Physical Perturbation Research Articles

Study on Performance Improvement of Sodium Acetate Trihydrate in Thermal Energy Storage System by Disturbance

Phase change materials (PCM) have been widely used in Thermal Energy Storage (TES) Systems. Considering the energy efficiency and the use of domestic hot water, the melting temperature range of phase change materials is considered to be optimal in the range of 50–60 °C. The most commonly used is sodium acetate trihydrate-based phase change material, which has the advantages of high latent heat and low price, but its high supercooling, low thermal conductivity, and phase separation affect its application. Therefore, this paper used sodium acetate trihydrate, disodium hydrogen phosphate dodecahydrate (DSP), and expanded graphite (EG) as raw materials to prepare composite phase change materials (CPCM) and used physical disturbance to further improve their properties. Firstly, their thermophysical properties were investigated by the step cooling curve method, differential scanning calorimetry (DSC), and x-ray diffraction (XRD). Secondly, in order to further evaluate the effect of physical disturbance on CPCM crystallization, further experimental studies were carried out by adjusting the rotor mass and rotational speed. The experimental results showed that when 1.5 wt.% DSP, 1.5 wt.% EG and physical perturbation work together, the CPCM phase transition temperature is 56.7 °C, and the latent heat is as high as 258.98 kJ/kg. At this time, its thermal conductivity increased from 0.62 w/m·k to 1.1625 w/m·k, and its subcooling degree decreased from above 20 °C to less than 0.5 °C, and no phase separation occurred. The greater the disturbance momentum (the greater the rotor mass or the greater the rotational speed), the shorter the induction time, which is more conducive to the crystallization of CPCM. The results obtained in this paper are instructive for the preparation of efficient new CPCMs.

DNA‐Based Nanoarchitectures as Eminent Vehicles for Smart Drug Delivery Systems

AbstractIn order to cure diseases efficiently with minimal side effects in sophisticated medicine, eminent drugs must be selectively delivered to diseased parts and allow to work only there. However, most of drug delivery systems (DDSs) previously proposed are not yet sufficiently selective and effective. This review covers recent developments of DDS in which DNA nanoarchitectures are employed as drug carriers. From short DNA fragments, a variety of complicated nanomedicines are fabricated to show unprecedentedly smart DDS functions. Encapsulated drugs are released mostly through controlled disassembly of DNA nanoarchitectures. Recent attention has been focusing to the use of appropriate stimuli to regulate each process in the DDS (delivery of drug, its release, and others) for further improved therapy. As intracellular stimuli for the regulation, various endogenous compounds (e.g., mRNA and enzymes), which are specifically abundant in target cells, are employed. Alternatively, physical perturbation (e.g., light irradiation) is provided from outside of tissues to control DDS. By combining multiple strategies in terms of new concepts, enormously smart DDSs are being achieved. Further progresses of these approaches in the future are guaranteed by complete freedom of molecular design in DNA nanoarchitectonics.

Scalar perturbation of gravitating double-kink solutions

In this letter, a two-dimensional (2D) gravity-scalar model is studied. This model supports interesting double-kink solutions, and the corresponding metric solutions can be derived analytically. Depending on a tunable parameter c, the metric can be symmetric or asymmetric. The Schrödinger-like equation for normal modes of the physical linear perturbation is derived. As c varies, the effective potential can have one or two singular barriers. If c is larger than a critical value, the zero mode will be normalizable, despite of the appearance of a strong repulsive singularity. The double-kink solution is always stable against linear perturbations.

No recovery of a large-scale anthropogenic sediment disturbance on the Pacific seafloor after 77 years at 6460 m depth

Habitat restoration and recolonisation of benthic communities after physical perturbation in the deep sea has long been thought to be extremely slow. This study reports on a serendipitous opportunity to survey the current state of a large mechanical disturbance of sediments at 6460 m in the Pacific Ocean. The impact was caused 77 years ago by the sinking of the USS Johnston. The surrounding debris field had little impact on the sedimentary habitat, other than in the provision of artificial hard substrates, while the troughs that formed as the ship impacted the seafloor and slid down the slope of the Philippine Trench were still completely void of animal tracks and burrows, or any observable epifauna, and in some areas subsurface stratification was still exposed at the surface. This suggests that mechanical perturbations of sediments in the deep Pacific may remain ecologically significant for, at the very least, 100 years.

