http://journals.iucr.org/a/issues/2009/06/00/isscontsbdy.html Acta Crystallographica Section A: Foundations of Crystallography publishes papers reporting fundamental advances in all areas of crystallography in the broadest sense. The central themes are, on the one hand, experimental and theoretical studies of the properties and arrangements of atoms, ions and molecules in condensed matter, ideal or real, and of their symmetry and, on the other, the theoretical and experimental aspects of the various methods to determine these arrangements. en Copyright (c) 2009 International Union of Crystallography 2009-11-01 International Union of Crystallography International Union of Crystallography http://journals.iucr.org urn:issn:0108-7673 Acta Crystallographica Section A: Foundations of Crystallography publishes papers reporting fundamental advances in all areas of crystallography in the broadest sense. The central themes are, on the one hand, experimental and theoretical studies of the properties and arrangements of atoms, ions and molecules in condensed matter, ideal or real, and of their symmetry and, on the other, the theoretical and experimental aspects of the various methods to determine these arrangements. text/html Acta Crystallographica Section A: Foundations of Crystallography, Volume 65, Part 6, 2009 text yearly 6 2002-01-01T00:00+00:00 6 65 2009-11-01 Copyright (c) 2009 International Union of Crystallography Acta Crystallographica Section A: Foundations of Crystallography 443 urn:issn:0108-7673 med@iucr.org November 2009 2009-11-01 http://journals.iucr.org/logos/rss10a.gif http://journals.iucr.org/a/issues/2009/06/00/isscontsbdy.html Still image http://scripts.iucr.org/cgi-bin/paper?sc5027 The parameter-space concept for solving crystal structures from reflection amplitudes (without employing or searching for their phases) is described on a theoretically oriented basis. Emphasis is placed on the principles of the method, on selecting one of three types of parameter spaces discussed in this paper, and in particular on the structure model employed (equal-atom point model, however usually reduced to one-dimensional projections) and on the system of `isosurfaces' representing experimental `geometrical structure amplitudes' in an orthonormal parameter space of as many dimensions as unknown atomic coordinates. The symmetry of the parameter space as well as of the imprinted isosurfaces and its effect on solution methods is discussed. For point atoms scattering with different phases or signs (as is possible in the case of X-ray resonant or of neutron scattering) it is demonstrated that the `landscape' of these isosurfaces remains invariant save certain shifts of origin known beforehand (under the condition that all atomic scattering amplitudes have been reduced to 1 thus meeting the requirement of the structure model above). Partly referring to earlier publications on the subject, measures are briefly described which permit circumventing an analytical solution of the system of structure-amplitude equations and lead to either a unique (unequivocal) approximate structure solution (offering rather high spatial resolution) or to all possible solutions permitted by the experimental data used (thus including also all potential `false minima'). A simple connection to Patterson vectors is given, also a first hint on data errors. References are given for practical details of various solution techniques already tested and for reconstruction of three-dimensional structures from their projections by `point tomography'. We would feel foolish if we tried to aim at any kind of `competition' to existing methods. Having mentioned `pros and cons' of our concept, some ideas about potential applications are nevertheless offered which are mainly based on its inherent resolution power though demanding rather few reflection data (use of optimal intensity contrast included) and possibly providing a result proven to be unique. Copyright (c) 2009 International Union of Crystallography urn:issn:0108-7673 Zimmermann, H. Fischer, K.F. 2009-10-17 doi:10.1107/S0108767309030293 International Union of Crystallography A method of structure determination based on an equal-atom point model is described. The method avoids the phase problem, offers high resolution, works with sparse experimental data and provides all possible (quasi-)homometric solutions. en structure determination parameter spaces unique solution homometric solutions phase problem eliminated The parameter-space concept for solving crystal structures from reflection amplitudes (without employing or searching for their phases) is described on a theoretically oriented basis. Emphasis is placed on the principles of the method, on selecting one of three types of parameter spaces discussed in this paper, and in particular on the structure model employed (equal-atom point model, however usually reduced to one-dimensional projections) and on the system of `isosurfaces' representing experimental `geometrical structure amplitudes' in an orthonormal parameter space of as many dimensions as unknown atomic coordinates. The symmetry of the parameter