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PubMed2000

Effect of particle size, air flow and inhaler device on the aerosolisation of disodium cromoglycate powders.

Recently, the dispersion of mannitol powders has demonstrated the importance of particle size, air flow and inhaler device (Chew and Chan, 1999). The aim of the present study is to extend our investigation to a different compound, disodium cromoglycate (DSCG) powders. Solid state characteristics of the powders were assessed by particle sizing, scanning electron microscopy, X-ray powder diffraction, moisture content, particle density determination and freeze fracture. The aerosol behaviour of the powders was studied by dispersion using Rotahaler(R) and Dinkihaler(R), connected to a four-stage liquid impinger operating at 30-120 l/min. Three amorphous powders with a mass median diameter (MMD) of 2.3, 3.7, 5.2 microm and a similar polydispersity were prepared. The particles were nearly spherical with a particle density of 1.6 g/cm(3) and moisture content of 6.6 wt.%. Using Rotahaler(R), the maximum fine particle fraction (FPF(max)) for all three powders was only 15 wt.%, attained at the highest flow of 120 l/min. Using Dinkihaler(R), the FPF(max) was two to four times higher, being 36 and 29 wt.% for the 2.3 and 3.7 microm powder, respectively, at 60 l/min; and 18 wt.% for the 5.2 microm powder at 120 l/min. Hence, the study shows that the FPF in the DSCG powder aerosols was determined by the interaction of the particle size, air flow and inhaler design. The attribution of the amorphous nature and the different physico-chemical properties of the powder may explain the incomplete and low dispersibility of DSCG.

Aerosols↗
PubMed1990

The effect of moisture content on the compression properties of maltodextrins.

The effect of moisture content on the compression properties of maltodextrin powders obtained by different degrees of hydrolysis (depolymerization) of corn starch has been studied using the yield pressure determined from the Heckel plot and the compact tensile strength measured by the diametrical compression method. An increase in the moisture content of the powder reduced the yield pressure and improved the densification for all five maltodextrins evaluated. At the same moisture level, the extent of densification which occurred during compaction was greater for maltodextrins with a lower degree of polymerization. Compacts produced by maltodextrins with a lower degree of polymerization also exhibited a greater tensile strength for a given pressure at a moisture content below 8.0%. However, further increase in moisture content resulted in a decrease in compact tensile strength for maltodextrins having a lower degree of polymerization. Despite the significant difference in compression behaviour, the five maltodextrins did not show noticeable differences in crystallinity as revealed by their x-ray powder diffraction pattern.

Crystallization↗
PubMed1998

New high- and low-temperature apparatus for synchrotron polycrystalline X-ray diffraction.

A high-temperature furnace with an induction heater coil and a cryogenic system based on closed-cycle refrigeration have been assembled to enhance the non-ambient powder diffraction facilities at the Synchrotron Radiation Source, Daresbury Laboratory. The commissioning of the high- and low-temperature devices on the high-resolution powder diffractometer of Station 2.3 is described. The combined temperature range provided by the furnace/cryostat is 10-1500 K. Results from Fe and NH(4)Br powder samples are presented to demonstrate the operation of the apparatus. The developments presented in this paper are applicable to a wide range of other experiments and diffraction geometries.

Journal Article↗
PubMed1996

X-ray diffraction studies of oxidized high-palladium alloys.

