Relevant bibliographies by topics / Amorphous and Crystalline Forms of Drug

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  1. Journal articles
  2. Dissertations / Theses
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  4. Book chapters
  5. Conference papers

Academic literature on the topic 'Amorphous and Crystalline Forms of Drug'

Author: Grafiati
Published: 4 June 2021
Last updated: 3 February 2022

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Journal articles on the topic "Amorphous and Crystalline Forms of Drug"

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Kissi, Eric Ofosu, Keyoomars Khorami, and Thomas Rades. "Determination of Stable Co-Amorphous Drug–Drug Ratios from the Eutectic Behavior of Crystalline Physical Mixtures." Pharmaceutics 11, no. 12 (November 24, 2019): 628. http://dx.doi.org/10.3390/pharmaceutics11120628.

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Co-amorphous drug–drug systems have been developed with the overall aim of improving the physical stability of two or more amorphous drugs. Co-amorphous systems often show good physical stability, and higher solubility and dissolution rates compared to their crystalline counterparts. The aim of this study is to determine if eutectic mixtures of two drugs can form stable co-amorphous systems. Three drug–drug mixtures, indomethacin–naproxen (IND−NAP), nifedipine–paracetamol (NIF−PAR), and paracetamol–celecoxib (PAR−CCX), were investigated for their eutectic and co-amorphization behavior as well as their physical stability in the co-amorphous form. The phase diagrams of the crystalline mixtures and the thermal behavior of the co-amorphous systems were analyzed by differential scanning calorimetry. The solid-state form and physical stability of the co-amorphous systems were analyzed using X-ray powder diffractometry during storage at room temperature at dry conditions. Initial eutectic screening using nifedipine (NIF), paracetamol (PAR), and celecoxib (CCX) indicated that IND−NAP, NIF−PAR, and PAR−CCX can form eutectic mixtures. Phase diagrams were then constructed using theoretical and experimental values. These systems, at different drug-to-drug ratios, were melted and cooled to form binary mixtures. Most mixtures were found to be co-amorphous systems, as they were amorphous and exhibited a single glass transition temperature. The stability study of the co-amorphous systems indicated differences in their physical stability. Comparing the phase diagrams with the physical stability of the co-amorphous mixtures, it was evident that the respective drug–drug ratio that forms the eutectic point also forms the most stable co-amorphous system. The eutectic behavior of drug–drug systems can thus be used to predict drug ratios that form the most stable co-amorphous systems.
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Webster, Gregory K., Cynthia A. Pommerening, Whitney W. Harman, Mathew A. Gragg, Jian-Hwa Han, and Daniel J. Taylor. "Exploiting Kinetic Solubility Differences for Low Level Detection of Crystallinity in Amorphous Drug Formulations." Current Pharmaceutical Analysis 16, no. 5 (June 15, 2020): 529–38. http://dx.doi.org/10.2174/1573412915666181210144338.

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Background: Enabling formulations have been implemented by the pharmaceutical industry as an effective tool for keeping Active Pharmaceutical Ingredient (API) in an amorphous state. Upon dosing in the amorphous state, many drugs which fail to demonstrate bioactivity due to the limited solubility and bioavailability of their crystalline form become bioavailable. Purpose: The analytical techniques use today for crystallinity detection are challenged by the sensitivity and robustness needed to achieve a 5% quantitation limit in low dose drug products. Our laboratory has developed a novel procedure capable of meeting this sensitivity and selectivity requirement. This is achieved by exploiting the differences in kinetic solubility of the formulated amorphous and free crystalline forms of API currently being used in dosage form platforms. Methods: Representative amorphous drug formulations were prepared and spiked with varying levels of crystalline drug substances to evaluate the selectivity and recovery of the crystalline drug substance from the product formulation. Kinetic solubility testing using a (i) Particle wetting phase, (ii) Particle suspending/erosion phase, (iii) Sampling time point and (iv) A total recovery determination for the drug substance. Results: The method selectively and quantitatively distinguishes crystalline drug substance from amorphous drug substance for samples spiked from 2.5% to 10% of the nominal label concentration of the API in the dosage form matrix. Conclusion: The kinetic solubility approach reported here achieves sensitive crystallinity quantitation for low drug level amorphous drug formulations at levels not yet achieved by complimentary analytical techniques.
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Cheung, Eugene, Maxwell Terban, Simon Billinge, Paul Krolikowski, and Steve Hollis. "Recrystallization behavior of amorphous and crystalline lactose from TSPDF." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C864. http://dx.doi.org/10.1107/s2053273314091359.

