bluuebunny/crossref_metadata_2025 huggingface dataset:
Room- and high-temperature single crystal diffraction studies on γ-Na2Si2O5: an interrupted framework with exclusively Q3-units
Authors: Kahlenberg V. , Rakić S. , Weidenthaler C.
Published: December 2003

Single crystals of γ-Na2Si2O5 have been obtained from the crystallization of a stoichiometric glass at 520 °C. The monoclinic crystals belong to space group C2/c (a = 33.326(2) Å, b = 14.1457(7) Å, c = 26.206(2) Å, β = 108.60(2)°, V = 11709.0(1.5) Å3, Z = 96, D
calc = 2.48 g cm–3). The diffraction pattern showed the typical features of a superstructure. The structure was solved by direct methods including the pseudo-translational effects as a prior information for the normalization process and subsequently refined to a residual of R1 = 0.058. The compound can be classified as an interrupted tetrahedral framework with exclusively Q3-units. Basic building units are spiral achter single chains running parallel [010]. Every four of these chains are linked via common corners, surrounding a central tunnel where the sodium atoms are located for charge compensation. The framework density has a value of 16.4 T-atoms/1000 Å3. At 563°C the monoclinic phase undergoes a structural phase transition into a tetragonal high temperature modification (space group I41/a, a = 11.869(2) Å, c = 7.176(2) Å, V = 1011.0(6) Å3, Z = 4). The transition is induced by cooperative rotations of the tetrahedra and involves a bisection of the translation period along the spiral chains. The symmetries of both modifications are in a close relationship: the space group of the RT-phase is a subgroup of index 24 of the space group of the HT-phase. Focussing on the connectivity of the tetrahedra the two phases are identical and can be characterized as defect—cristobalites where 20 of the tetrahedra have been removed. Topologically they can be described as three dimensional 3-connected nets of a type which has been already observed in the intermetallic compounds LiGe and LiSi, as well as in the mineral grumantite.
General structural relationships between rutile-type VO2 and the Magnéli-phases VnO2

n

–1
Authors: Katzke H. , Schlögl R.
Published: December 2003

The structures of the Magnéli-phases V
n
O2

n

–1 (3 ≤ n ≤ 7) are reviewed with respect to their structural relationships to rutile-type VO2. The general expressions for the transformation matrices P and Q = P
–1 are derived allowing the prediction of lattice parameters and atomic coordinates for hypothetical structures of V
n
O2

n

–1 with n ≥ 8.
Crystal structures of N-(trichloroacetyl)morpholine and 2,6-di(trichloroacetyl)cyclohexanone
Authors: Özbey Süheyla , Kaynak F. B. , Şenöz H. , Tunoğlu N.
Published: December 2003

The crystal and molecular structure of the title compounds have been determined by X-ray analysis (N-(trichloroacetyl)morpholine, C6H8Cl
3NO2, P21/a, a = 9.869(1) Å, b = 12.287(1) Å, c = 16.060(1) Å, β = 98.773(7)°, Z = 8; 2,6-di(trichloroacetyl)cyclohexanone, C10H8Cl
6O3, Pbca, a = 10.553(1) Å, b = 15.405(2) Å, c = 18.435(2) Å, Z = 4). The morpholine and cyclohexane rings of both compounds adopt the chair conformation. There are some intra- and intermolecular hydrogen bonds in the title compounds, so the crystal structures of them are stabilized by C—H...Cl and C—H...O intra- and inter molecular hydrogen bonds.
Hydroxy-alkyl bisphosphonic acid partial esters (HABPA-PE): Structures of two symmetrical and non-symmetrical members of a new class of prodrugs in bone disease treatments
Authors: Barbey C. , Lecouvey M. , Mallard I. , Prangé Th. , Neuman A. , Lance M. , Navaza A.
Published: December 2003

Two new hydroxy alkyl bisphosphonate partial esters (HABPA-PE) have been crystallised. The first compound C6H15NaO7P2C2H5O, crystallises as an ethanol solvate and forms rigid infinite β-sheet-like ribbons. The second, C6H16O7P2, displays self-association in dimers. In these new structures, packing analyses confirm the enhanced hydrophobic character due to partial esterification compared to naked hydroxybisphosphonic acids and the simplification of their H bonding patterns.
Ab-initio XRPD structural characterization of coordination polymers: the case of [Ag(C3H3N2CS2)]
Authors: Masciocchi N. , Brenna S. , Galli S. , Maspero A.
Published: December 2003

The crystal structure of the one-dimensional polymer [Ag(C3H3N2CS2)] has been determined from conventional X-ray powder diffraction methods, through simulated annealing and Rietveld refinement techniques [Ag(C3H3N2CS2)] is monoclinic, P21/c; a = 8.409(1), b = 11.740(1), c = 6.721(1) Å, β = 101.86(2)°, V = 649.3(2) Å3; Z = 4; ρ = 2.566 g cm-3 Final Rwp
, Rp
and RF
agreement factors, for 3100 data points collected in the 8–70° 2θ range, are 0.091, 0.071 and 0.058, respectively Anisotropic peak shapes and high-angle tails for the 0k0 (and neighboring) reflections suggest that the polymeric chains, aligned along b, suffer from a partial disorder, in that packing of adjacent molecules does not conform to a rigorous crystalline, truly periodic, tiling.
Preparation and crystal structure of a new high-pressure phase (V0.5Re0.5)O2 with rutile-type structure
Authors: Bramnik K. G. , Ehrenberg H. , Theissmann R. , Fuess H. , Morán E.
Published: December 2003

The new complex oxide (V0.5Re0.5)O2 has been synthesized under high pressure of 60 kbar at 1000°C, and its crystal structure determined by single crystal X-ray diffraction data analysis (S.G.: P42/mnm, a = 4.6357(4) Å, c = 2.8292(3) Å, V = 60.80(1) Å3). This compound adopts a rutile-type structure with random cat ion distribution on one crystallographic site. The substitution of 50 vanadium by rhenium stabilizes the high temperature form of VO2 at room temperature. The cation ratio of 1 : 1 was confirmed by EDX analysis performed by electron microscopy on the same crystals used for X-ray diffraction.
Electron crystallography of zeolites. 1. Projected crystal structures of ZSM-5 and ZSM-11
Authors: Dorset Douglas L.
Published: December 2003

