Spatial distribution of nitrate and related factors in the High Plains Aquifer,Texas

Utilizing geographic information systems (GIS) and statistics, objectives of this study were to evaluate: (a) the spatial distribution of nitrate concentrations in groundwater, and (b) associations between nitrate concentrations and: proximity to playa lakes, hydraulic conductivity of soil, well depth, and land use in the High Plains Aquifer, Texas. Data were compiled from wells sampled during 2000–2008. Nitrate concentrations in approximately 9% of wells exceeded the maximum contaminant level for drinking water. Concentrations were generally higher beneath urban and agricultural land, under permeable soil, and in shallow wells (especially in the southern part of the study area). However, concentrations were lower near playa lakes. While playas focus recharge to groundwater, denitrification in reducing environments lower nitrate concentrations beneath them. This study identifies areas vulnerable to nitrate contamination that warrant continued monitoring and mitigation efforts.     

我国中部和南部地区降水再循环率评估

利用1976～1995 年20 年NCEP 再分析资料,对我国中、南部地区降水再循环率进行了评估,发现长江上游总的降雨有20%来自我国中、南部地区水汽蒸发,长江中下游总的降雨则有40%来自这一地区. 降水再循环率有很强的季节变化规律,8、9、10三个月的降水再循环率最高,达四成左右,而5、6、7三个月的降水再循环率不到四分之一.蒸发率和降水再循环率在20年中均有增加的趋势,这可能与气候变暖有关.     

Reconciling the centimeter- and millimeter-wavelength ammonia absorption spectra under jovian conditions: Extensive millimeter-wavelength measurements and a consistent model

Over 1000 laboratory measurements of the 2-4 mm-wavelength opacity of ammonia have been made under simulated jovian atmospheric conditions using a high-precision laboratory system developed at Georgia Tech. These laboratory measurements of the opacity of ammonia were made of various gas mixtures of hydrogen (∼77.5-85.5%), helium (∼12.5-13.5%), and ammonia (1-10%) at pressures between 1 and 3 bars and temperatures between 200 and 300 K. Laboratory measurements were also made of the opacity of pure ammonia at pressures between 0.05 and 1 bar and temperatures between 200 and 300 K. Using these millimeter-wavelength measurements and close to 2000 cm-wavelength measurements made by Hanley et al. (2009), a new consistent model has been developed to accurately characterize the absorption spectra of ammonia in a hydrogen/helium atmosphere in the 1 mm to 30 cm wavelength range. This model can be used in the 1-30 cm wavelength range at pressures up to 20 bars and temperatures from 200 to 500 K and in the 1 mm to 1 cm wavelength range at pressures up to 3 bars and temperatures from 200 to 300 K. These measurements and the accompanying model will enable better interpretation of the centimeter- and millimeter-wavelength emission spectra of the jovian planets.     

Non-LTE radiative transfer for sub-millimeter water lines in Comet 67P/Churyumov-Gerasimenko

The European Space Agency (ESA) Rosetta spacecraft (Schulz, R., Alexander, C., Boehnhardt, H., Glassmeier, K.H. (Eds.) [2009]. “ROSETTA - ESA”) will encounter Comet 67P/Churyumov-Gerasimenko in 2014 and spend the next 18 months in the vicinity of the comet, permitting very high spatial and spectral resolution observations of the coma and nucleus. During this time, the heliocentric distance of the comet will change from ∼3.5 AU to ∼1.3 AU, accompanied by an increasing temperature of the nucleus and the development of the coma. The Microwave Instrument for the Rosetta Orbiter (MIRO) will observe the ground-state rotational transition (1₁₀-1₀₁) of H₂¹⁶O at 556.936 GHz, the two isotopologues H₂¹⁷O and H₂¹⁸O and other molecular transitions in the coma during this time (Gulkis, S. et al., [2007]. MIRO: Microwave Instrument for Rosetta Orbiter. Space Sci. Rev. 128, 561-597).The aim of this study is to simulate the water line spectra that could be obtained with the MIRO instrument and to understand how the observed line spectra with various viewing geometries can be used to study the physical conditions of the coma and the water excitation processes throughout the coma. We applied an accelerated Monte Carlo method to compute the excitations of the seven lowest rotational levels (1₀₁, 1₁₀, 2₁₂, 2₂₁, 3₀₃, 3₁₂, and 3₂₁) of ortho-water using a comet model with spherically symmetric water outgassing, density, temperature and expansion velocity at three different heliocentric distances 1.3 AU, 2.5 AU, and 3.5 AU. Mechanisms for the water excitation include water-water collisions, water-electron collisions, and infrared pumping by solar radiation.Synthetic line spectra are calculated at various observational locations and directions using the MIRO instrument parameters. We show that observations at varying viewing distances from the nucleus and directions have the potential to give diagnostic information on the continuum temperature and water outgassing rates at the surface of the nucleus, and the gas density, expansion velocity, and temperature of the coma as a function of distance from the nucleus. The gas expansion velocity and temperature affect the spectral line width and frequency shift of the line from the rest frequency, while the gas density (which is directly related to the outgassing rate) and the line excitation temperature determine the antenna temperature of the absorption and emission signal in the line profile.     

