Calculation Of Half-life Research Articles

Systematic Calculations of α-Decay Half-Lives Using Microscopic Deformed Potentials

A new version of the generalized density-dependent cluster model (GDDCM) is developed to describe an α particle tunneling through a deformed potential barrier. The microscopic deformed potential is numerically constructed in the double-folding model using the multipole expansion method. The decay width of an α-cluster state is evaluated using the integral of the quasi-bound state wave function, the scattering state wave function, and the difference of potentials. We perform a systematic calculation of α-decay half-lives for favored transitions in even-even nuclei ranging from Z=52 to Z=104. The calculated half-lives are in good agreement with the experimental values. The relation between nuclear deformations and α-decay half-lives is also discussed in details.

COMPETITION OF α DECAY AND HEAVY PARTICLE DECAY IN SUPERHEAVY NUCLEI

Calculations of half-lives of superheavy nuclei (SH) show an unexpected result: For some of them heavy particle radioactivity (HPR) dominates over α decay (branching ratios larger than 1). The new mass table AME11 and the theoretical KTUY05 and FRDM95 masses are used to determine Q-values. For Z = 124 we found isotopes with half-lives in the range of ns to ps.

Cluster decay of superheavy nuclei

Calculations of half-lives of superheavy (SH) nuclei show an unexpected result: for some of them cluster radioactivity (CR) dominates over $\ensuremath{\alpha}$ decay. We changed the concept of CR to allow emitted particles with ${Z}_{e}g28$ from parents with $Zg110$ (daughter around ${}^{208}$Pb). We find a trend toward shorter half-lives and larger branching ratios relative to $\ensuremath{\alpha}$ decay for heavier SHs. A table of measured masses along with theoretical tables are used to determine Q values.

Ethylene Glycol Elimination Kinetics and Outcomes in Patients Managed Without Hemodialysis

Ethylene glycol remains an important toxic cause of metabolic acidosis and acute renal failure. Traditionally, inhibition of alcohol dehydrogenase along with hemodialysis has been used for treatment. Because of reported long elimination half-life of ethylene glycol during alcohol dehydrogenase inhibition, hemodialysis has been used in patients who are otherwise doing well to clear ethylene glycol. We study ethylene glycol elimination kinetics in patients treated with fomepizole, but without hemodialysis. This was a retrospective, multicenter cohort study of patients older than 15 years who were treated at one of 3 medical centers during an 8-year period. Inclusion criteria were peak serum ethylene glycol concentration greater than 20 mg/dL, lack of renal failure on admission, treatment with fomepizole but without hemodialysis, and availability of serial serum ethylene glycol concentrations, allowing calculation of elimination half-life. The primary outcome variable was ethylene glycol elimination half-life; mortality and onset of renal failure were secondary outcome variables. During the study period, 85 patients were treated for ethylene glycol toxicity, of whom 40 met inclusion criteria. The mean serum ethylene glycol elimination half-life was 14.2 hours (SD=3.7 hours; 95% confidence interval 13.1 to 15.3 hours). One patient presented with metabolic acidosis on admission and developed mild transient renal insufficiency but did not require hemodialysis. No patient died. The mean elimination half-life of ethylene glycol in this population was shorter than previously reported without hemodialysis, and this select group of patients did well without enhanced elimination by hemodialysis.

α-decay systematics for superheavy elements

In this Brief Report we extend the \ensuremath{\alpha}-decay half-life calculation to the superheavy emitter region to verify whether these nuclei satisfy the recently observed systematics [D. N. Poenaru et al., Phys. Rev. C 83, 014601 (2011);C. Qi et al., Phys. Rev. C 80, 044326 (2009)]. To establish the systematics, we have used the \ensuremath{\alpha}-cluster potential description, which was originally developed to study $\ensuremath{\alpha}$ decay in connection with nuclear energy level structure [B. Buck et al., Phys. Rev. C 51, 559 (1995)]. The quantum-mechanical tunneling calculation has been employed to obtain the half-lives, showing that with this treatment the systematics are well reproduced in the region of heavy nuclei. Finally, the half-life calculation has been extended to the superheavy emitters to verify whether the systematics can still be observed.

