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  • Elsevier  (293)
  • Springer  (241)
  • Oxford University Press  (38)
  • Cambridge University Press  (24)
  • American Meteorological Society
  • 1995-1999  (197)
  • 1990-1994  (182)
  • 1980-1984  (129)
  • 1975-1979  (92)
  • 1945-1949  (2)
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  • 1
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Mechanically skinned fibre preparations from the extensor digitorum longus muscle of the rat were used to test whether a rise in myoplasmic [NH4 +] in the range 2–10 mm interferes with the mechanism of excitation-contraction coupling in fast-twitch mammalian muscle. Under our conditions (pH 7.10, Mg2+ 1 mm, temperature 23° C), [NH4 +] up to 10 mm had little effect on the Ca+-activated force and on the peak of the t-system depolarization-induced force response. However, the duration of the depolarization-induced force response was decreased significantly at [NH4 +] ≥2 mm. From these data we conclude that the intracellular accumulation of NH4 + is not likely to play a major role in fatigue. Nevertheless, the build up of NH4 + during fatigue, may have a significant inhibitory effect on the force output by decreasing the duration of the t-system depolarization-induced activation of the contractile apparatus.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The main objective of this study was to analyse glycogen in single muscle fibres, using a recently developed microfluorometric method which detects subpicomol amounts of NADPH, glucose and glycogen (as glucosyl units) (detection limit 0.16–0.17pmol in a 25nl sample) without fluorochrome amplification. The fibres were freshly dissected from the twitch region of the iliofibularis muscle of the cane toad (Bufo marinus), and were mechanically skinned under paraffin oil to gain access to the intracellular compartments. The results show that: (1) glycogen concentrations in toad skeletal muscle fibres range between 25.8 and 369mmol glucosyl units/litre fibre volume; (2) there is a large variation in glycogen content between individual fibres from the iliofibularis muscle of one animal; (3) there are seasonal differences in the glycogen content of toad single muscle fibres; (4) the total amount of glycogen in single muscle fibres of the toad does not decrease significantly when storing the tissue, under paraffin oil, at 20–25°C for up to 6h or at 4°C for up to 24h; and (5) 15–26% of fibre glycogen can be washed in an aqueous solution at pH 5–7, within 5min, while 74–85% of fibre glycogen remains associated with the washed skinned fibre, even after 40min exposure of the skinned fibre preparation to the aqueous environment. The retention of most glycogen in the fibre preparation after mechanical removal of the plasma membrane and extensive washing indicates that in toad skeletal muscle fibres the largest proportion of glycogen is tightly bound to intracellular structures. The results also show that the skinned muscle fibre preparation is well suited for microfluorometric glycogen determination, since low molecular weight non-glycogen contributors to the fluorescence signal can be removed from the myoplasmic space prior to the glycogen hydrolysis step.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 1998-06-01
    Print ISSN: 0003-2697
    Electronic ISSN: 1096-0309
    Topics: Biology , Chemistry and Pharmacology
    Published by Elsevier
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  • 4
    Electronic Resource
    Electronic Resource
    Cambridge : Cambridge University Press
    Journal of American studies 9 (1975), S. 189-197 
    ISSN: 0021-8758
    Source: Cambridge Journals Digital Archives
    Topics: English, American Studies , History , Political Science , Sociology , Economics
    Notes: While the question of geographic mobility has long been a mainstay of American historical writing and American myth-making – as evidenced by Turner and his disciples and the general obsession widi the frontier – until recently most historians have done little systematic investigation into it. Nor, indeed, have they been aware either of the enormous degree of movement within the country, or of the complex issues involved in determining why people have moved as they have. However, with the rise of what generally is termed the ‘ new urban ’ or ‘ new social ’ history, historians have begun to view migration as a question central to their analysis. Social scientists recognized the importance of migratory behaviour for many years and have employed sophisticated analytical techniques in their efforts to explain migration patterns, but recently historians approached the problem from another direction.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Cambridge : Cambridge University Press
    Urban history 24 (1997), S. 365-366 
    ISSN: 0963-9268
    Source: Cambridge Journals Digital Archives
    Topics: Architecture, Civil Engineering, Surveying , History , Sociology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of mathematical biology 40 (1978), S. 211-221 
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Non-steady-state equations for kidney models are stated. General conservation relations for these equations are derived. Transient equations for the central core model of the renal medulla are developed. Solution of the equations by Laplace transform methods for time invariant volume flows is discussed. The general theory of solving models with time dependent flows by finite difference methods is developed.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of mathematical biology 40 (1978), S. 273-300 
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Transient solutions are developed for the buildup of a concentration gradient in the single loop solute cycling model of the renal medulla. The “pump” from ascending limb to descending limb is considered in both unsaturated and completely saturated modes of operation. Both analytic solutions and semianalytic solutions obtained from inverting Laplace transforms are considered. The classic representation of concentration buildup by the multiplication process is compared with calculated profiles. The “single effect” is found to vary both in time and space.
