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Nanotechnology in Preventive and Emergency Healthcare
Published in Bhaskar Mazumder, Subhabrata Ray, Paulami Pal, Yashwant Pathak, Nanotechnology, 2019
Nilutpal Sharma Bora, Bhaskar Mazumder, Manash Pratim Pathak, Kumud Joshi, Pronobesh Chattopadhyay
Severe acute exposure, as in the case of nuclear explosion or accidental exposure to highly reactive industrial materials, may lead to single or multiple exposure of very high doses of radiation through external exposure or after entering into the body through wounds, oral intake, or respiratory exposure. Exposure in excess of 75 rad (unit of absorbed dose) in a short amount of time can cause acute health effects like radiation sickness. Radiation sickness is divided into four stages, namely the prodromal stage (N-V-D stage), the latent stage, the manifest illness stage, and recovery or death. While acute exposure to high doses of radiation can produce symptoms of radiation sickness, as discussed above, chronic exposure to low doses of radiation can have a negative effect on health, including damage to the thyroid gland and an increased risk of cancer. Long-term risks associated with exposure to radiation include lung fibrosis, skin burns, hypothyroidism, thyroiditis, cataracts, suppression of ovulation, suppression of sperm count, increased risk of cancers, as well as heritable genetic damage (Centers for Disease Control and Prevention, 2017a; US EPA, 2017).
Shielding Systems and Radiation Shields
Published in Robert E. Masterson, Nuclear Engineering Fundamentals, 2017
For a given photon energy, increasing the atomic number Z of the shielding material increases its ability to absorb photons. This is due to the effects of Compton scattering that were discussed in Chapter 17. This trend continues as the atomic number is increased because heavy elements have more electrons to scatter the photons than light elements do. However, at very high energies, even heavy materials can have a difficult time stopping an energetic photon. In Chapter 19, we will explore methods for measuring the amount of radiation that is able to penetrate a radiation shield. This will lead to a discussion of the units that are used to measure radiation exposure including the REM and the RAD. The RAD measures the total amount of energy the radiation deposits in a material, while the REM measures the biological effect of this radiation on the object that absorbs it.
Toxic Pollution
Published in Kimon Hadjibiros, Ecology and Applied Environmental Science, 2013
The following units are used to measure emitted or absorbed radioactive radiation: One Curie (Ci) is the radioactive radiation emitted by radioactive material that undergoes 37 billion nuclear transformations per second (the transformation rate of 1 gram of Radium-226). The submultiple units millicurie (mCi), microcurie (μCi), nanocurie (nCi) and picocurie (pCi) are used, each of which is one-thousandth of the previous one.The Becquerel (Bq) is equal to one nuclear transformation per second, therefore 1 Bq = 27 pCi.The rad (Roentgen-absorbtion-dose) is equal to an energy absorption of 100 ergs per gram of irradiated material.The rem (rad-equivalent-man) is also a unit of energy absorption, which takes into account its biological effects as a function of the type of radiation and its distribution in the human body. It is the dose that has the biological effects of 1 rad of x-rays and is determined by multiplying rad by a quality factor QF. A unit usually used for smaller doses is the millirem (mrem), i.e. one one-thousandth of a rem.
Measurement of Radiation Absorbed Dose Effects in SRAM-Based FPGAs
Published in IETE Journal of Research, 2022
T. S. Nidhin, Anindya Bhattacharyya, Aditya Gour, R. P. Behera, T. Jayanthi, K. Velusamy
SRAM-based FPGAs use CMOS process technology, so the knowledge about how the MOS devices are affected due to charge deposition is very much important. When the charged particles or high-energy photons interact with MOS devices [14–17], electron–hole pairs (ehps) will be generated along the track of the material [18]. The energy loss per unit length is expressed in stopping power or linear energy transfer (LET) and it is measured in MeV.cm2/g [12]. The total amount of energy deposited, which causes electron–hole pair production, is known as total ionization dose (TID). TID is measured in Rad or Gray which represents the energy absorbed per unit mass of a material. The mean energy required to ionize the material is dependent on the band gap of the target material and it is 3.6 eV for silicon and 17 eV for silicon dioxide [19]. The physical processes that lead from the initial deposition of energy by ionizing radiation to the creation of ionization defects are (1) the generation of ehps, (2) the prompt recombination of a fraction of the generated ehps, (3) the transport of free carriers remaining in the oxide and either (4a) the formation of trapped charge via hole trapping in defect precursor sites or (4b) the formation of interface traps via reactions involving hydrogen [20–22]. The damage caused in MOS devices are primarily due to the trapping of the charge in SiO2 and secondarily due to the trapping of the charge in the Si/SiO2 interface [23]. The building up of charge causes a change in the electronic parameters of MOS transistors. The most important parameter is threshold voltage (Vth) shift, other parameters are an increase of leakage current, reduction of drain–source breakdown voltage and a decrease in transconductance, etc. [24,25]. The increase in power supply current is one of the major failure modes in SRAM-based FPGAs and it is due to the leakage current and the transistors which are in off state turning on.