Complex Envelope Research Articles

From Cool to Hot F-stars: The Influence of Two Ionization Regions in the Acoustic Oscillations

Abstract The high-precision data available from the Kepler satellite allows us to study the complex outer convective envelopes of solar-type stars. We use a seismic diagnostic, specialized for investigating the outer layers of solar-type stars, to infer the impact of the ionization processes on the oscillation spectrum, for a sample of Kepler stars. These stars, of spectral type F, cover all of the observational seismic domain of the acoustic oscillation spectrum in solar-type stars. They also cover the range between a cool F-dwarf (∼6000 K) and a hotter F-star (∼6400 K). Our study reveals the existence of two relevant ionization regions. One of these regions, which is located closer to the surface of the star, is commonly associated with the second ionization of helium, although other chemical species also contribute to ionization. The second region, located deeper in the envelope, is linked with the ionization of heavy elements. Specifically, in this study, we analyze the elements carbon, nitrogen, oxygen, neon, and iron. Both regions can be related to the K electronic shell. We show that, while for cooler stars like the Sun, the influence of this second region on the oscillation frequencies is small; in hotter stars, its influence becomes comparable to the influence of the region of the second ionization of helium. This can guide us in the study of the outer layers of F-stars, specifically with the understanding of phenomena related to rotation and magnetic activity in these stars.

The Flow of Proteins and Idealised Pores within the Membranes of Gram-Negative Bacteria

Gram-negative bacteria are protected by a complex cell envelope. Understanding the structure-dynamics-function relationships within the Gram-negative cell envelope is key to the ongoing fight against the emergence of bacterial resistance to antibiotics. The Gram–negative cell envelope consists of two membranes, separated by a cell wall. The membranes contain a variety of proteins, which make up to 25% of the bilayer surface area. Lipid-protein interactions are significant in determining the function and organisation of membrane proteins, through macroscopic bilayer properties or specific protein-lipid interactions. Computational and experimental studies have revealed that proteins and lipids diffuse together as complexes, which have dynamical properties that differ from the properties of unbound lipids. However it is unclear how much the size, shape and biochemistry of the macromolecules contribute to these altered dynamics. Here we present the results of coarse–grained simulations that uncover the structural and dynamic effects of a series of outer membrane proteins (OMPs) and functionlised carbon nanotubes (CNTs) on biologically relevant models of the inner and outer membranes of E. coli. Investigating such a range of nanopores provides an insight into the effects the chemistry and topology of an embedded protein have on the local membrane environment. We show that the flow of molecules in the outer membrane is asymmetrical, reflecting the lipid composition of this membrane. Flow of proteins and lipids are highly correlated in the outer leaflet and much less so in the inner leaflet of the membrane.

Motion-compensated coherent integration of constant moving target echoes with arbitrary complex envelope

Signal integration, as an effective method of detecting weak target, is widely used in areas of radar, sonar, etc. In previous studies of long-time coherent integration, researchers usually established a multi-pulse echo model with linear frequency modulation (LFM) signal due to its good compression performance and large Doppler tolerance. Then, perfect analytical formula can be deduced to compensate for range migration and Doppler spread, which is helpful in analyzing the mechanism of long-time coherent integration in depth. However, besides LFM, a wide variety of signal waveforms are also used in modern sonar and underwater guidance system to meet the requirements for diverse applications. For instance, continuous wave (CW) pulse is often used in signal detection, high resolution direction of arrival (DOA) estimation, and velocity estimation, while large time-bandwidth product waveforms such as modulated signal, coded signal, and pseudo-random signal are utilized for special tasks like anti-interference detection, channel matching, and active concealed detection. Therefore, the formulas and corresponding instructive conclusions deduced by LFM have no generality when other sonar waveforms are used in pulse integration. In this paper, we focus on long-time coherent integration for arbitrary signal reflected by underwater target moving with a uniform velocity and propose a motion-compensated coherent integration method for arbitrary complex envelop signal. A kind of general ambiguity function (GAF) for transmitted signal is defined to present a unified expression based on GAF for the output of the matched filter. The operation not only helps us to describe and calculate the pulse compression form of the arbitrary complex envelop by using a general mathematical model, but also provides information about the range migration and Doppler frequency shift of the multi-pulse echo, which is needed in pulse range alignment and FFT integration. For the matched filter output expressed by the GAF, Keystone transform is utilized to correct the complex envelop of the multi-pulse echo and eliminate the range walk. Then, Doppler frequency shift is compensated for by performing FFT transform, and the long-time coherent integration for arbitrary complex envelop is realized. To verify the correctness of the proposed method, we carry out the computer simulation on both signal integration and detection performance by using four sonar waveforms, i.e., CW signal, LFM signal, m-sequence phase-coded signal, and Costas frequency hop coded signal. The simulation results show that the proposed motion-compensated coherent integration method is applicable to arbitrary complex envelop signal. We also design an anechoic water tank experiment scheme which can successfully obtain the multi-pulse echoes of constant moving target. The motion-compensated coherent integration of the experimental data of the above-mentioned four waveforms further validates the effectiveness of the proposed method.

