3,219 research outputs found
Glacial climate sensitivity to different states of the Atlantic Meridional Overturning Circulation: results from the IPSL model
Paleorecords from distant locations on the globe show rapid and large amplitude climate variations during the last glacial period. Here we study the global climatic response to different states of the Atlantic Meridional Overturning Circulation (AMOC) as a potential explanation for these climate variations and their possible connections. We analyse three glacial simulations obtained with an atmosphere-ocean coupled general circulation model and characterised by different AMOC strengths (18, 15 and 2 Sv) resulting from successive ~0.1 Sv freshwater perturbations in the North Atlantic. These AMOC states suggest the existence of a freshwater threshold for which the AMOC collapses. A weak (18 to 15 Sv) AMOC decrease results in a North Atlantic and European cooling. This cooling is not homogeneous, with even a slight warming over the Norwegian Sea. Convection in this area is active in both experiments, but surprisingly stronger in the 15 Sv simulation, which appears to be related to interactions with the atmospheric circulation and sea-ice cover. Far from the North Atlantic, the climatic response is not significant. The climate differences for an AMOC collapse (15 to 2 Sv) are much larger and of global extent. The timing of the climate response to this AMOC collapse suggests teleconnection mechanisms. Our analyses focus on the North Atlantic and surrounding regions, the tropical Atlantic and the Indian monsoon region. The North Atlantic cooling associated with the AMOC collapse induces a cyclonic atmospheric circulation anomaly centred over this region, which modulates the eastward advection of cold air over the Eurasian continent. This can explain why the cooling is not as strong over western Europe as over the North Atlantic. In the Tropics, the southward shift of the Inter-Tropical Convergence Zone appears to be strongest over the Atlantic and Eastern Pacific and results from an adjustment of the atmospheric and oceanic heat transports. Finally, the Indian monsoon weakening appears to be connected to the North Atlantic cooling via that of the troposphere over Eurasia. Such an understanding of these teleconnections and their timing could be useful for paleodata interpretation
Polarization dependence of emission spectra of multiexcitons in self-assembled quantum dots
We have investigated the polarization dependence of the emission spectra of
p-shell multiexcitons of a quantum dot when the single particle level spacing
is larger than the characteristic energy of the Coulomb interactions. We find
that there are many degenerate multiexciton states. The emission intensities
depend on the number of degenerate initial and final states of the optical
transitions. However, unlike the transition energies, they are essentially
independent of the strength of the Coulomb interactions. In the presence of
electron-hole symmetry the independence is exact.Comment: 7 pages, 5 figures, published in Solid State Commu
A DrugâDrug Interaction Study to Investigate the Effect of Nintedanib on the Pharmacokinetics of Microgynon (Ethinylestradiol and Levonorgestrel) in Female Patients with Systemic Sclerosis-Associated Interstitial Lung Disease
Nintedanib; Drug Interactions; Systemic SclerosisNintedanib; Interacciones medicamentosas; Esclerosis sistĂ©micaNintedanib; Interaccions farmacolĂČgiques; Esclerosi sistĂšmicaBackground and Objectives
Nintedanib is a tyrosine kinase inhibitor approved for the treatment of systemic sclerosis-associated interstitial lung disease (SSc-ILD), idiopathic pulmonary fibrosis, and other chronic fibrosing ILDs with a progressive phenotype. As nintedanib may cause foetal harm, patients taking nintedanib should avoid pregnancy. The objective of this study was to investigate the effect of nintedanib co-administration on the pharmacokinetics of Microgynon (ethinylestradiol and levonorgestrel) in female patients with SSc-ILD.
