Path integral Monte Carlo approach to the structural properties and collective excitations of liquid $$^3{\text {He}}$$ without fixed nodes

Due to its nature as a strongly correlated quantum liquid, ultracold helium is characterized by the nontrivial interplay of different physical effects. Bosonic $$^4{\text {He}}$$ 4 He exhibits superfluidity and Bose-Einstein condensation. Its physical properties have been accurately determined on the basis of ab initio path integral Monte Carlo (PIMC) simulations. In contrast, the corresponding theoretical description of fermionic $$^3{\text {He}}$$ 3 He is severely hampered by the notorious fermion sign problem, and previous PIMC results have been derived by introducing the uncontrolled fixed-node approximation. In this work, we present extensive new PIMC simulations of normal liquid $$^3{\text {He}}$$ 3 He without any nodal constraints. This allows us to to unambiguously quantify the impact of Fermi statistics and to study the effects of temperature on different physical properties like the static structure factor $$S({\mathbf {q}})$$ S ( q ) , the momentum distribution $$n({\mathbf {q}})$$ n ( q ) , and the static density response function $$\chi ({\mathbf {q}})$$ χ ( q ) . In addition, the dynamic structure factor $$S({\mathbf {q}},\omega )$$ S ( q , ω ) is rigorously reconstructed from imaginary-time PIMC data. From simulations of $$^3{\text {He}}$$ 3 He , we derived the familiar phonon–maxon–roton dispersion function that is well-known for $$^4{\text {He}}$$ 4 He and has been reported previously for two-dimensional $$^3{\text {He}}$$ 3 He films (Nature 483:576–579 (2012)). The comparison of our new results for both $$S({\mathbf {q}})$$ S ( q ) and $$S({\mathbf {q}},\omega )$$ S ( q , ω ) with neutron scattering measurements reveals an excellent agreement between theory and experiment.

Dynophore-Based Approach in Virtual Screening: A Case of Human DNA Topoisomerase IIα

In this study, we utilized human DNA topoisomerase IIα as a model target to outline a dynophore-based approach to catalytic inhibitor design. Based on MD simulations of a known catalytic inhibitor and the native ATP ligand analog, AMP-PNP, we derived a joint dynophore model that supplements the static structure-based-pharmacophore information with a dynamic component. Subsequently, derived pharmacophore models were employed in a virtual screening campaign of a library of natural compounds. Experimental evaluation identified flavonoid compounds with promising topoisomerase IIα catalytic inhibition and binding studies confirmed interaction with the ATPase domain. We constructed a binding model through docking and extensively investigated it with molecular dynamics MD simulations, essential dynamics, and MM-GBSA free energy calculations, thus reconnecting the new results to the initial dynophore-based screening model. We not only demonstrate a new design strategy that incorporates a dynamic component of molecular recognition, but also highlight new derivates in the established flavonoid class of topoisomerase II inhibitors.

Experimental Investigation and Numerical Simulation of C-Shape Thin-Walled Steel Profile Joints

The versatility of steel, its high resistance in relation to its low mass, as well as the easily accessible technology in the context of using recyclable materials and the low negative impact on the environment represent important arguments in using thin-walled steel profiles to make structures for buildings with a low height regime. This paper presents the results of an experimental program that investigated the behavior of three types of joints in a T-shape form made of thin-walled steel profiles to make shear wall panels or truss beam floors. Due to the small dimensions of the C-profiles of 89 × 41 × 12 × 1 mm, and of the technology of their joining, manufacturers prefer the hinged connections of elements with self-drilling screws. The purpose of the research presented in this paper is to assess the maximum capacity of the joints, the elastic and post-elastic behavior until failure, and also the mechanisms failure. The types of joints analyzed are commonly used in the production of structural systems for houses. The experimental program, which consisted of testing 5 specimens for each type of joint in tension (shear on screws), showed different behavior in terms of load-displacement. The experimental, tested models were analyzed by finite element simulations in an ANSYS nonlinear static structure with 3D solid models. The materials were defined by a bilinear true stress–strain curve obtained after some experimental tensile tests of the steel. The results of the experimental tests showed that the main failure mechanism is a yielding of the holes where the screws were mounted and a shearing of the profile walls. Adding an additional screw on each side increases the capacity of the joints, but not until a yield loss is obtained. In conclusion, it is shown that the solution is suitable for a low level of loading in a static manner; however, additional studies are necessary in order to develop and verify other solutions, thus improving the strength of the connection.

