Barrier Penetration Probability Research Articles

Molecular Docking Analysis for Screening of Cyclooxygenase-2 Inhibitors from Secondary Metabolite Compounds of Lactococcus lactis subsp. lactis (Lac3)

Inflammatory response plays important roles in both tumorigenesis and carcinogenesis. In this study, secondary metabolite compounds from Lactococcus lactis subsp. lactis (Lac3) were analyzed by LC-MS and the potential inhibition activity against the COX-2 receptor was screened through molecular docking and molecular dynamics (MD) analysis. Anti-inflammatory agents, mofezolac and ibuprofen, were used as positive control ligands. The result indicates a potential COX-2 inhibitor of 5-[(4-Amino-6-morpholin-4-yl-1,3,5-triazin-2-yl)amino]-2- methylbenzenesulfonate, which has a hydrogen bond on the active site Tyr385 of COX-2 with affinity energy of –9.0 kcal/mol. Moreover, another candidate of COX-2 inhibitor, designated as 3-Indolepropionic acid binds hydrogen on the important residue Ser530 of COX-2, with an affinity energy of –6.9 kcal/mol. To confirm the binding specificity, molecular docking analysis was also performed against COX-1. The binding stability and flexibility were confirmed using MD simulations. In addition, the toxicity and solubility of the potential ligands were predicted according to Lipinski’s rules and BOILED-Egg modeling. The 5-[(4-Amino-6-morpholin-4-yl- 1,3,5-triazin-2-yl)amino]-2-methylbenzenesulfonate shows the propensity for passive absorption through the gastrointestinal tract, whereas 3-Indolepropionic acid shows a high probability of blood-brain barrier penetration. In conclusion, this study identified potential compounds through molecular docking analysis which can be developed as COX-2 inhibitors.

Electric field and voltage fluctuations in the Casimir effect

The effects of reflecting boundaries on vacuum electric field fluctuations are treated. The presence of the boundaries can enhance these fluctuations and possibly lead to observable effects. The electric field fluctuations lead to voltage fluctuations along the worldline of a charged particle moving perpendicularly to a pair of reflecting plates, These voltage fluctuations in turn lead to fluctuations in the kinetic energy of the particle, which may enhance the probability of quantum barrier penetration by the particle. A recent experiment by Moddel {\it et al} is discussed as a possible example of this enhanced barrier penetration probability.

Effect of initial 3α cluster configurations in C12 on the direct decay of its Hoyle state

We investigate the implications of initial $3\ensuremath{\alpha}$ configurations in $^{12}\mathrm{C}$ corresponding to different decay modes of its Hoyle state on the penetrability ratios. Considering the second ${2}^{+}$ (10.03 MeV) state to be a collective excitation of the Hoyle state, the direct $3\ensuremath{\alpha}$ decay width for the Hoyle state has been calculated using the ratio of the barrier penetration probability of the Hoyle state to the ${2}^{+}$ state. Semiclassical Wentzel--Kramers--Brillouin (WKB) approximation has been employed to determine the penetrability ratio, resulting in an upper limit on the branching ratio of the direct decay of the Hoyle state in ``equal phase-space'' ($\mathrm{DD}\ensuremath{\phi}$) mode as $\frac{{\mathrm{\ensuremath{\Gamma}}}_{3\ensuremath{\alpha}}}{\mathrm{\ensuremath{\Gamma}}}<3.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$. However, this limit for ``linear chain'' (DDL) decay is $\frac{{\mathrm{\ensuremath{\Gamma}}}_{3\ensuremath{\alpha}}}{\mathrm{\ensuremath{\Gamma}}}<2.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$, which is one order of magnitude smaller than the $\mathrm{DD}\ensuremath{\phi}$ decay and the limit for ``equal energy'' (DDE) decay is $\frac{{\mathrm{\ensuremath{\Gamma}}}_{3\ensuremath{\alpha}}}{\mathrm{\ensuremath{\Gamma}}}<1.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$, which is greater than both $\mathrm{DD}\ensuremath{\phi}$ and DDL decays. It implies that the limit on direct decay probability is strongly dependent on the initial configuration of the $3\ensuremath{\alpha}$ cluster. A further probe using a bent-arm-like $3\ensuremath{\alpha}$ initial configuration shows that the direct decay probability is maximum when the angle of the bent arm is $\ensuremath{\approx}{120}^{\ensuremath{\circ}}$, an important ingredient for understanding the Hoyle-state structure.

