Energy Level Spectrum Research Articles

Spectral phenotyping of embryonic development reveals integrative thermodynamic responses

BackgroundEnergy proxy traits (EPTs) are a novel approach to high dimensional organismal phenotyping that quantify the spectrum of energy levels within different temporal frequencies associated with mean pixel value fluctuations from video. They offer significant potential in addressing the phenotyping bottleneck in biology and are effective at identifying lethal endpoints and measuring specific functional traits, but the extent to which they might contribute additional understanding of the phenotype remains unknown. Consequently, here we test the biological significance of EPTs and their responses relative to fundamental thermodynamic principles. We achieve this using the entire embryonic development of Radix balthica, a freshwater pond snail, at different temperatures (20, 25 & 30 °C) and comparing responses against predictions from Arrhenius’ equation (Q10 = 2).ResultsWe find that EPTs are thermally sensitive and their spectra of frequency response enable effective high-dimensional treatment clustering throughout organismal development. Temperature-specific deviation in EPTs from thermodynamic predictions were evident and indicative of physiological mitigation, although they differed markedly in their responses from manual measures. The EPT spectrum was effective in capturing aspects of the phenotype predictive of biological outcomes, and suggest that EPTs themselves may reflect levels of energy turnover.ConclusionsWhole-organismal biology is incredibly complex, and this contributes to the challenge of developing universal phenotyping approaches. Here, we demonstrate the biological relevance of a new holistic approach to phenotyping that is not constrained by preconceived notions of biological importance. Furthermore, we find that EPTs are an effective approach to measuring even the most dynamic life history stages.

Maximal relevance and optimal learning machines

We explore the hypothesis that learning machines extract representations of maximal relevance, where the relevance is defined as the entropy of the energy distribution of the internal representation. We show that the mutual information between the internal representation of a learning machine and the features that it extracts from the data is bounded from below by the relevance. This motivates our study of models with maximal relevance—that we call optimal learning machines—as candidates of maximally informative representations. We analyse how the maximisation of the relevance is constrained both by the architecture of the model used and by the available data, in practical cases. We find that sub-extensive features that do not affect the thermodynamics of the model, may affect significantly learning performance, and that criticality enhances learning performance, but the existence of a critical point is not a necessary condition. On specific learning tasks, we find that (i) the maximal values of the likelihood are achieved by models with maximal relevance, (ii) internal representations approach the maximal relevance that can be achieved in a finite dataset and (iii) learning is associated with a broadening of the spectrum of energy levels of the internal representation, in agreement with the maximum relevance hypothesis.

Two-nucleon S -wave interactions at the SU(3) flavor-symmetric point with mud≈msphys : A first lattice QCD calculation with the stochastic Laplacian Heaviside method

We report on the first application of the stochastic Laplacian Heaviside method for computing multi-particle interactions with lattice QCD to the two-nucleon system. Like the Laplacian Heaviside method, this method allows for the construction of interpolating operators which can be used to construct a positive definite set of two-nucleon correlation functions, unlike nearly all other applications of lattice QCD to two nucleons in the literature. It also allows for a variational analysis in which optimal linear combinations of the interpolating operators are formed that couple predominantly to the eigenstates of the system. Utilizing such methods has become of paramount importance in order to help resolve the discrepancy in the literature on whether two nucleons in either isospin channel form a bound state at pion masses heavier than physical, with the discrepancy persisting even in the $SU(3)$-flavor symmetric point with all quark masses near the physical strange quark mass. This is the first in a series of papers aimed at resolving this discrepancy. In the present work, we employ the stochastic Laplacian Heaviside method without a hexaquark operator in the basis at a lattice spacing of $a\sim0.086$~fm, lattice volume of $L=48a\simeq4.1$~fm and pion mass $m_\pi\simeq714$ MeV. With this setup, the observed spectrum of two-nucleon energy levels strongly disfavors the presence of a bound state in either the deuteron or dineutron channel.

