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  • 1
    Electronic Resource
    Electronic Resource
    The Role of Carbonic Anhydrase in Photosynthesis (1994)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Plant Physiology and Plant Molecular Biology 45 (1994), S. 369-392 
    Details
    ISSN: 1040-2519
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.pp.45.060194.002101
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  • 2
    Electronic Resource
    Electronic Resource
    High light enhances the expression of low-CO2-inducible transcripts involved in the CO2-concentrating mechanism in Synechocystis sp. PCC6803 (2004)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 27 (2004), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The relative abundances of key gene transcripts encoding proteins involved in inducible inorganic carbon (Ci) transport in the cyanobacterium Synechocystis PCC6803 were quantified by real-time reverse-transcriptase-polymerase chain reaction under conditions of varying Ci and light levels. Significant increases in CO2-concentrating mechanism (CCM)-related transcript abundance were observed only in cells aerated with CO2-free air for 30 min in the light, but not in the dark, relative to illuminated cells grown at high CO2 levels (high-Ci cells). Cells were incubated under precisely defined conditions in a cuvette attached to a mass spectrometer to allow for the measurement of photosynthetic gas exchange rates, [Ci] and [O2], in combination with quantitative analysis of transcripts. Under conditions of increasing irradiance and low [Ci], or under conditions of decreasing [Ci] at constant irradiance, the abundances of cmpA (encoding part of the BCT1 HCO3– transporter), ndhF3 (encoding subunit of high-affinity CO2 uptake system) and sbtA (encoding Na+-dependent HCO3– transporter) transcripts tended to increase, relative to illuminated cells grown at high-CO2. The cmpA transcript appeared to be less responsive to decreasing [Ci] than either ndhF3 or sbtA. The induction of cmpA and ndhF3 transcripts was completely inhibited by 10 µm 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) compared to untreated control cells. This inhibitor had no effect on sbtA expression. In the presence of 2,6-dichlorobenzoquinone (DCBQ), the expression of the cmpA transcript tracked the apparent rate of O2 evolution from photosystem II closely as the irradiance was increased, reaching maximum levels of expression approximately 16-fold higher than control cells. Under the same conditions, the ndhF3 transcript increased by two- to three-fold, whereas the sbtA transcript did not respond to this treatment. The regulation of CCM induction in this strain is discussed in relation to current hypotheses on the sensing of Ci limitation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.2004.01175.x
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  • 3
    Electronic Resource
    Electronic Resource
    Carbonic anhydrase and C4 photosynthesis: a transgenic analysis (2004)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 27 (2004), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Carbonic anhydrase (CA, EC 4.2.1.1) catalyses the first reaction in the C4 photosynthetic pathway, the conversion of atmospheric CO2 to bicarbonate in the mesophyll cytosol. To examine the importance of the enzyme to the functioning of the C4 photosynthetic pathway, Flaveria bidentis (L.) Kuntze, a C4 dicot, was genetically transformed with an antisense construct in which the cDNA encoding a putative cytosolic CA (CA3) was placed under the control of a constitutive promoter. Some of the primary transformants had impaired CO2 assimilation rates and required high CO2 for growth. The T1 progeny of four primary transformants were used to examine the quantitative relationship between leaf CA activity and CO2 assimilation rate. CA activity was determined in leaf extracts with a mass spectrometric technique that measured the rate of 18O exchange from doubly labelled 13C18O2. Steady-state CO2 assimilation rates were unaffected by a decrease in CA activity until CA activity was less than 20% of wild type when they decreased steeply. Transformants with less than 10% of wild-type CA activity had very low CO2 assimilation rates and grew poorly at ambient CO2 partial pressure. Reduction in CA activity also increased the CO2 partial pressure required to saturate CO2 assimilation rates. The present data show that CA activity is essential for the functioning of the C4 photosynthetic pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.2003.01157.x
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  • 4
    Electronic Resource
    Electronic Resource
    Science policy in Australia (1988)
    [s.l.] : Nature Publishing Group
    Nature 336 (1988), S. 10-10 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIRá€"The Australian federal government has placed great emphasis on science and technology to underpin Australia's future economic performance. A recent policy statement on higher education describes the government's agenda for sweeping changes designed to align academic and ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/336010a0
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  • 5
    Electronic Resource
    Electronic Resource
    Thermodynamic properties of CaCO3 calcite and aragonite: A quasi-harmonic calculation (1993)
    Springer
    Physics and chemistry of minerals 19 (1993), S. 472-479 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract A quasi-harmonic model has been used to simulate the thermodynamic behaviour of the CaCO3 polymorphs, by equilibrating their crystal structures as a function of temperature so as to balance the sum of inner static and thermal pressures against the applied external pressure. The vibrational frequencies and elastic properties needed have been computed using interatomic potentials based on two-body Born-type functions, with O-C-O angular terms to account for covalency inside the CO3 molecular ion. A good agreement with experimental data is generally shown by simulated heat capacity and entropy, while the thermal expansion coefficient seems to be more difficult to reproduce. The results obtained for aragonite are less satisfactory than those of calcite, but they are improved by using a potential specifically optimized on properties of that phase itself.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00203187
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  • 6
    Electronic Resource
    Electronic Resource
    Interatomic potentials for CaCO3 polymorphs (calcite and aragonite), fitted to elastic and vibrational data (1992)
    Springer
