Strongly enhanced shot noise in chains of quantum dots

We study charge transport through a chain of quantum dots. The dots are fully coherent among each other and weakly coupled to metallic electrodes via the dots at the interface, thus modelling a molecular wire. If the non-local Coulomb interactions dominate over the inter-dot hopping we find strongly enhanced shot noise above the sequential tunneling threshold. The current is not enhanced in the region of enhanced noise, thus rendering the noise super-Poissonian. In contrast to earlier work this is achieved even in a fully symmetric system. The origin of this novel behavior lies in a competition of "slow" and "fast" transport channels that are formed due to the differing non-local wave functions and total spin of the states participating in transport. This strong enhancement may allow direct experimental detection of shot noise in a chain of lateral quantum dots.Comment: 4 pages, 2 figures, submitted to PR

The dark core of personality and socially aversive psychopathology

Objective: Although dark traits as studied in mainstream personality research and socially aversive psychopathology as studied in abnormal psychology intend to account for the same classes of behavior, their degree of conceptual and, consequently, empirical correspondence has remained limited at best. We aim to overcome this divide by demonstrating clear convergence between the common core of all dark traits (the Dark Factor of Personality, D) and the four prominent instances of socially aversive psychopathology: narcissistic, antisocial, paranoid, and borderline tendencies. Method: In a large-scale, eight-month longitudinal study we assessed D, basic personality (the six HEXACO dimensions), and narcissistic, antisocial, paranoid, and borderline tendencies at time 1 (N = 2,329) and the latter aversive tendencies again at time 2 (N = 668) using different inventories. Results: D predicted all instances of socially aversive psychopathology cross-sectionally and longitudinally, with a large effect size on average, beyond the six HEXACO dimensions and even beyond the very same instances (measured through a different inventory). Conclusions: Bridging mainstream personality and abnormal psychology, the findings reveal strong, theory-consistent correspondence between dark traits and socially aversive psychopathology once dark traits are viewed through the lens of their common core, D

Narrow, Fast, and "Cool" Mantle Plumes Caused by Strain-Weakening Rheology in Earth's Lower Mantle

The rheological properties of Earth's lower mantle are key for mantle dynamics and planetary evolution. The main rock-forming minerals in the lower mantle are bridgmanite (Br) and smaller amounts of ferropericlase (Fp). Previous work has suggested that the large differences in viscosity between these minerals greatly affect the bulk rock rheology. The resulting effective rheology becomes highly strain-dependent as weaker Fp minerals become elongated and eventually interconnected. This implies that strain localization may occur in Earth's lower mantle. So far, there have been no studies on global-scale mantle convection in the presence of such strain-weakening (SW) rheology. Here, we present 2D numerical models of thermo-chemical convection in spherical annulus geometry including a new strain-dependent rheology formulation for lower mantle materials, combining rheological weakening and healing terms. We find that SW rheology has several direct and indirect effects on mantle convection. The most notable direct effect is the changing dynamics of weakened plume channels as well as the formation of larger thermochemical piles at the base of the mantle. The weakened plume conduits act as lubrication channels in the mantle and exhibit a lower thermal anomaly. SW rheology also reduces the overall viscosity, notable in terms of increasing convective vigor and core-mantle boundary heat flux. Finally, we put our results into context with existing hypotheses on the style of mantle convection and mixing. Most importantly, we suggest that the new kind of plume dynamics may explain the discrepancy between expected and observed thermal anomalies of deep-seated mantle plumes on Earth

Super-poissonian noise, negative differential conductance, and relaxation effects in transport through molecules, quantum dots and nanotubes

We consider charge transport through a nanoscopic object, e.g. single molecules, short nanotubes, or quantum dots, that is weakly coupled to metallic electrodes. We account for several levels of the molecule/quantum dot with level-dependent coupling strengths, and allow for relaxation of the excited states. The current-voltage characteristics as well as the current noise are calculated within first-order perturbation expansion in the coupling strengths. For the case of asymmetric coupling to the leads we predict negative-differential-conductance accompanied with super-poissonian noise. Both effects are destroyed by fast relaxation processes. The non-monotonic behavior of the shot noise as a function of bias and relaxation rate reflects the details of the electronic structure and level-dependent coupling strengths.Comment: 8 pages, 7 figures, submitted to Phys. Rev. B, added reference

Discretization Errors in the Hybrid Finite Element Particle-in-cell Method

In computational geodynamics, the Finite Element (FE) method is frequently used. The method is attractive as it easily allows employment of body-fitted deformable meshes and a true free surface boundary condition. However, when a Lagrangian mesh is used, remeshing becomes necessary at large strains to avoid numerical inaccuracies (or even wrong results) due to severely distorted elements. For this reason, the FE method is oftentimes combined with the particle-in-cell (PIC) method, where particles are introduced which track history variables and store constitutive information. This implies that the respective material properties have to be interpolated from the particles to the integration points of the finite elements. In numerical geodynamics, material parameters (in particular the viscosity) usually vary over a large range. This may be due to strongly temperature-dependent rheologies (which result in large but smooth viscosity variations) or material interfaces (which result in viscosity jumps). Here, we analyze the accuracy and convergence properties of velocity and pressure of the hybrid FE-PIC method in the presence of large viscosity variations. Standard interpolation schemes (arithmetic and harmonic) are compared to a more sophisticated interpolation scheme which is based on linear least squares interpolation for two types of elements ( $$Q_1P_0$$ Q 1 P 0 and $$Q_2P_{-1}$$ Q 2 P - 1 ). In the case of a smooth viscosity field, the accuracy and convergence is significantly improved by the new interpolation scheme. In the presence of viscosity jumps, the order of accuracy is strongly decreased

