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Tservistas M, Levy MS, Lo-Yim MY, O'Kennedy RD, York P, Humphrey GO, Hoare M. The formation of plasmid DNA loaded pharmaceutical powders using supercritical fluid technology. Biotechnol Bioeng 2001; 72:12-8. [PMID: 11084588 DOI: 10.1002/1097-0290(20010105)72:1<12::aid-bit2>3.0.co;2-z] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The invention of novel drugs based on biological macromolecules requires the development of specialized formulation methods. Supercritical fluid technology offers the possibility to produce dry powder formulations suitable for inhalation or needle-free injection. In this article we describe the first application of a process involving supercritical carbon dioxide for the production of plasmid DNA-loaded particles. The technique of solution enhanced dispersion by supercritical fluids (SEDS) is used to coformulate the 6.9 kb plasmid pSV beta with mannitol as excipient. After initial experiments showed a high degradation of the plasmid during powder formation, a systematic investigation of the process revealed pH effects to be crucial for the recovery of intact DNA. The application of high-buffer concentration led to an increase of the recovered supercoiled proportion from 7% to 80%.
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Crowley KJ, Forbes RT, York P, Nyqvist H, Camber O. Drug-fatty acid salt with wax-like properties employed as binder in melt granulation. Int J Pharm 2000; 211:9-17. [PMID: 11137334 DOI: 10.1016/s0378-5173(00)00577-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The tacky and deformable properties of a wax-like drug-fatty acid salt, propranolol oleate (POA), make particle size reduction and separation challenging. The aim of this study was to investigate the use of POA as binder in a melt granulation procedure to improve processing properties. POA is a suitable candidate for binder phase in melt granulation with a melting temperature of 50-56 degrees C. Small batches (ca 30 g) were manufactured using a high shear mixer with lactose monohydrate as the substrate phase. Optimum uniformity of drug content and minimum friability were found at 10% w/w POA binder concentration. POA melt granules exhibited a >10-fold increase in the rate of in vitro dissolution at pH 7.4 with 0.2% w/v sodium lauryl sulphate compared with raw POA. The increased drug surface area in granular form was thought to be responsible for the change in dissolution behaviour. This study has demonstrated that melt granulation using POA as binder is a viable process which leads to beneficial changes in dissolution behaviour for the lipophilic drug-fatty acid salt.
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Raghavan SL, Ristic RI, Sheen DB, Sherwood JN, Trowbridge L, York P. Morphology of Crystals of α-Lactose Hydrate Grown from Aqueous Solution. J Phys Chem B 2000. [DOI: 10.1021/jp002051o] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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54
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Crowley KJ, Forbes RT, York P, Apperley DC, Nyqvist H, Camber O. Characterization of oleic acid and propranolol oleate mesomorphism using (13)C solid-state nuclear magnetic resonance spectroscopy (SSNMR). J Pharm Sci 2000; 89:1286-95. [PMID: 10980503 DOI: 10.1002/1520-6017(200010)89:10<1286::aid-jps6>3.0.co;2-o] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Lipids regularly exhibit complicated thermotropic and lyotropic phase behavior. In this study, the utility of (13)C solid-state nuclear magnetic resonance spectroscopy (SSNMR) in characterizing the phase properties of pharmaceutical lipids was investigated. Variable temperature (13)C SSNMR spectra and spin-lattice relaxation times (T(1)(C)) were obtained for high-purity oleic acid (OA) and propranolol oleate (POA). Spectral changes took place following OA gamma-to-alpha phase transition that indicated increased nuclear inequivalence of aliphatic chain carbons in the alpha phase. T(1)(C) data for the alpha phase demonstrated considerable conformational changes throughout the aliphatic chain, not solely in the methyl side chain as previously reported. These data support alpha-OA classification as a conformationally disordered crystalline phase. The prevalence of low T(1)(C) values in both POA I and II suggested the absence of a rigid crystalline molecular lattice, so both phases were described as conformationally disordered crystalline phases. A two-phase mixture of POA I and II was also identified, emphasizing the sensitivity of this technique. (13)C SSNMR provided valuable information regarding the nuclear environment of specific functional groups in lipid crystalline and mesomorphic structures. Understanding phase behavior at the molecular level can aid selection of appropriate formulation strategies for lipids by allowing prediction of processing properties, and physical and chemical stability. (13)C SSNMR is a powerful technique for pharmaceutical lipid characterization.
