Exact Modes Research Articles

Crystal Structure of LSD1 in Complex with 4-[5-(Piperidin-4-ylmethoxy)-2-(p-tolyl)pyridin-3-yl]benzonitrile.

Because lysine-specific demethylase 1 (LSD1) regulates the maintenance of cancer stem cell properties, small-molecule inhibitors of LSD1 are expected to be useful for the treatment of several cancers. Reversible inhibitors of LSD1 with submicromolar inhibitory potency have recently been reported, but their exact binding modes are poorly understood. In this study, we synthesized a recently reported reversible inhibitor, 4-[5-(piperidin-4-ylmethoxy)-2-(p-tolyl)pyridin-3-yl]benzonitrile, which bears a 4-piperidinylmethoxy group, a 4-methylphenyl group, and a 4-cyanophenyl group on a pyridine ring, and determined the crystal structure of LSD1 in complex with this inhibitor at 2.96 Å. We observed strong electron density for the compound, showing that its cyano group forms a hydrogen bond with Lys661, which is a critical residue in the lysine demethylation reaction located deep in the catalytic center of LSD1. The piperidine ring interacts with the side chains of Asp555 and Asn540 in two conformations, and the 4-methylphenyl group is bound in a hydrophobic pocket in the catalytic center. Our elucidation of the binding mode of this compound can be expected to facilitate the rational design of more-potent reversible LSD1 inhibitors.

Influence of Crack on Modal Parameters of Cantilever Beam Using Experimental Modal Analysis

In this paper, the dynamic behavior of a cantilever beam without and with crack is observed. An elastic Aluminum cantilever beams having surface crack at various crack positions are considered to analyze dynamically. Crack depth, crack length and crack location are the foremost parameters for describing the health condition of beam in terms of modal parameters such as natural frequency, mode shape and damping ratio. It is crucial to study the influence of crack depth and crack location on modal parameters of the beam for the decent performance and its safety. Crack or damage of structure causes a reduction in stiffness, an intrinsic reduction in resonant frequencies, variation of damping ratios and mode shapes. The broad examination of cantilever beam without crack and with crack has been done using Numerical analysis (Ansys18.0) and experimental modal analysis. To observe the exact higher modes of beam, discretize the beam into small elements. An experimental set up was established for cantilever beam having crack and it was excited by an impact hammer and finally the response was obtained using PCB accelerometer with the help sound and vibration toolkit of NI Lab-view. After obtaining the Frequency response functions (FRFs), the natural frequencies of beam are estimated using peak search method. The effectiveness of experimental modal analysis in terms of natural frequency is validated with numerical analysis results. This paper contains the study of free vibration analysis under the influence of crack at different points along the length of the beam.

Apocalypse Masque: Post-Electric Theatricality inMr. Burns

How does a society survive through its stories, after the death of the technologies that embodied those narratives? This is the question that drives Anne Washburn’s 2012 play Mr. Burns. She posits a landscape in apocalyptic shadow, a post-electric New England where the power plants have failed and wanderers gather around campfires to trade lists of lost loved ones and whatever tales they can remember from the defunct world of television. Over the course of three acts, a single episode from The Simpsons becomes a bardic solace for a fractured society, then (a few years later, when troupes are paid to perform fading episodes from the show) an economic structure through which hope and nostalgia are exchanged, and, finally, in the distant future, a fully ritual theatre in which its previous purposes have attained a religious level of abstraction. Washburn’s concern is thus the way intertextual weaving and viral reproduction—starting with The Simpsons’s own mélange of borrowings from sources as distant as classic cinema and Victorian musicals—serve a post-truth society without access to exact mechanical modes of replication and transmission, preserving a text and the history it carries even through the process of mutation.

Rigorous decoupling between edge states in frustrated spin chains and ladders

We investigate the occurrence of exact zero modes in one-dimensional quantum magnets of finite length that possess edge states. Building on conclusions first reached in the context of the spin-1/2 XY chain in a field, then for the spin-1 $J_1-J_2$ Heisenberg model, we show that the development of incommensurate correlations in the bulk invariably leads to oscillations in the sign of the coupling between edge states, hence to exact zero energy modes at the crossing points where the coupling between the edge states rigorously vanishes. This is true regardless of the origin of the frustration (e.g. next-nearest neighbor coupling or biquadratic coupling for the spin-1 chain), of the value of the bulk spin (we report on spin-1/2, spin-1 and spin-2 examples), and of the value of the edge-state emergent spin (spin-1/2 or spin-1).

