232 research outputs found
Environment-assisted quantum transport in a 10-qubit network
The way in which energy is transported through an interacting system governs
fundamental properties in many areas of physics, chemistry, and biology.
Remarkably, environmental noise can enhance the transport, an effect known as
environment-assisted quantum transport (ENAQT). In this paper, we study ENAQT
in a network of coupled spins subject to engineered static disorder and
temporally varying dephasing noise. The interacting spin network is realized in
a chain of trapped atomic ions and energy transport is represented by the
transfer of electronic excitation between ions. With increasing noise strength,
we observe a crossover from coherent dynamics and Anderson localization to
ENAQT and finally a suppression of transport due to the quantum Zeno effect. We
found that in the regime where ENAQT is most effective the transport is mainly
diffusive, displaying coherences only at very short times. Further, we show
that dephasing characterized by non-Markovian noise can maintain coherences
longer than white noise dephasing, with a strong influence of the spectral
structure on the transport effciency. Our approach represents a controlled and
scalable way to investigate quantum transport in many-body networks under
static disorder and dynamic noise.Comment: Mai
Involvement of multiple genetic loci in Staphylococcus aureus teicoplanin resistance
Teicoplanin resistance was transformed from a teicoplanin-resistant Staphylococcus aureus into the susceptible strain BB255 to give strain BB938. The cell wall composition, amidation of the iD-glutamate, and peptide crosslinking were identical in BB938 as in BB255 except for a 60% increased length of the glycan chain. Transductional crosses revealed that at least two distinct loci contributed in a cumulative fashion to teicoplanin resistance. One of these loci correlated with a mutation inactivating the anti-sigma factor RsbW. This mutation must have occurred during transformation and selection for teicoplanin resistance in BB938. Genetic manipulations involving the sigB operon showed that transcription factor SigB contributed to decreased teicoplanin susceptibilit
Influence of adatom interactions on second layer nucleation
We develop a theory for the inclusion of adatom interactions in second layer
nucleation occurring in epitaxial growth. The interactions considered are due
to ring barriers between pairs of adatoms and binding energies of unstable
clusters. The theory is based on a master equation, which describes the time
development of microscopic states that are specified by cluster configurations
on top of an island. The transition rates are derived by scaling arguments and
tested against kinetic Monte-Carlo simulations. As an application we reanalyze
experiments to determine the step edge barrier for Ag/Pt(111).Comment: 4 pages, 4 figure
Spectrophotometric Evaluation of Polyetheretherketone (PEEK) as a Core Material and a Comparison with Gold Standard Core Materials
This study investigated the colorimetric properties of different veneering materials on core materials. Standardized specimens (10 mm x 10 mm x 1.5 mm) reflecting four core (polyetheretherketone (PEEK), zirconia (ZrO2), cobalt-chromium-molybdenum alloy (CoCrMo), and titanium oxide (TiO2);thickness: 1.5 mm) and veneering materials (VITA Mark II, IPS e.max CAD, LAVA Ultimate and VITA Enamic, all in shade A3;thickness: 0.5, 1.0, 1.5 and 2 mm, respectively) were fabricated. Specimens were superimposed to assemblies, and the color was determined with a spectrophotometer (CieLab-System) or a chair-side color measurement device (VITA EasyShade), respectively. Data were analyzed using three-, two-, and one-way ANOVA, a Chi(2)-test, and a Wilson approach (p < 0.05). The measurements with EasyShade showed A2 for VITA Mark II, A3.5 for VITA Enamic, B2 for LAVA Ultimate, and B3 for IPS e.max CAD. LabE-values showed significant differences between the tested veneering materials (p < 0.001). CieLab-System and VITA EasyShade parameters of the different assemblies showed a significant impact of core (p < 0.001), veneering material (p < 0.001), and thickness of the veneering material (p < 0.001). PEEK as core material showed comparable outcomes as compared to ZrO2 and CoCrMo, with respect to CieLab-System parameters for each veneering material. The relative frequency of the measured VITA EasyShade parameters regarding PEEK cores also showed comparable results as compared to the gold standard CoCrMo, regardless of the veneering material used
Depression and vaccination behavior in patients with chronic physical illness – A cross-sectional survey
Objective: Chronically ill are vulnerable to vaccine preventable infections. Consequently, their vaccination behavior is highly relevant. Depressive comorbidities are frequent in these patients. Furthermore, these patients are mainly diagnosed, treated and vaccinated in primary care. Therefore, we aimed to investigate the associations between depression and vaccination behavior (COVID-19 and influenza) in adult chronically ill primary care patients. Methods: In a cross-sectional survey, we examined depression (PHQ9), psychological antecedents of vaccinations (Confidence and Constraints), health care utilization, and vaccination status. Based on an effect model, descriptive statistics and mixed linear/logistic models were calculated. (German Clinical Trials Register, DRKS00030042). Results: n = 795 patients were analyzed. Both psychological antecedents of vaccinations (Confidence and Constraints) mediated a negative association between depression and vaccination behavior, healthcare utilization mediated a positive association. The total effect of depression was negligible. Conclusions: As the effects of vaccination readiness and healthcare utilization are opposing, different total effects depending on the study population are possible. Further studies are needed to investigate additional predictors of vaccination behavior. Practice implications: We suggest tackling vaccine acceptance in chronically ill through increasing confidence using communication-based interventions, for which primary care is the suitable setting. Constraints might be reduced by reminder and recall systems
An Open-System Quantum Simulator with Trapped Ions
The control of quantum systems is of fundamental scientific interest and
promises powerful applications and technologies. Impressive progress has been
achieved in isolating the systems from the environment and coherently
controlling their dynamics, as demonstrated by the creation and manipulation of
entanglement in various physical systems. However, for open quantum systems,
engineering the dynamics of many particles by a controlled coupling to an
environment remains largely unexplored. Here we report the first realization of
a toolbox for simulating an open quantum system with up to five qubits. Using a
quantum computing architecture with trapped ions, we combine multi-qubit gates
with optical pumping to implement coherent operations and dissipative
processes. We illustrate this engineering by the dissipative preparation of
entangled states, the simulation of coherent many-body spin interactions and
the quantum non-demolition measurement of multi-qubit observables. By adding
controlled dissipation to coherent operations, this work offers novel prospects
for open-system quantum simulation and computation.Comment: Pre-review submission to Nature. For an updated and final version see
publication. Manuscript + Supplementary Informatio
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