Signals of slab breakoff- and tearing in the stratigraphic architecture of a foreland basin

A significant change in the architecture of peripheral pro-foreland basins observed in all natural examples is the flysch to molasse transition (i.e., shift from underfilled- to overfilled conditions). Forcing mechanisms for pro-foreland basin architecture include changes in sediment supply from the adjacent growing orogen and flexural subsidence in the basin. As these forcing mechanisms themselves are driven by orogenic processes in the adjacent mountain range, the flysch to molasse transition can be regarded as the sedimentary fingerprint of hinterland tectonics. Slab breakoff of the foreland plate leading to isostatic rebound of both the pro-foreland basin and adjacent orogen (leading to increased sediment supply) has been suggested to be a driver of the flysch to molasse transition. However, this cause-and-effect relationship between slab breakoff and the flysch to molasse transition is based on qualitative assessments. This raises the question whether other external forcings may have masked the contribution of slab breakoff to the flysch to molasse transition. In this study we investigate the stratigraphic signal of slab breakoff in a pro-foreland basin. To quantitatively assess the relationship between slab breakoff and the flysch to molasse transition, we coupled 2D geodynamic models (GMs) of slab breakoff using LaMEM with 2D forward stratigraphic modelling (FSM) using the GPM software (SLB). To better understand the influence of slab breakoff on pro-foreland basin architecture, we tested slab breakoff scenarios in our GMs for varying 1) slab bending angles and 2) slab necking durations (depending on slab rheology). To test whether the stratigraphic signal of slab breakoff may be masked by other external forcings, we introduced eustatic sea level changes (50 m amplitude with a 1 My period). From our FSMs we generated sediment thickness maps used to reconstruct sediment supply rates, grain size distribution- and facies maps and synthetic seismic data to compare with observed seismic data. Our preliminary results indicate that vertical uplift due to isostatic rebound in the pro-foreland basin (1.5 – 7 cm/yr, where fast necking of steep slabs yields higher values) decreases the accommodation space, leading to a stratigraphically upward shallowing. Furthermore, isostatic rebound of the adjacent mountain range (2-5 cm/yr, same relationship with slab dynamics as pro-foreland basin) results in up to 2.5x increased rates of sediment supply with very little lag time, adding to the stratigraphically upward shallowing. The eustatic sea level changes do not mask the stratigraphic signal of slab breakoff. Lastly, the facies of the flysch to molasse transition in our synthetic seismics looks similar to that observed on seismics of the Austrian Molasse which occurred coeval with slab breakoff under the Eastern Alps

Shot noise in tunneling transport through molecules and quantum dots

We consider electrical transport through single molecules coupled to metal electrodes via tunneling barriers. Approximating the molecule by the Anderson impurity model as the simplest model which includes Coulomb charging effects, we extend the ``orthodox'' theory to expand current and shot noise systematically order by order in the tunnel couplings. In particular, we show that a combined measurement of current and shot noise reveals detailed information of the system even in the weak-coupling limit, such as the ratio of the tunnel-coupling strengths of the molecule to the left and right electrode, and the presence of the Coulomb charging energy. Our analysis holds for single-level quantum dots as well.Comment: 8 page

Impact of repeated percutaneous coronary intervention on long-term survival after subsequent coronary artery bypass surgery

<p>Abstract</p> <p>(Background)</p> <p>In the current stent era, aggressive repeated percutaneous coronary intervention (PCI) has become more common. The aim of this study was to investigate the impact of previous repeated PCI on the subsequent coronary artery bypass grafting (CABG).</p> <p>(Methods)</p> <p>Between January 1990 and January 2008, a total of 894 patients underwent first-time isolated elective CABG. Among the 894 patients, 515 patients had had no PCI (group A), 179 patients had had single PCI (Group B), and 200 patients had had multiple PCI (2-15 times, mean 3.6 ± 2.3 times) (group C) before CABG. These groups were compared in terms of early and late clinical results.</p> <p>(Results)</p> <p>Preoperative left ventricular ejection fraction was significantly higher in group A (group A;58 ± 13%, group B;54 ± 12%, and group C;54 ± 12%). Number of bypass grafts was significantly smaller in group C (A:3.3 ± 1.0, B 3.4 ± 0.9, C 3.1 ± 1.0). Although there was no statistically significant difference among the groups, in-hospital mortality in group C was higher than that in group A and B (A:1.6%, B:1.1%, C:3.5%, p = 0.16). Survival analysis by Kaplan-Meier method (mean follow-up: 58 ± 43 methods) revealed that freedom from all-cause death and cardiac death was significantly lower in group C in comparison with group A. Freedom from cardiac event was significantly higher in group C than that in group A. Multivariate analysis identified a number of previous PCI as an independent risk factor for cardiac death.</p> <p>(Conclusions)</p> <p>Repeated PCI increased risk for long-term prognosis of subsequent CABG.</p

A transdisciplinary and community-driven database to unravel subduction zone initiation

Subduction zones are pivotal for the recycling of Earth’s outer layer into its interior. However, the conditions under which new subduction zones initiate are enigmatic. Here, we constructed a transdisciplinary database featuring detailed analysis of more than a dozen documented subduction zone initiation events from the last hundred million years. Our initial findings reveal that horizontally forced subduction zone initiation is dominant over the last 100 Ma, and that most initiation events are proximal to pre-existing subduction zones. The SZI Database is expandable to facilitate access to the most current understanding of subduction zone initiation as research progresses, providing a community platform that establishes a common language to sharpen discussion across the Earth Science community