Energetics of potential heterotrophic metabolisms in the marine hydrothermal system of Vulcano Island, Italy

Values of overall Gibbs free energy of 144 organic oxidation (respiration) and disproportionation (fermentation) reactions are calculated at the temperatures and chemical compositions that exist in nine submarine vents, sediment seeps and geothermal wells in the hydrothermal system of Vulcano Island, Italy. The organic compounds considered here include four carboxylic acids (formic, acetic, propanoic and lactic), two C₅ aldoses (arabinose and xylose), three C₆ aldoses (galactose, glucose and mannose), and 15 protein-forming amino acids (Ala, Arg, Asp, Glu, Gly, His, Ile, Leu, Lys, Met, Phe, Ser, Thr, Tyr, and Val). Oxidation of these compounds is coupled to five redox pairs: O₂/H₂O, , S⁰/H₂S, and Fe₃O₄/Fe²⁺. Energy yields from potential respiration reactions range from 6 to 118 kJ/mol of electrons transferred and show systematic behavior with respect to the terminal electron acceptor. Overall, respiration with O₂ yields the most energy (98–118 kJ/mol e⁻), followed by reactions with (53– 86 kJ/mol e⁻), magnetite (29–91 kJ/mol e⁻), S⁰ (11–33 kJ/mol e⁻) and (6–34 kJ/mol e⁻). Energy yields show little correlation with organic compound family, but are correlated with fluid pH. Variability in energy yields across the nine sites is greatest for Fe(III) reduction and is primarily influenced by pH and the activity of Fe²⁺. In addition to the potential respiration reactions, the energetics of 24 potential fermentation reactions are also calculated. As expected, fermentation reactions generally yield much less energy than respiration. Normalized to the number of moles of carbon transferred, fermentation yields−8 to 71 kJ/mol C, compared with 16 to 531 kJ/mol C for respiration reactions. All respiration and fermentation reactions, except for methionine (Met) fermentation, are exergonic under the in situ hydrothermal conditions and represent a plethora of potential metabolisms for Vulcano’s diverse thermophilic heterotrophs.     

Determination of first-order degradation rate constants from monitoring networks

In this article, different strategies for estimating first-order degradation rate constants from measured field data are compared by application to multiple, synthetic, contaminant plumes. The plumes were generated by numerical simulation of contaminant transport and degradation in virtual heterogeneous aquifers. These sites were then individually and independently investigated on the computer by installation of extensive networks of observation wells. From the data measured at the wells, that is, contaminant concentrations, hydraulic conductivities, and heads, first-order degradation rates were estimated by three 1D centerline methods, which use only measurements located on the plume axis, and a two-dimensional method, which uses all concentration measurements available downgradient from the contaminant source. Results for both strategies show that the true rate constant used for the numerical simulation of the plumes in general tends to be overestimated. Overestimation is stronger for narrow plumes from small source zones, with an average overestimation factor of about 5 and single values ranging from 0.5 to 20, decreasing for wider plumes, with an average overestimation factor of about 2 and similar spread. Reasons for this overestimation are identified in the velocity calculation, the dispersivity parameterization, and off-centerline measurements. For narrow plumes, the one- and the two-dimensional strategies show approximately the same amount of overestimation. For wider plumes, however, incorporation of all measurements in the two-dimensional approach reduces the estimation error. No significant relation between the number of observation wells in the monitoring network and the quality of the estimated rate constant is found for the two-dimensional approach.     

Raman spectra of nitrogen-containing organic compounds obtained in high altitude sites using a portable spectrometer: Possible application for remote robotic Titan studies

Well-resolved Raman spectra of examples of nitrogen-containing compounds were detected using a portable Raman instrument (Ahura First Defender XL) outdoors at a low temperature of −15 °C at an altitude of 2860 m (Pitztall, Austria). The portable Raman spectrometer tested here is equipped with a 785 nm diode laser and fixed frontal probe. Solid forms of formamide, urea, 3-methylpyridine, aniline, indene, 1-(2-aminoethyl)piperazine, benzofuran and indoline were detected unambiguously under field high-mountain conditions. The main Raman features (strong, medium and partially weak bands) were observed at their correct wavenumber positions (spectral resolution 7-10 cm⁻¹) in the range 200-2000 cm⁻¹. The results obtained demonstrate the possibility of applying a miniaturised Raman spectrometer as key instrument for investigating the presence of nitrogen-containing organic compounds and biomolecules under low temperature field conditions. Within the payload designed by ESA and NASA for future missions focusing not only on Mars, Raman spectroscopy will be an important non-destructive analytical tool for the in-situ identification of both organic and inorganic compounds relevant to life detection on planetary surfaces or near sub-surfaces.     