Structural Aspects of Betaherpesvirus-Encoded Proteins.

Betaherpesvirus possesses a large genome DNA with a lot of open reading frames, indicating abundance in the variety of viral protein factors. Because the complicated pathogenicity of herpesvirus reflects the combined functions of these factors, analyses of individual proteins are the fundamental steps to comprehensively understand about the viral life cycle and the pathogenicity. In this chapter, structural aspects of the betaherpesvirus-encoded proteins are introduced. Betaherpesvirus-encoded proteins of which structural information is available were summarized and subcategorized into capsid proteins, tegument proteins, nuclear egress complex proteins, envelope glycoproteins, enzymes, and immune-modulating factors. Structure of capsid proteins are analyzed in capsid by electron cryomicroscopy at quasi-atomic resolution. Structural information of teguments is limited, but a recent crystallographic analysis of an essential tegument protein of human herpesvirus 6B is introduced. As for the envelope glycoproteins, crystallographic analysis of glycoprotein gB has been done, revealing the fine-tuned structure and the distribution of its antigenic domains. gH/gL structure of betaherpesvirus is not available yet, but the overall shape and the spatial arrangement of the accessory proteins are analyzed by electron microscopy. Nuclear egress complex was analyzed from the structural perspective in 2015, with the structural analysis of cytomegalovirus UL50/UL53. The category "enzymes" includes the viral protease, DNA polymerase and terminase for which crystallographic analyses have been done. The immune-modulating factors are viral ligands or receptors for immune regulating factors of host immune cells, and their communications with host immune molecules are demonstrated in the aspect of molecular structure.

Identification of novel lipid modifications and intermembrane dynamics in Corynebacterium glutamicum using high-resolution mass spectrometry [S

The complex cell envelopes of Corynebacterineae contribute to the virulence of pathogenic species (such as Mycobacterium tuberculosis and Corynebacterium diphtheriae) and capacity of nonpathogenic species (such as Corynebacterium glutamicum) to grow in diverse niches. The Corynebacterineae cell envelope comprises an asymmetric outer membrane that overlays the arabinogalactan-peptidoglycan complex and the inner cell membrane. Dissection of the lipid composition of the inner and outer membrane fractions is important for understanding the biogenesis of this multilaminate wall structure. Here, we have undertaken the first high-resolution analysis of C. glutamicum inner and outer membrane lipids. We identified 28 lipid (sub)classes (>233 molecular species), including new subclasses of acylated/acetylated trehalose mono/dicorynomycolic acids, using high-resolution LC/MS/MS coupled with mass spectral library searches in MS-DIAL. All lipid subclasses exhibited polarized distributions across the inner and outer membrane fractions generated by differential solvent extraction. Strikingly, deletion of the TmaT protein, which is required for transport of trehalose corynomycolates across the inner membrane, led to the accumulation of triacylglycerols in the inner membrane and to suppressed synthesis of phosphatidylglycerol and alanylated lipids. These analyses indicate unanticipated connectivity in the synthesis and/or transport of different lipid classes in C. glutamicum.