OBJECTIVE: The purpose of this study was to use x-ray diffraction (XRD) to obtain new information about the oxide layers on four representative oxidized high-palladium alloys. METHODS: Cast specimens of two Pd-Cu-Ga alloys and two Pd-Ga alloys, with both polished and etched surfaces and air-abraded surfaces, were subjected to oxidation procedures recommended by the manufacturers. The specimens were analyzed by x-ray diffraction using CuK alpha radiation, and the peaks were compared to appropriate Joint Committee on Powder Diffraction Standards (JCPDS). RESULTS: The surface preparation procedure had a profound effect on the phases present in the oxide layers. For the specimens that had been polished and etched, CuGa2O4 and beta-Ga2O3 were detected on the 79Pd-10Cu-9Ga-2Au alloy, whereas SnO2 and CuGa2O4 were detected on the 76Pd-10Cu-5.5Ga-6Sn-2Au alloy. The oxide layers on both Pd-Cu-Ga alloys contained Cu2O1 and the oxide layer on the 76Pd-10Cu-5.5Ga-6Sn-2Au alloy may contain beta-Ga2O3. The principal phase in the oxide layers on both Pd-Ga alloys that had been polished and etched was ln2O3, which exhibited extreme preferred orientation. No other phase was detected in the oxide layer on the 85Pd-10Ga-2Au-1Ag-1 ln alloy, whereas beta-Ga2O3 was found in the oxide layer on the 75Pd-6Ga-6Au-6Ag-6.5ln alloy. For the air-abraded specimens, beta-Ga2O2 was not present in the oxide layers on the Pd-Cu-Ga alloys, and beta-Ga2O3 was the major phase in the oxide layers on the Pd-Ga alloys. Palladium oxide(s) in varying amounts were detected for both surface preparations of the Pd-Cu-Ga alloys and for the air-abraded Pd-Ga alloys. Except for the 76Pd-10Cu-5.5Ga-6Sn-2Au alloy, the oxide layer caused minimal change in the lattice parameter of the palladium solid solution compared to that for the as-cast alloy. SIGNIFICANCE: Knowledge of the phases found in the oxide layers on these high-palladium alloys is of fundamental importance for interpreting differences in the adherence of dental porcelain to the metal substrates under static and dynamic conditions, and may provide guidance in the development of new high-palladium alloys with improved metal-ceramic bonding.

Copper↗
PubMed2003

Highly conducting crystals based on single-component gold complexes with extended-TTF dithiolate ligands.

Highly conducting crystals based on single-component gold complexes with extended-TTF dithiolate ligands [Au(dmdt)(2)](0+) (1) and [Au(tmdt)(2)](0+) (2) were prepared (dmdt = dimethyltetrathiafulvalenedithiolate and tmdt = trimethylenetetrathiafulvalenedithiolate). On the basis of the synchrotron radiation powder diffraction data, the MEM electron density of 2 was successfully obtained. The conductivities of compacted powder samples of 1 and 2 at room temperature were 12 and 15 S cm(-1), respectively. Pauli-like susceptibility of 1 suggested the system to be essentially metallic at least above 50 K, while 2 showed a magnetic transition around 100 K without loss of its high conductivity.

Journal Article↗
PubMed1998

In vivo and in vitro cloning and phenotype characterization of tellurite resistance determinant conferred by plasmid pTE53 of a clinical isolate of Escherichia coli.

A determinant encoding resistance against potassium tellurite (Te(r)) was discovered in a clinical isolate of Escherichia coli strain KL53. The strain formed typical black colonies on solid LB medium with tellurite. The determinant was located on a large conjugative plasmid designated pTE53. Electron-dense particles were observed in cells harboring pTE53 by electron microscopy. X-Ray identification analysis identified these deposits as elemental tellurium and X-ray diffraction analysis showed patterns typical of crystalline structures. Comparison with JCPDS 4-0554 (Joint Committee on Powder Diffraction Standards) reference data confirmed that these crystals were pure tellurium crystals. In common with other characterized Te(r) determinants, accumulation studies with radioactively labeled tellurite showed that reduced uptake of tellurite did not contribute to the resistance mechanism. Tellurite accumulation rates for E. coli strain AB1157 harboring pTE53 were twice higher than for the plasmid-free host strain. In addition, no efflux mechanism was detected. The potassium tellurite resistance determinant of plasmid pTE53 was cloned using both in vitro and in vivo techniques in low-copy-number vectors pACYC184 and mini-Mu derivative pPR46. Cloning of the functional Te(r) determinant into high-copy cloning vectors pTZ19R and mini-Mu derivatives pBEf and pJT2 was not successful. During in vivo cloning experiments, clones with unusual "white colony" phenotypes were found on solid LB with tellurite. All these clones were Mucts62 lysogens. Their tellurite resistance levels were in the same order as the wild type strains. Clones with the "white" phenotype had a 3.6 times lower content of tellurium than the tellurite-reducing strain. Transformation of a "white" mutant with a recombinant pACYC184 based Te(r) plasmid did not change the phenotype. However, when one clone was cured from Mucts62 the "white" phenotype reverted to the wild-type "black" phenotype. It was suggested that the "white" phenotype was the result of an insertional inactivation of an unknown chromosomal gene by Mucts62, which reduced the tellurite uptake.

Cloning, Molecular↗
PubMed1997

Correlations between 9Be magic-angle spinning nuclear magnetic resonance spectra and the geometry of beryllium containing framework structures.