space as well as of the imprinted isosurfaces and its effect on solution methods is discussed. For point atoms scattering with different phases or signs (as is possible in the case of X-ray resonant or of neutron scattering) it is demonstrated that the `landscape' of these isosurfaces remains invariant save certain shifts of origin known beforehand (under the condition that all atomic scattering amplitudes have been reduced to 1 thus meeting the requirement of the structure model above). Partly referring to earlier publications on the subject, measures are briefly described which permit circumventing an analytical solution of the system of structure-amplitude equations and lead to either a unique (unequivocal) approximate structure solution (offering rather high spatial resolution) or to all possible solutions permitted by the experimental data used (thus including also all potential `false minima'). A simple connection to Patterson vectors is given, also a first hint on data errors. References are given for practical details of various solution techniques already tested and for reconstruction of three-dimensional structures from their projections by `point tomography'. We would feel foolish if we tried to aim at any kind of `competition' to existing methods. Having mentioned `pros and cons' of our concept, some ideas about potential applications are nevertheless offered which are mainly based on its inherent resolution power though demanding rather few reflection data (use of optimal intensity contrast included) and possibly providing a result proven to be unique. text/html Structure determination without Fourier inversion. V. A concept based on parameter space text 6 65 2009-10-17 Copyright (c) 2009 International Union of Crystallography Acta Crystallographica Section A: Foundations of Crystallography research papers 443 455 http://scripts.iucr.org/cgi-bin/paper?au5093 An open-ended classification scheme for crystal structures based on Wyckoff sets and affine normalizer groups is proposed. It is free of metrical and geometrical considerations. All structures of one structure type belong to the same symmetry class. An application is given for the Inorganic Crystal Structure Database (version 2, 2007). Copyright (c) 2009 International Union of Crystallography urn:issn:0108-7673 Burzlaff, H. Zimmermann, H. 2009-10-17 doi:10.1107/S0108767309030116 International Union of Crystallography An open-ended classification scheme for crystal structures based on Wyckoff sets and affine normalizer groups is proposed. en crystal structure classification Wyckoff positions Wyckoff sets affine normalizers An open-ended classification scheme for crystal structures based on Wyckoff sets and affine normalizer groups is proposed. It is free of metrical and geometrical considerations. All structures of one structure type belong to the same symmetry class. An application is given for the Inorganic Crystal Structure Database (version 2, 2007). text/html On symmetry classes of crystal structures text 6 65 2009-10-17 Copyright (c) 2009 International Union of Crystallography Acta Crystallographica Section A: Foundations of Crystallography research papers 456 465 http://scripts.iucr.org/cgi-bin/paper?dm5009 A method for analyzing and classifying two-dimensional pure point diffraction spectra (i.e. a set of Bragg peaks) of certain self-similar structures with scaling factor β > 1, such as quasicrystals, is presented. The two-dimensional pure point diffraction spectrum Π is viewed as a point set in the complex plane in which each point is assigned a positive number, its Bragg intensity. Then, by using a nested sequence of self-similar subsets called β-lattices, we implement a multiresolution analysis of the spectrum Π. This analysis yields a partition of Π simultaneously in geometry, in scale and in intensity (the `fingerprint' of the spectrum, not of the diffracting structure itself). The method is tested through numerical explorations of pure point diffraction spectra of various mathematical structures and also with the diffraction pattern of a realistic model of a quasicrystal. Copyright (c) 2009 International Union of Crystallography urn:issn:0108-7673 Elkharrat, A. Gazeau, J.-P. Dénoyer, F. 2009-10-17 doi:10.1107/S0108767309028499 International Union of Crystallography The classification of diffraction spectra of aperiodic crystals based on multiresolution analysis is described. en quasicrystals diffraction spectra self-similar structures multiresolution analysis A method for analyzing and classifying two-dimensional pure point diffraction spectra (i.e. a set of Bragg peaks) of certain self-similar structures with scaling factor β > 1, such as quasicrystals, is presented. The two-dimensional pure point diffraction spectrum Π is viewed as a point set in the complex plane in which each point is assigned a positive number, its Bragg intensity. Then, by using a nested sequence of self-similar subsets called β-lattices, we implement a multiresolution analysis of the spectrum Π. This analysis yields a partition of Π simultaneously in geometry, in scale and in intensity (the `fingerprint' of