Transient Features Research Articles

Transient Two-Layer Electroosmotic Flow and Heat Transfer of Power-Law Nanofluids in a Microchannel.

To achieve the optimum use and efficient thermal management of two-layer electroosmosis pumping systems in microdevices, this paper studies the transient hydrodynamical features in two-layer electroosmotic flow of power-law nanofluids in a slit microchannel and the corresponding heat transfer characteristics in the presence of viscous dissipation. The governing equations are established based on the Cauchy momentum equation, continuity equation, energy equation, and power-law nanofluid model, which are analytically solved in the limiting case of two-layer Newtonian fluid flow by means of Laplace transform and numerically solved for two-layer power-law nanofluid fluid flow. The transient mechanism of adopting conducting power-law nanofluid as a pumping force and that of pumping nonconducting power-law nanofluid are both discussed by presenting the two-layer velocity, flow rates, temperature, and Nusselt number at different power-law rheology, nanoparticle volume fraction, electrokinetic width and Brinkman number. The results demonstrate that shear thinning conducting nanofluid represents a promising tool to drive nonconducting samples, especially samples with shear thickening features. The increase in nanoparticle volume fraction promotes heat transfer performance, and the shear thickening feature of conducting nanofluid tends to suppress the effects of viscous dissipation and electrokinetic width on heat transfer.

A Simple Radial Gradient Filter for Batch-Processing of Coronagraph Images

Images of the extended solar corona, as observed by different white-light coronagraphs, include the K- and F-corona and suffer from a radial variation in intensity. These images require separation of the two coronal components with some additional image-processing to reduce the intensity gradient and analyse the structures and processes occurring at different heights in the solar corona within the full field of view. Over the past few decades, coronagraphs have been producing enormous amounts of data, which will be continued with the launch of new telescopes. To process these bulk coronagraph images with steep radial-intensity gradients, we have developed the algorithm Simple Radial Gradient Filter (SiRGraF). This algorithm is based on subtracting a minimum background (F-corona) created using long-duration images and then dividing the resultant by a uniform-intensity-gradient image to enhance the K-corona. We demonstrate the utility of this algorithm to bring out the short-time-scale transient structures of the corona. SiRGraF can be used to reveal and analyse such structures. It is not suitable for quantitative estimations based on intensity. We have successfully tested the algorithm on images of the Large Angle Spectroscopic COronagraph (LASCO)-C2 onboard the Solar and Heliospheric Observatory (SOHO) and COR-2A onboard the Solar TErrestrial RElations Observatory (STEREO) with good signal-to-noise ratio (SNR) along with low-SNR images of STEREO/COR-1A and the KCoronagraph (KCor). We also compared the performance of SiRGraF with the existing widely used algorithm Normalizing Radial Gradient Filter (NRGF). We found that when hundreds of images have to be processed, SiRGraF works faster than NRGF, providing similar brightness and contrast in the images and separating the transient features. Moreover, SiRGraF works better on low-SNR images of COR-1A than on NRGF, providing better identification of dynamic coronal structures throughout the field of view. We discuss the advantages and limitations of the algorithm. The application of SiRGraF to COR-1 images can be extended for an automated coronal mass ejection (CME) detection algorithm in the future, which will help in our study of the characteristics of CMEs in the inner corona.

Kinematics analysis of the transient Milky Way warp using RGB stars from Gaia DR2

The perturbations to the Milky Way cause the disk to have bending or breathing wave, flare, and warp. Both spatial analyses from stellar and gas show the Milky Way warp can be approached with sinusoidal function to the Galactocentric longitude. In this research, we aim to find evidence of the transient Milky Way warp using kinematics data of the Red Giant Branch (RGB) stars from Gaia Data Release 2. We only use RGB stars with positive parallaxes and small parallax uncertainties where ϖ > 0 and ϖ/σϖ > 5, respectively. Using the linear warp model, we find the Milky Way warp starts on Rw = 10.72 kpc, with the amplitude (γw ) of 0.39 and the Line of Node lies on ϕw = −5.26°. Assumed the warp is a static long-lived feature on kinematics distribution, where all of the warp parameters are constant by the time, the observed vertical velocity (Vz ) is less than the expected one. The maximum Vz is not exceeded to 12.5 km/s rather 20 km/s derived from the proposed model. It infers that the warp drive on the Milky Way is a transient feature. One of the possible reasons is the recent interaction with satellite galaxies in perturbing the outer disk of the Milky Way.

