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  • 1
    Electronic Resource
    Electronic Resource
    Availability of copper from phytoplankton and water for the bivalveMacoma balthica. II. Uptake and elimination from64Cu-labelled diatoms and water (1994)
    Springer
    Marine biology 118 (1994), S. 129-135 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The amount of copper taken up via algae and water byMacoma balthica from the Oosterschelde sea arm, S.W. Netherlands, was established using the radioisotope64Cu. As far as we know, this isotope has never been used before in marine flod chain studies. As a model food source the marine diatomPhaeodactylum tricornutum was allowed to accumulate64Cu for 1 d. These labelled algae were fed to the clams in the presence of the complexing agent EDTA (0.27mM). EDTA was added to prevent uptake of dissolved64Cu that could be leaking from the labelled diatoms. In control experiments, unlabelled diatoms were fed toM. balthica in the presence of dissolved64Cu (with and without EDTA) in order to assure a similar filtration activity. In repeated experiments with varying particulate/dissolved copper ratios, uptake through food always turned out to be at least as efficient as uptake from the water. It was concluded that Cu, associated with food, is well available for uptake byM. balthica.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00699227
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  • 2
    Electronic Resource
    Electronic Resource
    Availability of copper from phytoplankton and water for the bivalveMacoma balthica. I. Separation of uptake pathways using the radiotracer64Cu (1994)
    Springer
    Marine biology 118 (1994), S. 123-127 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To study the role of food in Cu accumulation by bivalves, algae spiked with Cu can be used. With spiked algae, however, redistribution of Cu between the disolved solved and the particulate phase hampers the assessment of the contribution of food. This occurred in efforts to label algae with the radiotracer64Cu. A method was designed to overcome this problem of redistribution. By adding excess EDTA to seawater, the biological availability of dissolved Cu was minimized. The effectiveness of complexation by EDTA was controlled through adsorption onMacoma balthica shells and uptake inM. balthica tissue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00699226
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  • 3
    Electronic Resource
    Electronic Resource
    The joint probability distribution of Eh, Eh+k and cos 2π(h/2+k).U – where U is a single Patterson vector – and related conditional averages: space group P\overline{1} (1975)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 31 (1975), S. 731-737 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: In order to establish a generalized form of an earlier derived algebraic relation between a structure factor, triple products and a single Patterson vector U, the joint probability distribution P(X0, X1, M) of Ek, Eh + k and cos 2π(h/2 + k). U with h fixed, is derived for space group P{\bar 1}. From this distribution the desired generalized equations are obtained. The sign probability formula for triple products is adapted to the case that cos 2π(h/2 + k). U is known. A numerical check on the expression for the conditional average (cos 2πh/2 + k). U||Ek| 〉 t, |Eh + k 〉 t )k, showed that for an artificial structure the set of signs of the structure factors obtained from this expression was better than that calculated from heavy-atom positions related by U.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739475001581
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  • 4
    Electronic Resource
    Electronic Resource
    Direct phase determination of triple products from Bijvoet inequalities (1977)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 33 (1977), S. 382-385 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The classical method of phase determination from Bijvoet inequalities is applied to the phase {\bar \varphi}hk = ½(φhk -- \varphi_{\bar {\bf hk}}) of the triple product τhk ≡ FhFkF_{\bar {\bf h + k}}. The phase-determining formula is then (in the case of a centrosymmetric configuration of anomalous scatterers): sin {\bar \varphi}hk = {{|\tau_{hk}|^{2} - |\tau_{{\bar \bf hk}}|^{2}}\over{4\tau''_{\bf hk}|\tau^{0}_{\bf hk}}} in which τ”hk is the contribution from the imaginary part of the complex double Patterson function to τhk, and | τ0hk2 =½(| τhk|2 + | τ_{\bar hk}|2) - | τ”hk|2. It is shown that τ”hk contains an important term, i.e. the contribution from the origin peak of the double Patterson function, which is independent of the positions of the anomalous scatterers. A test calculation on a structure in P1, containing two Br ions, shows that, in fact, the phases of the triple products can be determined without introducing any a priori knowledge about the positions of the anomalous scatterers, provided an appropriate scaling procedure is applied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739477001028
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  • 5
    Electronic Resource
    Electronic Resource
