Ultraviolet and thermally stable polymer compositions

A class of polymers is provided, namely, poly(diarylsiloxy) arylazines. These polymers have a basic chemical composition which has the property of stabilizing the optical and physical properties of the polymer against the degradative effect of ultraviolet light and high temperatures. This stabilization occurs at wavelengths including those shorter than found on the surface of the earth and in the absence or presence of oxygen, making the polymers of the present invention useful for high performance coating applications in extraterrestrial space as well as similar applications in terrestrial service. The invention also provides aromatic azines which are useful in the preparation of polymers such as those of the present invention

Ultraviolet and thermally stable polymer compositions

A new class of polymers is provided, namely, poly (diarylsiloxy) arylazines. These novel polymers have a basic chemical composition which has the property of stabilizing the optical and physical properties of the polymer against the degradative effect of ultraviolet light and high temperatures. This stabilization occurs at wavelengths including those shorter than found on the surface of the earth and in the absence or presence of oxygen, making the polymers useful for high performance coating applications in extraterrestrial space as well as similar applications in terrestrial service. The invention also provides novel aromatic azines which are useful in the preparation of polymers such as those described

Ultraviolet and thermally stable polymer compositions

Copolymers, produced from aromatic substituted aromatic azine-siloxane compositions, are thermally stable, solar ultraviolet light non-degradable by wavelengths shorter than those reaching earth surface

Using scale heights derived from bottomside ionograms for modelling the IRI topside profile

Groundbased ionograms measure the Chapman scale height <i>H_T</i> at the F2-layer peak that is used to construct the topside profile. After a brief review of the topside model extrapolation technique, comparisons are presented between the modeled profiles with incoherent scatter radar and satellite measurements for the mid latitude and equatorial ionosphere. The total electron content TEC, derived from measurements on satellite beacon signals, is compared with the height-integrated profiles ITEC from the ionograms. Good agreement is found with the ISR profiles and with results using the low altitude TOPEX satellite. The TEC values derived from GPS signal analysis are systematically larger than ITEC. It is suggested to use <i>H_T</i> , routinely measured by a large number of Digisondes around the globe, for the construction of the IRI topside electron density profile

Short-term relationship of total electron content with geomagnetic activity in equatorial regions

The short-term relationship between equatorial ionosphere and geomagnetic activity is examined. Hourly averages of the total electron content (TEC) and critical frequency of the F(2) layer (f(o)F(2)) are compared with the Dst index, a proxy for equatorial geomagnetic activity, at three local times (0700-0800, 1200-1300, and 1600-1700 LT) from March 1998 to August 1999. Owing to the geomagnetic latitude and local times used, positive storms, almost exclusively, are observed (cf. Prolss, 1995). While f(o)F(2) measurements over an extended period (similar to 10 years) have been studied (Matsushita, 1959) and TEC and f(o)F(2) are coupled, TEC measurements can provide a significantly better signal-to-noise ratio. At timescales of 2-3, 3-5, 5-9, and 9-11 days, there are significant correlations (similar to 0.4 at local noon, when all the data are included) between TEC and Dst. These correlations increase from morning to afternoon. By comparison, correlations between f(o)F(2) and Dst are significantly smaller, similar to 0.2 ( near the noise level) at local noon. Even during geomagnetically quiet times (Dst \u3e -20), a clear correlation (0.21, which exceeds the 95% confidence level by 0.05) is seen between TEC and Dst at the shortest timescale examined. As geomagnetic activity increases, the correlations increase rapidly. For example, when moderate levels of geomagnetic activity (Dst \u3e -50) are included for observations at local noon, distinct correlations (similar to 0.3) are seen and persist for all but the longest timescale; with higher levels of geomagnetic activity included, there are distinct correlations at all the timescales examined. The presence of a significant correlation at quiet conditions and persistence of the correlation at moderate levels of activity are both unexpected

