Artykuły w czasopismach: „Amorphous substances”

1

Antosik, Agata, Joanna Szafraniec, Krzysztof Niwiński i Renata Jachowicz. "Amorphous drug substances". Farmacja Polska 74, nr 11 (30.11.2018): 671–78. http://dx.doi.org/10.32383/farmpol/118638.

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Wang, Bo, i Yuan Ming Song. "Study on the Difference of Amorphous Substances of Coal Ashes". Advanced Materials Research 287-290 (lipiec 2011): 1189–92. http://dx.doi.org/10.4028/www.scientific.net/amr.287-290.1189.

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There is much difference among the amorphous substances of different coal ashes, the important basis for their utilization. The micromorphology and content of the amorphous substances were measured by scanning electron microscopy (SEM) and chemical method respectively, and the 28d compressive strength ratio was also used to characterize their contribution to the cement-coal ashes system. The results show that the amorphous substances of BFBC/CFBC ashes are irregular and loose textured, which are significantly different from those of PC fly ashes that are spherical and compact. The content and the pozzolanic activity of the amorphous substance of BFBC ashes are greater than that of PC fly ashes.

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Shklovskii, V. A., i V. M. Kuz'menko. "Explosive crystallization of amorphous substances". Uspekhi Fizicheskih Nauk 157, nr 2 (1989): 311. http://dx.doi.org/10.3367/ufnr.0157.198902c.0311.

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Shklovskiĭ, V. A., i V. M. Kuz'menko. "Explosive crystallization of amorphous substances". Soviet Physics Uspekhi 32, nr 2 (28.02.1989): 163–80. http://dx.doi.org/10.1070/pu1989v032n02abeh002681.

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Webster, Gregory K., Cynthia A. Pommerening, Whitney W. Harman, Mathew A. Gragg, Jian-Hwa Han i Daniel J. Taylor. "Exploiting Kinetic Solubility Differences for Low Level Detection of Crystallinity in Amorphous Drug Formulations". Current Pharmaceutical Analysis 16, nr 5 (15.06.2020): 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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Sheka, E. F. "Spectroscopy of amorphous substances with molecular structure". Uspekhi Fizicheskih Nauk 160, nr 2 (1990): 263. http://dx.doi.org/10.3367/ufnr.0160.199002c.0263.

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Sheka, E. F. "Spectroscopy of amorphous substances with molecular structure". Soviet Physics Uspekhi 33, nr 2 (28.02.1990): 147–66. http://dx.doi.org/10.1070/pu1990v033n02abeh002546.

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Fratzl, P., G. Vogl i S. Klaumünzer. "Small-angle scattering from porous amorphous substances". Journal of Applied Crystallography 24, nr 5 (1.10.1991): 588–92. http://dx.doi.org/10.1107/s0021889890012225.

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Mikhailov, E., S. Vlasenko, S. T. Martin, T. Koop i U. Pöschl. "Amorphous and crystalline aerosol particles interacting with water vapor – Part 1: Microstructure, phase transitions, hygroscopic growth and kinetic limitations". Atmospheric Chemistry and Physics Discussions 9, nr 2 (20.03.2009): 7333–412. http://dx.doi.org/10.5194/acpd-9-7333-2009.

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Abstract. Interactions with water are crucial for the properties, transformation and climate effects of atmospheric aerosols. Here we outline characteristic features and differences in the interaction of amorphous and crystalline aerosol particles with water vapor. Using a hygroscopicity tandem differential mobility analyzer (H-TDMA), we performed hydration, dehydration and cyclic hydration&dehydration experiments with aerosol particles composed of levoglucosan, oxalic acid and ammonium sulfate (diameters ~100–200 nm, relative uncertainties <0.4%, relative humidities <5% to 95% at 298 K). The measurements and accompanying Köhler model calculations provide new insights into particle microstructure, surface adsorption, bulk absorption, phase transitions and hygroscopic growth. The results of these and related investigations lead to the following main conclusions: 1. Many organic substances (including carboxylic acids, carbohydrates and proteins) tend to form amorphous rather than crystalline phases upon drying of aqueous solution droplets. Depending on viscosity and microstructure, the amorphous phases can be classified as glasses, rubbers, gels or viscous liquids. 2. Amorphous organic substances tend to absorb water vapor and undergo gradual deliquescence and hygroscopic growth at much lower relative humidity than their crystalline counterparts. 3. In the course of hydration and dehydration, certain organic substances can form rubber- or gel-like structures (supra-molecular networks) and undergo stepwise transitions between swollen and collapsed network structures. 4. Organic gels or (semi-)solid amorphous shells (glassy, rubbery, ultra-viscous) with low molecular diffusivity can kinetically limit the uptake and release of water by submicron aerosol particles on (multi-)second time scales, which may influence the hygroscopic growth and activation of aerosol particles as cloud condensation nuclei (CCN) and ice nuclei (IN). 5. The shape and porosity of amorphous and crystalline particles formed upon dehydration of aqueous solution droplets depend on chemical composition and drying conditions. The apparent volume void fractions of particles with highly porous structures can range up to ~50% or more (xerogels, aerogels). Void fractions as well as residual water in dried aerosol particles that are not water-free (due to kinetic limitations of drying or stable hydrate formation) should be taken into account in Köhler model calculations of hygroscopic growth and CCN activation. 6. For efficient description of water uptake and phase transitions of amorphous and crystalline organic and inorganic aerosol particles and particle components, we propose not to limit the terms deliquescence and efflorescence to equilibrium phase transitions of crystalline substances interacting with water vapor. Instead we propose the following generalized definitions: Deliquescence is the transformation of a (semi-)solid substance into a liquid aqueous solution, whereby water is absorbed from the gas phase ("liquefaction upon humidification/hydration"). Efflorescence is the transformation of a substance from a liquid aqueous solution into a (semi-)solid phase, whereby water is evaporated ("solidification upon drying/dehydration"). According to these definitions, individual components as well as entire aerosol particles can undergo gradual or prompt, partial or full deliquescence or efflorescence.

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Shimizu, Y., H. Sogabe i Y. Terashima. "The effects of colloidal humic substances on the movement of non-ionic hydrophobic organic contaminants in groundwater". Water Science and Technology 38, nr 7 (1.10.1998): 159–67. http://dx.doi.org/10.2166/wst.1998.0289.