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Lactose is a disaccharide sugar of galactose and glucose that is most commonly associated with milk. Its importance to the food and animal product industry cannot be overstated, as it is involved in aspects as diverse as baking, confectionary, and infant products. The other major use of lactose is in the pharmaceutical industry. The mildly sweet and loosely bland flavor of lactose has lent to its use as a stabilizer and excipient in pharmaceutical products. Despite the wide range of applications for this material, there is still much to be studied. While it is known to exist in several crystalline forms and as two anomers, α and β, characterized by the flipping of a hydroxide group on the glucose ring, the amorphous form of lactose is less understood. Yet it is this amorphous form which may play a crucial role in the physicochemical stability of amorphous drug dispersions. In order to fully understand the structural changes which lactose undergoes when converted from a crystalline to amorphous material, total scattering experiments coupled with PDF analysis for structural identification of amorphous lactose of different origins were undertaken with the goal of understanding the recrystallization behavior of this versatile material. Samples measured included commercial forms of lactose, crystalline and amorphous, and amorphous forms obtained by melt quenching and lyophilization. Recrystallization was followed for the amorphous forms by measuring characteristic samples aged at 400C/75% RH, which is a standard condition for stressing pharmaceutical materials to extrapolate shelf-life. By fitting the PDF curves to a structural model of lactose, and refining with the characteristic function for a sphere of radius r, an estimate of the coherence length of atom-atom correlations for a give sample provides a measure of the growth progression, from single molecule to crystallite for the lactose samples. Coupled with data from NMR spectroscopy, TSPDF analysis is teasing out the nuances of the recrystallization behavior of lactose.
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Matzger, Adam J., Kuthuru Suresh, Vilmalí López-Mejías, Saikat Roy, and Daniel F. Camacho. "Leveraging Framework Instability: A Journey from Energy Storage to Drug Delivery." Synlett 31, no. 16 (June 18, 2020): 1573–80. http://dx.doi.org/10.1055/s-0040-1707139.

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Amorphous pharmaceuticals often suffer from poor physical stability, which can negate their high solubility, fast dissolution rate, and better oral bioavailability vs. crystalline forms. This represents a major hurdle to processing, storage, and delivery of amorphous pharmaceuticals. Several approaches to addressing these problems have been pursued, but there is still a need for a general method for stabilizing the amorphous form. We describe a novel approach using a water-unstable metal-organic framework as a drug delivery vehicle that demonstrates improved amorphous form stability accompanied by remarkably enhanced solubility and a fast dissolution rate. This research project spanned eleven years from conception to realization and dissemination. With origins in understanding the stability or porous solids for energy storage materials, the work also highlights potential of basic science understanding to illuminate new areas of application.
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Hancock, Bruno C., Glenn T. Carlson, Dauda D. Ladipo, Beth A. Langdon, and Matthew P. Mullarney. "Comparison of the mechanical properties of the crystalline and amorphous forms of a drug substance." International Journal of Pharmaceutics 241, no. 1 (July 2002): 73–85. http://dx.doi.org/10.1016/s0378-5173(02)00133-3.

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Puri, Vibha, Ajay K. Dantuluri, Mahesh Kumar, N. Karar, and Arvind K. Bansal. "Wettability and surface chemistry of crystalline and amorphous forms of a poorly water soluble drug." European Journal of Pharmaceutical Sciences 40, no. 2 (May 2010): 84–93. http://dx.doi.org/10.1016/j.ejps.2010.03.003.

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Sip, Szymon, Natalia Rosiak, Andrzej Miklaszewski, Patrycja Talarska, Ewa Dudziec, and Judyta Cielecka-Piontek. "Amorphous Form of Carvedilol Phosphate—The Case of Divergent Properties." Molecules 26, no. 17 (September 1, 2021): 5318. http://dx.doi.org/10.3390/molecules26175318.