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York P. ParticleâParticle Adhesion in Pharmaceutical Powder Handling, Fridrun Podczeck, Imperial College Press, 1998. ISBN 1-86094-112-5. Int J Pharm 2000. [DOI: 10.1016/s0378-5173(00)00518-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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56
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Moshashaée S, Bisrat M, Forbes RT, Nyqvist H, York P. Supercritical fluid processing of proteins. I: lysozyme precipitation from organic solution. Eur J Pharm Sci 2000; 11:239-45. [PMID: 11042230 DOI: 10.1016/s0928-0987(00)00108-1] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The solution enhanced dispersion by supercritical fluid (SEDS) process was used to evaluate the effect of the processing variables on the biological and physicochemical characteristics of lysozyme protein particles produced from an organic solution of dimethylsulfoxide (DMSO) using an experimental design procedure. The processing variables were temperature, pressure, solution concentration and the flow-rates of supercritical carbon dioxide and a protein solution. Solutions of hen egg lysozyme (0.5-1%, w/v) in DMSO were dispersed using supercritical carbon dioxide as the antisolvent, and particles precipitated in a particle formation vessel. The morphology, particle size and size distribution and biological activity of the protein were determined. The precipitates were also examined with high sensitivity differential scanning calorimetry (HSDSC) and high-performance cation-exchange chromatography. The amount of residual DMSO was determined using headspace gas chromatography. Particle size measurements showed the precipitates to be agglomerates with primary particles of size 1-5 microm, containing <20 ppm of residual solvent. The activity of the precipitates varied between 44 and 100% depending on the experimental conditions. The similarity of HSDSC data for unprocessed and processed samples indicated that the SEDS process does not cause major denaturation of lysozyme when prepared from DMSO solutions. By optimising of working conditions, the SEDS process can produce micron-sized particles of lysozyme with minimal loss of biological activity.
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Grimsey IM, Sunkersett M, Osborn JC, York P, Rowe RC. Interpretation of the differences in the surface energetics of two optical forms of mannitol by inverse gas chromatography and molecular modelling. Int J Pharm 1999; 191:43-50. [PMID: 10556739 DOI: 10.1016/s0378-5173(99)00284-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Inverse gas chromatography (IGC) has been successfully used to characterise the nature of the surface of two optical forms of mannitol, DL and betaD. This has shown that the surface energetics of the two forms are significantly different with the DL form having higher values for the interactions with the dispersive and basic probes. Molecular modelling was used to predict the slip planes by utilising attachment energy calculations and so the dominant faces exposed upon milling could be predicted. Imaging these faces showed that the orientation of the molecules at these surfaces differed between the two forms. A visual comparison of the faces indicated that the DL form had a higher density of acidic and dispersive sites exposed at the surfaces than the betaD form. The results from the modelling agreed with the trends seen in the changes in surface energetics as measured by IGC. This suggests that the components of the surface energetic terms reflect the density of exposed groups at the particle surfaces.
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Greenhalgh DJ, Williams AC, Timmins P, York P. Solubility parameters as predictors of miscibility in solid dispersions. J Pharm Sci 1999; 88:1182-90. [PMID: 10564068 DOI: 10.1021/js9900856] [Citation(s) in RCA: 419] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This paper reports interactions and possible incompatibilities in solid dispersions of hydrophobic drugs with hydrophilic carriers, with solubility parameters employed as a means of interpreting results. Systems containing ibuprofen (IB) and xylitol (XYL) in varying proportions and systems of IB with other sugars and a sugar polymer were produced using solvent evaporation and fusion methods. Additionally, bridging agents were employed with IB/XYL systems to facilitate the production of a solid dispersion. Results show that IB formed no interactions with any of the sugar carriers but interacted with all the bridging agents studied. The bridging agents were immiscible with XYL in the liquid state. Results of other reported drug/carrier systems and those from the systems studied in this paper were interpreted using Hildebrand solubility parameters. A trend between differences in drug/carrier solubility parameters and immiscibility was identified with incompatibilities evidence when large solubility parameter differences exist between drug and carrier. It was concluded that Hildebrand parameters give an indication of possible incompatibilities between drugs and carriers in solid dispersions, but that the use of partial solubility parameters may provide a more accurate prediction of interactions in and between materials and could provide more accurate indications of potential incompatibilities.
