Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Powder Diffraction”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 541 records · Page 30Linked to original sources
PubMed2005

Boron-induced hydrogen localization in the novel metal hydride LaNi(3)BH(x) (x = 2.5-3.0).

The crystal structure and hydrogenation properties of the intermetallic boride LaNi(3)B were investigated. The hydrogen-free compound has a novel structure with orthorhombic symmetry, space group Imma, a = 4.9698(8) A, b = 7.1337(8) A, c = 8.3001(9) A, and V = 294.26(7) A(3). Thermal gravimetrical analysis reveals a hydride phase that forms near ambient conditions within the compositional range LaNi(3)BH(2.5)(-)(3.0). Single-crystal X-ray diffraction on both the alloy and the hydride, using the same crystal, shows an expansion in the a-c plane (by up to approximately 8%) and a contraction along b (by approximately 3%), while the symmetry changes from Imma to Bmmb (Cmcm) and the unit cell doubles along a and b. The cell parameters for the composition of LaNi(3)BD(2.73(4)) are a = 10.7709(7) A, b = 16.0852(10) A, c = 7.6365(5) A, V = 1323.03(15) A(3), and space group Cmcm. Four nearly fully occupied interstitial hydrogen sites were located by neutron powder diffraction on deuterides and found to have tetrahedral, La(2)Ni(2) (D1,D2), trigonal-prismatic, La(3)Ni(3) (D3), and trigonal-bipyramidal, La(2)Ni(3) (D4), metal environments. The structure can also be described in terms of alternating quasi two-dimensional [NiD](-) slabs (Ni-D = 1.62-1.97 A) and La-B sheets for which bond-valence sums suggest the limiting formula La(3+)B(0)[Ni(3)D(3)](3)(-). The La-B planes do not accommodate deuterium; the B-D and D-D interactions appear to be repulsive. The shortest B-D and D-D contacts are 2.52(2) and 2.33(2) A, respectively.

Journal Article↗
PubMed1998

Optical design of the general-purpose Spanish X-ray beamline for absorption and diffraction.

This paper describes the optical design of the general-purpose Spanish beamline for absorption and diffraction (SpLine), which will be installed on a bending-magnet port of the ESRF. This beamline is planned to cover the needs of the Spanish synchroton radiation community with broad scientific fields of interest, covering physics, chemistry, materials science and biology. By using the advantages of a wide front end (9 mrad), the Spanish beamline will be split into two branches. Both branches will be equipped with focusing optics and experimental stations. Thus, each branch can be operated simultaneously and independently from each other. One branch (A) will have two experimental stations, one for high-resolution powder diffraction (HRPD) and the other for X-ray absorption spectroscopy (XAS) and X-ray standing waves (XSW). The other branch (B) will have facilities for macromolecular crystallography and for single-crystal diffraction analysis, including that of surfaces and interfaces, as well as an X-ray diffraction/scattering camera for non-crystalline specimens.

Journal Article↗
PubMed2002

Preparation and characterisation of hydrocortisone particles using a supercritical fluids extraction process.

Crystallisation and subsequent milling of pharmaceutical powders by traditional methods often cause variations in physicochemical properties thereby influencing bioavailability of the formulation. Crystallisation of drug substances using supercritical fluids (SFs) offers some advantages over existing traditional methods in controlling particle characteristics. The novel particle formation method, solution enhanced dispersion by supercritical (SEDS) fluids was used for the preparation of hydrocortisone (HC) particles. The influence of processing conditions on the solid-state properties of the particles was studied. HC, an anti-inflammatory corticosteroid, particles were prepared from acetone and methanol solutions using the SEDS process. The solutions were dispersed with supercritical CO(2), acting as an anti-solvent, through a specially designed co-axial nozzle into a pressured vessel maintained at a specific constant temperature and pressure. The temperatures and pressures studied were 40-90 degrees C and 90-180 bar, respectively. The relative flow rates of drug solution to CO(2) were varied between 0.002 and 0.03. Solid-state characterisation of particles included differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD), solubility studies and scanning electron microscopy (SEM) examination. The aerodynamic properties of SEDS prepared particles were determined by a multistage liquid impinger (MLI). Particles produced from acetone solutions were crystalline needles, melting at 221+/-2 degrees C. Their morphology was independent of processing conditions. With methanol solutions, particles were flakes or needles depending on the processing temperature and pressure. This material melted at 216+/-1 degrees C, indicating a different crystal structure from the original material, in agreement with observed differences in the position and intensity of the XRPD peaks. The simulated lung deposition, using the MLI, for HC powder was improved after SEDS processing. It was possible to produce and control the crystallinity, morphology, and aerodynamic properties of HC particles with the SEDS technique. This method may be useful for the processing of inhalation powders.