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The amorphous form of carvedilol phosphate (CVD) was obtained as a result of grinding. The identity of the obtained amorphous form was confirmed by powder X-ray diffraction (PXRD), different scanning calorimetry (DSC), and FT-IR spectroscopy. The process was optimized in order to obtain the appropriate efficiency and time. The crystalline form of CVD was used as the reference standard. Solid dispersions of crystalline and amorphous CVD forms with hydrophilic polymers (hydroxypropyl-β-cyclodextrin, Pluronic® F-127, and Soluplus®) were obtained. Their solubility at pH 1.2 and 6.8 was carried out, as well as their permeation through a model system of biological membranes suitable for the gastrointestinal tract (PAMPA-GIT) was established. The influence of selected polymers on CVD properties was defined for the amorphous form regarding the crystalline form of CVD. As a result of grinding (four milling cycles lasting 15 min with 5 min breaks), amorphous CVD was obtained. Its presence was confirmed by the “halo effect” on the diffraction patterns, the disappearance of the peak at 160.5 °C in the thermograms, and the changes in position/disappearance of many characteristic bands on the FT-IR spectra. As a result of changes in the CVD structure, its lower solubility at pH 1.2 and pH 6.8 was noted. While the amorphous dispersions of CVD, especially with Pluronic® F-127, achieved better solubility than combinations of crystalline forms with excipients. Using the PAMPA-GIT model, amorphous CVD was assessed as high permeable (Papp > 1 × 10−6 cm/s), similarly with its amorphous dispersions with excipients (hydroxypropyl-β-cyclodextrin, Pluronic® F-127, and Soluplus®), although in their cases, the values of apparent constants permeability were decreased.
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Mudie, Deanna M., Aaron M. Stewart, Jesus A. Rosales, Nishant Biswas, Molly S. Adam, Adam Smith, Christopher D. Craig, Michael M. Morgen, and David T. Vodak. "Amorphous Solid Dispersion Tablets Overcome Acalabrutinib pH Effect in Dogs." Pharmaceutics 13, no. 4 (April 15, 2021): 557. http://dx.doi.org/10.3390/pharmaceutics13040557.

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Calquence® (crystalline acalabrutinib), a commercially marketed tyrosine kinase inhibitor (TKI), exhibits significantly reduced oral exposure when taken with acid-reducing agents (ARAs) due to the low solubility of the weakly basic drug at elevated gastric pH. These drug–drug interactions (DDIs) negatively impact patient treatment and quality of life due to the strict dosing regimens required. In this study, reduced plasma drug exposure at high gastric pH was overcome using a spray-dried amorphous solid dispersion (ASD) comprising 50% acalabrutinib and 50% hydroxypropyl methylcellulose acetate succinate (HPMCAS, H grade) formulated as an immediate-release (IR) tablet. ASD tablets achieved similar area under the plasma drug concentration–time curve (AUC) at low and high gastric pH and outperformed Calquence capsules 2.4-fold at high gastric pH in beagle dogs. In vitro multicompartment dissolution testing conducted a priori to the in vivo study successfully predicted the improved formulation performance. In addition, ASD tablets were 60% smaller than Calquence capsules and demonstrated good laboratory-scale manufacturability, physical stability, and chemical stability. ASD dosage forms are attractive for improving patient compliance and the efficacy of acalabrutinib and other weakly basic drugs that have pH-dependent absorption.
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Manogna, Katta, P. Nagaveni, and K. Thyagaraju. "Enhancement of solubility of poorly soluble drugs by solid dispersion: An Overview." Indian Journal of Pharmaceutical and Biological Research 5, no. 04 (December 31, 2017): 17–23. http://dx.doi.org/10.30750/ijpbr.5.4.4.

