Calculation Of Half-life Research Articles

Super-heavy nuclei

Scientifically based searches for elements beyond uranium started after the discovery of the neutron. Neutrons captured by uranium nuclei and subsequent decay, similarly as most of the elements were produced in nature, was the successful method applied. However, as a first result, Hahn and Strassmann discovered nuclear fission indicating a limit for the existence of nuclei at an increasing number of protons. Eventually, the nuclear shell model allowed for a more accurate calculation of binding energies, half-lives and decay modes of the heaviest nuclei. Theoreticians predicted a region of increased stability at proton number Z = 126, later shifted to 114, and neutron number N = 184. These nuclei receive their stability from closed shells for the protons and neutrons. Later, increased stability was also predicted for deformed nuclei at Z = 108 and N = 162. In this review I will report on experimental work performed on research to produce and identify these super-heavy nuclei (SHN). Intensive heavy ion beams, sophisticated target technology, efficient electromagnetic ion separators, and sensitive detector arrays were the prerequisites for discovery of 12 new elements during the last 40 years. The results are described and compared with theoretical predictions and interpretations. An outlook is given on further improvement of experimental facilities which will be needed for exploration of the extension and structure of the island of SHN, in particular for searching for isotopes with longer half-lives predicted to be located in the south east of the island, for new elements, and last not least, for surprises which, naturally, emerge unexpectedly.

Dose Calibrator Linearity Testing: Radioisotope (99m)Tc or (18)F? An Alternative for Reducing Costs in Nuclear Medicine Quality Control.

Dose calibrator linearity testing is indispensable for evaluating the capacity of this equipment in measuring radioisotope activities at different magnitudes, a fundamental aspect of the daily routine of a nuclear medicine department, and with an impact on patient exposure. The main aims of this study were to evaluate the feasibility of substituting the radioisotope Fluorine-18 (18F) with Technetium-99m (99mTc) in this test, and to indicate it with the lowest operational cost. The test was applied with sources of 99mTc (62 GBq) and 18F (12 GBq), the activities of which were measured at different times, with the equipment preadjusted to measuring sources of 99mTc, 18F, Gallium-67 (67Ga), and Iodine-131 (131I). Over time, the average deviation between measured and expected activities from 99mTc and 18F were, respectively, 0.56 (±1.79)% and 0.92 (±1.19)%. The average ratios for 99mTc source experimental activity, when measured with the equipment adjusted for measuring 18F, 67Ga, and 131I sources, in real values, were, respectively, 3.42 (±0.06), 1.45 (±0.03), and 1.13 (±0.02), and those for the 18F source experimental activity, measured through adjustments of 99mTc, 67Ga, and 131I, were, respectively, 0.295 (±0.004), 0.335 (±0.007), and 0.426 (±0.006). The adjustment of a simple exponential function for describing 99mTc and 18F experimental activities facilitated the calculation of the physical half-lives of the radioisotopes, with a difference of about 1% in relation to the values described in the literature. Linearity test results, when using 99mTc, through being compatible with those acquired with 18F, imply the possibility of using both radioisotopes during linearity testing. Nevertheless, this information, along with the high potential of exposure and the high cost of 18F, implies that 99mTc should preferably be employed for linearity testing in clinics that normally use 18F, without the risk of prejudicing either the procedure itself or the guarantee of a high-quality nuclear medicine service.

Systematic calculations of α-decay half-lives with an improved empirical formula

Based on the recent data in NUBASE2012, an improved empirical formula for evaluating α-decay half-lives is presented, in which the hindrance effect resulting from the change of the ground state spins and parities of parent and daughter nuclei is included, together with a new correction factor for nuclei near the shell closures. The calculated α-decay half-lives are found to be in better agreement with the experimental data, and the corresponding root-mean-square (rms) deviation is reduced to 0.433 when experimental Q-values are employed. Furthermore, the Q-values derived from different nuclear mass models are used to predict α-decay half-lives with this improved formula. It is found that the calculated half-lives are very sensitive to the Q-values. Remarkably, when mass predictions are improved with the radial basis function (RBF), the resulting rms deviations can be significantly reduced. With the mass prediction from the latest version of Weizsäcker–Skyrme (WS4) model, the rms deviation of α-decay half-lives with respect to the known data falls to 0.697.