Anti-Inflammatory Agents↗
PubMed1991

Kinetics and mechanism of the pressure-induced lamellar order/disorder transition in phosphatidylethanolamine: a time-resolved X-ray diffraction study.

By using synchrotron radiation, a movie was made of the X-ray scattering pattern from a biological liquid crystal undergoing a phase transition induced by a pressure jump. The system studied includes the fully hydrated phospholipid dihexadecylphosphatidylethanolamine in the lamellar gel (L beta') phase at a temperature of 68 degrees C and a pressure of 9.7 MPa (1400 psig). Following the rapid release of pressure to atmospheric the L beta' phase transforms slowly into the lamellar liquid crystal (L alpha) phase. The pressure perturbation is applied with the intention of producing a sudden phase disequilibrium followed by monitoring the system as it relaxes to its new equilibrium condition. Remarkably, the proportion of sample in the L alpha phase grows linearly with time, taking 37 s to totally consume the L beta' phase. The time dependencies of radius, peak intensity, and width of the powder diffraction ring of the low-angle (001) lamellar reflections were obtained from the movie by image processing. The concept of an "effective pressure" is introduced to account for the temperature variations that accompany the phase transition and to establish that the observed large transit time is indeed intrinsic to the sample and not due to heat exchange with the environment. The reverse transformation, L alpha to L beta', induced by a sudden jump from atmospheric pressure to 9.7 MPa, is complete in less than 13 s. These measurements represent a new approach for studying the kinetics of lipid phase transitions and for gaining insights into the mechanism of the lamellar order/disorder transition.

Kinetics↗
PubMed2006

Dehydration of trehalose dihydrate at low relative humidity and ambient temperature.

The physico-chemical behaviour of trehalose dihydrate during storage at low relative humidity and ambient temperature was investigated, using a combination of techniques commonly employed in pharmaceutical research. Weight loss, water content determinations, differential scanning calorimetry and X-ray powder diffraction showed that at low relative humidity (0.1% RH) and ambient temperature (25 degrees C) trehalose dihydrate dehydrates forming the alpha-polymorph. Physical examination of trehalose particles by scanning electron microscopy and of the dominant growth faces of trehalose crystals by environmentally controlled atomic force microscopy revealed significant changes in surface morphology upon partial dehydration, in particular the formation of cracks. These changes were not fully reversible upon complete rehydration at 50% RH. These findings should be considered when trehalose dihydrate is used as a pharmaceutical excipient in situations where surface properties are key to behaviour, for example as a carrier in a dry powder inhalation formulations, as morphological changes under common processing or storage conditions may lead to variations in formulation performance.

Calorimetry, Differential Scanning↗
PubMed1996

Recording diffraction data for structure determination for very small crystals.

An account is given of experiences in recording diffraction data with synchrotron radiation to determine structures for very small crystals, too small for use with conventional X-ray sources and diffractometers. The effect of crystal composition as well as size on the relative intensity of diffraction patterns of different crystals is noted. Crystal mounting is briefly described. Experimental methods are outlined including detectors and other instrumentation, and a range of examples is given; these include the use of both monochromatic area-detector systems for intensity measurement and of the white-beam Laue method. Choice of the shortest wavelength available with adequate intensity is recommended. The examples include organic, organometallic and aluminophosphate compounds; in all cases structure determination was important in relation to chemical research projects - they were not chosen as ;test' crystals. Comparison is made of the quality of the structure refinements achieved with those from synchrotron radiation powder diffraction - the alternative method when good-sized crystals are not available. Commonly it is found that when good-quality large crystals of a substance cannot be grown, the small crystals are poor in quality with substantial mosaic spread; the relationship between mosaic spread, structure, morphology and crystal growth is explored.