Universal proton emission systematics

We investigate proton systematics in terms of the barrier penetration and formation probability. To this purpose we approximate the realistic proton-core interaction by a parabolic dependence describing the nuclear part matched to a pure Coulomb potential. In this way we can use analytic semiclassical solutions to describe the proton dynamics inside the barrier. We then carefully investigate effects induced by the centrifugal barrier and quadrupole deformation. It turns out that the nuclear centrifugal and deformation effects are much smaller than their Coulomb counterparts. On the other hand, the Coulomb action defining the semiclassical penetrability is larger by one order of magnitude than its nuclear counterpart. We evidence a dependence of the Coulomb action upon the Coulomb parameter in terms of two parallel lines separated by $A=145$. Such a dependence was previously discovered for the logarithm of the experimental decay width corrected by the Coulomb centrifugal barrier. We also evidence an additional but smaller residual linear decrease of the proton formation probability versus ${A}^{1/3}$ along two parallel lines separated by $A=145$, induced by the internal proton wave function. Therefore, the dependence between the experimental decay width corrected by the centrifugal barrier and the Coulomb penetrability multiplied by the proton formation probability in the doubly logarithmic scale can be fitted within a factor of two by a universal straight line.

A systematic study of alpha decay in actinide nuclei using modified generalized liquid drop model

The alpha decay half-lives of actinides within modified generalized liquid drop model (MGLDM) are investigated by the Wentzel–Kramers–Brillouin (WKB) barrier penetration probability. The potential barrier was studied taking in to account of nuclear proximity, coulomb interaction and centrifugal potential with the inclusion of angular momentum. This work predicts the alpha decay half-lives of unknown actinide nuclei such as [Formula: see text]Am, [Formula: see text]Cm, [Formula: see text]Bk, [Formula: see text]Es and [Formula: see text]No. The calculated alpha decay half-lives reproduce accurately the experimental data. The predictions provided for the alpha decay half-lives within the MGLDM may be helpful for identifying the new isotopes in this field.

Tunneling Calculation in the Field Ion Microscope

In this work we describe calculations of tunneling rate constants for the Field Ion Microscope (FIM) using one-dimensional model potential that simulates the ionization process in a FIM. We obtain expressions for the ionization rate constant (ionization probability per unit of time) of inert gas atoms as a function of their position above the surface. In order to calculate the probability of barrier penetration we have used the semiclassical (JWKB) approximation. We have also calculated ionization zone widths as the distance between points where ionization rate is a maximum and half of this value. An application to helium as the imaging gas is presented to highlight the power of the method.

Tunneling Calculation in the Field Ion Microscope

In this work we describe calculations of tunneling rate constants for the Field Ion Microscope (FIM) using one-dimensional model potential that simulates the ionization process in a FIM. We obtain expressions for the ionization rate constant (ionization probability per unit of time) of inert gas atoms as a function of their position above the surface. In order to calculate the probability of barrier penetration we have used the semiclassical (JWKB) approximation. We have also calculated ionization zone widths as the distance between points where ionization rate is a maximum and half of this value. An application to helium as the imaging gas is presented to highlight the power of the method.

Cluster decay half-lives and preformation probabilities

An improved semi-analytic approach to the barrier penetration probability is developed in the frame work of the Wentzel-Kramers-Brillouin (WKB) approximation. It is used to calculate decay half-lives and preformation probabilities for a set of 304 cluster emitters in the range 87 ≤ Z ≤ 96 and a set of 390 α-emitters in the range 52 ≤ Z ≤ 120. For cluster decay, the validity of our approach is tested against Coulomb and proximity potential model (CPPM) by comparing decay half-lives and barrier penetration probabilities. Our results are found to be in a good agreement with CPPM calculations and with the available experimental data. In case of α-decay, our calculations are tested against the experimental data and also a very good agreement is achieved. In both cases, results are also compared with calculations of some other well known universal decay laws that are used in many recent studies. Our approach shows a better agreement with experimental data than most of the other models. Our study is extended to calculate the assault frequency and preformation probability of the cluster inside the parent nucleus. A strong correlation is obtained for all these parameters with each other. Neutron shell closures are found to be more important in the cluster decay process than proton shell closure. It is also noted that the odd–even staggering behavior dominates the decay processes involving the emission of clusters with odd neutron number.