Methods
This was an open-label, two-period, fixed-sequence, drugâdrug interaction study. Female patients with SSc and â„ 10% extent of fibrotic ILD on a high-resolution computed tomography scan were eligible to participate. In Period 1, patients received one Microgynon tablet (ethinylestradiol 30 ÎŒg and levonorgestrel 150 ÎŒg) â„ 3 days before the first administration of nintedanib in Period 2. In Period 2, patients received one Microgynon tablet following intake of nintedanib 150 mg twice daily for â„ 10 consecutive days. The primary pharmacokinetic endpoints were the areas under the plasma concentrationâtime curve of ethinylestradiol and levonorgestrel over the time interval from 0 to the last quantifiable data point (AUC0âtz) and the maximum measured concentrations of ethinylestradiol and levonorgestrel in plasma (Cmax). The secondary pharmacokinetic endpoint was the area under the plasma concentrationâtime curve of ethinylestradiol and levonorgestrel over the time interval from 0 extrapolated to infinity (AUC0ââ). The relative exposures of ethinylestradiol and levonorgestrel when administered alone and in combination with nintedanib were assessed using an ANOVA model.
Results
Seventeen patients were treated. Pharmacokinetic data from 15 patients were analysed. Plasma concentrationâtime profiles of ethinylestradiol and levonorgestrel were similar following administration of Microgynon before and after administration of nintedanib for â„ 10 consecutive days. Adjusted geometric mean (gMean) ratios [90% confidence intervals (CIs)] for AUC0âtz (101.4% [92.8, 110.7]) and AUC0ââ (101.2% [94.0, 109.1]) indicated that there was no difference in total ethinylestradiol exposure when Microgynon was administered before or after administration of nintedanib. The adjusted gMean ratio for Cmax of ethinylestradiol (116.7% [90% CI 107.6, 126.5]) indicated an increase in peak exposure in the presence of nintedanib. Adjusted gMean ratios [90% CIs] for AUC0-tz (96.4% [91.5, 101.6]) and Cmax (100.9% [89.9, 113.2]) indicated that there was no difference in total or peak levonorgestrel exposure when Microgynon was administered before or after administration of nintedanib. The adjusted gMean ratio for AUC0ââ of levonorgestrel indicated a decrease in total exposure in the presence of nintedanib (88.1% [90% CI 80.0, 97.0]).
Conclusion
Pharmacokinetic data indicate that there is no relevant effect of nintedanib on plasma exposure to ethinylestradiol and levonorgestrel in female patients with SSc-ILD
Effect of deconfinement on resonant transport in quantum wires
The effect of deconfinement due to finite band offsets on transport through
quantum wires with two constrictions is investigated. It is shown that the
increase in resonance linewidth becomes increasingly important as the size is
reduced and ultimately places an upper limit on the energy (temperature) scale
for which resonances may be observed.Comment: 6 pages, 6 postscript files with figures; uses REVTe
Localized states in strong magnetic field: resonant scattering and the Dicke effect
We study the energy spectrum of a system of localized states coupled to a 2D
electron gas in strong magnetic field. If the energy levels of localized states
are close to the electron energy in the plane, the system exhibits a kind of
collective behavior analogous to the Dicke effect in optics. The latter
manifests itself in ``trapping'' of electronic states by localized states. At
the same time, the electronic density of states develops a gap near the
resonance. The gap and the trapping of states appear to be complementary and
reflect an intimate relation between the resonant scattering and the Dicke
effect. We reveal this relation by presenting the exact solution of the problem
for the lowest Landau level. In particular, we show that in the absence of
disorder the system undergoes a phase transition at some critical concentration
of localized states.Comment: 28 pages + 9 fig
Scanning Fourier Spectroscopy: A microwave analog study to image transmission paths in quantum dots
We use a microwave cavity to investigate the influence of a movable absorbing
center on the wave function of an open quantum dot. Our study shows that the
absorber acts as a position-selective probe, which may be used to suppress
those wave function states that exhibit an enhancement of their probability
density near the region where the impurity is located. For an experimental
probe of this wave function selection, we develop a technique that we refer to
as scanning Fourier spectroscopy, which allows us to identify, and map out, the
structure of the classical trajectories that are important for transmission
through the cavity.Comment: 4 pages, 5 figure
Luminescence from highly excited nanorings: Luttinger liquid description
We study theoretically the luminescence from quantum dots of a ring geometry.