Journal Article↗
PubMedDate not supplied

Glycerol conformation and the crystal structure of lipids. I. An electron diffraction study of tripalmitin and conformationally fixed analogs.

Transmission electron diffraction is used as a qualitative analytical probe of polymethylene chain packing in three conformationally-restricted analogs of tripalmitin derived from configurational isomers of cyclopentane-1,2,3-triol. The analysis demonstrates that the all trans "tuning-fork" conformation seen in X-ray crystal structure analyses on homologous compounds is also found in microcrystals, in contrast to a proposal by Fringeli et al. (Z. Naturforsch. 27b, 780 [1972]) that an all cis conformation of the triglyceride exists in solvent-grown microcrystals and in multilayers. The presence of mixed polymorphs is also shown for bulk samples previously examined by X-ray powder diffraction techniques by other workers.

Crystallography↗
PubMedDate not supplied

Physical properties of microbial polythioesters: characterization of poly(3-mercaptoalkanoates) synthesized by engineered Escherichia coli.

Physical properties of chiral poly(thioesters), PTEs, prepared by engineered Escherichia coli, were examined by GPC, 13C CP/MAS solid-state NMR, X-ray diffraction, and thermal analysis. Microbial homopolymers of PTEs, poly(3-mercaptopropionate), PMP, and poly(3-mercaptovalerate), PMV, showed different solubility characteristics compared to poly(hydroxyalkanoates), PHAs. Generally, PTEs required higher temperatures for dissolution. Poly(3-mercaptobutyrate), PMB, and PMV dissolve in chloroform, and the molecular weight values were revealed by GPC as 176,000 and 165,000, respectively. The density values for PMP and PMB were 1.42 and 1.27 g/cm3, respectively. These values are similar to those for oxygen analogues. The NMR spectra for PTEs showed that carbonyl carbons are greatly shifted downfield by the sulfur atoms in the chain backbone compared to the PHA family. X-ray powder diffraction data indicated that PTEs are crystalline materials, but they do not crystallize as well as in the PHA family. The melting point, Tm, for PMP was 170 degrees C, which is about 100 degrees C higher than the equivalent oxygen analogue, poly(3-hydroxypropionate), PHP, and almost the same as that of bacterial poly(3-hydroxybutyrate), PHB. According to thermal analysis, only the PMP sample had enhanced heat stability, e.g., the decomposition temperature for PMP was 277 degrees C at 5% weight loss, whereas the values for PHP and PHB were 233 and 260 degrees C at the same weight loss, respectively.

Escherichia coli↗
PubMed2002

High resolution three-dimensional visualization and characterization of coronary atherosclerosis in vitro by synchrotron radiation x-ray microtomography and highly localized x-ray diffraction.

Human atherosclerotic plaques in both native and bypass arteries have been visualized using microtomography to provide additional information on the nature of coronary artery disease. Plaques contained within arteries removed from three white males aged 51, 55 and 70 are imaged in three-dimensions with monochromatic synchrotron x-ray radiation. Fields of view are 658 x 658 x 517 voxels. with cubic voxels ranging from 12 to 13 microm on a side. X-ray energies range from 11 to 15 keV (bandpass approximately 10 eV). At lower energies, high local absorption tends to generate reconstruction artefacts, while at higher energies the arterial wall is scarcely visible. At all energies, calcifications are clearly visible and differences are observed between plaques in native arteries (lifetime accumulations) versus bypass arteries (plaques developing in the interval between the heart bypass operation and the autopsy). In order to characterize coronary calcification, a microfocused, 50 microm2, 25 keV x-ray beam was used to acquire powder diffraction data from selected calcifications. Also, large calcifications were removed from the native arteries and imaged with 25 keV x-ray energy. Calcifications are composed of hydroxyapatite crystallites and an amorphous phase. In summary, native calcifications are larger and have a higher fraction of hydroxyapatite than calcifications from the bypass arteries.