Wind Speed Forecasts of a Mesoscale Ensemble for Large-Scale Wind Farms in Northern China: Downscaling Effect of Global Model Forecasts

To facilitate wind power integration for the electric power grid operated by the Inner Mongolia Electric Power Corporation—a major electric power grid in China—a high-resolution (of 2.7 km grid intervals) mesoscale ensemble prediction system was developed that forecasts winds for 130 wind farms in the Inner Mongolia Autonomous Region. The ensemble system contains 39 forecasting members that are divided into 3 groups; each group is composed of the NCAR (National Center for Atmospheric Research) real-time four-dimensional data assimilation and forecasting model (RTFDDA) with 13 physical perturbation members, but driven by the forecasts of the GFS (Global Forecast System), GEM (Global Environmental Multiscale Model), and GEOS (Goddard Earth Observing System), respectively. The hub-height wind predictions of these three sub-ensemble groups at selected wind turbines across the region were verified against the hub-height wind measurements. The forecast performance and variations with lead time, wind regimes, and diurnal and regional changes were analyzed. The results show that the GFS group outperformed the other two groups with respect to correlation coefficient and mean absolute error. The GFS group had the most accurate forecasts in ~59% of sites, while the GEOS and GEM groups only performed the best on 34% and 2% of occasions, respectively. The wind forecasts were most accurate for wind speeds ranging from 3 to 12 m/s, but with an overestimation for low speeds and an underestimation for high speeds. The GEOS-driven members obtained the least bias error among the three groups. All members performed rather accurately in daytime, but evidently overestimated the winds during nighttime. The GFS group possessed the fewest diurnal errors, and the bias of the GEM group grew significantly during nighttime. The wind speed forecast errors of all three ensemble members increased with the forecast lead time, with the average absolute error increasing by ~0.3 m/s per day during the first 72 h of forecasts.

Asymptotic Tracking Control on Profiling Posture of Sprayer Boom Systems With Position Uncertainties

An adaptive and robust backstepping method based on wavelet network approximation was proposed to solve the problems of load variation, unmodeled uncertainties, physical parameter perturbation and external disturbance in the sprayer boom profiling system. Firstly, a complete mathematical model for the boom system with uncertainties, unknowns and nonlinear terms was established and transformed into a state space form with strict feedback. Secondly, the designed wavelet primitive was used to construct the neural network, to approximate the virtual equivalent control part of the backstepping method under the condition that the optimal error is bounded. The adaptive update law was selected to estimate the unknown parameters. The robust compensation term was introduced to reduce the adverse effect of the composite interference on the system. The input command signal order requirement was reduced. Finally, suitable functions were constructed by means of the Lyapunov stability theory, to prove that the position tracking error of the closed-loop system asymptotically converges to the origin. The simulation results show that, the proposed control method can realize the rapid maneuver adjustment of the sprayer boom position and posture, and effectively enhance the robust stability and control accuracy of the boom system.

Abstract 14407: Effect of Initial Defibrillation on Chest Compression Artifact in the ECG

Introduction: Chest compressions (CCs) during CPR cause electrical artifacts in the ECG. Prior work has found that the severity of CC artifact, quantified by the signal-to-noise ratio (SNR), affects the diagnostic sensitivity of defibrillator algorithms designed to detect shockable rhythms during CCs. Whether SNR is altered by defibrillation is unknown. We therefore compared SNR before and after defibrillation shocks. Methods: We evaluated patients with out-of-hospital cardiac arrest who received at least 1 defibrillation shock, had subsequent ventricular fibrillation (VF), and had a calculable SNR before and after initial shock. We measured the CC artifact during VF before and after the initial shock (and up to 3 subsequent shocks) using CC amplitude and SNR. CC amplitude was defined as the median peak-to-peak voltage of the ECG during CCs. SNR was calculated as the log ratio of the power of the CC-free VF signal to the power of the estimated noise caused by CC artifact (Figure). Differences in medians before and after the first 4 shocks were evaluated using Wilcoxon signed-rank test with Bonferroni correction (alpha = 0.0125). Results: A total of 192 patients had a calculable SNR during VF before and after initial shock. Of these, the median CC amplitude decreased after the initial shock (0.93 vs. 0.75 mV, p<0.001), and SNR improved (-2.30 vs. -1.07 dB, p=0.004). In contrast to the initial shock, both CC amplitude and SNR did not differ significantly before and after shock 2 (n=107), shock 3 (n=54), or shock 4 (n=32). Conclusion: Measures of CC artifact in the ECG were greater before initial shock than afterward. This could potentially be due to changes in CC characteristics, variations in physical perturbation of the defibrillator electrodes, degradation of VF over time, or effects of tissue electroporation on paddle conductivity and noise. These findings may have implications for selection of decision thresholds in algorithms to detect shockable rhythm during CCs.