Semi-analytic calculations of barrier penetration and alpha particle preformation probabilities

An improved semi-analytic approach for the barrier penetration probability is developed in the framework of the Wentzel–Kramers–Brillouin approximation. It is used to calculate the α-decay half-life, assault frequency and α-preformation probability for many radioactive nuclei in the range Z = 52–99. Calculations are also extended to the super heavy region with Z = 100–120. Results are compared with the experimental data and some other recent studies. This approach achieves a better agreement with the experimental data than many other models. A strong correlation is found between the experimental decay half-life and the calculated penetration probability, assault frequency and preformation probability. Therefore, this approach achieves both reasonable accuracy and good consistency with the expected nuclear physical observations.

Theoretical studies on Alpha decay half-lives of Astatine isotopes

The half-life of a parent nucleus of Astatine isotopes [Formula: see text] decaying via alpha emission is investigated by employing Coulomb and proximity potential model (CPPM) using the WKB barrier penetration probability and other different analytical and semiempirical formulae of Royer, AKRE, Akrawy, RoyerB, MRoyerB, MRenB, SemFIS, VS and SLB. In the calculation of Alpha decay (AD) half-life the available experimental and theoretical [Formula: see text]-values with the total alpha kinetic energy have been considered. The behavior of hindrance factor with the variation of mass numbers of parent nuclei for isotopes in the range [Formula: see text] and the effect of magic number at closed shells were investigated. Through the comparison of obtained results from the systematics with the experimental data, the prediction of SemFIS formula was the best among the studied ones where it shows the minimum standard deviation of 0.829881.

Branching ratios of α-decay to ground and excited states of Fm, Cf, Cm and Pu

We use the well-known Wentzel–Kramers–Brillouin (WKB) barrier penetration probability to calculate α-decay branching ratios for ground and excited states of heavy even–even nuclei of Fermium (248–254Fm), Californium (244–252Cf), Curium (238–248Cm) and Plutonium (234–244Pu) with 94≤Zp≤100. We obtained the branching ratios for the excited states of daughter nucleus by the α-decay energy (Qα), the angular momentum of α-particle (ℓα), and the excitation probability of the daughter nucleus with the excitation energy of state ℓ in the daughter nucleus (i.e. Eℓ⁎). α-Decay half-lives have been evaluated by using the proximity potential model for the heavy even–even nuclei. We have reported the half-lives and compared the results with the experimental data. The theoretical branching ratios of α-transitions in our calculation are found to agree with the available experimental data well for 0→+ 0+, 0→+ 2+, 0→+ 4+, 0→+ 6+ and 0+ → 8+α-transitions.

Proton emission with a screened electrostatic barrier

Half-lives of proton emission for Z$\ge$51 nuclei are calculated within a simple analytical model based on the WKB approximation for the barrier penetration probability which includes the centrifugal and overlapping effects besides the electrostatic repulsion. The model has a single free parameter associated to a Hulthen potential which emulates a Coulomb electrostatic interaction only at short distance. The agreement with experimental data is very good for most of the considered nuclei. Theoretical predictions are made for few cases with uncertain emitting state configuration or incomplete decay information. The model's assignment of the proton orbital momentum is in agreement with the differentiation of the experimental data by orbital momentum values realized with a newly introduced correlation formula.

Correlation between alpha preformation probability, decay half-life and barrier assault frequency

Calculation of alpha particle preformation probabilities for some alpha emitters is considered in the framework of a recent proposed barrier penetration formula, by two different approximations. The behavior of alpha particle preformation probability with the variation of neutron and proton numbers of parent nuclei for isotopes, in the range [Formula: see text], and isotones, in the range [Formula: see text], is investigated. The same correlations are then studied for the alpha decay half-life, the barrier assault frequency, barrier height and barrier penetration probability. Strong correlations are found and in a good agreement with experimental expectations.