State identification of home appliance with transient features in residential buildings

State identification of home appliance with transient features in residential buildings

Stable decoding of working memory load through frequency bands

ABSTRACT Numerous studies have shown that working memory modulates every frequency band’s power in the human brain. Yet, the question of how the highly distributed working memory adapts to external demands remains unresolved. Here, we explored frequency band modulations underlying working memory load, taking executive control under account. We hypothesized that synchronizations underlying various cognitive functions may be sequenced in time to avoid interference and that transient modulation of decoding accuracy of task difficulty would vary with increasing difficulty. We recorded whole scalp EEG data from 12 healthy participants, while they performed a visuo-spatial n-back task with three conditions of increasing difficulty, after an initial learning phase. We analyzed evoked spectral perturbations and time-resolved decoding of individual synchronization. Surprisingly, our results provide evidence for persistent decoding above the level-of-chance (83.17% AUC) for combined frequency bands. In fact, the decoding accuracy was higher for the combined than for isolated frequency bands (AUC from 65.93% to 74.30%). However, in line with our hypothesis, frequency band clusters transiently emerged in parieto-occipital regions within two separate time windows for alpha-/beta-band (relative synchronization from approximately 200 to 600 ms) and for the delta-/theta-band (relative desynchronization from approximately 600 to 1000 ms). Overall, these findings highlight concurrent sustained and transient measurable features of working memory load. This could reflect the emergence of stability within and between functional networks of the complex working memory system. In turn, this process allows energy savings to cope with external demands.

Investigation of the effects of non-Gaussian noise transients and their mitigation in parameterized gravitational-wave tests of general relativity

The detection of gravitational waves from compact binary coalescence by Advanced LIGO and Advanced Virgo provides an opportunity to study the strong-field, highly relativistic regime of gravity. Gravitational-wave tests of general relativity (GR) typically assume Gaussian and stationary detector noise and, thus, do not account for non-Gaussian, transient noise features (glitches). We present the results obtained by performing parametrized gravitational-wave tests on simulated signals from binary-black-hole coalescence overlapped with three classes of frequently occurring instrumental glitches with distinctly different morphologies. We then review and apply three glitch mitigation methods and evaluate their effects on reducing false deviations from GR. By considering nine cases of glitches overlapping with simulated signals, we show that the short-duration, broadband blip and tomte glitches under consideration introduce false violations of GR, and using an inpainting filter and glitch model subtraction can consistently eliminate such false violations without introducing additional effects.

Novelties in Autoimmune and Paraneoplastic Cerebellar Ataxias: Twenty Years of Progresses.

Major advances in our knowledge concerning autoimmune and paraneoplastic cerebellar ataxias have occurred in the last 20 years. The discovery of several neural antibodies represents an undeniable contribution to this field, especially those serving as good biomarkers of paraneoplastic neurological syndromes and those showing direct pathogenic effects. Yet, many patients still lack detectable or known antibodies, and also many antibodies have only been reported in few patients, which makes it difficult to define in detail their clinical value. Nevertheless, a notable progress has additionally been made in the clinical characterization of patients with the main neural antibodies, which, although typically present with a subacute pancerebellar syndrome, may also show either hyperacute or chronic onsets that complicate the differential diagnoses. However, prodromal and transient features could be useful clues for an early recognition, and extracerebellar involvement may also be highly indicative of the associated antibody. Moreover, important advances in our understanding of the pathogenesis of cerebellar ataxias include the description of antibody effects, especially those targeting cell-surface antigens, and first attempts to isolate antigen-specific T-cells. Furthermore, genetic predisposition seems relevant, although differently involved according to cancer association, with particular HLA observed in non-paraneoplastic cases and genetic abnormalities in the tumor cells in paraneoplastic ones. Finally, immune checkpoint inhibitors used as cancer immunotherapy may rarely induce cerebellar ataxias, but even this undesirable effect may in turn serve to shed some light on their physiopathology. Herein, we review the principal novelties of the last 20 years regarding autoimmune and paraneoplastic cerebellar ataxias.

