The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
Bruno Konrad Radatus - One of the best experts on this subject based on the ideXlab platform.
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Polymorphic Behavior and Crystal Habit of an Anti-Viral/HIV Drug: Stavudine
Crystal Growth & Design, 2006Co-Authors: Mahmoud Mirmehrabi, Sohrab Rohani, Keshava Murthy, Bruno Konrad RadatusAbstract:Different characterization methods (optical microscopy, Karl Ficher titration (KF), XRPD, and solid-state FTIR) were used to identify the two polymorphs and one hydrate of stavudine. The two forms are monotropically related, and form 1 is the stable polymorph. The effects of solvent, impurities, supersaturation, and mixing on the polymorphic occurrence of stavudine are investigated in detail. Hydrogen bonding analysis is employed to qualitatively predict the role of the solvent and structurally related impurities (thymine and thymidine) on polymorphism and Crystal Habit of stavudine Crystals. The impurities showed significant changes in the Crystal Habit and Crystal bulk density of stavudine but had no influence on the polymorphic structure. Depending on the degree of supersaturation at T = 25 °C, a specific polymorph or a mixture of forms 1 and 2 was obtained concomitantly.
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polymorphic behavior and Crystal Habit of an anti viral hiv drug stavudine
Crystal Growth & Design, 2006Co-Authors: Mahmoud Mirmehrabi, Sohrab Rohani, Keshava Murthy, Bruno Konrad RadatusAbstract:Different characterization methods (optical microscopy, Karl Ficher titration (KF), XRPD, and solid-state FTIR) were used to identify the two polymorphs and one hydrate of stavudine. The two forms are monotropically related, and form 1 is the stable polymorph. The effects of solvent, impurities, supersaturation, and mixing on the polymorphic occurrence of stavudine are investigated in detail. Hydrogen bonding analysis is employed to qualitatively predict the role of the solvent and structurally related impurities (thymine and thymidine) on polymorphism and Crystal Habit of stavudine Crystals. The impurities showed significant changes in the Crystal Habit and Crystal bulk density of stavudine but had no influence on the polymorphic structure. Depending on the degree of supersaturation at T = 25 °C, a specific polymorph or a mixture of forms 1 and 2 was obtained concomitantly.
Mahmoud Mirmehrabi - One of the best experts on this subject based on the ideXlab platform.
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Polymorphic Behavior and Crystal Habit of an Anti-Viral/HIV Drug: Stavudine
Crystal Growth & Design, 2006Co-Authors: Mahmoud Mirmehrabi, Sohrab Rohani, Keshava Murthy, Bruno Konrad RadatusAbstract:Different characterization methods (optical microscopy, Karl Ficher titration (KF), XRPD, and solid-state FTIR) were used to identify the two polymorphs and one hydrate of stavudine. The two forms are monotropically related, and form 1 is the stable polymorph. The effects of solvent, impurities, supersaturation, and mixing on the polymorphic occurrence of stavudine are investigated in detail. Hydrogen bonding analysis is employed to qualitatively predict the role of the solvent and structurally related impurities (thymine and thymidine) on polymorphism and Crystal Habit of stavudine Crystals. The impurities showed significant changes in the Crystal Habit and Crystal bulk density of stavudine but had no influence on the polymorphic structure. Depending on the degree of supersaturation at T = 25 °C, a specific polymorph or a mixture of forms 1 and 2 was obtained concomitantly.
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polymorphic behavior and Crystal Habit of an anti viral hiv drug stavudine
Crystal Growth & Design, 2006Co-Authors: Mahmoud Mirmehrabi, Sohrab Rohani, Keshava Murthy, Bruno Konrad RadatusAbstract:Different characterization methods (optical microscopy, Karl Ficher titration (KF), XRPD, and solid-state FTIR) were used to identify the two polymorphs and one hydrate of stavudine. The two forms are monotropically related, and form 1 is the stable polymorph. The effects of solvent, impurities, supersaturation, and mixing on the polymorphic occurrence of stavudine are investigated in detail. Hydrogen bonding analysis is employed to qualitatively predict the role of the solvent and structurally related impurities (thymine and thymidine) on polymorphism and Crystal Habit of stavudine Crystals. The impurities showed significant changes in the Crystal Habit and Crystal bulk density of stavudine but had no influence on the polymorphic structure. Depending on the degree of supersaturation at T = 25 °C, a specific polymorph or a mixture of forms 1 and 2 was obtained concomitantly.