The prospect of carrying out quantitative crystal structure analyses by direct methods with electron diffraction intensity data from zeolites is evaluated for two related materials: ZSM-5 and ZSM-11. The stacked plate-like arrays of ZSM-5 induce intensity perturbations from secondary electron scattering; nevertheless, the T-site positions can be found by direct methods. Intensity data from smaller ZSM-11 microcrystals are more favorable for ab initio analysis so that some oxygen positions are found during Fourier refinement. For intergrowths of one zeolite in the other, the nature of the inclusions has been found to depend on the dominant species. If ZSM-5 is dominant, the apparent ZSM-11 inclusions (assuming a preferred platy orientation) could be rather large, whereas if ZSM-11 is dominant, the ZSM-5 inclusions extend over only 3 or 4 unit cells.
The structures of ZrNCl, TiOCl and AlOCl in the light of the Zintl-Klemm concept
Authors: Vegas A. , Santamaría-Pérez D.
Published: December 2003

The structures of ZrNCl on one hand and TiOCl and AlOCl on the other hand are analysed in comparison with the Zintl phases Ca[Al2Si2] and Na[AlSi], respectively. In the former, the [ZrN]+ sublattice is isostructural to the [Al2Si2]2- skeleton whereas the latter are orthorhombic distortions of the Na[AlSi] structure. The three structures can be rationalised by means of an inverse Zintl-Klemm concept, in similarity with the Zintl-Klemm concept which accounts for the structures of the Zintl phases. In addition, Ca[Al2Si2] presents the same structure than the hexacelsian oxide Ca[Al2Si2O8] providing a new example of how the cation arrays, in oxides, maintain the structure of their respective alloy.
Single crystal neutron diffraction study of the phase transition in (NH4)H5(PO4)2
Authors: Troyanov Sergej I. , Kosterina E. V. , Loose A. , Reehuis M. , Kemnitz Erhard
Published: December 2003

The crystal structure of NH4H5(PO4)2 was investigated at 298 and 80 K by single crystal neutron diffraction. The room temperature modification II crystallizes monoclinic (space group C2/c), a = 10.156(4), b = 7.554(3), c = 9.507(4) Å, β = 100.71(4)°, Z = 4. It is characterized by disorder of the NH4
+ cations and short symmetrical hydrogen bonds (2.422(8) Å) connecting the layers of H2PO4 tetrahedra. The low temperature modification I is monoclinic, (space group P21/c), a = 10.040(4), b = 7.628(2), c = 9.558(3) Å, β = 102.51(4)°, Z = 4. Below the phase transition the NH4
+ cations become ordered and the layers of PO4 tetrahedra are connected by asymmetrical hydrogen bonds (2.427(7) Å) allowing to formulate the phase I as (NH4)(H2PO4)(H3PO4). The changes in the thermal ellipsoids and a possible mechanism of the phase transition are discussed.
The crystal structure of Er(HPO4)(NO3)·3 H2O: ab initio determination from X-ray powder diffraction data
Authors: Ivashkevich L. S. , Lyakhov A. S. , Selevich A. F. , Petrusevich Yu. I.
Published: December 2003

The crystal structure of orthorhombic Er(HPO4)(NO3)·3 H2O has been determined from X-ray powder diffraction data. The unit cell dimensions are a = 10.1653(4) Å, b = 11.9178(5) Å, c = 6.8533(3) Å, V = 830.26(6), Z = 4. The space group is Pbcm (No. 57) or Pbc21 (No. 29). The structures were solved ab initio using EXPO program and refined by FULLPROF package. Because geometrical features of the two solutions are the same, the crystal structure has been described in the scope of the centrosymmetric Pbcm space group. Positions of the hydrogen atoms were not defined. The erbium atom is eight coordinated. It is surrounded by one nitrate anion, one water molecule and four phosphate groups. [ErO8] polyhedra are linked together through their edges forming infinite chains extended along the c axis. The chains are connected by phosphate groups to form layers palallel to the yz plane. Probable hydrogen bonds are discussed.
Molecular and crystal structure of 5-amino-1H-[1,2,4]triazole-3-carboxylic acid derivatives
Authors: Wawrzycka-Gorczyca I. , Rzeszotarska B. , Dżygiel A. , Masiukiewicz E. , Kozioł A. E.
Published: December 2003

The analysis of molecular structures of three derivatives: 5-amino-3-carbomethoxy-1-methyl-1H-[1,2,4]-triazole (1), 1-acetyl-5-amino-3-carbomethoxy-1H-[1,2,4]-triazole (2) and 5-acetylamino-3-carbomethoxy-1-methyl-1H-[1,2,4]triazole (3) indicate the sensitivity of the N2–N1–C5 fragment of the triazole ring to the substitution. Molecular conformations are influenced by several intra- and intermolecular contacts. In all structures very extensive N–H···N/O and C–H(methyl)···O/N net of secondary interactions is formed. This kind of interactions is common in crystal structures which are proton-deficient and for this reason various types of multi-point interactions are forced. Besides, triazole π···π stacking interactions are observed.
Synthesis and structural investigation of (4-methoxy-phenyl)-[4-(4-methoxy-phenyl)-1-(1-phenylethylidene-amino)-2-thioxo-1,2-dihydro-pyrimidin-5-yl]-methanone
Authors: Akkurt M. , Sarıpınar E. , Öztürk S. , Yılmaz C. , Fun H.-K.
Published: December 2003

