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PubMed2003

Gamma-ray and neutron diffraction studies of CoF2: magnetostriction, electron density and magnetic moments.

Accurate structure factors up to sin theta/lambda = 1.6 A(-1) have been measured with 316.5 keV gamma-rays from CoF(2), both at room temperature and in the antiferromagnetic state at 10 K. The same crystal was used to collect extended time-of-flight neutron diffraction data in the two magnetic states, which allowed an accurate determination of the fluorine positional parameter. For room temperature, the standard structural parameters are reported. At 10 K, a complete charge-density study has been carried out. The total number of 3d electrons on Co is found to be 6.95 (3). The experimental populations of the d orbitals agree with expectation from crystal field theory. The fluorine valence region exhibits a strong dipolar deformation. Electronic properties at the bond critical points and integrated atomic properties are derived from the static model electron density, revealing the Co-F interactions as purely ionic. On magnetic ordering, a shift of the fluorine ions of 1.5 (4) x 10(-3) A is found which confirms a prediction from theory of optical birefringence. The effect of magnetostriction on the distortion of the ligand coordination octahedra is compared for the late members of the 3d transition-metal difluorides. From neutron powder diffraction, an ordered magnetic moment of 2.60 (4) mu(B) per cobalt ion is found. Despite the strong deviation from the ideal spin value of 3 mu(B), there is still an appreciable orbital contribution to the local magnetic moment.

Journal Article↗
PubMed1995

Zwitterionic nature of tenoxicam: crystal structures and thermal analyses of a polymorph of tenoxicam and a 1:1 tenoxicam:acetonitrile solvate.

The products of recrystallization of tenoxicam (4-hydroxy-2-methyl-N-2-pyridinyl-2H-thieno[2,3-e]-1,2-thiazine-3- carboxamide 1,1-dioxide) from ethanol and acetonitrile were investigated by thermogravimetric analysis, differential scanning calorimetry, and X-ray diffraction. Recrystallization from ethanol yielded a polymorph designated 1, and recrystallization from acetonitrile gave a solvate 2 with 1:1 stoichiometry. The structures of 1 and 2 were determined by single-crystal X-ray methods. Polymorph 1 is triclinic, space group P1, with Z = 4; solvate 2 is monoclinic, space group P2(1)/n, with Z = 4. In both crystal structures, the tenoxicam molecule exists in the zwitterionic form, adopting a planar conformation that is stabilized by two intramolecular hydrogen bonds (N(+)-H...O and N-H...O-). Tenoxicam molecules associate by N(+)-H...O and C-H...N hydrogen bonding in both crystal structures. Desolvation of 2 yields a polymorph of tenoxicam that is different from polymorph 1. A study of the kinetics of the desolvation of 2 by dynamic thermogravimetry yielded estimates of the activation energy in the range 69-72 kJ.mol-1. From a comparison of experimental and simulated X-ray powder diffraction patterns, neither 1 nor 2 undergoes a polymorphic transition upon grinding. X-ray patterns based on the single-crystal X-ray data for 1 and 2 are presented as reliable references for their identification.

Acetonitriles↗
PubMed2002

Assessment of amorphous content by microcalorimetry.

The amorphous content of model drugs was evaluated by isotherm microcalorimetry. Two model drugs were employed; lactose as a hydrophilic one and erythromycin as a hydrophobic one. When amorphous lactose was loaded in a sample cell with a water vial, a sharp exothermic peak due to the crystallization was observed. When a mixture of the amorphous and the crystalline forms was loaded, the peak area of the exothermic heat flow was proportional to the amorphous content. Quantification could be done with much higher accuracy than by the X-ray powder diffraction method reported in earlier literature. When erythromycin was used as a model drug, the crystallization was not completed by water but by organic solvents, which can dissolve erythromycin. The most adequate solvent for erythromycin was acetonitrile, of which the suitability was elucidated in terms of solubility and vapor pressure. This is the first report in which the role of the vapor pressure on crystallization behavior is discussed. The time needed to obtain the crystallization peak was controlled by mixing acetonitrile with water. The strategy to obtain the crystallization peak by microcalorimetry, which enables quantification of the amorphous content with high accuracy, is discussed.

