Envelope Function Research Articles

Extracellular vesicles from Zika virus-infected cells display viral E protein that binds ZIKV-neutralizing antibodies to prevent infection enhancement.

Mosquito-borne flaviviruses including Zika virus (ZIKV) represent a public health problem in some parts of the world. Although ZIKV infection is predominantly asymptomatic or associated with mild symptoms, it can lead to neurological complications. ZIKV infection can also cause antibody-dependent enhancement (ADE) of infection with similar viruses, warranting further studies of virion assembly and the function of envelope (E) protein-specific antibodies. Although extracellular vesicles (EVs) from flavivirus-infected cells have been reported to transmit infection, this interpretation is challenged by difficulties in separating EVs from flavivirions due to their similar biochemical composition and biophysical properties. In the present study, a rigorous EV-virion separation method combining sequential ultracentrifugation and affinity capture was developed to study EVs from ZIKV-infected cells. We find that these EVs do not transmit infection, but EVs display abundant E proteins which have an antigenic landscape similar to that of virions carrying E. ZIKV E-coated EVs attenuate antibody-dependent enhancement mediated by ZIKV E-specific and DENV-cross-reactive antibodies in both cell culture and mouse models. We thus reportan alternative route for Flavivirus E protein secretion. These results suggest that modulation of E protein release via virions and EVs may present a new approach to regulating flavivirus-host interactions.

Nonlinear random vibration of the slender deep-water pier under seismic excitation

The present study investigates the nonlinear random vibration of the deep-water pier exposed to horizontal seismic excitation. First of all, the stochastic dynamic model of the pier is formulated. During the process, the pier is simplified as a cantilever beam fixed on the rock foundation, the seismic excitation is treated as Gaussian white noise, the hydrodynamic pressure is described with the radiation wave theory, and the equation for the nonlinear kinematic of the pier is deduced by the means of Kane’s method. Then, with the application of the stochastic averaging (SA) technique, the Fokker–Plank–Kolmogorov (FPK) equation governing the transient probability density function (PDF) of the amplitude envelope and the backward Kolmogorov (BK) equation for the conditional reliability function (CRF) are derived, respectively. The closed-form stationary PDF can be yielded directly from the reduced FPK equation, while the CRF and the conditional PDF of first-passage time are given after solving the BK equation numerically. Numerical discussions are performed to illustrate the trend of excitation intensity, mass ratio, immersion ratio, and inner and outer hydrodynamic effect on the stationary response and first-passage failure are examined, respectively. It has been shown that increases in the excitation intensity, mass ratio, and immersion ratio can amplify the response and reduce the reliability of the deep-water pier system. The hydrodynamic effect also leads to an amplification of the system response and a reduction in the reliability of the system. Similarly, the presence of inner water can also exacerbate these effects, and this phenomenon becomes more pronounced with increasing immersed ratios. Additionally, the analytical solution is validated by the result obtained by pertained Monte Carlo simulations (MCS). It is noted that this work will be helpful for the optimal seismic design of deep-water piers.

Computationally Efficient Handling of Partially Coherent Electron Sources in (S)TEM Image Simulations via Matrix Diagonalization.

We introduce a novel method to improve the computational efficiency for (S)TEM image simulation by employing matrix diagonalization of the mixed envelope function (MEF). The MEF is derived by taking the finite size and the energy spread of the effective electron source into account, and is a component of the transmission cross-coefficient that accounts for the correlation between partially coherent waves. Since the MEF is a four-dimensional array and its application in image calculations is time-consuming, we reduce the computation time by using its eigenvectors. By incorporating the aperture function into the matrix diagonalization, only a small number of eigenvectors are required to approximate the original matrix with high accuracy. The diagonalization enables for each eigenvector the calculation of the corresponding image by employing the coherent model. The individual images are weighted by the corresponding eigenvalues and then summed up, resulting in the total partially coherent image.

Hybrid uncertainty analysis and optimisation based on probability box for bus powertrain mounting system

In engineering practice, the bus powertrain mounting system (BPMS) may have both epistemic and aleatory uncertainty under the influence of manufacturing, measurement, and assembly errors. The hybrid uncertainty in BPMS may result in over-design or insufficient design. Therefore, the probability box (p-box) model, which can handle both aleatory and epistemic variables, is introduced into the uncertainty analysis of BPMS. Considering the elastic connection between the compressor and powertrain, a 12-degree-of-freedom dynamic model is constructed to calculate the inherent characteristic of BPMS. A rejection sampling method based on the fast envelope function (RSMBFEF) is proposed to propagate the hybrid uncertainties. Then double-loop Monte Carlo method is used to be compared with RSMBFEF. To reduce the number of uncertainty analyses, a two-step uncertainty optimisation method is proposed. Finally, the proposed method's efficacy and accuracy are verified through a numerical case. The applicability of the p-box model is illustrated by comparing it with the BPMS model with only pure aleatory or pure interval variables.