The crystal structure of (4-methoxy-phenyl)-[4-(4-methoxy-phenyl)-1-(1-phenylethylideneamino)-2-thioxo-1,2-dihydro-pyrimidin-5-yl]-methanone, has beeen determined by single-crystal X-ray diffraction at 183(2) K. The compound crystallizes in the monoclinic system, space group P21/c. The O3 and C19 atoms in the methoxy group shows conformational disorder. In the title compound, the pyrimidine ring is slightly nonplanar. The angle between the planes formed by the ring atoms N2–C2–C3 and C1–N1–C4 is 4.0 (1)°. The three phenyl rings form dihedral angles of 147.9 (1), 113.0 (1) and 103.2 (1)° with the pyrimidine ring. The structure is stabilized by weak intermolecular C–H...O interactions.
Structural and spectral studies of N-(3-hydroxypyridine-2-yl)salicylideneimine and N-(3-hydroxypyridine-2-yl)-5-bromosalicylideneimine and their dimethyltin(IV) complexes
Authors: Öztaş S. G. , Şahin E. , Ancın N. , İde S. , Tüzün M.
Published: December 2003

N-(3-hydroxypyridine-2-yl)salicylidineimine (1), N-(3-hydroxypyridine-2-yl)-5-bromo salicylideneimine (2) and their diorganotin(IV) complexes formulated as Me2Sn(OC6H4CH=NC5H3NO) (3) and Me2Sn(OC6H3BrCH=NC5H3NO) (4) were prepared and characterized by 1H-NMR, IR, mass spectroscopy and single crystal x-ray diffraction study. The crystal structures of 3 [orthorhombic, Pbna (no 60); a = 10.439(1) Å, b = 13.388(3) Å, c = 19.340(2) Å, Z = 4; V = 2703(1) Å3] and 4 [monoclinic, P21/a (no 14); a = 7.528(4) Å, b = 16.576(7) Å, c = 12.017(7) Å, β = 97.97(5), Z = 4; V = 1485(1) Å3] have been solved by standard methods and refined by full-matrix least squares (carried out on F
2) to R values of 0.066 and 0.046 respectively. The studied tin(IV) complexes (3 and 4) exhibit the distorted trigonal-bipyramidal geometries around Sn atoms, separately. The tautomeric effects of ligands and the substitution of Br atom to the common molecular structure were discussed beside of the coordination geometries of 3 and 4.
Synthesis, crystal structure and electrochemical behaviour of [2,6-bis(3,5-dimethylpyrazolyl)pyridine](dithiocyanato)cobalt(II)
Authors: Arıcı C. , Ülkü D. , Kurtaran R. , Emregül K. C. , Atakol O.
Published: December 2003

A mononuclear cobalt(II) complex, [Co(dmpp)(SCN)2], was synthesized using 2,6-bis (3,5-dimethylpyrazolyl)pyridine (dmpp) and thiocyanate anion (SCN), and characterized by IR spectroscopy and single-crystal X-ray diffraction. In addition, cyclic voltammetric studies have been performed. The complex crystalizes in monoclinic space group C 2/c, with unit cell dimensions a = 15.2469(15), b = 9.1120(9), c = 14.0302(11) Å, β = 95.823(3)°. The cell containes 4 molecules.
Crystal structure and properties of L-arginine diphosphate
Authors: Haussühl S. , Karapetyan H. A. , Petrosyan A. M.
Published: December 2003

Single crystals of L-arginine diphosphate (L-HN:C(NH2)NH(CH2)3CH(NH2)COOH·2 H3PO4, abbreviated as LADP) with dimensions of ca 15 × 20 × 40 mm and of optical quality were grown by controlled evaporation of aqueous solutions. A structure analysis showed that LADP (space group P212121, a
1 = 9.681(2), a
2 = 21.756(4), a
3 = 7.000(14) Å, Z = 4 at 293 K) is isotypic to L-arginine·2 H3AsO4. The tensors of thermal expansion as well as of dielectric, elastic, thermoelastic, piezoelastic and piezoelectric properties were measured and compared with corresponding properties of L-arginine·H3PO4·H2O (LAP).
The (3 + 1)-dimensional superspace description of the commensurately modulated structure of p-chlorobenzamide (α-form) and its relation to the γ-form
Authors: Schönleber A. , Pattison P. , Chapuis G.
Published: December 2003

The room temperature structure (α-form) of the organic compound p-chlorobenzamide, C7H6ClNO, can be described as a classical three-dimensional periodic superstructure (α
S) and also as a commensurately modulated structure (α
M) in (3 + 1)-dimensional superspace. The diffraction pattern is characterized by a clear difference in intensity between main and satellite reflections. All reflections can be indexed with four indices hklm in a triclinic unit cell and one modulation vector in the superspace group P1̅(αβγ) with the modulation vector q⃗ = 1/3·a⃗*. The structure undergoes a phase transition at higher temperature. In this phase transition the modulation vanishes as indicated by the disappearance of the satellite reflections. The resulting high temperature phase (γ-form) contains one molecule in the asymmetric unit, the space group is P1̅. The high temperature structure (γ) is very close to the reference structure of the modulated model at room temperature. The phase transition can therefore be understood as a loss of the modulation at high temperature.
Rietveld refinement of incommensurate low tridymite
Authors: Graetsch H. A.
Published: December 2003

The incommensurate modification of SiO2 low-tridymite was refined in the 3 + 1 dimensional superspace group Cc(α0γ) 0 at 295 and 325 K from X-ray powder diffraction data. The displacive modulation mainly consists of tiltings of rigid SiO4/2 tetrahedra with the wave vector r = 0.656a* – 0.496c* (dimensions of the average cell: a = 5.005 Å, b = 8.598 Å, c = 8.213 Å and β = 91.50°). The largest amplitude is ca. 0.6 Å for oxygen and ca. 0.3 Å for silicon. Wave vector and amplitudes of the displacive modulation functions vary only very little with increasing temperature.
Wickenburgite, a double-layer silicate Pb3Al[6][Ca[6]Al[4]Si[4]
10O27(H2O)3]·H2O: Crystal chemistry and thermal behaviour
Authors: Hesse K.-F. , Liebau F. , Eulert H.-H.
Published: December 2003

To clarify discrepancies in the literature with regard to the water content and crystal structure of wickenburgite, chemical and thermal analyses and IR spectroscopic measurements were made and the structure was redetermined with single-crystal X-ray diffraction data. It was found that the idealised composition of the mineral is Pb3Al2CaSi10O27·4 H2O rather than Pb3Al2CaSi10O27·3 H2O as reported by Lam et al. in 1994. Based on chemical analysis and crystal structure determination, there is considerable isomorphous replacement on the cation positions, leading to the crystal-chemical formula

Pb3(Al0.79Pb0.22)Σ1.01
[6]{
uB
, 4, 2∞
2} [Ca1.02
[6](Al0.81Fe0.06Si0.14)Σ1.01[4]Si10.00
[4]O27(H2O)3]·H2O.

