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Viruses as Nanomaterials
Published in Devarajan Thangadurai, Saher Islam, Charles Oluwaseun Adetunji, Viral and Antiviral Nanomaterials, 2022
Dushyant R. Dudhagara, Megha S. Gadhvi, Anjana K. Vala
XRD is a primary technique for the identification of the crystalline nature at the atomic scale (Sapsford et al. 2011; Waseda et al. 2011). X-ray powder diffraction is a nondestructive technique with great potential for the characterization of both organic and inorganic crystalline materials. This method has been used to measure phase identification, conduct quantitative analysis, and determine structural imperfections in samples from various disciplines, such as geological, polymer, environmental, pharmaceutical, and forensic sciences. Recently, the applications have extended to the characterization of various nanomaterials and their properties (Das et al. 2014). The working principle of X-ray diffraction follows Bragg's law. Typically, XRD techniques are worked based on the wide-angle elastic scattering of X-rays (Lin et al. 2014). Although XRD has several advantages, it has limited disadvantages, including difficulty in growing the crystals and the ability to get results pertaining only to a single conformation/binding state (Sapsford et al. 2011). Another drawback of XRD is the low intensity of diffracted X-rays compared to electron diffractions (Chapman et al. 2011).
Organization and Management of a Radiation Safety Office
Published in Kenneth L. Miller, Handbook of Management of Radiation Protection Programs, 2020
Steven H. King, Rodger W. Granlund
Analytical X-ray machines include X-ray diffraction and fluorescence units, electron microscopes, and the various scanning electron microscopes, and X-ray emission devices. Only the X-ray diffraction and fluorescence units present a significant safety hazard, although some of the early electron microscopes produced high radiation fields under some conditions.
Solid State Testing of Inhaled Formulations
Published in Anthony J. Hickey, Sandro R.P. da Rocha, Pharmaceutical Inhalation Aerosol Technology, 2019
Philip Chi Lip Kwok, Hak-Kim Chan
X-ray powder diffraction involves the detection of the X-ray diffraction pattern of a randomly oriented powder. The diffraction patterns of highly crystalline solids show sharp peaks, while those of amorphous solids show broad halo patterns (Figure 23.2). The angular positions of the peaks are characteristic to the compound, and polymorphic form thus can serve as a “fingerprint” for identification. Peak intensity is affected by the preferred orientation and crystallinity of the particles. Preferred orientation is a particularly a problem for acicular and plate-like particles. One way of increasing the orientation randomness in the powder bed is particle size reduction (British Pharmacopoeia 2017, European Pharmacopoeia 2017, United States Pharmacopeia 40-National Formulary 35 2017). However, too much milling may reduce the crystallinity, change the polymorphic form, or cause other solid state reactions so it should be avoided. Particles in the inhalable size range (1 µm–5 µm) should have less issues with preferred orientation because they can pack better than large particles.
Monte Carlo dosimetry using Fluka code and experimental dosimetry with Gafchromic EBT2 and XR-RV3 of self-built experimental setup for radiobiological studies with low-energy X-rays
Published in International Journal of Radiation Biology, 2020
Joanna Czub, Janusz Braziewicz, Adam Wasilewski, Anna Wysocka-Rabin, Paweł Wołowiec, Andrzej Wójcik
This relatively unconventional experimental setup for radiobiological research required a number of experimental solutions and simulation calculations. The experimental system was created at Jan Kochanowski University, Kielce, Poland and used an X-ray beam with a maximum energy of 60 keV, filtered through an Al filter of thickness 1 mm. The X-ray tube was adapted from the field of X-ray diffraction science to radiobiological studies. The consequence of this step is the heterogeneous distribution of X-rays in the vertical beam profile and the need for cell irradiation in a vertical position. Hence, to ensure the uniformity of the radiation distribution on the irradiated surface, a rotation system was introduced to provide a uniform distribution of radiation with deviation equal to ±3.5%. A specially constructed Petri dish was introduced to enable vertical irradiation of living cells. The component of this Petri dish on which cells were located during irradiation was the coverglass, which was made from borosilicate glass. MC simulations show that this component caused an increase in the dose absorbed by the cells, due to the emission of characteristic radiation in the backscattered radiation spectrum. These simulations also show that the absorbed dose rate was equal to 0.9 Gy/min. At this point it should be emphasized that the construction of the Petri dish which is used in radiobiological research is a very important component in the process of determining the dose absorbed by living cells.
Physical stability of dry powder inhaler formulations
Published in Expert Opinion on Drug Delivery, 2020
Nivedita Shetty, David Cipolla, Heejun Park, Qi Tony Zhou
The most commonly used solid-state characterization techniques for determining crystallinity in DPI formulations include PXRD, FTIR, FT-Raman spectroscopy, DSC, TGA and DVS [165]. Powder X-ray crystallography or PXRD measures the crystal structure and degree of crystallinity. It is a common tool to detect polymorphism and crystallinity in amorphous systems. X-ray diffraction is a classic technique based on the principle that when X-rays diffract from atoms that appear repeatedly in the same position within the unit cell (i.e. a crystalline structure), a sharp peak is observed [166]. In general, the limit of detection (LOD) for crystalline structures when using PXRD is about 2% depending on the system. In contrast, amorphous structures have a short-range order which is observed as a broad baseline hump referred to as halo. Even if a sample is 10–20% amorphous, the halo may not be evident and cannot be separated completely with diffraction peaks. PXRD is useful for the detection of a small amount of crystalline, but it is difficult to obtain reliable results for samples with low amorphous content to access accurate amorphous content [167]. PXRD has been employed in investigating the crystallinity of α- lactose monohydrate and comparing it to spray-dried lactose which lacks crystalline long-range order [168]. PXRD is commonly used to determine and quantify the presence of crystallinity in spray-dried amorphous powder DPI formulations stored at higher humidity [72,169–171].
Spectroscopic and computational insights into theophylline/β-cyclodextrin complexation: inclusion accomplished by diverse methods
Published in Journal of Microencapsulation, 2018
Subhraseema Das, Jitendra Maharana, Subhrajit Mohanty, Usharani Subuddhi
X-ray diffraction has been employed as one of the useful tools to judge drug-CD complexation phenomenon. The diffraction profile of the IC is generally different from those of the individual components. Figure 2(B) presents the wide-angle X-ray diffraction profiles of β-CD, THP, PM, KN, CP, FD, and MW. The β-CD and THP diffractograms display a series of sharp intense peaks. The powdered XRD profile of β-CD includes peaks at 9.1°, 12.5°, 23.0°, and 25.8° which suggest β-CD adopts a highly crystalline nature. A sharp peak at 12.6° was observed in the XRD profile of THP which also revealed its crystalline nature. The diffraction profile of the PM revealed the features of both β-CD and THP suggesting that no new crystal has been formed. The diffraction profile of KN exhibits some new peaks along with the peaks due to drug and β-CD which point towards incomplete complexation. The diffractogram of CP, FD, and MW illustrates completely different features relative to the parent components. Thus, the formation of new entities due to formation of ICs by the co-precipitation, freeze-drying, and microwave irradiation methods is clearly evident.