Physical Sciences and Mathematics Commons^™

"Hands-On" Epicycles And Retrograde Motion, Matthew J. Moelter, Bernard A. Bates

Physics

No abstract provided.

Hands-On Phasors And Multiple-Slit Interference, Rand S. Worland, Matthew J. Moelter

Physics

No abstract provided.

Reaction Of Dioxygen With A Cross-Conjugated Carbon-Carbon Double Bond In A Bis-Macrocycle Diiron Compound, D. Brent Macqueen, Christopher Lange, Melvin Calvin, John W. Otvos, Larry O. Spreer, Christian B. Allan, Anna Ganse, Richard B. Frankel

Physics

Dioxygen at atmospheric pressure attacks a cross-conjugated carbon-carbon double bond in a diiron complex to form two, like, keto macrocyclic iron(II) complexes. This reaction occurs with high yield in both solution and in the solid state. A dioxetane intermediate is, therefore, invoked. The rate of the reaction is very dependent on the nature of the axial ligands on the low-spin iron(II) ions in the bimetallic complex. The rate is at least a factor of 10⁴ faster with DMF ligands than with CH₃CN axial ligands. This rate dependence is explained by stabilization of a peroxo biradical transition state …

Determination Of The Preexponential Frequency Factor For Superparamagnetic Maghemite Particles In Magnetoferritin, Bruce M. Moskowitz, Richard B. Frankel, Sarah A. Walton, Dominic P. E. Dickson, K. K. W. Wong, T. Douglas, Stephen Mann

Physics

Magnetization and Mössbauer measurements on maghemite particles with an average particle diameter of 10 nm have been made in the temperature range from 5 K to 353 K spanning the superparamagnetic (SPM) and stable single domain (SD) regimes. The maghemite particles were produced within the iron-storage protein ferritin, resulting in a narrowly-sized, weakly interacting nanocomposite material called magnetoferritin. Experiments combining hysteresis measurements, low temperature remanence, and Mössbauer spectroscopy were used to characterize magnetoferritin and to provide experimental estimates of (1) the pre-exponential frequency factor ƒ₀ in the Néel-Arhennius relaxation equation; (2) the SPM threshold size at room temperature for …

Single-Shot Detection Of Wavepacket Evolution, M. B. Campbell, Thomas J. Bensky, Robert R. Jones

Physics

We have developed a new instrument for monitoring electronic wavepacket dynamics using a single electromagnetic pulse pair. The operation of the device is analogous to that of single-shot cross-correlators commonly used to monitor the temporal evolution of short laser pulses. We have used the instrument to probe wavepacket evolution over time scales ranging from 100 psec to less than 1 fsec. The device reduces the amount of time required to collect pump-probe time delay data by orders of magnitude, greatly reducing the deleterious effects of experimental drifts. In addition, the single-shot feature provides real-time feedback as to the affect of …

Ionization Of Na Rydberg Atoms By Subpicosecond Quarter-Cycle Circularly Polarized Pulses, Thomas J. Bensky, G. Haeffler, Robert R. Jones

Physics

We report the first observation of ionization of Rydberg atoms by subpicosecond, circularly polarized THz radiation. The field amplitude in these pulses is non-negligible for only one-quarter of an optical cycle. The experiment is performed in the short-pulse regime, where the duration of the ionizing pulse is shorter than the classical Kepler period of the Rydberg electron. We find that the ionization probability for these atoms is remarkably insensitive to the time-varying polarization of the THz field.

Magneto-Aerotaxis In Marine Coccoid Bacteria, Richard B. Frankel, Dennis A. Bazylinski, Mark S. Johnson, Barry L. Taylor

Physics

Magnetotactic cocci swim persistently along local magnetic field lines in a preferred direction that corresponds to downward migration along geomagnetic field lines. Recently, high cell concentrations of magnetotactic cocci have been found in the water columns of chemically stratified, marine and brackish habitats, and not always in the sediments, as would be expected for persistent, downward-migrating bacteria. Here we report that cells of a pure culture of a marine magnetotactic coccus, designated strain MC-1, formed microaerophilic bands in capillary tubes and used aerotaxis to migrate to a preferred oxygen concentration in an oxygen gradient. Cells were able to swim in …

Review Of Possible Health Effects Of Exposure To Residential Electric And Magnetic Fields, David W. Hafemeister

Physics

No abstract provided.

Sea Brightness Temperature And Effects Of Spray And Whitecaps, Richard P. Barber Jr., Jin Wu

Physics

Following the approach of Tang [1974], the microwave brightness of the sea surface is recalculated with recent parameterizations in terms of wind velocity for the slope distribution and whitecap coverage of the sea surface and the contribution of sea spray. The difference between this revised calculation with no free parameters and the earlier one becomes more significant as the wind velocity increases; it reaches 10 K or more at a wind velocity of 20 m s-1. Present predictions compare favorably with experimental results, suggesting that this model does include the essential physical mechanisms.

Review Of The Nuclear Black Market, Global Organized Crime Project, David W. Hafemeister

Physics

No abstract provided.

Summing Up: Questions And Answers On The Comprehensive Test Ban Treaty, David W. Hafemeister

Physics

My experiences with the ratification of the Strategic Arms Reduction Treaty, the Threshold Test Ban Treaty, and the Conventional Armed Forces in Europe Treaty have led me to conclude that presenting technical issues early in the process greatly reduces their politicization during the ratification end game. This chapter summarizes the important issues that will be raised during the debate on ratification of the Comprehensive Test Ban Treaty. It uses a compact question and answer format to cover the following topics: I. Nuclear Proliferation, II. Nuclear Arms Control, III. Warhead Reliability and Yield for National Security, IV. Warhead Safety, V. Verification, …

A Child's Flashlight And Rc Circuit Concepts, Matthew J. Moelter, Rand S. Worland

Physics

No abstract provided.

Reflections On The Gao Report On The Nuclear Triad, David W. Hafemeister

Physics

Senate Hearings on the GAO report on the nuclear triad and on the START treaty showed that vulnerabilities of the U.S. triad were vastly over‐stated, that the performance of new projected strategic systems was over‐estimated, and that the performance of existing U.S. strategic systems was under‐estimated. These exaggerations enhanced the psychological (Freud) aspects of the Cold War and compromised logic (Newton).

With the end of the Cold War it is imperative that we re‐examine the basic premises that guided the choices of the strategic nuclear systems. The initial bottom line is that these systems were successful in that they did …