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Branchu S, Forbes RT, York P, Petrén S, Nyqvist H, Camber O. Hydroxypropyl-beta-cyclodextrin inhibits spray-drying-induced inactivation of beta-galactosidase. J Pharm Sci 1999; 88:905-11. [PMID: 10479352 DOI: 10.1021/js9804819] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The single-step, fast spray-drying process may represent a valuable alternative to the multistep, time-consuming freeze-drying process in the area of formulation and processing of biopharmaceuticals. In this study, we tested the use of sucrose and hydroxypropyl-beta-cyclodextrin (HP-beta-CD) as stabilizing excipients in the spray-drying of a model protein, beta-galactosidase. The solutions were processed using a Büchi 190 cocurrent Mini Spray Dryer at an outlet temperature of 61 +/- 2 degrees C. The powders were redissolved and analyzed for catalytic activity, aggregation, chemical decomposition, and thermal susceptibility as observed by high-resolution calorimetry. Spray-drying significantly inactivated beta-galactosidase. Spray-drying beta-galactosidase in the presence of sucrose did not prevent inactivation. However, after spray-drying beta-galactosidase in the presence of HP-beta-CD, or HP-beta-CD and sucrose, full catalytic activity was exhibited on reconstitution. Furthermore, the reconstituted product was unchanged in terms of molecular weight, charge, and thermal stability. These findings are consistent with a hypothesis that the change responsible for inactivation of beta-galactosidase was mainly a monomolecular, noncovalent change, i. e., the formation of incorrect structures, that arose from surface denaturation. This study clearly demonstrates that cyclodextrins can be useful stabilizing excipients in the preparation of spray-dried protein pharmaceuticals.
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Kordikowski A, York P, Latham D. Resolution of ephedrine in supercritical CO(2): A novel technique for the separation of chiral drugs. J Pharm Sci 1999; 88:786-91. [PMID: 10430543 DOI: 10.1021/js980459f] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Racemic ephedrine has been resolved by diastereomeric salt formation with mandelic acid using supercritical CO(2) as precipitating agent. Crystallizations were performed using the Solution Enhanced Dispersion by Supercritical Fluids (SEDS) technique. Temperature was varied between 35 and 75 degrees C, and pressures ranged from 100 to 350 bar. Resolution, determined by chiral capillary electrophoresis, is described as a function of temperature and density of the supercritical fluid. A comparison of SEDS-produced material with a conventional resolution method shows that SEDS-crystallized material exhibits identical properties to conventionally crystallized material.
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Palakodaty S, York P. Phase behavioral effects on particle formation processes using supercritical fluids. Pharm Res 1999; 16:976-85. [PMID: 10450920 DOI: 10.1023/a:1011957512347] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The application of supercritical fluid (SF) processing in pharmaceutical research is increasing particularly in the field of particle formation for drug delivery systems. The SF processes have benefits over the existing particle formation methods in terms of improved control, flexibility and operational ease. This review highlights the fundamental concepts of fluid phase behaviour and their influence on the various processes involving particle formation with supercritical fluids. Several phase behaviour systems are discussed to provide an insight into the factors influencing the process paths and their effects on the characteristics of the particles.