Analysis of finite-volume discrete adjoint fields for two-dimensional compressible Euler flows

This work deals with a number of questions related to the discrete and continuous adjoint fields associated with the compressible Euler equations and classical aerodynamic functions. The consistency of the discrete adjoint equations with the corresponding continuous adjoint partial differential equations is one of them. It has been established or at least discussed only for some numerical schemes and a contribution of this article is to give the adjoint consistency conditions for the 2-D Jameson-Schmidt-Turkel scheme in cell-centered finite-volume formulation. The consistency issue is also studied here from a new heuristic point of view by discretizing the continuous adjoint equation for the discrete flow and adjoint fields. Both points of view prove to provide useful information. Besides, it has been often noted that discrete or continuous inviscid lift and drag adjoint exhibit numerical divergence close to the wall and stagnation streamline for a wide range of subsonic and transonic flow conditions. This is analyzed here using the physical source term perturbation method introduced in reference [1]. With this point of view, the fourth physical source term of [1] appears to be the only one responsible for this behavior. It is also demonstrated that the numerical divergence of the adjoint variables corresponds to the response of the flow to the convected increment of stagnation pressure and diminution of entropy created at the source and the resulting change in lift and drag.

Sensing characteristics of grating assisted counterpropagating cladding modes in optical fibers.

In this paper, using full vector modal field analysis, we present physical parameter sensing, e.g., temperature, axial strain, bulk refractive index, and affinity sensing characteristics of counterpropagating cladding modes in optical fibers. Counterpropagating cladding modes (HEmn) are considered to be excited by resonant power coupling from the fundamental core mode using a suitably designed fiber Bragg grating (FBG). We show that for such couplings, the bandwidths of reflection spectra are much smaller than those obtained for conventional core mode reflecting FBGs. Next, we also show that the reflection bandwidth increases linearly with increasing grating strength, whereas it decreases exponentially with increasing grating length. The reflection spectra of such FBGs, as a function of different ambient physical perturbation parameters, are obtained, and then the grating sensitivity corresponding to those parameters is established. Interestingly, we have noticed that despite having the same evanescent field in the analyte region, unlike the long-period grating assisted co-propagating cladding modes (HEmn), the same cladding modes while propagating counter to the core mode are weakly sensitive to changes in the ambient refractive index. The reason behind this observation is discussed.

Kinetic partitioning of major and trace cations between clinopyroxene and phonotephritic melt under convective stirring conditions: New insights into clinopyroxene sector zoning and concentric zoning