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Most of the newly invented chemical drug moieties are poorly water soluble. According to BCS classification, class II and IV drugs are considered as poorly water soluble. So enhancement of oral absorption and bioavailability of solid dosage forms remains a challenge to formulation scientists due to their solubility criteria. Therefore many techniques are being explored to enhance the solubility of poor soluble drugs. Solid dispersion is one of the most important method for enhance the solubility (dissolution rate) and hence oral bioavailability of poorly soluble drugs. In solid dispersion the particle size of drug is reduced or a crystalline pure drug is converted into amorphous form and hence the solubility is increased. Polymer incorporating in solid dispersion technology is usually hydrophilic in nature and also showing compatibility with the drug to enhance the drug solubility. This review mainly discus about solid dispersion, preparation methods, and finally characterization.
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Talaczyńska, Alicja, Kornelia Lewandowska, Anna Jelińska, Piotr Garbacki, Agnieszka Podborska, Przemysław Zalewski, Irena Oszczapowicz, Adam Sikora, Maciej Kozak, and Judyta Cielecka-Piontek. "Application of Vibrational Spectroscopy Supported by Theoretical Calculations in Identification of Amorphous and Crystalline Forms of Cefuroxime Axetil." Scientific World Journal 2015 (2015): 1–8. http://dx.doi.org/10.1155/2015/921049.

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FT-IR and Raman scattering spectra of cefuroxime axetil were proposed for identification studies of its crystalline and amorphous forms. An analysis of experimental spectra was supported by quantum-chemical calculations performed with the use of B3LYP functional and 6-31G(d,p) as a basis set. The geometric structure of a cefuroxime axetil molecule, HOMO and LUMO orbitals, and molecular electrostatic potential were also determined by using DFT (density functional theory). The benefits of applying FT-IR and Raman scattering spectroscopy for characterization of drug subjected to degradation were discussed.
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Dissertations / Theses on the topic "Amorphous and Crystalline Forms of Drug"

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Avala, Usha Kranthi. "Ionic Conductivity in Non-Ionic Compounds." TopSCHOLAR®, 2013. http://digitalcommons.wku.edu/theses/1279.

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The main objective of this work is to investigate the ionic conductivity of the drugs under certain conditions and also to compare the ionic conductivities of drugs determined by single surface sensors and parallel plate sensors. The ionic conductivity of various materials at their pre-melt and melt states are studied in order to further study a recently discovered phenomenon. Polar solids like Lidocaine, Ketoconazole, Procainamide and Nifedipine were examined in this study. Experimental studies show an increase in ionic conductivity in both pre-melt (20 -30 °C below melting temperature) and melt transition regions. Results of ionic conductivity of both parallel plate and single surface sensor at different frequencies are compared. At 1000 Hz, all the samples show an increase in ionic conductivity with both parallel plate and single surface sensor, but at 0.1 Hz frequency, no increase in ionic conductivity is observed with parallel plate sensor except for Nifedipine.
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Daisenberger, D. "Transformations among metastable amorphous and crystalline forms of silicon." Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1301773/.

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This thesis presents experimental and theoretical investigations of two metastable forms of silicon: amorphous silicon and hypothetical clathrate Si46. Amorphous silicon was investigated at room temperature and high pressure by diamond anvil cell Raman scattering, synchrotron x-ray scattering and electrical resistance measurements. The Raman data provide the first direct evidence for a reversible room temperature high pressure low-density to high-density polyamorphic transition in silicon. This transition is also observed by high pressure x-ray scattering. The combined data suggest that the high-density amorphous silicon network is of significantly higher mean coordination number than the familiar tetrahedrally bonded semiconducting low-density amorphous modification of silicon. Complimentary electrical resistance measurements conducted in a diamond anvil cell also suggest that the high-density amorphous modification is metallic. Amorphous silicon at high pressure was also investigated by molecular dynamics simulations conducted with the Stillinger-Weber potential. According to the simulations low-density amorphous silicon networks first become more defective under compression before transforming to a distinct high-density amorphous network. The changes in the simulated Raman spectra and x-ray structure factors across the transition to the distinct high-density amorphous network resemble those observed in the experimental data, again suggesting that the polyamorphic transition in silicon involves significant changes in the local structure of the amorphous network. Si46, a hypothetical metastable crystalline form of silicon, was also investigated by molecular dynamics simulations conducted with the Stillinger-Weber potential. In agreement with previous simulations the Stillinger-Weber potential predicts that Si46 is of slightly higher energy than related silicon clathrate Si136, although the energy difference between these two structures is much smaller according to the Stillinger- Weber potential than in other calculations. The simulations also show that Si46 melts at slightly lower temperature than Si136 at positive pressures but that its melting point becomes equal to that of Si136 at negative pressures.
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Mesallati, H., A. Umerska, Krzysztof J. Paluch, and L. Tajber. "Amorphous polymeric drug salts as ionic solid dispersion forms of ciprofloxacin." 2017. http://hdl.handle.net/10454/12180.