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Crowley KJ, Forbes RT, York P, Nyqvist H, Camber O. Oleate salt formation and mesomorphic behavior in the propranolol/oleic acid binary system. J Pharm Sci 1999; 88:586-91. [PMID: 10350493 DOI: 10.1021/js9804967] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Thermal analysis of propranolol/oleic acid mixtures prepared by solvent evaporation enabled construction of the binary system phase diagram. This allowed both physical and chemical interactions to be identified, including complex formation at the equimolar composition. An incongruent melting complex with a characteristic reaction point was identified in excess oleic acid compositions, a common property of fatty acid/fatty acid salt binary systems. The equimolar complex was confirmed to be propranolol oleate using infrared spectroscopy. Wide-angle X-ray powder diffractometry demonstrated that propranolol oleate possessed long-range positional order ( approximately 25 A d spacing) accompanied by a degree of disorder over shorter d spacings. Such a pattern suggested mesophase formation, explaining the unctuous nature of propranolol oleate at room temperature. Accurate measurement of the long-range d spacing was achieved using small-angle X-ray scattering, permitting differentiation of the three different phases identified (phase I: 25.4 A, phase II: 24.6 A, phase III: 25.4-25.5 A). The implications of drug fatty acid salt formation and also mesomorphism in pharmaceutical systems are discussed.
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63
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Landín M, York P, Cliff MJ, Rowe RC. Scaleup of a pharmaceutical granulation in planetary mixers. Pharm Dev Technol 1999; 4:145-50. [PMID: 10231876 DOI: 10.1081/pdt-100101349] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The scaleup of a pharmaceutical granulation in a series of planetary mixers with increasing bowl capacity between 5 and 200 liters has been studied by applying the classical dimensionless numbers of Power, Reynolds, and Froude to define the power consumption profile of each mixer as a function of the processing conditions in dimensionless form. Experiments were performed using a formulation based on dicalcium phosphate dihydrate containing pregelatinized starch, with water being added at a fixed rate. Samples were taken at different power consumptions and assessed using mixer torque rheometry. Geometrically similar machines gave the same dimensionless relationship, but when similarity was compromised by the use of modified bowls and blades, different relationships occurred. The results show that, for geometrically similar machines, it is possible to calculate the power consumption at a predefined granulation endpoint at any given operating condition at any scale.
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Branchu S, Forbes RT, York P, Nyqvist H. A central composite design to investigate the thermal stabilization of lysozyme. Pharm Res 1999; 16:702-8. [PMID: 10350014 DOI: 10.1023/a:1018876625126] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
PURPOSE The formulation and processing of protein drugs requires the stabilization of the native, biologically active structure. Our aim was to investigate the thermal stability of a model protein, lysozyme, in the presence of two model excipients, sucrose and hydroxypropyl-beta-cyclodextrin (HP-beta-CD). METHODS We used high sensitivity differential scanning calorimetry (HSDSC) in combination with a central composite design (CCD). As indicators of protein thermal stability, the measured responses were the unfolding transition temperature (Tm), the onset temperature of the denaturation (To), and the extrapolated onset temperature (To,e). RESULTS A highly significant (F probability <0.001) statistical model resulted from analysis of the data The largest effect was due to pH (over the range 3.2-7.2), and the pH value that maximized Tm was 4.8. Several minor but significant effects were detected that were useful for mechanistic understanding. In particular, the effects of protein concentration and cyclodextrin concentration on Tm and To,e were found to be pH-dependent This was indicative of the partially hydrophilic nature of protein-protein interactions and protein-cyclodextrin interactions, respectively. CONCLUSIONS Response surface methodology (RSM) proved efficient for the modeling and optimization of lysozyme thermal stability as well as for the physical understanding of the protein-sugar-cyclodextrin system in aqueous solution.
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Faure A, Grimsey IM, Rowe RC, York P, Cliff MJ. Applicability of a scale-up methodology for wet granulation processes in Collette Gral high shear mixer-granulators. Eur J Pharm Sci 1999; 8:85-93. [PMID: 10210730 DOI: 10.1016/s0928-0987(98)00063-3] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
This study investigates the extension of a scale-up methodology based on dimensionless power relationships, to a series of vertical mixer-granulators in which the bowl is removable, i.e. both impeller and chopper blades are mounted on top-driven vertical shafts positioned through the lid. Granulation runs were carried out in several bowl sizes belonging to the series of Collette Gral mixer-granulators, ranging from 8 to 600 l capacities. It was shown that under certain conditions a common scale-up master curve could be drawn from the data gathered for each bowl, thus permitting the use of such a curve for the determination of mixer-granulator power consumption at a defined granulation end-point. The results also helped to clarify the concept of similitude, both geometrical and dynamic, which is implied in the methodology. The importance of wall slippage (as promoted by the insertion of a PTFE lining into the bowls) and batch size are illustrated.
