Penetration Probability Research Articles

Nuclear surface energy coefficients in α-decay

Within a modified unified fission model approach, the alpha decay half-lives of 108 even–even isotopes of heavy nuclei are studied first for the use of different nuclear surface energy coefficients (γ − MN76, γ − MN95, γ − MS67 and γ − MS00) entering in the calculation of proximity potential, for the use of two different forms of overlapping potentials, linear and second-order polynomial forms. Exact fitting of the half-lives for the isotopes of Ra, Th and U is obtained by introducing a parameter ▵R, which extends the touching point radius. A linear relation connecting this parameter ▵R and Q-value of the decay is obtained with a constraint to have a continuity of the potential in the overlapping and non-overlapping regions. For the use of this linear relation, half-life values are calculated for all the 108 even–even isotopes of heavy nuclei. The pre-existence probability is also calculated as the penetrability of the overlapping region for the use of two different forms of overlapping potentials, linear and second-order polynomial forms. The pre-existence probability and penetration probability calculations reveal the associated nuclear structure effects. Calculated half-lives for the use of different versions of nuclear surface energy coefficients, using both linear and polynomial overlapping potentials, compare well with the experimental values. Nuclear surface energy coefficient (γ − MS00 ) due to Myers and Swiatecki gives the least deviation. Further, for the use of both linear and polynomial overlapping potentials using the γ − MS00 version of the surface energy coefficient the half-lives of experimentally known superheavy elements are calculated and the calculations are also extended to predict half-lives of yet experimentally unknown nuclei.

Nanostraw-Mediated Intracellular Delivery: Direct Observation of Cell/Nanotube Interfaces

As a tool for massively parallel, high throughput molecular delivery, nanostructured platforms have emerged as a delivery technique with unique capabilities. Nanostructured platforms are able to access many different types of cells, even those that resist traditional techniques, and modern fabrication techniques can be used to introduce unique functionalities into individual nanowires or nanotubes on a platform, such as electrical access. Unfortunately, the active delivery process, including the number or percentage of nanostructures that participate, the time scale of delivery, and the mechanisms, whether endocytotic or directly penetrating, are still unknown. Using single event, nanowire-based methods, these important characteristics of delivery are difficult to study and the technique is effectively a black box. We previously reported on a system, the nanostraw platform, capable of time resolved deliveries and in situ observation. Here we introduce a technique using nanostraws to directly observe molecular deliveries to cells. Using a simple, two part delivery assay, we demonstrate not only the direct observation of nanostraw penetration into cells, but also the probability and frequency of cell penetration by nanostraws. We are also able to demonstrate how soon cells accept nanostraw access after plating. Using these nanostraw techniques, we can make the first direct observations of the dynamic high-aspect ratio nanostructure to cell interface during molecular delivery.

Computer simulation study of nanoparticle interaction with a lipid membrane under mechanical stress

Pore formation of lipid bilayers under mechanical stress is critical to biological processes. A series of coarse grained molecular dynamics simulations of lipid bilayers with carbon nanoparticles different in size have been performed. Surface tension was applied to study the disruption of lipid bilayers by nanoparticles and the formation of pores inside the bilayers. The presence of small nanoparticles enhances the probability of water penetration thus decreasing the membrane rupture tension, while big nanoparticles have the opposite effect. Nanoparticle volume affects bilayer strength indirectly, and particle surface density can complicate the interaction. The structural, dynamic, elastic properties and lateral densities of lipid bilayers with nanoparticles under mechanical stress were analyzed. The results demonstrate the ability of nanoparticles to adjust the structural and dynamic properties of a lipid membrane, and to efficiently regulate the pore formation behavior and hydrophobicity of membranes.

Reaction cross sections in heavy-ion collisions

Previously a compact formula for total reaction cross section for heavy-ion collisions as a function of energy was obtained by treating the angular momentum $l$ as a continuous variable. The accuracy of the continuum approximation is assessed and corrections are evaluated. The accuracy of the compact equation can be improved by a simple modification, if a higher accuracy is required. Simple rules to determine the barrier heights and the penetration probability for the $l$ partial wave from experimental data are presented, for the collision of identical or non-identical light nuclei.

