Long-period waves over California\u27s continental borderland Part II. Tsunamis

During the Chilean tsunami of 22 May 1960, precise readings of sea level were digitally recorded every 15 seconds by the La Jolla low-frequency wave instrument. The tsunami remained above background for a week. The record gave a good opportunity to measure the decay of tsunami energy as a function of frequency. Energy is reduced by 1/e about once each half day. The decay is somewhat more rapid at high frequen cies and at high energy densities. The total energy of the tsunami is estimated to be of the order of 3 x 1023 ergs

Long-period waves over California\u27s continental borderland. Part III The decay of tsunamis and the dissipation of tidal energy

The characteristic damping (energy e-folding) time derived from the decay of the tsunami pulse can be compared to the dissipation time of the lunar semidiurnal tides as inferred from the discrepancies in the orbital motions of the Moon, Sun, and Mercury. The times are comparable, of the order of ½ day, and this suggests that the same processes are responsible for the dissipation of the tide waves and tidal waves

Long-period waves over California\u27s continental borderland Part I. Background spectra

Long ocean waves, with frequencies between 0.2 and xo cycles per hour (cph), have been recorded simultaneously at La Jolla on the California coast and at San Clemente Island, about rno km seaward. The spectral power is greatest at the lowest frequencies but remains fairly uniform (about 5 x 10-2 cm2/cph) between 0.7 and 10 cph. Comparison of the Island and shore records shows that at the lowest frequencies (below 0.7 cph) the two records are consistently in phase and are highly coherent, as might be expected; above 0.7 cph they are out of phase, and the coherence is low...

Analysis of Small Water Management Structures in Irrigation Distribution Systems

The Irrigation and Drainage Research Conference conducted at Utah State University (ASCE, 1964) delineated many of the research needs regarding “Small Low- Cost Hydraulic Structures for Conveyance and Distribution Systems,” which was one of the six topics considered at the conference. In discussing possibilities for accomplishing the recommended research, it was suggested by some panel members that a considerable portion of the work could be undertaken by graduate students, particularly at the Master of Science level. The intent of this report has been to sort through the large volume of literature in an attempt to define the specific research needs regarding small water management structure used in irrigation distribution systems. In particular, the emphasis has been to develop specific research topics which could be accomplished as a thesis by a graduate student at the Master of Science level

Quantifying bamboo coral growth rate nonlinearity with the radiocarbon bomb spike : a new model for paleoceanographic chronology development

© The Author(s), 2017. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 125 (2017): 26-39, doi:10.1016/j.dsr.2017.04.006.Bamboo corals, long-lived cold water gorgonin octocorals, offer unique paleoceanographic archives of the intermediate ocean. These Isididae corals are characterized by alternating gorgonin nodes and high Mg-calcite internodes, which synchronously extend radially. Bamboo coral calcite internodes have been utilized to obtain geochemical proxy data, however, growth rate uncertainty has made it difficult to construct precise chronologies for these corals. Previous studies have relied upon a tie point from records of the anthropogenic Δ14C bomb spike preserved in the gorgonin nodes of live-collected corals to calculate a mean radial extension rate for the outer ~50 years of skeletal growth. Bamboo coral chronologies are typically constructed by applying this mean extension rate to the entire coral record, assuming constant radial extension with coral age. In this study, we aim to test this underlying assumption by analyzing the organic nodes of six California margin bamboo corals at high enough resolution (<0.5 mm) to identify the Δ14C bomb spike, including two tie points at 1957 and 1970, plus coral collection date (2007.5) for four samples. Radial extension rates between tie points ranged from 10 to 204 μm/year, with a decrease in growth rate evident between the 1957-1970 and 1970- 2007.5 periods for all four corals. A negative correlation between growth rate and coral radius (r = -0.7; p = 0.03) was determined for multiple bamboo coral taxa and individuals from the California margin, demonstrating a decline in radial extension rate with specimen age and size. To provide a mechanistic basis for these observations, a simple mathematical model was developed based on the assumption of a constant increase in circular cross sectional area with time to quantify this decline in radial extension rate with coral size between chronological tie points. Applying the area-based model to our Δ14C bomb spike time series from individual corals improves chronology accuracy for all live-collected corals with complete Δ14C bomb spikes. Hence, this study provides paleoceanographers utilizing bamboo corals with a method for reducing age model uncertainty within the anthropogenic bomb spike era (~1957-present). Chronological uncertainty is larger for the earliest portion of coral growth, particularly for skeleton precipitated prior to bomb spike tie points, meaning age estimations for samples living before 1957 remain uncertain. Combining this technique with additional chronological markers could improve age models for an entire bamboo coral. Finally, the relative consistency in growth rate in similarly-aged corals of the same depth and location supports the hypothesis that skeletal growth may be limited by local environmental conditions.This research was made possible by National Science Foundation Award #1420984 to M. LaVigne and a Clare Boothe Luce Fellowship to M. Frenkel

Frustrated H-Induced Instability of Mo(110)

Using helium atom scattering Hulpke and L"udecke recently observed a giant phonon anomaly for the hydrogen covered W(110) and Mo(110) surfaces. An explanation which is able to account for this and other experiments is still lacking. Below we present density-functional theory calculations of the atomic and electronic structure of the clean and hydrogen-covered Mo(110) surfaces. For the full adsorbate monolayer the calculations provide evidence for a strong Fermi surface nesting instability. This explains the observed anomalies and resolves the apparent inconsistencies of different experiments.Comment: 4 pages, 2 figures, submitted to PR

Antireflection coatings from analogy between electron scattering and spin precession

We use the analogy between scattering of a wave from a potential, and the precession of a spin-half particle in a magnetic field, to gain insight into the design of an antireflection coating for electrons in a semiconductor superlattice. It is shown that the classic recipes derived for optics are generally not applicable due to the different dispersion law for electrons. Using the stability conditions we show that a Poisson distribution of impedance steps is a better approximation than is a Gaussian distribution. Examples are given of filters with average transmissivity exceeding 95% over an allowed band

Massively parallel computing on an organic molecular layer

Current computers operate at enormous speeds of ~10^13 bits/s, but their principle of sequential logic operation has remained unchanged since the 1950s. Though our brain is much slower on a per-neuron base (~10^3 firings/s), it is capable of remarkable decision-making based on the collective operations of millions of neurons at a time in ever-evolving neural circuitry. Here we use molecular switches to build an assembly where each molecule communicates-like neurons-with many neighbors simultaneously. The assembly's ability to reconfigure itself spontaneously for a new problem allows us to realize conventional computing constructs like logic gates and Voronoi decompositions, as well as to reproduce two natural phenomena: heat diffusion and the mutation of normal cells to cancer cells. This is a shift from the current static computing paradigm of serial bit-processing to a regime in which a large number of bits are processed in parallel in dynamically changing hardware.Comment: 25 pages, 6 figure

Tube Models for Rubber-Elastic Systems

In the first part of the paper we show that the constraining potentials introduced to mimic entanglement effects in Edwards' tube model and Flory's constrained junction model are diagonal in the generalized Rouse modes of the corresponding phantom network. As a consequence, both models can formally be solved exactly for arbitrary connectivity using the recently introduced constrained mode model. In the second part, we solve a double tube model for the confinement of long paths in polymer networks which is partially due to crosslinking and partially due to entanglements. Our model describes a non-trivial crossover between the Warner-Edwards and the Heinrich-Straube tube models. We present results for the macroscopic elastic properties as well as for the microscopic deformations including structure factors.Comment: 15 pages, 8 figures, Macromolecules in pres