Evaluation of the Rayleigh-Gans approximation for microwave scattering by rimed snowflakes

We have evaluated of the applicability of the Rayleigh–Gans (RGA) and Self-Similar Rayleigh–Gans (SSRGA) approximations for microwave scattering by rimed snowflakes. This study extends previous findings that showed that, for unrimed snowflakes, the RGA is in good agreement with the discrete dipole approximation (DDA), which we used as a reference method. When riming is introduced, the RGA-derived scattering properties of individual snowflakes deviate significantly — up to 20–25 dB for the backscattering cross section at the W-band — from the corresponding DDA results. In contrast, the average scattering properties given by RGA are in good agreement with DDA for all but the most heavily rimed snowflakes: the mean bias in the backscattering cross section rarely exceeds 1 dB for light and moderate riming. We also found that an adjustment that accounts for the nonspherical shapes of the ice crystals can help eliminate a small constant bias found in RGA in earlier studies. The SSRGA approximates the RGA results with good accuracy at all degrees of riming, indicating that it, too, can be used with up to moderately rimed snowflakes

Properties of the conditionally filtered equations: Conservation, normal modes, and variational formulation

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this record.Conditionally filtered equations have recently been proposed as a basis for modelling the atmospheric boundary layer and convection. Conditional filtering decomposes the fluid into a number of categories or components, such as convective updrafts and the background environment, and derives governing equations for the dynamics of each component. Because of the novelty and unfamiliarity of these equations, it is important to establish some of their physical and mathematical properties, and to examine whether their solutions might behave in counter-intuitive or even unphysical ways. It is also important to understand the properties of the equations in order to develop suitable numerical solution methods. The conditionally filtered equations are shown to have conservation laws for mass, entropy, momentum or axial angular momentum, energy, and potential vorticity. The normal modes of the conditionally filtered equations include the usual acoustic, inertio-gravity, and Rossby modes of the standard compressible Euler equations. In addition, they posses modes with different perturbations in the different fluid components that resemble gravity modes and inertial modes but with zero pressure perturbation. These modes make no contribution to the total filter-scale fluid motion, and their amplitude diminishes as the filter scale diminishes. Finally, it is shown that the conditionally filtered equations have a natural variational formulation, which can be used as a basis for systematically deriving consistent approximations.We are grateful to two anonymous reviewers for their constructive comments on an earlier version of this paper. This work was funded by the Natural Environment Research Council under grant NE/N013123/1 as part of the ParaCon programme

Toward Automatic Label-Free Whispering Gallery Modes Biodetection with a Quantum Dot-Coated Microsphere Population

We explore a new calibration-free approach to biodetection based on whispering gallery modes (WGMs) without a reference measure and relative shifts. Thus, the requirement to keep track of the sensor position is removed, and a freely moving population of fluorophore-doped polystyrene microspheres can now fulfill this role of sensing resonator. Breaking free from fixed surface-based biosensing promotes adhesion between the microsphere sensors and the analytes since both can now be thoroughly mixed. The 70-nm-wide spectrum of green fluorescent microbeads allows us to monitor over 20 WGMs simultaneously without needing evanescent light coupling into the microspheres, hence enabling remote sensing. Since the exact radius of each microsphere is unknown a priori, it requires algorithmic analyses to obtain a reliable result for the refractive index of a solution. We first test our approach with different solutions of alcohol in water obtaining 3 × 10−4 precision on the refractive index at lower concentrations. Then, the solutions of bacterial spores in water yield clear evidence of biodetection in the statistical analysis of WGMs from 50 microspheres. To extend the fluorescence spectral range of our WGM sensors, we present preliminary results on coating microspheres with CdSe/ZnS quantum dots

Gold nanorods for diagnostics and photothermal therapy of cancer

This chapter describes the application of gold nanorods for cancer diagnostics and photothermal therapy. The optical properties of gold nanorods are summarized at the beginning, including optical absorption and scattering properties, plasmonic field enhancement, and photothermal properties. Cancer diagnostic approaches cover light scattering cancer imaging, surface plasmon resonance detection, and surface-enhanced Raman scattering detection. Photothermal therapy includes both in vitro and in vivo studies, followed by combination therapy with chemotherapy and photodynamic therapy. At the end, biodistribution of gold nanorods with and without targeting ligands is described