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Comment: 5 pages, 3 figures
We study the quantum-jump-based feedback control on the entanglement shared between two qubits with one of them subject to decoherence, while the other qubit is under the control. This situation is very relevant to a quantum system consisting of nuclear and electron spins in solid states. The possibility to prolong the coherence time of the dissipative qubit is also explored. Numerical simulations show that the quantum-jump-based feedback control can improve the entanglement between the qubits and prolong the coherence time for the qubit subject directly to decoherence.
The phosphoenolpyruvate carboxykinase in Escherichia coli (encoded by pck) catalyzes the conversion from oxaloacetate (OAA) to phosphoenolpyruvate under gluconeogenic conditions. We report here the characterization of two mutant alleles, pck-51 and pck-53, both of which are point mutations leading to single amino acid changes (D to N at position 268 and G to S at position 284, respectively). Pck51 is an altered-activity mutant that catalyzes the conversion from OAA to pyruvate (OAA decarboxylase activity). This new activity was not detected from the wild-type Pck, and it complements the pck null mutation only in a pps+ background. Pck53 is a reduced-activity mutant that complements the pck null mutation in a strain-dependent fashion.
The development of Sendai virus-specific cytotoxic T-lymphocyte (CTL) effectors and precursors (CTLp) has been compared for mice that are homozygous (-/-) for a disruption of the H-2I-Ab class II major histocompatibility complex glycoprotein and for normal (+/+) controls. The generation of CD8+ CTLp was not diminished in the -/- mice, though they failed to make virus-specific immunoglobulin G class antibodies. While the cellularity of the regional lymph nodes was decreased, the inflammatory process assayed by bronchoalveolar lavage (BAL) of the pneumonic lung was not modified, and potent CTL effectors were present in BAL populations recovered from both groups at day 10 after infection. There was little effect on virus clearance. Production of interleukin-2 by both freshly isolated BAL inflammatory cells and cultured lymph node cells wa...
This paper presents a dynamic region following formation control method for a swarm of robots. In this control strategy, a swarm of robots shall move together as a group inside a dynamic region that can rotate or scale to enable the robots to adjust the formation. Various desired shapes can be formed by choosing appropriate functions. Unlike existing formation control methods, the proposed method do not need to have specific identities or orders in the group but yet dynamic formation can be formed for a large group of robots. This enables a swarm of robots to adjust the formation during the course of maneuver. The system is also scalable in the sense that any robot can move into the formation or leave the formation without affecting the other robots. Lyapunov-like function is presented for convergence analysis of the multi-robot system...
Pulsed terahertz spectroscopy is used to determine the superfluid response of a YBa2Cu3O7−δ film under both thermal and optical stimulation. The coherent, time‐domain technique is used in a novel configuration to directly measure the complex conductivity of the film versus temperature and continuous‐wave laser illumination. At 0.6 Tc, the superfluid shows an identical response regardless of whether the stimulus is thermal or optical. This contrasts with the behavior of the superfluid at 0.26 Tc, where dramatic differences are observed depending on whether the sample is heated or subjected to optical illumination. It is suggested that these differences arise from an enhanced contribution due to quantum effects, and thus also from a strong temperature dependence of the quasiparticle recombination time at low temperatures. © 1995 American...
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