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Fundamentals of Radiation Physics and Dosimetry
Published in Arash Darafsheh, Radiation Therapy Dosimetry: A Practical Handbook, 2021
Blake R. Smith, Larry A. DeWerd
describes the relationship for the measured exposure, , in units of Roentgen (R) to collision kerma in units of Gy. The constant converts from the unit of Roentgen to the charges produced per unit mass of air, C kg−1 R−1, and the quantity , approximately 33.97 J C−1, is the energy required to create a charge pair in dry air. The standard used for 60Co energies at the US standards lab was a known-volume graphite chamber with a well-known collection volume. Based on the measured charge from ionized gas in the cavity, the exposure can be calculated from
Mass Spectrometric Analysis
Published in Adorjan Aszalos, Modern Analysis of Antibiotics, 2020
Like SIMS, this method uses a modified ion beam. Argon was first used and is still frequently used because of lower costs, but xenon was found to be more efficient [97]. The ions are converted to neutral species by charge exchange with a high pressure of un-ionized gas in the source itself. Residual argon or xenon ions are removed from the atom beam (2–10 KeV) by an electrostatic deflector. The most striking difference between FAB and other particle-induced desorption methods is the way the sample is prepared. It is dissolved in a liquid or oil that has a low vapor pressure [98]; glycerol is most used at present. A thin film of the solution is applied to a heatable surface that is exposed to the atom beam at an incidence angle of approximately 15°. The advantage to using a solution is that the molecular surface is continually refreshed, thereby avoiding quenching of the ion yields that would be caused by surface damage to solid films. Results can frequently be optimized by adding an acid or base to the sample solution.
Analysis of Clinical Specimens Using Inductively Coupled Plasma Mass Spectrometry
Published in Steven H. Y. Wong, Iraving Sunshine, Handbook of Analytical Therapeutic Drug Monitoring and Toxicology, 2017
K. Owen Ash, Gabor Komaromy-Hiller
The term plasma refers to a hot, partially ionized gas. In the analytical field, argon plasmas are prominent, but mixed (Ar-N2) and even pure helium-based plasmas are also described.18 The energy required to maintain the plasma is provided by an electromagnetic field in the form of radiofrequency (ICP) or microwave energy in microwave-induced plasmas, or by a direct current (dc) discharge. The commercially available emission and mass spectrometers are coupled to ICP.
Efficacy of cavity liners with/without atmospheric cold helium plasma jet for dentin remineralization
Published in Biomaterial Investigations in Dentistry, 2020
Hamid Kermanshah, Reza Saeedi, Elham Ahmadi, Ladan Ranjbar Omrani
Plasma is the 4th state of matters that forms at very high temperatures. This ionized gas includes photons, electrons, positive and negative ions, atoms, free radicals, and excited and non-excited molecules that constantly interact with each other [11]. Plasma has different types including hot, warm and cold plasma. The cold plasma is a type of plasma created by electrical discharge [12]. Of different methods of production of cold plasma, plasma jet has gained attention since it is portable, can be charged on spot and has low energy consumption. The ACPJ has low temperature (room temperature) and therefore, has several medical applications [13]. Researchers have shown that plasma surface modification is a clean and effective method [10]. Its effect is related to plasma reactive species. According to the plasma type, the plasma gas reacts with the surface of substrates and creates new surface characteristics [10]. Increased wettability, as well as permeability, is among the modifications caused by argon and helium plasma in dental substrates [10].
Non-thermal plasma induces immunogenic cell death in vivo in murine CT26 colorectal tumors
Published in OncoImmunology, 2018
Abraham G. Lin, Bo Xiang, Dante J. Merlino, Trevor R. Baybutt, Joya Sahu, Alexander Fridman, Adam E. Snook, Vandana Miller
Plasma, the fourth state of matter, is ionized gas composed of charged particles, active neutral gas species, electric fields, and low amounts of ultraviolet (UV) light.7–11 Development of plasma systems that can be sustained in atmospheric pressure and at room temperature has opened doors for biomedical applications, including, but not limited to, cancer therapy.12–14 Mounting evidence demonstrates that these ‘non-thermal plasmas’ (NTP) can be optimized to destroy tumors with minimal damage to neighboring healthy tissue.14–17 Decreased tumor burden and prolonged animal survival following direct plasma treatment have been reported, suggesting that plasma should be further explored as a viable candidate for cancer treatment.18
Prevention of Peritoneal Adhesions by Non-Thermal Dielectric Barrier Discharge Plasma Treatment on Mouse Model: A Proof of Concept Study
Published in Journal of Investigative Surgery, 2020
Uğur Gökçelli, Utku Kürşat Ercan, Enver İlhan, Asuman Argon, Elif Çukur, Orhan Üreyen
Plasma is ionized gas and defined as the fourth state of matter next to solid, liquid, and gas and could be generated by application of an external electric field to a gas [15]. Plasma consists of positively and negatively charged atoms and/or molecules, free electrons, electrically excited particles, neutrals, reactive oxygen species (ROS), reactive nitrogen species (RNS), free radicals, and ultraviolet (UV) photons [16,17]. According to gas temperature, plasmas are classified as thermal (hot or equilibrium) and non-thermal (cold or non-equilibrium) plasmas based on the thermal equilibrium in between electrons and heavy particles. In thermal plasmas, the gas temperature is in equilibrium with electrons and may reach up to thousands of kelvins which limits their application to tissues for therapeutic purposes. Conversely, in non-thermal plasmas, electrons and gas are not in thermal equilibrium and gas remains in room temperature. Thus, non-thermal plasmas could be used on tissues for therapeutic applications without thermal damage [15,18]. Thermal plasmas have been used in medicine, particularly in surgery, for coagulation, ablation, and cauterization [19]. Besides, due to the applicability of non-thermal plasmas on heat-sensitive materials and tissues, biomedical applications of non-thermal plasma have been drawing the attention of scientific community for couple decades and formed itself a new area called as “Plasma Medicine” [20]. To date, various biomedical applications of non-thermal plasmas including, antimicrobial, wound healing, anticancer, blood clotting effects along with dental and biomaterial modification applications, were reported [15,21–23]. Various thermal and non-thermal plasma devices are present in the market and routinely used in clinical applications with an increasing number of novel biomedical applications [19].