Period-assisted adaptive parameterized wavelet dictionary and its sparse representation for periodic transient features of rolling bearing faults

Accurate extraction of fault-induced periodic transient features from noise interference containing harmonics and large-amplitude random impulses is a key to fault detection of rolling bearings. Therefore, this paper proposes a sparse representation method based on a period-assisted adaptive parameterized wavelet dictionary to extract periodic transient features of rolling bearing faults. First, considering the influence of noise and vibration transmission paths on impulse response generated by bearing faults, an asymmetric bilateral exponential attenuation wavelet is constructed according to a vibration model of impulse response, which can be more flexible to match impulse features in vibration signals. Meanwhile, an adaptive correlation filtering method and a benchmark atom obtained by a standard K-SVD are utilized to determine optimal parameters of the constructed wavelet, which is less disturbed by noise and harmonics. On this basis, by introducing a priori knowledge of an impulse period, a method of constructing a period-assisted parameterized wavelet dictionary is proposed to get a dictionary that is suitable to characterize periodic transient features. Finally, a periodic transient signal is recovered using the constructed dictionary and the orthogonal matching pursuit (OMP) algorithm. Comparisons with the K-SVD, a sparse representation method based on a db8 wavelet dictionary, spectral correlation and spectral kurtosis demonstrate that the proposed method can more accurately extract periodic transient features in simulated and experimental vibration signals, which provides an effective analysis tool for rolling bearing fault detection.

Numerical study of transient characteristics of a standing-wave thermoacoustic heat engine

Understanding of transient fluid flow and heat transfer characteristics within thermoacoustic devices is crucial to improve their start up processes and subsequently the achievable efficiencies. The present numerical study investigates the transient features of a standing-wave quarter-wavelength thermoacoustic heat engine composed of hot and cold heat exchangers, a stack, and a resonator. The non-linear fluid dynamical as well as energy equations are solved on the structured grids by resolving viscous and thermal boundary layers using OpenFOAM software. Full discretization of governing equations captured nonlinear features of flow at high pressure amplitudes which are typically ignored by the linear theory. The results show the existence of acoustic streaming phenomenon in the system due to the interaction of Stokes boundary layer adjacent to the solid regions which can lead to undesirable convective heat transport and as a result the reduction of the system efficiency.

Glaciotectonic disintegration of roches moutonnées during glacial ripping in east Sweden

ABSTRACT Roches moutonnées are typical landforms of glacial erosion developed in hard rocks, with an asymmetric profile caused by abrasion and lee-side plucking. In eastern Sweden, some roches moutonnées show extensive damage, including open fractures, disintegration into blocks, fracture caves and short boulder trains. Disintegration increases along ice-flow directions during deglaciation of the last Weichselian Fennoscandian Ice Sheet, indicating a subglacial origin: limited edge rounding can be explained by a combination of hard rock, slow abrasion rates and disintegration just prior to deglaciation. The roches moutonnées initially developed in kernels of gneissic rocks with a wide fracture spacing (large block size) and interlocking fracture pattern, and hence high overall rock mass strength. Dilated fractures and ‘fracture caves’ occur up to 15 m below the ice-bed interface. It is proposed that hydraulic jacking by overpressured water opened up the rock mass along pre-existing fractures. Jacking reduced rock mass strength, allowing glaciotectonic deformation of the roches moutonnées. Uneven hydraulic jacking led to uplift of individual fracture-bound blocks above the pre-existing smooth, abraded surface of the roches moutonnées, creating blunt, step-like edges. These edges allowed high ice pushing forces to act on large blocks: where blocks extend into the deeper rock mass, they further aided the disintegration of the rock mass. The disintegrated roches moutonnées can be regarded as transient features between intact bedrock and complete disintegration into boulders. The jacking-disintegration-transport sequence is characteristic of glacial ripping and very different from classic lee-side plucking.