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  • 8
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Substitution of measured permeabilities into mathematical models of the concentrating mechanism of the renal inner medulla yields less than the known urine osmolalities. To gain a better understanding of the mechanism we analyse a model in which a force of unspecified origin [expressed as fraction, ɛ, of entering descending thin limb (DTL) concentration] drives fluid from DTL to interstitial vascular space (CORE), thus concentrating the solution in DTL. When flow in the DTL reverses at the hairpin bend of the loop of Henle, the high solute permeability of ascending thin limb (ATL) permits solute to diffuse into the CORE thus permitting ɛ to be multiplied many-fold. Behavior of the model is described by two non-linear differential equations. In the limit for infinite salt permeability of ATL the two equations reduce to a single equation that is formally identical with that for the Hargitay and Kuhn multiplier, which assumes fluid transport directly from DTL to ATL (Z. Electrochem. Angew. Phys. Chem. 55, 539, 1951). Solutions of the equations describing the model with parameters taken from perfused thin limbs show that urine osmolalities of the order of 5000 mosm L−1 can be generated by forces of the order of 20 mosm L−1. It seems probable that mammals including desert rodents use some variant of this basic mechanism for inner medullary concentration.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1435-604X
    Keywords: Keywords: Adenocarcinoma; Aminolaevulinic acid; Barrett's oesophagus; Dysplasia; Photodynamic therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract . Photodynamic therapy (PDT) may have a role in the prevention of oesophageal cancer. Ten patients with Barrett's oesophagus, three with low-grade dysplasia (LGD), four with high-grade dysplasia (HGD), one with carcinoma in situ and two with invasive carcinoma, were treated with PDT. All received 30 mg/kg aminolaevulinic acid (ALA) followed 4 h later by laser endoscopy. Half were treated with red light (630 nm; 100 mW/cm2 for 1000 s) and half with green light (514 nm; 100 mW/cm2 for 500 s). Columnar epithelial regression was seen in all patients with dysplasia (mean area decrease 44%; range 10–100%), with apparent elimination of dysplasia in all cases. In patients with in situ or invasive carcinoma, no response was seen. ALA-induced PDT, using either red or green light, produces effective ablation of dysplastic Barrett's oesophagus, hence may have a role in the prevention of oesophageal carcinoma, but has little effect on in situ or invasive adenocarcinoma.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Optical and quantum electronics 12 (1980), S. 143-158 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract In this paper, the radiation losses caused by film thickness and refractive index discontinuities in asymmetric slab waveguides are examined theoretically. A technique developed by Mahmoud and Beal for dealing with the continuous part of the radiation spectrum is used. Several numerical examples which show the radiation loss for various waveguide configurations are presented and discussed and, where appropriate, comparisons with other related work made. In the case of asymmetric thickness steps, the radiation losses are found to be appreciably higher than those computed for symmetric guides. The radiation losses for guides having the same thickness were found to decrease as the guide thickness increased. Once the TE1 mode become guided, the losses decreased rapidly. However, if the two guides had different thickness then it was found that the losses exhibited a minimum.
    Type of Medium: Electronic Resource
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