Self-trapping under two-dimensional spin-orbit coupling and spatially growing repulsive nonlinearity

We elaborate a method for the creation of two- and one-dimensional (2D and 1D) self-trapped modes in binary spin-orbit (SO)-coupled Bose-Einstein condensates (BECs) with the contact repulsive interaction, whose local strength grows fast enough from the center to periphery. In particular, an exact semi-vortex (SV) solution is found for the anti-Gaussian radial-modulation profile. The exact modes are included in the numerically produced family of SV solitons. Other families, in the form of mixed modes(MMs), as well as excited state of SVs and MMs, are produced too. While the excited states are unstable in all previously studied models, they are partially stable in the present one. In the 1D version of the system, exact solutions for the counterpart of the SVs, namely, \textit{semi-dipole} solitons, are found too. Families of semi-dipoles, as well as the 1D version of MMs, are produced numerically.

Dynamics of transversally vibrating non-prismatic Timoshenko cantilever beams

The present study deals with evaluation of the dynamic response in a pulse loaded homogeneous non-prismatic Timoshenko cantilever beam. Subsequent to the derivation of the partial differential equations (PDE’s) of motion using the Lagrange-d’Alembert principle (or extended Hamilton’s principle) the eigenvalue problem has been set up and solved for eigenfrequencies and eigenfunctions. Galerkin’s method of weighted residuals was then applied to obtain governing ordinary differential equations (ODE’s) for the system. The dynamic response under arbitrary pulse loading is obtained using the method of eigenfunction expansion which attributes to displacement and rotation fields generalised coordinates when the exact modes are chosen as shape functions. It has been shown that inclusion of few terms (in this case 5) in the series expansion provides a good correlation between the displacement fields and the truncated series. Dimensionless response parameters are introduced and two methods of non-dimensionalisation are proposed which could be useful in dealing with generic problems of a specified formulation.

Dispersion characteristics of V-band radial-line backward-wave oscillators with arbitrary periodic shallow rectangular grooves

The dispersion characteristics of radial-line slow wave structures with shallow rectangular grooves are examined using the Borgins's potential function method. The whole structure is considered as one region with grooves that satisfy the Rayleigh criterion. In this region, an appropriate Fourier expansion of traveling waves is applicable. By applying suitable boundary conditions, the dispersion equations of an infinite system are obtained, which are solved numerically by calculation and simulation. Comparisons of analytic and numerical results with calculation and simulation show excellent agreement and justify a high degree of confidence in the validity of the theory. The Q-factor and coupling impedance of TM02 mode are higher than that of TM01 mode and that of the quasi-TEM mode with special parameters, while the starting current of TM02 mode is lower than that of TM01 and quasi-TEM modes, which makes the TM02 mode dominate over the start-up of the oscillation. Structural parameters, including period length, corrugation depth, and tube width as well as original radius are considered in detail to choose the exact operating frequency and modes of V-band radial-line backward-wave oscillators (BWOs). More importantly, the presented new dispersion equations can provide a theoretical guidance for the design of V-band radial-line BWOs.

Quantum heating as an alternative of reheating

To model a realistic situation for the beginning we consider massive real scalar $\phi^4$ theory in a (1+1)-dimensional asymptotically static Minkowski spacetime with an intermediate stage of expansion. To have an analytic headway we assume that scalars have a big mass. At past and future infinities of the background we have flat Minkowski regions which are joint by the inflationary expansion region. We use the tree-level Keldysh propagator in the theory in question to calculate the expectation value of the stress-energy tensor which is, thus, due to the excitations of the zero-point fluctuations. Then we show that even for large mass, if the de Sitter expansion stage is long enough, the quantum loop corrections to the expectation value of the stress-energy tensor are not negligible in comparison with the tree-level contribution. That is revealed itself via the excitation of the higher-point fluctuations of the exact modes: During the expansion stage a non-zero particle number density for the exact modes is generated. This density is not Plankian and serves as a quench which leads to a thermalization in the out Minkowski stage.

