A boundary-temperature-controlled epitaxy, where the growth temperature of InN is controlled at its maximum, is used to obtain high-electronmobility InN layers on sapphire substrates by molecular beam epitaxy. The Hall-effect measurement shows a recorded electron mobility of 3280 cm 2 V À1 s À1 and a residual electron concentration of 1:47 Â 10 17 cm À3 at room temperature. The enhanced electron mobility and reduced residual electron concentration are mainly due to the reduction of threading dislocation density. The obtained Hall mobilities are in good agreement with the theoretical modelling by the ensemble Monte Carlo simulation. #

Electrically manipulating electron spins based on Rashba spin-orbit coupling (SOC) is a key pathway for applications of spintronics and spin-based quantum computation. Two-dimensional electron systems (2DESs) offer a particularly important SOC platform, where spin polarization can be tuned with an electric field perpendicular to the 2DES. Here, by measuring the tunable circular photogalvanic effect (CPGE), we present a room-temperature electric-field-modulated spin splitting of surface electrons on InN epitaxial thin films that is a good candidate to realize spin injection. The surface band bending and resulting CPGE current are successfully modulated by ionic liquid gating within an electric double-layer transistor configuration. The clear gate voltage dependence of CPGE current indicates that the spin splitting of the surface electron accumulation layer is effectively tuned, providing a way to modulate the injected spin polarization in potential spintronic devices.

We consider the problem to reconstruct a wave speed c ∈ C ∞ (M ) in a domain M ⊂ R n from acoustic boundary measurements modelled by the hyperbolic Dirichlet-to-Neumann map Λ. We introduce a reconstruction formula for c that is based on the Boundary Control method and incorporates features also from the complex geometric optics solutions approach. Moreover, we show that the reconstruction formula is locally Lipschitz stable for a low frequency component of c −2 under the assumption that the Riemannian manifold (M, c −2 dx 2 ) has a strictly convex function with no critical points. That is, we show that for all bounded C 2 neighborhoods U of c, there is a C 1 neighborhood V of c and constants C, R > 0 such thatfor all c ∈ U ∩ V , where Λ is the Dirichlet-to-Neumann map corresponding to the wave speed c and · * is a norm capturing certain regularity properties of the Dirichlet-to-Neumann maps.1991 Mathematics Subject Classification. Primary: 35R30.

The dedicated murine PET (MuPET) scanner is a high-resolution, high-sensitivity, and low-cost preclinical PET camera designed and manufactured at our laboratory. In this article, we report its performance according to the NU 4-2008 standards of the National Electrical Manufacturers Association (NEMA). We also report the results of additional phantom and mouse studies. Methods: The MuPET scanner, which is integrated with a CT camera, is based on the photomultiplier-quadrant-sharing concept and comprises 180 blocks of 13 · 13 lutetium yttrium oxyorthosilicate crystals (1.24 · 1.4 · 9.5 mm 3 ) and 210 low-cost 19-mm photomultipliers. The camera has 78 detector rings, with an 11.6-cm axial field of view and a ring diameter of 16.6 cm. We measured the energy resolution, scatter fraction, sensitivity, spatial resolution, and counting rate performance of the scanner. In addition, we scanned the NEMA image-quality phantom, Micro Deluxe and Ultra-Micro Hot Spot phantoms, and 2 healthy mice. Results: The system average energy resolution was 14% at 511 keV. The average spatial resolution at the center of the field of view was about 1.2 mm, improving to 0.8 mm and remaining below 1.2 mm in the central 6-cm field of view when a resolution-recovery method was used. The absolute sensitivity of the camera was 6.38% for an energy window of 350-650 keV and a coincidence timing window of 3.4 ns. The system scatter fraction was 11.9% for the NEMA mouselike phantom and 28% for the ratlike phantom. The maximum noise-equivalent counting rate was 1,100 at 57 MBq for the mouselike phantom and 352 kcps at 65 MBq for the ratlike phantom. The 1-mm fillable rod was clearly observable using the NEMA image-quality phantom. The images of the Ultra-Micro Hot Spot phantom also showed the 1-mm hot rods. In the mouse studies, both the left and right ventricle walls were clearly observable, as were the Harderian glands. Conclusion: The MuPET camera has excellent resolution, sensitivity, counting rate, and imaging performance. The data show it is a powerful scanner for preclinical animal study and pharmaceutical development. Smal l-animal PET has been widely used in a broad range of applications in the field of biology and pharmaceutical development (1). Because of the small physical dimensions of rodents, achieving spatial resolution and detection sensitivity adequate to study small structures and the low concentration of receptors is challenging. In addition, to make the in vivo molecular imaging capability of PET accessible to more biology and genetics laboratories, thus facilitating the integration of biologic research and clinical medicine, lower camera-production costs are also needed.A preclinical dedicated murine PET (MuPET) camera has been designed and constructed at the University of Texas M.D. Anderson Cancer Center (2). It has been integrated with a CT camera into a compact gantry. The MuPET camera combines the advantages of a lower production cost with high resolution and high sensitivity. In this work, we report on the scanner's perfor...