With regard to crystal structure, that described by Lam et al. is found to be essentially correct, except for an additional H2O molecule per formula unit, whereas the structure suggested by Penna & Giese in 1968 and by Hesse & Liebau in 1992 and 1993 is incorrect. The wickenburgite structure contains silicate double-layers in which one out of twelve [(Al, Si)O4] tetrahedra is replaced by an [O3Ca(H2O)3] octahedron. Adjacent double layers are held together by Al3+ and Pb2+ cations that are octahedrally and irregularly eight-fold coordinated, respectively. The fourth H2O molecule per formula unit occupies a small cavity which is formed by six oxygen atoms from two adjacent double layers and three interlayer lead ions, thus shielding the repulsive forces between the lone-pair electrons of the latter. Minor but varying amounts of adhering, non-crystalline water is reversibly lost upon heating below 100°C. The cavity water is steadily and irreversibly lost between approximately 100 and 550°C (at a heating rate of 10°C per minute). Before all cavity water has been driven out, water coordinating the Ca2+ ions begins to escape. This dehydration process is accompanied by an approximately 4.4 percent reduction of the unit-cell volume without substantial disruption of the structure. At 740 °C the dehydration is not yet complete. The structure of wickenburgite is related to that of jagoite which contains both silicate single- and double-layers. In the double-layers of wickenburgite one out of twelve [(Al, Si)O4] tetrahedra is replaced by an [O3Ca(H2O)3] octahedron whereas in jagoite within the double-layers two out of twelve [(Fe, Si)O4] tetrahedra are replaced by [PbO3] pyramids.
Structure characterization of molecular complexes for non-linear optical materials I. X-ray analysis and AM1 calculations of 1 : 1 complexes of 8-hydroxiquinoline (1) and isonicotinamide (2) with 2,4,6-trinitrophenol
Authors: Carvalho C. C. , Camargo A. J. , Teijido Maurício Vega , Isolani P. C. , Vicentini G. , Zukerman-Schpector Julio
Published: December 2003

C6H2N3O7–·C9H8NO+(1), Mr = 374.27,P21/c,a= 8.2606(9),b= 9.2574(9),c= 19.906(2) Å,β= 91.441(8)°,Z= 4,R1= 0.0405. C6H2N3O7–·C6H7N2O+, (2), Mr = 351.24,P21/n,a= 14.3064(6),b= 7.4451(7),c= 14.7209(7) Å,β= 116.626(3)°,Z= 4,R1= 0.0385. The packing units in both compounds consist of hydrogen bonded cation-anion pairs. The basic first and second-level graph set analysis are given. The (hyper)polarizabilities have been calculated for the crystallographic and optimized molecules, by the semi-empirical quantum method AM1.
The twinned and disordered crystal structure of tetrakis(triphenylphosphine)silver(I)bis(trifluoroacetato)triphenylstannate(IV)
Authors: Ng Seik Weng , Rae A. David
Published: December 2003

The crystal structure of tetrakis(triphenyl-phosphine)silver(I)bis(trifluoroacetato)triphenylstannate(IV), [(C6H5)3P]4Ag (C6H5)3Sn(O2CCF3)2 [R3: a = 16.238(1), c = 52.354(3) Å], consists of discrete four-coordinate te trahedral cations and five-coordinate trans-C3SnO2 trigonal bipramidal anions. The asymmetric unit consists of a third of each of two cations and two anions. The structure is a 0.675(3): 0.325 twin of a 0.783(1): 0.217 disorder of an R3 structure that uses a 2-fold rotation operation of R32 for the twinning and the disorder. The structure is refined on 234 variables and 6276 reflections with I > 3σ(I) to R
F = 0.053.
Theoretical explanation of the octahedral distortion in FeF2and MgF2
Authors: Riss Alexander , Blaha Peter , Schwarz Karlheinz , Zemann Josef
Published: December 2003

The equilibrium geometries of rutile type FeF2and MgF2are determined using precise density functional theory calculations that lead to good agreement with experimental data. The strong deviation from the “ideal” octahedral geometry in FeF2comes from the Fe2+ion with thed6configuration in the high-spin state, which would require a singly occupied spin-downdorbital. The stability can only be understood by going beyond the first coordination shell considering direct Fe–Fe interactions mainly along thec-axis. The orbital population of the various Fe-dorbitals is analyzed using constarint distortions between the ideal and the equilibrium structure. Above a critical Fe–Fe distance of about 3.15 Å the population numbers change drastically, a single Fe-dspin down orbital becomes occupied and the system can relax to an insulating state. In MgF2no suchd-orbitals are present and thus the distortions are much smaller.
Rational approximants to 5, 8 and 7-fold two-dimensional tilings
Authors: Subramaniam Anandh , Ramakrishnan Krishnamurthy
Published: December 2003

The strip projection method is used to generate rational approximants to Penrose, octagonal and 7-fold tilings. Two types of approximants to the Penrose tiling are considered, wherein the basis vectors of the approximants are either orthogonal or are 72° apart. Various types of approximants including those with partially retained quasiperiodicity are generated and the pseudosymmetries arising therein analyzed. A simplified approach based on uniform distortions of perpendicular space is put forth for the analyses.
The cubic limiting complexes of the tetragonal lattice complexes
Authors: Koch Elke , Fischer Werner
Published: December 2003

