ITERA: IDL tool for emission-line ratio analysis

We present a new software tool to enable astronomers to easily compare observations of emission-line ratios with those determined by photoionization and shock models, ITERA, the IDL Tool for Emission-line Ratio Analysis. This tool can plot ratios of emission lines predicted by models and allows for comparison of observed line ratios against grids of these models selected from model libraries associated with the tool. We provide details of the libraries of standard photoionization and shock models available with ITERA, and, in addition, present three example emission-line ratio diagrams covering a range of wavelengths to demonstrate the capabilities of ITERA. ITERA, and associated libraries, is available from http://www.brentgroves.net/itera.html.     

Diffuse X-ray background measurements in the energy range 2–18 keV

Rocket measurements, of the diffuse X-ray background in the energy range 2–18 keV, conducted from Thumba Equatorial Rocket Launching Station (TERLS), India, are presented. The estimates of the cosmic background are derived by the method which employs the Earth and its atmosphere as a shutter to intercept the celestial X-rays. The results are shown to be consistent with a power law photon spectrum.13.6 _–3.3 ^+4.3 E ^{–1.73±0.15} photons/cm²-sec-keV-ster the spectrum being much flatter than that observed at higher energies.     

On the relation between orbital structure and observed bar morphology

We investigate the morphological relation between the orbits of the central family of periodic orbits ( x ₁ family) and the bar itself using models of test particles moving in a barred potential. We show that different bar morphologies may have as a backbone the same set of x ₁ periodic orbits. We point out that by populating initially axisymmetric stellar discs exponentially with test particles in circular, or almost circular motion, we may end up with a response bar which reveals a shape different in crucial details from that of the individual stable x ₁ orbits. For example, a bar model in which the x ₁ orbits are pure ellipses may have a much more complicated response morphology. This depends on the particular invariant curves around x ₁, which are populated in each model.     

Robertson-Walker-type universes with conformally-invariant scalar field

Recently, Innaiah and Reddy (1985) obtained a flat Robertson-Walker-type solution for the Einstein field equations with the trace-free energy-momentum tensor of a conformally invariant scalar field as source. Here we show that the field equations force the scalar field to be independent of time. Furthermore, we obtain open and closed Robertson-Walker-type solutions and observe that, once again, the scalar field has to be independent of time.     

Abbau von Monochlornitrobenzolen durch Pseudomonas acidovorans CA50

Degradation of Monochloronitrobenzenes by Pseudomonas acidovorans CA50 Pseudomonas acidovorans strain CA50 was used for degradation experiments with monochloronitrobenzenes in aerobic batch culture. The monochloronitrobenzenes were reduced to the corresponding monochloroanilines. The reduction only occurred with an additional carbon and nitrogen source. Chlorocatechols were found to be present. 3-Chlorocatechol accumulated in the presence of 2-chloroaniline, whereas 4-chlorocatechol was an intermediate metabolite of 3- and 4-chloroaniline. Contrary to the degradation of monochloronitrobenzenes, Pseudomonas acidovorans strain CA50 used the monochloroanilines as a sole source of carbon, energy, and nitrogen for growth. The oxidation of monochloroanilines was not repressed by the additional substrates. 2-Chloronitrobenzene was degraded with the lowest rate because of the low turnover of the intermediate metabolite 2-chloroaniline. 3-Chloronitrobenzene was completely degraded also in a mixture. A complete degradation of 4-chloronitrobenzene was achieved only when it was the sole chloronitrobenzene. The results suggest that a dechlorination and mineralization of monochlornitrobenzenes is possible, but for a final proof, further investigations will be necessary.     

Stormflow concentration–discharge dynamics of suspended sediment and dissolved phosphorus in an agricultural watershed

Concentration–discharge (C-Q) relationships are an effective tool for identifying watershed biogeochemical source and transport dynamics over short and long timescales. We examined stormflow C-Q, hysteresis, and flushing patterns of total suspended sediment (TSS) and soluble reactive phosphorus (SRP) in two stream reaches of a severely impaired agricultural watershed in northeastern Wisconsin, USA. The upper watershed reach—draining a relatively flat, row crop-dominated contributing area—showed predominantly anti-clockwise TSS hysteresis during storms, suggesting that particulate materials were mobilized more from distal upland sources than near- and in-channel areas. In contrast, the incised lower watershed reach produced strong TSS flushing responses on the rising limb of storm hydrographs and clockwise hysteresis, signalling rapid mobilization of near- and in-channel materials with increasing event flows. C-Q relationships for SRP showed complex patterns in both the upper and lower reaches, demonstrating largely non-linear chemodynamic C-Q behaviour during events. As with TSS, anti-clockwise SRP hysteresis in the upper reach suggested a delay in the hydrologic connectivity between SRP sources and the stream, with highly variable SRP concentrations during some events. A broad range of clockwise, anti-clockwise, and complex SRP hysteresis patterns occurred in the lower watershed, possibly influenced by in-channel legacy P stores and connection to tile drainage networks in the lower watershed area. Total suspended sediment and SRP responses were also strongly related to precipitation event characteristics including antecedent precipitation, recovery period, and precipitation intensity, highlighting the complexity of stormflow sediment and phosphorus responses in this severely impaired agricultural stream.     

