Tukey methods [G. M. Jenkins and D. G. Watts, Spectral Analysis and its Applications (Holden-Day, Oakland, CA, 1968)] to the ␦ 18 O anomalies resolves statistically significant (minimum of 80% level) spectral peaks at 12.2-, 8.3-, 5.5-, 3.78-, 2.3-, and 1.7-year periods. The maximum entropy method places these peaks at 11.4, 7.8, 5.5, and 3.5, 2.3, and 1.7 years. 13. We used singular spectrum analysis (SSA) [R. Vautard and M. Ghil, Physica D 35, 395 (1989)] to reconstruct the most energetic modes in the coral record. After the removal of the seasonal cycle and the longterm trend, with a window length of M ϭ 39 years, SSA produces two modes in clean quadrature: modes 1 and 2, with a period of 11.8 years, and modes 3 and 4, with a period of 5.3 years (modes with periods greater than 39 years are unresolved). After the further removal of the decadal and interdecadal modes and with a window length of M ϭ 25 years, two modes emerge in quadrature: modes 1 and 2, with a period of 5.3 years, and modes 3 and 4, with a period of 3.5 years. The quasi-biennial signal emerges in clean quadrature when a 10-year window length is used. Monte Carlo simulations suggest that all of these modes represent statistically significant (at the 95% confidence level) concentrations of variance. More conventional band-pass filtering yields nearly identical patterns.

A functioning logic gate based on quantum-dot cellular automata is presented, where digital data are encoded in the positions of only two electrons. The logic gate consists of a cell, composed of four dots connected in a ring by tunnel junctions, and two single-dot electrometers. The device is operated by applying inputs to the gates of the cell. The logic AND and OR operations are verified using the electrometer outputs. Theoretical simulations of the logic gate output characteristics are in excellent agreement with experiment.

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We present a hybrid assembly technique to facilitate the transport measurements of electronic molecules. The technique consists of forming a self-assembled monolayer of the investigated molecule on prepatterned electrodes and then bridging the electrodes with nanoparticles using an alternating electric field. This technique can potentially provide a quick and simple way to screen a large number of electronic molecules. As an example, we report preliminary transport measurements of 1-nitro-2,5-di(phenylethynyl-4*-thioacetyl)benzene as a test molecule. The data show qualitative agreement with previously published results for a similar molecule.