the spectrum, not of the diffracting structure itself). The method is tested through numerical explorations of pure point diffraction spectra of various mathematical structures and also with the diffraction pattern of a realistic model of a quasicrystal. text/html Multiresolution of quasicrystal diffraction spectra text 6 65 2009-10-17 Copyright (c) 2009 International Union of Crystallography Acta Crystallographica Section A: Foundations of Crystallography research papers 466 489 http://scripts.iucr.org/cgi-bin/paper?cn5019 A high-resolution single-crystal X-ray study of paracetamol has been performed at 85 K. Different approaches to modeling the experimental electron density (ED) were tested for the dynamically disordered portions of the molecule in order to check to what extent it is possible to obtain a proper ED distribution in the ordered part. Models were examined in which the methyl-group ED was built from pseudoatoms taken from the University at Buffalo Pseudoatom Databank or the Invariom database, with multipole parameters for the remaining atoms being obtained from free refinement. The κ′ restricted multipolar model (KRMM) and free κ′ refinements were compared; restriction of the κ′ parameters was essential in order to obtain values of the electrostatic interaction energy consistent with the results of theoretical single-point periodic calculations. After simultaneous use of KRMM refinement and the databases to model the methyl group, the bond critical point properties and interaction electrostatic energy values were found to be closer to those obtained from theory. Additionally, some discrepancies in the ED distribution and dipole moment among transferred aspherical atom model refinements utilizing both theoretical databases and parameters from theoretical periodic calculations are shown. Including the influence of the crystal field in the periodic calculations increases the ED in the hydroxyl and amide groups, thus leading to higher values of the electrostatic interaction energy, changes in the electrostatic potential values mapped on the isodensity surface and changes in the shape of the anisotropic displacement parameters with respect to results found for both database models. Copyright (c) 2009 International Union of Crystallography urn:issn:0108-7673 Bąk, J.M. Dominiak, P.M. Wilson, C.C. Woźniak, K. 2009-10-17 doi:10.1107/S0108767309031729 International Union of Crystallography On the basis of high-resolution single-crystal X-ray diffraction data for paracetamol, different approaches (including those based on pseudoatom databases) to modeling of the static experimental electron density in the presence of a dynamically disordered molecular fragment were tested. The electrostatic properties obtained were compared with the results of theoretical single-point periodic calculations. en experimental charge density University at Buffalo Pseudoatom Databank Invariom database aspherical atom model paracetamol A high-resolution single-crystal X-ray study of paracetamol has been performed at 85 K. Different approaches to modeling the experimental electron density (ED) were tested for the dynamically disordered portions of the molecule in order to check to what extent it is possible to obtain a proper ED distribution in the ordered part. Models were examined in which the methyl-group ED was built from pseudoatoms taken from the University at Buffalo Pseudoatom Databank or the Invariom database, with multipole parameters for the remaining atoms being obtained from free refinement. The κ′ restricted multipolar model (KRMM) and free κ′ refinements were compared; restriction of the κ′ parameters was essential in order to obtain values of the electrostatic interaction energy consistent with the results of theoretical single-point periodic calculations. After simultaneous use of KRMM refinement and the databases to model the methyl group, the bond critical point properties and interaction electrostatic energy values were found to be closer to those obtained from theory. Additionally, some discrepancies in the ED distribution and dipole moment among transferred aspherical atom model refinements utilizing both theoretical databases and parameters from theoretical periodic calculations are shown. Including the influence of the crystal field in the periodic calculations increases the ED in the hydroxyl and amide groups, thus leading to higher values of the electrostatic interaction energy, changes in the electrostatic potential values mapped on the isodensity surface and changes in the shape of the anisotropic displacement parameters with respect to results found for both database models. text/html Experimental charge-density study of paracetamol – multipole refinement in the presence of a disordered methyl group text 6 65 2009-10-17 Copyright (c) 2009 International Union of Crystallography Acta Crystallographica Section A: Foundations of Crystallography research papers 490 500 http://scripts.iucr.org/cgi-bin/paper?zm5063 The mineral kettnerite, CaBi(OFCO3), is a rare example of an order–disorder (OD) structure with a quadratic net. The lattice parameters of