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Fluid Bed Processing
Published in Dilip M. Parikh, Handbook of Pharmaceutical Granulation Technology, 2021
Kulling and Simon [18] reported the closed-loop system shown in Figure 10.34. The inert gas (generally nitrogen) used for fluidization circulates continuously. An adjustable volume of gas is diverted through the bypassed duct where solvent vapors are condensed, and solvent collected. The circulating gas passes through the heat exchanger to maintain the temperature necessary for the evaporation of the solvent from the product bed. During the agglomeration and subsequent drying process, the solvent load in the gas stream does vary. The bypass valve controls the flow of the gas to the heat exchanger and the condenser. By controlling the gas stream in this manner, the drying action is continued until the desired level of drying is reached. Even though the cost of the fluid bed processor with the solvent recovery is generally double the cost of a regular single pass fluid bed processor, such a system offers effective measures for both explosion hazard reduction and air pollution control.
Gas Exchange in the Lungs
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
This form of the alveolar air equation produces a small error, as it does not account for an additional effect of the respiratory quotient: the expired gas volume differs from the inspired volume. The inspired and expired gas volumes may also differ if inert gases (nitrogen) are not in equilibrium – as may be the case during anaesthesia. A more complex form of the alveolar air equation accounts for these factors and only requires knowledge of inspired , and collection of mixed expired gas for measurement of mixed expired and (the respiratory quotient is not required):
Physics of Radiation Biology
Published in Kedar N. Prasad, Handbook of RADIOBIOLOGY, 2020
Electrons are negatively charged particles and orbit the atomic nucleus in a precisely defined path, each path being characterized by its own unique energy level. Electrons are positioned in shells or energy levels that surround the nucleus. The first or K shell contains no more than 2 electrons, the second or L shell no more than 8 electrons, and the third or M shell no more than 18 electrons (Figure 3.2). The outermost electron shell of an atom, no matter which shell it is, never contains more than 8 electrons. Electrons in the outermost shell are termed valence electrons and determine to a large degree the chemical properties of an atom. An atom with an outer shell filled with electrons seldom reacts chemically. These atoms constitute elements known as the inert gases (helium, neon, argon, krypton, xenon, and radon).
Advances in encapsulating gonadotropin-releasing hormone agonists for controlled release: a review
Published in Journal of Microencapsulation, 2022
Nardana Bazybek, Yi Wei, Guanghui Ma
Spray drying is applied to produce microencapsulated or matrix-based drug delivery systems to obtain sustained drug formulation. This technology is a continuous process that transforms feedstock solutions into dried micro-sized particles by subjecting feed to a high-temperature and gaseous medium (Al-Khattawi et al.2018). According to Figure 5, spray drying consists of three main stages: atomisation, drying, and separation. Atomisation refers to converting a liquid stream into small fine particles by the appropriate device. In this stage, the prepared feedstock is delivered through a peristaltic pump to the atomiser chamber by a nozzle. Then, droplets are produced in the atomiser chamber by exposure to the interaction with a hot drying gas (higher than feed temperature) (Shi et al.2020). Atomised dispersion droplets are subjected to a hot gas stream in the second stage, which mainly refers to atmospheric air. In some cases, it is required to use inert gas to obtain the stability of particles. Process conditions such as inlet temperature, drying air temperature, and device geometry simultaneously influence the drying performance and efficiency. In the last stage, dried product particles are collected using a separation device as a cyclone (Cal and Sollohub 2010).
Effect of first order chemical reactions through tissue-blood interface on the partial pressure distribution of inhaled gas
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Numerical code validation and predictive accuracy of the model are checked by comparing output data produced by the present model by removing flow through a tissue-blood capillary interface under reactive boundary conditions with the previous model of Saini et al. (2010) for partial pressure of the gas at breath rate (f) = 1–10 and represented in Figure 3(a) (Table 1). Saini et al. (2010) studied unsteady partial pressure of inert gas by using generalized diffusion equations without any consideration of short time dispersion, flow through the tissue-blood capillary interface, and reactive boundary conditions. Figure 3(a) shows variation in partial pressure with axial distance. We found that our numerical result is validated with their result of up to 99.9%. So, we can say, our results are in excellent agreement with those of Saini et al. (2010).
Pneumatic retinopexy: a review of an essential technique in vitreoretinal surgical care
Published in Expert Review of Ophthalmology, 2022
Ian Shao, Arjan S. Dhoot, Marko M. Popovic, Paola L. Oquendo, Hesham Hamli, Peter J. Kertes, Rajeev H Muni
In clinical practice, the inert gases sulfur hexafluoride (SF6) and perfluoropropane (C3F8) are often used, with the former being more favorable. SF6 has a doubling of size within the first 24–48 hours, and lasts an average duration of 12 days within the eye after injection. In comparison, C3F8 quadruples in volume after injection, however, its longer average duration of 38 days is longer than necessary and may result in undesirable outcomes [10–13,15]. Furthermore, it takes 3–4 days for the C3F8 gas bubble to reach its maximal volume which is less ideal than the 36 hours it takes for SF6. If a larger bubble is required, we prefer sequential SF6 gas injections separated by a few days.