Review of Spectroscopic Data for Measurements of Stratospheric Species

Results and recommendations from a two day workshop are discussed. A review of the current status of experimental and theoretical spectroscopic data on molecules of stratospheric interest is given along with recommendations for additional research. Methods for disseminating new and existing data are also discussed

Atmospheric solar absorption measurements in the 9 to 11 mu m region using a diode laser heterodyne spectrometer

A tunable diode laser heterodyne radiometer was developed for ground-based measurements of atmospheric solar absorption spectra in the 8 to 12 microns spectral range. The performance and operating characteristics of this Tunable Infrared Heterodyne Radiometer (TIHR) are discussed along with atmospheric solar absorption spectra of HNO3, O3, CO2, and H2O in the 9 to 11 microns spectral region

Atmospheric solar absorption measurements in the 9-11 micron region using a diode laser heterodyne spectrometer

A tunable diode laser heterodyne radiometer was developed for ground based measurements of atmospheric solar absorption spectra in the 9 to 12 micron spectral range. The performance and operating characteristics of this tunable infrared heterodyne radiometer (TIHR) is discussed along with recently measured heterodyne solar absorption spectra in the 10 to 11 micron spectral region

Assessment of Techniques for Measuring Tropospheric H Sub x O Sub y

In its continuing efforts to direct its applications programs towards relevant national needs, NASA is conducting the Tropospheric Chemistry Program, the long-range objective of which is to apply NASA's space technology to assess and predict human impact on the troposphere, particularly on the regional to global scale. One area of required research is instrumentation development, which is aimed at improving the capability to measure important trace gases and aerosols which are key species in the major atmospheric biogeochemical cycles. To focus on specific needs, the Instrumentation Worksphop for H(x)O(y) Tropospheric Species was conducted in August 1982. The workshop discussed current measurement needs and instrument capabilities for H(x)O(y) species, including OH, HO2, and H2O2. The workshop activities and conclusions are documented

Computer simulation of an aircraft-based differential absorption and scattering system for retrieval of SO2 vertical profiles

The feasibility of using the differential absorption and scattering technique from aircraft altitudes for remotely measuring the vertical distribution of SO2 was studied via a computer simulation. Particular care was taken in this simulation to use system parameters (i.e., laser energy, telescope size, etc.) which can be accommodated on an aircraft and can be realized with commercially available technology. The vertical molecular and aerosol profiles were chosen to simulate the types of profiles which might be experienced over a large city. Results are presented on the retrieval of the assumed SO2 profile which show the effects of systematic errors due to interfering gases and aerosols, as well as random errors due to shot noise in the return signal, detector and background noise, and instrument-generated noise

Incompatibility of a comoving Ly-alpha forest with supernova-Ia luminosity distances

Recently Perlmutter et al. suggested a positive value of Einstein's cosmological constant Lambda on the basis of luminosity distances from type-Ia supernovae. However, Lambda world models had earlier been proposed by Hoell & Priester and Liebscher et al. on the basis of quasar absorption-line data. Employing more general repulsive fluids ("dark energy") encompassing the Lambda component we quantitatively compare both approaches with each other. Fitting the SN-data by a minimum-component model consisting of dark energy + dust yields a closed universe with a large amount of dust exceeding the baryonic content constrained by big-bang nucleosynthesis. The nature of the dark energy is hardly constrained. Only when enforcing a flat universe there is a clear tendency to a dark-energy Lambda fluid and the `canonical' value Omega_M = 0.3 for dust. Conversely, fitting the quasar-data by a minimum-component model yields a sharply defined, slightly closed model with a low dust density ruling out significant pressureless dark matter. The dark-energy component obtains an equation-of-state P = -0.96 epsilon close to that of a Lambda-fluid. Omega_M = 0.3 or a precisely flat spatial geometry are inconsistent with minimum-component models. It is found that quasar and supernova data sets cannot be reconciled with each other via (repulsive ideal fluid+dust+radiation)-world models. Compatibility could be reached by drastic expansion of the parameter space with at least two exotic fluids added to dust and radiation as world constituents. If considering such solutions as far-fetched one has to conclude that the quasar absorption line and the SN-Ia constraints are incompatible.Comment: 8 pages, 4 figures, latex, accepted for publication in A&

Membrane penetration and trapping of an active particle

The interaction between nano- or micro-sized particles and cell membranes is of crucial importance in many biological and biomedical applications such as drug and gene delivery to cells and tissues. During their cellular uptake, the particles can pass through cell membranes via passive endocytosis or by active penetration to reach a target cellular compartment or organelle. In this manuscript, we develop a simple model to describe the interaction of a self-driven spherical particle (moving through an effective constant active force) with a minimal membrane system, allowing for both penetration and trapping. We numerically calculate the state diagram of this system, the membrane shape, and its dynamics. In this context, we show that the active particle may either get trapped near the membrane or penetrates through it, where the membrane can either be permanently destroyed or recover its initial shape by self-healing. Additionally, we systematically derive a continuum description allowing to accurately predict most of our results analytically. This analytical theory helps identifying the generic aspects of our model, suggesting that most of its ingredients should apply to a broad range of membranes, from simple model systems composed of magnetic microparticles to lipid bilayers. Our results might be useful to predict mechanical properties of synthetic minimal membranes.Comment: 16 pages, 6 figures. Revised manuscript resubmitted to J. Chem. Phy

Pseudoscalar and vector mesons as q\bar{q} bound states

Two-body bound states such as mesons are described by solutions of the Bethe-Salpeter equation. We discuss recent results for the pseudoscalar and vector meson masses and leptonic decay constants, ranging from pions up to c\bar{c} bound states. Our results are in good agreement with data. Essential in these calculation is a momentum-dependent quark mass function, which evolves from a constituent-quark mass in the infrared region to a current-quark mass in the perturbative region. In addition to the mass spectrum, we review the electromagnetic form factors of the light mesons. Electromagnetic current conservation is manifest and the influence of intermediate vector mesons is incorporated self-consistently. The results for the pion form factor are in excellent agreement with experiment.Comment: 8 pages, 6 .eps figures, contribution to the proceedings of the first meeting of the APS Topical Group on Hadron Physics, Fermilab, Oct. 200

Cosmic String Network Evolution in arbitrary Friedmann-Lemaitre models

We use the velocity-dependent one-scale model by Martins & Shellard to investigate the evolution of a GUT long cosmic string network in arbitrary Friedmann-Lemaitre models. Four representative models are used to show that in general there is no scaling solution. The implications for structure formation are briefly discussed.Comment: 8 pages, 4 postscript figures included, submitted to Phys. Rev.