Assessment of contaminant levels in fish from the Toronto waterfront area

The Toronto waterfront area of Lake Ontario is part of the Toronto and Region Area of Concern (AOC), partly due to elevated contaminant levels in fish and the resulting restrictive fish consumption advisories. Data collected by the Province of Ontario were used to investigate long-term (1975–2011) temporal trends of mercury, polychlorinated biphenyls (PCBs), mirex, and toxaphene levels in multiple fish species collected from the Toronto waterfront area. Recent (2000–2012) mercury and total PCB levels in fish from the Toronto waterfront area were compared to those for other regions, including other AOCs, of the Canadian waters of the Great Lakes. A similar comparison of fish PCB levels was also conducted for the Canadian AOCs for a historical scenario. Mercury and PCB levels in fish from the Toronto waterfront area demonstrated significant decreasing trends over time in multiple species, and recent mercury levels are well below the current consumption advisory benchmarks. In some cases, PCB levels remain above the current consumption advisory benchmarks and above the levels observed in fish from other AOC and non-AOC regions of the Canadian Great Lakes. Half-life calculations for these species indicate that it may take 8–26 years for total PCB concentrations in certain fish species to decrease below the current consumption advisory benchmarks. Sustained monitoring of PCBs in fish from the Toronto waterfront area is recommended to aid in ensuring that recovery continues.

Calculation of chemical elimination half-life from blood with an ongoing exposure source: The example of perfluorooctanoic acid (PFOA)

Determination of the chemical clearance rate from human blood is a critical component of toxicokinetic exposure assessment. Analysis of temporal biomonitoring data without consideration of ongoing exposure results in calculation of apparent elimination half-life values that are longer than the intrinsic value. The intrinsic elimination half-life is solely a function of the rate of elimination while the apparent elimination half-life reflects the processes of both elimination and ongoing exposure. Confusion between intrinsic and apparent half-life values can lead to misinterpretation of biomonitoring data and can result in exaggerated predictions in subsequent modeling efforts. This work provides a review of the first-order equations that have been developed to calculate intrinsic and apparent half-life values and the potential bias that can result from confusing these two values. Published human biomonitoring data for perfluorooctanoic acid (PFOA) are analyzed using these equations to provide examples of low, medium and high bias in determination of the intrinsic elimination half-life from plasma or serum, the components of blood typically analyzed for PFOA. An approach is also provided to estimate the extent of exposure reduction that is indicated by declining longitudinal or cross-sectional biomonitoring data. Based on the evaluation methodology presented in this work, the intrinsic elimination half-life of PFOA in humans is 2.4years, representing the average of independent estimates of 2.5years (95% CI, 2.4–2.7) and 2.3years (95% CI, 2.1–2.4). The declining concentration of PFOA in blood of the general USA adult population represents an estimated exposure reduction of 20–30% over the period 1999–2008.

Predictions for α-decay half-lives of heavy and superheavy elements with a generalized liquid drop model

Theoretical estimates for the lifetimes of several isotopes of heavy and superheavy elements with Z = 100–126 are performed in the framework of the generalized liquid drop model including the proximity effects, the mass and charge asymmetry. The α-decay half-lives calculated using the experimental Q-values were found to be in reasonable agreement with experimental data. Half-lives with the Q-values from the finite-range droplet model (FRDM) and the macroscopic–microscopic method (MMM) are presented for comparison. It is found that the half-life calculations are quite sensitive to the choice of Q-values. The results show that the half-lives obtained by the theoretical Q-values from MMM are better in agreement with experimental ones than those with Q-values from FRDM. Finally, some predications on the α-decay half-lives using the two kinds of theoretical Q-values are provided for future experimental assignment and identification.