Tunable conductance and spin filtering in twisted bilayer copper phthalocyanine molecular devices.

We investigate theoretically the quantum transport properties of a twisted bilayer copper phthalocyanine (CuPc) molecular device, in which the bottom-layer CuPc molecule is connected to V-shaped zigzag-edged graphene nanoribbon electrodes. Based on a non-equilibrium Green's function approach in combination with density-functional theory, we find that the twist angle effectively modulates the electron interaction between the bilayer CuPc molecules. HOMO (highest occupied molecular orbital)–LUMO (lowest unoccupied molecular orbital) gap, spin filtering efficiency (SFE) and spin-dependent conductance of the bilayer CuPc molecular device could be modulated by changing the twist angle. The conductance reaches its maximum when the twist angle θ is 0° while the largest SFE is achieved when θ = 60°. The twist angle-induced exotic transport phenomena can be well explained by analyzing the transmission spectra, molecular energy level spectra and scattering states of the twisted bilayer CuPc molecular device. The tunable conductance, HOMO–LUMO gap and spin filtering versus twist angle are helpful for predicting how a two-molecule system may behave with twist angle.

An undergraduate-oriented comment about inverting spectral data to determine the interatomic potential

An elementary, analytically soluble example of a pair of isospectral potentials is discussed. This example was developed in response to an inquiry by an undergraduate student who was intrigued by the widely used (but not often discussed in undergraduate courses) Rydberg–Klein–Rees (RKR) procedure for inverting rovibrational data to determine potential functions of diatomic molecules, which is based on the semiclassical (WKB) approximation. The pair of potentials discussed provide a clear elementary example of the insufficiency of the energy level spectrum to determine the potential, even in a case in which the bound states form a complete set.

Linearized spectral decimation in fractals

In this article we study the energy level spectrum of fractals which have block-hierarchical structures. We develop a method to study the spectral properties in terms of linearization of spectral decimation procedure and verify it numerically. Our approach provides qualitative explanations for various spectral properties of self-similar graphs within the theory of dynamical systems, including power-law level-spacing distribution, smooth density of states and effective chaotic regime.

Analysis and Research on Microseismic Signal Characteristics and Energy Change of Working Face in Liyazhuang Mine

To provide a certain support for the prediction of the rockburst and setting of the threshold, the SOS microseismic monitoring system is used to remotely, real-time, dynamic and automatic monitoring of the seismic signal of the 2-228 working face of Liyazhuang coal mine. And the original signal of the microseismic is processed by the window Fourier transform, and the characteristics of the microseismic waveform and spectrum of different energy levels are analyzed. The results show that there are different characteristics of waveform and spectrum corresponding to signals at different energy levels. The high amplitude, low and centralized main frequency, long duration of signal, coda waves developing obviously than head wave and slow attenuation are the typical characteristics of strong mine earthquake. With the decrease of mine earthquake energy, the vibration attenuation rate gradually becomes faster, and the duration of the signal being shorter, the development of the head wave being obvious, the amplitude of velocity decreasing correspondingly, but the rate of amplitude decreasing gradually slows down, and the main frequency is gradually spread from concentration to diffusion, while the frequency distribution range is affected rarely. The research results can provide a scientific basis for setting the threshold of shock pressure prediction index and its risk prediction.

Study on the Properties of Organic–Inorganic Hole Transport Materials in Perovskite Based on First-Principles