Autoplot: a browser for scientific data on the web

Autoplot is software developed for the Virtual Observatories in Heliophysics to provide intelligent and automated plotting capabilities for many typical data products that are stored in a variety of file formats or databases. Autoplot has proven to be a flexible tool for exploring, accessing, and viewing data resources as typically found on the web, usually in the form of a directory containing data files with multiple parameters contained in each file. Data from a data source is abstracted into a common internal data model called QDataSet. Autoplot is built from individually useful components, and can be extended and reused to create specialized data handling and analysis applications and is being used in a variety of science visualization and analysis applications. Although originally developed for viewing heliophysics-related time series and spectrograms, its flexible and generic data representation model makes it potentially useful for the Earth sciences.     

Industrial specialization and economic performance: A case of Czech microregions

An influential body of literature suggests that economic diversity rather than specialization fuels the economic performance of regions and nations. The authors argue that this hypothesis has no universal applicability and that a more differentiated view is needed. In particular, historical specificity of the local environment and structural characteristics of regional economies should be taken into account. They focus on the effects of industrial specialization on economic performance and the vulnerability of Central European post-communist regions, namely Czech microregions with less than 200,000 inhabitants. They examine whether the economic performance and vulnerability of these regions is fuelled rather by industrial specialization or diversity when controlling for other potential determinants of regional economic performance. Their findings show that the dependence of Czech regions on manufacturing correlates with higher economic performance but also with higher regional vulnerability. In addition, industrial specialization within manufacturing was found to be instrumental for the economic performance of regions with high dependence on manufacturing. With a decreasing share of employment in manufacturing, industrial diversity rather than specialization becomes more valuable for the economic performance of Czech regions.     

Warmer early instrumental measurements versus colder reconstructed temperatures: shooting at a moving target

Comparison of tree-ring-based warm-season temperature reconstructions and their instrumental target data reveals substantial divergence between (warmer) early instrumental measurements and (colder) proxy estimates. Here we detail this systematic misfit for the Northern Hemisphere before 1900 and the European Alps before 1850. Five hypotheses related to both proxy and target uncertainties are presented towards explaining this phenomenon. These include: (1) tree-ring detrending methods, (2) biological persistence in the proxy time-series, (3) uncertainties and instabilities in the growth response to given climatic parameters, (4) reduced instrumental station availability back in time, and (5) instrumental data homogeneity. We suggest that uncertainties in the choice of instrumental targets at the hemispheric scale, and instrumental data inhomogeneities at the Alpine and possibly also the hemispheric-scale are the most important factors in explaining this offset. Assessment of homogeneity at larger scales remains challenging. Attention is drawn to possible warm biases in early thermometer shelters and the relevance of proxy/target discrepancies for understanding and quantifying the amplitude of both recent anthropogenic and past natural forced climate fluctuations.     

Paraxial ray theory in general coordinates

Summary Principles of an alternative approach to the ray theory and paraxial ray approximation (PRA) theory are discussed. Invariant equations for the ray, the eikonal equation and basic equations of the PRA-theory are derived on the basis of Riemannian geometry. Paraxial rays and paraxial time field equations in general curvilinear coordinates are shown as an example of application.     