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Faure A, Grimsey IM, Rowe RC, York P, Cliff MJ. Process control in a high shear mixer-granulator using wet mass consistency: the effect of formulation variables. J Pharm Sci 1999; 88:191-5. [PMID: 9950637 DOI: 10.1021/js9803454] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
This work investigates the relationships between the wet mass consistency/viscosity of samples prepared in a mixer-granulator and physical properties of the dry granules produced from the wet mass; namely, size distribution, bulk density (Hausner ratio), friability, and flow avalanching behavior. The correlation between the consistency of the wet mass and the downstream dry granule properties confirms that consistency is the key parameter to control in wet granulation by mechanical agitation. Variations in the formulation affect the dimensionless power relationship of the mixer-granulator considered; that is, the equivalence between wet mass consistency and mixer net power consumption, which is actually the parameter used to monitor the wet granulation process. The same variations in formulation also affect the relationships between wet mass consistency and dry granule properties.
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67
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Osborn J, York P. A comparison of sublimation enthalpies with lattice energies calculated using force fields. J Mol Struct 1999. [DOI: 10.1016/s0022-2860(98)00558-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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68
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Palakodaty S, York P, Pritchard J. Supercritical fluid processing of materials from aqueous solutions: the application of SEDS to lactose as a model substance. Pharm Res 1998; 15:1835-43. [PMID: 9892466 DOI: 10.1023/a:1011949805156] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
PURPOSE The objective of the work was to study the factors influencing the crystallisation of alpha-lactose monohydrate from aqueous solution using the Solution Enhanced Dispersion by Supercritical Fluids (SEDS) technique. METHODS An aqueous solution of alpha-lactose monohydrate is dispersed with a homogeneous mixture of carbon dioxide-ethanol/methanol using a co-axial nozzle. Crystallised lactose particles were analysed for water content by Karl-Fisher analysis, anomeric composition by Differential Scanning Calorimetry (DSC) and characterised for crystallinity by powder X-ray diffraction and morphology by scanning electron microscopy. RESULTS Water content in the lactose recrystallised with ethanol was higher compared to the product obtained with methanol as cosolvent. Rate of crystallisation could be altered by varying the CO2 flow thereby modifying the water content in the lactose. At low flow rates of CO2, the crystallisation occurred in a cosolvent rich antisolvent phase causing rapid crystallisation whereas high flow rates of CO2 favoured a much slower crystallisation mechanism in the water rich phase. As a consequence, the morphology changed from thin long bands to large agglomerated chunks with mean particle size between 5 and 31 microns. CONCLUSIONS The SEDS process is an efficient method for forming micron sized particles of water-soluble compounds with controlled physico-chemical properties.
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Faure A, Grimsey IM, Rowe RC, York P, Cliff MJ. Importance of wet mass consistency in the control of wet granulation by mechanical agitation: a demonstration. J Pharm Pharmacol 1998; 50:1431-2. [PMID: 10052861 DOI: 10.1111/j.2042-7158.1998.tb03371.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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70
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York P, Ticehurst M, Osborn J, Roberts R, Rowe R. Characterisation of the surface energetics of milled dl-propranolol hydrochloride using inverse gas chromatography and molecular modelling. Int J Pharm 1998. [DOI: 10.1016/s0378-5173(98)00247-6] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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71
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Singer MI, Slovak K, Frierson T, York P. Viewing preferences, symptoms of psychological trauma, and violent behaviors among children who watch television. J Am Acad Child Adolesc Psychiatry 1998; 37:1041-8. [PMID: 9785715 DOI: 10.1097/00004583-199810000-00014] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE To examine the extent to which children's television-viewing practices are associated with symptoms of psychological trauma and aggressive behaviors. The following three hypotheses were tested: (1) children who report watching greater amounts of television per day will report higher levels of trauma symptoms than children who report lesser amounts of television viewing; (2) children who report watching greater amounts of television per day will report higher levels of violent behaviors than children who report watching lesser amounts of television per day; and (3) children who report a preference for action and fighting programs will report higher levels of violent behaviors than children who report a preference for other types of television programs. METHOD The study used a survey design in which an anonymous self-report questionnaire was administered to students in grades 3 through 8 in 11 Ohio public schools during the 1995-1996 school year (N = 2,245). RESULTS All three hypotheses were supported. CONCLUSION Heavy television viewing by children may indicate the presence of problems such as depression, anxiety, and violent behaviors; such viewing should be screened for by psychiatrists and other mental health professionals working with children.