Newport Inc. was licensed recently by the National Renewable Energy Laboratory of the United States to update the highest efficiency of the perovskite solar cell (PSC) certification of PSCs by 23.7%. Exploring new hole transfer layer is the key to the future development of PSC. In this paper, we constructed seven organic hole transport material molecules such as copper-phthalocyanine (CuPc), 2',7'-bis(bis(4-methoxyphenyl)amino)spiro[cyclopenta-[2,1-b:3,4-b']dithiophene-4,9'-fluorene] (FDT), Poly-triarylamine (PTAA), poly(3,4-ethylenedioxy thiophene)/poly(styrenesulfonate) (PEDOT/PSS) poly(3-hexylthiophene) (P3HT) and six in-organic hole transport material molecules such as CuCSN, CuI, InCuS2, CuO, Cu2O, NiO with Material Studio software. By the structure optimization, their energy band, density of state (DOS), HOMO/lowest unoccupied orbit (LUMO) energy level and absorption spectrum were calculated. Furthermore, the HOMO/LUMO electron cloud distribution map of FDT molecule was analyzed in detail. The results show that the electron cloud is closer to the nucleus with the increase of the isopotential surface value. From the absorption spectra, the absorption wavelengths of most inorganic hole transport materials are mainly concentrated at about 200 nm, which is relatively short. But the absorption wavelengths of organic hole transport materials are distributed in long wavelength region, most of them are above 2000 nm. Only the absorption spectra of PTAA, Spiro OMetad and CuPc are in the range of solar spectrum. The HOMO energy levels of seven organic hole transport materials are slightly higher than the values of valence band of CH3NH3PbI3 and NH2CH = NH2PbI3, which are favorable for carrier injection and transport. The band gap of inorganic hole transport materials CuCSN and CuI is wider. From the energy band structure curve, the effective mass of NiO, CuO, Cu2O carriers is smaller, which the carrier transport rate is relatively high. The hole transport material must have high hole mobility and hole conductivity so as to ensure the effective transport of the hole at the interface between the hole transport layer and the perovskite layer.

Time-crystalline behavior in an engineered spin chain

Time crystals appear when systems display a commensurate spontaneous breaking of the discrete time translational invariance imposed by an external periodic drive. No consensus on the definition has been reached as yet, but important aspects comprise robustness against small variations of the parameters and the initial quantum state. Often, disorder and interaction are thought to be essential ingredients for the occurrence of time crystals. We study a finite-length polarized XX spin chain engineered to display a spectrum of equidistant energy levels without drive and show that it keeps a spectrum of equidistant quasienergies in Floquet theory for a large variety of periodic driving schemes. This interesting behavior is explained by mapping the XX spin chain with $N+1$ sites to a single large spin with $S=N/2$ invoking the closure of the group SU(2). For suitably tuned parameters this system realizes time crystals of various periodicities for \emph{all} initial states. The robustness against variations of the parameters is also discussed. Thereby, we establish a clean system without interaction which can display the phenomenon of time crystallization.

Multifractal spectrum and spectral behavior of calcium and titanium isotopes based on nuclear shell model

We investigate the effect of valence space nucleons on the multifractal analysis (MFA) and spectral analysis of calcium and titanium isotopes. The multifractality of wavefunctions is characterized by its associated singularity spectrum f(α) and generalized dimension Dq. The random matrix theory (RMT) has been employed in the study of properties of the distribution of energy levels. In particular, we find that the number of nucleons and two-body residual interactions particularly affect the singularity and energy level spectra.

Local orbital degeneracy lifting as a precursor to an orbital-selective Peierls transition

Fundamental electronic principles underlying all transition metal compounds are the symmetry and filling of the d-electron orbitals and the influence of this filling on structural configurations and responses. Here we use a sensitive local structural technique, x-ray atomic pair distribution function analysis, to reveal the presence of fluctuating local-structural distortions at high temperature in one such compound, CuIr2S4. We show that this hitherto overlooked fluctuating symmetry-lowering is electronic in origin and will modify the energy-level spectrum and electronic and magnetic properties. The explanation is a local, fluctuating, orbital-degeneracy-lifted state. The natural extension of our result would be that this phenomenon is likely to be widespread amongst diverse classes of partially filled nominally degenerate d-electron systems, with potentially broad implications for our understanding of their properties.