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A controlled experimental study of the sorption of colloidal humic substances (humic acid) and a non-ionic hydrophobic organic compound (naphthalene) onto typical inorganic constituents of aquifer solids was performed using four types of model solid phases {i.e., individual model solids (montmorillonite, kaolinite, amorphous aluminosilicate gel, and amorphous iron oxides) and combined model solids (montmorillonite coated by amorphous aluminosilicate gel or iron oxides)}, which are synthesized in the laboratory. The batch experimental results indicated that the sorption of non-ionic hydrophobic organic compounds and colloidal humic substances onto the aquifer solids is significantly influenced by the solid composition. And it was also suggested that the non-ionic hydrophobic organic compounds which have greater hydrophobicity are considered to be sorbed and stabilized by the mobile colloidal humic substances in groundwater, and these colloids may act as a third phase that can increase the amount of compounds that the flow of groundwater can transport. On the other hand, the non-ionic hydrophobic organic contaminants of smaller hydrophobicity may be retarded significantly with the sorption of colloidal humic substances onto the aquifer solids.

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Battaglini, Ana Paula Pavão, Alexandre Urbano, Vanerli Beloti, Edson Antonio Rios, Juliana Ramos Pereira i Rafael Fagnani. "X-ray diffraction has limited applicability in investigation of milk tampering". Journal of Dairy Research 86, nr 3 (sierpień 2019): 337–40. http://dx.doi.org/10.1017/s0022029919000566.

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AbstractThe aim of this work was to use X-ray diffraction to identify substances used for adulteration of raw milk and to determine if crystallographic analysis can detect extraneous substances in milk. Two unknown substances were sent anonymously by employers linked to the dairy chain, who claimed that they were added directly in milk prior to water addition by truck drivers. The samples were analyzed by X-ray diffraction and submitted to physicochemical analysis. The first substance was identified by X-ray diffraction as sodium citrate, complying with its physicochemical attributes, such as the powerful ability to decrease the freezing point. The second substance was identified by X-ray diffraction as sucrose and this result was also in agreement with its ability to increase the density, decrease the freezing point and finally, to be positive for sucrose in the resorcinol qualitative test. To evaluate if X-ray diffraction can detect extraneous substances already mixed in milk, fresh raw milk samples tampered with urea, sodium hydroxide, sodium citrate and sucrose were freeze dried and analyzed by X-ray diffraction, with no detection of any extraneous substances at any percentage. This is the first report of attempted diagnosis of extraneous substances in milk by X-ray diffraction. However, this technique can be useful only when applied to identify substances used for adulteration prior to its dilution in milk, since the amorphous nature of milk seems to be a limitation for the accurate detection of extraneous substances.

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Mikhailov, E., S. Vlasenko, S. T. Martin, T. Koop i U. Pöschl. "Amorphous and crystalline aerosol particles interacting with water vapor: conceptual framework and experimental evidence for restructuring, phase transitions and kinetic limitations". Atmospheric Chemistry and Physics 9, nr 24 (16.12.2009): 9491–522. http://dx.doi.org/10.5194/acp-9-9491-2009.

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Abstract. Interactions with water are crucial for the properties, transformation and climate effects of atmospheric aerosols. Here we present a conceptual framework for the interaction of amorphous aerosol particles with water vapor, outlining characteristic features and differences in comparison to crystalline particles. We used a hygroscopicity tandem differential mobility analyzer (H-TDMA) to characterize the hydration and dehydration of crystalline ammonium sulfate, amorphous oxalic acid and amorphous levoglucosan particles (diameter ~100 nm, relative humidity 5–95% at 298 K). The experimental data and accompanying Köhler model calculations provide new insights into particle microstructure, surface adsorption, bulk absorption, phase transitions and hygroscopic growth. The results of these and related investigations lead to the following conclusions: (1) Many organic substances, including carboxylic acids, carbohydrates and proteins, tend to form amorphous rather than crystalline phases upon drying of aqueous solution droplets. Depending on viscosity and microstructure, the amorphous phases can be classified as glasses, rubbers, gels or viscous liquids. (2) Amorphous organic substances tend to absorb water vapor and undergo gradual deliquescence and hygroscopic growth at lower relative humidity than their crystalline counterparts. (3) In the course of hydration and dehydration, certain organic substances can form rubber- or gel-like structures (supramolecular networks) and undergo transitions between swollen and collapsed network structures. (4) Organic gels or (semi-)solid amorphous shells (glassy, rubbery, ultra-viscous) with low molecular diffusivity can kinetically limit the uptake and release of water and may influence the hygroscopic growth and activation of aerosol particles as cloud condensation nuclei (CCN) and ice nuclei (IN). Moreover, (semi-)solid amorphous phases may influence the uptake of gaseous photo-oxidants and the chemical transformation and aging of atmospheric aerosols. (5) The shape and porosity of amorphous and crystalline particles formed upon dehydration of aqueous solution droplets depend on chemical composition and drying conditions. The apparent volume void fractions of particles with highly porous structures can range up to ~50% or more (xerogels, aerogels). (6) For efficient description of water uptake and phase transitions of aerosol particles, we propose not to limit the terms deliquescence and efflorescence to equilibrium phase transitions of crystalline substances. Instead we propose generalized definitions according to which amorphous and crystalline components can undergo gradual or prompt, partial or full deliquescence or efflorescence. We suggest that (semi-)solid amorphous phases may be important not only in the upper atmosphere as suggested in recent studies of glass formation at low temperatures. Depending on relative humidity, (semi-)solid phases and moisture-induced glass transitions may also play a role in gas-particle interactions at ambient temperatures in the lower atmosphere.

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Nozaki, Jorge, Edivaldo Egea Garcia i Joji Suguita. "ADSORPTION OF GASEOUS SUBSTANCES ON CHEMICAL AND ELECTROLYTIC MANGANESE DIOXIDE". SOUTHERN BRAZILIAN JOURNAL OF CHEMISTRY 6, nr 7 (20.12.1998): 7–15. http://dx.doi.org/10.48141/sbjchem.v6.n7.1998.10_1998_2.pdf.

