Electron correlations and single-particle physics in the Integer Quantum Hall Effect

The compressibility of a two-dimensional electron system with spin in a spatially correlated random potential and a quantizing magnetic field is investigated. Electron-electron interaction is treated with the Hartree-Fock method. Numerical results for the influences of interaction and disorder on the compressibility as a function of the particle density and the strength of the magnetic field are presented. Localization-delocalization transitions associated with highly compressible region in the energy spectrum are found at half-integer filling factors. Coulomb blockade effects are found near integer fillings in the regions of low compressibility. Results are compared with recent experiments.Comment: 4 pages, 2 figures, replaced with revised versio

Negative Application Conditions for Reconfigurable Place/Transition Systems

This paper introduces negative application conditions for reconfigurable place/transition nets. These are Petri nets together with a set of rules that allow changing the net and its marking dynamically. Negative application conditions are a control structure that prohibits the application of a rule if certain structures are already existent. We motivate the use of negative application conditions in a short example. Subsequently the underlying theory is sketched and the results – concerning parallelism, concurrency and confluence – are presented. Then we resume the example and explicitly discuss the main results and their usefulness within the example

Lead uptake in diverse plant families: A study applying X-ray absorption near edge spectroscopy

The chemical environment of lead in roots and leaves of plants from four different plant families and a lichen from a former lead mining site in the Eifel Mountains in Germany was determined by Pb L3-edge XANES measurements using solid reference compounds and also aqueous solutions of different ionic strength simulating the plant environment. Pb2+ ions in the plants were found to have two major coordinations, one with nine oxygen atoms in the first coordination shell similar to outer-sphere complexation and a second coordination with just three oxygen atoms similar to inner-sphere complexation. This can be interpreted assuming that lead is sorbed on the surface of cell walls depending on the concentration of lead in the soil solution. Pb L3-edge XANES spectra of dried and fresh plant samples are very similar because sorption does not change with removal of water but only because of the initial ionic strength. No bonding to biologically important groups (-S, - N) or precipitation (-PO4) was found. © 2013 American Chemical Society

Azbel-Hofstadter model on triangular lattice revisited

In the present paper, the mean of Lyapunov exponents for the Azbel-Hofstadter model on the triangular lattice is calculated. It is recently proposed that [Phys. Rev. Lett. {\bf 85}, 4920 (2000)], for the case of the square lattice, this quantity can be related to the logarithm of the partition function of the two dimensional Ising model and has a connection to the asymptotic bandwidth. We find that the correspondence of this quantity to the logarithm of the partition function of the two dimensional Ising model is not complete for the triangular lattice. Moreover, the detailed connection between this quantity and the asymptotic bandwidth is not valid. Thus the conclusions for the mean of Lyapunov exponents suggested previously depend on the lattice geometry.Comment: RevTeX, 4 page, no figur

Effect of ABCG2, OCT1, and ABCB1(MDR1) Gene Expression on Treatment-Free Remission in a EURO-SKI Subtrial

Introduction Tyrosine kinase inhibitors (TKIs) can safely be discontinued in chronic myeloid leukemia (CML) patients with sustained deep molecular response. ABCG2 (breast cancer resistance protein), OCT1 (organic cation transporter 1), and ABCB1 (multidrug resistance protein 1) gene products are known to play a crucial role in acquired pharmacogenetic TKI resistance. Their influence on treatment-free remission (TFR) has not yet been investigated. Materials and Methods RNA was isolated on the last day of TKI intake from peripheral blood leukocytes of 132 chronic phase CML patients who discontinued TKI treatment within the European Stop Tyrosine Kinase Inhibitor Study trial. Plasmid standards were designed including subgenic inserts of OCT1, ABCG2, and ABCB1 together with GUSB as reference gene. For expression analyses, quantitative real-time polymerase chain reaction was used. Multiple Cox regression analysis was performed. In addition, gene expression cutoffs for patient risk stratification were investigated. Results The TFR rate of 132 patients, 12 months after TKI discontinuation, was 54% (95% confidence interval [CI], 46%-62%). ABCG2 expression (‰) was retained as the only significant variable (P = .02; hazard ratio, 1.04; 95% CI, 1.01-1.07) in multiple Cox regression analysis. Only for the ABCG2 efflux transporter, a significant cutoff was found (P = .04). Patients with an ABCG2/GUSB transcript level >4.5‰ (n = 93) showed a 12-month TFR rate of 47% (95% CI, 37%-57%), whereas patients with low ABCG2 expression (≤4.5‰; n = 39) had a 12-month TFR rate of 72% (95% CI, 55%-82%). Conclusion In this study, we investigated the effect of pharmacogenetics in the context of a CML treatment discontinuation trial. The transcript levels of the efflux transporter ABCG2 predicted TFR after TKI discontinuation

