Lag of Low-Energy Photons in an X-ray Burst Oscillation: Doppler Delays

Numerous X-ray bursts show strong oscillations in their flux at several hundred Hz as revealed by RXTE. Analyzing one such oscillation from the X-ray binary Aql X-1, I find that low energy photons (3.5-5.7 keV) lag high energy photons (>5.7 keV) by approximately 1 radian. The oscillations are thought to be produced by hot spots on the spinning neutron star. The lags can then be explained by a Doppler shifting of emission from the hot spots; higher energy photons being emitted earlier in the spin phase as the spot approaches the observer. A quantitative test of this simple model shows a remarkable agreement with the data. Similar low energy lags have been measured in kilohertz quasi-periodic oscillations and in the accreting millisecond pulsar SAX J1808.4-3658. A Doppler delay mechanism may be at work there as well.Comment: accepted ApJ Letter

Photochemical delivery of nitric oxide.

There remains considerable interest in developing methods for the targeted delivery of nitric oxide and other small molecule bioregulators such as carbon monoxide to physiological targets. One such strategy is to use a "caged" NO that is "uncaged" by excitation with light. Such photochemical methods convey certain key advantages such as the ability to control the timing, location and dosage of delivery, but also have some important disadvantages, such as the relatively poor penetration of the ultraviolet and visible wavelengths often necessary for the uncaging process. Presented here is an overview of ongoing studies in the author's laboratory exploring new photochemical NO precursors including those with nanomaterial antennas designed to enhance the effectiveness of these precursors with longer excitation wavelengths

On the Canonical Equivalence of Liouville and Free Fields

We obtain the parity invariant generating functional for the canonical transformation mapping the Liouville theory into a free scalar field and explain how it is related to the pseudoscalar transformationComment: 8 pages, Latex, Important earlier work by G.P. Jordadze acknowledge

Detection of negative energy: 4-dimensional examples

We study the response of switched particle detectors to static negative energy densities and negative energy fluxes. It is demonstrated how the switching leads to excitation even in the vacuum and how negative energy can lead to a suppression of this excitation. We obtain quantum inequalities on the detection similar to those obtained for the energy density by Ford and co-workers and in an `operational' context by Helfer. We revisit the question `Is there a quantum equivalence principle?' in terms of our model. Finally, we briefly address the issue of negative energy and the second law of thermodynamics.Comment: 10 pages, 7 figure