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The adsorption of mercury, arsine, hydrocyanic acid, and hydrogen sulfide on amorphous chemical manganese dioxide (CMD) and electrolytic manganese dioxide (EMD) has been investigated. Variables such as agitation time, pH, temperature, the mass of adsorbent, and concentration of adsorbate were studied. The adsorption process obeys a Freundlich type isotherm over the concentration range investigated. Wads of Lujfa cylindrica Roem were used as a substrate for CMD production. For gaseous substances, this amorphous material showed better sorption capacity than EMD.

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Alexander, Keith, i C. Judson King. "FACTORS GOVERNING SURFACE MORPHOLOGY OF SPRAY-DRIED AMORPHOUS SUBSTANCES". Drying Technology 3, nr 3 (sierpień 1985): 321–48. http://dx.doi.org/10.1080/07373938508916275.

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Sanditov, D. S., i A. A. Mashanov. "On some features of glass transition in amorphous substances". Doklady Physical Chemistry 477, nr 2 (grudzień 2017): 231–34. http://dx.doi.org/10.1134/s0012501617120077.

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Darmaev, Migmar V., Michael I. Ojovan, Alexey A. Mashanov i Timur A. Chimytov. "The Temperature Interval of the Liquid–Glass Transition of Amorphous Polymers and Low Molecular Weight Amorphous Substances". Applied Sciences 13, nr 4 (20.02.2023): 2742. http://dx.doi.org/10.3390/app13042742.

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We present calculation results of the temperature interval δTg characterizing the liquid–glass transition in amorphous materials obtained on the basis of available data of the empirical parameters C1 and C2 in the Williams–Landel–Ferry (WLF) viscosity equation. We consider the unambiguous dependence of the relative transition temperature interval δTg/Tg on the fraction of the fluctuation volume fg frozen at the glass transition temperature Tg utilizing Sanditov’s model of delocalized atoms. The parameter f = ΔVe/V, which determines the molecular mobility characteristic of delocalized atoms in the liquid–glass transition region, is weakly dependent on the nature of most vitreous substances and can be found as fg = 1/C1. We show that the temperature interval δTg is less than 1% of the Tg for most amorphous substances. This result conforms with Simon’s classical idea of a small temperature range in which the structure freezes. The structural relaxation time τg at Tg of polymers and chalcogenide glasses is also calculated.

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Vranić, Edina. "Amorphous Pharmaceutical Solids." Bosnian Journal of Basic Medical Sciences 4, nr 3 (20.08.2004): 35–39. http://dx.doi.org/10.17305/bjbms.2004.3383.

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Amorphous forms are, by definition, non-crystalline materials which possess no long-range order. Their structure can be thought of as being similar to that of a frozen liquid with the thermal fluctuations present in a liquid frozen out, leaving only “static” structural disorder. The amorphous solids have always been an essential part of pharmaceutical research, but the current interest has been raised by two developments: a growing attention to pharmaceutical solids in general, especially polymorphs and solvates and a revived interest in the science of glasses and the glass transition.Amorphous substances may be formed both intentionally and unintentionally during normal pharmaceutical manufactoring operations. The properties of amorphous materials can be exploited to improve the performance of pharmaceutical dosage forms, but these properties can also give rise to unwanted effects that need to be understood and managed in order for the systems to perform as required.

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Abrosimova, G. E., i I. M. Shmytko. "The use of single-crystal cuvettes with the properties of an optical shutter in X-ray diffractometers". Industrial laboratory. Diagnostics of materials 84, nr 6 (1.08.2018): 34–37. http://dx.doi.org/10.26896/1028-6861-2018-84-6-34-37.

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The atomic structure of substances can be studied using X-ray diffraction methods. X-ray diffractometers contains X-ray source and goniometer with a detector of scattered radiation. A sample holder (a cuvette) with the material under study is placed in the center of the goniometer. The diffraction spectrum which represents the structure of the sample under study is recorded upon angular scanning of the sample and detector. Study of crystalline powders, amorphous substances, nanocrystalline and partially crystalline objects is often based on the Bragg-Brentano scheme (θ – 2θ-scanning) with divergent X-ray beams irradiating the entire sample surface. Scattered radiation from the cuvette can also enter the detector and affect the recorded diffraction spectrum. The aforementioned distortion is rather weak for polycrystalline samples due to strong intensity of crystalline reflections. However, when studying amorphous substances, nanocrystalline and partially crystalline objects, contribution of the scattered radiation can be compared with the radiation from the sample and thus interfere with an unambiguous determination of the sample structure. The results of using standard cuvettes for X-ray diffractometers D500, D5000 (Siemens), D8 ADVANCE (Bruker) and DRON are analyzed with a special attention paid to distortion of X-ray spectra attributed to the use of cuvettes made of plastic or amorphous quartz when studying amorphous, nanocrystalline and partially crystalline samples. Special cuvettes, being a kind of optical shutters for background scattering, which do not distort the diffraction spectra of the objects under study are developed: single crystal plates of a special orientation with cylindrical cavities for the samples. The advantages of a single-crystal silicon cuvette compared to plastic cuvette usually supplied for D500 diffractometer are estimated when studying an amorphous sample.

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Harder, D. E., J. Chong, R. Rohringer, K. Mendgen, A. Schneider, K. Welter i G. Knauf. "Ultrastructure and cytochemistry of extramural substances associated with intercellular hyphae of several rust fungi". Canadian Journal of Botany 67, nr 7 (1.07.1989): 2043–51. http://dx.doi.org/10.1139/b89-258.

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Several types of extramural substance(s) associated with rust fungal intercellular hyphae were identified using a variety of tissue processing techniques. With conventional glutaraldehyde–OsO4 fixing and uranyl acetate – lead citrate staining, little material could be discerned on the hyphal surfaces in nonsporulating areas except at locations of cell–cell contact, where a lightly staining fibrous or darker staining amorphous material was apparent. Freeze-substitution or freeze-fracturing preserved greater amounts of coating material, which could be distinguished from the outer fungal wall layers. In freeze-substituted samples the extramural material was amorphous in nonsporulating areas, whereas near sporulating zones it had a fibrous consistency, with the fibrils oriented perpendicularly to the fungal wall. At locations of cell–cell contact there was additional extramural material that was composed of randomly oriented fibrils or was amorphous and densely staining. All types of extramural material stained positively with the periodate – thiocarbahydrazide – silver proteinate or periodate – chromate–phosphotungstate stains, but Concanavalin A bound only to some of the dense amorphous material. Sodium ethoxide etching and platinum–carbon shadowing also revealed the extramural material. When rust-infected wheat leaves were flooded with suspensions of colloidal gold, adhesion of gold particles occurred outside the hyphal walls and coincided with the location of extramural material.