Influence of plasma shielding effect on ground state and excited state energies of Ar<sup>16+</sup>

A systematical knowledge of the atomic properties in plasma is of great interest for various research areas, such as the explanation of the X-ray radiation from universe, plasma diagnostics, extreme ultraviolet (EUV) and X-ray sources and so on. Among these researches, the detailed information about how the plasma influences the atomic energy level and transition spectrum are crucial for understanding the X-ray emission mechanism and the state of plasma. An analytic calculation method of treating the non-relativistic energy and its relativistic corrections for the multi-electron atoms embedded in weakly coupled plasma is developed based on the Rayleigh-Ritz variation method. The systematical investigations are performed for the ground state 1s<sup>2</sup> <sup>1</sup>S, single excited states 1sns <sup>1,2</sup>S (<i>n</i> = 2−5), 1s<i>n</i>p <sup>1,3</sup>P (<i>n</i> = 2−5) and double excited state 2s2p <sup>1</sup>P of Ar<sup>16+</sup> ion in weak coupled plasma. The analytic formulas for calculating the non-relativistic energy and its relativistic correction energy are derived, which include mass correction, one and two-body Darwin correction, spin-spin contact interaction and orbit-orbit interaction. All the angular integration spin sums involved in the problem are worked out explicitly by using the irreducible theory. The influence of plasma on non-relativistic energy and relativistic correction energy are discussed. The results show that the mass correction and the one-body Darwin correction are the main ones among the terms of relativistic correction, and are three orders of magnitude greater than the other relativistic terms. The plasma shielding effect mainly affects the non-relativistic energy, and has little effect on the relativistic correction. At the same time, it has a more significant selectivity for the electronic configuration. Further research shows that the influence of plasma on the energy of the outer shell electron is greater than that of the inner shell electron. With the increase of the plasma shielding parameters, the outer shell electron extends outward, and the higher the excited state, the greater the degree of extension is. This work should be useful for astrophysical applications where such a plasma environment exists.

Benzobis(thiadiazole)-based small molecules as efficient electron transporting materials in perovskite solar cells

Novel small-molecules, B2T and B2F, based on benzobis(thiadiazole) have been designed and synthesized as electron transporting materials for perovskite solar cells (PSCs). Benefiting from the high electron affinity of benzobis(thiadiazole) unit, both B2T and B2F exhibited an efficient electron transporting ability in CH3NH3PbI3-xClx planar-heterojunction (PHJ) PSCs. The device based on B2T exhibited an optimal power-conversion efficiency (PCE) of 13.0%, while that of B2F was 15.0% with a relatively low hysteresis. Compared to B2T device, the higher efficiency of B2F device was mainly due to the impressive increase in short-circuit current density (JSC), from 19.36 mA cm−2 to 22.13 mA cm−2. By comprehensive analysis of the energy level and photoluminescence spectra of the devices, we inferred that the higher JSC was resulted from the lower highest occupied molecular orbital (HOMO) energy level of B2F than B2T, which induced a more efficient hole-blocking and less recombination of charge carriers. Through the molecular design (from thiophene to fluorene), we developed a highly efficient electron transporting material, this strategy may provide a new building block to develop novel efficient interface materials for PSCs.

Addition energy and magnetization of 3-D multicarrier anisotropic quantum dots in magnetic field by exact multi-pole expansion of coulomb correlations

Coulomb interactions replicates in N(N − 1)∕2 terms for interacting 3-D N − e confined quantum dots leading to non-trivial Schrödinger equations. For the systems having N > 3, e − e interaction reciprocating to both lateral (electrical) and transverse (magnetic) confinements in moderate fields causes acute interplay in anisotropic quantum dots. As DFT, Hartree-Fock and other perturbative methods have certain limitations, recasting Schrödinger equations into self-adjoint Whittaker-M functions addresses coulomb (exchange) integrals as simplest, finite and single-summed analytical Lauricella functions (F2) via Chu-Vandermonde identity. In case of higher ′N′, expansion of coulomb correlations in terms of multi-pole expansion facilitates the convergences for bound states upto quadrapole and octopole terms. Although, fermionic exchange symmetry of many electron systems could be included in terms of various two-electron integrals, for the sake of brevity we have aimed to reproduce experimental results without spin. Level clustering/accidential degeneracies manifest on energy level spectra due to competitive role among anisotropic confinement strength, magnetic field, mass of the carrier and dielectric constant of the medium. It triggers orbital induced paramagnetism (T ∼ (0 − 1)K), signature of fractional quantum Hall effect (FQHE) in chemical potential cusps (μ) and formation of different ′shell structures′ in capacitive energy respectively, spanning over wide dielectric range of materials (atomic like quantum dots, ZnO, GaAs and PbSe (Lead Chalcogenide) etc).