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Feeley J, York P, Sumby B, Dicks H. Determination of surface properties and flow characteristics of salbutamol sulphate, before and after micronisation. Int J Pharm 1998. [DOI: 10.1016/s0378-5173(98)00179-3] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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73
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Taylor LS, Williams AC, York P. Particle size dependent molecular rearrangements during the dehydration of trehalose dihydrate in situ FT-Raman spectroscopy. Pharm Res 1998; 15:1207-14. [PMID: 9706051 DOI: 10.1023/a:1011935723444] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
PURPOSE (1) To characterise the different phases of trehalose using FT-Raman spectroscopy. (2) To monitor the changes in the structure of trehalose dihydrate on isothermal heating at 80 degrees C. METHODS Different phases of trehalose were prepared and FT-Raman spectra obtained. Trehalose dihydrate was sieved to < 45 microns and > 425 microns particle size fractions and FT-Raman spectra were obtained at various time intervals during heating at 80 degrees C. RESULTS During heating at this temperature, the spectra of a < 45 microns particle size fraction showed a loss of peak resolution with time and after 210 minutes resembled the spectrum of amorphous trehalose prepared by lyophilisation, indicating that the material was rendered amorphous by heating. In contrast, spectra obtained from a > 425 micron particle size fraction altered with time and became characteristic of the crystalline anhydrate. The approximate kinetics of this transformation to the anhydrate were monitored by analysis of peak intensity ratios with time. A two state rearrangement was indicated; some functional groups appeared to manoeuvre into the spatial arrangement found in the anhydrate initially before the rest of the ring structure relaxed into this conformation. This may be due to some parts of the molecule being immediately affected by the loss of the water molecules on dehydration prior to the subsequent reorientation of the entire molecule into the anhydrate crystal lattice. CONCLUSIONS The < 45 micron particle size fraction becomes disordered on dehydration induced by heating at 80 degrees C whilst the > 425 micron particle size fraction crystallises to the anhydrate under the same conditions.
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Faure A, Grimsey IM, Rowe RC, York P, Cliff MJ. A methodology for the optimization of wet granulation in a model planetary mixer. Pharm Dev Technol 1998; 3:413-22. [PMID: 9742562 DOI: 10.3109/10837459809009869] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
This paper investigates a methodology for the optimization of wet granulation processes in planetary mixers. A model formulation was granulated in a planetary mixer (two different bowl sizes). The wet masses were characterized by their bulk density and consistency (as measured by mixer torque rheometry), and the feasibility of scale-up from one mixer bowl to the other was studied using a dimensionless numbers approach for the estimation of the power consumption at the granulation end point. Both bowls gave the same dimensionless power relationships (a relationship between the power number, Reynolds number, Froude number, and bowl fill ratio), which could therefore be used for calculating the power consumption level when the wet mass achieves its target values of density and consistency, i.e., the point at which granulation should be stopped. It was also shown that batches granulated in different conditions (batch size, blade speed) in two planetary mixers, but presenting similar wet mass characteristics (bulk density and consistency) led to dry granules of similar properties: granule size distribution, density, friability, and flow. This work suggests that it is possible to characterize the wet mass by only two parameters which describe the quality of the downstream granules. The scale-up procedure based on the use of dimensionless numbers was found to be applicable to planetary mixers, provided they give one common dimensionless power relationship.
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Taylor LS, York P. Effect of particle size and temperature on the dehydration kinetics of trehalose dihydrate. Int J Pharm 1998. [DOI: 10.1016/s0378-5173(98)00065-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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