Human embryonic development: from peri-implantation to gastrulation.

The basic body plan of the mammalian embryo is established through gastrulation, a pivotal early postimplantation event during which the three major germ layers (endoderm, ectoderm, and mesoderm) are specified with cellular and spatial diversity. Despite its basic and clinical importance, human embryo development from peri-implantation to gastrulation remains shrouded in mystery. Recent advances in the elongated in vitro culture of rodent and non-primate embryos and the construction of embryo-like structures have helped to improve understanding of the mechanisms of human early embryonic development. Here, we review the recent advances and possible future directions in the development of in vitro models to better understand human embryogenesis from peri-implantation to gastrulation.

Performance of a multi-stage thermoacoustically-driven pulse tube cryocooler: Uncertainty quantification and sensitivity analysis

• An octa-engine four-stage cryocooler utilizing low-grade heat source is proposed. • A temperature difference of 132 K at a no-load cold temperature of 77 K is achieved. • Increasing stages reduces hot temperature, but with a lower exergetic efficiency. • Thermal conductivity and engine’s mesh number strongly influence cooling features. • The onset hot temperature has a linear relation with the connecting tube’s length. The current paper presents the broad-range sensitivity analysis and uncertainty quantification for the performance of a thermoacoustically-driven pulse tube cryocooler to make it robustly perform using a low-grade heat source. Accordingly, the onset and steady-periodic operations of the cryocooler are numerically simulated using Rott’s one-dimensional equations. The effects of increasing hot/cold core’s number, engine’s phase-shifter length, and mean pressure on the cooling features and hot-source temperature are investigated. In this regard, a looped-branched, octa-engine, four-stage cryocooler is proposed that operates with a steady temperature difference of 132 K at a no-load cold temperature of 77 K. In contrast to previous findings, the results show that increasing the number of stages or the charge pressure does not necessarily improve thermodynamic performance. Moreover, the uncertainty in the operation of a quad and octa-engine, four-stage cryocooler caused by the geometric and material characteristics is estimated using the Morris method. It is demonstrated that the overall operation is more sensitive to the hot-core dimensions than to the cold-core dimensions. Besides the hot-core dimensions, gas properties and solid thermal conductivity strongly influence the transient and steady-periodic features of the cryocooler, respectively. Furthermore, doubling the hot cores in the four-stage system increases the uncertainty of the acoustic power up to five times, leading to more uncertainty in the cooling features. Drawing on the results of this paper, a multi-stage cryocooler can be designed to optimize the overall performance and reliability.

CUT&RUN Profiling of the Budding Yeast Epigenome.

Mapping the epigenome is key to describe the relationship between chromatin landscapes and the control of DNA-based cellular processes such as transcription. Cleavage under targets and release using nuclease (CUT&RUN) is an in situ chromatin profiling strategy in which controlled cleavage by antibody-targeted Micrococcal Nuclease solubilizes specific protein-DNA complexes for paired-end DNA sequencing. When applied to budding yeast, CUT&RUN profiling yields precise genome-wide maps of histone modifications, histone variants, transcription factors, and ATP-dependent chromatin remodelers, while avoiding cross-linking and solubilization issues associated with the most commonly used chromatin profiling technique Chromatin Immunoprecipitation (ChIP). Furthermore, targeted chromatin complexes cleanly released by CUT&RUN can be used as input for a subsequent native immunoprecipitation step (CUT&RUN.ChIP) to simultaneously map two epitopes in single molecules genome-wide. The intrinsically low background and high resolution of CUT&RUN and CUT&RUN.ChIP allows for identification of transient genomic features such as dynamic nucleosome-remodeling intermediates. Starting from cells, one can perform CUT&RUN or CUT&RUN.ChIP and obtain purified DNA for sequencing library preparation in 2days.

Properties of pursuit movements.