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Siddharatha Dhoppalapudi i Prashanth Parupathi. "Hot melt extrusion: A single-step continuous manufacturing process for developing amorphous solid dispersions of poorly soluble drug substances". GSC Advanced Research and Reviews 13, nr 2 (30.11.2022): 126–35. http://dx.doi.org/10.30574/gscarr.2022.13.2.0311.

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In today’s world with increasing patient population, the demand for pharmaceutical medications is increasing enormously. However, poor solubility of drug substances and underdeveloped manufacturing process are affecting the revenue of the pharmaceutical industries. Improving the solubility and establishing a robust manufacturing process is the primary prerequisite of the developmental scientists. Among various approaches amorphous solid dispersion has gained a tremendous response for improving the solubility of the drug substances. In addition, the process of hot melt extrusion has attracted the investigators from regulatory agencies and industries. The process of hot melt extrusion involves application of thermal and mechanical energy on to the processing material. The process requires no solvent and is referred as “green technique.” Various factors need to be taken into consideration for developing amorph amorphous solid dispersions. The miscibility of drug and polymer, solubility of drug in polymer, drug-polymer interactions, glass transition temperature, storage conditions majorly influence the stability of the amorphous solid dispersions systems. Though hot melt extrusion is most widely employed for developing amorphous solid dispersions still a lot of research is warranted for developing strategies to formulate high drug loading medications with improved stability. This review article mainly focuses on the instrumentation, and process for developing amorphous solid dispersions by hot melt extrusion with a small note on the various advantages and limitations.

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Wang, Xiuteng, Guoliang Liu, Ling Lin, Dongfeng Gao, Jing Liu, Fei Fang i Xiaodong Huo. "Environmental Risk Analysis of Leachable Substances from Vitreous Residue of Solid Wastes Treated by High Temperature Melting". Advances in Engineering Technology Research 4, nr 1 (6.03.2023): 100. http://dx.doi.org/10.56028/aetr.4.1.100.2023.

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High temperature melting is a harmless treatment technology for solid wastes, which is applicable to hazardous wastes containing heavy metals and other harmful substances, obtaining amorphous glassy substances. Vitreous residue usually has high stability and low leaching toxicity. This paper simulates the leaching test of vitreous residue under natural conditions in ordinary rain and acid rain, systematically detects the concentration of leachable substances of typical residue, and analyses its environmental risks according to groundwater quality standards, indicating that harmful substances such as heavy metals may bring potential environmental risks when the vitreous residue enters the environment.

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Golubev, E. A., i O. V. Kovaleva. "Nanostructurization in X-ray amorphous organic substances of geological origin". Russian Journal of General Chemistry 81, nr 6 (czerwiec 2011): 1366–74. http://dx.doi.org/10.1134/s1070363211060417.

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Sanditov, D. S., A. A. Mashanov i M. V. Darmaev. "Energy of Atomic Delocalization and Glass Temperature of Amorphous Substances". Polymer Science, Series A 62, nr 2 (marzec 2020): 79–84. http://dx.doi.org/10.1134/s0965545x20020054.

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Chechetkina, E. A. "Medium-range order in amorphous substances: A modified layer model". Solid State Communications 91, nr 2 (lipiec 1994): 101–4. http://dx.doi.org/10.1016/0038-1098(94)90262-3.

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Akulova, Yu O., N. O. Gonchukova, T. V. Larionova i O. V. Tolochko. "Structural relaxation in amorphous substances with highly non-equilibrium structure". Journal of Non-Crystalline Solids 261, nr 1-3 (styczeń 2000): 252–59. http://dx.doi.org/10.1016/s0022-3093(99)00585-2.

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Li, Z. G., L. Liang, R. L. Harlow, C. M. Foris, R. E. Olson, T. M. Sielecki, J. Liu, R. D. Vickery i M. B. Maurin. "New Applications of Electron Microscopy in Pharmaceuticals: Crystallinity Assessment and Polymorph Determination". Microscopy and Microanalysis 6, S2 (sierpień 2000): 1004–5. http://dx.doi.org/10.1017/s143192760003751x.

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Recently, transmission electron microscopy has been used in crystallinity assessments and unit cell parameter/polymorph determinations in solid drug substances [1,2]. Lumaxis™ (roxifiban) is a glycoprotein nb/ffla (GPHb/HIa) antagonist discovered recently at The DuPont Pharmaceuticals Company [3] currently undergoing clinical evaluation for the treatment of thrombotic disorders. Lumaxis™ is converted in vivo to a zwitterionic active metabolite, XV459. As reported here, we have assessed by electron microscopy and x-ray diffraction the crystallinity of XP280, the benzenesulfonate salt of XV459, and determined the unit cell parameters of SC877, the methanesulfonate salt of the methyl ester of XV459.Crystallinity assessment. Partial or complete transformation of crystalline phases into amorphous phases can occur during production processes that may ultimately affect the activity associated with various batches of a drug [4, 5]. Whether desired or not, the amorphous content of any drug substance is thus an important issue for the pharmaceutical industry.

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Caminiti, Ruggero, Carmen Munoz Roca, Daniel Beltran-Porter i Antonella Rossi. "Amorphous Complexes MM (EDTA) (H2O)4 · 2H2O . LAXS and XPS Investigation of the Local Structure". Zeitschrift für Naturforschung A 43, nr 6 (1.06.1988): 591–96. http://dx.doi.org/10.1515/zna-1988-0610.

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Abstract The amorphous MM (EDTA)(H2O)4·2 H2O (M = Ni,Co) substances are made up of infinite chains of alternating "hydrated" and "chelated" octahedra bridged by carboxylate groups: M(H2O)4 - M(EDTA)-M(H2O)4-... . XPS enables to ascertain that the coordination of the EDTA ligand in the amorphous phase is identical to that in the crystalline phase, i.e., hexacoordination toward the M atom and two bridging groups in the Ni -Ni, Co - Co compounds.

