Confined surface waves in layered dielectric materials

We demonstrate deep subwavelength confinement of surface phonon-polaritons in silicon carbide by capping the crystal with nanometric layers of MoS2. Near-field nano-imaging shows 85 time surface wave confinement in comparison with free-space wavelength of 11.15 micrometers

Deep Learning-Based Rapid Flood Inundation Modeling for Flat Floodplains With Complex Flow Paths

Flood inundation emulation models based on deep neural networks have been developed to overcome the computational burden of two-dimensional (2D) hydrodynamic models. Challenges remain for flat and complex floodplains where many anabranches form during flood events. In this study, we propose a new approach to simulate the temporal and spatial variation of flood inundation for a floodplain with complex flow paths. A U-Net-based spatial reduction and reconstruction method (USRR) is used to find representative locations on the floodplain with complex flow paths. The water depths at these locations are simulated using one-dimensional convolutional neural network (1D-CNN) models, which are well-suited to handling multivariate timeseries inputs. The flood surface is then reconstructed using the USRR method and the simulated flood depths at the representative locations. The combined 1D-CNN and USRR method is compared with a previously developed approach based on the long short-term memory recurrent neural network (LSTM) models and a 2D linear interpolation-based SRR method. Compared to the LSTM model, the 1D-CNN model is not only more accurate, but also takes less time to develop. Although both surface reconstruction methods take <1 s to produce an inundation map for a specific point in time, the USRR method is more accurate than the SRR method, leading to an increase of 5.6% in the proportion of correctly detected inundation area. The combination of 1D-CNN and USRR can detect over 95% of the inundated area simulated using a 2D hydrodynamic model but is 98 times faster.Yuerong Zhou, Wenyan Wu, Rory Nathan, and Q. J. Wan

Development of a Fast and Accurate Hybrid Model for Floodplain Inundation Simulations

High computational cost is often the most limiting factor when running high-resolution hydrodynamic models to simulate spatial-temporal flood inundation behavior. To address this issue, a recent study introduced the hybrid Low-fidelity, Spatial analysis, and Gaussian Process learning (LSG) model. The LSG model simulates the dynamic behavior of flood inundation extent by upskilling simulations from a low-resolution hydrodynamic model through Empirical Orthogonal Function (EOF) analysis and Sparse Gaussian Process learning. However, information on flood extent alone is often not sufficient to provide accurate flood risk assessments. In addition, the LSG model has only been tested on hydrodynamic models with structured grids, while modern hydrodynamic models tend to use unstructured grids. This study therefore further develops the LSG model to simulate water depth as well as flood extent and demonstrates its efficacy as a surrogate for a high-resolution hydrodynamic model with an unstructured grid. The further developed LSG model is evaluated on the flat and complex Chowilla floodplain of the Murray River in Australia and accurately predicts both depth and extent of the flood inundation, while being 12 times more computationally efficient than a high-resolution hydrodynamic model. In addition, it has been found that weighting before the EOF analysis can compensate for the varying grid cell sizes in an unstructured grid and the inundation extent should be predicted from an extent-based LSG model rather than deriving it from water depth predictions.Niels Fraehr, Quan J. Wang, Wenyan Wu, and Rory Natha

The first-order phase transition between dimerized-antiferromagnetic and uniform-antiferromagnetic phases in Cu_(1-x)M_xGeO_3

We have performed detailed magnetic susceptibility measurements as well as synchrotron x-ray diffraction studies to determine the temperature vs concentration ($T$ - $x$) phase diagram of Cu${}_{1-x}$Mg${}_x$GeO${}_3$. We observe clear double peaks in the magnetic susceptibility implying two antiferromagnetic (AF) transition temperatures in samples with Mg concentrations in the range 0.0237 $\le x \le$ 0.0271. We also observe a drastic change in the inverse correlation length in this concentration range by x-ray diffraction. The drastic change of the AF transition temperature as well as the disappearance of the spin-Peierls (SP) phase have been clarified; these results are consistent with a first-order phase transition between dimerized AF (D-AF) and uniform AF (U-AF) phases as reported by T. Masuda {\it et al.} \lbrack Phys. Rev. Lett. {\bf 80}, 4566 (1998)\rbrack. The $T$ - $x$ phase diagram of Cu${}_{1-x}$Zn${}_x$GeO${}_3$ is similar to that of Cu${}_{1-x}$Mg${}_x$GeO${}_3$, which suggests that the present phase transition is universal for Cu${}_{1-x}M_{x}$GeO${}_3$.Comment: 7 pages, 5 figures. submitted to PR

Reversed Drifting Quasi-periodic Pulsating Structure in an X1.3 Solar Flare on 2005 July 30