For all tetragonal lattice complexes the limiting complexes with cubic characteristic space-group type have been derived. These limiting complexes are caused by a specialization of the axial ratioc/a. However, they may require in addition special coordinate parameters.The limiting complexes have been determined with the aid of group-subgroup relationships. In order to check the material, the occurrence of cubic sphere packings within tetragonal lattice complexes was used. The results are presented in four separate tables referring to the 4 invariant, the 24 univariant, the 38 bivariant and the 48 trivariant tetragonal lattice complexes.
The crystal structures of the potassium hydrogen monofluorophosphates, KHPO3F and K3[H(PO3F)2], and the α modification of RbHPO3F
Authors: Prescott Hillary A. , Troyanov Sergej I. , Kemnitz Erhard
Published: December 2003

Three new hydrogen monofluorophosphates, KHPO3F (I), K3[H(PO3F)2] (II), and α-RbHPO3F (III), were crystallographically characterized with single crystal X-ray analysis at 180 K. The compound I is monoclinic, space group P21 with a = 7.273(1), b = 14.086(3), c = 7.655(2) Å, β = 90.13(3), Z = 8, and R
1 and wR
2 factors of 0.0214 and 0.0395, respectively. II crystallizes in the monoclinic space group C2/c with a = 7.973(3), b = 11.635(4), c = 9.688(4) Å, β = 113.52(4), Z = 4, and R
1 and wR
2 factors of 0.0581 and 0.1615, respectively. III is monoclinic with the P21/n space group, a = 7.465(2), b = 15.551(8), c = 7.563(4) Å, β = 105.38(5), Z = 8, and R
1 and wR
2 factors of 0.0365 and 0.0694, respectively. I and III include O–H···O hydrogen bonding between the HPO3F tetrahedra to form branched spiral chains (I) or tetramers (III), respectively. In the structure of II, dimeric units are formed by a symmetrically disordered hydrogen bond between the PO3F tetrahedra. Both O and F atoms participate in cation coordination in all three structures, whereas only O atoms are involved in hydrogen bonding.
Electron crystallography of zeolites. 3. Calcined MCM-22 and MCM-49, a case of subtle differences
Authors: Dorset Douglas L.
Published: December 2003

Single crystal electron diffraction intensity data, analyzed by direct methods for determining crystallographic phases, have been employed to seek differences between the crystal structures of calcined MCM-22 and MCM-49. A direct comparison of hk0 intensity data indicates such a difference and this is justified further when the respective structural models are refined. The MCM-22 data agree well with the ITQ-1 Si-framework model, but without adding the extraneous interstitial atoms imposed in an earlier powder X-ray diffraction determination. The T-sites in MCM-49 are placed similarly to the ones in MCM-22 but Fourier refinement indicates the presence of an oxygen site not seen for MCM-22. Also one of the oxygen positions found in MCM-22 is not observed in the MCM-49 potential maps.
Crystal structures, order-disorder transition and twinning of the Jahn-Teller system (NO)2VCl6
Authors: Henke Henning
Published: December 2003

As in the case of (NO)2TiCl6 the octahedral-shaped crystals of dinitrosonium hexachlorovanadate(IV) are tetragonal at room temperature with space group P4/mnc and Z = 2. An X-ray structure determination at 248 K yields lattice parameters of a = 667.8(1) and c = 1023.8(1) pm, V–Cl distances for the ‘octahedral’ VCl6
2- ion of slightly different length [2 × 233.2(1), 4 × 229.4(1) pm], and a fourfold orientational disorder for the species NO+. The phase change at T
c = 236.5 ± 0.2 K is very sharp and clearly 1st order leading to a monoclinic unit cell with a = 657.1(3), b = 662.6(2), c = 1027.5(2) pm, and β = 91.82(1)° at T = 156 K in space group P21/n with Z = 2. As expected for vanadium in the oxidation state +4 the paramagnetism of the black compound measured above and below T
c confirms the spin-only value for a d1 system. The compressive distortion of the VCl6
2- units to approximate D
4h symmetry [2 × 234.3(1), 2 × 233.7(1), 2 × 224.1(1) pm at 156 K] favours the ordering process of the NO+ cations and vice versa. For the ordered NO+ the atomic distance is 107.0(3) pm. Repetition of the structure analysis at 231 K demonstrates that the static manifestation of the Jahn-Teller effect is coupled to the tilt of the VCl6
2- groups. In accordance with the symmetry reduction in formally two steps of type t2, the formation of quadruplet domains is observed, usually arranged around [001] as the common axis giving a fourfold rotation twin with c
tetr parallel c
mon and a
mon slightly inclined against the tetragonal a–b plane. If the crystal is clamped along c the twin law changes to the corresponding reflection twin (001).
Structural and physical properties of bis(guanidinium) X bis(nitrilotriacetate) hydrate, (C[NH2]3)2X(N[CH2COO]3)2·H2O (X = Zr, Sn, Hf) and bis(methylammonium) X bis(nitrilotriacetate dihydrate, (CH3NH3)2X(N[CH2COO]3)2·2 H2O (X = Sn, Zr)
Authors: Haussühl E. , Haussühl S. , Tillmanns E.
Published: December 2003