Experimental estimation of the photons visiting probability profiles in time-resolved diffuse reflectance measurement

A time-gated intensified CCD camera was applied for time-resolved imaging of light penetrating in an optically turbid medium. Spatial distributions of light penetration probability in the plane perpendicular to the axes of the source and the detector were determined at different source positions. Furthermore, visiting probability profiles of diffuse reflectance measurement were obtained by the convolution of the light penetration distributions recorded at different source positions. Experiments were carried out on homogeneous phantoms, more realistic two-layered tissue phantoms based on the human skull filled with Intralipid–ink solution and on cadavers. It was noted that the photons visiting probability profiles depend strongly on the source–detector separation, the delay between the laser pulse and the photons collection window and the complex tissue composition of the human head.

Effect of hydrogen addition on the residual stress of B–C–N films with cubic boron nitride phase prepared by r.f. magnetron sputtering of a B4C target

The effect of hydrogen on the compressive residual stress of B–C–N films composed of amorphous B4C, hexagonal boron nitride (hBN), and cubic boron nitride (cBN) phases has been investigated. The films were basically deposited on silicon (100) substrates by sputtering of a B4C target with a gas mixture of Ar (25sccm), N2 (5sccm), and H2 (0–5sccm) at a chamber pressure of 0.27Pa. To improve the adhesive strength of the films, a compositional gradient B–C–N buffer layer, which was prepared by step-wise deposition with an increasing nitrogen flow rate from 0sccm to 4.5sccm in Ar/N2 mixed gas with a constant Ar flow rate of 25sccm, was adopted before the nucleation stage of the cBN phase. Up to 5sccm hydrogen was added to the Ar/N2 reactive gas after the deposition of the B4C layer with pure Ar gas. For all deposition conditions, hBN and cBN phases were observed to form in the B–C–N films. The cBN fraction in these films remained around 65%, irrespective of the amount of hydrogen added. However, the compressive stress of the B–C–N films was observed to rapidly decrease from 9.5GPa to 4.2GPa, with increasing the hydrogen flow from 0sccm up to 5sccm. The stress reduction is discussed in terms of the relation between the penetration probabilities of hydrogen and argon ions into the films, which was the main origin of the compressive residual stress of the compositional gradient B–C–N layer with hBN structure.

Glass transition dependence of ultrahigh strain rate response in amine cured epoxy resins

Ultrahigh strain rate performance in a series of model amine cured epoxy resins was investigated as a function of the glass transition temperature (Tg) of the cured polymer network, where the network Tg was systematically varied through the monomer stiffness, structure, and size. The high rate response was characterized in terms of a projectile penetration velocity, V50BL(P) (ballistic limit, protection criteria), which describes the projectile velocity with a 50% probability of sample penetration. One factor that dictates the ballistic performance of the epoxy networks, at effective rates of 104–105 s−1, is the difference between the measurement temperature and the glass transition temperature of the network. Sub-Tg relaxations did not have a measurable effect on ballistic performance, and neither did the monomer structure and functionality outside of the influence of the resin Tg, while off-stoichiometric (excess amine) formulations improved V50BL(P) slightly with high Tg epoxies. The results have implications in protective materials for military, aerospace, transportation, and construction industries, where high strain rate insults from airborne debris, high rate collisions, and natural events are increasingly considered during product design.

Cluster radioactivity using various versions of nuclear proximity potentials

The systematic study of doubly closed shell ${}^{208}\mathrm{Pb}$-daughter cluster radioactivity using different versions of proximity potentials within the preformed cluster-decay model is extended to daughter nuclei other than ${}^{208}\mathrm{Pb}$. The nuclear proximity potentials used in the calculation of total interaction potential cover a wide range of barrier characteristics. The decay half-life of the cluster changes significantly with the use of these different potentials because of the corresponding change in the preformation probability (${P}_{0}$) and penetration probability ($P$) of the cluster. The cluster radioactivity is worked out at touching as well as at an elongated neck configuration by taking the neck-length parameter $\ensuremath{\Delta}R=0.5$ fm. In order to observe the effect of deformation, the spherical fragmentation of clusters is also taken into account and the standard root-mean-square (rms) deviation is also compared for the various nuclear proximity potentials. It is observed that Prox 1977 reproduces the experimental half-lives very well at $\ensuremath{\Delta}R=0.5$ fm and further improves upon the value obtained in previous work. Thus Prox 1977 turns out to be a better option for studying the cluster decay of radioactive nuclei; however, the calculated half-lives of ${}^{14}\mathrm{C}$ clusters are still poor. With the use of mod-Prox 1988, having stronger isospin and asymmetry dependence, the comparison for ${}^{14}\mathrm{C}$ clusters improves significantly and the standard rms deviation from experimental half-lives comes out to be 1.01 and 1.46 for spherical and deformed choices of fragmentation, respectively. The standard rms deviation reported for various proximity potentials can be further improved if the precise experimental half-lives of 15, out of the 45 clusters used in present study, are made available. Till now only lower limits are available for these clusters. The barrier characteristics of various interaction potentials obtained using different nuclear proximity potentials are also explored in the context of ground-state cluster radioactivity. The new cases of ${}^{34}\mathrm{Si}$ decay of ${}^{238}\mathrm{U}$ and ${}^{14}\mathrm{C}$ and ${}^{15}\mathrm{N}$ decays of ${}^{223}\mathrm{Ac}$ are also included in the present study of 45 clusters. Predictions of half-lives of possible cluster decays in the trans-lead region are also made using Prox 1977. The deformation effect is included with optimum cold orientations.

