914 research outputs found
The Exact Potential Driving the Electron Dynamics in Enhanced Ionization
It was recently shown that the exact factorization of the electron-nuclear
wavefunction allows the construction of a Schr\"odinger equation for the
electronic system, in which the potential contains exactly the effect of
coupling to the nuclear degrees of freedom and any external fields. Here we
study the exact potential acting on the electron in charge-resonance enhanced
ionization in a model one-dimensional H molecule. We show there can be
significant differences between the exact potential and that used in the
traditional quasistatic analyses, arising from non-adiabatic coupling to the
nuclear system, and that these are crucial to include for accurate simulations
of time-resolved ionization dynamics and predictions of the ionization yield
Laser-induced electron localization in H: Mixed quantum-classical dynamics based on the exact time-dependent potential energy surface
We study the exact nuclear time-dependent potential energy surface (TDPES)
for laser-induced electron localization with a view to eventually developing a
mixed quantum-classical dynamics method for strong-field processes. The TDPES
is defined within the framework of the exact factorization [A. Abedi, N. T.
Maitra, and E. K. U. Gross, Phys. Rev. Lett. 105, 123002 (2010)] and contains
the exact effect of the couplings to the electronic subsystem and to any
external fields within a scalar potential. We compare its features with those
of the quasistatic potential energy surfaces (QSPES) often used to analyse
strong-field processes. We show that the gauge-independent component of the
TDPES has a mean-field-like character very close to the density-weighted
average of the QSPESs. Oscillations in this component are smoothened out by the
gauge-dependent component, and both components are needed to yield the correct
force on the nuclei. Once the localization begins to set in, the gradient of
the exact TDPES tracks one QSPES and then switches to the other, similar to the
description provided by surface-hopping between QSPESs. We show that evolving
an ensemble of classical nuclear trajectories on the exact TDPES accurately
reproduces the exact dynamics. This study suggests that the mixed
quantum-classical dynamics scheme based on evolving multiple classical nuclear
trajectories on the exact TDPES will be a novel and useful method to simulate
strong field processes.Comment: 10 pages, 6 figure
Scintigraphy with 99mTc(V)-DMSA in monitoring patients with inflammatory bowel disease
The clinical significance of pentavalent technetium-99m dimercaptosuccinic acid (99mTc(V)-DMSA) scintigraphy in diagnosing inflammatory bowel disease (IBD) has not yet been fully elucidated. The aim of this prospective paper was to study the above. This study included 54 patients, 22 females and 32 males (mean age: 36.68±11.49; range: 18-63 years) with IBD who came to our clinics for follow-up and were examined clinically by colonoscopy and 99mTc(V)-DMSA scintigraphy. On the follow-up studies, five patients (9.25%) relapsed, and 49 (90.74%) remained at a steady condition. There was a good correlation between the scintigraphic results and the clinical and colonoscopy data of the patients (P<0.05). In conclusion, our results indicated that 99mTc(V)DMSA scintigraphy can be complementary to colonoscopy for the diagnostic evaluation of IBD
Electronic non-adiabatic dynamics in enhanced ionization of isotopologues of hydrogen molecular ions from the exact factorization perspective
It was recently shown that the exact potential driving the electron's dynamics in enhanced ionization of H-2(+) can have large contributions arising from dynamic electron-nuclear correlation, going beyond what any Coulombic-based model can provide. This potential is defined via the exact factorization of the molecular wavefunction that allows the construction of a Schro "dinger equation for the electronic system, in which the potential contains exactly the effect of coupling to the nuclear system and any external fields. Here we study enhanced ionization in isotopologues of H-2(+) in order to investigate the nuclear-mass-dependence of these terms for this process. We decompose the exact potential into components that naturally arise from the conditional wavefunction, and also into components arising from the marginal electronic wavefunction, and compare the performance of propagation on these different components as well as approximate potentials based on the quasi-static or Hartree approximation with the exact propagation. A quasiclassical analysis is presented to help analyse the structure of different non-Coulombic components of the potential driving the ionizing electron.We acknowledge support from the European Research Council (ERC-2015-AdG-694097), Grupos Consolidados (IT578-13), and the European Union's Horizon 2020 Research and Innovation programme under grant agreement no. 676580. A. K. and A. A. acknowledge funding from the European Union's Horizon 2020 research and innovation programme under the Marie SklodowskaCurie grant agreement no. 704218 and 702406, respectively. N. T. M. thanks the National Science Foundation, grant CHE1566197, for support. Open Access funding provided by the Max Planck Society
Hybrid Testbed for Security Research in Software-Defined Networks
Tele-operations require secure end-to-end Network Slicing leveraging Software-Defined Networking to meet the diverse requirements of multi-modal data streams. Research on network slicing needs tools to develop prototypes quickly that work on emulation and practical deployment. However, state-of-the-art tools focus only on emulation, needing more support for a mixed testbed, including hardware devices. We decouple the topology generating from the actual deployment on destination domains and apply a divide-and-conquer approach. The master coordinator generates an Intermediate Representation (IR) layer, a serialization of the topology. Via a toolchain, the worker coordinators at autonomous systems convert the IR into full or partial deployment scripts. The testbed introduces a marginal overhead by design, allowing for flexible deployment of complex topologies to study secure end-to-end Network Slicing
Behavior of Braced Sheetpile Excavation in Detroit Clay
This paper presents the design criteria, finite element modeling and actual behavior of a braced sheetpile excavation in Detroit soft clay. Due to the close proximity of existing structures to the excavation, a detailed analysis was performed to design and construct an earth retention system to avoid damage to these structures. The excavation involved a 170 ft by 220 ft area. The maximum depth of excavation was 23.5 ft. The subsurface soil consists of soft to very soft Detroit clay from the excavation level to a depth of 80 ft and has an undrained shear strength as low as 360 psf
Performance of a Semi-Rigid Braced Excavation in Soft Clay
Construction of a 21-foot wide, 28-foot deep braced excavation in Detroit soft clays has been completed. In order to protect an existing 50-year old tunnel adjacent to the excavation, a semi-rigid, tangent wall earth retention system was constructed to minimize the soil movements. The tangent wall was formed by 118 drilled piers with 42-inch in diameter and 41-foot long. The maximum soil lateral and vertical movements adjacent to the excavation were controlled below a magnitude of 2.0 inches, while bottom of the excavation experienced about 3 inches of heave. This paper presents the design considerations and construction performance of the retention system based on geotechnical instrumentation data. Prediction of maximum soil lateral movement based on a finite element analysis and a semi-empirical method conformed well with field measurements. Experience learned from the design and construction will be valuable for future construction of braced excavation systems in similar soil conditions
The exact forces on classical nuclei in non-adiabatic charge transfer
The decomposition of electronic and nuclear motion presented in Abedi et al. [Phys. Rev. Lett. 105, 123002 (2010)] yields a time-dependent potential that drives the nuclear motion and fully accounts for the coupling to the electronic subsystem. Here, we show that propagation of an ensemble of independent classical nuclear trajectories on this exact potential yields dynamics that are essentially indistinguishable from the exact quantum dynamics for a model non-adiabatic charge transfer problem. We point out the importance of step and bump features in the exact potential that are critical in obtaining the correct splitting of the quasiclassical nuclear wave packet in space after it passes through an avoided crossing between two Born-Oppenheimer surfaces and analyze their structure. Finally, an analysis of the exact potentials in the context of trajectory surface hopping is presented, including preliminary investigations of velocity-adjustment and the force-induced decoherence effect. (C) 2015 AIP Publishing LLC.open5
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