Reliable Fault Diagnosis of Rotary Machine Bearings Using a Stacked Sparse Autoencoder‐Based Deep Neural Network

Due to enhanced safety, cost‐effectiveness, and reliability requirements, fault diagnosis of bearings using vibration acceleration signals has been a key area of research over the past several decades. Many fault diagnosis algorithms have been developed that can efficiently classify faults under constant speed conditions. However, the performances of these traditional algorithms deteriorate with fluctuations of the shaft speed. In the past couple of years, deep learning algorithms have not only improved the classification performance in various disciplines (e.g., in image processing and natural language processing), but also reduced the complexity of feature extraction and selection processes. In this study, using complex envelope spectra and stacked sparse autoencoder‐ (SSAE‐) based deep neural networks (DNNs), a fault diagnosis scheme is developed that can overcome fluctuations of the shaft speed. The complex envelope spectrum made the frequency components associated with each fault type vibrant, hence helping the autoencoders to learn the characteristic features from the given input signals more readily. Moreover, the implementation of SSAE‐DNN for bearing fault diagnosis has avoided the need of handcrafted features that are used in traditional fault diagnosis schemes. The experimental results demonstrate that the proposed scheme outperforms conventional fault diagnosis algorithms in terms of fault classification accuracy when tested with variable shaft speed data.

Characteristics of surface nuclear magnetic off-resonance signal and complex envelope inversion

As a new groundwater exploration method, noninvasive surface nuclear magnetic resonance (SNMR) has the benefits of direct, quantitative and uniqueness estimation of water content and relaxation time (T2*) in the near surface groundwater exploration. In practice, the earth magnetic field is difficult to be determined accurately, due to its inhomogeneity, time-varying and susceptible to ambient noise, which results in off-resonance excitation and serious decrease in accuracy of the inversion result. In this paper, based on the model of surface nuclear magnetic off-resonance (SNMOR) and the expression for the kernel function, the influences of the frequency offset on the amplitude and phase of the free induced decay (FID) signal are discussed, and a complex envelop inversion (CEI) based on automatic matching system phase and involving both the real part and imaginary part of the signal is applied. By comparing the synthetic signals generated from the SNMR and SNMOR models, it can be concluded that the phase of the FID signal significantly changes with the increase of the frequency offset, and the amplitude of the signal can be increased by 65.9% for the synthetic model in this paper. Thus when the frequency offset is greater than 2 Hz, the distribution of water content and T2* from the inversion results using the SNMR kernel will have a serious deviation from the actual model. However, using the SNMOR kernel based on the frequency offset, the inversion results are more accurate, and the maximum error of the water content and T2* are 4.2% and 39.3 ms, respectively. Moreover, synthetic data with different noise levels are inverted by the CEI method and conventional amplitude envelop inversion method (or QTI). The results show CEI obtain better performances in stability and reliability at a high noise level. Finally, a field measurement of SNMOR is conducted in Taipingchi Reservoir near Changchun City, China. The off-resonance FID signals are obviously observed by utilizing the JLMRS instrument and can be used to estimate the frequency offset. The characteristics of the FID signal with the frequency offset confirm the correctness of the SNMOR model. And the inversion result of field data using SNMOR kernel show that the distribution of water content and T2* are consistent with the known geological data from the drillings and other geophysical methods, which is much better than that using the SNMR kernel or conventional amplitude envelop inversion method. Therefore, the validities and accuracies of the SNMOR model and CEI method proposed in this paper are verified, which provides a new idea and technique for groundwater exploration in the near surface.