Extraction of Group Velocity Dispersion Curves of Surface Waves Using Continuous Wavelet Transform

Surface wave tomography is performed by first estimating surface wave dispersion curves and then inverting them. The objective of this paper is the efficient and reliable estimation of the group velocity dispersion curves of surface waves. In this paper, group velocity dispersion curves of surface waves recorded at a single station with known location of seismic source or between a pair of stations are estimated using continuous wavelet transform (CWT). The advantage of CWT is its multi-resolution property and flexible choice of analyzing function. In the proposed method, the number of CWT filters used are almost half of the total number of filters used in the conventional frequency-time analysis (FTAN) method. The CWT coefficients of the seismogram are the functions of time and scale (analogues to wave period). The arrival time to reach the peak of the envelope function of CWT coefficients is estimated to calculate group velocity of the surface waves. Group velocity dispersion curve of the surface waves is the plot of change of group velocity with the period. Synthetic test data and ambient noise recordings of MesoAmerica Seismic Experiment (MASE) stations are acquired to investigate the performance of the proposed method. It is observed that the proposed method effectively retrieves the weaker surface waves and results the broader band group-velocity dispersion curve when compared to the conventional FTAN method. The proposed method is also found to be computationally efficient.

Dystonia genes and their biological pathways.

High-throughput sequencing has been instrumental in uncovering the spectrum of pathogenic genetic alterations that contribute to the etiology of dystonia. Despite the immense heterogeneity in monogenic causes, studies performed during the past few years have highlighted that many rare deleterious variants associated with dystonic presentations affect genes that have roles in certain conserved pathways in neural physiology. These various gene mutations that appear to converge towards the disruption of interconnected cellular networks were shown to produce a wide range of different dystonic disease phenotypes, including isolated and combined dystonias as well as numerous clinically complex, often neurodevelopmental disorder-related conditions that can manifest with dystonic features in the context of multisystem disturbances. In this chapter, we summarize the manifold dystonia-gene relationships based on their association with a discrete number of unifying pathophysiological mechanisms and molecular cascade abnormalities. The themes on which we focus comprise dopamine signaling, heavy metal accumulation and calcifications in the brain, nuclear envelope function and stress response, gene transcription control, energy homeostasis, lysosomal trafficking, calcium and ion channel-mediated signaling, synaptic transmission beyond dopamine pathways, extra- and intracellular structural organization, and protein synthesis and degradation. Enhancing knowledge about the concept of shared etiological pathways in the pathogenesis of dystonia will motivate clinicians and researchers to find more efficacious treatments that allow to reverse pathologies in patient-specific core molecular networks and connected multipathway loops.

О ПРИМЕНИМОСТИ МЕТОДА БЫСТРОГО ЦИФРОВОГО ФОРМИРОВАНИЯ ХАРАКТЕРИСТИК НАПРАВЛЕННОСТИ В СИСТЕМАХ ЛОКАЦИИ СО СЛОЖНЫМИ СИГНАЛАМИ

This work belongs to the field of hydroacoustics, namely to the problem of digitalbeamforming based on spatial fast Fourier transform (FFT) in a multibeam echo sounder(MLS) with baseband digital signal processing. The applicability of FFT-based beamformingwhen using relatively broadband signals is considered. The main attention is paid to the MLSwith a static beam pattern, at the same time, obtained results are also applicable to rangingsystems that provide dynamic beam control. The aim of the study is to establish the relatio nshipbetween the relative width of the signal spectrum and signal level in the spatial channelof the MLS with a given maximum beam steering. A qualitative condition for the applicabilityof FFT-based spatial beamforming for a probing signal with a given relative bandwidth isdetermined. An analytical expression linking the signal attenuation coefficient in the spatialchannel with the following signal and receiver characteristics was obtained: the number ofelements of the linear equidistant antenna array, the distance between array elements, beamsteering, the correlation function of the complex envelope of the signal, the window functionfor weighting the matched filter response in spectral domain. Presented results can be usefulin designing multibeam echo sounders, providing high resolution both in range and in angularcoordinates.