Examining recombinant human TSH primed 131I therapy protocol in patients with metastatic differentiated thyroid carcinoma: comparison with the traditional thyroid hormone withdrawal protocol

Purpose Recombinant human thyroid-stimulating hormone (rhTSH)-based protocol is a promising recent development in the management of differentiated thyroid carcinoma (DTC). The objectives of this prospective study were: (1) to assess the feasibility and efficacy of the rhTSH primed 131I therapy protocol in patients with DTC with distant metastatic disease, (2) to perform lesional dosimetry in this group of patients compared to the traditional protocol, (3) to document the practical advantages (patient symptoms and hospital stay) of the rhTSH protocol compared to the traditional thyroid hormone withdrawal protocol, (4) to document and record any adverse effect of this strategy, (5) to compare the renal function parameters, and (6) to compare the serum TSH values achieved in either of the protocols in this group of patients.

α-decay half-life calculations of superheavy nuclei using artificial neural networks

Investigations of superheavy elements (SHE) have received much attention in the last two decades, due to the successful syntheses of SHE. In particular, α-decay of SHEs has a great importance because most synthesized SHE have a-decay and the experimentalists have evaluated the theoretical predictions of the a-decay half-life during the experimental design. Because of this, the correct prediction of α-decay half-life is important to investigate superheavy nuclei as well as heavy nuclei. In this work, artificial neural networks (ANN) have been employed on experimental a-decay half-lives of superheavy nuclei. Statistical modeling of a-decay half-life of superheavy nuclei have been found as to be successful.

Prediction of risk for symptomatic sialadenitis by post-therapeutic dual 131I scintigraphy in patients with differentiated thyroid cancer

The aim of this study is to predict the risk of symptomatic sialadenitis after (131)I therapy using the early (third day post-therapy) and delayed (fifth or sixth day post-therapy) post-therapeutic (131)I scintigraphy images in patients with differentiated thyroid cancer (DTC). Included in the study were 112 patients with DTC who underwent early and delayed (131)I scans after (131)I treatment. All patients had normal salivary gland function on salivary scintigraphy performed in the week before the (131)I treatment. Scintigraphy images were visually analyzed and the salivary gland-to-background uptake ratio (SUR) and percent change of the SUR between early and delayed scans were calculated. Calculation of effective half-life and absorbed dose in the salivary glands was performed based on the MIRD schema. Of 112 patients, symptomatic sialadenitis was diagnosed in 46 patients (41 %). Of these 46 patients, 83 % (38 patients) had persistent (131)I uptake in the salivary glands on both early and delayed scans. Among 55 patients with persistent (131)I uptake in the salivary glands, 69 % experienced symptomatic sialadenitis, while only 14 % of the other 57 patients experienced symptomatic sialadenitis (p < 0.0001). On the early (131)I scintigraphy, SURs of bilateral parotid glands on early scan in patients with symptomatic sialadenitis were significantly higher than in other patients (p = 0.001 for right and p = 0.004 for left). Further, patients with symptomatic sialadenitis had a higher decreasing rate of the SUR and shorter effective half-life of (131)I in bilateral parotid glands than other patients. Using visual analysis and SURs of right and left parotid glands on early (131)I scan as parameters, the sensitivities for predicting symptomatic sialadenitis were 83, 80, and 93 %, respectively. The mean values of effective half-life and absorbed dose in the parotid and submandibular glands were 20.8 ± 6.3 h and 2.7 ± 0.8 Gy, and 22.1 ± 7.9 h and 2.8 ± 1.1 Gy, respectively. Symptomatic sialadenitis can be predicted by post-therapeutic (131)I scintigraphy with high sensitivity. Post-therapeutic (131)I scintigraphy could provide effective information on the risk of symptomatic sialadenitis in DTC patients who underwent (131)I treatment.