Based on the analysis of the microwave observations at frequency of 2.60 -- 3.80 GHz in a solar X1.3 flare event observed at Solar Broadband RadioSpectrometer in Huairou (SBRS/Huairou) on 2005 July 30, an interesting reversed drifting quasi-periodic pulsating structure (R-DPS) is confirmed. The R-DPS is mainly composed of two drifting pulsating components: one is a relatively slow very short-period pulsation (VSP) with period of about 130 -- 170 ms, the other is a relatively fast VSP with period of about 70 -- 80 ms. The R-DPS has a weak left-handed circular polarization. Based on the synthetic investigations of Reuven Ramaty High Energy Solar Spectroscopic Imaging (RHESSI) hard X-ray, Geostationary Operational Environmental Satellite (GOES) soft X-ray observation, and magnetic field extrapolation, we suggest the R-DPS possibly reflects flaring dynamic processes of the emission source regions

A note on Friedmann equation of FRW universe in deformed Horava-Lifshitz gravity from entropic force

With entropic interpretation of gravity proposed by Verlinde, we obtain the Friedmann equation of the Friedmann-Robertson-Walker universe for the deformed Ho\v{r}ava-Lifshitz gravity. It is shown that, when the parameter of Ho\v{r}ava-Lifshitz gravity $\omega\rightarrow \infty$, the modified Friedmann equation will go back to the one in Einstein gravity. This results may imply that the entropic interpretation of gravity is effective for the deformed Ho\v{r}ava-Lifshitz gravity.Comment: 9 pages, no figure

Nernst Effect and Anomalous Transport in Cuprates: A Preformed-Pair Alternative to the Vortex Scenario

We address those puzzling experiments in underdoped high $T_c$ superconductors which have been associated with normal state "vortices" and show these data can be understood as deriving from preformed pairs with onset temperature $T^* > T_c$. For uncorrelated bosons in small magnetic fields, and arbitrary $T^*/T_c$, we present the exact contribution to \textit{all} transport coefficients. In the overdoped regime our results reduce to those of standard fluctuation theories ($T^*\approx T_c$). Semi-quantitative agreement with Nernst, ac conductivity and diamagnetic measurements is quite reasonable.Comment: 9 pages, 4 figures; Title, abstract and contents modified, new references added, figures changed, one more figure added; to be published on PR

Multi-timescale Solar Cycles and the Possible Implications

Based on analysis of the annual averaged relative sunspot number (ASN) during 1700 -- 2009, 3 kinds of solar cycles are confirmed: the well-known 11-yr cycle (Schwabe cycle), 103-yr secular cycle (numbered as G1, G2, G3, and G4, respectively since 1700); and 51.5-yr Cycle. From similarities, an extrapolation of forthcoming solar cycles is made, and found that the solar cycle 24 will be a relative long and weak Schwabe cycle, which may reach to its apex around 2012-2014 in the vale between G3 and G4. Additionally, most Schwabe cycles are asymmetric with rapidly rising-phases and slowly decay-phases. The comparisons between ASN and the annual flare numbers with different GOES classes (C-class, M-class, X-class, and super-flare, here super-flare is defined as $\geq$ X10.0) and the annal averaged radio flux at frequency of 2.84 GHz indicate that solar flares have a tendency: the more powerful of the flare, the later it takes place after the onset of the Schwabe cycle, and most powerful flares take place in the decay phase of Schwabe cycle. Some discussions on the origin of solar cycles are presented.Comment: 8 pages, 4 figure

Comparison of endosperm amyloplast development and degradation in waxy and non-waxy wheat

The waxy wheat shows special starch quality due to high amylopectin content. However, little information is available concerning the development and degradation of amyloplast from waxy wheat endosperm. To address this problem, waxy wheat variety, Yangnuo 1, and a non-waxy wheat variety, Yangmai 13, were chosen to investigate the development and degradation of endosperm amyloplast during wheat caryopsis development and germination stage respectively using histochemical staining and light microscopy. Changes of morphology, the soluble sugar and total starch content were indistinguishable in the process of caryopsis development of two wheat varieties. The developing endosperm of non-waxy was stained blue-black by I2-KI while the endosperm of waxy wheat was stained reddish-brown, but the pericarp of waxy and non-waxy wheat was stained blue-black. In contrast to nonwaxy wheat, endosperm amyloplast of waxy wheat had better development status and higher proportion of small amyloplast. During seed germination many small dissolution pores appeared on the surface of endosperm amyloplast and the pores became bigger and deeper until amyloplast disintegrated. The rate of degradation of waxy wheat endosperm amyloplast was faster than non-waxy wheat. Our results may also be helpful to the use of waxy starch in food and nonfood industry