Aged↗
PubMed2001

Characterisation of zeolitic materials with a HEU-type structure modified by transition metal elements: definition of acid sites in nickel-loaded crystals in the light of experimental and quantum-chemical results.

Nickel-loaded HEU-type zeolite crystals have been obtained by well-known synthetic procedures and characterised by X-ray fluorescence (XRF), scanning-electron microscopy/ energy-dispersive spectroscopy (SEM-EDS), FT-IR, diffuse reflectance UV/ Vis spectroscopy (DR(UV/Vis)S) and X-ray photoelectron spectroscopy (XPS) measurements as non-homoionic and non-stoichiometric substances containing exchangeable hydrated Ni2+ ions in the micropores and nickel hydroxide phases supported on the surface. Thermogravimetric analysis/differential gravimetry (TGA/DTG) and differential thermal analysis (DTA) demonstrated that full dehydration below approximately 400 degrees C follows a clearly endothermic process, whereas at higher temperatures the zeolite is amorphised and finally partially recrystallised to Ni(Al,Si) oxides, detected by powder X-ray powder diffraction (XRD). The solid acidity of NiHEU, initially determined by temperature-programmed desorption (TPD) of ammonia to be 8.93 mgg(-1) NH3, is attributed to the weak acid sites (fundamentally Lewis sites) resolved at approximately 183 degrees C, and to the strong acid sites (essentially Brønsted sites) resolved at approximately 461 degrees C in the TPD pattern. A more sophisticated study based on in situ/ex situ FT-IR with in situ/ex situ 27Al MAS NMR and pyridine (Py) as a probe molecule, revealed that the Lewis acid sites can be attributed primarily to Ni2+ ions, whereas the Brønsted ones can probably be associated with the surface-supported nickel hydroxide phases. The spectroscopic measurements in conjunction with powder XRD and 29Si MAS NMR data strongly suggest that distorted Al tetrahedra are formed during the dehydration process and Py chemisorption/complexation (NiHEU-Py), whereas the crystal structure is remarkably well preserved in the rehydrated material (NiHEU-Py/R). The structural, electronic, energetic and spectroscopic properties of all possible nickel(II) aqua and dihydroxy complexes absorbed in the zeolite micropores or supported on the zeolite surface were studied theoretically by density functional theory (DFT). The computed proton affinity, found to be in the range 182.0-210.0 kcalmol(-1), increases with increasing coordination number of the aqua and dihydroxy nickel(II) complexes.

Journal Article↗
PubMed2006

Mechanochemical approach to remove phenanthrene from a contaminated soil.

Soil samples collected from a cultivated soil of Southern Italy after artificial contamination with phenanthrene (PHE) were ground in a ball mill and compared with spiked (via acetone) sample as control. The mechanochemical treatment was also applied to a simple binary system birnessite (delta-MnO(2))-PHE and to soil added with birnessite to evaluate the oxide role in removing the contaminant. Different extraction methods, such as Soxhlet, sonication, and desorption from resin beads were adopted to estimate the residual PHE analysed with HPLC. X-ray diffraction and TG-DTA analyses were performed to quantify mineralogical phases in soil and their possible modifications after grinding. The results showed that the grinding was more efficient in removal of PHE when the pollutant was in solid phase ( approximately 50% of removal) than when it was spiked via acetone in the same soil ( approximately 20% of removal). Addition of birnessite to soil did not change significantly the removal of PHE through time. Independently of the extraction methods used, the PHE recovered after the mechanochemical treatment in the presence of solid PHE was always lower, suggesting a higher efficiency of such a treatment in degrading PHE or forming bound residues in its original or transformed form. X-ray powder diffraction of milled solid PHE showed that order-disorder phase transition occurred in solid phenanthrene as consequence of the mechanochemical treatment. X-ray diffractometry and TG-DTA analyses were crucial in evidencing that interaction between PHE and birnessite occurred.

