7,245 research outputs found
Proceedings of a Workshop on Cosmogenic Nuclide Production Rates
Abstracts of reports from the proceedings are presented. The presentations were divided into discussion topics. The following general topic areas were used: (1) measured cosmogenic noble gas and radionuclide production rates in meteorite and planetary surface samples; (2) cross-section measurements and simulation experiments; and (3) interpretation of sample studies and simulation experiments
S-Adenosyl-L-homocysteine hydrolase from Dictyostelium discoideum is inactivated by cAMP and reactivated by NAD+
AbstractPurified S-adenosyl-L-homocysteine hydrolase from Dictyostelium discoideum is inactivated when incubated at 25°C with cAMP. Half maximal velocity of the inactivation process occurs at 10 μM cAMP. Catalytic activity is fully restored by further incubation with NAD+, but not with NADP+ or NADH. The enzyme must be preincubated with cAMP or NAD+ to induce inactivation or reactivation, respectively, since neither of these ligands has an effect on the active or inactive enzyme when added directly to the assay. These results suggest a role for cAMP and NAD+ in the regulation of cellular methylation reactions by altering the level of S-adenosyl-L-homocysteine via S-adenosyl-L-homocysteine hydrolase
Nonlinear structures and thermodynamic instabilities in a one-dimensional lattice system
The equilibrium states of the discrete Peyrard-Bishop Hamiltonian with one
end fixed are computed exactly from the two-dimensional nonlinear Morse map.
These exact nonlinear structures are interpreted as domain walls (DW),
interpolating between bound and unbound segments of the chain. The free energy
of the DWs is calculated to leading order beyond the Gaussian approximation.
Thermodynamic instabilities (e.g. DNA unzipping and/or thermal denaturation)
can be understood in terms of DW formation.Comment: 4 pages, 5 figures, to appear in Phys. Rev. Let
Investigation of Three Design Modifications of the NACA Injection Impeller in an R-3350 Engine
An investigation was conducted to determine the effects of three design modifications of the original NACA injection impeller on the performance of an R-3350 engine. Different methods of injecting the fuel into the impeller air stream were studied and evaluated from the individual cylinder fuel-air ratios and the resulting cylinder temperatures. Each impeller was tested for a range of engine powers normally used in flight operation. The relatively simple design of the original injection impeller produced approximately the same mixture- and temperature-distribution characteristics as the modified impellers of more complex design. None of the modifications appreciably affected the manifold pressure, the combustion-air flow, nor the throttle angle required to maintain a given engine power
Glycinergic Transmission: Physiological, Developmental and Pathological Implications
No abstract available
Deterministic protocol for mapping a qubit to coherent state superpositions in a cavity
We introduce a new gate that transfers an arbitrary state of a qubit into a
superposition of two quasi-orthogonal coherent states of a cavity mode, with
opposite phases. This qcMAP gate is based on conditional qubit and cavity
operations exploiting the energy level dispersive shifts, in the regime where
they are much stronger than the cavity and qubit linewidths. The generation of
multi-component superpositions of quasi-orthogonal coherent states, non-local
entangled states of two resonators and multi-qubit GHZ states can be
efficiently achieved by this gate
Hardware-efficient autonomous quantum error correction
We propose a new method to autonomously correct for errors of a logical qubit
induced by energy relaxation. This scheme encodes the logical qubit as a
multi-component superposition of coherent states in a harmonic oscillator, more
specifically a cavity mode. The sequences of encoding, decoding and correction
operations employ the non-linearity provided by a single physical qubit coupled
to the cavity. We layout in detail how to implement these operations in a
practical system. This proposal directly addresses the task of building a
hardware-efficient and technically realizable quantum memory.Comment: 12 pages,6 figure
Dynamically protected cat-qubits: a new paradigm for universal quantum computation
We present a new hardware-efficient paradigm for universal quantum
computation which is based on encoding, protecting and manipulating quantum
information in a quantum harmonic oscillator. This proposal exploits
multi-photon driven dissipative processes to encode quantum information in
logical bases composed of Schr\"odinger cat states. More precisely, we consider
two schemes. In a first scheme, a two-photon driven dissipative process is used
to stabilize a logical qubit basis of two-component Schr\"odinger cat states.
While such a scheme ensures a protection of the logical qubit against the
photon dephasing errors, the prominent error channel of single-photon loss
induces bit-flip type errors that cannot be corrected. Therefore, we consider a
second scheme based on a four-photon driven dissipative process which leads to
the choice of four-component Schr\"odinger cat states as the logical qubit.
Such a logical qubit can be protected against single-photon loss by continuous
photon number parity measurements. Next, applying some specific Hamiltonians,
we provide a set of universal quantum gates on the encoded qubits of each of
the two schemes. In particular, we illustrate how these operations can be
rendered fault-tolerant with respect to various decoherence channels of
participating quantum systems. Finally, we also propose experimental schemes
based on quantum superconducting circuits and inspired by methods used in
Josephson parametric amplification, which should allow to achieve these driven
dissipative processes along with the Hamiltonians ensuring the universal
operations in an efficient manner.Comment: 28 pages, 11 figure
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