the simplest possible 1O polytype are a = 5.3641 (1), b = 5.3641 (1), c = 13.5771 (2) Å, and the space group is Pbaa. There are three kinds of OD layers, identical to structure-building layers. Two of them are non-polar: the Bi—O and Ca—F at z = 0 and z = 1/2, respectively, with the layer-group symmetry C2/m2/m(4/a,b)21/m21/m. The third kind of OD layer of CO3 groups (located between the Bi—O and Ca—F layers) is polar, with alternating sense of polarity. The layer group is Pba(4)mm. Triangular CO3 groups are parallel to (110) or (1\bar10) planes with one O atom oriented towards the Bi—O layer and the remaining two O atoms oriented towards the Ca—F layer. The orientations of CO3 groups alternate along the [110] and [1\bar10] directions. As a result, each group parallel to (110) is surrounded by four nearest neighbors parallel to (1\bar10) and vice versa. These positions can be interchanged by an (a + b)/2 shift or by π/2 rotation; thus stacking of the layer onto adjacent ones is ambiguous. Instead of OD layers, the polytypes are generated by stacking of OD packets, comprising the whole CO3 layers and adjacent halves of the Bi—O and Ca—F layers. They are polar, with alternating sense of polarity; the layer group is Pba(4)mm. Stacking sequences are expressed by ball-and-stick models, with the aid of symbolic figures, and by sequences of orientational characters. There are two maximum-degree-of-order (MDO) polytypes, 1O (really found and described, see lattice parameters and space group above) and 2O, with doubled c parameter and space group Ibca (not yet found). The derivation of the MDO generating operations of both polytypes is presented in this paper. The stacking rule also allows another, non-MDO, polytype with doubled c, i.e. the 2Q polytype, space group P42bc (tetragonal, not yet found). Various kinds of domains can exist: (i) out-of-step domains shifted by (a + b)/2, (ii) twin domains rotated by π/2 around local tetrads of odd or even packets, and (iii) upside-down domains in the polar 2Q polytype. Stacking sequences of 16 possible domains of the polytypes mentioned above are listed. Also 60 domains of four distinct six-packet polytypes are theoretically possible. Copyright (c) 2009 International Union of Crystallography urn:issn:0108-7673 Hybler, J. Ďurovič, S. 2009-10-17 doi:10.1107/S0108767309037702 International Union of Crystallography The mineral kettnerite, CaBi(OFCO3), has an order–disorder (OD) structure with a quadratic net built up by more than one kind of layer. Two maximum-degree-of-order (MDO) (1O, 2O) and one non-MDO (2Q) polytypes are derived by stacking of regularly alternating polar OD packets instead of layers. The stacking rule allows the existence of out-of-step, twin and upside-down domains. en kettnerite OD structure polytypism The mineral kettnerite, CaBi(OFCO3), is a rare example of an order–disorder (OD) structure with a quadratic net. The lattice parameters of the simplest possible 1O polytype are a = 5.3641 (1), b = 5.3641 (1), c = 13.5771 (2) Å, and the space group is Pbaa. There are three kinds of OD layers, identical to structure-building layers. Two of them are non-polar: the Bi—O and Ca—F at z = 0 and z = 1/2, respectively, with the layer-group symmetry C2/m2/m(4/a,b)21/m21/m. The third kind of OD layer of CO3 groups (located between the Bi—O and Ca—F layers) is polar, with alternating sense of polarity. The layer group is Pba(4)mm. Triangular CO3 groups are parallel to (110) or (1\bar10) planes with one O atom oriented towards the Bi—O layer and the remaining two O atoms oriented towards the Ca—F layer. The orientations of CO3 groups alternate along the [110] and [1\bar10] directions. As a result, each group parallel to (110) is surrounded by four nearest neighbors parallel to (1\bar10) and vice versa. These positions can be interchanged by an (a + b)/2 shift or by π/2 rotation; thus stacking of the layer onto adjacent ones is ambiguous. Instead of OD layers, the polytypes are generated by stacking of OD packets, comprising the whole CO3 layers and adjacent halves of the Bi—O and Ca—F layers. They are polar, with alternating sense of polarity; the layer group is Pba(4)mm. Stacking sequences are expressed by ball-and-stick models, with the aid of symbolic figures, and by sequences of orientational characters. There are two maximum-degree-of-order (MDO) polytypes, 1O (really found and described, see lattice parameters and space group above) and 2O, with doubled c parameter and space group Ibca (not yet found). The derivation of the MDO generating operations of both polytypes is presented in this paper. The stacking rule also allows another, non-MDO, polytype with doubled c, i.e. the 2Q polytype, space group P42bc (tetragonal, not yet found). Various kinds of domains can exist: (i) out-of-step domains shifted by (a + b)/2, (ii) twin domains rotated by π/2 around local tetrads of odd or even packets, and (iii) upside-down domains in the polar 2Q polytype. Stacking sequences of 16 possible domains of the polytypes mentioned above are listed. Also 60 domains of four distinct six-packet polytypes are theoretically possible. text/html