Calculation of half-lives of cluster decay by using proximity potential with a new universal function

Abstract The half-lives of cluster decays are calculated using proximity potential model with a new universal function, and compared to the experimentally measured values and the theoretical ones of liquid drop model. The results of the present calculations show reasonable agreement with the experimental data as well as the half-life calculations of liquid drop model. In the present work, it is certified that proximity potential model with the new universal function can be used successfully to calculate the half-lives of cluster decays for heavy nuclei.

Theoretical predictions forα-decay chains ofZ=119isotopes in the region274≤A≤313

An extensive study on the \ensuremath{\alpha}-decay half-life for the isotopes of $Z$ = 119 superheavy nuclei in the range 274 \ensuremath{\le} $A$ \ensuremath{\le} 313 is performed within the Coulomb and proximity potential model for deformed nuclei (CPPMDN). We have also evaluated the decay properties by keeping the parents and daughter in spherical nuclear shape (without including the nuclear deformations), within the Coulomb and proximity potential model (CPPM). The half-life calculations are also performed by using the Viola-Seborg semi-empirical (VSS) relation, very frequently used for \ensuremath{\alpha}-decay studies, and it can be seen that our predictions agree well with the computed VSS values. Our intention to understand the mode of decay of the isotopes was fulfilled through the spontaneous fission (SF) half-life calculations and the comparison of the \ensuremath{\alpha} half-lives with the SF half-lives. Thus, our study reveals that those isotopes of $Z$ = 119 with $A$ \ensuremath{\ge} 309 and with $A$ \ensuremath{\le} 275 do not survive fission, and thus, the \ensuremath{\alpha} decay is restricted within the range of 276 \ensuremath{\le} $A$ \ensuremath{\le} 308. Through our study, we have predicted six consistent \ensuremath{\alpha} chains from ${}^{292--295}$119, five consistent \ensuremath{\alpha} chains from ${}^{296}$119, four consistent \ensuremath{\alpha} chains from ${}^{297}$119, and three consistent \ensuremath{\alpha} chains from ${}^{298,299}$119, and we hope these findings will provide a new guide for future experiments. A theoretical study is performed here to understand the mode of decay of the isotopes of $Z$ = 119, which helps to identify the mode of decay of about 40 isotopes within the range of 274 \ensuremath{\le} $A$ \ensuremath{\le} 313.

Heavy-particle radioactivity

The competition of heavy particle radioactivity (HPR) and α decay is investigated in the region of superheavy (SH) nuclei with atomic numbers Z = 104–124. Calculations of half-lives within analytical superasymmetrical fission (ASAF) model are performed by using different theoretical mass tables to determine Q, the energy released. For α decay the calculations are made using semi-empirical Fission (semFIS) model and AME11 mass table. A trend toward shorter half-lives and larger branching ratios relative to alpha decay for heavier SHs is observed.

Intra‐operative parathyroid hormone kinetics and influencing factors with high baseline PTH: a prospective study

Intra-operative parathyroid hormone (IOPTH) kinetics and therefore the efficacy of IOPTH utilization as a predictor of cure are likely to be affected by baseline IOPTH levels, vitamin D deficiency and parathyroid weight. Consecutive subjects with primary hyperparathyroidism (PHPT, n = 51) undergoing parathyroidectomy with IOPTH monitoring were studied prospectively during the period October 2009-November 2011. Samples were collected pre-incision, pre-excision and post-excision (5, 10, 15 min). Iterative analysis of IOPTH kinetics and half-life calculation was carried out in subgroups. Nonparametric testing was used for group statistics. Hypovitaminosis D (25(OH)D3 < 50 nm) was present in 39 (76%), serum PTH > 1000 ng/l in 23 (45%), and giant parathyroid adenoma (weight > 3000 mg) in 23 (45%). The percentage drop at 10 min was significantly higher in large adenomas (weight > 3000 mg). Miami and 5 min criteria showed the highest negative predictive value and maximum accuracy. The average percentage IOPTH drop observed at 5 min post-excision was 79.8%. Kinetic analysis showed a mean half-life of PTH of 2.57 ± 0.27 min (range: 0.07-11.55). IOPTH monitoring is reliable even in patients with extremely high baseline IOPTH value, with a greater percentage drop at 5 and 10 min post-excision. In patients with high baseline IOPTH, a 50% decay in PTH value at 5 min may be indicative of cure, obviating the need for 10 and 15 min samples. IOPTH kinetics are altered by adenoma weight but not affected by vitamin D status or baseline IOPTH levels.

