Unconventional Homogeneous and Heterogeneous Asymmetric Organocatalysis

This work describes developments of i) a catalytic asymmetric protonation reaction of ketene dithioacetals using a chiral Brønsted acid as a catalyst and ii) a heterogeneous catalysis using textiles as solid support materials. First, for an asymmetric protonation reaction of ketene dithioacetals, we have disclosed a facile preparation of various lactones and hydrocoumarins. The formation and application of ketene dithioacetals was well demonstrated and fully chracterized. The key enantiodetermining step, an asymmetric protonation reaction, was smoothly catalyzed by BINOL‐based Brønsted acids. The desired dithioacetal protected hydrocoumarins were obtained in good yields and high enantioselectivities. The utility of the obtained enantioenriched products were further demonstrated by synthesizing a natural product and conducting a large scale reaction. Secondly, we have successfully demonstrated a facile preparation of textile‐immobilized heterogeneous catalysts. As a general method, photochemical reaction conditions can provide diverse solidsupported organocatalysts within one‐step from inexpensive starting materials. Further applications and mechanistic studies revealed the high efficiency and application potential of the presented methodology

Separation in Stability Analysis of Piecewise Linear Systems in Discrete Time

Abstract. Stability analysis of piecewise linear systems, without affine terms, consists of the problem of finding maximal stabilizing sets of switching paths among possible system coefficients and that of obtaining a sequence of state-space partitions in the order of increasing refinement. Exploiting the fact that these two problems can be solved separately, one can find subsets of the state space such that the piecewise linear system restricted to these sets is uniformly exponentially stable

Loophole-free Bell test for continuous variables via wave and particle correlations

We derive two classes of multi-mode Bell inequalities under local realistic assumptions, which are violated only by the entangled states negative under partial transposition in accordance with the Peres conjecture. Remarkably, the failure of local realism can be manifested by exploiting wave and particle correlations of readily accessible continuous-variable states, with very large violation of inequalities insensitive to detector-efficiency, which makes a strong case for a loophole-free test.Comment: 4 pages, published versio

Reply to the comment on "Loophole-free Bell test for continuous variables via wave and particle correlations"

In a recent note, Cavalcanti and Scarani (CS) constructed a counter local-hidden-variable model to explain the violation of our inequalities in Phys. Rev. Lett. 105, 170404 (2010). Here, we briefly discuss some issues in response to the comments raised by CS.Comment: published versio

Proposal for direct measurement of concurrence via visibility in a cavity QED system

An experimental scheme is proposed that allows direct measurement of the concurrence of a two-qubit cavity system. It is based on the cavity-QED technology using atoms as flying qubits and relies on the identity of the two-particle visibility of the atomic probability with the concurrence of the cavity system. The scheme works for any arbitrary pure initial state of the two-qubit cavity system.Comment: To appear in Physical Review A as a Rapid Comminicatio

Adaptive channel estimation in WCDMA STTD systems

The receiver performance with the use of a space time transmit diversity (STTD) scheme is more susceptible to the accuracy of channel estimate than that without the use of the STTD scheme since the despreading signals suffer from the effect of crosstalk and the transmit power is equally divided into multiple transmit antennas. As a result, the efficiency of channel estimation in the WCDMA STTD system becomes an important issue more than that in the non-STTD system. In this paper, an adaptive channel estimator (ACE) is designed to mitigate the performance degradation due to inaccurate channel estimation. Numerical results show that the performance improvement significantly increases with the use of the proposed ACE, particularly when the channel condition becomes worse

Optimum pilot pattern for channel estimation in OFDM systems

The performance of channel estimation in orthogonal frequency division multiplexing (OFDM) systems significantly depends on the pilot signal, which is usually scattered in time and frequency domains. For a given pilot density, the authors optimally design the pilot pattern so as to minimize the mean squared error (MSE) of the channel estimate with the use of a general interpolator. The analytic results are verified by computer simulation

Optimum pilot pattern for MMSE channel estimation in single-carrier MIMO systems

The minimum mean squared error (MMSE) channel estimator (CE) can provide receiver performance better than the least square (LS) CE. However, the MMSE CE usually uses a pilot pattern optimally designed for the LS CE. In this paper, we derive an optimum pilot pattern for the MMSE CE in single-carrier MIMO systems assuming that both the transmitter and receiver know the average channel information, such as the channel correlation matrix and signal to interference and noise power ratio. Analytic and simulation results show that the MMSE CE with the use of the proposed pilot pattern can reduce the MSE compared to the use of one optimized for the LS CEThis work was supported (in part) by the Ministry of Information & Communications, Korea, under the Information Technology Research Center (ITRC) Support Program