A range of sodalite framework structures containing beryllium with general formula M8[BeZO4]6X2; M = Cd, Zn, Z = Si, Ge and X = S, Se or Te have been synthesised. The structures of these materials, which contain a single beryllium environment, have been refined from powder neutron diffraction or powder X-ray diffraction data and the compounds further characterised using 9Be magic-angle spinning nuclear magnetic resonance (MASNMR). Spectra show a single sharp resonance for 9Be(OSi)4 in the chemical shift range +/- 1 ppm from 0.1 M BeCl2. Correlations between the Be-O-Z bond angles and the 9Be chemical shift are reported and show upfield shifts for larger angles as seen previously in MASNMR spectra for 29Si and 27Al.

Beryllium↗
PubMed2005

Supercritical fluid crystallization of griseofulvin: crystal habit modification with a selective growth inhibitor.

Poly (sebacic anhydride) (PSA) was used as a growth inhibitor to selectively modify habit of griseofulvin crystals formed via the Precipitation with a compressed-fluid antisolvent (PCA) process. PSA and griseofulvin were coprecipitated within a PCA injector, which provided efficient mixing between the solution and compressed antisolvent process streams. Griseofulvin crystal habit was modified from acicular to bipyramidal when the mass ratio of PSA/griseofulvin in the solution feed stream was <or=1:1. The habit modification was attributed to the preferential adsorption of PSA to the fastest growing crystal face of the acicular crystal form, which inhibited growth. Scanning electron microscopy (SEM) was used to characterize the griseofulvin and PSA particles, and gave results consistent with a selective growth inhibition mechanism. SEM micrographs showed regions on griseofulvin crystals where PSA microparticles had preferentially adsorbed. X-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC) analysis of the griseofulvin crystals indicated no changes in the crystalline form after the habit modification. Powder compressibility decreased from 49 +/- 3% to 28 +/- 7% with the modification in crystal habit. No change in the physical stability of the processed powder was observed after being stored at 25 degrees C/60% RH and 40 degrees C/70% RH for 23 days. Despite the change in crystal habit, griseofulvin crystals achieved 100% dissolution within 60 min in a simulated gastric fluid.

Anhydrides↗
PubMed2005

Studies on the crystallinity of a pharmaceutical development drug substance.

The crystallinity and amorphous content of a micronized pharmaceutical development drug substance have been independently determined. An evaluation of different techniques for this purpose has been carried out, and it was found that solid-state nuclear magnetic resonance (ss NMR) and X-ray powder diffraction (XRPD) were suitable for the former and latter, respectively. The baseline intensities of X-ray powder diffractograms, associated with the amorphous component of the sample, have been used to detect levels of non-crystalline material greater than 5%w/w with an absolute accuracy of +/-3%. ss NMR has been employed to quantify crystalline defects at levels of greater than 3%w/w with an estimated uncertainty of +/-2%. It is proposed that such crystalline defects arise from molecular conformational differences that only have a small effect on crystal lattice parameters and, by implication, only have small effects on X-ray powder diffractograms. In both cases the techniques are shown to be highly reproducible and require minimal sample preparation. Excellent linearity is demonstrated for the determination of amorphous material using prepared standards. The present account describes the choice of analytical method, method validation and the results obtained for typical samples of drug substance. It is demonstrated that solid-state NMR should be used as a complementary technique with respect to XRPD for studying crystallinity.

Calorimetry, Differential Scanning↗
PubMed2006

Production of salbutamol sulfate for inhalation by high-gravity controlled antisolvent precipitation.

The purpose of this study was to produce salbutamol sulfate (SS) as a model anti-asthmatic drug using high-gravity controlled precipitation (HGCP) through antisolvent crystallisation. An aqueous solution of SS was passed through a HGCP reactor with isopropanol as antisolvent to induce precipitation. Spray drying was employed to obtain dry powders. Scanning electron microscopy, X-ray powder diffraction (XRD), density measurement, thermal gravimetric analysis, and dynamic vapour sorption were carried out to characterise the powder physical properties. The aerosol performance of the powders was measured using an Aeroliser connected to a multiple stage liquid impinger operating at 60 L/min. The HGCP SS particles were elongated with 0.1 microm in width but varying length of several mum, which formed spherical agglomerates when spray dried. The particles showed the same XRD pattern and true density (1.3g/cm3) as the raw material, indicating that they belonged to the same crystalline form. However, the spray dried agglomerates had a much lower tapped density (0.1g/cm3) than the raw material (0.6g/cm3). Compared with the powder obtained by spray drying directly from an aqueous solution, the SS powders obtained from HGCP were much less hygroscopic (0.6% versus 10% water uptake at 90% RH). The in vitro aerosol performance showed a fine particle fraction FPFloaded and FPFemitted up to 54.5+/-4.9% and 71.3+/-10.0%, respectively. In conclusion, SS powder with suitable physical and aerosol properties can be obtained through antisolvent HGCP followed by spray drying.

