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Digitale Medien

Exact solutions of an algebraically extended Kaluza–Klein theory (1985)

Mann, R. B.

College Park, Md. : American Institute of Physics (AIP)

Journal of Mathematical Physics 26 (1985), S. 2308-2316

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ISSN: 1089-7658

Quelle: AIP Digital Archive

Thema: Mathematik , Physik

Notizen: The four-dimensional field equations in an algebraically extended Kaluza–Klein theory are solved in the static spherically symmetric case. Eight distinct classes of solutions are found, some of which are free of singularities in both the metric and the electromagnetic field.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.526814

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Digitale Medien

On the accuracy of age-determination using scales from rudd, Scardinius erythrophthalmus (L.), of known age (1985)

Mann, R. H. K. ; Steinmetz, B.

Oxford, UK : Blackwell Publishing Ltd

Journal of fish biology 26 (1985), S. 0

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ISSN: 1095-8649

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Biologie

Notizen: Six scientists from five European countries each examined 29 sets of scales from rudd of known age. The material contained 174 scales from both fast and slow growing fish and, with the exception of one participant, the scientists missed the first annulus when it was formed close to the scale centre. Sixty-eight scales were misread in this way, but only 12 were incorrectly aged because of confusion between true and false annuli. Comparisons of back-calculated lengths with observed lengths at each age were used to identify which false annuli had been incorrectly identified as true annuli, and vice-versa. The results confirmed the necessity of having information from other sources, e.g. seasonal length-frequency distributions of 0-group fish, to support the subjective interpretation of the scales.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.1095-8649.1985.tb04302.x

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Digitale Medien

Environmentally-induced fluctuations in year-class strength and their implications for management (1985)

Mills, C. A. ; Mann, R. H. K.

Oxford, UK : Blackwell Publishing Ltd

Journal of fish biology 27 (1985), S. 0

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ISSN: 1095-8649

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Biologie

Notizen: Data for river populations of common freshwater species including dace, chub, roach, gudgeon and pike are examined to assess the magnitude of natural density-independent fluctuations in the strength of year-classes. Both in the cyprinid populations and in those of some salmonids, only occasional years give rise to large cohorts of adult fish. Correlations with temperature indicate that for the cyprinid populations these are often years when temperatures are high. In the River Frome, Dorset there is a significant relationship between the growth of O-group dace and subsequent year-class strength. Faster-growing larvae may be better able to avoid predation. Both the habitat and feeding requirements of these young fish are different from those of the adults. A practical approach to improving recruitment in a population of a given species would be to first characterize, and then increase, the availability of suitable habitats and food organisms for the larval stages.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.1095-8649.1985.tb03243.x

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A pike management strategy for a trout fishery (1985)

Mann, R. H. K.

Oxford, UK : Blackwell Publishing Ltd

Journal of fish biology 27 (1985), S. 0

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ISSN: 1095-8649

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Biologie

Notizen: The efficiency of pike removal from a chalkstream trout fishery, by an angling society using electrofishing, was estimated over five successive autumns using mark-recapture methods. It averaged c. 50% for pike aged 1+ years or more. Numbers of 3+ and older pike decreased from 3.7 ha-1 (1980) to 1.4 ha-1 (1984), but there was no corresponding reduction in recruitment success. Both pike immigration and an inverse relationship between natural and fishing mortality could have reduced the effect of the pike culls. The mean weight of 0+ pike increased from 19.4 g to 48.2 g over the 5 years, but there was no change in the growth rates of older pike. Only the larger pike were able to eat the larger trout stocked, and the reduction in numbers of 3 + and older pike appears to have reduced the predation pressure on the trout population. Angling effort increased more than three-fold over the 5 years studied and rod-catches more than doubled, but catch-per-unit-effort was extremely variable between years. The increased rod catch occurred despite the decrease in numbers of large (〉 33 cm) trout stocked in the spring and early summer. Compared with pre-cull years, the angling society saved about ş850 (present day prices) by stocking fewer trout.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.1095-8649.1985.tb03244.x

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Experimental temperature rise in human hip joint in vitro in simulated walking (1985)

Tepic, S. ; Macirowski, T. ; Mann, R. W.

Hoboken, NJ [u.a.] : Wiley-Blackwell

Journal of Orthopaedic Research 3 (1985), S. 516-520

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ISSN: 0736-0266

Schlagwort(e): Synovial joint mechanics ; Simulated walking ; Friction ; Temperature rise ; Chondrocyte response ; Life and Medical Sciences

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Medizin

Notizen: Although reported frictional coefficients in synovial joints are very low, a computer model of the human hip joint in simulated walking predicted a temperature rise of several degrees Celsius. To confirm this prediction, physical experiments were conducted in vitro on intact human hip joints dynamically loaded and articulated as in walking. Thermisters were placed in subchondral bone in both the acetabulum and femoral head, just below the cartilage layers. The surrounding saline bath was maintained at 37°C. Measured temperatures as high as 2.5°C above the 37°C were recorded in the subchondral bone. Loading that simulated the stance/swing phases of gait but without articulation produced no significant increase in temperature; thus fluid flow perse is not significantly energy dissipative; the prime source is friction at the articulating surfaces.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/jor.1100030416

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