Combined optical solitary waves and conservation laws for nonlinear Chen–Lee–Liu equation in optical fibers

This paper obtains a combined optical solitary wave solution that is modeled by nonlinear Chen–Lee–Liu equation (NCLE) which arises in the context of temporal pulses along optical fibers associated with the self-steepening nonlinearity using the complex envelope function ansatz. The novel combined solitary wave describes bright and dark solitary wave properties in the same expression. The intensity and the nonlinear phase shift of the combined solitary wave solution are reported. Moreover, the Lie point symmetry generators or vector fields of a system of partial differential equations (PDEs) which is acquired by transforming the NCLE to a real and imaginary parts are derived. It is observed that the obtained system is nonlinearly self-adjoint with an explicit form of a differential substitution satisfying the nonlinear self-adjoint condition. Then we use these facts to establish a set of conservation laws (Cls) for the system using the general Cls theorem. Numerical simulation and physical interpretations of the obtained results are demonstrated with interesting figures showing the meaning of the acquired results. It is hoped that the results reported in this paper can enrich the nonlinear dynamical behaviors of the NCLE.

Novel optical solitary waves and modulation instability analysis for the coupled nonlinear Schrödinger equation in monomode step-index optical fibers

This paper addresses the coupled nonlinear Schrödinger equation (CNLSE) in monomode step-index in optical fibers which describes the nonlinear modulations of two monochromatic waves, whose group velocities are almost equal. A class of dark, bright, dark-bright and dark-singular optical solitary wave solutions of the model are constructed using the complex envelope function ansatz. Singular solitary waves are also retrieved as bye products of the in integration scheme. This naturally lead to some constraint conditions placed on the solitary wave parameters which must hold for the solitary waves to exist. The modulation instability (MI) analysis of the model is studied based on the standard linear-stability analysis. Numerical simulation and physical interpretations of the obtained results are demonstrated. It is hoped that the results reported in this paper can enrich the nonlinear dynamical behaviors of the CNLSE.

Exact quantification by the nonparametric fast Pad\xe9 transform using only shape estimation of high-order derivatives of envelopes

This study deals exclusively with total shape spectra (envelopes). Yet, the goal is to exactly reconstruct all the components of the given envelope by relying only upon non-parametric signal processors (shape estimators). To this end, the so-called derivative envelope spectra are investigated. A derivative spectrum is the result of the application of the differentiation transform left( {hbox {d}/hbox {d}nu } right) ^{m} to the given conventional spectrum. Here, non-negative integer m is the order of differentiation and nu is the real linear sweep frequency. For the customary envelope (the hbox {zero}{mathrm{th}}-order derivative, m=0), we use the non-parametric fast Padé transform to generate the derivative fast Padé transform (dFPT). Explicit computations are carried out by successively increasing the differentiation order m from low through intermediate to high values of derivatives of complex envelopes. The dFPT can disentangle the spectrally crowded regions by splitting apart any multiplet of closely packed peaks. Hidden resonances, even those that are very weak, can be not only visualized, but also exactly quantified by the dFPT, despite performing shape estimations alone. Most importantly, while the envelopes in the derivative fast Fourier transform exhibit huge noise amplification with increasing m, the same-order of the differentiation transform in the dFPT acts as an effective noise suppressor. The results of the dFPT are illustrated for the envelopes with overlapping peaks stemming from synthesized noise-free and noise-contaminated time signals associated with encoding by in vitro proton magnetic resonance spectroscopy (MRS) of breast cancer tissue. This new methodology is anticipated to significantly enhance resolution as well as signal-to-noise ratio and the overall performance of single-voxel MRS in clinical diagnostics. It is also expected to be of special benefit for volumetric coverage of the scanned tissue by magnetic resonance spectroscopic imaging.

Dark and combined optical solitons, and modulation instability analysis in dispersive metamaterial

This paper obtains the dark and dark-bright or combined optical solitons to the nonlinear schrödinger equation (NLSE) describing propagation in dispersive metamaterial in optical fibers. The integration algorithm is the complex envelope function ansatz. This naturally lead to some constraint conditions placed on the soliton parameters which must hold for the solitons to exist. The intensities and the nonlinear phase shifts of the solitons are reported. Furthermore, the modulation instability analysis (MI) is studied based on the standard linear-stability analysis and the MI gain spectrum is got. Numerical simulation of some obtained results are analyzed with interesting figures showing the physical meaning of the solutions.