    Conditional phase probability distributions of structure factors in a Karle–Hauptman matrix (1979)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 35 (1979), S. 105-107 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: From the joint probability distribution of all structure factors in a Karle-Hauptman matrix new phase probability distributions are obtained. These calculations lead to a reformulation of the maximum-determinant rule for phase determination. In addition a new function is derived whose maximum corresponds to the most probable values for the phases of an arbitrary subset of the structure factors in a Karle-Hauptman matrix. This function accounts for the interaction among phases in a Karle-Hauptman matrix through triple products and quartets simultaneously.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739479000188
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  • 6
    Electronic Resource
    Electronic Resource
    Determination of the position of even the lighter anomalous scatterers in a crystal structure by means of a two-wavelength technique (1982)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 38 (1982), S. 710-717 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: For identical anomalous scatterers among a majority of normal scatterers the structure-factor amplitudes are estimated from intensity data obtained either with two wavelengths at one side of the absorption edge or with one wavelength at either side. Direct methods (or a Patterson synthesis) will allow the localization of these anomalous scatterers. Test calculations on the known structure of the iron-containing protein ferredoxin, simulating the effects of synchrotron radiation, show the feasibility of the procedure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739482001430
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  • 7
    Electronic Resource
    Electronic Resource
    On the direct-methods theory of single isomorphous replacement (1987)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 43 (1987), S. 810-820 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The joint probability distribution of six structure factors for a pair of isomorphous structures [Hauptman (1982). Acta Cryst. A38, 289-294] is used for probability calculations in which doublet invariant phase information (i.e. phase-difference information) is employed as conditional information together with intensity data. This information is obtained from the structure-factor magnitudes of the structure formed by the replacement atoms (assumed to be known) and the two isomorphous structures. First, conditional probability distributions of the triplet invariants of the native structure are derived. An alternative to the approach of Fortier, Moore & Fraser [Acta Cryst. (1985), A41,571-577] is presented, based on a new enantiomorph-sensitive distribution. It is argued that application of enantiomorph-sensitive distributions obtained by restriction of phase invariants can be widened by using various enantiomorph-defining invariants. Second, the ambiguity in single isomorphous replacement is resolved by calculating the probability of the two possible solutions as was proposed by Fan Hai-fu, Han Fu-son, Qian Jin-zi & Yao Jia-xing [Acta Cryst. (1984), A40, 489-495], but using a different probabilistic basis. It turns out that the formulae of the latter authors are a special case of formulae derived in the present paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767387098477
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  • 8
    Electronic Resource
    Electronic Resource
    Restriction of the number of terms in the Sayre–Hughes equation connected with a criterion to establish the absence of atomic overlap in projection (1976)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 32 (1976), S. 115-119 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: In the Sayre-Hughes equation the variable reciprocal-lattice vector ranges over the whole reciprocal net. It is shown that under the condition that a projection along a zone axis has no overlapping atoms the variable reciprocal-lattice vector can be restricted to range over a plane of the reciprocal net. A fortiori if a projection on an axis is free from overlap the variable vector can be restricted to range over a row of the reciprocal net. Criteria to determine the projections for which these conditions are best fulfilled are given. These criteria involve the absolute values of the structure factors only. The theory is illustrated by a test employing normalized structure factors calculated from atomic coordinates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567739476000211
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  • 9
    Electronic Resource
    Electronic Resource
    The crystal structures of potassium mesotartrate dihydrate and the isomorphous rubidium salt (1965)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 19 (1965), S. 293-297 
    Details
    ISSN: 0001-5520
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0365110X6500333X
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  • 10
    Electronic Resource
    Electronic Resource
    The crystal and molecular structure of aminomalonic acid (1966)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 21 (1966), S. 990-995 
    Details
    ISSN: 0001-5520
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0365110X66004304
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