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Solovyeva, Svetlana N., Marina P. Sutunkova, Sergey V. Kuzmin, Larisa I. Privalova, Vladimir B. Gurvich i Boris A. Katsnelson. "Assessment of cytotoxicity of an original industrial aerosol containing a high percentage of amorphous silica in the nanometer range". Hygiene and sanitation 100, nr 9 (20.09.2021): 938–42. http://dx.doi.org/10.47470/0016-9900-2021-100-9-938-942.

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Introduction. At the current stage of hygienic evaluation, the substantiation of at least approximate safe concentrations in the ambient air of populated areas for nanoparticles is an up-to-date challenge. Its persistence dissolves the guidelines for risk management and divests the supervisory bodies of legal support. A comparative toxicological evaluation of the studied substance and its chemical analogue is one of the guidelines for the academic substantiation of the hygienic standards for the permissible content of hazardous substances in the air. It already has previously defined exposure standards. Materials and methods. To investigate the cytotoxicity of the studied particles, a shift of the cellular composition of the bronchoalveolar lavage fluid (BALF) was used. Also, some biochemical measurements of the BALF supernatant were investigated. Outbred female rats were instilled with a suspension of particles in the volume of 1 ml of various concentrations in the form of an intratracheal suspension. Distilled water was used as a solvent. Statistical analysis of the data obtained was performed using the Student’s t-test. Results. The comparative assessment of the cytotoxicity of an original industrial aerosol containing 72% amorphous silica with an average particle size of 90 nm (SiO2 IA) was performed. It also included engineered particles of amorphous silica with an average size of 43 nm (SiO2 NPs), a commercial, an industrial sample of 100% amorphous silica with a particle size of 5 to 60 nm (amorphous SiO2), and a reference sample of standard quartz DQ12 in a volume of 1 ml of water suspension. Under the findings of changes in the cellular composition of the bronchoalveolar lavage fluid 24 hours after the intratracheal instillation of these particles, it was revealed that the biological power (in terms of the NL/AM ratio) of both SiO2 NPs and amorphous SiO2 is statistically much higher than the industrial aerosol under study. It is also higher than the standard quartz dust DQ12. In this regard, the cytotoxicity of SiO2 IA may be explained by the predominant content of amorphous silica nanoparticles in it. Conclusion. Under the obtained results, the appropriateness of using indicative safe exposure levels (ISEL) of 0.02 mg/m3 for amorphous silica needs to be reviewed. The safe reference level of impact guideline does not contain data concerning the particle size and the percentage of amorphous SiO2 in the aerosol. Nevertheless, it is impossible to pollute the ambient air with an aerosol containing only this substance.

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Sanditov, D. S. "Free volume of amorphous substances in the model of delocalized atoms". Doklady Physical Chemistry 464, nr 2 (październik 2015): 255–57. http://dx.doi.org/10.1134/s0012501615100097.

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Chechetkina, E. A. "Synergetic model for the first sharp diffraction peak in amorphous substances". Solid State Communications 87, nr 3 (lipiec 1993): 171–74. http://dx.doi.org/10.1016/0038-1098(93)90469-4.

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Ankele, Jürgen, Joachim Mayer, Peter Lamparter, Peter Lamparter i Siegfried Steeb. "Investigation of the Structure of Amorphous Substances by Means of Electron Diffraction". Zeitschrift für Naturforschung A 49, nr 7-8 (1.08.1994): 771–75. http://dx.doi.org/10.1515/zna-1994-7-807.

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Abstract The structure factor of amorphous germanium was determined using 120 kV electrons, an Ω-filter for the elimination of inelastically scattered electrons and a correction procedure for multiple scattering. The structure factor thus obtained is in good accordance to that obtained with X-rays and neutrons, respectively.

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Sato, Kiminori, i Minoru Hirano. "Age-Related Changes of Elastic Fibers in the Superficial Layer of the Lamina Propria of Vocal Folds". Annals of Otology, Rhinology & Laryngology 106, nr 1 (styczeń 1997): 44–48. http://dx.doi.org/10.1177/000348949710600109.

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An investigation was carried out to determine the morphologic characteristics of elastic fibers in the superficial layer of the lamina propria of aged vocal folds (EFAVFs). Excised human adult vocal folds served as the material for this study. Scanning and transmission electron microscopic observations were made. The results can be summarized as follows. First, the EFAVFs were composed of amorphous substances and microfibrils. The amorphous substances increased in amount and the microfibrils became less numerous. Second, the EFAVFs ran in various directions, were branched, and formed a complicated network. The surface of the fibers was rough, and the fibers appeared to vary in size. Some EFAVFs united to form a sheet with a rough surface. Third, the EFAVFs could not be easily digested by elastase compared with those of younger adults. We conclude that the morphologic and metabolic changes of elastic fibers in the most important vibrating portion (superficial layer of the lamina propria) of the aged vocal folds contribute partially to aging of the voice.

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Chechetkina, E. A. "The first sharp diffraction peak in glasses and in other amorphous substances". Journal of Physics: Condensed Matter 5, nr 43 (25.10.1993): L527—L530. http://dx.doi.org/10.1088/0953-8984/5/43/001.

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G. Choconi, Roberto, Alberto A. Ghini, Victor H. Conzonno i Alicia Fernández Cirelli. "Humic Substances from sediments of Lobos Pond (Argentina). Isolation, Characterization and Limnological Implications". Eclética Química Journal 36, nr 2 (31.10.2017): 128. http://dx.doi.org/10.26850/1678-4618eqj.v36.2.2011.p128-141.

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Humic substances (HS) were isolated from the sediments of Lobos Pond (Argentina) using mild conditions to preserve their native structure. The HS (humic and fulvic acids) were characterized by means of elemental analysis and FTIR spectroscopy. Also a by-product obtained during fulvic acids (FA) fractionation (an amorphous white solid residue) was analyzed. Results revealed possible interactions between FA and inorganic-organic substances that may have implications referring to bioavailability. Other limnological implications, such as autochtonous origin of HS linked with the hydrology, and change of pH during stormy weather that affects HS interactions, are discussed.