Anti-Bacterial Agents↗
PubMed2000

Bulk modulus and high-pressure crystal structures of tetrakis(trimethylsilyl)methane C

The pressure dependence of the crystal structure of cubic tetrakis(trimethylsilyl)methane C[Si(CH3)3]4 (TC) (P < 16.0 GPa, T = 298 K) is reported using high-resolution angle-dispersive X-ray powder diffraction. The compound has crystal structures with the molecules in a cubic-close-packed (c.c.p.) arrangement. It shows three phase transitions in the measured pressure range. At ambient conditions, TC has space group Fm3m (Z = 4) with a = 12.8902 (2) A, V = 2141.8 (1) A3 (phase I). Between 0 and 0.13 GPa TC exhibits a first-order phase transition into a structure with space group Pa3 (phase II). A second first-order phase transition occurs between 0.2 and 0.28 GPa into a structure with space group P2(1)3 (phase III). Under non-hydrostatic pressure conditions (P > 10 GPa) a transformation is observed into a c.c.p. structure that is different from the face-centred-cubic structure at ambient conditions. A non-linear compression behaviour is observed, which could be described by a Vinet relation in the range 0.28-4.8 GPa. The extrapolated bulk modulus of the high-pressure phase III was determined to be K0 = 7.1 (8) GPa. The crystal structures in phase III are refined against X-ray powder data measured at several pressures between 0.49 and 4.8 GPa, and the molecules are found to be fully ordered. This is interpreted to result from steric interactions between neighbouring molecules, as shown by analysing the pressure dependence of intramolecular angles, torsion angles and intermolecular distances. Except for their cell dimensions, phases I, II and III are found to be isostructural to the corresponding phases at low temperatures.

Journal Article↗
PubMed1999

Crystal and molecular structures of 2-

The crystal and molecular structures of 2-[1-(2-aminoethyl)-2-imidazolidinylidene]-2-nitroacetonitrile [C(7)H(11)N(5)O(2); space group P2(1)/n; Z = 4; a = 7.4889 (8), b = 17.273 (2), c = 7.4073 (8) Å, beta = 111.937 (6) degrees ], (I), and 2,6-diamino-5-hydroxy-3-nitro-4H-pyrazolo[1,5-a]pyrimidin-7-one monohydrate [C(6)H(6)N(6)O(4).H(2)O; space group P2(1)/n; Z = 4; a = 17.576 (3), b = 10.900 (2), c = 4.6738 (6) Å, beta = 92.867 (8) degrees ], (II), have been determined from X-ray, synchrotron and neutron powder diffraction data using various methods. The structures were originally solved from Guinier photographs with a grid search procedure and the program MRIA using a priori information from NMR and mass spectra on the possible geometry of the molecules. Because the conformation of molecule (I) changed during the bond-restrained Rietveld refinement, solvent water was found in (II) and, moreover, as both Guinier patterns were corrupted by texture, high-resolution texture-free synchrotron data were collected at the BM16 beamline, ESRF, to confirm the original results. Using the set of |F|(2) values derived from the synchrotron patterns after full-pattern decomposition procedures, the structures of (I) and (II) were solved by direct methods via SHELXS96, SIRPOW.92 and POWSIM without any preliminary models of the molecules, and by Patterson search methods via DIRDIF96 and PATSEE with the use of rigid fragments from each of the molecules. The neutron patterns allowed (I) and (II) to be solved using the grid search procedure and correct initial models of the molecules including H atoms. The results obtained from powder patterns measured on different devices demonstrate the high level of reproducibility and reliability of various powder software and equipment, with a certain preference for synchrotron facilities.

Journal Article↗
PubMed2002

Preparation and characterization by morphological analysis of diclofenac/PEG 4000 granules obtained using three different techniques.

