Conflict between background matching and social signalling in a colour-changing freshwater fish

The ability to change coloration allows animals to modify their patterning to suit a specific function. Many freshwater fishes, for example, can appear cryptic by altering the dispersion of melanin pigment in the skin to match the visual background. However, melanin-based pigments are also used to signal dominance among competing males; thus colour change for background matching may conflict with colour change for social status signalling. We used a colour-changing freshwater fish to investigate whether colour change for background matching influenced aggressive interactions between rival males. Subordinate males that had recently darkened their skin for background matching received heightened aggression from dominant males, relative to males whose coloration had not changed. We then determined whether the social status of a rival male, the focal male's previous social status, and his previous skin coloration, affected a male's ability to change colour for background matching. Social status influenced skin darkening in the first social encounter, with dominant males darkening more than subordinate males, but there was no effect of social status on colour change in the second social encounter. We also found that the extent of skin colour change (by both dominant and subordinate males) was dependent on previous skin coloration, with dark males displaying a smaller change in coloration than pale males. Our findings suggest that skin darkening for background matching imposes a significant social cost on subordinate males in terms of increased aggression. We also suggest that the use of melanin-based signals during social encounters can impede subsequent changes in skin coloration for other functions, such as skin darkening for background matching

Colour change and assortment in the western rainbowfish

Grouping behaviour is widespread across the animal kingdom, and is known to reduce an individual's risk of predation, for example through predator confusion. Theory predicts that individuals that are different in appearance to the rest of the group are at a greater risk of predation because they are more conspicuous to predators (the ‘oddity’ effect). Thus, animals should choose group mates that are the most similar in appearance to themselves. Another common antipredator tactic is crypsis (camouflage). Fishes are capable of changing colour to match their visual background, but few studies have examined how this might influence shoaling decisions, particularly in the context of the oddity effect. We induced colour pattern changes in a colourful species of freshwater fish, the western rainbowfish, Melanotaenia australis, by maintaining fish in dark and pale aquaria for 2 weeks. Analysis of the proportion of black body pigmentation confirmed that rainbowfish in dark environments developed darker colour patterns than those held in pale environments. We then conducted behavioural observations to determine whether fish subsequently based their shoaling decisions on body coloration. We found that rainbowfish preferred to shoal with similar individuals; fish that had been held in dark aquaria preferred to shoal with other dark fish and fish from pale aquaria preferred other pale fish. Our findings are consistent with the predictions of the oddity effect and demonstrate how morphological colour pattern changes and behavioural decisions interact to mediate antipredator tactics in fish

Solar sustained plasma/absorber conceptual design

A space power system concept was evaluated which uses concentrated solar energy to heat a working fluid to temperatures as high as 4000 K. The high temperature working fluid could be used for efficient electric power production in advanced thermal or magnetohydrodynamic conversion cycles. Energy absorber configurations utilizing particles or cesium vapor absorber material were investigaed. Results of detailed radiant heat transfer calculations indicated approximately 86 percent of the incident solar energy could be absorbed within a 12-cm-dia flowing stream of gas borne carbon particles. Calculated total energy absorption in the cesium vapor seeded absorber configuration ranged from 34 percent to 64 percent of the incident solar energy. Solar flux concentration ratios of between approximately 3000 and 10,000 will be required to sustain absorber temperatures in the range from 3000 K to 4000 K

Measurement Error In Cross-Sectional and Longitudinal Labor Market Surveys: Results From Two Validation Studies

This paper reports evidence on the error properties of survey reports of labor market variables such as earnings and work hours. Our primary data source is the PSID Validation Study, a two-wave panel survey of a sample of workers employed by a large firm which also allowed us access to its very detailed records of its workers earnings. etc. The second data source uses individuals' 1977 and 1978 (March Current Population Survey) reports of earnings, matched to Social Security earnings records. In both data sets, individuals: reports of earnings are fairly accurately reported, and the errors are negatively related to true earnings. The latter property reduces the bias due to measurement error when earnings are used as an independent variable, but (unlike the classical-error case) leads to some bias when earnings are the dependent variable. Measurement-error-induced biases when change in earnings is the variable of interest are larger, but not dramatically so. Various measures of hourly earnings were much less reliable than annual earnings. Retrospective reports of unemployment showed considerable under-reporting, even of long spells.

