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Temperature Measurement
Published in Ethirajan Rathakrishnan, Instrumentation, Measurements, and Experiments in Fluids, 2020
This thermometer can be used for measuring a wide range of temperatures. At very low temperatures, helium is substituted for hydrogen, since helium has a lower condensation temperature. For high temperatures nitrogen is used instead of hydrogen. For use at temperatures higher than the melting point of glass, the bulb is made of platinum or a platinum–iridium alloy.
Units and Significant Figures
Published in Patrick F. Dunn, Fundamentals of Sensors for Engineering and Science, 2019
The SI base unit of mass is the kilogram (kg). This is the only base unit still defined in terms of an artifact. The international standard is a cylinder of platinum-iridium alloy kept by the International Bureau of Weights and Measures in Sèvres, France. A copy of this cylinder, a secondary standard, is at the NIST in Gaithersburg, Maryland, where it serves as the primary standard in the United States. The kilogram is the only SI base unit linked to a unique physical object. This will end soon when the kilogram is redefined in terms of a more accurate, atom-based standard [4].
Interfaces and the Concept of Surface Tension
Published in Andrew Terhemen Tyowua, Liquid Marbles, 2018
A vertical thin plate, as described in Figure 1.4a, is used. The plate is made of roughened platinum-iridium alloy or platinum. The plate is cleaned from organic contaminants by an organic solvent and then flamed with a Bunsen flame. Both roughening and cleaning of the plate surfaces help the test liquid to wet it perfectly, thus making θ = 0°. Glass, mica, and steel can be used in place of the alloy (Rusanov and Prokhorov 1996). This is particularly the case when the interfacial tension between heavy nonpolar liquids such as carbon tetrachloride and an immiscible, but lighter, polar liquid like water is to be measured. This usually requires the plate to be hydrophobic. This is achieved by using fluorinated polymers, which are inherently hydrophobic. In some cases, the surfaces of the alloy are made hydrophobic by coating them with organic amines and used for the experiment.
Recent advances in nuclear and hybrid detection modalities for image-guided surgery
Published in Expert Review of Medical Devices, 2019
Matthias N. Van Oosterom, Daphne D.D. Rietbergen, Mick M. Welling, Henk G. Van Der Poel, Tobias Maurer, Fijs W.B. Van Leeuwen
Two main detector setups are in use for γ probes: (1) a scintillation detector, which consists of a scintillation crystal coupled (directly or via optical fiber [107]) to a photomultiplier tube (PMT) or photodiode, or (2) an ionization detector, which consists of a semiconductor crystal structure. Next to having real-time sample times (typically <1 s), γ probes have been shown to allow for the identification of lesions as small as 2 mm [108]. To allow for spatial resolution, some form of collimation is needed around the detector setup to only allow radiation originating from the front-side of the γ probe to be detected. To achieve collimation, shielding of the detector with a certain thickness of a high-atom-number material is required. Lead and tungsten, or some sort of alloy of these materials, are the most generally used materials in collimators [106]. Given the relative stopping powers, however, gold and platinum might even be better alternatives; relative stopping powers of 1 (lead), 1.2 (tungsten (8% copper)), 1.6 (gold) and 1.7 (platinum (iridium alloy)) [109]. The collimator material also reflects on the size and weight of the collimator, where a typical collimator diameter for low-energy γ probes ranges between 10 and 12 mm. Even with the collimator in place, lesions with low radiopharmaceutical uptake can still be hard to distinguish when located in close proximity to high-uptake background tissues, typically denoted as the ‘shine-through’ problem. To this end, some groups have experimented with blocking background radiation (e.g. injection site) with the intraoperative use of additional lead-shielding [110,111].
Unified Dosimetry Quality Audit Index: an integrated Monte Carlo model-based quality assurance ranking for radiotherapy treatment of glioblastoma multiforme
Published in Radiation Effects and Defects in Solids, 2023
Praveen Kumar C, Lalit M. Aggarwal, Saju Bhasi, Neeraj Sharma
GBM 34: Patient case report illustrates the use of DBS electrode of platinum – Iridium alloy in the ratio of 0.75: 0.25 weight fraction, with a diameter of 0.127 cm. Density was assigned in the range of 21.56 g/cm3. Slab designation DBPI521 had computed values with dimensions as R = 2.4232 cm, Z = 0.0052250185 cm and mean excitation energy as 781.6 eV.
Systematic Component Investigation of the Steady-State High-Temperature In-Pile Nuclear Thermal Propulsion Experimental Test Bed
Published in Nuclear Technology, 2022
Tyler R. Steiner, Richard H. Howard
Melt wires were used to verify the thermocouple data. Each melt wire discussed in this section was sourced from a common platinum-iridium alloy. This alloy has a reported melting temperature of 2550 K (Ref. 5). An unused melt wire can be seen in Fig. 16.