Within subvolcanic plumbing systems, along volcanic conduits and post-eruptive emplacement, mineral textures and compositions are governed by complex kinetic (undercooling) and dynamic (convective) processes that deviate from theoretical models and equilibrium criteria. In this perspective, we have investigated the partitioning of major and trace cations between clinopyroxene and phonotephritic melt under convective stirring conditions at high degrees of undercooling (−ΔTnominal = 30–60 °C) and atmospheric pressure. We have integrated this novel data set with conventional static (no physical perturbation) clinopyroxene-melt compositions obtained under interface- and diffusion-controlled growth regimes. Results show that clinopyroxene growth kinetics and diffusion boundary layers caused by melt supersaturation are partly mitigated by the homogenizing effects of stirring. Because of continuous supply of fresh melt to the advancing crystal surface, the partitioning of major and trace cations is governed by local equilibrium effects, which are interpreted as the extension of equilibrium thermodynamic principles to non-equilibrium bulk systems. Major cations are incorporated into the clinopyroxene structure via the coupled substitution [M1Mg, TSi] ↔ [M1Ti, TAl] and in conformity with the thermodynamic mixing properties of CaMgSiO2, CaAl2SiO6, and CaTiAl2O6 components. The complementary relationship between lattice strain (ΔGstrain) and electrostatic (ΔGelectrostatic) energies of heterovalent substitutions is the most appropriate thermodynamic description for the accommodation of trace cations in the clinopyroxene lattice site (i.e., ΔGpartitioning = ΔGstrain + ΔGelectrostatic). The excess energy of partitioning ΔGpartitioning changes principally with Al in tetrahedral coordination and determines the type and number of charge-balanced and -imbalanced configurations taking place in the structural sites of clinopyroxene. An important outcome from dynamic stirring experiments is that superimposition of convective mass transfer on melt supersaturation phenomena causes the formation of Cr-rich concentric zones under closed system crystallization conditions. However, these Cr-rich zones do not correlate with enrichment in other compatible elements and depletion in incompatible elements, as would be expected in natural open systems characterized by input of more primitive magmas. While the convective transport acts to reduce the diffusive length scale of chemical species in the experimental melt, fresh Cr cations are more easily incorporated into the concentric zones due to crystal field effects. Together, our findings reveal that during magma ascent and emplacement, convective stirring may promote clinopyroxene crystallization and minimize kinetic effects on clinopyroxene zoning.

Pinnipeds and salmon farming: Threats, conflicts and challenges to co‐existence after 50 years of industrial growth and expansion

AbstractIn this review, we summarize and discuss the main interactions affecting salmon farming and pinniped populations worldwide. Out of seven pinnipeds commonly engaged in these interactions, only one, Eumetopias jubatus, is currently listed, as ‘Near Threatened’, by the IUCN. This scenario may change as the salmon farming industry is expanding to higher latitudes and climate change is threatening many pinniped populations. Pinniped attacks cause productive and economic losses, equivalent to 1%–12% of gross production costs, due to predation, induced escapes and implementing deterrent measures. Other potential negative effects on the industry remain unassessed: lower fish growth, immunosuppression, diseases transmission, damaging infrastructure and injuring farmworkers. Main direct threats to pinnipeds include intended and unintended killing, which lack independent quantifications and have generated a growing number of ethical, economic and socio‐political concerns, as well as trade regulations affecting the industry. Physical perturbation, pollution, nutrification and/or prey subsidies related to this industry may induce behavioural, trophic and social changes, as well as breeding and/or foraging habitat loss/change in impacted areas. Despite their relevance, the magnitude and consequences of these potential impacts have been poorly evaluated and documented, precluding us from assembling accurate assessments on most interactions. Hence, we recommend focusing further research on assessing the effects of these interactions and make a call for implementing and maintaining reliable and independent records of: (i) intended and unintended killings and (ii) demography of affected populations. Implementing an ecosystem approach may be key to reduce negative impacts of salmon farming on pinnipeds and coastal ecosystems.

Visualizing the Invisible: Advanced Optical Microscopy as a Tool to Measure Biomechanical Forces.

The importance of mechanical force in biology is evident across diverse length scales, ranging from tissue morphogenesis during embryo development to mechanotransduction across single adhesion proteins at the cell surface. Consequently, many force measurement techniques rely on optical microscopy to measure forces being applied by cells on their environment, to visualize specimen deformations due to external forces, or even to directly apply a physical perturbation to the sample via photoablation or optogenetic tools. Recent developments in advanced microscopy offer improved approaches to enhance spatiotemporal resolution, imaging depth, and sample viability. These advances can be coupled with already existing force measurement methods to improve sensitivity, duration and speed, amongst other parameters. However, gaining access to advanced microscopy instrumentation and the expertise necessary to extract meaningful insights from these techniques is an unavoidable hurdle. In this Live Cell Imaging special issue Review, we survey common microscopy-based force measurement techniques and examine how they can be bolstered by emerging microscopy methods. We further explore challenges related to the accompanying data analysis in biomechanical studies and discuss the various resources available to tackle the global issue of technology dissemination, an important avenue for biologists to gain access to pre-commercial instruments that can be leveraged for biomechanical studies.

Visual feedback of the tongue influences speech adaptation to a physical modification of the oral cavity.

