Intrinsic Enrichment Research Articles

Mineral phases on the fracture of a glass particle and in the fines of a Luna 24 regolith sample

This paper reports new findings of native molybdenum and iron from Mare Crisium. Native tin, copper, and nickel were detected for the first time in this area of the lunar surface. Native tantalum and indium, intermetallic compound Ta2Mo, and barium titanate Ba2TiO4 were found for the first time on the Moon. The latter two phases were observed for the first time in nature. It was shown that the investigated mineral phases correspond to different genetic groups (preimpact, impact, and postimpact mineral assemblages), which is in general typical of lunar regolith. Based on the morphological features of the identified mineral phases, the history of the formation of impact glass particles was reconstructed in part. They were probably affected by at least three impact events. It was concluded that the peculiar molybdenum geochemical anomaly observed in a group of orange impact glass fragments was not related to the impactor material but rather to the intrinsic enrichment in molybdenum of lunar rocks (target) in the area of the impact events. It was supposed that this enrichment could be of exhalative (fumarole) nature.

A modified intrinsic enriched element free Galerkin method for multiple cracks simulation

In this work, the element free Galerkin method (EFGM) has been used to obtain the solution of multiple edge crack problems. The regular intrinsic enrichment approach used in EFGM has been modified to analyze and study the multiple crack problems. The modified approach provides a versatile technique to model multiple static as well as moving crack problems without any requirement of re-meshing. In this approach, the regular enrichment criterion has been modified to solve multiple interacting crack problems using linear elastic fracture mechanics (LEFM). Few test cases of multiple edge cracks lying on the same as well as on the opposite faces are solved under plane stress conditions. The results obtained by modified intrinsic enrichment technique are compared with those obtained by the diffraction criterion, analytical and FEM solutions. The values of mode-I and mode-II stress intensity factors have been evaluated by the interaction integral approach.

LULL1 Retargets TorsinA to the Nuclear Envelope Revealing an Activity That Is Impaired by theDYT1Dystonia Mutation

TorsinA (TorA) is an AAA+ ATPase in the endoplasmic reticulum (ER) lumen that is mutated in early onset DYT1 dystonia. TorA is an essential protein in mice and is thought to function in the nuclear envelope (NE) despite localizing throughout the ER. Here, we report that transient interaction of TorA with the ER membrane protein LULL1 targets TorA to the NE. FRAP and Blue Native PAGE indicate that TorA is a stable, slowly diffusing oligomer in either the absence or presence of LULL1. Increasing LULL1 expression redistributes both wild-type and disease-mutant TorA to the NE, while decreasing LULL1 with shRNAs eliminates intrinsic enrichment of disease-mutant TorA in the NE. When concentrated in the NE, TorA displaces the nuclear membrane proteins Sun2, nesprin-2G, and nesprin-3 while leaving nuclear pores and Sun1 unchanged. Wild-type TorA also induces changes in NE membrane structure. Because SUN proteins interact with nesprins to connect nucleus and cytoskeleton, these effects suggest a new role for TorA in modulating complexes that traverse the NE. Importantly, once concentrated in the NE, disease-mutant TorA displaces Sun2 with reduced efficiency and does not change NE membrane structure. Together, our data suggest that LULL1 regulates the distribution and activity of TorA within the ER and NE lumen and reveal functional defects in the mutant protein responsible for DYT1 dystonia.

RETRACTED ARTICLE: Fracture analysis using an enriched meshless method

Crack propagation and fatigue fracture is studied with an enriched meshless method. This method uses an intrinsic enrichment of the meshless weighting functions such that the correct crack kinematics can be described. The major advantage of the method is its simplicity, especially with respect to implementation. The method is applied to problems in elastostatics where analytical and experimental data is available. We show the higher accuracy of our method in comparison to standard methods for two problems with analytical solutions. Finally, we show the accuracy of the method for interacting flaws.