    Physics and chemistry of minerals 19 (1992), S. 80-87 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Calcite and aragonite have been modeled using rigid-ion, two-body Born-type potentials, supplemented by O-C-O angular terms inside the CO3 groups. A shell model has also been developed for calcite. Atomic charges, repulsive parameters and force constants have been optimized to reproduce the equilibrium crystal structures, the elastic constants and the Raman and infrared vibrational frequencies. The rigid-ion potential RIM (atomic charges:z O= -0.995e,z C = 0.985e,z Ca = 2.0e) fitted to calcite properties is able to account for those of aragonite as well. Experimental unit-cell edges, elastic constants, internal and lattice frequencies are reproduced with average relative errors of 2.1, 5.5, 2.4, 15.1% for calcite and of 0.2, 19.4, 2.5, 11.8% for aragonite, respectively. The RIM potential is suitable for thermodynamic and phase diagram simulations in the CaCO3 system, and is discussed and compared to other potentials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00198605
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  • 7
    Electronic Resource
    Electronic Resource
    The energetics of interaction between oxygen vacancies in sillimanite: A model for the mullite structure (1992)
    Springer
    Physics and chemistry of minerals 19 (1992), S. 196-202 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract A microscopic model is introduced to discuss the modulated structure of mullite. The oxygen vacancies of this aluminosilicate are known to play a central role. In particular, a single vacancy strongly orders its surrounding Al/Si tetrahedral sites. It is shown in this work that if two oxygen vacancies approach too closely to one another, their Al/Si “dressing” overlap. This situation results in repulsive interaction. The field of interaction between the vacancies is estimated with the use of an atomistic computer simulation. We use a Bragg-Williams type of theory to dicuss the ordering pattern of the vacancies. Due to “frustration” between the two dominant repulsive interactions, our model predicts a modulated phase transition in agreement with observation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00202108
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  • 8
    Electronic Resource
    Electronic Resource
    Periodic ab initio Hartree-Fock study of trigonal and orthorhombic phases of boric oxides (1997)
    Springer
    Physics and chemistry of minerals 24 (1997), S. 423-431 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract  The structure and electronic properties of trigonal and orthorhombic boric oxide (B2O3) are studied using periodic ab initio Hartree-Fock method. The optimised structural parameters for two B2O3 polymorphs are in good agreement with experimental data. The analyses of their electronic structures provide insights into the chemical nature of the B–O bond and the way in which it changes with the coordination number around boron and oxygen. Our quantum-chemical study suggests that the orthorhombic form is more ionic than the trigonal form and that the coordination number of boron around oxygen plays a more dominant role than that of oxygen around boron in B2O3 crystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690050056
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  • 9
    Electronic Resource
    Electronic Resource
    Modelling the effect of water on the surface structure and stability of forsterite (2000)
    Springer
    Physics and chemistry of minerals 27 (2000), S. 332-341 
    Details
    ISSN: 1432-2021
    Keywords: Key words Forsterite ; Atomistic simulation ; Adsorption of water ; Surface reactivity ; Morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract  We describe the application of atomistic simulation techniques to investigate the effect of associative and dissociative adsorption of water on the structures and stabilities of the low-index surfaces of forsterite. All surfaces are amenable to associative adsorption of water, while dissociative adsorption is energetically favourable on all but the non-dipolar {1 0 0} surface. Often, otherwise unstable (dipolar) surfaces are stabilised to a large extent by hydration, e.g. the dipolar {0 1 0} surface. However, on thermodynamic grounds we do not expect associatively adsorbed water to dissociate on all surfaces, as the energies released for dissociative adsorption of water on the non-dipolar {0 1 0} and {1 0 0} surfaces are less than those released for associative adsorption. As such, there is no energetic incentive for the associatively adsorbed water molecules to dissociate. The stabilities of the two terminations of the {0 1 0} surface, the main cleavage plane of forsterite, are reversed when hydroxylated, indicating that some dissolution of the magnesium ions may occur upon hydration, which is shown to be an exothermic process for both surface terminations. The equilibrium morphology was calculated as a way of assessing the change in surface energies. The experimental morphology of forsterite is adequately reproduced, suggesting that the relative stabilities of the surfaces, both unhydrated and hydroxylated, are calculated correctly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690050262
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  • 10
    Electronic Resource
    Electronic Resource
    A mechanism for pyroxene-pyroxenoid and pyroxenoid-pyroxenoid transformations (1984)
    Springer
    Physics and chemistry of minerals 10 (1984), S. 236-243 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract A mechanism for the solid state replacement of clinopyroxene by pyroxenoids has been derived from consideration of the crystal structures. The mechanism involves the propagation of partial dislocations, with Burgers vectors of 1/4 $$[2\bar 3\bar 1]$$ , through the clinopyroxene matrix to generate a resultant shear; the passage of one dislocation gives rise to a single chain-repeat unit of wollastonite in each silicate chain. Pyroxenoids may thus be formed from clinopyroxene by the periodic introduction of these dislocations on parallel slip-planes, and pyroxenoid to pyroxenoid inversions may proceed by the introduction and removal of such shears by the propagation of the correct combination of partial dislocations. The Burgers vectors for these dislocations in each of the pyroxenoid mineral structures has been calculated. A two step mechanism is proposed for clinopyroxene to bustamite, and pyroxenoid to bustamite inversions, which utilises the same shear as above which generates a wollastonite structure. The second step is a shear of 1/2[001] on the plane $$(1\bar 10)$$ of this wollastonite intermediate, to give a bustamite structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00309316
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