Ashok K. Tiwary - One of the best experts on this subject based on the ideXlab platform.
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Modification of Crystal Habit and its role in dosage form performance.
Drug development and industrial pharmacy, 2001Co-Authors: Ashok K. TiwaryAbstract:Crystallization is often employed for purifying a drug substance. Use of different solvents and processing conditions may change the Crystal Habit, besides altering the polymorphic state. Furthermore, altered Habit may result from Crystal growth during storage. Hence, there is a need to understand the factors influencing Crystal Habit and to evaluate critically its role in the performance of dosage forms. Establishing the physicotechnical properties of different Habits of a drug will help to recognize lot-to-lot variations in raw materials and to ensure reproducibility of dosage form performance.
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Enhanced Suspension Stability : Choice Of Crystal Habit
Indian Journal of Pharmaceutical Sciences, 2000Co-Authors: Ashok K. Tiwary, Gopal M. PanpaliaAbstract:It is well established that the polymorphic state of a solid can modify physicochemical properties and suspension stability of drugs. However, not much attention has been paid towards Crystal Habit, the other seemingly trivial property of a Crystalline solid. This study reveals that different Habits of sulphamethoxazole belonging to the same polymorphic state can be obtained by varying the Crystallization conditions, normally associated with preparation of different polymorphs. This implies that the same polymorphic form can exist in different Habits. The selected Habits were found to differ significantly with respect to shape parameters, bulk density and dissolution rate. The suspension formulations containing these Habits exhibited significantly different physical stability than that formulated with the parent drug material. However, due to insignificant difference in I”H1,value of the Crystals and inherent nature to be rapidly absorbeds the Ka,Tmax and extent of free as well as acetylated sulphamethoxazole excreted were not significantly altered.
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Influence of Crystal Habit on trimethoprim suspension formulation.
Pharmaceutical research, 1999Co-Authors: Ashok K. Tiwary, Gopal M. PanpaliaAbstract:Purpose. The role of Crystal Habit in influencing the physical stability and pharmacokinetics of trimethoprim suspensions was examined.
Manfred Wendisch - One of the best experts on this subject based on the ideXlab platform.
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effects of ice Crystal Habit on thermal infrared radiative properties and forcing of cirrus
Journal of Geophysical Research, 2007Co-Authors: Ping Yang, Manfred Wendisch, Peter PilewskieAbstract:[1] The impact of assumed ice Crystal morphology on thermal infrared (IR) radiative properties of subtropical cirrus is quantified. In particular, the Crystal-shape-dependent profiles of downwelling and upwelling thermal IR (broadband and spectral) irradiances and the radiative forcing of cirrus (at the top and bottom of the atmosphere) are investigated. For this purpose, airborne measurements of ice Crystal size distribution (in terms of ice Crystal maximum dimension) from the Crystal-FACE campaign and a recently published library of thermal IR optical properties of nonspherical ice Crystal Habits are implemented into radiative transfer simulations. Two cirrus cases are studied in detail: (1) a high (cold) cirrus with small optical thickness (� 1 at 10.8 mm wavelength) and (2) a lower (warmer) cirrus of relatively large optical thickness (� 7). The relative effects of ice Crystal shape on thermal IR irradiance are substantial for the high, optically thin cirrus (up to 70%). Spectrally, the largest effects of ice Crystal shape are identified in the atmospheric window spanning from 8 to 12 mm wavelengths, especially for the upwelling irradiance above the cirrus. For the low cirrus of large optical thickness the thermal IR irradiance is only slightly sensitive to ice Crystal Habit (less than 15–20%). Within the major gas absorption bands the thermal IR radiation is essentially insensitive to ice Crystal shape. Furthermore, it is concluded that the thermal IR radiative forcing at the top of the atmosphere contains significant ice Crystal shape dependence for the high cirrus case.
