Dirac Neutrino Masses in NCG

Several models in NCG with mild changes to the standard model(SM)are introduced to discuss the neutrino mass problem. We use two constraints, Poincar$\acute{e}$ duality and gauge anomaly free, to discuss the possibility of containing right-handed neutrinos in them. Our work shows that no model in this paper, with each generation containing a right-handed neutrino, can satisfy these two constraints in the same time. So, to consist with neutrino oscillation experiment results, maybe fundamental changes to the present version of NCG are usually needed to include Dirac massive neutrinos.Comment: 14 page

Photoacoustic tomography and sensing in biomedicine

Photoacoustics has been broadly studied in biomedicine, for both human and small animal tissues. Photoacoustics uniquely combines the absorption contrast of light or radio frequency waves with ultrasound resolution. Moreover, it is non-ionizing and non-invasive, and is the fastest growing new biomedical method, with clinical applications on the way. This review provides a brief recap of recent developments in photoacoustics in biomedicine, from basic principles to applications. The emphasized areas include the new imaging modalities, hybrid detection methods, photoacoustic contrast agents and the photoacoustic Doppler effect, as well as translational research topics

Photoacoustic tomography of the mouse cerebral cortex with a high-numerical-aperture-based virtual point detector

The mouse cerebral cortex was imaged in situ by photoacoustic tomography (PAT). Instead of a flat ultrasonic transducer, a virtual point detector based on a high numerical aperture (NA), positively focused transducer was used. This virtual point detector has a wide omnidirectional acceptance angle, a high sensitivity, and a negligible aperture effect. In addition, the virtual point detector can be located much more closely to the object during the detection. Compared with a finite-size flat transducer, images generated by using this virtual point detector have both uniform signal-to-noise ratio (SNR) and resolution

Improving the image quality of photoacoustic tomography (PAT) by using a negative acoustic lens

Although a small point ultrasound transducer has a wide acceptance angle, its signal-to-noise (SNR) is low due to the high thermal-noise-induced electric voltages in the transducer, which is a result of its small active area. By contrast, a finite size flat transducer has high sensitivity (good SNR), but the acceptance angle is generally small, which limits its application in reconstruction-based photoacoustic tomography (PAT). In this paper, we report a negative lens concept to increase the acceptance angle for a flat transducer. We also provide phantom experiments that demonstrate this concept can greatly increase the detection region for PAT and without losing sensitivity

Radiative interactions: I. Light scattering and emission from irregular particles. II. Time dependent radiative coupling of an atmosphere-ocean system

In the first part of this dissertation, radiative interactions with single irregular particles are simulated. We first introduce the basic method and techniques of Finite- Difference Time-Domain method(FDTD), which is a powerful method to numerically solve Maxwell's equations with high accuracy. To improve the efficiency of FDTD, we also develop a parallel FDTD code. Since FDTD can simulate light scattering by arbitrary shape and compositions, we study several radiative interaction cases for single particles in an external plane parallel light source: the surface roughness effects on the scattering, electric and magnetic energy density distribution in irregular particles, and backscattered Mueller images. We also develop an innovative and accurate method to simulate the infinitesimal electric dipole radiation from inside a particle with arbitrary shape and composition. Our research and results are very important to study light scattering by irregular particles, Raman scattering and fluorescence. In the second part of the dissertation, we study radiative interactions in an atmosphere-ocean system. By using the so called Matrix operator method, not only the radiance of the radiation field, but also the polarization of the radiation field are obtained. Given the single layer information for the atmosphere, time dependent ocean surface shapes, and the ocean with no interface, the Matrix operator method couples these three layers and provides both the radiance and polarization reaching a certain detector in the time domain, which are essential for atmospheric science and oceanography. Several simple cases are studied by this method to demonstrate its accuracy and robustness. We also show the most difficulties in this method and discuss what one need to do in future research works

Fast and Robust Deconvolution-Based Image Reconstruction for Photoacoustic Tomography in Circular Geometry: Experimental Validation

Photoacoustic tomography (PAT) is a fast-developing biomedical imaging technology suitable for in vivo imaging. PAT in spherical or circular geometry gives good image resolution yet is slow or expensive in signal acquisition and image formation. Reducing the number of detection angles can ameliorate such issues, usually at the expense of image quality. This paper introduces a deconvolution-based algorithm that models the imaging process as a linear and shift-invariant system. As demonstrated by the in vivo experiment, this algorithm not only runs much faster than the back-projection algorithm but also shows stronger robustness in that it provides better image quality when detection angles are sparse. Therefore, this algorithm promises to enable real-time PAT in circular geometry