Bacteria↗
PubMed1998

Physicochemical stability of crystalline sugars and their spray-dried forms: dependence upon relative humidity and suitability for use in powder inhalers.

Lactose, trehalose, sucrose, and mannitol were purchased in crystalline form and fractionated by sieving. Coarse (125-212 microns) and fine (44-74 microns) free-flowing fractions were selected as typical of drug carriers in dry-powder inhalers. In addition, one batch of each sugar was spray-dried to form a respirable powder (> 50% [w/w], < 5 microns). Both fractions and the spray-dried powders were characterized before and after storage for 30 days at < 23%, 23%, 52%, 75% and 93% relative humidity (RH) at 25 degrees C. Moisture uptake was determined by thermogravimetric analysis (TGA) validated by Karl Fischer titration. Sieve fractions (before storage at different RHs) and spray-dried materials (before and after storage) were further characterized by differential scanning calorimetry (DSC) and x-ray powder diffraction (XRPD). All crystalline sieve fractions (except sucrose at 93% RH) were stable at 25 degrees C and showed insignificant moisture uptake when exposed to each relative humidity for 30 days. Sucrose dissolved in sorbed moisture at 93% RH. Spray-dried lactose, sucrose, and trehalose, which were collected in the amorphous form, showed moisture uptake, without recrystallization, when held for 30 days at 23% RH. These sugars recrystallized as sintered masses and became undispersible at > or = 52% RH. Spray-dried mannitol was apparently 100% crystalline when collected directly from the spray-dryer; it did not show humidity-induced changes. The physicochemical behavior of each sugar form is discussed as it relates to the sugar's suitability as a powder-inhaler excipient, with both conventional and protein drugs.

Calorimetry, Differential Scanning↗
PubMed2001

Chiral metal-dithiolene/viologen ion pairs: synthesis and electrical conductivity.

Enantiomerically pure dithiolene complexes NBu4[Ni[(R,R)-diotte)2] and NBu4[Ni((S,S)-diotte]2] (diotte2- = a 1,3-dioxolane-tetrathiaethylene), were prepared from the corresponding enantiomers of a diotte2- precursor. The structure of the precursor was solved by single-crystal X-ray analysis; desulfurization afforded a novel tetrathiafulvalene derivative. Combination of the complex monoanion with the enantiomers of the viologen derivative bis(2-methyl-3-hydroxypropyl)-4,4'-dipyridinium (HiBV2+) afforded enantiomeric and diastereomeric ion-pair complexes of the type HiBV[Ni(diotte)2]2. For comparison, the analogous compounds A[Ni(diotte)2]2, (A2+ = methyl (MV2+), octyl (OV2-), stearyl (StV2+) viologen or two 2,2'-bipyridinium acceptors), HiBV-[Ni(diotte)L] [L = mnt2- (maleonitrile-1,2-dithiolate), dmit2- (2-thioxo-1,3-dithiol-4,5-dithiolate)], MV[Ni(dmit)2)]2, [Ni(diotte)2], and [Ni(diotte)(dmit)] were synthesized. An X-ray powder diffraction structural analysis of MV-[Ni(dmit)2)]2 revealed the presence of mixed stacks that contain the sequence anion-anion-cation. While no short contacts are observable within a stack, these are observed between the stacks for the dication-anion interaction by short S...H distances in the range of 2.77 to 2.86 A, and for the anion-anion interaction short S...S distances of 3.55 to 3.65 A. In agreement with the absence of intrastack interactions, no ion-pair charge-transfer band can be detected in this and the other complexes. ESR and UV/Vis data suggest that in [Ni(diotte)2]- electron delocalization is less pronounced than in the corresponding mnt2- and dmit2- complexes. The specific electrical conductivity (sigma) of pressed powder pellets ranges from 10(-2) to 10(-12) ohm(-1) cm(-1) and in all cases increases with increasing temperature (293 - 393 K) according to an Arrhenius law. Corresponding activation energies vary from 0.14 to 0.93 eV and increase linearly with log a for structurally similar ion pairs. Charge generation is postulated to occur by disproportionation of the monoanion as suggested by the almost linear increase of log(sigma) with decreasing disproportionation energy. The conductivity of diastereomers of ions with two unlike configurations like [(S,S)-HiBV]-[Ni[(R,R)-diotte]2]2 (1.1 x 10(-1) ohm(-1) cm(-1)) is one to two orders of magnitude higher as compared to the diastereomers with two like-configured ions.