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Ciprofloxacin (CIP) is a poorly soluble drug that also displays poor permeability. Attempts to improve the solubility of this drug to date have largely focused on the formation of crystalline salts and metal complexes. The aim of this study was to prepare amorphous solid dispersions (ASDs) by ball milling CIP with various polymers. Following examination of their solid state characteristics and physical stability, the solubility advantage of these ASDs was studied, and their permeability was investigated via parallel artificial membrane permeability assay (PAMPA). Finally, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the ASDs were compared to those of CIP. It was discovered that acidic polymers, such as Eudragit L100, Eudragit L100C==, Carbopol and HPMCAS, were necessary for the amorphization of CIP. In each case, the positively charged secondary amine of CIP was found to interact with carboxylate groups in the polymers, forming amorphous polymeric drug salts. Although the ASDs began to crystallize within days under accelerated stability conditions, they remained fully XCray amorphous following exposure to 90% RH at 25 oC, and demonstrated higher than predicted glass transition temperatures. The solubility of CIP in water and simulated intestinal fluid was also increased by all of the ASDs studied. Unlike a number of other solubility enhancing formulations, the ASDs did not decrease the permeability of the drug. Similarly, no decrease in antibiotic efficacy was observed, and significant improvements in the MIC and MBC of CIP were obtained with ASDs containing HPMCASC") and HPMCASCMG. Therefore, ASDs may be a viable alternative for formulating CIP with improved solubility, bioavailability and antimicrobial activity.
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Books on the topic "Amorphous and Crystalline Forms of Drug"

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Tiwari, Sandip. Phase transitions and their devices. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198759874.003.0004.

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Phase transitions as a collective response of an ensemble, with appearance of unique stable properties spontaneously, is critical to a variety of devices: electronic, magnetic, optical, and their coupled forms. This chapter starts with a discussion of broken symmetry and its manifestation in the property changes in thermodynamic phase transition and the Landau mean-field articulation. It then follows it with an exploration of different phenomena and their use in devices. The first is ferroelectricity—spontaneous electric polarization—and its use in ferroelectric memories. Electron correlation effects are explored, and then conductivity transition from electron-electron and electron-phonon coupling and its use in novel memory and device forms. This is followed by development of an understanding of spin correlations and interactions and magnetism—spontaneous magnetic polarization. The use and manipulation of the magnetic phase transition in disk drives, magnetic and spin-torque memory as well as their stability is explored. Finally, as a fourth example, amorphous-crystalline structural transition in optical, electronic, and optoelectronic form are analyzed. This latter’s application include disk drives and resistive memories in the form of phase-change as well as those with electochemical transport.
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Book chapters on the topic "Amorphous and Crystalline Forms of Drug"

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Zhou, Yibo, Vladimir Kolesnichenko, Louis Messerle, Selim Alayoglu, and Bryan Eichhorn. "Crystalline and Amorphous Forms of Tungsten Tetrachloride." In Inorganic Syntheses: Volume 36, 30–34. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2014. http://dx.doi.org/10.1002/9781118744994.ch06.

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Zhou, Yibo, Vladimir Kolesnichenko, Louis Messerle, Selim Alayoglu, and Bryan Eichhorn. "Crystalline and Amorphous Forms of Tungsten Tetrachloride." In Inorganic Syntheses: Volume 36, 30–34. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2014. http://dx.doi.org/10.1002/9781118744994.ch6.

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Ahluwalia, Gurinder Kaur. "Fundamentals of Chalcogenides in Crystalline, Amorphous, and Nanocrystalline Forms." In Applications of Chalcogenides: S, Se, and Te, 3–60. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-41190-3_1.

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Zhang, G. G. Z., and D. Zhou. "Crystalline and Amorphous Solids." In Developing Solid Oral Dosage Forms, 23–57. Elsevier, 2017. http://dx.doi.org/10.1016/b978-0-12-802447-8.00002-9.