This chapter describes dynamic properties of smooth pursuit, visual and non-visual stimuli for pursuit, smooth eye-head tracking movements, and plastic-adaptive properties of pursuit. Step-ramp visual stimulus motion has revealed important properties of pursuit, including the latency to onset, initial acceleration, accuracy, and transient oscillations-all features that have been used to develop models of the pursuit system, discussed in the chapter "Models of pursuit" by Robinson. The role of predictive neural mechanisms in generating pursuit movements that anticipate target motion, and that enable near-perfect tracking of sinusoidal target motion, are examined. Smooth pursuit can be generated in response to targets that do not move, such as stroboscopic lights and images stabilized in the periphery of vision. The view that, during combined eye-head pursuit, the pursuit signal is used to cancel the vestibulo-ocular reflex is an incomplete hypothesis, contradicted by behavioral and electrophysiological findings. Smooth pursuit shows adaptive capabilities, evident in individuals who develop extraocular muscle palsies.

Local Defect Detection of Ferromagnetic Metal Casing Based on Pulsed Eddy Current Testing

Remote-field eddy current testing (RFECT)-based methods have been widely used in conductive pipe evaluation. However, the response signals of RFECT are affected both by the casing thicknesses around the driver coil and in the vicinity of the pick-up coil, making it difficult to invert and separate the thicknesses around the coils. Moreover, the relative permeability difference between the near-field and the remote-field zones causes a further deviation in the thickness inversion. To avoid these problems, a near-field pulsed eddy current testing method is proposed for defect evaluation. Time-domain transient features, which can be applied for defect detection, are analyzed based on the theoretical data of pulsed eddy current testing. A prototype of the testing apparatus and a defective ferromagnetic metal casing are designed to verify the feature performance for defect evaluation. The experimental results indicate that the time-related features are sensitive to circumferential defects and insensitive to the axial defects, and the magnitude-related feature is sensitive to both the circumferential and axial defects. Therefore, the magnitude-based method can be used to detect the local defects of ferromagnetic metal casings.

Defect dynamics in active polar fluids vs. active nematics.

Topological defects play a key role in two-dimensional active nematics, and a transient role in two-dimensional active polar fluids. Using a variational method, we study both the transient and long-time behavior of defects in two-dimensional active polar fluids in the limit of strong order and overdamped, compressible flow, and compare the defect dynamics with the corresponding active nematics model studied recently. One result is non-central interactions between defect pairs for active polar fluids, and by extending our analysis to allow orientation dynamics of defects, we find that the orientation of +1 defects, unlike that of ±1/2 defects in active nematics, is not locked to defect positions and relaxes to asters. Moreover, using a scaling argument, we explain the transient feature of active polar defects and show that in the steady state, active polar fluids are either devoid of defects or consist of a single aster. We argue that for contractile (extensile) active nematic systems, +1 vortices (asters) should emerge as bound states of a pair of +1/2 defects, which has been recently observed. Moreover, unlike the polar case, we show that for active nematics, a linear chain of equally spaced bound states of pairs of +1/2 defects can screen the activity term. A common feature in both models is the appearance of +1 defects (elementary in polar and composite in nematic) in the steady state.

Anthropogenic aerosol and cryosphere changes drive Earth’s strong but transient clear-sky hemispheric albedo asymmetry

A striking feature of the Earth system is that the Northern and Southern Hemispheres reflect identical amounts of sunlight. This hemispheric albedo symmetry comprises two asymmetries: The Northern Hemisphere is more reflective in clear skies, whereas the Southern Hemisphere is cloudier. Here we show that the hemispheric reflection contrast from differences in continental coverage is offset by greater reflection from the Antarctic than the Arctic, allowing the net clear-sky asymmetry to be dominated by aerosol. Climate model simulations suggest that historical anthropogenic aerosol emissions drove a large increase in the clear-sky asymmetry that would reverse in future low-emission scenarios. High-emission scenarios also show decreasing asymmetry, instead driven by declines in Northern Hemisphere ice and snow cover. Strong clear-sky hemispheric albedo asymmetry is therefore a transient feature of Earth’s climate. If all-sky symmetry is maintained, compensating cloud changes would have uncertain but important implications for Earth’s energy balance and hydrological cycle.