Studies examining sensorimotor adaptation of speech to changing sensory conditions have demonstrated a central role for both auditory and somatosensory feedback in speech motor learning. The potential influence of visual feedback of oral articulators, which is not typically available during speech production but may nonetheless enhance oral motor control, remains poorly understood. The present study explores the influence of ultrasound visual feedback of the tongue on adaptation of speech production (focusing on the sound /s/) to a physical perturbation of the oral articulators (prosthesis altering the shape of the hard palate). Two visual feedback groups were tested that differed in the two-dimensional plane being imaged (coronal or sagittal) during practice producing /s/ words, along with a no-visual-feedback control group. Participants in the coronal condition were found to adapt their speech production across a broader range of acoustic spectral moments and syllable contexts than the no-feedback controls. In contrast, the sagittal group showed reduced adaptation compared to no-feedback controls. The results indicate that real-time visual feedback of the tongue is spontaneously integrated during speech motor adaptation, with effects that can enhance or interfere with oral motor learning depending on compatibility of the visual articulatory information with requirements of the speaking task.

Review of Helical Long-Period Fiber Gratings

In this paper, comprehensive remarks are given that focus on the main fabrications and wide applications of helical long-period fiber gratings (HLPGs). Firstly, the techniques of fabricating HLPGs by CO2 laser, hydrogen–oxygen flame heating, and arc discharge are summarized. Furthermore, the applications of HLPGs are investigated, i.e., orbital angular momentum (OAM) mode converters, all-fiber band-rejection filters, and sensors for measuring physical perturbation of torsion, strain, temperature, curvature, and surrounding refractive index (SRI). Furthermore, several long-period fiber gratings (LPFGs) of near-HLPG structures with periodic refractive index change along the azimuthal direction are introduced. Lastly, the prospects and key challenges for HLPGs are discussed.

Breaching the Delivery Barrier: Chemical and Physical Airway Epithelium Disruption Strategies for Enhancing Lentiviral-Mediated Gene Therapy

The lungs have evolved complex physical, biological and immunological defences to prevent foreign material from entering the airway epithelial cells. These mechanisms can also affect both viral and non-viral gene transfer agents, and significantly diminish the effectiveness of airway gene-addition therapies. One strategy to overcome the physical barrier properties of the airway is to transiently disturb the integrity of the epithelium prior to delivery of the gene transfer vector. In this study, chemical (lysophosphatidylcholine, LPC) and physical epithelium disruption using wire abrasion were compared for their ability to improve airway-based lentiviral (LV) vector mediated transduction and reporter gene expression in rats. When luciferase expression was assessed at 1-week post LV delivery, LPC airway conditioning significantly enhanced gene expression levels in rat lungs, while a long-term assessment in a separate cohort of rats at 12 months revealed that LPC conditioning did not improve gene expression longevity. In rats receiving physical perturbation to the trachea prior to gene delivery, significantly higher LacZ gene expression levels were found when compared to LPC-conditioned or LV-only control rats when evaluated 1-week post gene transfer. This proof-of-principle study has shown that airway epithelial disruption strategies based on physical perturbation substantially enhanced LV-mediated airway gene transfer in the trachea.

Maximum Spectral Flatness Control of a Manipulandum for Human Motor System Identification

System identification of a dynamic environment using a robotic device utilizes physical perturbations in the form of displacement or force. To obtain an accurate system model, physical perturbations must be informative, which can be characterized by their spectral properties. The process of generating physical perturbations by using a robotic device often leads to spectral property degradation in the high-frequency region due to the dynamics of robot motion control and discrete-time signal processing. Spectral flatness is a metric applicable to quantifying the fidelity of the robotic system and quality of physical perturbations on an external object. This letter introduces a new metric named Band-limited Spectral Flatness Gain (BLSFG) to evaluate the physical perturbation quality relative to the input reference over a frequency band of interest. Motion control of a manipulandum that generates pseudorandom position perturbations for human sensorimotor system identification is considered as a representative example. The closed-loop system dynamics of the position control is characterized and optimized based on the BLSFG. Results suggest that a certain underdamped closed-loop property is advantageous to improve the spectral flatness of a degraded continuous-time pseudorandom reference. A high BLSFG is achieved when the resonance frequency of the closed-loop system is close to the update frequency of the pseudorandom sequence.

