Perturbative QCD study of BsB_s decays to a pseudoscalar meson and a tensor meson

We study two-body hadronic $B_s\to PT$ decays, with $P (T)$ being a light pseudoscalar (tensor) meson, in the perturbative QCD approach. The CP-averaged branching ratios and the direct CP asymmetries of the $\Delta S=0$ modes are predicted, where $\Delta S$ is the difference between the strange numbers of final and initial states. We also define and calculate experimental observables for the $\Delta S=1$ modes under the $B_s^0-\bar{B}_s^0$ mixing, including CP averaged branching ratios, time-integrated CP asymmetries, and the CP observables $C_{f}$, $D_{f}$ and $S_{f}$. Results are compared to the $B_s\to PV$ ones in the literature, and to the $B\to PT$ ones, which indicate considerable U-spin symmetry breaking. Our work provides theoretical predictions for the $B_s\to PT$ decays for the first time, some of which will be potentially measurable at future experiments.Comment: 6 pages, 1 figur

Zener Tunneling in Semiconducting Nanotube and Graphene Nanoribbon p-n Junctions

A theory is developed for interband tunneling in semiconducting carbon nanotube and graphene nanoribbon p-n junction diodes. Characteristic length and energy scales that dictate the tunneling probabilities and currents are evaluated. By comparing the Zener tunneling processes in these structures to traditional group IV and III-V semiconductors, it is proved that for identical bandgaps, carbon based 1D structures have higher tunneling probabilities. The high tunneling current magnitudes for 1D carbon structures suggest the distinct feasibility of high-performance tunneling-based field-effect transistors.Comment: 4 Pages, 2 Figure

Synthetic studies towards tetrahydroxanthone natural products

Tetrahydroxanthones are a large class of natural products that contain a partially reduced xanthone moiety. These compounds exist in both monomeric and dimeric forms in nature. A concise retro-biomimetic synthetic approach to monomeric tetrahydroxanthone natural products has been developed. The key transformation involves vinylogous addition of siloxyfurans to benzopyryliums to access chromone lactone precursors which is followed by late-stage Dieckmann cyclization to the tetrahydroxanthone core. Application of this methodology led to efficient syntheses of blennolides B, C, and its stereoisomer epi-blennolide C. Synthetic efforts towards dimeric tetrahydroxanthones, including 2,2'-biaryl dimer secalonic acid D, have been pursued as well. We developed an efficient kinetic resolution using homobenzotetramisole (HBTM) catalysis to obtain enantiopure tetrahydroxanthones. The development of a mild, copper-mediated dimerization of stannyl tetrahydroxanthones also allowed access to enantiopure 2,2'-linked dimeric tetrahydroxanthones including secalonic acids A and D. After successful syntheses of secalonic acids A and D, we also applied the methodologies developed towards a synthesis of the axially chiral dimer rugulotrosin A. An enantiopure monomer was prepared in gram-scale by applying our previously developed methodology. The atropselective synthesis of rugulotrosin A was achieved via a one-pot Sukuzi dimerization with chiral palladium precatalyst. A rationale for point-to-axial chirality transfer observed in the key dimerization step has been developed. This key transformation led to the successful 7-step syntheses of rugulotrosin A, its enantiomer, and the atropisomer. Finally, we further exploited the kinetic resolution using homobenzotetramisole catalysts which successfully led to a unified strategy for syntheses of both the 2,4'-linked and 4',4'-linked secalonic acid derivatives. The isomerization properties of 2,2'-linked, 2,4'-linked, and 4,4'-linked secalonic acids was also studied in an effort to understand the "shapeshifting" properties of the dimeric tetrahydroxanthone family

A Software-Defined-Radio Platform for Multiple-Input-Multiple-Output Over-The-Air Measurement

This paper presents a 2 × 2 multiple-inputmultiple-output over-the-air (MIMO OTA) measurement system with user-programmable, reconfigurable and real-time signal processing field-programmable gate arrays (FPGAs)-based software-defined radio (SDR) capability. Signal generation and analysis as well as channel emulation are all implemented using vector signal transceivers (VSTs). As a demonstration, we performed the Third Generation Partnership Project (3GPP) two-stage MIMO OTA conducted test using a downlink time division long-term evolution (TD-LTE) duplex scheme. The channel emulation was operated in a stochastic mode. Some preliminary results of the system verification are shown