Spectral photonic lattices with complex long-range coupling

We suggest and experimentally realize a spectral photonic lattice - a signal can hop between discrete frequency channels, driven by nonlinear interaction with stronger pump lasers. By controlling the complex envelope and frequency separations of multiple pumps, it is possible to introduce non- local hopping and to break time-reversal symmetry, which opens up new possibilities for photonic quantum simulation. As two examples, we observe a spectral quantum walk and demonstrate the discrete Talbot effect in the spectral domain, where we find novel instances containing asymmetry and periodicities not possible in spatial lattices.

Chirped singular solitons for Chen-Lee-Liu equation in optical fibers and PCF

This paper obtains chirped singular optical soliton solutions that is modeled by Chen-Lee-Liu equation in the context of optical fibers and PCF. A special complex envelope traveling-wave method is applied to find a nonlinear equation with a fifth-degree nonlinear term describing the dynamics of field amplitude in the nonlinear media. It is shown that the chirp associated to the obtained solutions is directly proportional to the intensity of the wave and its amplitude is controlled by self steepening term. Parametric conditions for the existence of the chirped singular structures are also presented.

A Turbulent Origin for the Complex Envelope Kinematics in the Young Low-mass Core Per-bolo 58

Abstract We use CARMA 3 mm continuum and molecular lines (NH2D, N2H+, HCO+, HCN, and CS) at ∼1000 au resolution to characterize the structure and kinematics of the envelope surrounding the deeply embedded first core candidate Per-bolo 58. The line profile of the observed species shows two distinct peaks separated by 0.4–0.6 km s−1, which most likely arise from two different optically thin velocity components rather than the product of self-absorption in an optically thick line. The two velocity components, each with a mass of ∼0.5–0.6 , overlap spatially at the position of the continuum emission and produce a general gradient along the outflow direction. We investigate whether these observations are consistent with infall in a turbulent and magnetized envelope. We compare the morphology and spectra of the N2H+ (1–0) with synthetic observations of an MHD simulation that considers the collapse of an isolated core that is initially perturbed with a turbulent field. The proposed model matches the data in the production of two velocity components, traced by the isolated hyperfine line of the N2H+ (1–0) spectra, and shows a general agreement in morphology and velocity field. We also use large maps of the region to compare the kinematics of the core with that of the surrounding large-scale filamentary structure and find that accretion from the large-scale filament could also explain the complex kinematics exhibited by this young dense core.

Optical solitons and modulation instability analysis of an integrable model of (2+1)-Dimensional Heisenberg ferromagnetic spin chain equation

This paper addresses the nonlinear Schrödinger type equation (NLSE) in (2+1)-dimensions which describes the nonlinear spin dynamics of Heisenberg ferromagnetic spin chains (HFSC) with anisotropic and bilinear interactions in the semiclassical limit. Two integration schemes are employed to study the equation. These are the complex envelope function ansatz and the generalized tanh methods. Dark, dark-bright or combined optical and singular soliton solutions of the equation are derived. Furthermore, the modulational instability (MI) is studied based on the standard linear-stability analysis and the MI gain is got. Numerical simulation of the obtained results are analyzed with interesting figures showing the physical meaning of the solutions.

Braun’s Lipoprotein Facilitates OmpA Interaction with the Escherichia coli Cell Wall

Gram-negative bacteria such as Escherichia coli are protected by a complex cell envelope. The development of novel therapeutics against these bacteria necessitates a molecular level understanding of the structure-dynamics-function relationships of the various components of the cell envelope. We use atomistic MD simulations to reveal the details of covalent and noncovalent protein interactions that link the outer membrane to the aqueous periplasmic region. We show that the Braun’s lipoprotein tilts and bends, and thereby lifts the cell wall closer to the outer membrane. Both monomers and dimers of the outer membrane porin OmpA can interact with peptidoglycan in the presence of Braun’s lipoprotein, but in the absence of the latter, only dimers of OmpA show a propensity to form contacts with peptidoglycan. Our study provides a glimpse of how the molecular components of the bacterial cell envelope interact with each other to mediate cell wall attachment in E. coli.