Electon density profiles of the topside ionosphere

The existing uncertainties about the electron density profiles in the topside ionosphere, i.e., in the height region from h m F 2 to ~ 2000 km, require the search for new data sources. The ISIS and Alouette topside sounder satellites from the sixties to the eighties recorded millions of ionograms but most were not analyzed in terms of electron density profiles. In recent years an effort started to digitize the analog recordings to prepare the ionograms for computerized analysis. As of November 2001 about 350 000 ionograms have been digitized from the original 7-track analog tapes. These data are available in binary and CDF format from the anonymous ftp site of the National Space Science Data Center. A search site and browse capabilities on CDAWeb assist the scientific usage of these data. All information and access links can be found at http://nssdc.gsfc.nasa.gov/space/isis/isis-status. html. This paper describes the ISIS data restoration effort and shows how the digital ionograms are automatically processed into electron density profiles from satellite orbit altitude (1400 km for ISIS-2) down to the F peak. Because of the large volume of data an automated processing algorithm is imperative. The TOPside Ionogram Scaler with True height algorithm TOPIST software developed for this task is successfully scaling ~ 70% of the ionograms. An «editing process» is available to manually scale the more difficult ionograms. The automated processing of the digitized ISIS ionograms is now underway, producing a much-needed database of topside electron density profiles for ionospheric modeling covering more than one solar cycle

Local Properties of the Potential Energy Landscape of a Model Glass: Understanding the Low Temperature Anomalies

Though the existence of two-level systems (TLS) is widely accepted to explain low temperature anomalies in the sound absorption, heat capacity, thermal conductivity and other quantities, an exact description of their microscopic nature is still lacking. We performed computer simulations for a binary Lennard-Jones system, using a newly developed algorithm to locate double-well potentials (DWP) and thus two-level systems on a systematic basis. We show that the intrinsic limitations of computer simulations like finite time and finite size problems do not hamper this analysis. We discuss how the DWP are embedded in the total potential energy landscape. It turns out that most DWP are connected to the dynamics of the smaller particles and that these DWP are rather localized. However, DWP related to the larger particles are more collective

Critical currents in Josephson junctions with macroscopic defects

The critical currents in Josephson junctions of conventional superconductors with macroscopic defects are calculated for different defect critical current densities as a function of the magnetic field. We also study the evolution of the different modes with the defect position, at zero external field. We study the stability of the solutions and derive simple arguments, that could help the defect characterization. In most cases a reentrant behavior is seen, where both a maximum and a minimum current exist.Comment: 17 pages with 16 figures, submitted to Supercond. Sci. Techno

Short-term relationship between solar irradiances and equatorial peak electron densities

[1] The short-term relationship of the equatorial peak electron density and the solar short-wavelength irradiance is examined using foF2 observations from Jicamarca, Peru and recent solar irradiance measurements from satellites. Solar soft X-ray measurements from both the Student Nitric Oxide Explorer (SNOE) ( 1998 - 2000) and Thermosphere Ionosphere Mesosphere Energetics Dynamics ( TIMED) ( 2002 - 2004) satellites as well as extreme ultraviolet (EUV) measurements from the TIMED satellite are used. Soft X-rays show similar or higher correlation with foF2 at short timescales ( 27 days or less) than EUV does, although the EUV correlation is higher for longer periods. For the short-term variations, both SNOE and TIMED observations have a higher correlation in the morning ( similar to 0.46) than in the afternoon ( similar to 0.1). In the afternoon, SNOE observations have a higher correlation ( similar to 0.2) with foF2 than the TIMED observations ( similar to 0.1 correlation), which may be due to differences in the solar cycle. At morning times, foF2 has a similar to 27-day variation, consistent with the solar rotation rate. After noon, but not in the morning, a similar to 13.5-day variation consistently appears in foF2. This similar to 13.5-day variation is attributed to geomagnetic influences

Interference, reduced action, and trajectories

Instead of investigating the interference between two stationary, rectilinear wave functions in a trajectory representation by examining the two rectilinear wave functions individually, we examine a dichromatic wave function that is synthesized from the two interfering wave functions. The physics of interference is contained in the reduced action for the dichromatic wave function. As this reduced action is a generator of the motion for the dichromatic wave function, it determines the dichromatic wave function's trajectory. The quantum effective mass renders insight into the behavior of the trajectory. The trajectory in turn renders insight into quantum nonlocality.Comment: 12 pages text, 5 figures. Typos corrected. Author's final submission. A companion paper to "Welcher Weg? A trajectory representation of a quantum Young's diffraction experiment", quant-ph/0605121. Keywords: interference, nonlocality, trajectory representation, entanglement, dwell time, determinis