Magnetospheric eclipses in the double pulsar system J0737-3039

We argue that eclipses of radio emission from the millisecond pulsar A in the double pulsar system J0737-3039 are due to synchrotron absorption by plasma in the closed field line region of the magnetosphere of its normal pulsar companion B. A's radio beam only illuminates B's magnetosphere for about 10 minutes surrounding the time of eclipse. During this time it heats particles at r\gtrsim 10^9 cm to relativistic energies and enables extra plasma to be trapped by magnetic mirroring. An enhancement of the plasma density by a factor \sim 10^2 is required to match the duration and optical depth of the observed eclipses. The extra plasma might be supplied by a source near B through B\gamma pair creation by energetic photons produced in B's outer gap. Excitation of pairs' gyrational motions by cyclotron absorption of A's radio beam can result in their becoming trapped between conjugate mirror points in B's magnetosphere. Because the trapping efficiency decreases with increasing optical depth, the plasma density enhancement saturates even under steady state illumination. The result is an eclipse with finite, frequency dependent, optical depth. After illumination by A's radio beam ceases, the trapped particles cool and are lost. The entire cycle repeats every orbital period. We speculate that the asymmetries between eclipse ingress and egress result in part from the magnetosphere's evolution toward a steady state when illuminated by A's radio beam. We predict that A's linear polarization will vary with both eclipse phase and B's rotational phase.Comment: 8 pages, 1 figure, submitted to ApJ, references corrected, detectability of reprocessed emission revised, major conclusions unchange

Voting, the Symmetric Group, and Representation Theory

We show how voting may be viewed naturally from an algebraic perspective by viewing voting profiles as elements of certain well-studied QSn-modules. By using only a handful of simple combinatorial objects (e.g., tabloids) and some basic ideas from representation theory (e.g., Schur\u27s Lemma), this allows us to recast and extend some well-known results in the field of voting theory

AGING BEHAVIOR OF VITON O-RING SEALS IN THE 9975 SHIPPING PACKAGE

The Savannah River Site (SRS) is storing plutonium (Pu) materials in the K-Area Materials Storage (KAMS) facility. The Pu materials were packaged according to the DOE-STD-3013 standard and shipped to the SRS in Type B 9975 packages. The robust 9975 shipping package was not designed for long-term product storage, but it is a specified part of the storage configuration and the KAMS facility safety basis credits the 9975 design with containment. Within the 9975 package, nested stainless steel containment vessels are closed with dual O-ring seals based on Viton{reg_sign} GLT or GLT-S fluoroelastomer. The aging behavior of the O-ring compounds is being studied to provide the facility with advanced notice of nonconformance and to develop life prediction models. A combination of field surveillance, leak testing of surrogate fixtures aged at bounding service temperatures, and accelerated-aging methodologies based on compression stress-relaxation and oxygen consumption analysis is being used to evaluate seal performance. A summary of the surveillance program relative to seal aging behavior is presented

9975 SHIPPING PACKAGE LIFE EXTENSION SURVEILLANCE PROGRAM RESULTS SUMMARY

Results from the 9975 shipping package Storage and Surveillance Program at the Savannah River Site (SRS) are summarized for justification to extend the life of the 9975 packages currently stored in the K-Area Complex (KAC). This justification is established with the stipulation that surveillance activities will continue throughout the extended time to ensure the continued integrity of the 9975 materials of construction and to further understand the currently identified degradation mechanisms. The 10 year storage life justification was developed prior to storage. A subsequent report was later used to validate the qualification of the 9975 shipping packages for 10 years in storage. However the qualification for the storage period was provided by the monitoring requirements of the 9975 Storage and Surveillance Program. This report summarizes efforts to determine a new safe storage limit for the 9975 shipping package based on the surveillance data collected since 2005 when the 9975 Storage and Surveillance Program began. The Program has demonstrated that the 9975 package has a robust design that can perform under a variety of conditions. The primary emphasis of the on-going 9975 Storage and Surveillance Program is an aging study of the 9975 Viton{reg_sign} containment vessel O-rings and the Celotex{reg_sign} fiberboard thermal insulation at bounding conditions of radiation, elevated temperatures and/or elevated humidity

AGING PERFORMANCE OF MODEL 9975 PACKAGE FLUOROELASTOMER O-RINGS

The influence of temperature and radiation on Viton{reg_sign} GLT and GLT-S fluoroelastomer O-rings is an ongoing research focus at the Savannah River National Laboratory. The O-rings are credited for leaktight containment in the Model 9975 shipping package used for transportation of plutonium-bearing materials. At the Savannah River Site, the Model 9975 packages are being used for interim storage. Primary research efforts have focused on surveillance of O-rings from actual packages, leak testing of seals at bounding aging conditions and the effect of aging temperature on compression stress relaxation behavior, with the goal of service life prediction for long-term storage conditions. Recently, an additional effort to evaluate the effect of aging temperature on the oxidation of the materials has begun. Degradation in the mechanical properties of elastomers is directly related to the oxidation of the polymer. Sensitive measurements of the oxidation rate can be performed in a more timely manner than waiting for a measurable change in mechanical properties, especially at service temperatures. Measuring the oxidation rate therefore provides a means to validate the assumption that the degradation mechanisms(s) do not change from the elevated temperatures used for accelerated aging and the lower service temperatures. Monitoring the amount of oxygen uptake by the material over time at various temperatures can provide increased confidence in lifetime predictions. Preliminary oxygen consumption analysis of a Viton GLT-based fluoroelastomer compound (Parker V0835-75) using an Oxzilla II differential oxygen analyzer in the temperature range of 40-120 C was performed. Early data suggests oxygen consumption rates may level off within the first 100,000 hours (10-12 years) at 40 C and that sharp changes in the degradation mechanism (stress-relaxation) are not expected over the temperature range examined. This is consistent with the known long-term heat aging resistance of fluoroelastomers relative to hydrocarbon-based elastomers, and in absence of antioxidants that may be consumed over time. Additional experimental effort will be undertaken in the short term range within the first 100 hours of thermal aging to capture further details of the oxygen consumption rate