In silico labeling reveals the time-dependent label half-life and transit-time in dynamical systems

BackgroundMathematical models of dynamical systems facilitate the computation of characteristic properties that are not accessible experimentally. In cell biology, two main properties of interest are (1) the time-period a protein is accessible to other molecules in a certain state - its half-life - and (2) the time it spends when passing through a subsystem - its transit-time. We discuss two approaches to quantify the half-life, present the novel method of in silico labeling, and introduce the label half-life and label transit-time. The developed method has been motivated by laboratory tracer experiments. To investigate the kinetic properties and behavior of a substance of interest, we computationally label this species in order to track it throughout its life cycle. The corresponding mathematical model is extended by an additional set of reactions for the labeled species, avoiding any double-counting within closed circuits, correcting for the influences of upstream fluxes, and taking into account combinatorial multiplicity for complexes or reactions with several reactants or products. A profile likelihood approach is used to estimate confidence intervals on the label half-life and transit-time.ResultsApplication to the JAK-STAT signaling pathway in Epo-stimulated BaF3-EpoR cells enabled the calculation of the time-dependent label half-life and transit-time of STAT species. The results were robust against parameter uncertainties.ConclusionsOur approach renders possible the estimation of species and label half-lives and transit-times. It is applicable to large non-linear systems and an implementation is provided within the PottersWheel modeling framework (http://www.potterswheel.de).

The contribution of skin contamination dose to the total extremity dose of nuclear medicine staff: First results of an intensive survey

Abstract During nuclear medicine procedures technologists are exposed to relatively high extremity doses as a result of manipulation of syringes and vials. These manipulations also involve a risk on contamination with liquids that have a relatively high specific activity. Despite the fact that contaminations should be avoided by hygienic measures, they can occur by accidental spills or as a result of cross-contamination. It should be stated that even minor contaminations can lead to major extremity doses especially in the case of beta-emitters. This means that contamination survey followed by decontamination, where appropriate, is needed in routine practise. Regular survey by workers asks for self-discipline, is time-consuming and consequently often neglected. Moreover, the use of common contamination monitors does not reveal reliable quantitative data that can be used in calculation of cumulated doses. In this study contaminations were monitored during a long-term survey with a protocol based on fast identification, localisation and quantification. During the first 5 months of the survey 300 inspections were carried out among 10 technologists. Contamination was found in 28 (9%) cases (23 99m Tc-labelled radiopharmaceuticals, 5 18 FDG). All detected contaminations were highly localised with values ranging from 185Bq to 440 kBq. The skin dose rates were calculated using different reference data and methods. The follow-up of individual contaminations resulted in the calculation of effective half-lives that are strongly radiopharmaceutical related. The use of these effective half-lives, the estimated exposure time and the reference data for dose rates resulted in a wide range of cumulated skin doses ranging from 8 μSv to 33 mSv. The first results of this survey indicate that extremity doses resulting from contaminations can have a large contribution to the total extremity dose of nuclear medicine technologists.

Comparison of biological stability and metabolism of CCK2 receptor targeting peptides, a collaborative project under COST BM0607

Stability of radiolabelled cholecystokinin 2 (CCK2) receptor targeting peptides has been a major limitation in the use of such radiopharmaceuticals especially for targeted radionuclide therapy applications, e.g. for treatment of medullary thyroid carcinoma (MTC). The purpose of this study was to compare the in vitro stability of a series of peptides binding to the CCK2 receptor [selected as part of the COST Action on Targeted Radionuclide Therapy (BM0607)] and to identify major cleavage sites. Twelve different 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA)-minigastrin/CCK conjugates were provided within an European COST Action (BM0607) by different laboratories and radiolabelled with (177)Lu. Their in vitro stabilities were tested in fresh human serum. Radiochemical yields (RCY) and intact radioligands for half-life calculations were determined by radio-HPLC. Matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) analysis of metabolites was performed to identify cleavage products using conjugates labelled with excess stable (nat)Lu, incubated in serum at 37°C. Urine metabolite analysis after injection in normal mice was performed by radio-HPLC analysis. Variable stability in human serum was found for the different peptides with calculated half-lives between 4.5 ± 0.1 h and 198 ± 0.1 h (n = 2). In urine of normal mice only metabolised peptide fragments were detected even at short times after injection for all peptides. MALDI-TOF MS revealed a major cleavage site of all minigastrin derivatives between Asp and Phe-NH(2) at the C-terminal end. Development of CCK2 receptor ligands especially for therapeutic purposes in patients with MTC or small cell lung cancer (SCLC) is still ongoing in different laboratories. This comparative study provided valuable insight into the importance of biological stability especially in the context of other results of this comparative trial within the COST Action BM0607.