The steam granulation is a new wet granulation technique, which involves the use of steam water instead of traditional liquid water as granulation liquid. The aim of this work was to evaluate the possibility of using this new technique to prepare diclofenac-polyethylene glycol 4000 accelerated-release granules. Steam granules were prepared in a laboratory scale high-shear mixer, and their properties were then compared to those of granules, having the same composition, obtained by traditional granulation techniques (wet and melt granulation). The results showed that, selecting the proper process parameters, it was possible to obtain granules using all the three methods; however, the total process time was significantly shorter for steam granulation (30 min) in comparison to traditional wet granulation (70 min), due to the lower amount of used water. The morphological characterization of steam, water and melt granules, performed by scanning electron microscopy (SEM) and image analysis, revealed that steam granules had a more spherical shape and a larger surface area with respect to water and melt ones, suggesting a possible difference in dissolution behavior. Moreover, differential scanning calorimetry (DSC) and X-ray powder diffraction analysis evidenced the transformation of the drug from its originally crystalline form into the amorphous one. Finally, the in vitro dissolution tests showed an increased dissolution rate of the drug from the granules (in particular steam granules) in comparison to pure drug and physical mixture. In conclusion, the results of this study suggested that the steam granulation technique could be considered an interesting alternative to traditional wet granulation to improve the dissolution rate of diclofenac.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2005

High-throughput investigation and characterization of cobalt carboxy phosphonates.

High-throughput methods have been employed to study the system Co(2+)/(H(2)O(3)PCH(2))(2)NCH(2)C(6)H(4)COOH/NaOH in detail. The use of the phosphonocarboxylic acid (H(2)O(3)PCH(2))(2)NCH(2)C(6)H(4)COOH has led to several new cobalt carboxyaryl phosphonates under hydrothermal conditions. In addition to the effect of the pH of the starting mixture, the influence of the counterions of the cobalt salts on the product formation was investigated. Thus, reaction trends as well as fields of formation could be identified. Four new compounds Co(2)[(O(3)PCH(2))(2)NCH(2)C(6)H(4)COOH].H(2)O (1), Co[(O(3)PCH(2))(OCH)NCH(2)C(6)H(4)COOH].H(2)O (2), Co[H(2)(O(3)PCH(2))(2)NCH(2)C(6)H(4)COOH] (3), and [Co(2)(O(3)PCH(2))(2)NCH(2)C(6)H(4)COOH].3.5H(2)O (4) were obtained, and compounds 1 and 2 could be isolated as single crystals suitable for single-crystal X-ray diffraction. The counterions of the cobalt salts have an influence on the structure of the resulting compounds. This is due to the effect on the initial pH as well as the possibility of the counterions to take part in redox reactions. Compounds 1 and 4 are formed under more basic conditions, and the phosphonic acid group is fully deprotonated. The structure of 1 is a rare example of the family of inorganic-organic hybrid materials with iminobis(methylphosphonic acid) units wherein the nitrogen coordinates to the metal center. Compound 2 is the result of an in situ oxidation of one of the P-C bonds; the organic building unit is stabilized by complexation of the cobalt ion. On the basis of spectroscopic, thermogravimetric, elemental chemical analysis, and EDX-analysis data, compound 3 has been characterized as Co[H(2)(O(3)PCH(2))(2)NCH(2)C(6)H(4)COOH] and compound 4 as [Co(2)(O(3)PCH(2))(2)NCH(2)C(6)H(4)COOH].3.5H(2)O. X-ray powder diffraction and IR-spectroscopic studies show that thermal treatment of 4 leads to the title compound 1. This transformation is accompanied by a change of color from pink to deep blue.

Journal Article↗
PubMed2001

Crystal habit modifications of ibuprofen and their physicomechanical characteristics.