Coral δ18O evidence for Pacific Ocean mediated decadal variability in Panamanian ITCZ rainfall back to the early 1700s

In Central America, seasonal and interannual shifts in the position of the Intertropical Convergence Zone (ITCZ) control the hydrologic budget. To better understand long-term changes in regional ITCZ-driven precipitation we re-examined a coral δ18O record from a Porites lobata coral head near Secas Island (Core ID: S1) (7°59′ N, 82°3′ W) in the Gulf of Chiriquí on the Pacific side of Panamá. Linsley et al., (1994) originally published the 277-year time series and first described the presence of a narrow-band decadal cycle (period near 9–12 years) in δ18O. The original study did not present potential drivers for the decadal cycle, although they ruled out the influence of the sun spot cycle. Our re-analysis of this record supports the original interpretation that coral δ18O is largely responding to variations in precipitation and associated river discharge, but with a new proposed mechanism to explain the decadal mode. There is no similar decadal cycle in gridded instrumental sea surface temperature from the area, suggesting that the decadal coral δ18O signal results from hydrologic changes that influence coastal δ18O seawater. The decadal component in S1 δ18O is also coherent with a decadal mode embedded in the Pacific Decadal Oscillation (PDO) Index that we suggest has tropical origins. We speculate that the coral's temporary δ18O deviation (1900–1930) in the decadal mode from the corresponding bands in rainfall and the PDO can be ascribed to a weak PDO in addition to local Panama gap wind variability and its effect on moisture transport from the Atlantic to the Pacific. Ultimately, the Secas Island coral δ18O series records ITCZ-driven precipitation dictated by both the Atlantic and Pacific basins

Mechanical Work as an Indirect Measure of Subjective Costs Influencing Human Movement

To descend a flight of stairs, would you rather walk or fall? Falling seems to have some obvious disadvantages such as the risk of pain or injury. But the preferred strategy of walking also entails a cost for the use of active muscles to perform negative work. The amount and distribution of work a person chooses to perform may, therefore, reflect a subjective valuation of the trade-offs between active muscle effort and other costs, such as pain. Here we use a simple jump landing experiment to quantify the work humans prefer to perform to dissipate the energy of landing. We found that healthy normal subjects (N = 8) preferred a strategy that involved performing 37% more negative work than minimally necessary (P<0.001) across a range of landing heights. This then required additional positive work to return to standing rest posture, highlighting the cost of this preference. Subjects were also able to modulate the amount of landing work, and its distribution between active and passive tissues. When instructed to land softly, they performed 76% more work than necessary (P<0.001), with a higher proportion from active muscles (89% vs. 84%, P<0.001). Stiff-legged landings, performed by one subject for demonstration, exhibited close to the minimum of work, with more of it performed passively through soft tissue deformations (at least 30% in stiff landings vs. 16% preferred). During jump landings, humans appear not to minimize muscle work, but instead choose to perform a consistent amount of extra work, presumably to avoid other subjective costs. The degree to which work is not minimized may indirectly quantify the relative valuation of costs that are otherwise difficult to measure