Journal Article↗
PubMed1987

Polymorphs of tamoxifen citrate: detailed structural characterization of the stable form.

The structure of the stable polymorph of tamoxifen citrate (form B) has been analyzed by single crystal X-ray diffraction [monoclinic, a = 15.998 (4), b = 21.964 (3), c = 8.624 (5) A, beta = 96.28 (3) degrees, space group P2(1)/c]. The results include conformational details of the molecular structure as well as a description of the observed packing arrangement in the solid which is dominated by hydrogen-bonding interactions between the ionic entities. The proton transfer to the nitrogen atom of tamoxifen is from the central carboxyl group of the citric acid. There is a satisfactory correlation between the solid infrared spectrum of the carboxylic functions and the asymmetric environment observed around them in the crystal lattice. Additional results obtained from thermal and spectral analyses suggest that the second polymorph of tamoxifen citrate (form A) represents a metastable form of this compound. The two polymorphs are characterized by their powder diffraction spectra.

Chemical Phenomena↗
PubMed2002

Di-tert-butyl phosphate as synthon for metal phosphate materials via single-source coordination polymers [M(dtbp)(2)](n) (M = Mn, Cu) and [Cd(dtbp)(2)(H2O)](n) (dtbp-H = (tBuO)(2)P(O)OH).

Reaction of M(OAc)(2).xH(2)O (M = Mn, Cu, or Cd) with di-tert-butyl phosphate (dtbp-H) in a 1:2 molar ratio in methanol followed by slow crystallization of the resultant solid in MeOH/THF medium results in the formation of three new polymeric metal phosphates [M(dtbp)(2)](n)() [M = Mn, 1 (beige); M = Cu, 2 (blue)] and [Cd(dtbp)(2)(H(2)O)](n)(), 3 (colorless)] in good yields. The formation of [Mn(dtbp)(2)](n) (1) proceeds via tetrameric manganese phosphate [Mn(4)(O)(dtbp)(6)] (4), which has been isolated in an analytically pure form. Perfectly air- and moisture-stable compounds 1-4 were characterized with the aid of analytical, thermoanalytical, and spectroscopic techniques. The molecular structures of 1-3 were further established by single-crystal X-ray diffraction studies. Crystal data for 1: C(32)H(72)Mn(2)O(16)P(4), monoclinic, P2(1)/c, a = 19.957(4) A, b = 13.419(1) A, c = 18.083(2) A, beta = 91.25(2) degrees, Z = 4. Crystal data for 2: C(16)H(36)CuO(8)P(2), orthorhombic, Pccn, a = 23.777(2) A, b = 10.074(1) A, c = 10.090(1) A, Z = 4. Crystal data for 3: C(48)H(114)Cd(3)O(27)P(6), triclinic, P1, a = 12.689(3) A, b = 14.364(3) A, c = 22.491(5) A, alpha = 84.54(3) degrees, beta = 79.43(3) degrees, gamma = 70.03(3) degrees, Z = 2. The diffraction studies reveal three different structural forms for the three compounds investigated, each possessing a one-dimensional coordination polymeric structure. While alternating triple and single dtbp bridges are found between the adjacent Mn(2+) ions in 1, uniform double dtbp bridges across the adjacent Cu(2+) ions are present in 2. The cadmium ions in the structure of 3 are pentacoordinated. Thermal analysis (TGA and DSC) indicates that compounds 1-3 convert to the corresponding crystalline metaphosphate materials M(PO(3))(2), in each case at temperatures below 500 degrees C. Similarly, the thermal decomposition of 4 results in the formation of Mn(PO(3))(3) and Mn(2)P(2)O(7). The final materials obtained by independent thermal decomposition of bulk samples have been characterized using IR spectroscopic, powder diffraction, and N(2) adsorption studies.