The OD interpretation of the crystal structure of kettnerite CaBiOFCO3 text 6 65 2009-10-17 Copyright (c) 2009 International Union of Crystallography Acta Crystallographica Section A: Foundations of Crystallography research papers 501 511 http://scripts.iucr.org/cgi-bin/paper?sh5093 The method of joint probability distribution functions has been applied to molecular replacement techniques. The rotational search is performed by rotating the reciprocal lattice of the protein with respect to the calculated transform of the model structure; the translation search is performed by fast Fourier transform. Several cases of prior information are studied, both for the rotation and for the translation step: e.g. the conditional probability density for the rotation or the translation of a monomer is found both for ab initio and when the rotation and/or the translation values of other monomers are given. The new approach has been implemented in the program REMO09, which is part of the package for global phasing IL MILIONE [Burla, Caliandro, Camalli, Cascarano, De Caro, Giacovazzo, Polidori, Siliqi & Spagna (2007). J. Appl. Cryst. 40, 609–613]. A large set of test structures has been used for checking the efficiency of the new algorithms, which proved to be significantly robust in finding the correct solutions and in discriminating them from noise. An important design concept is the high degree of automatism: REMO09 is often capable of providing a reliable model of the target structure without any user intervention. Copyright (c) 2009 International Union of Crystallography urn:issn:0108-7673 Caliandro, R. Carrozzini, B. Cascarano, G.L. Giacovazzo, C. Mazzone, A. Siliqi, D. 2009-10-17 doi:10.1107/S0108767309035612 International Union of Crystallography The method of joint probability distribution functions has been applied to molecular replacement techniques. en molecular replacement protein crystallography joint probability distribution functions The method of joint probability distribution functions has been applied to molecular replacement techniques. The rotational search is performed by rotating the reciprocal lattice of the protein with respect to the calculated transform of the model structure; the translation search is performed by fast Fourier transform. Several cases of prior information are studied, both for the rotation and for the translation step: e.g. the conditional probability density for the rotation or the translation of a monomer is found both for ab initio and when the rotation and/or the translation values of other monomers are given. The new approach has been implemented in the program REMO09, which is part of the package for global phasing IL MILIONE [Burla, Caliandro, Camalli, Cascarano, De Caro, Giacovazzo, Polidori, Siliqi & Spagna (2007). J. Appl. Cryst. 40, 609–613]. A large set of test structures has been used for checking the efficiency of the new algorithms, which proved to be significantly robust in finding the correct solutions and in discriminating them from noise. An important design concept is the high degree of automatism: REMO09 is often capable of providing a reliable model of the target structure without any user intervention. text/html Molecular replacement: the probabilistic approach of the program REMO09 and its applications text 6 65 2009-10-17 Copyright (c) 2009 International Union of Crystallography Acta Crystallographica Section A: Foundations of Crystallography research papers 512 527 http://scripts.iucr.org/cgi-bin/paper?sc5029 In order to extend the application field of the direct-methods S-FFT phase-refinement algorithm to density functions with positive and negative peaks, the equal-sign constraint was removed from its definition by combining ρ2 with an appropriate density function mask [Rius & Frontera (2008). Acta Cryst. A64, 670–674]. This generalized algorithm (S2-FFT) was shown to be highly effective for crystal structures with at least one moderate scatterer in the unit cell but less effective when applied to structures with only light scatterers. To increase the success rate in this second case, the mask has been improved and the convergence rate of S2-FFT has been investigated. Finally, a closely related but simpler phase-refinement function (Sm) combining ρ (instead of ρ2) with a new mask is introduced. For simple cases at least this can also treat density peaks in the absence of the equal-sign constraint. Copyright (c) 2009 International Union of Crystallography urn:issn:0108-7673 Rius, J. Frontera, C. 2009-10-17 doi:10.1107/S0108767309038136 International Union of Crystallography The success rate of the direct-methods sign-unconstrained S-FFT algorithm has been improved for density functions with only light scatterers. In addition, a closely related but simpler phase-refinement function is introduced, which can also treat positive and negative density peaks. en direct methods S-FFT algorithm phase refinement In order to extend the application field of the direct-methods S-FFT phase-refinement algorithm to density functions with positive and negative peaks, the equal-sign constraint was removed from its