A laboratory study of the bidirectional reflectance from particulate samples

The Hapke (Hapke, B. [1981]. J. Geophys. Res. 86, 3039-3054) photometric model and its modifications are widely used to characterize telescopic, spacecraft, and laboratory observations of the bidirectional reflectance of particulate surfaces. Following work and methods laid out in a companion paper (Helfenstein, P., Shepard, M.K. [2011]. Icarus, in press), we deconstruct the Hapke model and, separating all empirical and ad hoc parameters (opposition surge, particle phase function, surface roughness), combine them into a single parameter called the surface phase function, F(α). We illustrate how to extract this function from scattering data sets acquired with the Bloomsburg University Goniometer (BUG). We show how this method can be used to rapidly and accurately characterize bidirectional reflectance data sets from laboratory and spacecraft measurements, often giving better fits to the data. We examine samples with strong color contrasts in different wavelengths. This allows us to examine the exact same surface, changing only the albedo to investigate how the amplitude and the detailed shape of the surface phase function might systematically depend on wavelength and albedo. We also examine the changes in scattering behavior that result when samples are compacted and find the surface phase function and single scattering albedo to be significantly changed. We suggest that these observations support the hypothesis that much of the scattering behavior attributed to the single particle phase function is instead cause by the surface micro-structure.     

Double Relics in the Outskirts of A3376: Accretion Flows Meet Merger Shocks?

The case of spectacular ring-like double radio relics in the merging, rich galaxy cluster A3376 is of great interest to study non-thermal phenomena at cluster outskirts. We present the first low frequency (330 and 150 MHz) images of the double relics using the GMRT. With our GMRT 330 MHz map and the VLA 1400 MHz map (Bagchi et al. 2006), we have constructed and analyzed the distribution of spectral indices over the radio relics. We find flat spectral indices at the outer edges of both the relics and a gradual steepening of spectral indices toward the inner regions. This supports the model of outgoing merger shock waves. The eastern relic has a complex morphology and spectral index distribution toward the inner region. This will be discussed in the context of the effect of large-scale accretion flows on the outgoing merger shocks as reported in the recent simulations.     

First encounter with a live male blanket octopus: The world's most sexually size‐dimorphic large animal

The first encounter with a live male blanket octopus, Tremoctopus violaceus Chiaie, 1830, illustrates the most extreme example of sexual size‐dimorphism in a non‐microscopic animal. Females attain sizes of up to 2 m long—almost 2 orders of magnitude larger than the 2.4‐cm‐long male. Weight ratios between the sexes are at least 10 000:1 and are likely to reach 40 000:1. Sexual selection and the unique defensive strategy of carrying cnidarian stinging tentacles may both have contributed to the evolution of this extreme size‐dimorphism. Such dimorphism is not seen in any other animal remotely as large.     

Critical depths for passage in braided rivers,Canterbury, New Zealand

Riffles and points of divergence of branch channels in braided rivers are critical controls upon passage of fish and recreational boats because they are points at which depths are at a minimum. Depths on randomly selected riffles were measured in braided reaches of the Ashley, Hurunui, and Rakaia Rivers and related to discharge; minimum depths encountered in extended reaches of these rivers at a range of flows have also been measured. The data can be used to predict minimum available passage depths at a specified flow, or conversely, to predict the discharge required to maintain a specified minimum passage depth. However, presently available estimates of critical minimum depths required for various instream uses (migration of salmonids, jetboating) appear excessively conservative, and minimum depth requirements must be more accurately determined before instream flow needs can be properly assessed.