Optical solitons and modulation instability analysis with (3 + 1)-dimensional nonlinear Shrödinger equation

This paper addresses the (3 + 1)-dimensional nonlinear Shrödinger equation (NLSE) that serves as the model to study the propagation of optical solitons through nonlinear optical fibers. Two integration schemes are employed to study the equation. These are the complex envelope function ansatz and the solitary wave ansatz with Jaccobi elliptic function methods, we present the exact dark, bright and dark-bright or combined optical solitons to the model. The intensity as well as the nonlinear phase shift of the solitons are reported. The modulation instability aspects are discussed using the concept of linear stability analysis. The MI gain is got. Numerical simulation of the obtained results are analyzed with interesting figures showing the physical meaning of the solutions.

Parametric instability of oscillations of a vortex ring in a z-periodic Bose condensate and return to the initial state

The dynamics of deformations of a quantum vortex ring in a Bose-Einstein condensate with periodic equilibrium density $\rho(z)= 1-\epsilon\cos z$ has been considered within the local induction approximation. Parametric instabilities of the normal modes with azimuthal numbers $\pm m$ have been revealed at the energy integral $E$ near values $E_m^{(p)}=2m\sqrt{m^2-1}/p$, where $p$ is the resonance order. Numerical simulations have shown that already at $\epsilon\sim 0.03$ a rapid growth of unstable modes with $m=2$, $p=1$ to magnitudes of order of unity is typical, which is then followed, after a few large oscillations, by fast return to a weakly excited state. Such behavior corresponds to an integrable Hamiltonian of the form $H\propto \sigma(E_2^{(1)}-E)(|b_+|^2 + |b_-|^2) -\epsilon(b_+ b_- + b_+^* b_-^*) +u(|b_+|^4 +|b_-|^4) + w |b_+|^2|b_-|^2$ for two complex envelopes $b_\pm(t)$. The results have been compared to parametric instabilities of vortex ring in condensate with density $\rho(z,r)=1-r^2-\alpha z^2$, which take place at $\alpha\approx 8/5$ and at $\alpha\approx 16/7$.

Outer nuclear membrane protein Kuduk modulates the LINC complex and nuclear envelope architecture.

Linker of nucleoskeleton and cytoskeleton (LINC) complexes spanning the nuclear envelope (NE) contribute to nucleocytoskeletal force transduction. A few NE proteins have been found to regulate the LINC complex. In this study, we identify one, Kuduk (Kud), which can reside at the outer nuclear membrane and is required for the development of Drosophila melanogaster ovarian follicles and NE morphology of myonuclei. Kud associates with LINC complex components in an evolutionarily conserved manner. Loss of Kud increases the level but impairs functioning of the LINC complex. Overexpression of Kud suppresses NE targeting of cytoskeleton-free LINC complexes. Thus, Kud acts as a quality control mechanism for LINC-mediated nucleocytoskeletal connections. Genetic data indicate that Kud also functions independently of the LINC complex. Overexpression of the human orthologue TMEM258 in Drosophila proved functional conservation. These findings expand our understanding of the regulation of LINC complexes and NE architecture.

Optical solitons, nonlinear self-adjointness and conservation laws for the cubic nonlinear Shrödinger's equation with repulsive delta potential

In this paper, the complex envelope function ansatz method is used to acquire the optical solitons to the cubic nonlinear Shrödinger's equation with repulsive delta potential (δ−NLSE). The method reveals dark and bright optical solitons. The necessary constraint conditions which guarantee the existence of the solitons are also presented. We studied the δ−NLSE by analyzing a system of partial differential equations (PDEs) obtained by decomposing the equation into real and imaginary components. We derive the Lie point symmetry generators of the system and prove that the system is nonlinearly self-adjoint with an explicit form of a differential substitution satisfying the nonlinear self-adjoint condition. Then we use these facts to establish a set of conserved vectors for the system using the general Cls theorem presented by Ibragimov. Some interesting figures for the acquired solutions are also presented.