Single crystals of bis(guanidinium) tin bis(nitrilotriacetate) hydrate (GuSN) and bis(methylammonium) tin bis(nitrilotriacetate) dihydrate (MetamSN) having optical quality and dimensions up to 15 × 15 × 20 mm were grown from aqueous solutions. The isotypy with the corresponding zirconium and hafnium compounds (GuZN, GuHN, and MetamZN, respectively)) was proved by X-ray structure analyses (GuSN: space group Ccc21, a
1 = 11.338 Å, a
2 = 20.285 Å, a
3 = 10.178 Å, Z = 4, density 1.796 g cm-3; MetamSN: space group P212121, a
1 = 9.851 Å, a
2 = 14.164 Å, a
3 = 15.548 Å, Z = 4, density 1.821 g cm-3). Distinct differences in the dimensions of the tin bis(nitrilotriacetate) and zirconium bis(nitrilotriacetate) anions could be derived from structural features. The molecular volume of the latter is about 6 Å3 larger than that of the tin complex. Along one direction perpendicular to the twofold or quasi-twofold axis the diameter of the tin complex is about 0.18 Å shorter. Thermal expansion, dielectric, piezoelectric, elastic, thermoelastic and piezo elastic properties of corresponding tin, zirconium and hafnium compounds are quite similar. The small differences in the dimensions of the anions, however, are clearly reflected in the elastic longitudinal stiffnesses. The earlier described phase transitions in GuZN exist also in GuSN as confirmed by X-ray analysis at 100 K. The temperature of the transition region II is shifted to lower temperatures by about 4 and 6 K, if Zr is substituted by Sn and Hf, respectively. All anomalous phenomena observed during the transition in GuZN and GuHN are also found in GuSN.
Dichloro[(E)-2-chloro-1-vinyl-cyclohexanol](4-methoxy phenyl)Te(IV). A case of conformational polymorphism
Authors: Teijido Maurício Vega , Zukerman-Schpector Julio , Camillo Robinson Luis , Caracelli Ignez , Stefani Hélio Alexandre , Chieffi André , Comasseto João Valdir
Published: December 2003

C15Cl3H19O2Te, Mr
= 465.25, (1), P21/a, a = 9.8303(9), b = 17.492(2), c = 10.911(1) Å, β = 108.521(8)°, Z = 4, R
1 = 0.0274. (2), P21/c, a = 8.2661(9), b = 22.863(2), c = 9.828(1) Å, β = 108.894(8)°, Z = 4, R
1 = 0.0379. In both compounds, the primary geometry of the TeIV atom is a pseudo-trigonal-bipyramidal arrangement with two halide atoms in apical positions and a lone pair of electrons and C atoms in the equatorial plane. In (1), the TeIV atom is involved in an intermolecular secondary interaction resulting in the self-assembly of a chain-like supramolecular array. In (2), molecules are linked in centrosymmetric dimers through Cl···H–O interactions.
Plane groups – from basic to advanced crystallographic concepts
Authors: Stróż K.
Published: December 2003

The plane groups are rarely discussed in the crystallography courses and the didactic role of the plane groups for teaching symmetry is rather underestimated. Most crystallographic concepts known from 3-dimensional space group descriptions concern also these 2-dimensional groups and can be easier illustrated. Symmetry of atomic layers as well as symmetry of mosaics, lattice designs, symmetry of electron diffraction patterns or any pattern with two-dimensional periodicity can be characterised on a unique basis. Such a pattern can be generated by decorating the points of a crystallographic orbit by different graphical objects. The orbits are visualised as “crystallographic mosaics” (by connection of the closest points of the orbit), they can be characterised by Shubnikov or Laves nets and there always exists a number (circle packing density) that is related to a given orbit. The paper and a didactic computer program presented in it give some ideas and framework for the plane symmetry experiments: from finding the isometries on the generated patterns to identifying the non-characteristic orbits. It is also shown that the contour map of a circle packing density is a good frame for locating symmetry elements, asymmetric units or points with higher plane symmetry into a unit cell. The applied complex approach to the orbit characterisation will narrow the gap existing between concepts used by practising and theoretical crystallographers and mathematicians interested in tessellations.
Approach to a social stranger is associated with low central nervous system serotonergic responsivity in female cynomolgus monkeys (Macaca fascicularis)
Authors: Manuck Stephen B. , Kaplan Jay R. , Rymeski Beth A. , Fairbanks Lynn A. , Wilson Mark E.
Published: December 2003

It is widely hypothesized that individual differences in central nervous system (CNS) serotonergic activity underlie dimensional variation in “impulsive” vs. “inhibited” social behavior in both humans and nonhuman primates. To assess relative impulsivity in a social context, a behavioral challenge involving animals' exposure to a social stranger (termed the “Intruder Challenge”) was recently validated in adolescent and adult male vervet monkeys (Cercopithecus aethiops sabaeus). Among these animals, monkeys that quickly approached the intruder were found to have lower cerebrospinal fluid (CSF) concentrations of the serotonin (5‐HT) metabolite, 5‐hydroxyindoleacetic acid, than less impulsive animals. In the present study we extended these observations to determine whether approach to a social stranger, as operationalized by the Intruder Challenge, is similarly associated with diminished CNS serotonergic function in female cynomolgus monkeys (Macaca fascicularis). Study animals were 25 adult monkeys that had been housed for 2 years in stable social groups. In each animal, the rise in plasma prolactin concentration induced by acute administration of the 5‐HT agonist, fenfluramine, was used to assess “net” central serotonergic responsivity. When exposed later to an unfamiliar female of the same species in a catch‐cage placed for 20 min within the subjects' home enclosure, monkeys that approached to within 1 m of the intruder (median latency to approach=3 min) were found to have significantly smaller prolactin responses to fenfluramine (diminished serotonergic responsivity) compared to “inhibited” animals that failed to approach the intruder (t=2.9, df=23, P<0.009; rpb=–0.51). Neither approach behavior nor the animals' fenfluramine‐induced prolactin responses covaried significantly with nondirected expressions of arousal (or anxiety) or with aggressive behaviors exhibited during testing. We conclude that in female cynomolgus monkeys, social impulsivity (vs. inhibition) correlates inversely with individual differences in CNS serotonergic activity, as assessed by neuroendocrine challenge. Am. J. Primatol. 61:187–194, 2003. © 2003 Wiley‐Liss, Inc.
Systematics and evolution of the jacchus group of marmosets (Platyrrhini)
Authors: Marroig Gabriel , Cropp Susan , Cheverud James M.
Published: December 2003