Transmission of Helicobacter pylori.

The exact modes and routes of transmission of Helicobacter pylori (H. pylori) infection remain unproven. Studies showed that H. pylori bacteria can spread directly from one person to the other, or indirectly from an infected person to the environment. Presently, interpersonal pathways are more probable than environmental exposure routes. Person to person transmission can be mainly fecal-oral or oral-oral. In the last 30 years many authors have investigated the main potential sources of H. pylori infections, vectors and risk factors for both fecal-oral and oral-oral routes of transmission, eating of contaminated food, drinking of contaminated water, and exposure to animals. They have tried to isolate H. pylori from feces, saliva, dental plaque. These aspects are the basis for the effective prevention of both H. pylori acquisition and gastroduodenal pathology associated with it. These issues will be discussed in this narrative review.

Exact vibration analysis of a double-nanobeam-systems embedded in an elastic medium by a Hamiltonian-based method

A new Hamiltonian-based approach is presented for finding exact solutions for transverse vibrations of double-nanobeam-systems embedded in an elastic medium. The continuum model is established within the frameworks of the symplectic methodology and the nonlocal Euler-Bernoulli and Timoshenko beam beams. The symplectic eigenfunctions are obtained after expressing the governing equations in a Hamiltonian form. Exact frequency equations, vibration modes and displacement amplitudes are obtained by using symplectic eigenfunctions and end conditions. Comparisons with previously published work are presented to illustrate the accuracy and reliability of the proposed method. The comprehensive results for arbitrary boundary conditions could serve as benchmark results for verifying numerically obtained solutions. In addition, a study on the difference between the nonlocal beam and the nonlocal plate is also included.

Multi-Stage Tunable Approximate Search in Resistive Associative Memory

General-purpose graphics processing units (GPGPUs), as programmable accelerators, improve energy efficiency by integrating a large number of relatively small cores. In this paper, we focus on improving energy efficiency of such processing core by integrating an associative memory where function responses are prestored. Associative memories can search and recall function responses for a subset of input values therefore avoiding the actual function execution on the processing core that leads to energy saving. We propose a novel low-energy Resistive Multi-stage Associative Memory (ReMAM) architecture to significantly reduce energy of a search operation by employing selective row activation and in-advance precharging techniques. ReMAM splits the search operations in a ternary content addressable memory (TCAM) to a number of shorter searches in consecutive stages. Then, it selectively activates TCAM rows at each stage based on the hits of previous stages, thus enabling energy savings. The proposed in-advance precharging technique mitigates the delay of the sequential TCAM search and limits the number of precharges to two low-cost steps. ReMAM further implements approximation on the selective TCAM blocks to reduce the search energy that relaxes the function output in a fine-grained granularity with very low impact on accuracy of the results. Its multi-stage search operation makes ReMAM applicable to many applications such as search engines, sorting, image coding, pattern recognition, query processing, and machine learning. In this work, we show an application of proposed ReMAM on AMD Southern Island GPUs. Our experimental evaluation shows that ReMAM reduces on average GPGPU energy consumption by 35 percent in the exact mode, and 58 percent in approximate mode with average relative error lower than 10 percent. These energy savings are 1.8 $\times$ and 1.5 $\times$ higher than state-of-the-art associative memories used in GPGPUs in exact and approximate modes.

Exact modes for post-buckling characteristics of nonlocal nanobeams in a longitudinal magnetic field