Aerosols↗
PubMed2005

The new diffractometer for surface X-ray diffraction at beamline BL9 of DELTA.

The experimental endstation of the hard X-ray beamline BL9 of the Dortmund Electron Accelerator is equipped with a Huber six-circle diffractometer. It is dedicated to grazing-incidence X-ray diffraction and X-ray reflectivity experiments on solid surfaces and thin films as well as to powder diffraction measurements. A new set-up for grazing-incidence X-ray scattering of liquids has been built up using a silicon mirror to reflect the incident X-ray to the liquid surface at angles of incidence around the critical angle of total reflection of the sample. X-ray reflectivity measurements of a polymer film and grazing-incidence X-ray diffraction measurements of an epitaxically grown Gd40Y60 film, an oxidized surface of Fe-15at.%Al alloy and aqueous salt solutions are presented and discussed.

Complex Mixtures↗
PubMed1994

X-ray, NMR, and theoretical studies of the nootropic agent BMY-21502, a pyrrolidinone derivative.

The preferred crystalline, solution, and in vacuo arrangements of 1-[[1-[2-trifluoromethyl)-4-pyrimidinyl]-4-piperidinyl]methyl]-2-pyrroli dinone (BMY-21502) were investigated by means of single-crystal X-ray diffraction, 1H and 13C NMR spectroscopy, and semiempirical molecular orbital and molecular mechanics calculations. The X-ray powder diffraction pattern is also reported.

Magnetic Resonance Spectroscopy↗
PubMed1998

Covalent Grafting of Phenylphosphonate Groups onto the Interlamellar Aluminol Surface of Kaolinite.

Kaolinite (K) was reacted with phenylphosphonic acid (PPA) in a water:acetone (1:1 V/V) solution (molar ratio 1 K:3 PPA), at 95 +/- 5 degreesC for different periods of time. Two different compounds (white powders) were identified but only one was isolated as a single phase and characterized by X-ray diffraction (powder method), thermal analysis (TG-DSC), Fourier-transformed infrared spectroscopy, and chemical analysis. The first compound showed a layer expansion of 7.86 Å and the second, a layer expansion of 9.29 Å, obtained as a decomposition product. Both compounds are consistent with the grafting of the phenylphosphonate group to the layers of kaolinite. The compounds have a formula of Al2Si2O5(OH)(HO3PPh)3.0 . 2H2O, as determined by thermal (water and total organic matter loss) and chemical (C content) analysis, respectively. Copyright 1998 Academic Press.

Journal Article↗
PubMed1994

High-density morphologies of ice in high-pressure frozen biological specimens.

Mouse liver tissue was rapidly cooled by high-pressure freezing at a nominal pressure of 2100 bar. Ultrathin cryosections were examined at 110 K with a cryoelectron microscope and the state of water was studied on micrographs and electron diffraction patterns. The results are compared with those from liver specimens cryofixed at ambient pressure by plunge freezing. The high-pressure frozen specimens contained crystalline frozen regions as well as areas which were vitreous. The spot diffraction patterns from crystalline regions are found to differ from those known for hexagonal ice. The comparison with powder diffraction data reveals the presence of the high-density morphologies Ice II and Ice III. Vitreous areas of biological samples frozen at ambient pressure are optically denser than areas where the water crystallised as cubic or hexagonal ice. However, on micrographs from high-pressure frozen samples, no significant contrast is found. This observation is explained by the higher specific mass of high-pressure ice compared to Ice I, an interpretation which requires a higher specific mass for high-pressure vitreous water compared to vitreous water produced at ambient pressure. The larger diffuse first ring of the diffraction pattern from high-pressure vitreous water confirms this argument.

Animals↗
PubMed2004

Surfactant-assisted synthesis of Keggin-type polyoxometalates nanorods.