Interspecific differentiation and geographic variation patterns in 39 skull traits of eastern Brazilian marmosets are analyzed. EasternCallithrixtaxa are distinct morphologically, and no evidence of intergradation among taxa is observed. Instead, there are sharp, stepped morphological boundaries among taxa, consistent with species‐level distinction. The morphological similarity cluster diagram obtained from Mahalanobis distances is different from available molecular trees, and the general picture emerging is that the easternCallithrixtaxa should be considered as good species arising recently in South American history. In particular,C. kuhliiis morphologically distinct from other marmoset taxa, includingC. geoffroyiandC. penicillata, which were previously hypothesized to be the parental populations that formedC. kuhliiby hybridization. Furthermore,C. kuhliipopulations from southeastern Bahia do not overlap morphologically with anyC. penicillatapopulation, including the upper São Francisco River populations that display skin colors and pelage patterns to some extent similar to true Kuhli's marmosets. There is a negative, though insignificant, correlation between the morphological distance matrix and a Mahalanobis distance matrix estimated from nine climatic variables, a pattern opposite to that expected under a parapatric speciation model. This result, together with the lack of clinal variation in skull traits, suggests that an allopatric model of speciation might best explain eastern marmoset diversification. Am J Phys Anthropol 2003. © 2002 Wiley‐Liss, Inc.
Patterns of phenotypic covariation and correlation in modern humans as viewed from morphological integration
Authors: González‐José Rolando , Van Der Molen Silvina , González‐Pérez Emili , Hernández Miquel
Published: December 2003

Proportionality of phenotypic and genetic distance is of crucial importance to adequately focus on population history and structure, and it depends on the proportionality of genetic and phenotypic covariance. Constancy of phenotypic covariances is unlikely without constancy of genetic covariation if the latter is a substantial component of the former. If phenotypic patterns are found to be relatively stable, the most probable explanation is that genetic covariance matrices are also stable. Factors like morphological integration account for such stability. Morphological integration can be studied by analyzing the relationships among morphological traits. We present here a comparison of phenotypic correlation and covariance structure among worldwide human populations. Correlation and covariance matrices between 47 cranial traits were obtained for 28 populations, and compared with design matrices representing functional and developmental constraints. Among‐population differences in patterns of correlation and covariation were tested for association with matrices of genetic distances (obtained after an examination of 10 Alu‐insertions) and with Mahalanobis distances (computed after craniometrical traits). All matrix correlations were estimated by means of Mantel tests. Results indicate that correlation and covariance structure in our species is stable, and that among‐group correlation/covariance similarity is not related to genetic or phenotypic distance. Conversely, genetic and morphological distance matrices were highly correlated. Correlation and covariation patterns were largely associated with functional and developmental factors, which probably account for the stability of covariance patterns. Am J Phys Anthropol, 2003. © 2003 Wiley‐Liss, Inc.
Hominid cranial remains from upper pleistocene deposits at Aduma, Middle Awash, Ethiopia
Authors: Haile‐Selassie Y. , Asfaw B. , White T.D.
Published: December 2003

The Upper Pleistocene localities of Aduma and Bouri have yielded hominid fossils and extensive Middle Stone Age (MSA) archaeological assemblages. The vertebrate fossils recovered include parts of four hominid crania from Aduma and a complete right parietal from Bouri. Archaeological associations and radiometric techniques suggest an Upper Pleistocene age for these hominids. The more complete cranium from Aduma (ADU‐VP‐1/3) comprises most of the parietals, the occipital, and part of the frontal. This cranium is compared to late Middle and Upper Pleistocene hominid crania from Africa and the Middle East. The Aduma cranium shows a mosaic of cranial features shared with “premodern” and anatomically modern Homo sapiens. However, the posterior and lateral cranial dimensions, and most of its anatomy, are centered among modern humans and resemble specimens from Omo, Skhul, and Qafzeh. As a result, the Aduma and Bouri Upper Pleistocene hominids are assigned to anatomically modern Homo sapiens. Am J Phys Anthropol, 2003. © 2003 Wiley‐Liss, Inc.
Beyond ‘anti‐smacking’: challenging parental violence and coercion
Authors: Phillips Ben , Alderson Priscilla
Published: December 2003

The anti‐smacking lobby concentrates on persuading parents not to smack and persuading the government to prohibit smacking by law. There is much evidence that smacking children is unnecessary and dangerous, and yet smacking continues to be widely practised and accepted in Britain. Our literature review found two underlying reasons for this contradiction: beliefs that children are ‘human becomings’ rather than full human beings and support for ‘parents’ rights' over children's human rights. We suggest that the anti‐smacking lobby's important work will have limited effect until it tackles these two issues, and make comparisons with debates on domestic violence against women to illustrate our argument. Copyright © 2003 John Wiley & Sons, Ltd.
Critical assessment of information extraction systems in biology
Authors: Blaschke Christian , Hirschman Lynette , Yeh Alexander , Valencia Alfonso
Published: December 2003

An increasing number of groups are now working in the area of text mining, focusing on a wide range of problems and applying both statistical and linguistic approaches. However, it is not possible to compare the different approaches, because there are no common standards or evaluation criteria; in addition, the various groups are addressing different problems, often using private datasets. As a result, it is impossible to determine how well the existing systems perform, and particularly what performance level can be expected in real applications. This is similar to the situation in text processing in the late 1980s, prior to the Message Understanding Conferences (MUCs). With the introduction of a common evaluation and standardized evaluation metrics as part of these conferences, it became possible to compare approaches, to identify those techniques that did or did not work and to make progress. This progress has resulted in a common pipeline of processes and a set of shared tools available to the general research community. The field of biology is ripe for a similar experiment. Inspired by this example, the BioLINK group (Biological Literature, Information and Knowledge) is organizing a CASP‐like evaluation for the text data‐mining community applied to biology. The two main tasks specifically address two major bottlenecks for text mining in biology: (1) the correct detection of gene and protein names in text; and (2) the extraction of functional information related to proteins based on the GO classification system. For further information and participation details, see http://www.pdg.cnb.uam.es/BioLink/BioCreative.eval.html. Copyright © 2003 John Wiley & Sons, Ltd.
Superficial radiotherapy for patients with basal cell carcinoma
Authors: Zagrodnik Beate , Kempf Werner , Seifert Burkhardt , Müller Beatrix , Burg Günter , Urosevic Mirjana , Dummer Reinhard
Published: December 2003

BACKGROUND

The histologic subtype of a basal cell carcinoma (BCC) may be an important factor for the success of a certain treatment modality. In the current article, the authors report recurrence rates among patients with BCC after superficial radiotherapy as well as Bcl‐2 and p53 expression levels stratified by BCC subtype.

