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  • 1
    Electronic Resource
    Electronic Resource
    Application of fiber-optic fluorescence measurements to on-line pH monitoring of a pseudomonad fermentation process (1991)
    s.l. : American Chemical Society
    Biotechnology progress 7 (1991), S. 564-569 
    Details
    ISSN: 1520-6033
    Source: ACS Legacy Archives
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bp00012a012
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  • 2
    Electronic Resource
    Electronic Resource
    Flow through arrays of cylinders: Lattice gas cellular automata simulations (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 6 (1994), S. 435-437 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A presentation is given of the results of two-dimensional lattice gas cellular automata (LGA) simulations for calculating the permeability for flow through periodic arrays of cylinders, where the cylinders have either a rhomboid or cruciform cross section. For the case of rhombi, the results are related via a semiempirical shape factor to analytical solutions for flow through arrays of circular cylinders. Finite size effects are studied by comparing simulation results with theory. This calibration of the LGA model then validates its use for the study of flow around cruciforms, for which there is no analytical solution. This has an important application in the mathematical modeling of flow through arrays of dendrites in the mushy region during the solidification of alloy steel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868341
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  • 3
    Electronic Resource
    Electronic Resource
    Analytical models of the effective permeability of sand-shale reservoirs (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 105 (1991), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: A study is made of the dependence of the effective permeability of sand-shale reservoirs on the geometry of the shale inclusions. Numerical simulations are described in which factors such as the orientation and the degree of anisotropy of the shales, their volume fraction and the permeability contrast ratio between the shale and the sandstone were varied. Two different reservoir models were used in the simulations: one in which the shales were in the form of random, overlapping spheroidal inclusions, and one in which the shales were generated by a geostatistical technique. The computed effective permeability data are compared with a variety of analytical models in an attempt to discover ‘rules of thumb’for the estimation of the effective permeability of sand-shale reservoirs for use in a range of practical situations. The main technical way in which this study advances on previous work is in its use of a computationally efficient, random walk algorithm for calculating the effective permeability, which has enabled larger volumes to be simulated and, hence, a thorough investigation of finite-size effects to be made. Another advantage of the work reported here is the general nature of the sand-shale geometries used in the numerical simulations and the extensive comparisons with analytical models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1991.tb06730.x
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  • 4
    Electronic Resource
    Electronic Resource
    Differential gene expression from the Escherichia coli atp operon mediated by segmental defferences in mRNA stability (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 5 (1991), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The atp operon of Escherichia coli directs synthesis rates of protein subunits that are well matched to the requirements of assembly of the membrane-bound H+-ATPase (α3β3γ1δ1σ1a1b2c10–15). Segmental differences in mRNA stability are shown to contribute to the differential control of atp gene expression. The first two genes of the operon, atpl and atpB, are rapidly inactivated at the mRNA level. The remaining seven genes are more stable. It has previously been established that the translational efficiencies of the atp genes vary greatly. Thus differential expression from this operon is achieved via post-transcriptional control exerted at two levels. Neither enhancement of translational efficiency nor insertion of repetitive extragenic palindromic (REP) sequences into the atplB intercistronic region stabilized atpl. We discuss the implications of these results in terms of the pathway of mRNA degradation and of the role of mRNA stability in the control of gene expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1991.tb02090.x
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  • 5
    Electronic Resource
    Electronic Resource
    Post-transcriptional control in the polycistronic operon environment: studies of the atp operon of Escherichia coli (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 4 (1990), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Post-transcriptional control mechanisms assume special significance in polycistronic operons. Differential gene expression in the atp operon of Escherichia coli is primarily attributable to translational control and, to a lesser extent, to control of mRNA stability. At the same time, the polycistronic environment influences, to varying degrees, the relative importance of the different types of post-transcriptional control. The present article briefly reviews more recent results obtained through studies of the atp operon. Investigations of the pathway and kinetics of mRNA decay have yielded new information about the role of degradative mechanisms in the overall scheme of control. Moreover, translational coupling has been shown to feature as a major form of interaction between the atp genes. The relevance of these and other data is discussed in the wider context of the post-transcriptional control mechanisms generally available to E. coli.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1990.tb00702.x
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  • 6
    Electronic Resource
    Electronic Resource