Multiphysics Modeling and Material Selection Methods to Develop Optimal Piezoelectric Plate Actuators for Active Noise Cancellation

The performance of a piezoelectric actuator for active noise cancellation depends primarily on the quality of the actuator material and its design approach, i.e., single-layer or multi-layer actuators, stacks, benders, or amplified actuators. In this paper, material selection and multiphysics modeling were performed to develop an optimal piezoelectric plate actuator for active noise cancellation. The material selection process was analyzed using two multi-criteria decision making (MCDM) approaches for material selection, i.e., figure of merit (FOM) for actuators and the technique for order of performance by similarity to ideal solution (TOPSIS). Of the 12 state-of-the-art piezoelectric actuator materials considered in this article, PMN–28% PT is the best material according to TOPSIS analysis, while (PIN24%-PMN-PT) is the best material according to FOM analysis. The ranking of state-of-the-art piezoelectric material categories for actuators according to the two analysis is consistent and the category of monocrystalline piezoelectric materials has the highest actuation performance. The multiphysics modeling was performed using ANSYS Mechanical using two different approaches: one using Ansys Parametric Design Language (APDL) command fragments, the other installing the PiezoAndMEMS ACT extension in ANSYS. Static structure, modal, and harmonic response analyses were performed to determine an optimal pair of piezoelectric plates to be used as an actuator for active noise cancellation. A pair of plates of the same materials, but of different dimensions turns out to be the optimal piezoelectric plate actuator for active noise reduction, according to the two multiphysics modeling methods.

Sensitivity of the Spool Rate on the Dynamic Response of the System

In rotodynamic systems, the rotor is spooled up from zero speed to its operating speed during the engine start. One of the considerations in design of rotating systems is the placement of rotor critical speed. It is vital to ensure that the rotor critical speeds are not close to the engine operating speed. However, it is not always possible to isolate all the frequencies above the operating speed. So, during the engine start to full speed, rotor system does travel through the mode. Therefore, to avoid a large system response, the rotor is spooled up quickly through the critical speed. In addition to the rotor critical speeds, the natural frequencies of the static structures may also get excited during the rotor spool up and spool down. The static structure response is one of the important considerations in designing a system for dynamic loading condition. It has been observed that the rotor spool rate affects the static structure response. This paper focuses on effect on system’s response under various spool rate. It has also been shown that the natural frequency of the system and damping in the system are two of the major factors towards sensitivity of system response with spool rate. Additionally, it has been observed that the presence of non-linearities shifts the peak response away from the natural frequency depending on the spool rate and spool direction.

Architecture of Intellectual System for Research of Space Weather Parameters

Has been carried out analysis of the subject area and main functions of the intellectual system for research of space weather parameters are identified. The model of static structure of intellectual system is developed as well as its dynamic aspects are modeled. Also is constructed an architecture of intellectual system for research of space weather parameters on the basis of “client-server” two-level model. The scientific novelty of the obtained results stands on developed model of the intellectual system for research of space weather parameters. The practical significance of the intellectual system lies in its capabilities: automated collection and processing of data on the manifestations of solar activity; storing information in the database; data analysis and establishing links between helio- and geo-activity indicators, as well as forecasting geophysical disturbances caused by cosmic factors.

“Navigating the Beautiful Tension”

The book’s conclusion draws together the seven ethnographic studies by arguing that evangelical worship is better understood as a theological culture than as a static structure. In contrast to the scholarship Kathryn Tanner and Molly Worthen, which understands the culture of Christianity and/or evangelicalism as an essentially contested concept, this chapter ultimately affirms the perspective of theologians John Webster and Kevin Vanhoozer, who understand evangelicalism eschatologically, as a unified diversity. When congregations gather in the presence of the living God, they are dislocated and re-established, changed into something they were not before the event began. Consequentially, corporate worship is not a peripheral “extra” tacked on to a fully formed spiritual/political/cultural movement, but rather the crucible in which congregations forge, debate over, and enact their unique contributions to the American mosaic known as evangelicalism.

Improving 1-propanol Force Field: a New Methodology

A new force field for 1-propanol, in the united and all atom models, has been obtained by combining two different empirical methodologies. The first was developed by scaling atom charges, and Lennard-Jones parameters to fit the dielectric constant, surface tension, and density ((2018) J. Chem. Theory Comput. 14:5949-5958). The second methodology consists of moving these parameters and together with the bond distance to obtain the liquid-vapor phase diagram of the CO2 molecule ((1995) J. Phys. Chem. 99:12021-12024). The last methodology is used to obtain the self-diffusion coefficient, which was not considered in the first one. With this new methodology, the experimental density, dielectric constant, surface tension, and self-diffusion coefficient at ambient temperature could be achieved. Furthermore, we show the temperature dependence of the aforementioned properties. The static structure factors are in accordance with the experimental spectrum. Solubility is increased to the experimental value for the united atom model after applying this methodology and for all atom scheme, the experimental solubility value is maintained.

Numerical study of a model of terahertz collective modes in DNA

Terahertz density fluctuations in DNA have been recognized to be associated with biological function of DNA and widely studied both experimentally and theoretically. In the present work, we investigate numerically a new model for the terahertz dynamics of density fluctuations in DNA, proposed earlier. This model considers the length scales corresponding to wave numbers up to the position of the maximum of the static structure factor and allows to reflect structural effects caused by the dependence of the static structure factor on wave number. We study the parametric dependencies of the model to elucidate the effect of dlocalization of the dynamics of density fluctuations caused by structural effects.