CHARACTERIZING DRIVER TAKE-OVER ACCURACY: EFFECT OF AGE, SEX, STARTLE, AND SECONDARY TASK

The Acoustic Startling Pre-stimulus (ASPS, i.e. a loud sound preceding a physical perturbation was previously found to accelerate take-over actions in adults but not teens in autonomous vehicle scenarios. It is not clear if the ASPS also influences the accuracy of the take-over response across ages and sexes. Therefore the aims of this study are: to characterize take-over accuracy across age/experience and sex and to examine the effect of the ASPS and a secondary task on steering wheel alignment in autonomous vehicle take-over scenarios. Fourteen adult (7 males and 13 teenage (6 males drivers volunteered for this study. Participants were instructed to align a marker on the steering wheel with a marker on a lateral post as fast as they could, when a sled perturbation started. Two of the conditions included the ASPS. Two of the conditions involved mobile texting while the sled started moving. The angle between the steering wheel and the lateral post was used to quantify overshooting, undershooting, or correct alignment during steering. Results showed that adult female subjects reached correct alignment slightly more frequently than any other group, while male adult drivers decreased their alignment error after the first trial. Both female and male adult drivers had a reduced alignment angle when the first trial had an ASPS compared to when the first trial had no ASPS while teen drivers performed similarly with ASPS or without. This study showed that take-over accuracy and steering control are influenced by sex, age/experience, and a startle-based warning.

Functional Modulation of Receptor Proteins on Cellular Interface with Optogenetic System.

In multicellular organisms, living cells cooperate with each other to exert coordinated complex functions by responding to extracellular chemical or physical stimuli via proteins on the plasma membrane. Conventionally, chemical signal transduction or mechano-transduction has been investigated by chemical, genetic, or physical perturbation; however, these methods cannot manipulate biomolecular reactions at high spatiotemporal resolution. In contrast, recent advances in optogenetic perturbation approaches have succeeded in controlling signal transduction with external light. The methods have enabled spatiotemporal perturbation of the signaling, providing functional roles of the specific proteins. In this chapter, we summarize recent advances in the optogenetic tools that modulate the function of a receptor protein. While most optogenetic systems have been devised for controlling ion channel conductivities, the present review focuses on the other membrane proteins involved in chemical transduction or mechano-transduction. We describe the properties of natural or artificial photoreceptor proteins used in optogenetic systems. Then, we discuss the strategies for controlling the receptor protein functions by external light. Future prospects of optogenetic tool development are discussed.

Dance training improves the CNS\u2019s ability to utilize the redundant degrees of freedom of the whole body

Professional dancers demonstrate an amazing ability to control their balance. However, little is known about how they coordinate their body segments for such superior control. In this study, we investigated how dancers coordinate body segments when a physical perturbation is given to their body. A custom-made machine was used to provide a short pulling impulse at the waist in the anterior direction to ten dancers and ten non-dancers. We used Uncontrolled Manifold analysis to quantify the variability in the task-relevant space and task-irrelevant space within the multi-dimensional space made up of individual segments’ centers of mass with a velocity adjustment. The dancers demonstrated greater utilization of redundant degrees of freedom (DoFs) supported by the greater task-irrelevant variability as compared to non-dancers. These findings suggest that long-term specialized dance training can improve the central nervous system’s ability to utilize the redundant DoFs in the whole-body system.

Artificial modulation of cell width significantly affects the division time of Escherichia coli

Bacterial cells have characteristic spatial and temporal scales. For instance, Escherichia coli, the typical rod-shaped bacteria, always maintains a relatively constant cell width and cell division time. However, whether the external physical perturbation of cell width has an impact on cell division time remains largely unexplored. In this work, we developed two microchannel chips, namely straight channels and ‘necked’ channels, to precisely regulate the width of E. coli cells and to investigate the correlation between cell width and division time of the cells. Our results show that, in the straight channels, the wide cells divide much slower than narrow cells. In the ‘necked’ channels, the cell division is remarkably promoted compared to that in straight channels with the same width. Besides, fluorescence time-lapse microscopy imaging of FtsZ dynamics shows that the cell pre-constriction time is more sensitive to cell width perturbation than cell constriction time. Finally, we revealed a significant anticorrelation between the death rate and the division rate of cell populations with different widths. Our work provides new insights into the correlation between the geometrical property and division time of E. coli cells and sheds new light on the future study of spatial–temporal correlation in cell physiology.