Immunopharmacotherapeutic manifolds and modulation of cocaine overdose

Cocaine achieves its psychostimulant, reinforcing properties through selectively blocking dopamine transporters, and this neurobiological mechanism impedes the use of classical receptor-antagonist pharmacotherapies to outcompete cocaine at CNS sites. Passive immunization with monoclonal antibodies (mAb) specific for cocaine circumvents this problem as drug is sequestered in the periphery prior to entry into the brain. To optimize an immunopharmacotherapeutic strategy for reversing severe cocaine toxicity, the therapeutic properties of mAb GNC92H2 IgG were compared to those of its engineered formats in a mouse overdose model. Whereas the extended half-life of an IgG justifies its application to the prophylactic treatment of addiction, the rapid, thorough biodistribution of mAb-based fragments, including F(ab′)2, Fab and scFv, may correlate to accelerated scavenging of cocaine and reversal of toxicity. To test this hypothesis, mice were administered the anti-cocaine IgG (180mg/kg, i.v.) or GNC92H2-based agent after receiving an LD50 cocaine dose (93mg/kg, i.p.), and the timeline of overdose symptoms was recorded. All formats lowered the rate of lethality despite the >100-fold molar excess of drug to antibody binding capacity. However, only F(ab′)2-92H2 and Fab-92H2 significantly attenuated the progression of premorbid behaviors, and Fab-92H2 prevented seizure generation in a percentage of mice. The calculation of serum half-life of each format demonstrated that the pharmacokinetic profile of Fab-92H2 (elimination half-life, t1/2~100min) best approximated that of cocaine. These results not only confirm the importance of highly specific and tight drug binding by the mAb, but also highlight the benefit of aligning the pharmacokinetic and pharmacodynamic properties of the immunopharmacotherapeutic with the targeted drug.

SPONTANEOUS FISSION HALF-LIVES IN VARIOUS MACROSCOPIC-MICROSCOPIC MODELS

The problem of describing spontaneous fission for the entire region of superheavy nuclei is continually present in theoretical investigations. This study outlines the results of the calculations of fission barriers and spontaneous fission half-lives for superheavy nuclei in the region of Z =100-122 using a mean field model. We examine four distinct macroscopic models and two types of pairing interactions. Our approach is based on the deformed Woods-Saxon potential. Spontaneous fission half-lives are calculated using a multi-dimensional dynamical-programming method, where the action integral is minimized within a three dimensional deformation space (β2, β4, β6).

Tristetraprolin‐driven regulatory circuit controls quality and timing of mRNA decay in inflammation

For a successful yet controlled immune response, cells need to specifically destabilize inflammatory mRNAs but prevent premature removal of those still used. The regulatory circuits controlling quality and timing in the global inflammatory mRNA decay are not understood. Here, we show that the mRNA-destabilizing function of the AU-rich element-binding protein tristetraprolin (TTP) is inversely regulated by the p38 MAPK activity profile such that after inflammatory stimulus the TTP-dependent decay is initially limited to few mRNAs. With time, the TTP-dependent decay gradually spreads resulting in cumulative elimination of one third of inflammation-induced unstable mRNAs in macrophages in vitro. We confirmed this sequential decay model in vivo since LPS-treated mice with myeloid TTP ablation exhibited similar cytokine dysregulation profile as macrophages. The mice were hypersensitive to LPS but otherwise healthy with no signs of hyperinflammation seen in conventional TTP knockout mice demonstrating the requirement for myeloid TTP in re-installment but not maintenance of immune homeostasis. These findings reveal a TTP- and p38 MAPK-dominated regulatory mechanism that is vital for balancing acute inflammation by a temporally and qualitatively controlled mRNA decay.

SYSTEMATIC CALCULATION OF α-DECAY HALF-LIVES WITHIN GENERALIZED DENSITY-DEPENDENT CLUSTER MODEL

An improved version of the generalized density-dependent cluster model is presented to describe an α particle tunneling through a microscopic potential barrier. The microscopic potential is numerically constructed in the double folding model for both the Coulomb potential and the nuclear potential. The decay width is computed using the integral of the quasibound state wave function, the scattering state wave function, and the difference of potentials. We perform a systematic calculation of α-decay half-lives for even-even, odd-A, and odd-odd nuclei ranging from N = 84 to N = 126. The calculated α-decay half-lives are found to be in good agreement with the experimental values.