Qualitative models of intramolecular dynamics of acetylene: relation between the bending polyads of acetylene and perturbed Keplerian systems

ABSTRACTWe analyse qualitatively the bending vibrational polyads of the acetylene molecule (CH) in the approximation of the resonant oscillator with axial symmetry using an effective vibrational Hamiltonian which reproduces bending vibrational energy levels computed by Michel Herman and coworkers [M. Herman, A. Campargue, M.I.E. Idrissi, and J.V. Auwera, J. Phys. Chem. Ref. Data 32 (3), 921 (2003). doi: 10.1063/1.1531651]. We explain how the classical limit of this quantum system for the total vibrational angular momentum is equivalent to a reduced perturbed Keplerian system on the classical phase space , such as the hydrogen atom in external electric and magnetic fields in the Kustaanheimo–Stiefel formalism. In particular, bending vibrational -polyads of CH correspond to the n-shells of the perturbed hydrogen atom. Within this approach, using the techniques developed for the Keplerian systems and methods of the qualitative theory, we account concisely for all series of bifurcations of the classical nonlinear normal modes and their manifestations in the quantum energy level spectrum described by our predecessors [V. Tyng and M.E. Kellman, J. Phys. Chem. B 110 (38), 18859 (2006). doi: 10.1021/jp057357f]. In addition to local oscillator approximations near stable equilibrium points, notably the local modes discussed by Rose and Kellman [J. Chem. Phys. 105 (24), 10743 (1996). doi: 10.1063/1.472882] and Jacobson et al. [J. Chem. Phys. 109 (1), 121 (1998). doi: 10.1063/1.476529; J. Chem. Phys. 111, 600 (1999). doi: 10.1063/1.479341; J. Chem. Phys. 110, 845 (1999). doi: 10.1063/1.478052], we introduce two new global integrable approximations, and confirm them by constructing respective two regular complementary lattices of quantum states within one -polyad. From the stratification of the phase space, we uncover the geometrical meaning of the corresponding new good quantum numbers and define new kind of wavefunction localisation in the neighbourhood of two spheres in the four-dimensional space. Furthermore, we use our two approximate lattices to uncover quantum monodromy of the system through the evolution of an elementary quantum cell along a closed path in the images of the nearly integrable energy-momentum maps.

Mapping the Coulomb Environment in Interference-Quenched Ballistic Nanowires.

The conductance of semiconductor nanowires is strongly dependent on their electrostatic history because of the overwhelming influence of charged surface and interface states on electron confinement and scattering. We show that InAs nanowire field-effect transistor devices can be conditioned to suppress resonances that obscure quantized conduction thereby revealing as many as six sub-bands in the conductance spectra as the Fermi-level is swept across the sub-band energies. The energy level spectra extracted from conductance, coupled with detailed modeling shows the significance of the interface state charge distribution revealing the Coulomb landscape of the nanowire device. Inclusion of self-consistent Coulomb potentials, the measured geometrical shape of the nanowire, the gate geometry and nonparabolicity of the conduction band provide a quantitative and accurate description of the confinement potential and resulting energy level structure. Surfaces of the nanowire terminated by HfO2 are shown to have their interface donor density reduced by a factor of 30 signifying the passivating role played by HfO2.