Energetic particle injections to geostationary orbit: Relationship to flow bursts and magnetospheric state

To address the mechanism and factors controlling the injection of energetic particles to the geostationary orbit (GEO), we analyzed the appearance of injections at the GEO drift shell as observed by LANL spacecraft in the cases where the flow bursts and associated transient dipolarization were detected at the entry to the inner magnetosphere, in the high beta plasma sheet region on the nightside between 8 and 13 Re. We analyzed two different data sets, one including Geotail observations in 1995–2005 and another including a set of Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations in 2008–2009. We found that only a small portion of all flow bursts at 8–13 Re were associated with particle injection at GEO but that those injection‐associated flows had smaller values of plasma tube entropy parameter (PV5/3) as well as larger change of magnetic field north‐south component (dBz). This confirms a scenario that the bursty flows at the entry of the inner magnetosphere (8–13 Re) penetrate into GEO and produce there the energetic particles flux increase. According to the bubble theory of magnetotail plasma flows, the probability of the deep plasma penetration critically depends on how stretched the magnetospheric configuration is, and this dependence is statistically confirmed in a large database to be the major factor controlling the occurrence of GEO injections. We suggest using the background plasma tube entropy value in the nightside part of the GEO drift shell as a suitable parameter to predict the probability of particle injection to GEO. One more outcome of this study is that the energetic particle injections cannot reliably serve as a tool to identify the substorm onset times, as has been done in many past studies.

Half-life of bismuth isotopes predicted by the Coulomb and proximity potential model; a proposition for the spherical nuclei

We know that the ground state energy, half-life, spin and parity of the heavy nuclei can be determined via the study of alpha decay. Bearing this in mind, we have calculated the penetration probability in the barrier, the decay constant and thereby the half-lives of 21 isotopes of Bi by using the proximity potential model. The comparison with the existing data is motivating.

Clean energy: Revisiting the challenges of industrial policy

Large public investments in clean energy technology arguably constitute an industrial policy. One rationale points to market failures that have not been corrected by other policies, most notably greenhouse gas emissions and dependence on oil. Another inspiration for clean energy policy reflects economic arguments of the 1980s. It suggests strategic government investments would increase U.S. firms' market share of a growing industry and thus help American firms and workers. This paper examines the reasoning for clean energy policy and concludes that:•While a case can be made that subsidizing clean energy might help address market failures, the case may be narrower than some assert, and turning theory into sound practice is no simple feat.•An appropriate price on greenhouse gases is an essential precondition to ensuring efficient incentives to develop and deploy cost-effective emissions-abating technologies. However, efficient prices alone are unlikely to generate efficient levels of basic research and development by private firms.•Government investments in clean energy are unlikely to produce net increases in employment in the long run, in part because pushing home-grown technologies at taxpayers' expense offers no guarantee that the eventual products ultimately would not be manufactured somewhere else.•Spending on clean energy technologies is not well suited to fiscal stimulus.The authors recommend that:•Federal energy spending should invest in technologies with the lowest expected cost of abatement and highest probability of market penetration.•Funding decisions ought to be insulated – as much as possible – from rent-seeking by interest groups, purely political distortions, and the parochial preferences of legislators.

