitive functions of individuals with psychiatric disorders differ from that of the general population. Such cognitive differences often manifest early in life as differential school performance and have a strong genetic basis. Here we measured genetic predictors of school performance in 30,982 individuals in English, Danish and mathematics via a genome-wide association study (GWAS) and studied their relationship with risk for six major psychiatric disorders. When decomposing the school performance into math and language-specific performances, we observed phenotypically and genetically a strong negative correlation between math performance and risk for most psychiatric disorders. But language performance correlated positively with risk for certain disorders, especially schizophrenia, which we replicate in an independent sample (n = 4547). We also found that the genetic variants relating to increased risk for schizophrenia and better language performance are overrepresented in individuals involved in creative professions (n = 2953) compared to the general population (n = 164,622). The findings together suggest that language ability, creativity and psychopathology might stem from overlapping genetic roots.Peer reviewe
Gliclazide may have an antiapoptotic effect related to its antioxidant properties in human normal and cancer cells
Experimental and clinical studies suggest that gliclazide may protect pancreatic β-cells from apoptosis induced by an oxidative stress. However, the precise mechanism(s) of this action are not fully understood and requires further clarification. Therefore, using human normal and cancer cells we examined whether the anti-apoptotic effects of this sulfonylurea is due to its free radical scavenger properties. Hydrogen peroxide (H2O2) as a model trigger of oxidative stress was used to induce cell death. Our experiments were performed on human normal cell line (human umbilical vein endothelial cell line, HUVEC-c) and human cancer cell lines (human mammary gland cell line, Hs578T; human pancreatic duct epithelioid carcinoma cell line, PANC-1). To assess the effect of gliclazide the cells were pre-treated with the drug. The 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay was employed to measure the impact of gliclazide on cell viability. Generation of reactive oxygen species, mitochondrial membrane potential (âΨm), and intracellular Ca2+ concentration [Ca2+] were monitored. Furthermore, the morphological changes associated with apoptosis were determined using double staining with Hoechst 33258-propidium iodide (PI). Gliclazide protects the tested cells from H2O2-induced cell death most likely throughout the inhibition of ROS production. Moreover, the drug restored loss of ÎΨm and diminished intracellular [Ca2+] evoked by H2O2. Double staining with Hoechst 33258-PI revealed that pre-treatment with gliclazide diminished the number of apoptotic cells. Our findings indicate that gliclazide may protect both normal and cancer human cells against apoptosis induced by H2O2. It appears that the anti-apoptotic effect of the drug is most likely associated with reduction of oxidative stress
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