1,571 research outputs found
Quantum interference induced by multiple Landau-Zener transitions in a strongly driven rf-SQUID qubit
We irradiated an rf-SQUID qubit with large-amplitude and high frequency
electromagnetic field. Population transitions between macroscopic distinctive
quantum states due to Landau-Zener transitions at energy-level avoided
crossings were observed. The qubit population on the excited states as a
function of flux detuning and microwave power exhibits interference patterns.
Some novel features are found in the interference and a model based on rate
equations can well address the features.Comment: 6 pages, 3 figures, comments are welcom
Dielectric Property of MoS2 Crystal in Terahertz and Visible Region
Two-dimensional materials such as MoS2 have attracted much attention in
recent years due to their fascinating optoelectronic properties. Dielectric
property of MoS2 is desired for the optoelectronic application. In this paper,
terahertz (THz) time-domain spectroscopy and ellipsometry technology are
employed to investigate the dielectric response of MoS2 crystal in THz and
visible region. The real and imaginary parts of the complex dielectric constant
of MoS2 crystal are found to follow a Drude model in THz region, which is due
to the intrinsic carrier absorption. In visible region, the general trend of
the complex dielectric constant is found to be described with a Lorentz model,
while two remarkable peaks are observed at 1.85 and 2.03 eV, which have been
attributed to the splitting arising from the combined effect of interlayer
coupling and spin-orbit coupling. This work affords the fundamental dielectric
data for the future optoelectronic applications with MoS2.Comment: 6 page
Occurrence-habitat mismatching and niche truncation when modelling distributions affected by anthropogenic range contractions
Aims Human-induced pressures such as deforestation cause anthropogenic range contractions (ARCs). Such contractions present dynamic distributions that may engender data misrepresentations within species distribution models. The temporal bias of occurrence data-where occurrences represent distributions before (past bias) or after (recent bias) ARCs-underpins these data misrepresentations. Occurrence-habitat mismatching results when occurrences sampled before contractions are modelled with contemporary anthropogenic variables; niche truncation results when occurrences sampled after contractions are modelled without anthropogenic variables. Our understanding of their independent and interactive effects on model performance remains incomplete but is vital for developing good modelling protocols. Through a virtual ecologist approach, we demonstrate how these data misrepresentations manifest and investigate their effects on model performance. Location Virtual Southeast Asia. Methods Using 100 virtual species, we simulated ARCs with 100-year land-use data and generated temporally biased (past and recent) occurrence datasets. We modelled datasets with and without a contemporary land-use variable (conventional modelling protocols) and with a temporally dynamic land-use variable. We evaluated each model's ability to predict historical and contemporary distributions. Results Greater ARC resulted in greater occurrence-habitat mismatching for datasets with past bias and greater niche truncation for datasets with recent bias. Occurrence-habitat mismatching prevented models with the contemporary land-use variable from predicting anthropogenic-related absences, causing overpredictions of contemporary distributions. Although niche truncation caused underpredictions of historical distributions (environmentally suitable habitats), incorporating the contemporary land-use variable resolved these underpredictions, even when mismatching occurred. Models with the temporally dynamic land-use variable consistently outperformed models without. Main conclusions We showed how these data misrepresentations can degrade model performance, undermining their use for empirical research and conservation science. Given the ubiquity of ARCs, these data misrepresentations are likely inherent to most datasets. Therefore, we present a three-step strategy for handling data misrepresentations: maximize the temporal range of anthropogenic predictors, exclude mismatched occurrences and test for residual data misrepresentations.Peer reviewe
Investigation of enhanced second harmonic generation in laser-induced air plasma
We report a systematic investigation into the processes behind a near
hundredfold enhanced second harmonic wave generated from a laser-induced air
plasma, by examining the temporal dynamics of the frequency conversion
processes, and the polarization of the emitted second harmonic beam. Contrary
to typical nonlinear optical processes, the enhanced second harmonic generation
efficiency is only observed within a sub-picosecond time window and found to be
nearly constant across fundamental pulse durations spanning from 0.1 ps to over
2 ps. We further demonstrate that with the adopted orthogonal pump-probe
configuration, the polarization of second harmonic field exhibits a complex
dependence on the polarization of both input fundamental beams, contrasting
with most of the previous experiments with a single-beam geometry
- …