Differential effects of salinity changes on two estuarine fishes,Leiostomus xanthurus andMicropogonias undulatus

Salinity fluctuation has been proposed as an important determinant of estuarine fish distribution. To test this idea, we compared distribution, behavioral preference and physiological sensitivity of two juvenile estuarine fishes, spot (Leiostomus xanthurus) and croaker (Micropogonias undulatus), with respect to salinity change. In field collections, spot: croaker ratios were positively correlated with salinity variation. Subsequent behavioral observations revealed that croaker tend to cross a 10‰ salinity gradient less often than spot. We proposed that energetic costs of salinity adaptation may be higher for croaker, resulting in the observed avoidance behavior. Oxygen consumption rates over rapid salinity fluctuations showed no significant differences in metabolic response between species, although there was some indication that sensitivity changes with fish size. Apparently, juvenile spot and croaker are well-equipped to withstand extreme changes in salinity. We conclude that environmental factors correlated with salinity change may be responsible for distribution differences between these two abundant species.     

The Berkeley parasitic SETI Program

Parasitic programs for the Search for Extraterrestrial Intelligence (SETI), carried out concurrently with conventional radio astronomical observing programs, can be an attractive and cost-effective means of exploring the large multidimensional search space intrinsic to this effort. We describe a microprocessor-based automated SETI acquisition system which searches for and records spectra of narrowband signals in the IF band of an observatory receiver. Data taken with this system over 35 days at the Hat Creek Radio Observatory at 1612 MHz are discussed. Out of approximately 10⁵ spectra processed during this period, 4000 were identified by the system as containing narrowband signals and were recorded. Subsequent analysis indicates that over 3900 of these are due to local RF contamination. The remainder are undergoing further investigation.     

A new approach for linking event‐based upland sediment sources to downstream suspended sediment transport

In this study, we proposed a new approach for linking event sediment sources to downstream sediment transport in a watershed in central New York. This approach is based on a new concept of spatial scale, sub‐watershed area (SWA), defined as a sub‐watershed within which all eroded soils are transported out without deposition during a hydrological event. Using (rainfall) event data collected between July and November, 2007 from several SWAs of the studied watershed, we developed an empirical equation that has one independent variable, mean SWA slope. This equation was then used to determine event‐averaged unit soil erosion rate, Q_S/A, (in kg/km²/hr) for all SWAs in the studied watershed and calculate event‐averaged gross erosion E_ea (in kg/hr). The event gross erosion E_t (in kilograms) was subsequently computed as the product of E_ea and the mean event duration, T (in hours) determined using event hydrographs at the outlet of the studied watershed. Next, we developed two linear sediment rating curves (SRCs) for small and big events based on the event data obtained at the watershed outlet. These SRCs, together with T, allowed us to determine event sediment yield SY_e (in kilograms) for all events during the study period. By comparing E_t with SY_e, developing empirical equations (i) between E_t and SY_e and (ii) for event sediment delivery ratio, respectively, we revealed the event dynamic processes connecting sediment sources and downstream sediment transport. During small events, sediment transport in streams was at capacity and dominated by the deposition process, whereas during big events, it was below capacity and controlled by the erosion process. The key of applying this approach to other watersheds is establishing their empirical equations for Q_S/A and appropriately determining their numbers of SWAs. Copyright © 2011 John Wiley & Sons, Ltd.     

Loss on ignition as a method for estimating organic and carbonate content in sediments: reproducibility and comparability of results