• Exact mode solution is utilized to analyze postbuckling dynamics of the nanobeam in a longitudinal magnetic field. • The introduced magnetic field can increase the critical buckling load to enhance the stability of the nanobeam. • The nonlocal impact results in a decrease in the critical buckling load. • The nonlocal effect can speed up the activation of the internal resonance between the first two modes. • A significant difference is obtained for the first frequency when considering classical and exact mode solutions. An exact mode solution that investigates the prebuckling and postbuckling characteristics of nonlocal nanobeams with fixed–fixed, hinged–hinged, and fixed–hinged boundary conditions in a longitudinal magnetic field is determined. The geometric nonlinearity arising from mid-plane stretching is considered to obtain the nonlinear governing equation of motion by virtue of Hamilton's principle. The influences of the nonlocal and magnetic parameters on the prebuckling and postbuckling dynamics of nanobeams with various boundary conditions are evaluated, indicating that the critical buckling force can be decreased with the increase of the nonlocal parameter while can be increased with increasing the magnetic parameter. It is demonstrated that the first natural frequency of the nanobeam with fixed–fixed and fixed–hinged conditions in postbuckling configuration is increased from zero to a constant value for higher values of the nonlocal parameter with increasing the axial force. The second natural frequency of the buckled nanobeam is always decreased with an increase of the nonlocal parameter. The results show that the internal resonance between the first and second modes of the postbuckling nanobeams can be quickly and easily activated by increasing the nonlocal parameters, especially for fixed–fixed and hinged–hinged boundary conditions. In addition, the results obtained by exact mode solution are compared those obtained by classical mode solution. It is found that the classical mode is valid only for nonlocal nanobeams with the hinged–hinged boundary conditions.

Flexural vibrations of discontinuous layered elastically bonded beams

Abstract This paper addresses the dynamic flexural behavior of layered elastically bonded beams carrying an arbitrary number of elastic translational supports and rotational joints. The beams are referred to as discontinuous for the discontinuities of response variables at the application points of supports/joints. The Euler-Bernoulli hypothesis is assumed to hold for each layer separately, and a linear constitutive relation between the horizontal interlayer slip and the interlaminar shear force is considered. Based on the theory of generalized functions to handle the discontinuities of response variables due to supports/joints, exact beam modes are obtained from a characteristic equation built as determinant of a 6 × 6 matrix, regardless of the number of supports/joints. On using pertinent orthogonality condition for the deflection modes, the dynamic response of the beam is derived in time domain. Remarkably, all response variables are presented in a closed analytical form. Two numerical applications illustrate the efficiency of the proposed method.

Exact vibration modes of multiple-stepped beams with arbitrary steps and supports using elemental impedance method

A novel numerical method has been developed and applied to the prediction of vibration modes of general stepped beams with arbitrary steps and general elastic supports. Each beam section is modelled as an element with input impedance at one end and output impedance at the other. These impedances are then coupled when the beam sections are joined to form an overall stepped beam structure. General elastic supports are modelled and their effects on impedance are examined. The method is theoretically exact assuming each beam section can be modelled as Euler-Bernoulli beam and is computationally very efficient since it does not involve any matrix operations of large dimension. Vibration modes of a number of stepped beams of different configurations have been computed using the proposed method and are compared with existing results in literature. Experimental investigations have also been carried out to validate the practical usefulness of the method. The method is also ideally suited for forced vibration applications since it not only establishes vibration modes, but also frequency response functions. In addition, a general purpose software has since been developed based on the method which can be very useful for structural dynamics design of general stepped beam structures.

Exact matrix product decay modes of a boundary driven cellular automaton

We study integrability properties of a reversible deterministic cellular automaton (Rule 54 of (Bobenko et al 1993 Commun. Math. Phys. 158 127)) and present a bulk algebraic relation and its inhomogeneous extension which allow for an explicit construction of Liouvillian decay modes for two distinct families of stochastic boundary driving. The spectrum of the many-body stochastic matrix defining the time propagation is found to separate into sets, which we call orbitals, and the eigenvalues in each orbital are found to obey a distinct set of Bethe-like equations. We construct the decay modes in the first orbital (containing the leading decay mode) in terms of an exact inhomogeneous matrix product ansatz, study the thermodynamic properties of the spectrum and the scaling of its gap, and provide a conjecture for the Bethe-like equations for all the orbitals and their degeneracy.

