Fundamental properties of matter, radiation and radioactive decay
Damian Tolan, Rachel Hyland, Christopher Taylor, Arnold Cowen in Get Through, 2020
False – although beta decay tends to occur if there is an excess of neutrons, there are other forms of decay. In electron capture or positron emission a nucleus with an excess of protons will covert a proton into a neutron to achieve stability.True – the half-life of a radioactive nuclide is the time taken for its radioactivity to reduce to half its original value. Decay is an exponential process.False – they are inversely proportional. Half-life = loge2/decay constant.True – radioactive decay is not dependent on physical conditions.True – the mean lifetime is the time taken to decay to I/e (1/2.7182) of the initial activity. The mean lifetime is I/(decay constant), so it is (half-life)/(loge2), or about 1.44 times the half-life.
Dictionary
Mario P. Iturralde in Dictionary and Handbook of Nuclear Medicine and Clinical Imaging, 1990
Neutron. Elementary nuclear particle with a mass approximately the same as that of a hydrogen atom and electrically neutral; its mass is 1.008986 mass units. Outside a nucleus a neutron is radioactive, decaying with a half-life of about 12 min to give a proton and an electron. Neutrons are commonly divided into sub-classifications according to their energies as follows: thermal, around 0.025 eV; epithermal, 0.1 to 100 eV; slow, less than 100 eV; intermediated, 102 to 105 eV; fast, greater than 0.1 MeV. Since it has no charge it does not ionize and therefore has no fixed range in matter. It travels in straight line until it is either scattered or absorbed by a nucleus. A neutron with very little kinetic energy can interact very strongly with a nucleus since it is not repelled electrostatically by the positive nuclear charge.
Ion Beam Analysis: Analytical Applications
Vlado Valković in Low Energy Particle Accelerator-Based Technologies and Their Applications, 2022
Three isotopes of carbon are present in nature; 12C, 13C and 14C. 12C accounts for ~99.8% of all carbon atoms, 13C accounts for ~1% of carbon atoms while 14C represents only 1 ppb (one part per billion) of natural carbon. Carbon isotope 14C is radioactive and has a half-life of 5730 years. Because this decay is constant it can be used as a “clock” to measure elapsed time assuming the starting amount is known. A unique characteristic of 14C is that it is constantly formed in the upper atmosphere where neutrons from cosmic rays knock a proton from 14N atoms. These newly formed 14C atoms rapidly oxidize to form 14CO2 that is chemically indistinguishable from 12CO2 and 13CO2. Photosynthesis incorporates 14C into plants and therefore animals that eat the plants. 14C enters the dissolved inorganic carbon pool in the oceans, lakes and rivers. From there it is incorporated into shell, corals and other marine organisms. When a plant or animal dies it no longer exchanges CO2 with the atmosphere. This starts the radioactive decay “clock”. 14C decays by emitting an electron, which converts a neutron to a proton, converting it back to its original 14N form.
A practical guide to the interpretation of PK/PD profiles of longer-acting analogue insulins. Part one: The principles of glucose clamp studies
Published in Journal of Endocrinology, Metabolism and Diabetes of South Africa, 2018
Oppel BW Greeff, Jacob John van Tonder, Kershlin Naidu, Alicia McMaster, Alet van Tonder, Rashem Mothilal
The unique mode of protraction of longer-acting analogue insulins, including insulin glargine (Gla-300) and degludec (IDeg), results in extended duration of action. Gla-300 is soluble at acidic pH, and after injection into the subcutaneous tissue microprecipitates form a more compact soluble depot with smaller surface area in comparison with Gla-100, from which active monomers are steadily released.12 In contrast, IDeg form multi-hexamers after administration in the subcutaneous tissue resulting in the formation of a soluble depot from which active monomers are steadily released.13 The long half-life of these insulins translates into extended duration of action and therefore allows once-daily administration.2 Half-life refers to the time required for the original plasma concentration of an administered drug to be reduced by half, which is determined by the rate at which drug is eliminated from the central compartment (plasma). For drugs with an intravenous bolus dose administration the original plasma concentration is established very rapidly so the plasma concentration profile over time is mainly determined by the bolus dose and factors that influence the rate at which plasma concentration decreases, including the rate of metabolism and the rate of excretion.
Recent developments on foaming mechanical and electronic techniques for the management of varicose veins
Published in Expert Review of Medical Devices, 2019
C. Davide Critello, Salvatore A. Pullano, Thomas J. Matula, Stefano De Franciscis, Raffaele Serra, Antonino S. Fiorillo
Half-life, i.e. the time required to reduce the foam to 50% its initial liquid volume, is one of the most cited parameters for quantifying stability of sclerosing foams, even if other more clinically–relevant parameters are available in the literature [35]. Ex-vivo observations suggested that the efficacy of the sclerosants was concentration and time-dependent, asserting that at least a 1-min contact time of 3% STS in small veins (about 6 mm in diameter) could be sufficient to cause enough endothelial and media damage for inducing fibrosis [30]. Foam stability depends on multiple factors. For instance, the type of gas and the gas–liquid ratio can affect half-life because of the different gas solubilities in blood [36,37]. The addition of a viscosity enhancer (i.e., surfactant, polymer, or viscous liquid) can modify half-life slowing down the liquid drainage occurring between foam bubbles [38–41]. Other factors affecting stability can be bubble size, temperature, nature and concentration of sclerosing agent, and tools used to make foams [42–45].
Tacrine and its 7-methoxy derivate; time-change concentration in plasma and brain tissue and basic toxicological profile in rats
Published in Drug and Chemical Toxicology, 2021
Jana Zdarova Karasova, Ondrej Soukup, Jan Korabecny, Milos Hroch, Marketa Krejciova, Martina Hrabinova, Jan Misik, Ladislav Novotny, Vendula Hepnarova, Kamil Kuca
Standard noncompartmental analysis was performed using the Kinetica software, version 4.0 (InnaPhase Corporation, Thermo Fisher Scientific Inc., Waltham, MA). Maximum concentration (Cmax) and the time to the maximum concentration (Tmax) were determined directly from the observed data. The area under the mean plasma concentration–time curve from zero up to infinity (AUCtotal) was determined as the sum of the AUC0–24 min and of the extrapolated part, that is, the ratio of the concentration predicted at the time interval of 24 hours and the terminal rate constant λz. The λz was estimated using linear regression of the log-transformed concentrations at interval from 45 minutes to 24 hours plotted against time. The half-life was calculated as follows: t1/2 = ln(2)/λz. Other statistical analysis was performed using GraphPad Prism, version 5.0 (GraphPad Software, San Diego, CA).
Related Knowledge Centers
- Atom
- Chemical Kinetics
- Chemical Reaction
- Radioactive Decay
- Rate Equation
- Biological Half-Life
- Doubling Time
- Expected Value
- Atomic Nucleus
- Reaction Rate Constant