Ibuprofen was crystallized from methanol, ethanol, isopropanol, and hexane at similar conditions. Marked differences in crystal habit of the samples obtained from these solvents were observed. The samples crystallized from methanol and ethanol had a polyhedral crystal habit, while those from hexane were needlelike. Those from isopropanol were elongated crystals. X-ray powder diffraction (XPD) and diferential scanning calorimetry (DSC) studies confirmed that these samples were structurally similar, therefore, polymorphic modifications were ruled out. The results showed that crystal habit modification had a great influence on the mechanical properties (compressibility, flow rate, and bulk density) of ibuprofen crystals. Samples obtained from methanol and ethanol exhibited the highest bulk density and the best flow rate, while those from hexane showed the lowest bulk density and the worst flow rate. The samples obtained from ethanol exhibited the best compression force/hardness profiles, and those obtained from hexane produced the softest tablets.

Calorimetry, Differential Scanning↗
PubMed2004

Modeling and monitoring of polymorphic transformations during the drying phase of wet granulation.

PURPOSE: The purpose of this work was to monitor polymorphic transformations of glycine during the drying phase of a wet granulation and model the polymorphic conversions using a time-based reconciliation model. METHODS: Near-infrared spectroscopy (NIR) was used for quantitation of polymorphs, and X-ray powder diffraction (XRPD) was used for qualitative analysis of polymorphs. RESULTS: The data show that the faster the granulation was dried, the more kinetic trapping of the metastable alpha-glycine polymorph, as predicted by reconciliation of the time scales of both the drying rate and the rate of the solution-mediated conversion. CONCLUSIONS: By knowing basic properties of the drug substance (solubility of the polymorphic forms and the rate of the solution-mediated conversion), processing conditions, such as the drying rate, can be adjusted to anticipate and prevent potential polymorphic transformations.

Calibration↗
PubMed2000

Application of diffuse reflectance near-infrared spectroscopy for determination of crystallinity.

Studies were conducted to investigate the use of near-infrared spectroscopy (NIRS) for determining degree of crystallinity. Physical mixtures of amorphous/crystalline indomethacin and amorphous/crystalline sucrose were prepared over several composition ranges. Spectra were obtained on powder samples contained in glass vials using diffuse reflectance sampling. Parallel studies were conducted using X-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC) for comparison. NIRS standard curves were constructed by plotting crystalline weight percent against the ratio of responses at two wavelengths or by partial least squares regression. NIRS standard curves demonstrated higher coefficients of determination and lower standard errors than either XRPD or DSC. Validation standards confirmed the accuracy of NIRS over XRPD. Method error analysis demonstrated comparable accuracy for NIRS and XRPD, with NIRS showing slightly better precision in repeated crystallinity determinations for a 50% crystalline sucrose sample. Interpretive analysis of the NIRS spectra was performed using neutron scattering and polarized Raman spectroscopy data obtained from the literature. Results indicated that the NIRS differences between crystalline and amorphous sucrose may be attributed to the disruption of regular vibrational modes when crystalline sucrose is rendered amorphous.

Crystallization↗
PubMed1999

Development of a mathematical model for the water distribution in freeze-dried solids.

PURPOSE: Development of a mathematical model to provide information about the amount of water associated with a protein and an excipient in a lyophilized product. METHODS: The moisture content of the product and the mass fraction of each component were used to derive a model for the calculation of the mass of water associating with each component. The model was applied to lyophilized formulations of rhDNase containing various amounts of mannitol or lactose. The total water content was investigated by thermogravimetry, crystalline properties by X-ray powder diffraction and water uptake behaviour using a moisture microbalance system. RESULTS: Calculations based on the model suggest that in a lyophilized rhDNase-mannitol formulation where the sugar is crystalline, most of the water is taken up by the protein. However, in the lyophilized rhDNase-lactose formulation where the sugar is amorphous, water is taken up by both the sugar and protein to a comparative extent. At high relative humidities when the amorphous sugar undergoes crystallization, the model can accommodate such a change by allowing for the formation of an additional crystalline phase. CONCLUSIONS: The rhDNase-sugar formulations show excellent conformity to the model which provides quantitative information about the distribution of water in the lyophilized binary protein-excipient products.

Crystallography, X-Ray↗
PubMed1978

Quantitative crystallinity determinations for beta-lactam antibiotics by solution calorimetry: correlations with stability.

