Transient Acceleration Research Articles

Design of Artificial Neuro-fuzzy Based Methodology for Six Component Force Balance

A blunt cone model of 600 apex angle and 150 flare with internally mountable accelerometer balance has been considered for the present investigation on six component force balance. The finite element method (FEM) has been incorporated at predetermined angles of the applied force to obtain multiple accelerations in three spatial directions so as to replicate a six component force balance system. A novel intelligent soft computing technique, Artificial Neuro-Fuzzy Inference System (ANFIS) has been implemented for accurate prediction of the magnitude and trend of aerodynamic forces and moments from the transient acceleration history. The same method is also used to validate the universal approximation nature of the impulse force by accurate prediction of the hat and ramp forces from the training of the impulse forces. Furthermore, a training algorithm is deduced so as to predict the force and moment magnitude for the three and single component force balance from the six component training data. Henceforth, novelty of this study involves in deduction of a universal training method and successful implementation of it to predict short duration transient force and moment histories.

Exosomes mediate the acquisition of the disease phenotypes by cells with normal genome in tuberous sclerosis complex.

Functions of extracellular vesicles including exosomes in the pathogenesis of tuberous sclerosis complex (TSC) have not yet been studied. We report that the extracellular vesicles such as exosomes derived from tuberous sclerosis 1 (Tsc1)-null cells transform phenotypes of neighboring wild-type cells in vivo in such manner that they become functionally similar to Tsc1-null cells. The loss of Tsc1 in the mouse neural tube increases the number of the wild-type neuronal progenitors, which is followed by the precocious and transient acceleration of neuronal differentiation of these cells. The mechanisms regulating these changes involve the exosomal delivery of exosomal shuttle Notch1 and Rheb esRNA and component of γ-secretase complex presenilin 1 from Tsc1-null cells to wild-type cells leading to the activation of Notch and Rheb signaling in the recipient cells. The exosome-mediated mechanisms may also operate in the cells of angiomyolipoma (AML), which develops as a result of mutations in TSC1/TSC2 genes in TSC patients, because we observed the reactivation of mammalian target of rapamycin and Notch pathways, driven by the delivery of Rheb and Notch1 esRNA, in AML cells depleted of Rheb that were treated with the exosomes purified from AML cells with the constitutively high Rheb levels.

Biomechanical analysis of spasticity treatment in patients with multiple sclerosis.

New metrics for clinical spasticity are needed to assess motor performance, since scales such as the Ashworth and Tardieu are unreliable. Here, we assessed outcomes of baclofen treatment in patients with multiple sclerosis (MS) using biomechanical analysis of voluntary movements. Patients with MS and symptomatic limb spasticity were recruited for a pre-post baclofen titration study, along with age-matched healthy controls. Oral baclofen was titrated to optimize spasticity symptoms in all MS cases over 4 weeks. Clinical assessments included the Modified Ashworth Scale (MAS), Tardieu Scale (TS); elbow kinematics were measured via the Transient Acceleration Measurement Interface (TAMI); performance was measured as the score at 4 weeks minus the baseline score in all measures. Movement proficiency within TAMI was quantified through a scale-free smoothness measure, according to the regional excursion deviation (RED) from a constant-velocity approximant. Twelve patients with MS [age: 47.8 ± 9.8 years; women: 4; disease duration: 20 ± 10 years; disease-modifying therapy use: 7; Expanded Disability Status Scale (EDSS): 6.8 ± 1.4] and eight age-matched healthy controls were evaluated concurrently (mean age: 49.5 ± 13.1 years; women = 3). In MS cases, no significant improvement in arm spasticity was observed with main effects: MAS: -41.6 ± 72.6 (p = 0.09); EDSS: -1.6 ± 10.4% (p = 0.49); and TS: -8.3 ± 2.1% (p = 0.32), -24.9 ± 63.6% (p = 0.42), and -30.7 ± 79.9% (p = 0.06), at slow, moderate, and fast speeds, respectively. However, voluntary motion smoothness, as measured by TAMI: RED, decreased significantly: 0.62 ± 0.08 versus 0.54 ± 0.09, p < 0.001, indicating significant increase in movement smoothness post treatment. A simple biomechanical analysis of voluntary movements revealed a significant reduction of spasticity after 30 days of baclofen therapy in patients with MS that was not detected by clinical assessments.

Optogenetics for suppression of cardiac electrical activity in human and rat cardiomyocyte cultures.

