1,511 research outputs found
Correlation Effects in Side-Coupled Quantum Dots
Using Wilson's numerical renormalization group (NRG) technique we compute
zero-bias conductance and various correlation functions of a double quantum dot
(DQD) system. We present different regimes within a phase diagram of the DQD
system. By introducing a negative Hubbard U on one of the quantum dots, we
simulate the effect of electron-phonon coupling and explore the properties of
the coexisting spin and charge Kondo state. In a triple quantum dot (TQD)
system a multi-stage Kondo effect appears where localized moments on quantum
dots are screened successively at exponentially distinct Kondo temperatures.Comment: 13 pages, 10 figure
Relevance of quantum fluctuations in the Anderson-Kondo model
We study a localized spin coupled to an Anderson impurity to model the
situation found in higher transition metal or rare earth compounds like e.g.\
LaMnO or Gd monopnictides. We find that, even for large quantum numbers of
the localized spin, quantum fluctuations play an essential role for the case of
ferromagnetic coupling between the spin and the impurity levels. For
antiferromagnetic coupling, a description in terms of a classical spin is
appropriate
Performance of the PROSPECT leaf radiative transfer model version 4 for Norway spruce needles
Leaf optical properties (LOPs) are a key input parameter for vegetation canopy radiative transfer models. The uncertainty introduced in the measurement and/or the simulation of this spectral information determines a final reliability of the modelled canopy reflectance. The broad-leaf radiative transfer model PROSPECT version 3.01 has been previously applied for some needle-leaf type species (e.g. pine trees) to estimate biochemical parameters through its inversion. Nevertheless, in a particular case of Norway spruce (Picea abies (L.) Karst.) PROSPECT 3.01 showed a poor performance in near infrared wavelengths and had to be recalibrated. Therefore, the applicability of PROSPECT version 4, which has been recently released, is verified for this type of leaves in this experiment. Forward simulations of an optimized version of the original PROSPECT 4 suggest that it is possible to reduce the average RMSE of reflectance and transmittance from 8% to 3.5- 4 % in the near infrared domain. For this achievement, the absorption coefficients for chlorophyll and dry matter together with the refractive index had to be simultaneously optimized via model inversion using measured LOPs of Norway spruce needles
Mindfulness and Symptoms o f Depression and Anxiety in the General Population: The Mediating Roles of Worry, Rumination, Reappraisal and Suppression
The present study examined the effects of mindfulness on depression and anxiety, both direct and indirect through the mediation of four mechanisms of emotional regulation: worry, rumination, reappraisal and suppression. Path analysis was applied to data collected from an international and non-clinical sample of 1151 adults, including both meditators and non-meditators, who completed an online questionnaire battery. Our results show that mindfulness are related to lower levels of depression and anxiety both directly and indirectly. Suppression, reappraisal, worry and rumination all acted as significant mediators of the relationship between mindfulness and depression. A similar picture emerged for the relationship between mindfulness and anxiety, with the difference that suppression was not a mediator. Our data also revealed that the estimated number of hours of mindfulness meditation practice did not affect depression or anxiety directly but did reduce these indirectly by increasing mindfulness. Worry and rumination proved to be the most potent mediating variables. Altogether, our results confirm that emotional regulation plays a significant mediating role between mindfulness and symptoms of depression and anxiety in the general population and suggest that meditation focusing on reducing worry and rumination may be especially useful in reducing the risk of developing clinical depression
The interaction of 11Li with 208Pb
Background: 11Li is one of the most studied halo nuclei. The fusion of 11Li
with 208Pb has been the subject of a number of theoretical studies with widely
differing predictions, ranging over four orders of magnitude, for the fusion
excitation function.
Purpose: To measure the excitation function for the 11Li + 208Pb reaction.
Methods: A stacked foil/degrader assembly of 208Pb targets was irradiated
with a 11Li beam producing center of target beam energies from above barrier to
near barrier energies (40 to 29 MeV). The intensity of the 11Li beam (chopped)
was 1250 p/s and the beam on-target time was 34 hours. The alpha-decay of the
stopped evaporation residues was detected in a alpha-detector array at each
beam energy in the beam-off period (the beam was on for <= 5 ns and then off
for 170 ns).
Results: The 215At evaporation residues were associated with the fusion of
11Li with 208Pb. The 213,214At evaporation residues were formed by the breakup
of 11Li into 9Li + 2n, with the 9Li fusing with 208Pb. The 214At evaporation
residue appears to result from a "quasi-breakup" process.
Conclusions: Most of 11Li + 208Pb interactions lead to breakup with a small
fraction (<= 11%) leading to complete fusion.Comment: 25 pages, 11 figure
- …