A systematic calculation of alpha decay half-lives using a new approach for barrier penetration probability

A systematic calculation of alpha decay half-lives of 347 nuclei is considered in the framework of the Wentzel–Kramers–Brillouin (WKB) approximation using two formulas. A recently proposed barrier penetration formula, with some modified parameters, is used first. Second, a new analytic barrier penetration formula is derived by taking into account the centrifugal potential. A good agreement with experimental data is achieved especially for spherical nuclei. The new formula reproduces experimental alpha decay half-lives with a satisfying accuracy especially for penetration energies much lower than the Coulomb barrier.

On atomic nuclear fusion processes at low temperatures. Enhancement of potential barrier transmission probability due to the so-called barrier anti-Zeno effect

It is known that in quantum mechanics the observation of an experiment may in some cases change the results of this experiment. In particular, this occurs for the so-called Zeno effect. It is shown that, unlike the standard Zeno effect for which observation reduces its probability, for a particle that penetrates a potential barrier the opposite situation (called the barrier anti-Zeno effect) can occur, i.e., observation can considerably increase the probability of barrier penetration. The possibility of utilizing the barrier anti-Zeno effect for explaining the paradoxical results of experiments on “cold nuclear fusion” that have been observed in various, including biological, systems is discussed. (According to the experimentalists who performed such studies, in these systems energy release that cannot be explained by any chemical processes, as well as changes of the isotope and even elemental composition of the studied substance, occur).

Heavy ion collision dynamics of10,11B+10,11B reactions

The dynamical cluster-decay model (DCM) of Gupta and collaborators has been applied successfully to the decay of very-light (A ∼ 30), light (A ∼ 40−80), medium, heavy and super-heavy mass compound nuclei for their decay to light particles (evaporation residues, ER), fusion-fission (ff), and quasi-fission (qf) depending on the reaction conditions. We intend to extend here the application of DCM to study the extreme case of decay of very-light nuclear systems 20,21,22Ne∗ formed in 10,11B+10,11B reactions, for which experimental data is available for their binary symmetric decay (BSD) cross sections, i.e., σBSD. For the systems under study, the calculations are presented for the σBSD in terms of their preformation and barrier penetration probabilities P0 and P. Interesting results are that in the decay of such lighter systems there is a competing reaction mechanism (specifically, the deep inelastic orbiting of non-compound nucleus (nCN) origin) together with ff. We have emipirically estimated the contribution of σnCN. Moreover, the important role of nuclear structure characteristics via P0 as well as angular momentum ℓ in the reaction dynamics are explored in the study.

Compound nucleus formation probabilityPCNdefined within the dynamical cluster-decay model

With in the dynamical cluster-decay model (DCM), the compound nucleus fusion/ formation probability PCN is defined for the first time, and its variation with CN excitation energy E* and fissility parameter χ is studied. In DCM, the (total) fusion cross section σfusion is sum of the compound nucleus (CN) and noncompound nucleus (nCN) decay processes, each calculated as the dynamical fragmentation process. The CN cross section σCN is constituted of the evaporation residues (ER) and fusion-fission (ff), including the intermediate mass fragments (IMFs), each calculated for all contributing decay fragments (A1, A2) in terms of their formation and barrier penetration probabilities P0 and P. The nCN cross section σnCN is determined as the quasi-fission (qf) process where P0=1 and P is calculated for the entrance channel nuclei. The calculations are presented for six different target-projectile combinations of CN mass A~100 to superheavy, at various different center-of-mass energies with effects of deformations and orientations of nuclei included in it. Interesting results are that the PCN=1 for complete fusion, but PCN <1 or ≪1 due to the nCN conribution, depending strongly on both E* and χ.