METHODS

The authors performed a retrospective study of 175 BCCs in 148 patients (64 female patients and 84 male patients; mean age, 69 years) who were treated with radiotherapy. According to their histologic patterns, BCCs were classified as nodular (n = 103), superficial (n = 25), and sclerosing (n = 47). In addition, six patients with metatypic BCC were reviewed. Bcl‐2 and p53 protein expression was examined on a tissue microarray of 60 BCC samples (18 nodular tumors, 12 superficial tumors, and 30 sclerosing tumors).

RESULTS

The estimated 5‐year recurrence rate for all patients with BCC was 15.8%: 8.2% for patients with the nodular subtype, 26.1% for patients with the superficial subtype, and 27.7% for patients with the sclerosing subtype (Kaplan–Meier analysis: P = 0.055). The median follow‐up was 48 months. The mean time to recurrence was 20 months, and 86.4% of all recurrences occurred within 3 years after treatment. No gender‐specific differences were observed. In addition, one of six metatypic BCCs recurred. Nuclear p53 immunoreactivity and low Bcl‐2 expression were significantly correlated with the sclerosing subtype. Overall, 61.5% of patients developed additional neoplasms during follow‐up (76 developed additional BCCs, 15 developed squamous cell carcinomas, and 6 developed Bowen disease).

CONCLUSIONS

The sclerosing subtype of BCC was a risk factor for recurrence after radiotherapy. In contrast, excellent results were achieved for patients with predominant nodular subtype. Nevertheless, radiotherapy may be the therapy of choice for patients with all BCC subtypes, depending on the individual patient's characteristics. Expression analyses confirmed that p53 and Bcl‐2 levels may be used as indicators for the aggressiveness of a BCC subtype. Due to the high incidence of additional skin malignancies, patients with BCC need careful follow‐up. Cancer 2003;98:2708–14. © 2003 American Cancer Society.
Free interferon‐α/β receptors in the circulation of patients with adenocarcinoma
Authors: Ambrus Julian L. , Dembinski Wlodzimierz , Ambrus Julian L. , Sykes Donald E. , Akhter Selina , Kulaylat Mahmoud N. , Islam Abul , Chadha Kailash C.
Published: December 2003

BACKGROUND

Many viral and neoplastic diseases are resistant to interferon‐α/β (IFN‐α/β) therapy or develop resistance during the course of IFN treatment. In patients with viral diseases, the authors identified four IFN inhibitors, of which the most important, most likely is a free IFN receptor of type 1 appearing in the circulation that captures and neutralizes IFN‐α/β.

METHODS

Ninety‐one cancer patients and 25 healthy individuals were studied. Free circulating IFN receptor‐α/β type 1 was studied. The patients were ages 35–75 years. The diagnoses were 24 cases of colon carcinoma, 7 cases of prostate carcinoma, 16 cases of breast carcinoma, 8 cases of ovarian carcinoma, 9 cases of uterine carcinoma, 5 cases of lung carcinoma, 3 cases of astrocytoma, 4 cases of transitional cell carcinoma of the bladder, 1 case of osteosarcoma, 3 cases of multiple myeloma, 4 cases of Hodgkin disease, 2 cases of non‐Hodgkin lymphoma, 3 cases of myelodysplastic syndrome, and 2 disseminated tumors of unknown origin.

RESULTS

All patients were found to have increased free IFN receptor‐α/β type 1 in the circulation, with the highest levels reported in patients with adenocarcinoma.

CONCLUSIONS

High IFN inhibitory activity in patients with cancer may be a significant factor in their increased susceptibility to progressive disease, infectious complications, and resistance to IFN therapy. Ongoing studies are being performed with the objective of overcoming this inhibitory activity. Cancer 2003;98:2730–3. © 2003 American Cancer Society.
Prostate carcinoma tissue proteomics for biomarker discovery
Authors: Zheng Yaxin , Xu Ye , Ye Bin , Lei Junyi , Weinstein Michael H. , O'Leary Michael P. , Richie Jerome P. , Mok Samuel C. , Liu Brian C.‐S.
Published: December 2003

BACKGROUND

The advent of the prostate‐specific antigen (PSA) test has had a profound impact on the diagnosis and treatment of prostate carcinoma. However, the use of PSA levels alone for screening for prostate carcinoma was compromised by the variations in the amount of PSA produced by the benign prostatic tissue specimens. Proteins were involved in various pathways that determine the behavior of a cell. Therefore, information regarding proteins may reveal drug targets and/or markers for early detection.

METHODS

The authors used surface‐enhanced laser desorption/ionization time‐of‐flight mass spectrometry to determine the protein profiles from fresh tissues of the prostate. Laser capture microdissection was performed to isolate pure populations of cells.

RESULTS

The authors identified a protein with an average m/Z of 24,782.56 ± 107.27 that was correlated with the presence of prostate carcinoma. Furthermore, using laser capture microdissection, they demonstrated that the origin of this protein, which the authors designated PCa‐24, was derived from the epithelial cells of the prostate. PCa‐24 expression was detected in 16 of 17 (94%) prostate carcinoma specimens but not in paired normal cells. In addition, this protein was not expressed in any of the 12 benign prostatic hyperplasia specimens that were assayed.

CONCLUSIONS

PCa‐24 may be useful a marker for prostate carcinoma. Cancer 2003;98:2576–82. © 2003 American Cancer Society.