For high excitation intensities, photoexcited electrons and holes form Fermi
seas. Close to the emission threshold, the single-particle spectral lines
aquire weak many-body satellites. However, away from the threshold, the
discrete luminescence spectrum is completely dominated by many-body
transitions. We employ the Luttinger liquid approach to exactly calculate the
intensities of all many-body spectral lines. We find that the transition from
single-particle to many-body structure of the emission spectrum is governed by
a single parameter and that the distribution of peaks away from the threshold
is universal.Comment: 10 pages including 2 figure
Tight-binding study of the influence of the strain on the electronic properties of InAs/GaAs quantum dots
We present an atomistic investigation of the influence of strain on the
electronic properties of quantum dots (QD's) within the empirical tight-binding (ETB) model with interactions up to 2nd nearest neighbors
and spin-orbit coupling. Results for the model system of capped pyramid-shaped
InAs QD's in GaAs, with supercells containing atoms are presented and
compared with previous empirical pseudopotential results. The good agreement
shows that ETB is a reliable alternative for an atomistic treatment. The strain
is incorporated through the atomistic valence force field model. The ETB
treatment allows for the effects of bond length and bond angle deviations from
the ideal InAs and GaAs zincblende structure to be selectively removed from the
electronic-structure calculation, giving quantitative information on the
importance of strain effects on the bound state energies and on the physical
origin of the spatial elongation of the wave functions. Effects of dot-dot
coupling have also been examined to determine the relative weight of both
strain field and wave function overlap.Comment: 22 pages, 7 figures, submitted to Phys. Rev. B (in press) In the
latest version, added Figs. 3 and 4, modified Fig. 5, Tables I and II,.and
added new reference
Efficient Passive ICS Device Discovery and Identification by MAC Address Correlation
Owing to a growing number of attacks, the assessment of Industrial Control
Systems (ICSs) has gained in importance. An integral part of an assessment is
the creation of a detailed inventory of all connected devices, enabling
vulnerability evaluations. For this purpose, scans of networks are crucial.
Active scanning, which generates irregular traffic, is a method to get an
overview of connected and active devices. Since such additional traffic may
lead to an unexpected behavior of devices, active scanning methods should be
avoided in critical infrastructure networks. In such cases, passive network
monitoring offers an alternative, which is often used in conjunction with
complex deep-packet inspection techniques. There are very few publications on
lightweight passive scanning methodologies for industrial networks. In this
paper, we propose a lightweight passive network monitoring technique using an
efficient Media Access Control (MAC) address-based identification of industrial
devices. Based on an incomplete set of known MAC address to device
associations, the presented method can guess correct device and vendor
information. Proving the feasibility of the method, an implementation is also
introduced and evaluated regarding its efficiency. The feasibility of
predicting a specific device/vendor combination is demonstrated by having
similar devices in the database. In our ICS testbed, we reached a host
discovery rate of 100% at an identification rate of more than 66%,
outperforming the results of existing tools.Comment: http://dx.doi.org/10.14236/ewic/ICS2018.
The Aharonov-Bohm effect for an exciton
We study theoretically the exciton absorption on a ring shreded by a magnetic
flux. For the case when the attraction between electron and hole is
short-ranged we get an exact solution of the problem. We demonstrate that,
despite the electrical neutrality of the exciton, both the spectral position of
the exciton peak in the absorption, and the corresponding oscillator strength
oscillate with magnetic flux with a period ---the universal flux
quantum. The origin of the effect is the finite probability for electron and
hole, created by a photon at the same point, to tunnel in the opposite
directions and meet each other on the opposite side of the ring.Comment: 13 RevTeX 3.0 pages plus 4 EPS-figures, changes include updated
references and an improved chapter on possible experimental realization
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