It was demonstrated that Keggin-type polyoxometalates nanorods (POMs-nanorods) were prepared from a solution containing a surfactant polyethylene glycol (PEG), when heteropolyanions [X(n+)M12O40](-(8-n)) (X(n+) = P5+ and Si4+; M = W and Mo) were precipitated by ammonia ion obtained by hydrolysis of urea at 373 K. In this method, PEG was used as a template and ammonia ion (NH4+) was a counterion. In an oil bath kept at 373 K without stirring, three kinds of ammonium salts of POMs, i.e., (NH4)3PW12O40, (NH4)4SiW12O40, and (NH4)3PMo12O40 nanorods were obtained. The POMs-nanorods were characterized by transmission electron microscopy (TEM), selected area electron diffraction (SAED), infrared spectra (IR), inductively coupled plasma atomic emission spectrometry (ICP-AES) and X-ray powder diffraction (XRD). TEM showed that nanorods were 0.5-1.5 microm in length, and 50-150 nm in diameter. The results of IR, ICP-AES and XRD proved the existence of Keggin structure. The formation process of POMs-nanorods, (NH4)(8-n) [X(n+)M12O40](-(8-n)) (X(n+) = P5+ and Si4+; M = W and Mo) in a H2O/PEG system was discussed.

Electrons↗
PubMed1984

Pneumoconiosis in workers exposed to silicon carbide.

Two men who had been exposed only to silicon carbide for many years in a factory manufacturing refractory bricks developed bilateral reticulonodular densities, as shown on chest radiograms, and complained of dyspnea. An open lung biopsy of one of them showed a large amount of black material in the fibrosed alveolar septums. Studies by X-ray diffraction revealed that the silicon carbide to which they were exposed did not contain quartz; X-ray powder diffraction analysis of the lung tissue revealed at least 6 different silicon carbides, traces of tungsten carbide, and an insignificant amount of quartz. Line-width analysis of the pattern suggested that the lung contained foreign material, with a significant number of particles smaller than 0.1 micron. The etiologic role of silicon carbide for tissue fibrosis is discussed.

Adult↗
PubMed2005

Representing structural databases in a self-organizing map.

This paper presents a way to accomodate large numbers of crystal structures, as present in e.g. the Cambridge Structural Database (CSD), in a self-organizing map. The structures are represented by their calculated powder diffraction patterns. The use of a recently introduced similarity criterion is essential: the weighted cross-correlation. This accurately reflects the similarities of the powder patterns and therefore, indirectly measures the resemblance of crystal packings. It will be shown that good results are obtained, even if the network is trained with a small subset of a complete database. This makes it possible to construct the map on common hardware in a few hours. Such a map provides several possibilities for two-dimensional visualization, but additionally has a number of important applications. Two such applications are fast and easy screening of a database, and providing an overview of the contents of a database in terms of structural diversity of specific chemical classes of compounds, e.g. steroids or peptides. A third is the selection of archetypical structures, covering the complete structural space.

Algorithms↗
PubMed2006

Structure of montmorillonite cointercalated with stearic acid and octadecylamine: modeling, diffraction, IR spectroscopy.

Structural analysis of Na-montmorillonite co-intercalated with octadecylamine and stearic acid was carried out using combination of experiment: X-ray powder diffraction and IR spectroscopy with molecular modeling (force field calculations) in Cerius(2) modeling environment. Results of structure analysis revealed the chemical reaction of guest compounds leading to the formation of octadecylammonium stearate. This reaction may occur even before the intercalation out of the interlayer space of montmorillonite. The presence of octadecylammonium stearate in the samples was clearly confirmed by IR spectroscopy and X-ray diffraction. Present results also showed that: (1) Stearic acid itself does not intercalate into Na-montmorillonite; (2) cointercalation with octadecylamine led to the formation of octadecylammonium stearate, which was successfully intercalated into the interlayer space of montmorillonite, and (3) Na-montmorillonite intercalated with octadecylammonium stearate does not create a stable structure. Intercalated samples in ambient conditions undergo gradual decomposition, accompanied by the release of octadecylammonium stearate from the interlayer space and rearrangement of the interlayer structure. Co-intercalation of STA and ODA to lower the octadecylamine content and consequently to suppress the unfavorable effect of amine groups on the polymer matrix in nanocomposite, was investigated.

Journal Article↗