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  • 1
    Electronic Resource
    Electronic Resource
    The room temperature reaction of carbon monoxide and oxygen with the cytochrome bd quinol oxidase from Escherichia coli (1994)
    s.l. : American Chemical Society
    Biochemistry 33 (1994), S. 15110-15115 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00254a021
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  • 2
    Electronic Resource
    Electronic Resource
    Biodegradable after use but not in use (1994)
    Bradford : Emerald
    Industrial lubrication & tribology 46 (1994), S. 7-9 
    Details
    ISSN: 0036-8792
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Discusses the paradox of the desire for petroleum products to resist degradation in use and yet be readily biodegradable as waste products. Offers four suggestions on how to reduce microbial susceptibility in use.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/00368799410781098
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  • 3
    Electronic Resource
    Electronic Resource
    Does Melanin Affect the Low LET Radiation Response of Cloudman S91 Mouse Melanoma Cell Lines? (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Periodontology 2000 4 (1991), S. 0 
    Details
    ISSN: 1600-0757
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Melanin contains melanin-free radicals and can both absorb and produce additional free radicals and active oxygen species on exposure to various stimuli. Yet its role in the radiation responses of malignant melanoma has been little studied. In this report, three subclones of Cloudman S91 mouse melanoma clone PC1A varying in constitutive melanin content were compared with respect to killing by gamma irradiation. Radiation responses correlated with melanin content. The least melanotic line, S91/amel, was most sensitive and the most melanotic line, S91/I3, was most resistant. Curve fitting using the linear-quadratic model suggests that S91/amel is killed only by single event inactivations; S91/I3, only by double event inactivations; and S91/M1B, with intermediate melanin and radiation response, by both types of inactivations. Split dose experiments confirmed a lack of immediate split dose recovery in S91/amel and its existence in S91/I3. Potentially lethal damage and its repair could be demonstrated in both S91/amel and S91/I3. Double strand break (DSB) induction was evaluated as a function of gamma ray dose in DNA of S91/I3 and S91/amel, as well as in EMT6, a mouse mammary cancer line that lacks tyrosinase and melanin. The rates of induction were proportional to cellular melanization, i.e., the rate of DSB induction was greatest in S91/I3, least in EMT6. Levels of thioredoxin reductase (TR), glutathione reductase (GR), superoxide dismutase (SOD), and catalase (CAT) were determined in S91/amel and S91/I3. TR was the same in both cell lines, while the other three enzymes were 3- to 4-fold lower in S91/amel. The results suggest that 1) melanin can act as a radiosensitizer of DNA damage and, 2) the presence of moderate constitutive levels of melanin in cells may effect radiation resistance by indirect means, possibly by causing cells to maintain high levels of antioxidant defenses and/or DNA repair systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-0749.1991.tb00319.x
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  • 4
    Electronic Resource
    Electronic Resource
    A mechanism for isotonic fluid flow through the tight junctions of Necturus gallbladder epithelium (1993)
    Springer
    The journal of membrane biology 136 (1993), S. 253-262 
    Details
    ISSN: 1432-1424
    Keywords: Pore sizes ; Epithelial junctions ; Necturus gallbladder ; Fluid transport ; Convective channels ; Reflexion coefficient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract During isotonic fluid flow, Necturus gallbladder epithelium mediates net fluxes of paracellular probes by a convective process. We show here that the paracellular system is modeled by permeation through three populations of channels: (i) convective parallel-sided ones of width 7.7 nm (ii) small diffusive ones of radius ∼0.6 nm, and (ii) large diffusive ones of radius exceeding 50 nm. The reflexion coefficient of the convective channels is very low and the calculated osmotic flow rate is close to zero when compared with the observed fluid absorptive rate of 2 x 10−6 cm/sec. Analysis reveals that the convective channels behave as though closed to back-diffusion of probes; if this is due to solvent drag then very high fluid velocities are required, acting through minute areas. There are no transjunctional gradients that could drive the flow, and so the fluid must be propelled through the channel by components of the junction. We propose a mechanism based upon an active junctional peristalsis which allows discrimination on the basis of molecular size, in which the channels are always occluded at some point and so back-diffusion cannot occur. There is no local gradient of salt distal to the junctions and therefore the osmotic permeability of the membranes is irrelevant. High fluid velocities are not required, and the flow can occur over a substantial fraction of the junction. The mechanism must involve motile and contractile elements associated with the junction for which there is already considerable evidence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233664
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  • 5
    facet.materialart.