An improved time-domain approach for the spectra-compatible seismic motion generation considering intrinsic non-stationary features

The dynamic structural responses are sensitive to the time-frequency content of seismic waves, and seismic input motions in time-history analysis are usually required to be compatible with design response spectra according to nuclear codes. In order to generate spectra-compatible input motions while maintaining the intrinsic non-stationarity of seismic waves, an improved time-domain approach is proposed in this paper. To maintain the nonstationary characteristics of the given seismic waves, a new time-frequency envelope function is constructed using the Hilbert amplitude spectrum. Based on the intrinsic mode functions (IMFs) obtained from given seismic waves through variational mode decomposition, a new corrective time history is constructed to locally modify the given seismic waves. The proposed corrective time history and time-frequency envelope function are unique for each earthquake records as they are extracted from the given seismic waves. In addition, a dimension reduction iterative technique is presented herein to simultaneously superimpose corrective time histories of all the damping ratios at a specific frequency in the time domain according to optimal weights, which are found by the genetic algorithm (GA). Examples are presented to show the capability of the proposed approach in generating spectra-compatible time histories, especially in maintaining the nonstationary characteristics of seismic records. And numerical results reveal that the modified time histories generated by the proposed method can obtain similar dynamic behaviors of AP1000 nuclear power plant with the natural seismic records. Thus, the proposed method can be efficiently used in the design practices.

Phase-Change Materials, 1/f Noise, and Phase Synchrony

In this article, we study 1 / f γ , γ ≈ 1 electrical noise in amorphous phase-change materials. Given the relevance of noise in recent applications, it is necessary to gain a deeper perspective on its nature in phase-change semiconductors, a promising class of materials. Electron conduction is envisaged in terms of an envelope function and a field-dependent Bloch wave function; the electron transport across the structure is modeled as driven phase oscillators under a weak field and obeys a Kuramoto-type equation. Its solutions naturally divide into a phase-synchronized group and phase-desynchronized oscillators. The former is comprised by long-lived pairs or aggregates and are responsible for 1 / f , γ = 1 noise. We identify the dividing frequency between γ = 1 noise and γ ≠ 1 noise. The phase-desynchronized carriers generate γ ≠ 1 noise and are single carriers, not aggregates, and are short-lived. We apply our analysis to recent experiments.

Biphoton engineering using modal spatial overlap on-chip.

Photon pairs generated by spontaneous parametric downconversion are essential for optical quantum information processing, in which the quality of biphoton states is crucial for the performance. To engineer the biphoton wave function (BWF) on-chip, the pump envelope function and the phase matching function are commonly adjusted, while the modal field overlap has been considered as a constant in the frequency range of interest. In this work, by using modal coupling in a system of coupled waveguides, we explore the modal field overlap as a new degree of freedom for biphoton engineering. We provide design examples for on-chip generations of polarization entangled photons and heralded single photons. This strategy can be applied to waveguides of different materials and structures, offering new possibilities for photonic quantum state engineering.

STEM-06. NUCLEAR STRUCTURE MAINTAINS GLIOBLASTOMA STEM CELLS

Abstract Glioblastoma stem cells (GSCs) contribute to therapeutic resistance, promote tumor angiogenesis, and evade anti-tumor immune responses. We and others have shown that GSCs display differential regulation of their epigenetic landscapes and metabolic profiles and contribute to the striking cellular heterogeneity and complex tumor microenvironments. Here, we find that GSCs undergo dramatic changes in chromatin organization and nuclear morphology upon differentiation. Leveraging unbiased RNA sequencing and protein profiling screens comparing GSCs and differentiated glioma cells, we identified nuclear membrane molecular regulation that defines nuclear size and lipid regulation. Genetic or pharmacologic targeting of nuclear envelope function reduced cancer stem cell proliferation, self-renewal, and in vivo tumor growth. Collectively, we define a novel role of the nuclear envelope in maintaining chromatin state and cancer stem cell self-renewing, informing the development of novel potential therapeutic paradigms for glioblastoma.

Regulated degradation of the inner nuclear membrane protein SUN2 maintains nuclear envelope architecture and function.