Five test runs were performed to assess possible bias when performing the loss on ignition (LOI) method to estimate organic matter and carbonate content of lake sediments. An accurate and stable weight loss was achieved after 2 h of burning pure CaCO₃ at 950 °C, whereas LOI of pure graphite at 530 °C showed a direct relation to sample size and exposure time, with only 40-70% of the possible weight loss reached after 2 h of exposure and smaller samples losing weight faster than larger ones. Experiments with a standardised lake sediment revealed a strong initial weight loss at 550 °C, but samples continued to lose weight at a slow rate at exposure of up to 64 h, which was likely the effect of loss of volatile salts, structural water of clay minerals or metal oxides, or of inorganic carbon after the initial burning of organic matter. A further test-run revealed that at 550 °C samples in the centre of the furnace lost more weight than marginal samples. At 950 °C this pattern was still apparent but the differences became negligible. Again, LOI was dependent on sample size.An analytical LOI quality control experiment including ten different laboratories was carried out using each laboratory's own LOI procedure as well as a standardised LOI procedure to analyse three different sediments. The range of LOI values between laboratories measured at 550 °C was generally larger when each laboratory used its own method than when using the standard method. This was similar for 950 °C, although the range of values tended to be smaller. The within-laboratory range of LOI measurements for a given sediment was generally small. Comparisons of the results of the individual and the standardised method suggest that there is a laboratory-specific pattern in the results, probably due to differences in laboratory equipment and/or handling that could not be eliminated by standardising the LOI procedure.Factors such as sample size, exposure time, position of samples in the furnace and the laboratory measuring affected LOI results, with LOI at 550 °C being more susceptible to these factors than LOI at 950 °C. We, therefore, recommend analysts to be consistent in the LOI method used in relation to the ignition temperatures, exposure times, and the sample size and to include information on these three parameters when referring to the method.     

Health profiles of Hamilton: Spatial characterisation of neighbourhoods for health investigations

This paper is part of a larger research program which employs a mixed-methods approach to study the determinants of health at the local level using specific neighborhoods in Hamilton, Ontario, Canada. In this paper, multivariate, spatial statistical techniques and geographic information systems are used to address questions about the characterization of neighbourhoods, based on socioeconomic determinants of health and risk factors such as smoking. While neighbourhood characterization has been a component of public health surveillance for some time, geostatistical techniques can now be used to derive more accurate representation of neighbourhoods for use in subsequent analysis. We utilize principal components analysis to reduce the data and extract the components that represent the underlying local processes. Principal components are also overlayed on comparative mortality figures to visualize where the socio-demographic determinants of health correspond spatially with mortality patterns. Predicted values from the components are then analysed for spatial clustering using local indicators of spatial association. The findings reveal a pattern of distinct neighbourhoods that will be used in subsequent quantitative and qualitative stages in the larger research programme. The results can also be used to inform public health policy and to target public health interventions.     

Bone isotope ratios and their bearing on elite privilege among the Classic Maya

This article discusses dietary patterns among the Classic Maya as they are revealed by stable carbon and nitrogen isotope ratios preserved in human bone. Skeletal samples are drawn from seven sites: Uaxactun, Holmul, Baking Pot, Barton Ramie, Siebal, Altar de Sacrificios, and Copán. The isotopic results indicate that Maya nutrition was not so much socially dictated as it was spatially determined; i.e., neither class nor gender nor chronological context are significant factors of isotopic variation when compared to geographic location. These data specifically challenge the notion that Maya elites had quantitative dietary privileges; they do, however, allow for the existence of qualitative privileges. Micro-environmental factors might account for the regional groupings defined, but ultimately, settlement density is considered a more significant variable. © 1997 John Wiley & Sons, Inc.     

Formation Flying for a Fresnel Lens Observatory Mission

The employment of a large area Phase Fresnel Lens (PFL) in a gamma-ray telescope offers the potential to image astrophysical phenomena with micro-arcsecond (μ^′′) angular resolution [1]. In order to assess the feasibility of this concept, two detailed studies have been conducted of formation flying missions in which a Fresnel lens capable of focussing gamma-rays and the associated detector are carried on two spacecraft separated by up to 10⁶ km. These studies were performed at the NASA Goddard Space Flight Center Integrated Mission Design Center (IMDC) which developed spacecraft, orbital dynamics, and mission profiles. The results of the studies indicated that the missions are challenging but could be accomplished with technologies available currently or in the near term. The findings of the original studies have been updated taking account of recent advances in ion thruster propulsion technology.