The ALOMAR Rayleigh/Mie/Raman lidar: objectives, configuration, and performance

We report on the development and current capabilities of the ALOMAR Rayleigh/Mie/Raman lidar. This instrument is one of the core instruments of the international ALOMAR facility, located near Andenes in Norway at 69°N and 16°E. The major task of the instrument is to perform advanced studies of the Arctic middle atmosphere over altitudes between about 15 to 90 km on a climatological basis. These studies address questions about the thermal structure of the Arctic middle atmosphere, the dynamical processes acting therein, and of aerosols in the form of stratospheric background aerosol, polar stratospheric clouds, noctilucent clouds, and injected aerosols of volcanic or anthropogenic origin. Furthermore, the lidar is meant to work together with other remote sensing instruments, both ground- and satellite-based, and with balloon- and rocket-borne instruments performing in situ observations. The instrument is basically a twin lidar, using two independent power lasers and two tiltable receiving telescopes. The power lasers are Nd:YAG lasers emitting at wavelengths 1064, 532, and 355 nm and producing 30 pulses per second each. The power lasers are highly stabilized in both their wavelengths and the directions of their laser beams. The laser beams are emitted into the atmosphere fully coaxial with the line-of-sight of the receiving telescopes. The latter use primary mirrors of 1.8 m diameter and are tiltable within 30° off zenith. Their fields-of-view have 180 rad angular diameter. Spectral separation, filtering, and detection of the received photons are made on an optical bench which carries, among a multitude of other optical components, three double Fabry-Perot interferometers (two for 532 and one for 355 nm) and one single Fabry-Perot interferometer (for 1064 nm). A number of separate detector channels also allow registration of photons which are produced by rotational-vibrational and rotational Raman scatter on N₂ and N₂+O₂ molecules, respectively. Currently, up to 36 detector channels simultaneously record the photons collected by the telescopes. The internal and external instrument operations are automated so that this very complex instrument can be operated by a single engineer. Currently the lidar is heavily used for measurements of temperature profiles, of cloud particle properties such as their altitude, particle densities and size distributions, and of stratospheric winds. Due to its very effective spectral and spatial filtering, the lidar has unique capabilities to work in full sunlight. Under these conditions it can measure temperatures up to 65 km altitude and determine particle size distributions of overhead noctilucent clouds. Due to its very high mechanical and optical stability, it can also employed efficiently under marginal weather conditions when data on the middle atmosphere can be collected only through small breaks in the tropospheric cloud layers.     

Diffusion of divalent cations in garnet: multi-couple experiments

We demonstrate the possibility of studying several diffusion couples in a single run, i.e. under almost similar P–T–t– conditions, allowing direct comparison of the diffusion rates in different diffusion couples. Thus the duration of experimental study and the risk of failure of expensive experimental equipment can be decreased considerably. The diffusion experiments were carried out in piston-cylinder apparatus. Gem-quality garnets of almandine, spessartine and grossular compositions together with inclusion-rich eclogitic garnets were embedded in a powder of natural pyrope and annealed together under dry conditions at P = 1.9–3.2 GPa and T = 1,070–1,400°C. Diffusion profiles were measured by electron microprobe and fitted numerically on the basis of multicomponent diffusion theory. The datasets derived from different diffusion couples yields parameters of the Arrhenius equation for Ca, Mg and Fe in natural eclogitic garnets and Mg, Mn and Fe in gem-quality garnets. We have also studied the effect of grain-boundary diffusion in the sintered pyrope matrix on interdiffusion on the basis of 2D modeling. Under conditions analogous to those of our experimental runs, we show that observed irregularities in some measured diffusion profiles (not applied for the diffusion modeling) can be directly related to the superposition of local grain-boundary diffusion on dominant volume diffusion.     

The “North American shale composite”: Its compilation,major and trace element characteristics

The compilation and major element composition of the “North American shale composite” (NASC) are reported for the first time, along with redeterminations for the REE and selected other elements by modern, high precision analytical methods. The NASC is not strictly of North American origin; 5 of the constituent samples are from Africa and Antarctica, and 15 are from unspecified locations. The major element composition of the NASC compares quite closely with other average shale compositions. New analyses of the NASC document that significant portions of the REE and some other trace elements are contained in minor phases (zircon and possibly other minerals) and that their uneven distribution in the NASC powder appears to have resulted in heterogeneity among analyzed aliquants. The results of this study show that the REE distributions of detrital sediments can be dependent to some extent on their minor mineral assemblages and the sedimentological factors that control these assemblages. Consequently, caution should be exercised in the interpretation of the REE distributions of sediment samples as they may be variable and biased relative to average REE distribution of the crustal rocks supplying detritus. These effects appear to be largely averaged out in sediment composites, with the result that their REE distributions are more likely to be representative of their provenances.