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Zhang, Geoff G. Z., and Deliang Zhou. "Crystalline and Amorphous Solids." In Developing Solid Oral Dosage Forms, 25–60. Elsevier, 2009. http://dx.doi.org/10.1016/b978-0-444-53242-8.00002-3.

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"Alteration of the Solid State of the Drug Substance: Polymorphs, Solvates, and Amorphous Forms." In Water-Insoluble Drug Formulation, 545–88. CRC Press, 2000. http://dx.doi.org/10.1201/9781420026054-20.

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Chavan, Rahul B., Balvant Yadav, Anurag Lodagekar, and Nalini R. Shastri. "Multicomponent Solid Forms." In Multifunctional Nanocarriers for Contemporary Healthcare Applications, 273–300. IGI Global, 2018. http://dx.doi.org/10.4018/978-1-5225-4781-5.ch010.

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Multicomponent systems provide the option of combining drugs at the supramolecular level. Among these, co-crystals have gained a widespread interest in pharmaceutical industry as US Food and Drug Administration (FDA) recently introduced new regulatory guidelines regarding this solid form that is anticipated to expand patent portfolios. Apart from co-crystals, other multi-component adducts such as co-amorphous system and eutectics are also a topic of interest for pharmaceutical researchers as they provide therapeutic advantages along with improved the aqueous solubility, dissolution, and bioavailability of poorly soluble drugs. This chapter provides a brief overview of multicomponent solid forms, their preparation methodologies, characterization, evaluation, biopharmaceutical aspects, scale up issues, and regulatory perspectives related to these solid forms. In addition, a section on future perspectives that sheds light on new therapeutic hybrids deploying drug-drug and drug-neutraceuticals combinations with improved pharmaceutical and biopharmaceutical attributes is also included.
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Chavan, Rahul B., and Nalini R. Shastri. "Overview of Multicomponent Solid Forms." In Alternative Pain Management, 65–102. IGI Global, 2020. http://dx.doi.org/10.4018/978-1-7998-1680-5.ch004.

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Multi-drug therapy involves the simultaneous or sequential administration of two or more drugs with similar or different mechanisms of action and is efficient in combating various ailments such as cancer, diabetes, and rheumatoid arthritis. It has emerged advantageous due to larger therapeutic benefits, an increase in patient compliance, lower administrative costs, and reduced number of prescriptions. In the recent past, the clinical success of the Novartis product Entresto (sacubitril, disodium valsartan and water) and Esteve product E-58425 (tramadol and celecoxib) has boosted the development of multi-drug . The present article is hence designed to provide an overview of different multicomponent addicts which provide option of combining the drugs at a supramolecular level (nano-sized level). Key features of multi-drug cocrystal, co-amorphous system and eutectics are described with major emphasis on screening tools, preparation methods, characterization techniques, biopharmaceutical aspects and scale up.
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Tiwari, Sandip. "Introduction." In Semiconductor Physics, 1–5. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198759867.003.0021.

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Semiconductors, as crystalline, polycrystalline or amorphous inorganic solids, as ordered or disordered organic solids or even in glassy and liquid forms, form a large set of materials useful in active and passive devices. The control of their properties arising in an interaction of particles—atoms, electrons, photons, their elementary one- and many-body excitations, transport and the exchange between different energy forms—has been a fruitful human endeavor since the birth of the transistor, where they found their first large-scale use. Integrated electronics, through its social and commercial informational ubiquity; optoelectronics, through lasers and photovoltaics; and thermoelectronics and magnetoelectronics, with their use in energy transformation and signal detection, are but a few of these gainful uses. Nanoscale, within this milieu, opens up a variety of perturbative and significantly more substantial and sensitive effects. Some are very useful, and some can be quite a bother....
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Lowenstam, Heinz A., and Stephen Weiner. "Mollusca." In On Biomineralization. Oxford University Press, 1989. http://dx.doi.org/10.1093/oso/9780195049770.003.0008.