αdecay of even-even superheavy elements

The $\ensuremath{\alpha}$-decay half-lives of even-even superheavy elements within the range of proton number $104\ensuremath{\leqslant}Z\ensuremath{\leqslant}126$, which can be formed by possible cold and hot fusion reactions, are calculated in the framework of various approaches for $\ensuremath{\alpha}$-decay half-life evaluation and by using the $Q$ values of $\ensuremath{\alpha}$ transitions obtained within different approximations for atomic masses. The dependencies of $\ensuremath{\alpha}$-decay half-lives of superheavy elements on model approaches for both the $Q$ values and half-life calculations are discussed in detail.

Predicting the Global Crisis Recovery Period: Lessons from the 1997 Crisis

The objective of this paper is to identify the best indicator in forecasting the recovery period from the current global crisis for Malaysia. Initially, to determine the best indicator for the recovery period, we construct a simple forecasting model that incorporates three indicators: lagging, leading and coincidence indices, with two proxies of economic performance, macroeconomic and financial variables. We estimate a two-variable vector error correction model (VECM) using monthly and quarterly data covering the period 1980 to 2000. We alternate between the three indicators and we evaluate each model using out-of-sample forecast. Using the results of the initial process of analysis, we predict the recovery period of Malaysian economy from the current global economic crisis. It is found that lagging index is the best indicator of financial performance of the economy. From the half-life calculation base on error correction term, the study found that Malaysia was able to recover from the previous 1997 crisis within a two to four year period after the crisis. Given that the current crisis environment is similar to the previous 1997 crisis, a similar time period could apply to the current global crisis recovery.

Linear accelerator therapeutic dose—induced radioactivity dependence

Dependence between therapeutic dose and activity induced in mammal bones is discussed. This activity leads to gamma ray emission registered by HPGe detector and scintilation probe. Presented results are focused on activation which occurs during emission of 15 and 20 MV photon beams. The purpose is to describe how therapeutic conditions (dose, time of irradiation) influence the induced radioactivity. Preliminary studies of decay rate, calculation of half-life and identification of isotopes involved in this dynamic process are given.

Theoretical study on spherical proton emission

The proton radioactivity half-lives of spherical proton emitters are investigated within a generalized liquid drop model (GLDM), including the proximity effects between nuclei in a neck and the mass and charge asymmetry. The penetrability is calculated in the WKB approximation and the assault frequency is estimated by the quantum mechanism method considering the structure of the parent nucleus. The spectroscopic factor is taken into account in half-life calculation, which is obtained by employing the relativistic mean field (RMF) theory. The half-lives within the GLDM are compared with the experimental data and other theoretical values. The results show that the GLDM works quite well for spherical proton emitters when the assault frequency is estimated by the quantum mechanical method and the spectroscopic factor is considered.

Bupivacaine concentrations in the lumbar cerebrospinal fluid of patients during spinal anaesthesia

Data on bupivacaine concentrations in the cerebral spinal fluid (CSF) during spinal anaesthesia are scarce. The purpose of this study was to determine the concentration of bupivacaine in the lumbar CSF of patients with an adequate level of spinal anaesthesia after injection of plain bupivacaine 0.5%. Sixty patients with an adequate level of spinal block after standardized administration of plain bupivacaine 20 mg in men and of 17.5 mg in women were studied. To measure the CSF bupivacaine concentration, we performed a second lumbar spinal puncture and obtained a CSF sample at a randomized time point 5-45 min after the bupivacaine injection. In addition, we calculated the half-life of bupivacaine in the CSF and tested the hypothesis that the level of spinal block is related to the lumbar CSF bupivacaine concentration. Men and women had CSF bupivacaine concentrations ranging from 95.4 to 773.0 microg ml(-1) (median 242.4 microg ml(-1)) and from 25.9 to 781.0 microg ml(-1) (median 187.6 microg ml(-1)), respectively. The large variability of bupivacaine concentrations obtained at similar times after subarachnoid administration made calculation of a meaningful half-life of bupivacaine in CSF impossible. There was no association between CSF bupivacaine concentration and spinal block level, and CSF bupivacaine concentrations for the same spinal block level differed between patients by six-fold. There is a large variability of CSF bupivacaine concentrations in patients with an adequate level of spinal anaesthesia.