The solution calorimetry method is based on the observation that amorphous forms are normally significantly higher in energy than are crystalline forms. The utility and validity of the calorimetric method were investigated for cephalothin sodium, cefazolin sodium, cefamandole nafate, and cefamandole sodium. Amorphous, partially crystalline, and crystalline forms were prepared and characterized by X-ray diffraction (powder), by solution calorimetry, and, for cephalothin sodium, by the thermal decomposition rate at 50 degrees. Qualitatively, there was a good correlation between calorimetric crystallinity and the (less precise) crystallinity derived from X-ray data. The energy and structure of the amorphous state depend on the history of the sample; even samples of the same crystalline polymorph, containing no amorphous phase, may differ in energy. Thus, the absolute value of the crystallinity (X-ray or calorimetric) depends on the choice of amorphous and crystalline standards. The heat of solution is a precise (+/- 1%) and unambiguous measure of the relative crystallinity; and provided amorphous and crystalline standards are appropriately chosen, the calorimetric crystallinity correlates well with chemical stability.

Absorption↗
PubMed2003

Quantitative determination of crystallinity of alpha-lactose monohydrate by Near Infrared Spectroscopy (NIRS).

The purpose of this study was to determine quantitatively the crystallinity in crystalline/amorphous powder mixtures of lactose, to asses the capability of Near Infrared Spectroscopy (NIRS) for quantitative determination of crystallinity and to compare the accuracy of the NIRS method with that of conventional X-ray powder diffraction (XRPD). Amorphous lactose was prepared by spray drying. Samples with different crystallinity were prepared by physical mixing of 100% amorphous and 100% crystalline materials. The samples were characterized by XRPD and NIRS. Analysis was performed on the data sets by multiple linear regression (MLR). There is a close correlation between the predicted and the actual crystallinity of physical mixtures of crystalline and amorphous lactose, determined by NIRS (R(2)=0.9994). NIRS results were compared to the XRPD using the same sample sets. The correlation coefficients was 0.9981. The results showed that NIRS is an useful method for accurately determining low quantities of the crystalline lactose in a physical mixture. Therefore, NIRS can be used for the quantitative determination of crystallinity of materials during pharmaceutical procedures.

Crystallization↗
PubMed2004

The charge density of urea from synchrotron diffraction data.

The charge density of urea is studied using very high precision single-crystal synchrotron-radiation diffraction data collected at the Swiss-Norwegian Beam Lines at ESRF. An unprecedented resolution of 1.44 A(-1) in sin theta;/lambda is obtained at 123 K. The optimization of the experiment for charge-density studies is discussed. The high precision of the data allowed the refinement of a multipole model extending to hexadecapoles and quadrupoles on the heavy and H atoms, respectively, as well as a liberal treatment of radial functions. The topological properties of the resulting electron density are analysed and compared with earlier experimental results as well as with periodic Hartree-Fock calculations. The properties of the strongly polarized C-O bond agree with trends derived from previous experimental results while the ab initio calculations differ significantly. The results indicate that the description of the C-O bond requires more flexible basis sets in the theoretical calculations. The calculated integrated atomic charges are much larger than the observed ones. It is suggested that the present experimental results provide new target values for validation of future ab initio calculations. The molecular dipole moment derived from the integrated atomic properties is the same as the one obtained from the multipole model even though the individual atomic contributions differ. Comparison with literature data for urea in solution and the gas phase yields a dipole enhancement in the solid of about 1.5 D. The thermal expansion of urea is determined using synchrotron powder diffraction data. With decreasing temperature, an increasing anisotropic strain is observed.

Journal Article↗
PubMed1989

Preliminary studies of the development of a direct compression cellulose excipient from bagasse.

