Marine Cloud Brightening (MCB), should it ever need to be deployed, envisions the formation of 10 17 salt Cloud Condensation Nuclei (CCN) per second coming from each of several thousand vessels deployed worldwide. The creation of this many nuclei on such a vast scale, from micron-or submicron-sized seawater droplets, preferably mono-disperse, poses a considerable engineering challenge. Various existing or experimental spray methods were investigated for feasibility, resulting in the identification of a few with promising results. Electro-spraying from Taylor cone-jets, using either silicon micromachined long capillaries or short capillary polymer substrates attached to a porous substrate, appears to have the best potential for implementation of all the methods that have been investigated so far.

Portable pop-up spectroscope Phys. Teach. 50, 443 (2012) Video-based spatial portraits of a nonlinear vibrating string Am. J. Phys. 80, 862 (2012) Analyzing simple pendulum phenomena with a smartphone acceleration sensorWe describe an experimental implementation of the Malkus-Lorenz water wheel. We demonstrate that both chaotic and periodic behavior is observed as wheel parameters are changed in agreement with predictions from the Lorenz model. We further show that when the measured angular velocity of the water wheel is used as an input signal to a computer model implementing the Lorenz equations, high-quality synchronization of the model and the water wheel is achieved in the chaotic regime. This indicates that the Lorenz equations provide a good description of the water wheel dynamics.

A polycrystalline silicon film 0.55 μm thick was deposited in a low-pressure CVD reactor on a Si3N4 substrate. Islands of various sizes (2×20 μm up to 20×160 μm) were prepared by standard photolithographic techniques. Laser annealing was then performed under conditions which are known to cause an increase in grain size from ∼500 Å to long narrow crystals of 2×25 μm in a continuous polysilicon film. These same conditions were found to produce single-crystal 〈100〉 material in the (2×20 μm) islands. However, 25×25-μm and 20×160-μm islands remain polycrystalline after the laser scan.

In a closely correlated study, we have investigated phase transformations and grain growth phenomena together with measurements of electrical resistivity in the silicides of tungsten, molybdenum, and tantalum. In the case of WSi2, we find the tetragonal structure at all temperatures of anneal between 700 and 1100 °C. Furthermore, the activation energy, 0.65 eV, derived from grain growth measurements is close to the value, 0.66 eV, derived from the increase in electrical conductivity. In the case of MoSi2, we find a mixture of hexagonal and tetragonal phases after annealing at 700 °C and pure tetragonal phase at 800 °C and above. Once again the activation energies derived from grain growth and electrical conductivity measurements are very similar. TaSi2 gives anomalous results compared with the other two silicides. Electrical conductivity shows an asymptotic behavior with increasing anneal temperature. This is probably related to the fact that tetragonal TaO2 was found in the films.

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