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Mollusks have a well-deserved reputation for being expert mineralizers based only on their much-admired shell-making abilities. Table 6.1 shows that the reputation is deserved 10-fold as shell formation is just one of many different processes that these animals perform in which biogenic minerals are utilized. The table lists no less than 21 different minerals and about 17 different functions! The list contains both amorphous minerals (amorphous fluorite, calcium carbonate, calcium phosphate, calcium pyrophosphate, and silica) and many crystalline ones, including rather uncommon ones such as weddelite, calcium fluorite, barite, magnetite, lepidocrocite, and goethite. Weddelite, for example, is a calcium oxalate mineral frequently formed pathologically in vertebrates. Certain gastropods use the rather soft weddelite nonpathologically to cap pestlelike objects (gizzard plates) in their stomachs (Lowenstam 1968), which they use for crushing shelled prey. One mollusk, the chambered Nautilus, forms no less than five different minerals. An individual tooth of a chiton contains three different mature minerals that are products of two other transient minerals. In addition to the more familiar functions of mineralized tissues, mollusks use biogenic minerals as buoyancy devices, trap doors, egg shells, and love darts. The varieties of crystal shapes, sizes, organizational arrays, and tissue sites present a picture of overwhelming diversity all within one phylum. It is illustrative to compare the mollusks with the echinoderms. The echinoderms also use minerals for a wide variety of functions, but in contrast to the mollusks they use essentially the same “building material” for many different purposes. Thus, understanding how one echinoderm mineralized tissue forms provides insight into how most of the others form. This is not so with mollusks. It seems futile to expect that they too have adapted one basic process to form all their mineralized tissues. It seems just as futile to look for a different explanation for each type of mineralized product. The mollusks force us to seek a level of understanding of mineralization that identifies common approaches, strategies, and principles and, at the same time, appears to dispel any “dreams” about discovering the mechanism of mineralization. The mollusk phylum contains seven different taxonomic classes.
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Conference papers on the topic "Amorphous and Crystalline Forms of Drug"

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Habib, Khaled J. "Properties and structures of Fe-based metallic thin films in amorphous and crystalline forms (Poster Paper)." In Semiconductors '92, edited by Orest J. Glembocki. SPIE, 1992. http://dx.doi.org/10.1117/12.60440.

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Li, Ruihua, and Donggang Yao. "Manufacturing of Single Poly(Lactic Acid) Composites." In ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-15268.

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An approach of utilizing slowly crystallizing dynamics for fabrication of poly(lactic acid) (PLA) single-polymer composites (SPCs) was investigated. As a slowly crystallizing polymer, PLA can be prepared as two distinct physical forms, amorphous (or near-amorphous) PLA and highly crystalline PLA. In this study, near-amorphous PLA films and highly crystalline PLA fibers were combined to form a SPC using a rapid hot compaction method at a temperature about 40°C below PLA's melting temperature. It was found that, by rapidly heating an amorphous-crystalline lamination above PLA's glass transition temperature during manufacturing, amorphous films can be fused and good adhesion between the amorphous film and the crystalline fiber can be achieved. Mechanical testing showed that the tearing strength of the SPC is almost half an order higher that that of the original PLA film.
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Jiang, W., A. Bakken, and R. P. Taleyarkhan. "Irradiation Induced Crosslinking in “Green” Polylactic-Acid (PLA) Polymers for Enhanced Strength and Elevated Temperature Applications." In 2020 International Conference on Nuclear Engineering collocated with the ASME 2020 Power Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/icone2020-16767.

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Abstract This paper presents interdisciplinary (nuclear-mechanical-materials-chemical) engineering technology and results pertaining to use of ionization radiation for tailoring “green”, renewable corn-soy based amorphous and crystalline form polymers for use as low-to-high temperature adhesives. Both amorphous and crystalline form polymer forms of such the Polylactic-Acid (PLA) polymer were studied with and without photon irradiation, alongside with and without cross-linking agent. In order to study and enhance the high-temperature application of PLA as a novel, multi-purpose adhesive, small concentrations of the crosslinking agent triallyl isocyanurate (TAIC) were included into molten amorphous and semi-crystalline PLA cast as glue sticks, followed with Co-60 gamma-irradiation. Bond strength variations were studied in tensile mode at room temperature using the resulting adhesive in between two steel dowels (head-to-head bonded) as well as via shear strength testing at elevated temperatures (50–120°C) under a set pre-load of 222 N. It was found that gamma irradiated samples with TAIC exhibited noticeably improved bonding strength, and importantly, such strength can potentially prevail towards 100°C. These are exciting results which offer potential for application for building construction and safety enhancements especially under fires and similar accidents. Samples without TAIC exhibited significant loss of strength past 90°C. The full paper will discuss details of apparatus, modeling and simulation of irradiation dose delivery, testing protocols results, and future enhancements via hybrid neutron-photon-electron irradiation for utility in variety of industrial applications.
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Waltermire, Scott W., Juekuan Yang, Deyu Li, and Terry T. Xu. "Thermal Conductivity of α-Tetragonal Boron Nanoribbons." In ASME 2009 Heat Transfer Summer Conference collocated with the InterPACK09 and 3rd Energy Sustainability Conferences. ASMEDC, 2009. http://dx.doi.org/10.1115/ht2009-88347.