Bagasse is an unused by-product in cane sugar manufacture. Bagasse from sugar cane manually harvested in Indonesia was transformed to pulp by mechanical means and repeated autoclaving in 1.4% NaOH. It was then subjected to cycles of bleaching with hypochlorite and acid hydrolysis with 2.5 M HCl to produce 'microcrystalline' cellulose (MCC). Extraction of waxes by petroleum ether was necessary in order to improve the disintegration properties of tablets made from this material, DICEB III. When the bagasse-derived cellulose was reconstituted by recombining different proportions of selected sieve cuts to have a similar sieve size distribution as the commercially available MCC, Avicel PH102, it was found that the latter and DICEB III also had similar crystallinity as measured by X-ray powder diffraction (degree of crystallinity 2.8 +/- 0.2). The crystallinity and flow index were also relatively insensitive to most of the changes in the manufacturing procedure, indicating that the production process was quite robust. Directly compressed tablets were made containing 50 mg of caffeine and 500 mg of either Avicel PH102 or DICEB III to approximately the same hardness (11.6 +/- 1.1 and 13.7 +/- 0.5 kPa, respectively). They displayed similar satisfactory disintegration and dissolution behavior. However, DICEB III required greater compaction pressures than Avicel PH102, perhaps because the former was not spray dried to give spherical agglomerates of particles of uniform size as the commercial product. Rather, DICEB III consisted mainly of single irregular particles. Further work is required to improve the new excipient and to explore if the bagasse from mechanically harvested sugar cane (often contaminated by soil) could also be used for production of MCC.

Caffeine↗
PubMed2005

Application of powder X-ray diffraction in studying the compaction behavior of bulk pharmaceutical powders.

This study investigates the effects of crystal lattice deformation on the powder X-ray diffraction (PXRD) patterns of compressed polycrystalline specimen (compacts/tablets) made from molecular, crystalline powders. The displacement of molecules and the corresponding adjustment of interplanar distances (d-spacings) between diffracting planes of PNU-288034 and PNU-177553, which have crystal habits with a high aspect ratio favoring preferred orientation during tableting, are demonstrated by shifts in the diffracted peak positions. The direction of shift in diffracted peak positions suggests a reduction of interplanar d-spacing in the crystals of PNU-288034 and PNU-177553 following compaction. There is also a general reduction of peak intensities following compression at the different compressive loads. The lattice strain representing the reduction in d-spacing is proportional to the original d-spacing of the uncompressed sample suggesting that, as with systems that obey a simple Hooke's law relationship, the further apart the planes of atoms/molecules within the lattice are, the easier it is for them to approach each other under compressive stresses. For a third model compound comprising more equant-shaped crystals of PNU-141659, the shift in diffracted peak positions are consistent with an expansion of lattice spacing after compression. This apparent anomaly is supported by the PXRD studies of the bulk powder consisting of fractured crystals where also, the shift in peak position suggests expansion of the lattice planes. Thus the crystals of PNU-141659 may be fracturing under the compressive loads used to produce the compacts. Additional studies are underway to relate the PXRD observations with the bulk tableting properties of these model compounds.

Compressive Strength↗
PubMed2004

Synthesis and characterization of a new bisphosphonic acid and several metal hybrids derivatives.