Spontaneous fission half-lives of heavy and superheavy nuclei within a generalized liquid drop model

We systematically calculate the spontaneous fission half-lives for heavy and superheavy nuclei between U and Fl isotopes. The spontaneous fission process is studied within the semi-empirical WKB approximation. The potential barrier is obtained using a generalized liquid drop model, taking into account the nuclear proximity, the mass asymmetry, the phenomenological pairing correction, and the microscopic shell correction. Macroscopic inertial-mass function has been employed for the calculation of the fission half-life. The results reproduce rather well the experimental data. Relatively long half-lives are predicted for many unknown nuclei, sufficient to detect them if synthesized in a laboratory.

Systematic Calculations of α-Decay Half-Lives of Well Deformed Nuclei

We perform an extensive investigation on the α decay of heavy deformed even-even and odd-A nuclei within the multichannel cluster model. The dynamics effects of core nuclei are taken into account in dealing with the interaction matrix and the α-cluster formation. Enough decay channels are considered for convergence in solving the coupled equations. Systematic calculations have been performed for 36 even-even nuclei and 32 odd-A nuclei. The calculated results show good agreement with the available experimental data concerning total α-decay half-lives and branching ratios, including the branching ratios for high-spin states.

Improvements to TCE Microcosm Protocols for Biostimulation in Bedrock Aquifers

AbstractIn this study, a factorial‐designed experiment of biostimulated trichloroethene (TCE) dechlorination in fractured bedrock aquifers using microcosms evaluated several potential biostimulants (i.e., nutrients, vitamins, and sterile groundwater). Substantial cost savings and resource efficiency can be provided by this approach because: factorial designs require relatively few microcosms per factor; the interpretation of the observations can proceed largely by common sense, simple arithmetic, and computer graphics; the observations can indicate promising directions for further experimentation and causative relationships; and designs can be suitably augmented when a more in‐depth exploration is needed.TCE degradation was evaluated using three methods of data analysis: (1) analysis of covariance (ANCOVA) between biotic and abiotic treatment trend‐line slopes; (2) calculation of biodegradation half‐life; and (3) effects screening by model fitting. Microcosm preparation with crushed rock in groundwater was found to more closely match the previously observed field rates than the preparation with only groundwater. Injection of nutrient and vitamin mixtures was made into microcosms that were previously aged to obtain consistent conditions, and the TCE concentration measured after incubating for 45 days. Comparison of results indicated that the nutrient mixture slows or inhibits the degradation of TCE compared to the sterile groundwater; however, the vitamin mixture offsets and nearly compensates for the inhibitory effect of the nutrient mixture. It is recommended that this factorial experiment be augmented with additional studies of individual or groups of compounds from the vitamin mixture using this methodology to isolate and identify the specific factor or interaction responsible for the inhibitory compensation. © 2013 Wiley Periodicals, Inc.

