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Reference Dose Determination under Reference Conditions
Published in W. P. M. Mayles, A. E. Nahum, J.-C. Rosenwald, Handbook of Radiotherapy Physics, 2021
Graphite has radiation-interaction characteristics similar to those of water. As it is a readily-machined solid, a well-defined absorbing core can be constructed, surrounded by vacuum gaps and reflecting surfaces that minimise heat exchange between the core and its surroundings. The heat defect is estimated to be less than 0.1% (Chapter 11 in Andreo et al. 2017), but there are uncertainties associated with the correction for conduction as well as the conversion from absorbed dose to graphite to absorbed dose to water. More details on the required conversion factors can be found in Nutbrown et al. (2002). The basic design was established by Domen and Lamperti (1974), represented generically in Figure 19.4.
Calorimetry
Published in Arash Darafsheh, Radiation Therapy Dosimetry: A Practical Handbook, 2021
Larry A. DeWerd, Blake R. Smith
The two types of calorimeters used in the past by primary laboratories have been a graphite calorimeter or a water calorimeter. Of course, the preferred quantity is absorbed dose to water, but the procedure for water calorimetry is more involved. Water calorimetry has a heat defect that must be taken into account. A heat defect arises when some of the energy deposited in the material is not liberated as heat because of chemical reactions or other effects, exothermic or endothermic [2]. Water can have a significant heat defect, which depends on the impurities and/or dissolved gases. Any perturbations from the surrounding materials must also be taken into account. If graphite is used, there needs to be correction of the absorbed energy from graphite to water. Graphite does not have a significant heat defect [2].
Inorganic Particulates in Human Lung: Relationship to the Inflammatory Response
Published in William S. Lynn, Inflammatory Cells and Lung Disease, 2019
Victor L. Roggli, J. P. Mastin, John D. Shelburne, Michael Roe, Arnold R. Brody
Anthracotic pigment may be identified in all adult human lung tissues, but it is extraordinarily difficult to prove that this material is inorganic carbon. Gravimetric methods have been described for measuring inorganic carbon as CO2,121 but these methods presume that organic carbon has been removed or extracted. Methods for determination of lung “soot”118 are of couse measuring inorganic carbon as well as silica, silicates, endogenous particulates, and other inorganic particulates. Churg et al.50 have noted that some non-asbestos ferruginous bodies (or pseudoasbestos bodies) contain black fibrous cores (Figure 6) which contained no elements detectable by EDXA (which is insensitive for elements with Z < 11) and produced no diffraction pattern. These investigators concluded that these black cores were probably amorphous carbon. Lynn et al.122 studied the black material obtained from a heavy cigarette smoker by bronchoalveolar lavage and found similar results with EDXA and microdiffraction studies of the extracted particulates. Scanning Auger microprobe studies were performed on this material, since Auger spectroscopy is sensitive to low atomic number elements. The particles were composed primarily of carbon (91.2% atomic), with trace amounts of sulfur, nitrogen, oxygen, iron, sodium, aluminum, and silicon. Graphite has also been identified in the lungs of individuals exposed to this material industrially.89, 123
Assessment of toxic metal ions in tea samples using new microextraction technique based on the solidified deep eutectic solvent followed by GFAAS
Published in Toxin Reviews, 2021
Toraj Ahmadi-Jouibari, Negar Noori, Nazir Fattahi
The experiments were performed using a Model nov AA 400 atomic absorption spectrometer (Analytik Jena AG, Jena, Germany), equipped with deuterium background correction, a transversely heated graphite tube atomizer and a MPE 60 auto-sampler. The optimized temperature programs for GFAAS are recommended in Table 1. Pyrolytic graphite coated graphite tubes with integrated PIN platform (Analytik Jena Part No. 407-A81.026) were used. Argon (99.999%) was purchased from Air Products (UK) as a purge and protective gas at a flow rate of 500 mL min−1 during all stages, except during atomization, when the flow was stopped. A Hettich Zentrifugen (EBA20, Tuttlingen, Germany) was used for centrifugation. The pH values were measured with a Metrohm pH meter (Model: 692, Herisau, Switzerland) supplied with a glass-combined electrode.
Development of graphene based nanocomposites towards medical and biological applications
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2020
Seyyed Mojtaba Mousavi, Foo Wah Low, Seyyed Alireza Hashemi, Chin Wei Lai, Younes Ghasemi, Sadaf Soroshnia, Amir Savardashtaki, Aziz Babapoor, Nelson Pynadathu Rumjit, Su Mei Goh, Nowshad Amin, Sieh Kiong Tiong
In addition, several types of graphene materials included graphite, graphite oxide, GO, and rGO were prepared and tested against E. coli bacteria and toxicity effects. The intensity of toxicity was measured by membrane stress and oxidative signals. They found that GO had less toxic than others samples (rGO > graphite > graphite oxide) [46]. While exploring the fabrication and design for antimicrobial application, graphene-poly-N vinyl carbazole (PVK) nanocomposites were biased towards a broad array of bacteria. This showed significant microbial inhibition and toxicity results (>80%) [47]. After that, the PVK-GO nanocomposite was explored for toxicity test and investigated under planktonic microbial cells, metallidurans B. subtilis E. coli, C. and R. opacus, mammalian fibroblast cells (NIH 3T3), and biofilms, respectively. The results revealed that PVK-GO possessed stronger antimicrobial effect rather than raw GO. It was also indicated that the PVK-GO exhibited neutral preferences on fibroblast cells, leading to further investigations on biomedical applications [48].
Variability, toxicity, and antioxidant activity of Eupatorium cannabinum (hemp agrimony) essential oils
Published in Pharmaceutical Biology, 2016
Asta Judzentiene, Rasa Garjonyte, Jurga Budiene
In this investigation of essential oils, electrochemical assay instead of spectrophotometry was proposed. Many antioxidants exhibit inherent electroactivity and can be easily oxidized at an inert electrode (Sochor et al., 2013). Carbon paste electrodes consisting of graphite and liquid binder (Kalcher et al., 2009) have a number of advantages such as chemical inertness, low cost, simple fabrication, low background currents, rapid renewal of the surface, and easy modification. Modified carbon pastes typically contain admixed water-insoluble compounds. Electrodes prepared from graphite and vegetable oils instead of usual inert binder (Apetrei et al., 2005) were suitable to examine the antioxidant properties of these oils. Voltammetric signals obtained under different conditions at these oil-modified carbon paste electrodes allowed discrimination of the oils from different plants. Similar methodology was used in this work to test the antioxidant properties of essential oils obtained from E. cannabinum. The oils were admixed to carbon paste prepared from graphite and paraffin oil.