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Choconi, Roberto G., Alberto A. Ghini, Victor H. Conzonno i Alicia Fernández Cirelli. "Humic substances from sediments of Lobos Pond (Argentina). Isolation, characterization and limnological implications". Eclética Química 36, nr 2 (2011): 128–41. http://dx.doi.org/10.1590/s0100-46702011000200007.

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Humic substances (HS) were isolated from the sediments of Lobos Pond (Argentina) using mild conditions to preserve their native structure. The HS (humic and fulvic acids) were characterized by means of elemental analysis and FTIR spectroscopy. Also a by-product obtained during fulvic acids (FA) fractionation (an amorphous white solid residue) was analyzed. Results revealed possible interactions between FA and inorganic-organic substances that may have implications referring to bioavailability. Other limnological implications, such as autochtonous origin of HS linked with the hydrology, and change of pH during stormy weather that affects HS interactions, are discussed.

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Sanditov, D. S., M. V. Darmaev i V. V. Mantatov. "Estimation of the parameter of the main equation of the glass transition of amorphous polymers and other amorphous substances". Polymer Science Series A 58, nr 2 (marzec 2016): 302–6. http://dx.doi.org/10.1134/s0965545x16020176.

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Olkhov, Anatoly A., Polina M. Tyubaeva, Yulia N. Zernova, Valery S. Markin, Regina Kosenko, Anna G. Filatova, Kristina G. Gasparyan i Alexey L. Iordanskii. "The Influence of Technological Factors and Polar Molecules on the Structure of Fibrillar Matrices Based on Ultrafine Poly-3-hydroxybutyrate Fibers Obtained via Electrospinning". Technologies 11, nr 5 (6.09.2023): 118. http://dx.doi.org/10.3390/technologies11050118.

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The article examines the regularities of structure formation of ultrafine fibers based on poly-3-hydroxybutyrat under the influence of technological (electrical conductivity, viscosity), molecular (molecular weight), and external factors (low-molecular and nanodispersed substances of different chemical natures). Systems with polar substances are characterized by the presence of intermolecular interactions and the formation of a more perfect crystalline fiber structure. Changes in technological and molecular characteristics affect the fiber formation process, resulting in alterations in the morphology of the nonwoven fabric, fiber geometry, and supramolecular fiber structure. Polymer molecular weight, electrical conductivity, and solution viscosity influence fiber formation and fiber diameter. The fiber structure is heterogeneous, consisting of both crystalline and non-equilibrium amorphous phases. This article shows that with an increase in the molecular weight and concentration of the polymer, the diameter of the fiber increases. At the same time, the increase in the productivity of the electrospinning process does not affect the fiber geometry. The chemical structure of the solvent and the concentration of polar substances play a decisive role in the formation of fibers of even geometry. As the polarity of the solvent increases, the intermolecular interaction with the polar groups of poly-3-hydroxybutyrate increases. As a result of this interaction, the crystallites are improved, and the amorphous phase of the polymer is compacted. The action of polar molecules on the polymer is similar to the action of polar nanoparticles. They increase crystallinity via a nucleation mechanism. This is significant in the development of matrix-fibrillar systems for drug delivery, bioactive substances, antiseptics, tissue engineering constructs, tissue engineering scaffolds, artificial biodegradable implants, sorbents, and other applications.

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Li, Qun, Zhi Xuan Zhang, Si Ming Liu i Ji Xin Su. "Properties of Slag and Ash from the Incinerator in Biomass Power Plants". Advanced Materials Research 512-515 (maj 2012): 579–82. http://dx.doi.org/10.4028/www.scientific.net/amr.512-515.579.

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The properties of slag and ash generated from a biomass power plant were analyzed by various characterization methods and the sulfur was tracked. The results showed that the slag and ash contain major elements like Si, S, K and Ca etc and primary substances like SiO2, CaCO3etc. Sulfur is in the form of amorphous soluble salts and insoluble materials in residual carbon.

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Kim, Jiyoung, Chan Hee Lee, Ran Hee Kim i Eun Jeong Shin. "Characterization of White and Black Deposits on the Surface of Korean Stone Cultural Heritages". Microscopy and Microanalysis 19, S5 (sierpień 2013): 167–71. http://dx.doi.org/10.1017/s1431927613012580.

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AbstractWhite and black deposits have been frequently observed on the surface of Korean stone cultural heritages, and they are considered as damage factors in both conservation and esthetic points of view. In order to set up the appropriate conservation remedy, it is important to know their origins, characteristics, and compositions. In this study, optical and scanning electron microscopes (SEMs) equipped with an energy-dispersive spectrometer (EDS) and X-ray diffractometer were employed to determine the white and black deposits. It was found that both deposits consisted mainly of calcium carbonate (calcite) and calcium sulfate (gypsum). The calcite and gypsum were characterized by bladed, rhombohedral, tabular, and amorphous morphologies under a SEM. The black deposit was not only composed of calcite or gypsum, but also accompanied amorphous and irregular matrix. SEM-EDS analysis revealed an abundance of silicon, aluminum, iron, phosphorus, and carbon on the matrix, which were major elements of soil, atmospheric deposits, and organisms. The white deposit, on the other hand, barely contained those coloring substances. These salts and deposited substances were caused by chemical reaction and physical adhesion between rock-forming minerals, lime mortar, sulfur in polluted air environment, soil dust, and microorganisms.

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Ponyatovsky, E. G. "A thermodynamic approach toT–Pphase diagrams of substances in liquid and amorphous states". Journal of Physics: Condensed Matter 15, nr 36 (29.08.2003): 6123–41. http://dx.doi.org/10.1088/0953-8984/15/36/304.

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Ganguli, Dibyendu. "Polyamorphism in Liquids and Amorphous Substances: An Analogue of Polymorphism in Crystalline Solids". Transactions of the Indian Ceramic Society 68, nr 2 (kwiecień 2009): 65–80. http://dx.doi.org/10.1080/0371750x.2009.11082161.

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Konda, Kishore Kumar, i Siddharatha Dhoppalapudi. "A Review of Various Manufacturing Approaches for Developing Amorphous Solid Dispersions". Journal of Drug Delivery and Therapeutics 12, nr 6 (15.11.2022): 189–200. http://dx.doi.org/10.22270/jddt.v12i6.5787.