    Unknown
    E.P. Thompson's Blake (1994)
    Manchester, etc. : Periodicals Archive Online (PAO)
    Literature and history. ser.3:3:1 (1994:Spring) 83 
    Details
    ISSN: 0306-1973
    Topics: Linguistics and Literary Studies , History
    Notes: Review Articles
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:r575-1994-003-01-000005
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  • 6
    Electronic Resource
    Electronic Resource
    On the derivation of first integrals for similarity solutions (1991)
    Springer
    Journal of engineering mathematics 25 (1991), S. 287-299 
    Details
    ISSN: 1573-2703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Technology
    Notes: Abstract In two recent papers the authors have obtained a number of first integrals for similarity solutions of nonlinear diffusion and of general high-order nonlinear evolution equation. Such integrals exist only for special parameter values and are obtained via integration of the ordinary differential equation, which results when the functional form of the solution is substituted into the governing partial differential equation. In this paper we show that these special parameter values also occur in a natural way when we utilize the first order partial differential equation instead of the explicit functional form and we ask under what conditions can a first integral with respect to either of the independent variables x or t be deduced. This simple procedure generates all previous results and presents the idea of similarity solutions in an entirely new light. That is, the significant features of similarity solutions for partial differential equations are not necessarily the explicit functional form and subsequent reduction to an ordinary differential equation but rather that the solutions sort are common to two partial differential equations. The process is illustrated with reference to an extensive number of examples including nonlinear diffusion, general diffusion equations containing a number of parameters and high-order nonlinear evolution equations. In addition a new exact solution for nonlinear diffusion is obtained which is illustrated graphically.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00044335
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  • 7
    Electronic Resource
    Electronic Resource
    Similarity solutions for nonlinear diffusion — further exact solutions (1990)
    Springer
    Journal of engineering mathematics 24 (1990), S. 109-124 
    Details
    ISSN: 1573-2703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Technology
    Notes: Abstract Although the nonlinear diffusion equation has been extensively studied and there exists substantial literature in many diverse areas of science and technology, the number of exact concentration profiles is nevertheless limited. In a recent article in this journal (Hill [1]) a brief review of known exact results is given, as well as an elementary integration procedure which appears to be a general device for obtaining integrals associated with similarity solutions. This paper extends the results given in [1] and for particular power law diffusivitiesc m (such asm = −/12, −1, −/32 and −2) presents a number of new exact solutions obtained by fully integrating the ordinary differential equations derived in [1]. In addition new results are found for a general nonlinear diffusion equation which includes one-dimensional diffusion with an inhomogenouus and nonlinear diffusivityc mxmas well as symmetric nonlinear diffusion in cylinders and spheres. Moreover by a separate and ad-hoc procedure a new solution is obtained of the travelling wave type but with a variable wave speed. Some of the new exact solutions obtained for one-dimensional nonlinear diffusion with power law diffusivitiesc mare illustrated graphically.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00129869
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  • 8
    Electronic Resource
    Electronic Resource
    Utilization of nonlinear diffusion solutions forn-diffusion and power-law materials (1992)
    Springer
    Acta mechanica 91 (1992), S. 193-208 
    Details
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The equation ofn-diffusion, as originally formulated by J. R. Philip for various problems involving unsteady turbulent flows, applies directly to the one-dimensional flow of a non-Newtonian power-law fluid as well as indirectly to the laminar boundary layer flow of such fluids over a flat plate. The purpose of this note is to utilize a simple relation between one-dimensionaln-diffusion and nonlinear diffusion with power-law diffusivity such that ifp(x, t) denotes ann-diffusion pressure thenc(x, t)=|ϖp/ϖx| satisfies the nonlinear diffusion equation with power law diffusivity. This means in particular that the large number of solutions presently known for nonlinear diffusion can be utilized in the context ofn-diffusion. Known solutions ofn-diffusion are obtained via this procedure as well as newn-diffusion solutions, including the source solution and a solution of the problem of fluid withdrawal at a constant flow rate for a non-Newtonian fluid in a porous medium of infinite extent. Solutions arising from other exact nonlinear diffusion profiles are also investigated as well as the limiting case ofn-diffusion forn tending to infinity and the results are displayed graphically.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01194109
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  • 9
    Electronic Resource
    Electronic Resource
    Clinical birthweight standards for a total population in the 1980s (1993)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 100 (1993), S. 0 
    Details
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Objective To derive clinical standards for singleton birthweight in a population based on area of residence.Design Analysis of variables recorded in Aberdeen Maternity and Neonatal Databank, calculating for each birth a standardised birthweight score, taking account of determining factors.Subjects All singleton live births of 32 to 42 weeks gestation to Aberdeen City District residents from 1979 to 1983.Results Basic standards of birthweight are presented correcting for gestational age, sex of the baby and parity of the mother. Birthweight is not normally distributed and empirical data are presented rather than smoothed curves. Adjustment for maternal height is straightforward but adjustment for maternal weight must take account of the gestation at which the woman was weighed. A method of calculating the appropriate correction for height and weight is described in detail.Conclusion Birthweight is not normally distributed at each week of gestation. Standardisation for parity, gestation and sex of the baby is essential, but adjustment for maternal size is complex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-0528.1993.tb15268.x
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  • 10
    Electronic Resource
    Electronic Resource
    Excitatory Amino Acid-Induced Phosphoinositide Turnover in Guinea Pig Cerebral Cortical Slices: Selective Enhancement by Spermine of the Response to DL-1-Aminocyclopentane- trans-1, 3-Dicarboxylate (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 59 (1992), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: In the presence of 1 mM spermine, accumulations of 3H labelled inositol phosphates elicited by quisqualate (100 μM) and 1 -aminocyclopentane-trans- 1, 3-dicarboxylate (t-ACPD, 300 μM) were significantly enhanced by 21 and 26%, respectively, without a significant alteration in the accumulation elicited by l-glutamate (10 mM) or DL-α-amino-3-hydroxy-5-methyl-4-isoxalone propionate (10 μM). Analysis of concentration-response data indicated that the presence of spermine led to an increase in the maximal response to t-ACPD without altering the EC50 value. The stimulatory effect of spermine on the accumulation of t-ACPD-elicited 3H-inositol phosphates was not reversed by ifenprodil or diethylenetriamine (putative polyamine site antagonists), by agents that activate or inhibit protein kinase C, or by calcium channel blockade, but was abolished in the presence of elevated extracellular calcium ion concentration. We conclude that spermine enhances the phosphoinositide turnover in guinea pig cerebral cortical slices elicited by the “metabotropic” excitatory amino acid receptor. The site through which the action of spermine is mediated remains to be defined, but it is apparently distinct from that suggested to modulate N-methyl-D-aspartate receptor activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1992.tb09413.x
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