Orbital HP-Clouds for solving Schrödinger equation in quantum mechanics

Solving Schrödinger equation in quantum mechanics presents a challenging task in numerical methods due to the high order behavior and high dimension characteristics in the wave functions, in addition to the highly coupled nature between wave functions. This work introduces orbital and polynomial enrichment functions to the partition of unity for solution of Schrödinger equation under the framework of HP-Clouds. An intrinsic enrichment of orbital function and extrinsic enrichment of monomial functions are proposed. Due to the employment of higher order basis functions, a higher order stabilized conforming nodal integration is developed. The proposed methods are implemented using the density functional theory for solution of Schrödinger equation. Analysis of several single and multi-electron/nucleus structures demonstrates the effectiveness of the proposed method.

Meshfree point collocation method with intrinsic enrichment for interface problems

A meshfree collocation method with an intrinsic wedge enrichment is presented for solving interface problems. To approximate the class of functions with discontinuous derivatives on the interface, the wedge is asymptotically added to the basis functions. A general class of wedge basis functions with specified orders of asymptotic behavior at the interface is developed for moving least square approximations. These are implemented in diffuse derivative methods where the shape functions are approximately differentiated. The reproducing properties of these approximations for the polynomial part and for the wedge function along straight boundaries of the basis are demonstrated. For curved boundaries, the reproducing properties of the wedge functions are more restricted. Numerical results show the ease of constructing the intrinsic enrichment and the robustness of the numerical scheme in solving interface problems.

Enriched meshfree collocation method with diffuse derivatives for elastic fracture

A meshfree collocation method with intrinsic enrichment for solving elastic crack problems is presented. A diffuse derivative approximation is applied in conjunction with an intrinsic enrichment of the near-tip asymptotic fields and a polynomial basis. These consistent diffuse derivatives of the approximation do not require computing the derivative of the weight function or that of the moment matrix. The local behavior of the near-tip stresses is successfully captured so that the stress intensity factors can be accurately computed. Numerical experiments demonstrate the accuracy and robustness of the method for solving elastic fracture problems.

V453 Oph: a s-process enriched, but carbon-deficient RV Tauri star of low intrinsic metallicity

This paper reports the detection of a heavy element enriched RV Tauri variable with an abundance pattern that differs significantly from a standard s-process enriched object: V453 Oph. Based on optical high-resolution spectra, we determined that this object of low intrinsic metallicity ([Fe/H] = -2.2) has a mild, but significant, enrichment ([s/Fe] ∼ +0.5) of heavy elements for which the distribution points to slow neutron capture nucleosynthesis. This result is strengthened by a comparative analysis to the non-enriched RV Tauri star DS Aqr ([s/Fe] = 0.0). Although V453 Oph is the first RV Tauri star showing a strong s-process signature, it is not accompanied by C enhancement, challenging our current nucleosynthetic models of post-AGB stars that predict a simultaneous enrichment in C and s-process elements. The low N abundance excludes CN cycling as being responsible for the low C abundance. We explore three different scenarios to explain the heavy element distribution in this evolved object: an enrichment of the parental cloud, an accretion scenario in which the chemical patterns were acquired by mass transfer in a binary system and an intrinsic enrichment by dredge-up.

Smoothing, enrichment and contact in the element-free Galerkin method

The element-free Galerkin (EFG) method belongs to the class of mesh-free methods, which are well-suited to problems involving crack propagation due to the absence of any predefined element connectivity. However, the original visibility criterion used to model cracks leads to interior discontinuities in the displacements. Three methods for smoothing meshless approximations near nonconvex boundaries such as cracks are reviewed and compared: (1) the diffraction method, which wraps the nodal domain of influence a short distance around a point of discontinuity, such as a crack tip; (2) the transparency method, which gradually severs the domains of influence near crack tips; and (3) the “see-through” method, or continuous line criterion. Two techniques for enriching the EFG approximations near the tip of a linear elastic crack are also summarized and compared: extrinsic enrichment, in which special functions are added to the trial function; and intrinsic enrichment, in which the EFG basis is expanded by special functions. A contact algorithm based on a penalty method is also introduced for enforcing crack contact in overall compressive fields. Several problems involving arbitrary crack propagation are solved to illustrate the effectiveness of EFG for this class of problems.