    Translational coupling varying in efficiency between different pairs of genes in the central region of the atp operon of Escherichia coli (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 5 (1991), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A series of afp::lacZ fusions has been constructed for use in a study of translational coupling in the central region of the Escherichia coli atp operon. Five genes, atpE, atpF, atpH, atp A and atpG, were shown to be translationally coupled to various degrees of tightness. A new lac promoter vector, compatible with the afp::lacZ fusion vectors, was used to express individual atp genes in the same hosts as the fusion genes. The H+-ATPase subunits thus synthesized exercised no significant trans-regulation on the expression of the atp::lacZ fusions, indicating that the coupling is primarily cis. The mechanism of this coupling was investigated using in vitro mutagenesis. At least in the case of the pair atpHA, coupling seems to involve facilitated binding of fresh ribosomes to the atpA translational initiation regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1991.tb00754.x
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  • 7
    Electronic Resource
    Electronic Resource
    AN ANALOG COMPUTER DEMONSTRATION OF DOUBLE-PEAKED INSTANTANEOUS UNIT HYDROGRAPHS (1972)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Water Resources Association 8 (1972), S. 0 
    Details
    ISSN: 1752-1688
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: The properties of an instantaneous unit hydrograph model consisting of two cascades of linear reservoirs in parallel were explored with the aid of an analog computer. By proper choice of the model parameters it is possible to produce two-peaked instantaneous unit hydrographs. The relative magnitudes and locations of the two peaks can be varied by changing the values of the parameters. An example of the use of the analog computer to select the parameters of the model giving the best fit to an observed runoff hydrograph is also included. The analog computer used in the study was the ASTRAC II developed at the University of Arizona.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1752-1688.1972.tb05257.x
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  • 8
    Electronic Resource
    Electronic Resource
    Significance of nanoplankton in the Chesapeake Bay estuary and problems associated with the measurement of nanoplankton productivity (1974)
    Springer
    Marine biology 24 (1974), S. 7-16 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Over a 2-year program of monthly cruises covering the entire Chesapeake Bay (USA), the phytoplankters which passed 35 μm mesh were responsible for 89.6% of the phytoplankton productivity. On a single summer cruise, the 〈35 μm phytoplankton fraction was responsible for 93.4% of the chlorophyll a and 100% of the primary productivity. The 〈10 μm fraction was responsible for 81.3% of the chlorophyll a and 94% of the productivity. The difference in biomass in the 〈35 μm and the 〈10 μm fractions was significant (P=0.025), but no significant difference in the productivity could be demonstrated. Laboratory experiments demonstrated that recently assimilated carbon can be lost with gravity screening. Considering both this and the effect of herbivorous zooplankters enclosed in productivity incubations, a prescreening rather than postscreening technique is recommended for studying nanoplankton productivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00402842
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  • 9
    Electronic Resource
    Electronic Resource
    Expression of a bacterial lysine decarboxylase gene and transport of the protein into chloroplasts of transgenic tobacco (1991)
    Springer
    Plant molecular biology 17 (1991), S. 475-486 
    Details
    ISSN: 1573-5028
    Keywords: Nicotiana tabacum ; plant transformation ; gene expression ; bacterial lysine decarboxylase ; protein transport ; chloroplasts ; cadaverine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A possible approach for altering alkaloid biosynthesis in plants is the expression of genes encoding key enzymes of a pathway such as lysine decarboxylase (ldc) in transgenic plants. Two strategies were followed here: one focused on expression of the gene in the cytoplasm, the other on subsequent targeting of the protein to the chloroplasts. Theldcgene fromHafnia alvei was therefore (a) placed under the control of the 1′ promoter of the bidirectional Tr promoter fromAgrobacterium tumefaciens Ti- plasmid, and (b) cloned behind therbcS promoter from potato fused to the coding region of therbcS transit peptide. Bothldc constructs, introduced intoNicotiana tabacum with the aid ofA. tumefaciens, were integrated into the plant genome and transcribed as shown by Southern and northern hybridization. However, LDC activity was only detectable in plants expressing mRNA under the control of therbcS promoter directing the LDC fusion protein into chloroplasts with the aid of the transit peptide domain. In plants expressing the processed bacterial enzyme cadaverine levels increased from nearly zero to 0.3–1% of dry mass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00040641
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  • 10
    Electronic Resource
    Electronic Resource
    Analytical solutions of 2D cresting models using the hodograph method (1994)
    Springer
    Transport in porous media 15 (1994), S. 251-269 
    Details
    ISSN: 1573-1634
    Keywords: Hodograph method ; 2D cresting models ; gas and water cresting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Three new applications of the hodograph method to the problem of gas and water cresting towards horizontal wells are presented: (1) A numerical technique, based on the hodograph method, is used to find the shape of the oil/water interface and values of critical heights for the problem of water cresting towards a horizontal well beneath an impermeable plane. (2) By correct implementation of the boundary conditions in the lateral edge drive model, a hodograph solution is found for which the water crest tends to a horizontal asymptote far from the well, rather than tending towards a parabolic curve as in previous approaches. The solution yields integral representations for the lengths of boundary segments and enables an explicit expression for the critical rate to be derived in terms of the distance to the constant potential boundary. (3) The problem of simultaneous gas and water cresting towards a horizontal well in a thin oil column reservoir is solved using the hodograph method, providing shapes of the free interfaces and an expression for the optimal placement of the well with respect to the interfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00613281
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