A multi-sensor analysis of Nimbus 5 data on 22 January 1973

The Nimbus 5 meteorological satellite carried aloft a full complement of radiation sensors, the data from which were analyzed and intercompared during orbits 569-570 on 22 January 1973. The electrically scanning microwave radiometer (ESMR) which sensed passive microwave radiation in the 19.35 GHz region, delineated rain areas over the ocean off the U.S. east coast, in good agreement with WSR-57 and FPS-77 radar imagery and permitted the estimation of rainfall rates in this region. Residual ground water in the lower Mississippi Valley, which resulted from abnormal rainfall in previous months, was indicated under clear sky conditions by soil brightness temperature values in the Nimbus 5 ESMR and U.S. Air Force Data Acquisition and Processing Program (DAPP) IR data. The temperature-humidity infrared radiometer showed the height and spatial configuration of frontal clouds along the east coast and outlined the confluence of a polar jet stream with a broad sub-tropical jet stream along the U.S. Gulf Coast. Temperature profiles from three vertical temperature sounders, the infrared temperature profile radiometer (ITPR), the Nimbus E microwave spectrometer (NEMS) and the selective chopper radiometer (SCR) were found to be in good agreement with related radiosonde ascents along orbit 569 from the sub-tropics to the Arctic Circle

A multisensor analysis of Nimbus-5 data recorded on 22 January 1973

The Nimbus 5 meteorological satellite has a full complement of radiation sensors. Data from these sensors were analyzed and intercompared for orbits 569 and 570. The electrically-scanning microwave radiometer (19.35-GHz region) delineated rain areas over the ocean off the U.S. east coast, in good agreement with radar imagery, and permitted the estimation of rainfall rates in this region. Residual ground water, from abnormal rainfall in the lower Mississippi Valley, was indicated under clear sky conditions by soil brightness temperature values in the Nimbus 5 electrically scanning microwave radiometer and U.S. Air Force Data Acquisition and Processing Program infrared data. The temperature-humidity infrared radiometer (6.7 micron and 11 micron) showed the height and spatial configuration of frontal clouds along the east coast and outlined the confluence of a polar jet stream with a broad subtropical jet stream along the U.S. Gulf Coast. Temperature profiles from three vertical temperature sounders are found to be in good agreement with related radiosonde ascents along orbit 569 from the subtropics to the Arctic Circle

Local u'g'r'i'z' Standard Stars in the Chandra Deep Field-South

Because several observing programs are underway in various spectral regimes to explore the Chandra Deep Field South (CDF-S), the value of local photometric standards is obvious. As part of an NOAO Surveys Program to establish u'g'r'i'z' standard stars in the southern hemisphere, we have observed the central region of the CDF-S to create local standards for use by other investigators using these filters. As a courtesy, we present the CDF-S standards to the public now, although the main program will not finish until mid-2005.Comment: Accepted by AJ (scheduled for October 2003 issue). 26 pages, 5 tables, 5 figures. High resolution version of Figure 7 available at http://home.fnal.gov/~dtucker/Southern_ugriz/index.htm

The crystal and molecular structure of the bis(4-N, N1-dimethylaminopyridine) solvate of disalicylicacidatobis(nitrotodioxouranium)(VI)

The structure of the title compound [(C7H4NO8U)(C7H11N2)]2 has been determined by Patterson and Fourier methods from single crystal X-ray diffraction data collected on a four-circle diffractometer. Full-matrix least-squares refinement yielded a final conventional R of 0.041 for 2189 reflections. The complex crystallizes in the space group P with a = 11.004(5), b = 9.981(5), c = 9.928(5) Å, α = 119.6(3), β = 107.7(3), γ = 81.9(3)°, Dm = 2.17, Dc = 2.173g cm−3. The structure is dimeric. The uranium atoms are eight-coordinate and are bridged via centrosymmetrically related carboxylic oxygen atoms. The nitrate group is bidentate and the average U---O (ligand) distance is 2.463 Å. Hydrogen bonding of the type N---HO links two dimethyl-aminopyridine molecules to the dimer

The structure of aliphatic amine adducts of uranyl acetylacetonate. III. Dioxobis(2,4-pentanedionato)mono (2-N-isopropylaminopentan-4-one)uranium(VI)

Introduction: In two earlier structural determinations of compounds of this type we have shown that the conformation of the adduct moiety is dependent on the formation of intramolecular N-H...0 hydrogen bonds (part I: Haigh, Nassimbeni, Pauptit, Rodgers & Sheldrick, 1976; part II: Nassimbeni, Orpen, Pauptit, Rodgers & Haigh, 1977). We have carried out the present analysis to study the conformational effects on the ligand brought about by the steric influence of an isopropyl substituent at N