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In recent years amorphous solid dispersions (ASD) has gained a tremendous response for improving the solubility of poorly water-soluble drug substances. Despite the stability challenges, various ASD commercial products have been successfully launched into the market over the last two decades. Among various manufacturing approaches, hot melt extrusion (HME) and spray drying techniques have attracted industries attributing to their simple manufacturing processes. In addition, KinetisolÒ, a solvent-free approach, is also being most widely investigated for developing ASDs since the thermal exposure time of the formulations is significantly less compared with the hot melt extrusion process. KinetisolÒ can be employed for developing ASDs of thermolabile drug substances. Another solvent-based technique, electrospinning, is also employed for developing nanofibers-based ASD. However, much research is warranted for the electrospinning process before implementing it in commercial manufacturing. Various critical factors such as drug-polymer solubility, the solubility of the drug in the polymer, drug-polymer interactions, type of manufacturing process, and storage conditions need to be considered for developing a stable and robust ASD formulation. This review mainly focuses on the most advanced manufacturing technologies of ASDs, namely HME, spray drying, KinetisolÒ, and electrospinning, along with a note on the various critical factors that affect the stability of ASD formulations. Keywords: amorphous solid dispersions; hot melt extrusion; spray drying; KinetisolÒ; electrospinning

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Li, Linghan, Tianci Xu, Faping Zhang, Chunhua Du i Song He. "Preparation of Super-Flexible Silica Aerogel and Its Application in Oil–Water Separation". Gels 9, nr 9 (12.09.2023): 739. http://dx.doi.org/10.3390/gels9090739.

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Using silica as the precursor, and methyltrimethoxysilane and dimethyldimethoxysilane as the silicon sources, a super-flexible hydrophobic lipophilic gel solid was prepared via hydrolysis, drying, solvent replacement, and atmospheric-pressure drying. The characterization test showed that the sample had good flexibility, hydrophobicity, an amorphous structure, and a hydrophobic contact angle of 137°. Through the adsorption separation experiment, it was concluded that the adsorption separation rate of aerogel to oil substances is related to the viscosity of the oil substances. The hydrophobic and oleophilic properties of flexible silicon aerogel materials can be applied to many aspects, such as crude oil leakage and kitchen waste oil recovery, with broad future development prospects and great research significance.

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Sainte-Marie, Guy, i Bernard Sainte-Marie. "Reproductive products in the adult snow crab (Chionoecetes opilio). I. Observations on spermiogenesis and spermatophore formation in the vas deferens". Canadian Journal of Zoology 77, nr 3 (1.09.1999): 440–50. http://dx.doi.org/10.1139/z98-229.

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Some of the events unfolding in the vas deferens of the adult snow crab (Chionoecetes opilio) were examined by means of light microscopy. Sperm cells entered the vas deferens as precursors of immature spermatids and developed into immature or mature spermatids within it. However, spermatozoa were not observed in the male reproductive tract. Two types of amorphous matter were added successively to sperm cells in the vas deferens. The first type was periodic acid - Schiff (PAS)-positive and apparently induced spermiogenesis when present in a sufficiently large amount. However, a smaller amount of this amorphous matter was sufficient to form the basal pellicle of spermatophores. The second type was PAS-negative and thickened the wall of spermatophores. Immature and mature spermatids were usually enclosed within distinct spermatophores. Enclosed mature spermatids were connected together by bridges formed by Feulgen-positive spikes coated and extended by PAS-positive amorphous matter. Once broken, the bridges appeared as arms that radiated from a spermatid. Peripheral mature spermatids were furthermore linked to the spermatophore wall by threads of PAS-positive amorphous matter. The bridges and threads may form a pathway for the diffusion of extraneous substances through the spermatophore wall to the innermost cells.

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Zhorov, Georgiy Aleksandrovich, Lyubov Lvovna Zakharova, Vasiliy Ivanovich Dorozhkin i Elizaveta Arkadievna Denisova. "Control of Ecotoxicants Content in Feed Additives and Veterinary Pharmacological Products". BIO Web of Conferences 37 (2021): 00041. http://dx.doi.org/10.1051/bioconf/20213700041.

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The article is devoted to the control of ecotoxicants content in mineral and organic substances of natural and artificial origin used in the production of feed additives and pharmacological veterinary agents. In the context of the growing technogenic load on the environment, the probability of detecting increased background levels of natural and technogenic ecotoxicants in mineral and organic raw materials for the production of feed additives and veterinary products increases significantly. In this regard, more attention should be paid to the study of substances of artificial origin with a minimum content of toxic and ballast components, as well as substances that have undergone technological processing to reduce their natural level of ecotoxicants. According to modern data, amorphous silicon dioxide is an effective, safe, economically available sorbing agent and it should be considered as a promising sorption-detoxifying agent for application under the influence of xenobiotics that differ in the toxicological action mechanism on the animal organism.

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Zolotov, S. A., I. A. Dain, N. B. Demina, A. S. Zolotova i E. S. Ponomarev. "The Effect of Solvents and Drying Temperature on the Physicochemical Properties of Darunavir and Darunavir Ethanolate Substances". Drug development & registration 10, nr 1 (25.02.2021): 67–73. http://dx.doi.org/10.33380/2305-2066-2021-10-1-67-73.