Evaluation of the Impact of Transient Disturbances on Railway Signaling Systems Using an Adapted Time-Frequency Analysis Method

Abstract As many other industrial environments, the railway electromagnetic environment is characterized by a large number of electromagnetic signals and disturbances. Among these, transient signals, with high energy level and wide frequency spectrum, represent an important threat to different signaling subsystems. In this paper, a new methodology dedicated to the detection and the characterization of the transient disturbances is presented. Based on a flexible and adjustable time-frequency analysis, this methodology is used to evaluate the impact of transient disturbances on a ground-to-train radio communication. A test bench was developed in order to validate the results of this evaluation.

Coherent Features of Resonance-Mediated Two-Photon Absorption Enhancement by Varying the Energy Level Structure, Laser Spectrum Bandwidth and Central Frequency**Supported by the National Natural Science Foundation of China under Grant Nos 51132004, 11474096 and 11604199, the Science and Technology Commission of Shanghai Municipality under Grant No 14JC1401500, and the Higher Education Key Program of He’nan Province under Grant Nos 17A140025 and

The femtosecond pulse shaping technique has been shown to be an effective method to control the multi-photon absorption by the light–matter interaction. Previous studies mainly focused on the quantum coherent control of the multi-photon absorption by the phase, amplitude and polarization modulation, but the coherent features of the multi-photon absorption depending on the energy level structure, the laser spectrum bandwidth and laser central frequency still lack in-depth systematic research. In this work, we further explore the coherent features of the resonance-mediated two-photon absorption in a rubidium atom by varying the energy level structure, spectrum bandwidth and central frequency of the femtosecond laser field. The theoretical results show that the change of the intermediate state detuning can effectively influence the enhancement of the near-resonant part, which further affects the transform-limited (TL)-normalized final state population maximum. Moreover, as the laser spectrum bandwidth increases, the TL-normalized final state population maximum can be effectively enhanced due to the increase of the enhancement in the near-resonant part, but the TL-normalized final state population maximum is constant by varying the laser central frequency. These studies can provide a clear physical picture for understanding the coherent features of the resonance-mediated two-photon absorption, and can also provide a theoretical guidance for the future applications.

Prediction of quantum many-body chaos in the protactinium atom

Energy level spectrum of protactinium atom (Pa, Z=91) is simulated with a CI calculation. Levels belonging to the separate manifolds of a given total angular momentum and parity $J^\pi$ exhibit distinct properties of many-body quantum chaos. Moreover, an extremely strong enhancement of small perturbations takes place. As an example, effective three-electron interaction is investigated and found to play a significant role in the system. Chaotic properties of the eigenstates allow one to develop a statistical theory and predict probabilities of different processes in chaotic systems.

Reversing the Landauer's erasure: Single‐electron Maxwell's demon operating at the limit of thermodynamic efficiency

AbstractAccording to Landauer's principle, erasure of information is the only part of a computation process that unavoidably involves energy dissipation. If done reversibly, such an erasure generates the minimal heat of per erased bit of information. The goal of this work is to discuss the actual reversal of the optimal erasure which can serve as the basis for the Maxwell's demon operating with ultimate thermodynamic efficiency as dictated by the second law of thermodynamics. The demon extracts of heat from an equilibrium reservoir at temperature T per one bit of information obtained about the measured system used by the demon. We have analyzed this Maxwell's demon in the situation when it uses a general quantum system with a discrete spectrum of energy levels as its working body. In the case of the effectively two‐level system, which has been realized experimentally based on tunneling of individual electron in a single‐electron box , we also studied and minimized corrections to the ideal reversible operation of the demon. These corrections include, in particular, the non‐adiabatic terms which are described by a version of the classical fluctuation–dissipation theorem. The overall reversibility of the Maxwell's demon requires, beside the reversibility of the intrinsic working body dynamics, the reversibility of the measurement, and feedback processes. The single‐electron demon can, in principle, be made fully reversible by developing a thermodynamically reversible single‐electron charge detector for measurements of the individual charge states of the single‐electron box.