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Impact of Crystal Habit on Cirrus Radiative Properties
Fourier Transform Spectroscopy Hyperspectral Imaging and Sounding of the Environment, 2007Co-Authors: Manfred Wendisch, Ping Yang, Peter PilewskieAbstract:The impact of assumed ice Crystal morphology of subtropical cirrus on the solar and thermal infrared (IR) radiative field above, within, and below the cirrus is quantified. For this purpose airborne measurements of ice Crystal size distribution from the Crystal-FACE campaign and a library of optical properties of nonspherical ice Crystal Habits are implemented into radiative transfer simulations.Two cirrus cases are studied in detail: a high (cold) cirrus cloud with small visible optical thickness (τ≈1), and a lower (warmer) cirrus cloud of relatively large visible optical thickness (τ≈7). For t+he solar wavelength range the impact of shape characteristics of the Crystals was important for the reflected irradiance above the optically thin cirrus, especially for small solar zenith angles. In this case single-scattering dominated the solar radiation field. For the cirrus of large visible optical thickness the enhanced multiple scattering tended to diminish particular shape features in solar radiation caused by nonspherical single-scattering.The relative effects of ice Crystal shape on thermal IR irradiance are substantial for the high, optically thin cirrus (up to 70%). Spectrally, the largest effects of ice Crystal shape are identified in the atmospheric window (8 to 12 μm wavelength), especially for the upwelling irradiance above the cirrus.For the low cirrus of large visible optical thickness the thermal IR irradiance is only slightly sensitive to ice Crystal Habit (less than 15-20%).
Sohrab Rohani - One of the best experts on this subject based on the ideXlab platform.
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Polymorphic Behavior and Crystal Habit of an Anti-Viral/HIV Drug: Stavudine
Crystal Growth & Design, 2006Co-Authors: Mahmoud Mirmehrabi, Sohrab Rohani, Keshava Murthy, Bruno Konrad RadatusAbstract:Different characterization methods (optical microscopy, Karl Ficher titration (KF), XRPD, and solid-state FTIR) were used to identify the two polymorphs and one hydrate of stavudine. The two forms are monotropically related, and form 1 is the stable polymorph. The effects of solvent, impurities, supersaturation, and mixing on the polymorphic occurrence of stavudine are investigated in detail. Hydrogen bonding analysis is employed to qualitatively predict the role of the solvent and structurally related impurities (thymine and thymidine) on polymorphism and Crystal Habit of stavudine Crystals. The impurities showed significant changes in the Crystal Habit and Crystal bulk density of stavudine but had no influence on the polymorphic structure. Depending on the degree of supersaturation at T = 25 °C, a specific polymorph or a mixture of forms 1 and 2 was obtained concomitantly.
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polymorphic behavior and Crystal Habit of an anti viral hiv drug stavudine
Crystal Growth & Design, 2006Co-Authors: Mahmoud Mirmehrabi, Sohrab Rohani, Keshava Murthy, Bruno Konrad RadatusAbstract:Different characterization methods (optical microscopy, Karl Ficher titration (KF), XRPD, and solid-state FTIR) were used to identify the two polymorphs and one hydrate of stavudine. The two forms are monotropically related, and form 1 is the stable polymorph. The effects of solvent, impurities, supersaturation, and mixing on the polymorphic occurrence of stavudine are investigated in detail. Hydrogen bonding analysis is employed to qualitatively predict the role of the solvent and structurally related impurities (thymine and thymidine) on polymorphism and Crystal Habit of stavudine Crystals. The impurities showed significant changes in the Crystal Habit and Crystal bulk density of stavudine but had no influence on the polymorphic structure. Depending on the degree of supersaturation at T = 25 °C, a specific polymorph or a mixture of forms 1 and 2 was obtained concomitantly.