Commercial bis-(4-bromophenyl)-ether, [BrC(6)H(4)](2)-O, has been used to prepare 4-[4'-(diethoxyphosphoryl)phenoxy]phenyl-phosphonic acid diethyl ester, [(CH(3)CH(2))(2)O(3)P-C(6)H(4)](2)-O, (I) following a slight modification of the Michaelis-Arbuzov reaction. The acid hydrolysis of I gave 4-(4'-phosphonophenoxy)phenyl phosphonic acid, [H(2)O(3)P-C(6)H(4)](2)-O (II), and both compounds have been characterized by (1)H NMR and (13)C NMR. The crystal structure of II has been determined by single-crystal X-ray diffraction. II crystallizes in an orthorhombic unit cell, space group Pbcn, with a = 7.822(3) A, b = 5.821(2) A, c = 28.982(9) A, and V = 1319.7(7) A(3). The final R factor was R1 = 0.0614. The structure is layered, being held together through a hydrogen bonding network. II has been used as precursor in the syntheses of new metal (Mn, Fe, Co, Ni, Cu, and Zn) bisphosphonates. The syntheses were carried out using a fixed metal/bisphosphonic acid molar ratio of 2.1:1 and the influence of the pH in the reactions has been studied. Nine new compounds have been isolated: Mn(2)(O(3)PC(6)H(4)OC(6)H(4)PO(3)).1.5H(2)O (III), Mn(5)(OH)(2)(O(3)PC(6)H(4)OC(6)H(4)PO(3))(2).2H(2)O (IV), Fe(HO(3)PC(6)H(4)OC(6)H(4)PO(3)).0.5H(2)O (V), Co(2)(O(3)PC(6)H(4)OC(6)H(4)PO(3)).2H(2)O (VI), Ni(2)(O(3)PC(6)H(4)OC(6)H(4)PO(3)).3H(2)O (VII), Ni(2)(O(3)PC(6)H(4)OC(6)H(4)PO(3)).2H(2)O (VIII), Cu(2)(O(3)PC(6)H(4)OC(6)H(4)PO(3)) (IX), Zn(2)(O(3)PC(6)H(4)OC(6)H(4)PO(3)) (X), and Zn(HO(3)PC(6)H(4)OC(6)H(4)PO(3)H) (XI). Compound IX crystallizes in an orthorhombic unit cell, space group Pbcn, and unit cell parameters a = 8.1012(5) A, b = 5.3109(3) A, c = 29.2595(5) A, and V = 1258.8(1) A(3). Its structure has been solved by ab initio powder diffraction and refined by the Rietveld method to R(F) = 0.042. IX has a pillared layer framework with highly distorted CuO(5) groups sharing edges to give isolated dimers. XI was indexed in a monoclinic unit cell, space group P112(1), with parameters a = 9.4991(9) A, b = 5.0445(5) A, c = 29.131(2) A, gamma = 91.945(7) degrees, and V = 1395.1(3) A(3). Its structure has been refined by the Rietveld method, R(F) = 0.054, since it is isostructural with the known compound, Zn[HO(3)P(C(6)H(4))(2)PO(3)H]. All solids were also characterized by thermal analysis and IR and UV-Vis spectroscopies.

Journal Article↗
PubMed2000

Elastic and physicochemical relationships within cortical bone.

The purpose of this study was to examine the relationships that exist between the elastic properties and the physicochemical properties of cortical bone in two groups of experimental animals. The animal model was the immature mutant dwarf rat, and the groups consisted of rats treated and not treated with recombinant human growth hormone (rhGH). The objective was to establish and broaden the quantifiable link between the three-dimensional form and function of bone beyond the typical unidirectional measures. This study was based on previously reported work that refined the ultrasonic elasticity technique for use with small specimens (<1.0 mm) and determined that the administration of rhGH can counter the degenerative effects produced by hormone-suppressed downregulation on the elastic and physicochemical characteristics of cortical bone. Ultrasonic wave propagation and density measurements were used previously to determine the three-dimensional (orthotropic) material properties of rat femoral cortical bone. X-ray powder diffraction, microscopic, morphometric, and biochemical analysis techniques have been used to describe physicochemical properties, including mineral crystal size, cortical porosity, mineral and nonmineral content, and microstructural characteristics. In this study, mathematical relationships between the local physicochemical (independent variable) and elastic (dependent variable) properties were formulated via linear and nonlinear regression analyses. In general, apparent density was found to have the highest level of correlation with most of the longitudinal and shear moduli (R(2) = 0.300 to 0.800). Concomitantly, mineral crystal width and cortical porosity offered the best correlations with the Poisson's ratios (R(2) up to 0.600). Wilcoxon t tests verified a significant decrease in the elastic properties in dwarf rat cortical bone after rhGH treatments (p < 0.05). Physicochemical measures of bone quality (density, crystal size) generally decreased while measures of bone quantity (cortical area, moments of inertia) generally increased (p < 0.05) after rhGH treatments. Some mineral and nonmineral properties were unchanged. This study presents a quantifiable link between cortical bone elasticity and its composite construction as measured across two dramatically different experimental groups.

Animals↗