Journal Article↗
PubMed1997

The effect of operating and formulation variables on the morphology of spray-dried protein particles.

The purpose of this research was to investigate the shape and morphology of various spray-dried protein powders as a function of spray-drying conditions and protein formulations. A benchtop spray dryer was used to spray dry three model proteins in formulation with a sugar or a surfactant. Physical characterizations of the powder included morphology (scanning electron microscopy), particle size, residual moisture, and X-ray powder diffraction analyses. A significant change in particle shape from irregular (e.g., "donut") to spherical was observed as the outlet temperature of the dryer was decreased. The drying air outlet temperature was shown to depend on various operating parameters and was found to correlate with the drying rate of atomized droplets in the drying chamber. The morphology of spray-dried protein particles was also affected by formulation. In protein:sugar formulations, spray-dried particles exhibited a smooth surface regardless of the protein-to-lactose ratio, whereas roughness was observed when mannitol was present at > 30% of total solids, due to recrystallization. Protein particles containing trehalose at concentrations > 50% were highly agglomerated. The presence of surfactant resulted in noticeably smoother, more spherical particles. The shape and the morphology of spray-dried powders are affected by spray drying conditions and protein formulation. This study provides information useful for development of dry proteins for fine powder (e.g., aerosol) applications.

Antibodies, Monoclonal↗
PubMed1999

Low-Temperature Formation of alpha-Alumina by Doping of an Alumina-Sol.

In our present study, the phase transition behavior of gamma-alumina doped by an alumina-sol was explored using X-ray powder diffraction and transmission electron microscopy. It was found that the addition of an alumina-sol into gamma-alumina enabled the onset of the gamma- to alpha-alumina transformation at temperatures as low as 600 degreesC. This phenomenon was designated as the "sol-effect." Although the onset temperature of the phase transformation was very low, the transformation was completed at 1100 degreesC which is the same as that observed with the seeding method. Further investigation revealed that the transformation was composed of two steps. One occurs over the temperature region from 600 to 950 degreesC where a slow increase in the content of alpha-alumina is observed. The other is the region from 950 to 1100 degreesC where a rapid increase of alpha-alumina occurs due to "self-seeding." The "sol-effect" produces powders with very fine alpha-alumina particle sizes and little agglomeration. Copyright 1999 Academic Press.

Journal Article↗
PubMed2001

Characterisation of mineralogical forms of barium and trace heavy metal impurities in commercial barytes by EPMA, XRD and ICP-MS.

This study was carried out to characterise the mineralogical forms of barium and the trace heavy metal impurities in commercial barytes of different origins using electron probe microanalysis (EPMA), X-ray diffraction (XRD) and inductively coupled plasma mass spectrometry (ICP-MS). Qualitative EPMA results show the presence of typically eight different minerals in commercial barytes including barite (BaSO4), barium feldspar, galena (PbS), pyrite (FeS2), sphalerite (ZnS), quartz (SiO2), and silicates, etc. Quantitative EPMA confirms that the barite crystals in the barytes contain some strontium and a little calcium, whereas trace heavy metals occur in the associated minerals. Analysis of aqua regia extracts of barytes samples by ICP-MS has shown the presence of a large number of elements in the associated minerals. Arsenic, copper and zinc concentrations correlate closely in all 10 samples. The findings suggest that barytes is not, as traditionally thought, an inert mineral, but is a potentially toxic substance due to its associated heavy metal impurities, which can be determined by an aqua regia digest without the need for complete dissolution of the barite itself. X-ray powder diffraction was not informative as the complex barite pattern masks the very weak lines from the small amounts of associated minerals.

Barium↗