Anthropogenic contamination of groundwater with nitrate in arid region: case study of southern Hodna (Algeria)

In southern Hodna, an arid region of Algeria, the extension of irrigated agriculture and overexploitation of groundwaters have led to a rupture with traditional land use by pastoralism. Due to the arid conditions, groundwaters are the only water resources for man and irrigation. This study focuses on nitrate contamination of groundwaters and its increase since the last 40 years, on the basis of two archives and recent analyses. The chemical facies of waters is sulphate-chloride, the risk of salinity is moderate to large. The sodicity risk, as estimated by the SAR, is low due to the large salinity and the sandy soil texture. Nitrate contamination of deep groundwater is a clear evidence when recent data are compared to the historical data. From 1996 to 2008, the proportion of samples with NO ₃ ^? concentrations larger than 50 mg/L increases from 24 to 61 %, the proportion of samples with NO ₃ ^? concentrations larger than 100 mg/L increases from 12 to 27 %. The study points at a general contamination of aquifers from anthropic origin: phreatic water was already contaminated when pastoralism was dominant (1967); as population increased and irrigation agriculture developed with large use of N-fertilizers and organic amendments, contamination extended spatially and vertically to deep aquifer. To remediate this contamination, fertilizers should be fractionated and limited to plant requirements on the basis of soil and plant analyses. Excess of irrigation should be avoided. Soil surface should be continuously covered to prevent nitrate leaching. Secondly, more efficient irrigation techniques, such as localized irrigation, should be implemented, with adaptation of crop systems and fertilizer inputs to arid conditions. Farmers should then be trained; simultaneously, local agronomic references that are presently lacking should be acquired.     

The shoreface-connected ridges along the central Dutch coast — part 2: morphological modelling

The hydrodynamic and sediment transport processes on the Dutch inner-shelf were studied on the basis of short- and medium-term (days, month) field experiments during fair-weather and storm conditions. The primary goal of this study was to identify the mechanisms that may be responsible for the formation and maintenance of the shoreface-connected ridges in the study area. The hydrodynamic field observations do not consistently support existing theoretical models explaining the formation of such ridges. Instead, the water motion appears to be dominated by wind- and density-driven effects. A review of literature indicates that other field studies also fail to observe the flow response expected from theory. Sediment transport during fair-weather is very episodic, with bed load transport slightly dominant over suspended load transport. The sediment transport processes during storms are dominated by the mean fluxes, with waves acting as a stirring mechanism. The contribution of wave-oscillatory fluxes cannot be neglected and may be directed with and against the waves. Long-wave fluxes are present, but very small.     

Limits on the size and orbit distribution of main belt comets

The first of a new class of objects now known as main belt comets (MBCs) or “activated asteroids” was identified in 1996. The seven known members of this class have orbital characteristics of main belt asteroids yet exhibit dust ejection like comets. In order to constrain their physical and orbital properties we searched the Thousand Asteroid Light Curve Survey (TALCS; Masiero, J.R., Jedicke, R., Durech, J., Gwyn, S., Denneau, L., Larsen, J. [2009]. Icarus 204, 145-171) for additional candidates using two diagnostics: tail and coma detection. This was the most sensitive MBC survey effort to date, extending the search from MBCs with H ∼ 18 (D ∼ 1 km) to MBCs as small as H ∼ 21 (D ∼ 150 m).We fit each of the 924 objects detected by TALCS to a PSF model incorporating both a coma and nuclear component to measure the fractional contribution of the coma to the total surface brightness. We determined the significance of the coma detection using the same algorithm on a sample of null detections of comparable magnitude and rate of motion. We did not identify any MBC candidates with this technique to a sensitivity limit on the order of cometary mass loss rate of about 0.1 kg/s.Our tail detection algorithm relied on identifying statistically significant flux in a segmented annulus around the candidate object. We show that the technique can detect tail activity throughout the asteroid belt to the level of the currently known MBCs. Although we did not identify any MBC candidates with this technique, we find a statistically significant detection of faint activity in the entire ensemble of TALCS asteroids. This suggests that many main belt asteroids are active at very low levels.Our null detection of MBCs allows us to set 90% upper confidence limits on the number distribution of MBCs as a function of absolute magnitude, semi-major axis, eccentricity, and inclination. There are ?400,000 MBCs in the main belt brighter than H_V = 21 (∼150-m in diameter) and the MBC:MBA ratio is ?1:400.We further comment on the ability of observations to meaningfully constrain the snow line’s location. Under some reasonable and simple assumptions we claim 85% confidence that the contemporary snow line lies beyond 2.5 AU.