TATA-Binding Protein Recognition and Bending of a Consensus Promoter Are Protein Species Dependent

The structure and behavior of full-length human TBP binding the adenovirus major late promoter (AdMLP) have been characterized using biophysical methods. The human protein induces a 97° bend in DNAAdMLP. The high-resolution functional data provide a quantitative energetic and kinetic description of the partial reaction sequence as native human TBP binds rapidly to a consensus promoter with high affinity. The reaction proceeds with successive formation of three bound species, all having strongly bent DNA, with the concurrence of binding and bending demonstrated by both fluorescence and anisotropy stopped flow. These results establish the protein species dependence of the TBP−DNAAdMLP structure and recognition mechanism. Additionally, the strong correlation between the DNA bend angle and transcription efficiency demonstrated previously for yeast TBP is shown to extend to human TBP. The heterologous NH2-terminal domains are the apparent source of the species-specific differences. Together with previous studies the present work establishes that TBPwt−DNATATA function and structure depend both on the TATA box sequence and on the TBP species

TATA-Binding Protein Recognition and Bending of a Consensus Promoter Are Protein Species Dependent

The structure and behavior of full-length human TBP binding the adenovirus major late promoter (AdMLP) have been characterized using biophysical methods. The human protein induces a 97° bend in DNAAdMLP. The high-resolution functional data provide a quantitative energetic and kinetic description of the partial reaction sequence as native human TBP binds rapidly to a consensus promoter with high affinity. The reaction proceeds with successive formation of three bound species, all having strongly bent DNA, with the concurrence of binding and bending demonstrated by both fluorescence and anisotropy stopped flow. These results establish the protein species dependence of the TBP−DNAAdMLP structure and recognition mechanism. Additionally, the strong correlation between the DNA bend angle and transcription efficiency demonstrated previously for yeast TBP is shown to extend to human TBP. The heterologous NH2-terminal domains are the apparent source of the species-specific differences. Together with previous studies the present work establishes that TBPwt−DNATATA function and structure depend both on the TATA box sequence and on the TBP species

Resonant Cyclotron Radiation Transfer Model Fits to Spectra from Gamma-Ray Burst GRB870303

We demonstrate that models of resonant cyclotron radiation transfer in a strong field (i.e. cyclotron scattering) can account for spectral lines seen at two epochs, denoted S1 and S2, in the Ginga data for GRB870303. Using a generalized version of the Monte Carlo code of Wang et al. (1988,1989b), we model line formation by injecting continuum photons into a static plane-parallel slab of electrons threaded by a strong neutron star magnetic field (~ 10^12 G) which may be oriented at an arbitrary angle relative to the slab normal. We examine two source geometries, which we denote "1-0" and "1-1," with the numbers representing the relative electron column densities above and below the continuum photon source plane. We compare azimuthally symmetric models, i.e. models in which the magnetic field is parallel to the slab normal, with models having more general magnetic field orientations. If the bursting source has a simple dipole field, these two model classes represent line formation at the magnetic pole, or elsewhere on the stellar surface. We find that the data of S1 and S2, considered individually, are consistent with both geometries, and with all magnetic field orientations, with the exception that the S1 data clearly favor line formation away from a polar cap in the 1-1 geometry, with the best-fit model placing the line-forming region at the magnetic equator. Within both geometries, fits to the combined (S1+S2) data marginally favor models which feature equatorial line formation, and in which the observer's orientation with respect to the slab changes between the two epochs. We interpret this change as being due to neutron star rotation, and we place limits on the rotation period.Comment: LaTeX2e (aastex.cls included); 45 pages text, 17 figures (on 21 pages); accepted by ApJ (to be published 1 Nov 1999, v. 525

Very-high-energy gamma radiation associated with the unshocked wind of the Crab pulsar

We show that the relativistic wind in the Crab pulsar, which is commonly thought to be invisible in the region upstream of the termination shock at R < 0.1 pc, in fact could be directly observed through its inverse Compton gamm-ray emission. The search for such specific component of radiation in the gamma-ray spectrum of the Crab can provide unique information about the unshocked pulsar wind that is not accessible at other wavelengths.Comment: 11 pages, 11 figures, to appear in one of the April issues of MNRA

Electron-Positron Jets from a Critically Magnetized Black Hole

The curved spacetime surrounding a rotating black hole dramatically alters the structure of nearby electromagnetic fields. The Wald field which is an asymptotically uniform magnetic field aligned with the angular momentum of the hole provides a convenient starting point to analyze the effects of radiative corrections on electrodynamics in curved spacetime. Since the curvature of the spacetime is small on the scale of the electron's Compton wavelength, the tools of quantum field theory in flat spacetime are reliable and show that a rotating black hole immersed in a magnetic field approaching the quantum critical value of $B_k=m^2 c^3/(e\hbar) \approx 4.4 \times 10^{13}$~G $\approx 1.3\times10^{-11}$ cm$^{-1}$ is unstable. Specifically, a maximally rotating three-solar-mass black hole immersed in a magnetic field of $2.3 \times 10^{12}$~G would be a copious producer of electron-positron pairs with a luminosity of $3 \times 10^{52}$ erg s$^{-1}$.Comment: 10 pages, 6 figures, submitted to Phys. Rev.