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Elemental boron has many interesting properties, such as high melting point, low density, high hardness, high Young’s modulus, good oxidation resistance, resulting from its complex crystalline structure from its electron-deficient nature. Boron forms complex crystalline structures according to the various arrangements of B12 icosahedra in the lattice, such as α (B12)- and β (B105)-rhombohedral and α (B50)- and β (B196)-tetragonal boron polymorphs, among others. Even though considerable materials research has been conducted over the past half century on boron and boron-based compounds, investigating their unique structures and corresponding properties, our understanding of this complex class of materials is still poor, compared to some other well-studied materials with much simpler structures such as silicon. Thermal transport studies through bulk boron have been performed mainly on β-rhombohedral and amorphous boron, because of the difficulty to grow high quality bulk α-rhombohedral boron samples [1–3]. Some efforts have been made to measure B12As2, B12P2, AlB12 samples that have an α-rhombohedral form [2,3]. There is almost no information available on α-tetragonal boron. However, Slack predicted the thermal conductivity of α-boron should be ∼200 W/m-K at room temperature, which is 1/2 that of copper. Large phonon mean free path has been predicted for α-boron (from ∼200 nm at room temperature to 6 nm at the Debye temperature), which could lead to interesting thermal transport properties for low dimensional boron structures.
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McQueen, Mark T. "Energy and High Surface Area Siliceous Ash From the Combustion of Rice Hulls." In 17th International Conference on Fluidized Bed Combustion. ASMEDC, 2003. http://dx.doi.org/10.1115/fbc2003-018.

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Biomass combustion is an attractive energy production method since it is a zero net emitter of carbon dioxide. Rice hulls are a significant source of biomass fuel: approximately 100Mt of rice hulls are produced yearly from the processing and milling of paddy rice. Previous studies have shown that the ash produced from the combustion of rice hulls possesses pozzolanic properties. When used as a concrete additive, the ash can behave similar to silica fume and improve the strength and porosity of the finished concrete. In such cases, the surface area attributed to the pozzolan is related to the residual carbon content of the ash, which is often well in excess of 5%. The excessive carbon level stems from the awkward geometry of the hulls combined with the low melting point and heat sensitive nature of the ash minerals: these create problems for commercial combustion devices. As a result, the ash produced at these facilities contains either high residual carbon or a high proportion of crystalline silica, both of which renders the ash unattractive for use as a concrete additive. However, if the ash is of sufficient quality to be sold as a concrete additive, the economics of energy generation from the rice hulls can be improved. Test work conducted in Mississauga, Canada has produced an ash with less than 3% residual carbon, and greater than 90% silica, nearly all of which is amorphous. This work was done at temperatures higher than those in conventional operations without significant conversion of the siliceous component from the amorphous state to crystalline forms such as crystobalite or quartz. The key to this unexpected result is an enhanced combustion environment in which the solids residence time at elevated temperatures, and therefore the opportunity for silica phase changes, is minimized. In this instance, the total measured surface area of this ash is lower than that of the other ashes due to the reduced residual carbon content, but the siliceous surface area is equal or greater due to the high amorphous content. Consistent with this fact, the rice hull ash performed well in a number of standard concrete tests, in which the ash replaced 7.5% to 12.5% of the Portland cement for similar water to cement mixture ratios. With proper application of a TORBED process reactor as a combustor, a high value and high surface area siliceous ash can be produced as energy is simultaneously recovered from the system.
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