Dynamical decay of32S* and31P* formed in20Ne+12C and19F+12C reactions, respectively, atE*CN= 60 MeV

The target-like C-yield in the decay of compound systems 32 S ∗ and 31 P ∗ formed in 20 Ne+ 12 C and 19 F+ 12 C reactions at E ∗ CN=60 MeV, is studied for the contribution of fusion-fission (ff) decay cross section σ ff and the deep inelastic (DI) orbiting σorb from the compound nucleus (CN) and non-compound nucleus nCN processes, respectively. The calculations are performed using the collective clusterization of fragments within the dynamical cluster-decay model (DCM) of Gupta and collaborators. Besides studying the compe- tition between ff and DI orbiting phenomenon in the C-yield of these systems, we exclusively investigate the preformation and barrier penetration probabilities P0 and P as a function of angular momentumvalues which subsequently affects the contributions of σ ff and σorb. For calculating the contribution of σ ff in the C-yield, we have added the contributions from all the minimized intermediate mass fragments (IMFs) for Z= 6i n the calculated fragmentation potentials for 32 S ∗ (IMFs 11,12,13 C are minimized) and for 31 P ∗ (IMFs 12,13 C are min- imized), while calculating subsequently, P0 and the P for these IMFs. The distribution of preformed clusters/ fragments as a function of fragment mass visibly explore the nuclear structure effects for the C-yield in decay of these compound systems, wherein, it is shown to be more favoured in the decay of 31 P ∗ in comparison to 32 S ∗ decay. The contribution of σorb to the C-yield is calculated from P at different allowed � -values (uptomax and also P≤1) of the outgoing fragments (same as that in the entrance channel, i.e., P0=1). Though preliminary but useful results indicates the competition between the CN and nCN process in the C-yield for the compound system 32 S ∗ only while the decay of 31 P ∗ is of pure CN origin, as observed in the experimental study. The calculations are in good comparison with the available experimental data.

Compound nucleus formation probabilityPCNdetermined within the dynamical cluster-decay model for various “hot” fusion reactions

The compound nucleus (CN) fusion/formation probability ${P}_{CN}$ is defined and its detailed variations with the CN excitation energy ${E}^{*}$, center-of-mass energy ${E}_{\mathrm{c}.\mathrm{m}.}$, fissility parameter $\ensuremath{\chi}$, CN mass number ${A}_{CN}$, and Coulomb interaction parameter ${Z}_{1}{Z}_{2}$ are studied for the first time within the dynamical cluster-decay model (DCM). The model is a nonstatistical description of the decay of a CN to all possible processes. The (total) fusion cross section ${\ensuremath{\sigma}}_{\mathrm{fusion}}$ is the sum of the CN and noncompound nucleus (nCN) decay cross sections, each calculated as the dynamical fragmentation process. The CN cross section ${\ensuremath{\sigma}}_{CN}$ is constituted of evaporation residues and fusion-fission, including intermediate-mass fragments, each calculated for all contributing decay fragments (${A}_{1}$, ${A}_{2}$) in terms of their formation and barrier penetration probabilities ${P}_{0}$ and $P$. The nCN cross section ${\ensuremath{\sigma}}_{\mathit{nCN}}$ is determined as the quasi-fission (qf) process, where ${P}_{0}=1$ and P is calculated for the entrance-channel nuclei. The DCM, with effects of deformations and orientations of nuclei included in it, is used to study the ${P}_{CN}$ for about a dozen ``hot'' fusion reactions forming a CN of mass number $A\ensuremath{\sim}100$ to superheavy nuclei and for various different nuclear interaction potentials. Interesting results are that ${P}_{CN}=1$ for complete fusion, but ${P}_{CN}&lt;1$ or ${P}_{CN}\ensuremath{\ll}1$ due to the nCN contribution, depending strongly on different parameters of the entrance-channel reaction but found to be independent of the nuclear interaction potentials used.

Systematical calculation of α decay half-lives with a generalized liquid drop model

Abstract A systematic calculation of α decay half-lives is presented for even–even nuclei between Te and Z = 118 isotopes. The potential energy governing α decay has been determined within a liquid drop model including proximity effects between the α particle and the daughter nucleus and taking into account the experimental Q value. The α decay half-lives have been deduced from the WKB barrier penetration probability. The α decay half-lives obtained agree reasonably well with the experimental data.