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Introduction. Usage of aggressive conditions (solvents, high temperature, etc.) in a dosage form manufacturing can lead to a change in the properties of a pharmaceutical substance. Darunavir (D) amorphous and darunavir ethanolate (DE) crystalline both have poor solubility, ability to pseudopolymorphism and are sensitive to high temperatures.Aim. Study the effect of solvents and drying temperature on the physicochemical properties of D and DE substancesMaterials and methods. D (Mylan Laboratories Limited), DE (Mylan Laboratories Limited), D (reference standard) 99,9 % (MSN Pharmachem Private Limited). D and DE weighed quantity was suspended in one of the solvents via magnetic stirrer and was dried via universal oven. Powder X-ray diffraction of dried samples was carried out via automatic powder diffractometer. Using DSC thermal properties of the samples were studied. Crystalline samples were examined using IR spectroscopy. Identification of D and DE was performed by HPLC method.Results and discussion. This article summarizes study results of the investigation of various solvents and drying temperature influence on the physicochemical properties of D and DE are presented. The impact of solvent type and drying temperatures in physicochemical properties of the APIs was studied by X-ray powder diffraction, differential scanning calorimetry, IR spectroscopy and HPLC methods. It was shown, that solvent type and drying temperatures can result in the presence of crystalline D solvates or amorphous D.Conclusion. To obtain the final drug containing as an API amorphous D, which perform better dissolution, one of the enlisted solvents can be used: dichloromethane, chloroform and heptane. In such case the intermediate product drying should be performed at not exceeding the solvent boiling point temperatures. In case of ethanol, methanol, acetone and tetrahydrofuran drying phase can be performed at temperatures, that are higher than melting points of obtained pseudopolymorphs. For the utilization of DE as an API only ethanol usage is efficient and drying temperature should not exceed 73.4 °C.

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Hu, Shu Gang, Xian Jun Lu i Hai Li Niu. "Research on Properties and Reaction Mechanism of Blast Furnace Slag Backfilling Cementing Material". Applied Mechanics and Materials 692 (listopad 2014): 454–59. http://dx.doi.org/10.4028/www.scientific.net/amm.692.454.

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According to XRD, DTA and SEM detections, the hydration products of blast furnace slag based cementing material SL, SLG. were studied in different age periods. The XRD analysis of cementing material SL hydration products showed the composition of hydration products were mainly amorphous substances, few crystalline substances. Characteristic peak of ettringite, such as AFt, hadn’t been found in the spectral line of DTA, and it hadn’t been found in the figures of SEM, either, which was accordant with the conclusion that the cementing performance of SL mainly coming from gel of hydrated calcium silicate (CSH) and hydrated calcium aluminate. But the cementing performance of SLG mainly coming from Aft, CSH and AFm from hydration products analysis of different age periods.

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Volkov, Dmitry S., Olga B. Rogova i Mikhail A. Proskurnin. "Temperature Dependences of IR Spectra of Humic Substances of Brown Coal". Agronomy 11, nr 9 (11.09.2021): 1822. http://dx.doi.org/10.3390/agronomy11091822.

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The capabilities of temperature-monitored IR spectroscopy for studying the organic matter and mineral composition of humic substances (HS) were tested. Temperature dependences of the mid-IR spectra of humic substances heated in the air in the range 25–215 °C (298–488 K, with a step of 2.5 °C)—for three commercially available samples isolated from brown coal (leonardite)—were performed. The characteristic bands were identified, and their changes in band maxima positions and intensities were compared. From the viewpoint of interpretation of HS components, the spectra were divided into regions of quartz lattice region (800–260 cm−1), quartz overtone region (1270–800 cm−1), humic substance organic matter region (1780–1270 cm−1), quartz combination region (2800–1780 cm−1), CH-speciation region (3100–2800 cm−1), and hydrogen-speciation region (4000–3100 cm−1) thus selected to contain the dominating type of bands. For the first time, a reversible change in the frequencies of the band maxima in IR spectra upon heating was observed, which can be interpreted as forming structures with a particular order in the studied humic substances in the dry state. For a single sample, both the band-shift scale and the functional dependence of the various bands on temperature differ significantly. The approach differentiates crystalline quartz bands, amorphous silica, and HSOM/surface groups experiencing a different temperature behavior of the band maxima and their intensities. Band-maximum temperature dependence can be considered more stable to changes in experimental conditions than band maxima at a single temperature, thus providing a more detailed HS structure analysis without HS decomposition or destruction.

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Bashouti, M. Y., A. Manshina, A. Povolotckaia, A. Povolotskiy, A. Kireev, Y. Petrov, M. Mačković i in. "Direct laser writing of μ-chips based on hybrid C–Au–Ag nanoparticles for express analysis of hazardous and biological substances". Lab on a Chip 15, nr 7 (2015): 1742–47. http://dx.doi.org/10.1039/c4lc01376j.

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Shpotyuk, Oleh, Zdenka Lukáčová Bujňáková, Peter Baláž, Andriy Kovalskiy, Małgorzata Sznajder, Jozef Cebulski, Yaroslav Shpotyuk, Pavlo Demchenko i Ihor Syvorotka. "Equimolar As4S4/Fe3O4 Nanocomposites Fabricated by Dry and Wet Mechanochemistry: Some Insights on the Magnetic–Fluorescent Functionalization of an Old Drug". Materials 17, nr 8 (10.04.2024): 1726. http://dx.doi.org/10.3390/ma17081726.

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Multifunctional nanocomposites from an equimolar As4S4/Fe3O4 cut section have been successfully fabricated from coarse-grained bulky counterparts, employing two-step mechanochemical processing in a high-energy mill operational in dry- and wet-milling modes (in an aqueous solution of Poloxamer 407 acting as a surfactant). As was inferred from the X-ray diffraction analysis, these surfactant-free and surfactant-capped nanocomposites are β-As4S4-bearing nanocrystalline–amorphous substances supplemented by an iso-compositional amorphous phase (a-AsS), both principal constituents (monoclinic β-As4S4 and cubic Fe3O4) being core–shell structured and enriched after wet milling by contamination products (such as nanocrystalline–amorphous zirconia), suppressing their nanocrystalline behavior. The fluorescence and magnetic properties of these nanocomposites are intricate, being tuned by the sizes of the nanoparticles and their interfaces, dependent on storage after nanocomposite fabrication. A specific core–shell arrangement consisted of inner and outer shell interfaces around quantum-confined nm-sized β-As4S4 crystallites hosting a-AsS, and the capping agent is responsible for the blue-cyan fluorescence in as-fabricated Poloxamer capped nanocomposites peaking at ~417 nm and ~442 nm, while fluorescence quenching in one-year-aged nanocomposites is explained in terms of their destroyed core–shell architectures. The magnetic co-functionalization of these nanocomposites is defined by size-extended heterogeneous shells around homogeneous nanocrystalline Fe3O4 cores, composed by an admixture of amorphous phase (a-AsS), nanocrystalline–amorphous zirconia as products of contamination in the wet-milling mode, and surfactant.

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