definition by combining ρ2 with an appropriate density function mask [Rius & Frontera (2008). Acta Cryst. A64, 670–674]. This generalized algorithm (S2-FFT) was shown to be highly effective for crystal structures with at least one moderate scatterer in the unit cell but less effective when applied to structures with only light scatterers. To increase the success rate in this second case, the mask has been improved and the convergence rate of S2-FFT has been investigated. Finally, a closely related but simpler phase-refinement function (Sm) combining ρ (instead of ρ2) with a new mask is introduced. For simple cases at least this can also treat density peaks in the absence of the equal-sign constraint. text/html Improving the direct-methods sign-unconstrained S-FFT algorithm. XV text 6 65 2009-10-17 Copyright (c) 2009 International Union of Crystallography Acta Crystallographica Section A: Foundations of Crystallography research papers 528 531 http://scripts.iucr.org/cgi-bin/paper?zm5061 An analysis of certain types of multiplicative congruential generators – otherwise known for their application to the sequential generation of pseudo-random numbers – reveals their relation to the coordinate description of lattice points in two-dimensional primitive sublattices. Taking the index of the lattice–sublattice transformation as the modulus of the multiplicative congruential generator, there are special choices for its multiplier which induce a symmetry-preserving permutation of lattice-point coordinates. From an analysis of similar sublattices with hexagonal and square symmetry it is conjectured that the cycle structure of the permutation has its crystallographic counterpart in the description of crystallographic orbits. Some applications of multiplicative congruential generators in structural chemistry and biology are discussed. Copyright (c) 2009 International Union of Crystallography urn:issn:0108-7673 Hornfeck, W. Harbrecht, B. 2009-10-17 doi:10.1107/S0108767309037088 International Union of Crystallography An analysis of certain types of multiplicative congruential generators – otherwise known for their application to the sequential generation of pseudo-random numbers – reveals their relation to lattice–sublattice transformations and the coordinate description of crystal structures. en multiplicative congruential generators lattice–sublattice transformation lattice points crystallographic orbits An analysis of certain types of multiplicative congruential generators – otherwise known for their application to the sequential generation of pseudo-random numbers – reveals their relation to the coordinate description of lattice points in two-dimensional primitive sublattices. Taking the index of the lattice–sublattice transformation as the modulus of the multiplicative congruential generator, there are special choices for its multiplier which induce a symmetry-preserving permutation of lattice-point coordinates. From an analysis of similar sublattices with hexagonal and square symmetry it is conjectured that the cycle structure of the permutation has its crystallographic counterpart in the description of crystallographic orbits. Some applications of multiplicative congruential generators in structural chemistry and biology are discussed. text/html Multiplicative congruential generators, their lattice structure, its relation to lattice–sublattice transformations and applications in crystallography text 6 65 2009-10-17 Copyright (c) 2009 International Union of Crystallography Acta Crystallographica Section A: Foundations of Crystallography research papers 532 542 http://scripts.iucr.org/cgi-bin/paper?pf0074 Copyright (c) 2009 International Union of Crystallography urn:issn:0108-7673 Aroyo, M.I. 2009-10-17 doi:10.1107/S0108767309036125 International Union of Crystallography en book review text/html Foundations of Crystallography with Computer Applications. By Maureen M. Julian. Boca Raton: CRC Press, 2008. Pp. xxvi + 340. Price (hardback) GBP 55.00. ISBN 978-1-4200-6075-1. text 6 65 2009-10-17 Copyright (c) 2009 International Union of Crystallography Acta Crystallographica Section A: Foundations of Crystallography book reviews 543 545 http://scripts.iucr.org/cgi-bin/paper?es0374 Copyright (c) 2009 International Union of Crystallography urn:issn:0108-7673 Marks, L.D. 2009-10-17 doi:10.1107/S0108767309042445 International Union of Crystallography en Gjønnes Medal text/html Gjønnes Medal in Electron Crystallography – call for nominations text 6 65 2009-10-17 Copyright (c) 2009 International Union of Crystallography Acta Crystallographica Section A: Foundations of Crystallography international union of crystallography 546 546 http://scripts.iucr.org/cgi-bin/paper?es0373 Copyright (c) 2009 International Union of Crystallography urn:issn:0108-7673 Dacombe, M.H. 2009-10-17 doi:10.1107/S0108767309042421 International Union of Crystallography en prices of journals text/html Prices of IUCr journals text 6 65 2009-10-17 Copyright (c) 2009 International Union of Crystallography Acta Crystallographica Section A: Foundations of Crystallography international union of crystallography 547 548