Hooked to vitamin B12 since 1955: A historical perspective

In our pioneering work in 1956, two binders of vitamin B12 (B12) alias cobalamin (Cbl) were identified in gastric juice, S with slow electrophoretic mobility, a 70 kD protein with intrinsic factor (IF) activity and another rapid (R), not IF active but probable digestion product. Numerous sources contained a protein immunologically identical to R (haptocorrin, Hc). Another IF-active component (I) was found. Isoelectric focusing showed that S, I and R were assemblies of "isoproteins" with different pI's due to varying glycosidation. Isolation of S, I and R in microquantities was achieved in 1962 using a series of ion exchange chromatographies and gel filtration. Ponderable products were obtained in 1965-1966. The B12-IF complex was a dimer, contained 13% carbohydrate and showed a different absorption spectrum than B12. Using the Schilling test, B12 absorption was shown to require Ca(++), bound invitro to the ileal receptor and IF, but most of Ca(++) could be removed with sialidase. The receptor-substrate complex contained Ca(++) and carbohydrate. The purified receptor was shown to contain two main subunits. The Imerslund-Gräsbeck syndrome was discovered 1958-1960; it is caused by mutations in either of two genes, cubilin or amnionless, which form the multiligand receptor cubam. Testicular biopsies during and after B12-treated deficiency showed remarkable improvement after therapy. Studies of the turnover of radioactive B12 revealed biliary and fecal excretion, enterohepatic circulation and allowed calculation of biological half-life and daily need. The B12 coenzymes largely behaved like B12. To study whether radiocobalt in B12 was representative of the rest of the B12 molecule, (32)P and (57)Co labeled hydroxocobalamins were biosynthesized and shown to behave identically when given simultaneously to rats. The complex metabolism of B12 explains the pathogenesis of B12 deficiencies. Some of its mechanisms are not restricted to B12, e.g. the endocytosis of B12-IF also applies to other macromolecules.

Calculations of β-decay half-lives of proton-rich nuclei

We investigate the half-lives of beta(+)/EC (electron capture) decay using the proton-neutron quasiparticle random-phase approximation (pnQRPA) with a delta-form Gamow-Teller residual interaction. Both particle-hole and particle-particle residual interactions are consistently introduced in dealing with the pnQRPA matrix equation. The sensitivity of the calculated half-lives to some physical quantities used in the calculations is examined. Calculations are performed for even-even neutron-deficient isotopes ranging from Z = 10 to Z = 76. Good agreement between experiment and theory is achieved especially for the nuclei far from stability, and the results of our calculations are discussed with comparison with other theoretical results. Predictions on the beta-decay half-lives of some very neutron-deficient nuclei are also given for reference in future experiments.

Diagnosis and treatment of factor VIII and IX inhibitors in congenital haemophilia: (4th edition)

Peter W. Collins, Elizabeth Chalmers, Daniel P. Hart, Ri Liesner, Savita Rangarajan, Kate Talks, Mike Williams and Charles R. Hay School of Medicine, Cardiff University, University Hospital of Wales, Wales, Royal Hospital for Sick Children, Glasgow, The London School of Medicine and Dentistry, Royal London Hospital, Barts, Queen Mary University, London, Great Ormond Street NHS Trust, London, Hampshire Hospital NHS Foundation Trust, Basingstoke & North Hampshire Hospital, Basingstoke, Royal Victoria Infirmary, Newcastle upon Tyne, Birmingham Childrens’ Hospital NHS Foundation Trust, Birmingham and Central Manchester University Hospitals, Manchester, UK

Calculations of the β-decay half-lives of neutron-rich nuclei

The β-decay half-lives of neutron-rich nuclei have been systematically investigated using the proton–neutron quasiparticle random-phase approximation (pnQRPA) with a δ-form Gamow–Teller residual interaction. The particle–hole and particle–particle components of the Gamow–Teller residual interaction are consistently taken into account in dealing with the pnQRPA matrix equation, and the dependence of the results on them is discussed. Even–even nuclei with atomic numbers Z = 6–58 are considered in the calculations, where some newly measured neutron-rich nuclei are included. The calculated β−-decay half-lives are found to be in good agreement with the available experimental data. The comparison with other theoretical results is also given. Moreover, predictions on β-decay half-lives are made for some extremely neutron-rich nuclei, which could be useful for future experiments.