Preventing Endotracheal Cuff Rupture during Tracheostomy

Objective: 1) To demonstrate the importance of endotracheal tube (ETT) positioning in avoiding complications of ETT cuff penetration during tracheostomy. 2) To describe the author’s technique of ETT positioning. 3) To determine the probability of cuff penetration utilizing the technique in a 3D-computed tomography model. Method: From July 2008 to January 2012, 89 patients who had undergone tracheostomy using the mentioned technique in a tertiary hospital setting were evaluated. One hundred fifty random patient CT scans were chosen, measurements were taken, and probability of cuff penetration during virtual tracheostomy was generated. Primary outcome was ETT cuff penetration. Results: Over the period studied, 85/89 patients underwent tracheotomy without ETT cuff rupture by positioning the ETT just proximal to the carina after neck extension. After evaluating 150 random 3D-CT scans, it was determined that the average distance between the tracheotomy to superior aspect of cuff was 80 mm in males and 63.8 mm in females when a 6.5 sized ETT was utilized, and 70.2 mm in males and 54 mm in females when a 7.5 ETT was utilized. Virtual tracheotomy between the second and third tracheal rings resulted in no probability of inadvertent ETT cuff rupture. Conclusion: ETT cuff rupture is a common occurrence that may result in disastrous intraoperative complications during tracheostomy. This study serves to underscore the importance of ETT positioning and provides radiologic evidence for the author’s approach. Distal ETT positioning should be strongly considered for avoiding problems of ETT cuff rupture during tracheostomy.

Ballistic impact modeling of woven fabrics considering yarn strength, friction, projectile impact location, and fabric boundary condition effects

The combined effects of yarn tensile strength, inter-yarn friction, projectile impact location, and fabric clamping conditions on the probabilistic impact response of flexible woven Kevlar KM2 fabrics are studied using a 0.22caliber spherical projectile. The statistical nature of yarn tensile strength is accounted for by mapping Weibull strength distributions onto the individual yarns of the fabric model. Variability in projectile impact location relative to the yarns at the impact site is accounted for by randomly selecting one of 25 predetermined impact locations around a warp-fill yarn cross-over location at the center of the fabric. Five different inter-yarn friction levels are deterministically implemented, ranging from 0.0 to 0.4. Two boundary conditions are considered, 4-sided clamped and 2-sided clamped. Forty impact simulations are used to generate a probabilistic impact response (PVR) curve for each test case, describing the probability of fabric penetration as a function of projectile impact velocity. The fabric V50 velocity and impact performance variability were observed to decrease with increasing inter-yarn friction levels for the 4-sided clamped cases, while they increased for the 2-sided clamped cases.

Calculation of penetration probability across an arbitrary potential barrier in fusion reactions

The penetration probability across an arbitrary nucleus-nucleus potential barrier is studied by using transfer matrix approach, including continuous variations of effective mass. The calculated penetration probabilities for reaction ${}^{16}$O+${}^{208}$Pb are closed to those of WKB and modified Numerov calculations based on the Bass potential. With the transfer matrix approach, the influence of the effective mass on the penetration probability are simultaneously investigated. The calculations imply that the effective mass is an important quantity for studying the hindrance of fusion cross sections of some reactions at deep sub-barrier energies. The fusion cross sections of heavy-ion fusion reactions and the resonance phenomena due to double-hump barriers are also studied with this approach.

Thermally assisted penetration and exclusion of single vortex in mesoscopic superconductors

A single vortex overcoming the surface barrier in a mesoscopic superconductor with lateral dimensions of several coherence lengths and thickness of several nanometers provides an ideal platform to study thermal activation of a single vortex. In the presence of thermal fluctuations, there is nonzero probability for vortex penetration into or exclusion from the superconductor even when the surface barrier does not vanish. We consider the thermal activation of a single vortex in a mesoscopic superconducting disk of circular shape. To obtain statistics for the penetration and exclusion magnetic fields, slow and periodic magnetic fields are applied to the superconductor. We calculate the distribution of the penetration and exclusion fields from the thermal activation rate. This distribution can also be measured experimentally, which allows for a quantitative comparison.

Calculating probabilities without quadrature

It is shown that a direct method for bound states can give the integrated probability over a given region and also the normalised squared wavefunction at a given point without using any quadratures or wavefunction storage. The method is tested on a known example and is then applied to an asymmetric double well potential and also to find the probability of penetration of a particle into the non-classical region for a single well potential.