Nuclear architecture and functions depend on dynamic interactions between nuclear components (such as chromatin) and inner nuclear membrane (INM) proteins. Mutations in INM proteins interfering with these interactions result in disease. However, mechanisms controlling the levels and turnover of INM proteins remain unknown. Here, we describe a mechanism of regulated degradation of the INM SUN domain-containing protein 2 (SUN2). We show that Casein Kinase 2 and the C-terminal domain Nuclear Envelope Phosphatase 1 (CTDNEP1) have opposing effects on SUN2 levels by regulating SUN2 binding to the ubiquitin ligase Skp/Cullin1/F-BoxβTrCP (SCFβTrCP). Upon binding to phosphorylated SUN2, SCFβTrCP promotes its ubiquitination. Ubiquitinated SUN2 is membrane extracted by the AAA ATPase p97 and delivered to the proteasome for degradation. Importantly, accumulation of non-degradable SUN2 results in aberrant nuclear architecture, vulnerability to DNA damage and increased lagging chromosomes in mitosis. These findings uncover a central role of proteolysis in INM protein homeostasis.

Estimation of Truncation Error in Statistical Description of Communication Signals over mm-Wave Channels

This paper presents an illustration of how knowledge from the field of special functions, orthogonal polynomials and numerical series can be applied to solve a very important problem in the field of modern wireless communications. We present the formulas for the probability density function (PDF) and cumulative distribution function (CDF) of the composite signal envelope over an mm-Wave channel. The formulas for the PDF and CDF are expressed in the convergent infinity series form. The main contribution of the paper is in estimating the upper bounds for absolute truncation error in evaluating PDF and CDF of the signal envelope. We also derive the formulas for the required number of terms in the summation under the condition of achieving a given accuracy for typical values of channel parameters. In deriving these formulas, we use the alternating series estimation theorem, as well as some properties of orthogonal polynomials in order to derive upper bounds for hypergeometric functions. Based on the newly derived formulas, numerical results are presented and commented upon. The analytical results are verified by Monte Carlo simulations. The results are essential in the designing and performance estimating of the fifth-generation (5G) and beyond wireless networks.

About an (Im‐)Possible Anomaly in Band Structure Theory

Based on an envelope function approach pioneered by Wannier and Slater, it can be shown that under the influence of strong effective magnetic fields in spinor space the band structure of certain materials gives rise to the analogs of tardyons and luxons, and in principle also to the analogs of tachyons. Such a (hypothetical) tachyonic band structure would be metallic, but with a gap in k ‐space and not in the range of allowed band energies . Some of the conditions to observe such a tachyonic anomaly in certain types of electronic band structures, which do not seem to be implausible, are discussed. Similar anomalies should appear in the spectrum of Landau levels. Furthermore, some of the pathologies that would come with such exotic band structure anomalies are pointed out.

Scattering of a twisted electron wavepacket by a finite laser pulse

The behavior of a twisted electron colliding with a linearly polarized laser pulse is investigated within relativistic quantum mechanics. In order to better fit the real experimental conditions, we introduce a Gaussian spatial profile for the initial electron state as well as an envelope function for the laser pulse, so the both interacting objects have a finite size along the laser propagation direction. For this setup we analyze the dynamics of various observable quantities regarding the electron state: the probability density, angular momentum, and mean values of the spatial coordinates. It is shown that the motion of a twisted wavepacket can be accurately described by averaging over classical trajectories with various directions of the transverse momentum component. On the other hand, full quantum simulations demonstrate that the ring structure of the wavepacket in the transverse plane can be significantly distorted leading to large uncertainties in the total angular momentum of the electron. This effect remains after the interaction once the laser pulse has a nonzero electric-field area.

Quality control mechanisms that protect nuclear envelope identity and function.

The nuclear envelope (NE) is a specialization of the endoplasmic reticulum with distinct biochemistry that defines inner and outer membranes connected at a pore membrane that houses nuclear pore complexes (NPCs). Quality control mechanisms that maintain the physical integrity and biochemical identity of these membranes are critical to ensure that the NE acts as a selective barrier that also contributes to genome stability and metabolism. As the proteome of the NE is highly integrated, it is challenging to turn over by conventional ubiquitin-proteasome and autophagy mechanisms. Further, removal of entire sections of the NE requires elaborate membrane remodeling that is poorly understood. Nonetheless, recent work has made inroads into discovering specializations of cellular degradative machineries tailored to meeting the unique challenges imposed by the NE. In addition, cells have evolved mechanisms to surveil and repair the NE barrier to protect against the deleterious effects of a breach in NE integrity, in the form of either a ruptured NE or a dysfunctional NPC. Here, we synthesize the most recent work exploring NE quality control mechanisms across eukaryotes.

