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Physics and Astronomy60%

Selected Abstracts

Biochemical universality of living matter and its metabolic implications

FUNCTIONAL ECOLOGY, Issue 4 2005
A. M. MAKARIEVA
Summary 1Recent discussions of metabolic scaling laws focus on the model of West, Brown & Enquist (WBE). The core assumptions of the WBE model are the size-invariance of terminal units at which energy is consumed by living matter and the size-invariance of the rate of energy supply to these units. Both assumptions are direct consequences of the biochemical universality of living matter. However, the second assumption contradicts the central prediction of the WBE model that mass-specific metabolic rate q should decrease with body mass with a scaling exponent µ = ,1/4, thus making the model logically inconsistent. 2Examination of evidence interpreted by WBE and colleagues in favour of a universal µ = ,1/4 across 15 and more orders of magnitude range in body mass reveals that this value resulted from methodological errors in data assortment and analysis. 3Instead, the available evidence is shown to be consistent with the existence of a size-independent mean value of mass-specific metabolic rate common to most taxa. Plotted together, q -values of non-growing unicells, insects and mammals in the basal state yield µ , 0. Estimated field metabolic rates of bacteria and vertebrates are also size-independent. 4Standard mass-specific metabolic rates of most unicells, insects and mammals studied are confined between 1 and 10 W kg,1. Plant leaves respire at similar rates. This suggests the existence of a metabolic optimum for living matter. With growing body size and diminishing surface-to-volume ratio organisms have to change their physiology and perfect their distribution networks to keep their q in the vicinity of the optimum. [source]

Spatiotemporal characterization of interswarm period seismicity in the focal area Nový Kostel (West Bohemia/Vogtland) by a short-term microseismic study

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2009
Martin Häge
SUMMARY The West Bohemia/Vogtland region is one of the seismically most interesting areas in Europe because of its swarm-like occurrence of seismicity. The installation of the local West Bohemian seismological network (WEBNET) has made the recording of small magnitude seismicity (detection threshold ML,,0.5) possible. We investigated if microseismicity exists below the detection threshold of WEBNET. A microseismic field campaign was carried out in the focal area Nový Kostel. The measurement was performed with three small arrays lasting for 6 d in a seismically quiet, interswarm period. We were able to detect and locate 13 microearthquakes in the magnitude range ,1.5 ,ML,,0.1 and achieved a detection threshold about one magnitude lower than the local network. A relative location suggests that the recorded seismicity is rather related to a specific fault segment than randomly distributed. The determined fault zone is aligned NW,SW and confirms the viability of mapping active faults with short-term measurements. The results demonstrate that a linear extrapolation of the b -value, determined by the network bulletin, down to ML=,0.5 fits well with the amount of our recorded events. [source]

Exploring star formation using the filaments in the Sloan Digital Sky Survey Data Release Five

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2008
Biswajit Pandey
ABSTRACT We have quantified the average filamentarity of the galaxy distribution in seven nearly two-dimensional strips from the Sloan Digital Sky Survey Data Release Five (SDSS DR5) using a volume-limited sample in the absolute magnitude range ,21 ,Mr,,20. The average filamentarity of star-forming (SF) galaxies, which are predominantly blue, is found to be more than that of other galaxies which are predominantly red. This difference is possibly an outcome of the fact that blue galaxies have a more filamentary distribution. Comparing the SF galaxies with only the other blue galaxies, we find that the two show nearly equal filamentarity. Separately analyzing the galaxies with high star formation rates (SFR) and low SFR, we find that the latter has a more filamentary distribution. We interpret this in terms of two effects. (i) A correlation between the SFR and individual galaxy properties like luminosity with the high-SFR galaxies being more luminous. (ii) A relation between the SFR and environmental effects like the density with the high-SFR galaxies preferentially occurring in high-density regions. These two effects are possibly not independent and are operating simultaneously. We do not find any difference in the filamentarity of SF galaxies and active galactic nuclei. [source]

Searches for ultracompact dwarf galaxies in galaxy groups

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2007
E. A. Evstigneeva
ABSTRACT We present the results of a search for ultracompact dwarf galaxies (UCDs) in six different galaxy groups: Dorado, NGC 1400, 0681, 4038, 4697 and 5084. We searched in the apparent magnitude range 17.5 ,bJ, 20.5 (except NGC 5084: 19.2 ,bJ, 21.0). We found one definite plus two possible UCD candidates in the Dorado group and two possible UCD candidates in the NGC 1400 group. No UCDs were found in the other groups. We compared these results with predicted luminosities of UCDs in the groups according to the hypothesis that UCDs are globular clusters formed in galaxies. The theoretical predictions broadly agree with the observational results, but deeper surveys are needed to fully test the predictions. [source]

The WASP project in the era of robotic telescope networks

ASTRONOMISCHE NACHRICHTEN, Issue 8 2006
D. J. Christian
Abstract We present the current status of the WASP project, a pair of wide angle photometric telescopes, individually called Super-WASP. SuperWASP-I is located in La Palma, and SuperWASP-II at Sutherland in South Africa. SW-I began operations in April 2004. SW-II is expected to be operational in early 2006. Each SuperWASP instrument consists of up to 8 individual cameras using ultra-wide field lenses backed by high-quality passively cooled CCDs. Each camera covers 7.8 × 7.8 sq degrees of sky, for nearly 500 sq degrees of total sky coverage. One of the current aims of the WASP project is the search for extra-solar planet transits with a focus on brighter stars in the magnitude range ,8 to 13. Additionally, WASP will search for optical transients, track Near-Earth Objects, and study many types of variable stars and extragalactic objects. The collaboration has developed a custom-built reduction pipeline that achieves better than 1 percent photometric precision. We discuss future goals, which include: nightly on-mountain reductions that could be used to automatically drive alerts via a small robotic telescope network, and possible roles of the WASP telescopes as providers in such a network. Additional technical details of the telescopes, data reduction, and consortium members and institutions can be found on the web site at: http://www.superwasp.org/. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]