Physics of Radiation Biology
Kedar N. Prasad in 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).
Suicidal Poisoning
David J. George in Poisons, 2017
For many years, carbon monoxide from various sources was the most commonly employed gas used as a suicidal agent. Other gases are now being encountered in suicidal investigations. These include inert gases, which act by blocking access to oxygen, and reactive gases that prevent utilization of inspired oxygen. Some of the more common gases that have been utilized for suicide are listed in Table 26.2. In the past few years, there has been an increase in suicides using hydrogen sulfide generated from combinations of common household products. By combining acidic products with sulfur-containing products in confined spaces, lethal levels of hydrogen sulfide can be produced quickly (Table 26.3). Death from hydrogen sulfide can occur after only a few breaths.
Presentation Format
Kitsakorn Locharoenrat in Research Methodologies for Beginners, 2017
Currently there are two devices (solar panel and solar concentrator) for the solar collection to convert heat to electricity. Although the life-times of these devices are not so different, solar concentrator quite works well in terms of the high thermal efficiency as compared with solar panel [1]. In solar concentrator, the solar receiver is generally used at the focal point of the parabolic dish. Alternatively, we are able to use Stirling engine in place of the receiver. This system can also be applied to the solar tracking system [2]. The principle of the Stirling engine relies on the temperature difference between the cylindrical displacer (hot side) and power cylinder (cold side). We can easily apply the cylindrical displacer in place of the receiver. The important parameters of the engine consist of displacer length, compression ratio, total pressure, thermal efficiency, output mechanical power, and Beale number. Herein we introduce a new design and construction of the gamma-type Stirling engine relying on the working temperature difference caused by the heat source of the solar concentrator. Our entire engine is made of brass that has a good thermal conductivity as compared with other works [3–4]. We also use air served as a working fluid in place of inert gas [3–7] in the entire engine system that is environmentally friendly. We will show the performance of the engine in terms of the thermal efficiency and the output mechanical power. We expect that our engine will be useful for the heat collection in future.
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).
Mechanics of tablet formation: a comparative evaluation of percolation theory with classical concepts
Published in Pharmaceutical Development and Technology, 2019
Saurabh M. Mishra, Bhagwan D. Rohera
True density of the powder materials was determined using a gas pycnometer (AccuPyc® II 1340, Micromeritics Instruments Corp., Norcross, GA). The pycnometer allows nondestructive measurement of volume and density of powder and solid materials, and uses a gas displacement technique to determine the volume of the sample under test. An inert gas (helium) was used as the displacement medium. Pycnometer was calibrated with an iron sphere of known mass prior to each measurement. For the determination, a known weight of powder sample was transferred into an aluminum sample container of 3.5 cm3 volume, and helium gas was passed through the sample from the reservoir. The determinations were carried out at room temperature. The instrument automatically purges moisture and volatile materials from the powder sample and repeats the analysis until successive measurements yield consistent results. The determination of sample density was repeated for up to 10 cycles. The average reading of 10 cycles was recorded as the true density of the material.
Overview of prevention and management of acute bronchiolitis due to respiratory syncytial virus
Published in Expert Review of Anti-infective Therapy, 2018
Helium is an inert gas, and its density is almost 15% that of air. Carbon dioxide (CO2) is more diffusible through helium than air. Helium inhalation results in maintenance of more laminar gas flow and decreases turbulence through narrowed airways, which subsequently lowers resistance to gas flow. Therefore, breathing heliox decreases airway resistance and reduces work of breathing [69,70]. Heliox has been shown to improve oxygenation in respiratory illness with moderate to severe airway obstruction, including in AVB [71]. A meta-analysis of four clinical trials (with 84 participants) using heliox, demonstrated improved respiratory distress scores in the first hour of its use in children with moderate to severe AVB. However, heliox inhalation did not affect need for intubation and mechanical ventilation and LOS in the pediatric intensive care unit [31,72]. The routine use of heliox is, therefore, not currently recommended.
Related Knowledge Centers
- Argon
- Butylated Hydroxytoluene
- Chemical Compound
- Chemical Reaction
- Helium
- Hydrolysis
- Sodium Benzoate
- Redox
- Air Separation
- Antimicrobial