Quench-drive spectroscopy of cuprates.

Cuprates are d-wave superconductors which exhibit a rich phase diagram: they are characterized by superconducting fluctuations even above the critical temperature, and thermal disorder can reduce or suppress the phase coherence. However, photoexcitation can have the opposite effect: recent experiments have shown an increasing phase coherence in optimally doped BSCCO with mid-infrared driving. Time-resolved terahertz spectroscopies are powerful techniques to excite and probe the non-equilibrium states of superconductors, directly addressing collective modes, such as amplitude (Higgs) oscillations. In this work, we calculate the full time evolution of the current generated by a cuprate with a quench-drive spectroscopy setup. Analyzing the response in Fourier space with respect to both the real time and the quench-drive delay time, we look for the signature of a transient modulation of higher harmonics, as well as the Higgs mode, in order to characterize the ground state phase. In particular, this approach can provide a smoking gun for induced or increased phase coherence when applied to the pseudogap phase. These results can pave the way for future experimental schemes to characterize and study superconductors alongside incoherent phases and phase transitions, including induced and transient superconductivity.

Transient electromagnetically induced transparency spectroscopy of 87Rb atoms in buffer gas

We study the transient response dynamics of 87Rb atomic vapor buffered in 8 torr Ne gas through an electromagnetically induced transparency configured in Λ-scheme. Experimentally, the temporal transmission spectra versus probe detuning by switching on and off the coupling one show complex structures. The transmitted probe light intensity drops to a minimum value when the coupling light turns off, showing a strong absorption. Even at the moment of turning on the coupling light at a subsequent delayed time, the atomic medium shows a fast transient response. To account for the transient switching feature, in the time-dependent optical Bloch equation, we must take the transverse relaxation dephasing process of atomic vapor into account, as well as the fluorescence relaxation along with the optical absorption. This work supplies a technique to quantify the transverse relaxation time scale and to sensitively monitor its variation along the environment by observing the transient dynamics of coherent medium, which is helpful in characterizing the coherent feature of the atomic medium.

Efficacy Analysis of Corneal Crosslinking (CXL): Comparing Epi-on and Epi-off Procedures

Purpose: To analyze the factors influencing the corneal crosslinking (CXL) efficacy and comparison of epi-on and epi-off procedures.
 Study Design: modeling the efficacy of epi-off and epi-on CXL.
 Place and Duration of Study: New Taipei City, Taiwan, between November, 2021 and December, 2021.
 Methodology: Solving the rate equations for the CXL efficacy which includes the roles of concentration of the photosensitizer, riboflavin (RF), RF depletion effects, dynamic of light intensity, and the non-uniform distribution of RF in the stroma, or the diffusion depth of RF. Both steady-state and transient state features are explored for the efficacy, crosslink depth (CD) and the effects of epithelium layer for the epi-on situation.
 Results: The steady-state efficacy is proportional to the square-root of [RF-concentration] /[light-intensity], The competing factors of reduced RF, F(z), and reduced light intensity in the stroma determine the relative efficacy of epi-on and epi-off. For example, for F(z)<0.5, epi-on is more efficient than epi-off. In contrast, in the transient state (with efficacy <0.6), the efficacy is proportional to the light dose, and therefore epi-on is always less efficient than epi-off. The crosslink depth (CD) has an inverse trend, such that higher light intensity and lower RF concentration lead to deeper CD. The analytic formulas are developed under simplified conditions, in which numerical simulation is required for non-uniform distribution, and when RF depletion are included. Various strategies for improved steady-state efficacy efficacy and crosslink depth for epi-on CXL are explored including the use of higher RF concentration and lower light intensity; enhancing the RF diffusion by an electrode device, or diffusion enhancing medicine. The analytic formulas are compared with measured data.
 Conclusion: For the steady-state epi-on is more efficient than epi-off, when the RF reduction factor is less than the light intensity gain factor. In contrast, in the transient state (with efficacy <0.6), the efficacy is proportional to the light dose, and therefore epi-on is always less efficient than epi-off.