Pharmacokinetics of disappearance of cocaine from hair after discontinuation of drug use

Methods that employ detection of drugs of abuse in hair are important for monitoring compliance with drug abstinence. Understanding the mechanisms and timeline of drug disappearance from hair is critical for clinical and forensic application of hair testing. We aimed to evaluate the kinetics of disappearance of cocaine and its metabolite, benzoylecgonine (BE), from hair after discontinuation of drug use. Methods The Motherisk laboratory at the Hospital for Sick Children in Toronto routinely receives hair samples for toxicology analysis. Cocaine and BE hair results were obtained from the Motherisk Database for calculation of half-life of these compounds in hair. Subjects were included in the study if they had gradually decreasing concentrations of cocaine and/or BE in sequential hair samples, with higher levels in the 1–3 cm distal segments (i.e. earlier in time) and low or non-measurable levels in the segment closest to the scalp (i.e. closer to the date of sampling). Elimination half-life of cocaine and BE in hair was calculated using standard kinetics calculations. The study was anonymous, and received ethics approval by the Ethics Review Board of our institution. Results 137 subjects met the inclusion criteria for the study. The median half-life of cocaine in hair was 1.5 months (95% CI 1.2–1.8) in females and 1.5 months (95% CI 1.1–1.8) in males. The median half-life of BE was 1.5 months (95% CI 1.1–2) in females and 1.5 months (95% CI 0.8–1.8) in males. Half lives of cocaine or BE were not statistically different between males and females (Mann–Whitney U-test; P = 0.93 for cocaine, P = 0.99 for BE). Half lives of cocaine and BE were strongly correlated (Spearman rank rho = 0.73; P < 0.001). Conclusion Cocaine and BE could be detected in hair of former drug users for several months after abstinence. The calculated half-life of over 1 month for cocaine implies that, assuming first order elimination, approximately 3–4 months have to pass for hair testing to become negative in the segment proximal to the scalp. This finding should be incorporated in interpreting compliance with abstinence of former drug users, and suggests that caution has to be exerted when evaluating potential breaches of abstinence.

Proton radioactivity within a generalized liquid drop model

The proton radioactivity half-lives of spherical proton emitters are investigated theoretically. The potential barriers preventing the emission of protons are determined in the quasimolecular shape path within a generalized liquid drop model (GLDM) including the proximity effects between nuclei in a neck and the mass and charge asymmetry. The penetrability is calculated with the WKB approximation. The spectroscopic factor has been taken into account in half-life calculation, which is obtained by employing the relativistic mean field (RMF) theory combined with the BCS method with the force NL3. The half-lives within the GLDM are compared with the experimental data and other theoretical values. The GLDM works quite well for spherical proton emitters when the spectroscopic factors are considered, indicating the necessity of introducing the spectroscopic factor and the success of the GLDM for proton emission. Finally, we present two formulas for proton emission half-life calculation similar to the Viola-Seaborg formulas and Royer's formulas of $\ensuremath{\alpha}$ decay.

Transcutaneous measurement of glomerular filtration rate using FITC-sinistrin in rats

Inulin/sinistrin (I/S) clearance is a gold standard for an accurate assessment of glomerular filtration rate (GFR). Here we describe and validate an approach for a transcutaneous determination of GFR by using fluorescein-isothiocyanate-labelled sinistrin (FITC-S) in rats. Using a small animal imager, fluorescence is measured over the depilated ear of a rat after the injection of FITC-S. The decay curve of fluorescence is used for the calculation of half-life and GFR. The thus obtained transcutaneous data were validated by simultaneously performed enzymatic and fluorometric measurements in plasma of both FITC-S and sinistrin. The results of enzymatic sinistrin determination versus transcutaneous half-life of FITC-S or plasma fluorescence correlated well with each other (R(2) > 0.90). Furthermore, Bland-Altman analyses proved a good degree of agreement of the three methods used. The measurements performed in healthy animals as well as different models of renal failure demonstrate its appropriateness in a wide range of renal function. The transcutaneous method described offers a precise assessment of GFR in small animals. As neither blood and/or urine sampling nor time-consuming lab work is required, GFR can be determined immediately after the clearance procedure is finished. This method, therefore, simplifies and fastens GFR determinations in small lab animals compared to conventional bolus clearance techniques based on blood sampling. A low-cost device for the measurement of transcutaneous fluorescence intensity over time is under construction.