Controlling thermodynamics of a quantum heat engine with modulated amplitude drivings.

External driving of bath temperatures with a phase difference of a nonequilibrium quantum engine leads to the emergence of geometric effects on the thermodynamics. In this work we modulate the amplitude of the external driving protocols by introducing envelope functions and study the role of geometric effects on the flux, noise, and efficiency of a four-level driven quantum heat engine coupled with two thermal baths and a unimodal cavity. We observe that having a finite width of the modulation envelope introduces an additional control knob for studying the thermodynamics in the adiabatic limit. The optimization of the flux as well as the noise with respect to thermally induced quantum coherences becomes possible in the presence of geometric effects, which hitherto has not been possible with sinusoidal driving without an envelope. We also report the deviation of the slope and generation of an intercept in the standard expression for efficiency at maximum power as a function of Carnot efficiency in the presence of geometric effects under the amplitude modulation. Further, a recently developed universal bound on the efficiency obtained from the thermodynamic uncertainty relation is shown not to hold when a small width of the modulation envelope along with a large value of cavity temperature is maintained.

Theory of silicon spin qubit relaxation in a synthetic spin-orbit field

We develop the theory of single-electron silicon spin qubit relaxation in the presence of a magnetic field gradient. Such field gradients are routinely generated by on-chip micromagnets to allow for electrically controlled quantum gates on spin qubits. We build on a valley-dependent envelope function theory that enables the analysis of the electron wave function in a silicon quantum dot with an arbitrary roughness at the interface. We assume the presence of single-layer atomic steps at a Si/SiGe interface and study how the presence of a gradient field modifies the spin-mixing mechanisms. We show that our theoretical modeling can quantitatively reproduce results of experimental measurements of qubit relaxation in silicon in the presence of a micromagnet. We further study in detail how a field gradient can modify the EDSR Rabi frequency of a silicon spin qubit. While this strongly depends on the details of the interface roughness, interestingly, we find that adding a micromagnet on top of a spin qubit with an ideal interface can even reduce the EDSR frequency within some interval of the external magnetic field strength.

Frequency-Coded and Programmable Synchronous Electromagnetic Encoders Based on Linear Strips

This letter presents electromagnetic encoders where encoding is achieved by considering four different inclusions, particularly linear strips of different length, etched at the predefined positions of the encoder chain, and transversely oriented with regard to the chain axis. Since the length of the strips determines their resonance frequencies, it follows that the 2-bits per inclusion, corresponding to the four possible different states (strip lengths), are frequency-coded. Thus, the reader is a microstrip line with a series gap fed by four harmonic (carrier) signals tuned to the resonance frequencies of the four considered encoder strips. By encoder motion over the reader, each carrier signal is amplitude modulated, with envelope functions exhibiting a peak each time a strip of the encoder chain tuned to the resonance frequency of the considered carrier signal crosses the axis of the reader line. The functionality of the system is experimentally validated in this letter. It is also shown that the encoders can be programmed by considering identical strips and by cutting them appropriately, according to the desired code. The proposed encoders are intrinsically synchronous. Such encoders are useful for measuring displacements and velocities, as well as for the implementation of synchronous near-field chipless radiofrequency identification tags with sequential bit reading.

Photoreflectance studies of the band gap alignments in boron diluted BGaInAs/GaAs quantum wells

Band gap alignments of BGaInAs/GaAs quantum wells with mole fractions of indium around 40% and mole fractions of boron ranging from 0% up to 4.75% are studied experimentally by photoreflectance (PR) and photoluminescence (PL). Obtained results are explained within a k · p model within an envelope function approximation. The study shows an increase of the valence band offset with an addition of boron into the thin film at a rate of around 4.2% per 1% of boron incorporated. Non-zero bowing parameters of valence band offsets for ternary alloys with boron (BGaAs and BInAs) are estimated. Moreover, it was observed that unlike in other highly mismatched alloy systems the incorporation of boron does not significantly deteriorate the optical quality of the studied samples, i.e., the broadening of optical transitions observed in PR and PL is very comparable to that observed for the reference QW, and the PL properties of boron containing QWs are similar to the reference boron free QW. Some deterioration of optical quality due to the increased alloy inhomogeneity is observed only for the sample with the highest concentration of B (4.2%).