Exact zero modes in frustrated Haldane chains

We show that the effective coupling between the spin-1/2 edge states of a spin-1 chain of finite length can be continuously tuned by frustration. For the $J_1-J_2$ model with nearest and next-nearest neighbor antiferromagnetic interactions, we show that the effective coupling in a chain of length $L$ changes sign $N\simeq 0.38 L$ times in the window $0.28\lesssim J_2/J_1 \lesssim 0.75$ where the short-range correlations are incommensurate. This implies that there are $N$ zero modes where the singlet and the triplet are strictly degenerate, i.e. $N$ values of $J_2/J_1$ where the spin-1/2 edge states are completely decoupled. We argue that this effect must be generic for all incommensurate phases with localized edge states, and we briefly discuss a few experimental implications.

Exact zero modes in twisted Kitaev chains

We study the Kitaev chain under generalized twisted boundary conditions, for which both the amplitudes and the phases of the boundary couplings can be tuned at will. We explicitly show the presence of exact zero modes for large chains belonging to the topological phase in the most general case, in spite of the absence of "edges" in the system. For specific values of the phase parameters, we rigorously obtain the condition for the presence of the exact zero modes in finite chains, and show that the zero modes obtained are indeed localized. The full spectrum of the twisted chains with zero chemical potential is analytically presented. Finally, we demonstrate the persistence of zero modes (level crossing) even in the presence of disorder or interactions.

Universal distribution of would-be topological zero modes in coupled chiral systems

We consider two quenched, chiral ensembles which are coupled in such a way that a combined chiral symmetry is preserved. The coupling also links the topology of the two systems such that the number of exact zero modes in the coupled system equals the sum of the number of zero modes in the two uncoupled systems counted with sign. The canceled modes that turn non-topological due to the coupling become near-zero modes at small coupling. We analyze the distribution of these would-be zero modes using effective field theory. The distribution is universal and, in the limit of small coupling, the would-be zero modes are distributed according to a finite size chiral Gaussian ensemble, where the width of the distribution scales as the inverse square root of the volume.

Exact eigensolution of a class of multi-level elastically connected members

Attention is given to determining the exact natural frequencies and modes of vibration of a class of structures comprising any number of related parallel members that are connected to each other, and possibly also to foundations, by uniformly distributed elastic interfaces of unequal stiffness. The members themselves are considered to have a uniform distribution of mass and stiffness and account can be taken of additional point masses and spring supports. The formulation is general and applies to any structure in which the motion of the component members is governed by a second order Sturm-Liouville equation. Closed form solution of the governing differential equations leads either, to a series of exact substitute systems that are easy to solve through a stiffness approach and which together yield the complete spectrum of natural frequencies and corresponding mode shapes of the original structure, or to simple exact relationships between the natural frequencies corresponding to coupled and uncoupled motion that enable hand solution of the more standard problems to be achieved. An appropriate form of the Wittrick-Williams algorithm is presented for converging on the required natural frequencies to any desired accuracy with the certain knowledge that none have been missed. Examples are given to confirm the accuracy of the approach and to indicate its range of application.

Static and Dynamic Behavior of Fibrous Polymeric Composite Materials at Different Environmental Conditions

The study of static and dynamic behavior of environmentally conditioned fibre reinforced polymeric (FRP) composites is necessary and crucial to examine the durability, reliability and sustainability of these noble materials. FRP composites are being used all around the globe and substituting the conventional materials, starting from mini toys to large aerospace components. Present review has introduced to accumulate and understand the disseminate literature in concentrating the significance of understanding the static and dynamic behavior of FRPs with changing environmental conditionings (hygrothermal, low and high temperature, salt solution, freeze thaw, UV light) and with the interaction of different nano-fillers. Their stability and integrity in diverse service environments may be reformed by their reactions against different nature of loadings i.e. static or dynamic and the components such as fibre, matrix and fibre/matrix interfaces in those environments. The static and dynamic states of loading may come with a possible weaker region to encounter the durability and integrity of the composites. To understand the exact failure modes that correlates the position of environmentally conditioned interfaces and dynamic state of loadings, thus confusing the estimation of its overall performance and mechanical behavior. Interface reliability and durability is vital since in-service environments the degradation in the interfacial region leads to complete composite failure. Therefore, the study of combined effects of various in-service environmental conditions and the role of static and dynamic behavior on the interface will be a crucial part related to the multiaxial dynamic states of failures occurring in FRP’s.