Cálculo da taxa de ionização por campo de um átomo próximo a uma superfície metálica: aplicação ao microscópio iônico de campo

Neste trabalho calculamos a taxa de ionização (probabilidade de ionização por unidade de tempo) para um átomo póximo a uma superficie metálica submetido a um campo elétrico uniforme. A probabilidade de penetração da barreira é calculada usando a aproximação WKB. Utilizando-se um modelo simples para a energia potencial do elétron externo do átomo, mas que contém as características física principais do problema, obtem-se uma expressão analítica para a taxa de ionização em função da distância átomo-superfície. Apresenta-se também de forma introdutória os princípios básicos de funcionamento do microscópio iônico de campo.

Finite element analysis of projectile size and shape effects on the probabilistic penetration response of high strength fabrics

The effects of projectile characteristics on the probabilistic impact response of single-layer fully-clamped flexible woven fabrics is numerically studied using a yarn-level fabric model with a statistical implementation of yarn strengths. Six small and large sized spherical, cylindrical, and conical projectiles of the same mass are considered. Probabilistic velocity response curves which describe the probability of fabric penetration as a function of projectile impact velocity are generated for each projectile type through a series of forty impact simulations at varying impact velocities. The probabilistic fabric impact response is observed to be strongly dependent on the shape of the projectile’s impact face and the manner of projectile–yarn interactions at the impact site.

Isospin asymmetry dependence of theαspectroscopic factor for heavy nuclei

Both the valence nucleons (holes) and the isospin asymmetry dependencies of the preformation probability of an \ensuremath{\alpha}-cluster inside parents radioactive nuclei are investigated. The calculations are employed in the framework of the density-dependent cluster model of an \ensuremath{\alpha}-decay process for the even-even spherical parents nuclei with protons number around the closed shell ${Z}_{0}$ $=$ 82 and neutrons number around the closed shells ${Z}_{0}$ $=$ 82 and ${Z}_{0}$ $=$ 126. The microscopic \ensuremath{\alpha}-daughter nuclear interaction potential is calculated in the framework of the Hamiltonian energy density approach based on the SLy4 Skyrme-like effective interaction. Also, the calculations based on the realistic effective M3Y-Paris nucleon-nucleon force have been used to confirm the results. The calculations then proceed to find the assault frequency and the \ensuremath{\alpha} penetration probability within the WKB approximation. The half-lives of the different mentioned \ensuremath{\alpha} decays are then determined and have been used in turn to find the \ensuremath{\alpha} spectroscopic factor. We found that the spectroscopic factor increases with increasing the isospin asymmetry of the parent nuclei if they have valence protons and neutrons. When the parent nuclei have neutron or proton holes in addition to the valence protons or neutrons, then the spectroscopic factor is found to decrease with increasing isospin asymmetry. The obtained results show also that the deduced spectroscopic factors follow individual linear behaviors as a function of the multiplication of the valence proton (${N}_{p}$) and neutron (${N}_{n}$) numbers. These linear dependencies are correlated with the closed shells core $({Z}_{0},{N}_{0})$. The same individual linear behaviors are obtained as a function of the multiplication of ${N}_{p}{N}_{n}$ and the isospin asymmetry parameter, ${N}_{p}{N}_{n}I$. Moreover, the whole deduced spectroscopic factors are found to exhibit a nearly general linear trend with the function ${N}_{p}{N}_{n}/({Z}_{0}+{N}_{0})$.

Effect of statistical yarn tensile strength on the probabilistic impact response of woven fabrics

The probabilistic impact response of flexible woven fabrics can be described through the V 0– V 100 or probabilistic velocity response (PVR) curve which describes the probability of fabric penetration as a function of projectile impact velocity. One source of variability that affects the probabilistic nature of fabric impact performance is the statistical distribution of yarn tensile strengths. In this paper the effects of the statistical yarn strength distribution characteristics on the probabilistic fabric impact response are computationally studied using five different strength distributions with differing mean strengths and distribution widths. Corresponding fabric PVR curves are generated for each strength distribution using a probabilistic computational framework that involves randomly mapping yarn strengths onto the individual woven yarns of a fabric finite element model and then running a series of impact simulations for the case of a four-sided clamped fabric impacted at the center by a spherical projectile.