Optogenetics has revolutionized neuroscience by enabling precise control of neural excitation. The development of similar optogenetics strategies in the heart is just emerging and mainly focused on pacing with light activation of channelrhodopsin-2. Here, we aimed to develop an optogenetic approach to suppress local cardiac electrical activity by using engineered cell-grafts (HEK293-cells) transfected to express the light-sensitive hyperpolarizing proton-pump archaerhodopsin-3 (Arch3). To evaluate the ability of the engineered cells to couple and modulate the electrical activity of cardiomyocytes, we co-cultured the Arch3-HEK293 cells with neonatal rat cardiomyocytes (NRCMs) or human embryonic stem cells derived cardiomyocytes (hESC-CMs). The co-cultures' conduction and chronotropic properties were evaluated prior, during, and following application of focused monochromatic light (590nm) using a multielectrode array mapping system. Application of focused illumination completely silenced electrical activity at the illuminated area in all NRCM co-cultures, leading to development of localized functional conduction blocks. Similarly, illumination significantly slowed spontaneous beating-rate in the hESCs-CMs co-cultures (from [Formula: see text] to [Formula: see text], [Formula: see text]). Interestingly, a transient acceleration in beating-rate was noted immediately postillumination. In conclusion, a combined gene and cell therapy approach, using light-sensitive hyperpolarizing proteins, could be used to modulate conduction and automaticity in cardiomyocyte cultures, opening the way for future optogenetic treatments for cardiac tachyarrhythmias.

Greenland supraglacial lake drainages triggered by hydrologically induced basal slip.

Water-driven fracture propagation beneath supraglacial lakes rapidly transports large volumes of surface meltwater to the base of the Greenland Ice Sheet. These drainage events drive transient ice-sheet acceleration and establish conduits for additional surface-to-bed meltwater transport for the remainder of the melt season. Although it is well established that cracks must remain water-filled to propagate to the bed, the precise mechanisms that initiate hydro-fracture events beneath lakes are unknown. Here we show that, for a lake on the western Greenland Ice Sheet, drainage events are preceded by a 6-12 hour period of ice-sheet uplift and/or enhanced basal slip. Our observations from a dense Global Positioning System (GPS) network allow us to determine the distribution of meltwater at the ice-sheet bed before, during, and after three rapid drainages in 2011-2013, each of which generates tensile stresses that promote hydro-fracture beneath the lake. We hypothesize that these precursors are associated with the introduction of meltwater to the bed through neighbouring moulin systems (vertical conduits connecting the surface and base of the ice sheet). Our results imply that as lakes form in less crevassed, interior regions of the ice sheet, where water at the bed is currently less pervasive, the creation of new surface-to-bed conduits caused by lake-draining hydro-fractures may be limited.

Suspension of solid particles in a density stratified fluid

Widespread implications of settling particles in stratified fluids call for accurate assessment of a suspension of particles at pycnoclines. We perform direct numerical simulations of the motion of particles based on a distributed Lagrange multiplier technique to quantify the effect of density stratification on the settling velocity and microstructure of a suspension of rigid particles. The flow field around particles is fully resolved, and a statistically steady-state condition is obtained after a transient acceleration of particles. Based on the simulation results, we propose a correlation for the mean settling velocity of the suspension as a function of solid volume fraction and background density gradient in a fluid column. The correlation follows a power-law dependence on the solid volume fraction of the suspension. The effect of the stratification on the microstructure of the suspension is also investigated by direct comparison of the pair correlation function between homogeneous and stratified fluids. It is shown that the presence of the background density gradient enhances the formation of horizontally aligned clusters in the fluid column.

Region‐Specific Spatial Cross‐Correlation Model for Stochastic Simulation of Regionalized Ground‐Motion Time Histories

Stochastic simulation of spatially distributed ground-motion time histor- ies is important for performance-based earthquake design of geographically distrib- uted systems. In this study, we develop a novel technique to stochastically simulate regionalized ground-motion time histories by taking account of the influence of regional site conditions. For this purpose, a transient acceleration time history is char- acterized by wavelet-packet parameters proposed by Yamamoto and Baker (2013). The wavelet-packet parameters can fully characterize ground-motion time histories in terms of energy content, time-frequency-domain characteristics and time-frequency nonstationarity. This study further investigates the spatial cross correlations of wavelet- packet parameters based on geostatistical analysis of 1500 regionalized ground-motion data from eight well-recorded earthquakes in California, Mexico, Japan, and Taiwan. The linear model of coregionalization (LMC) is used to develop a permissible spatial cross-correlation model for each parameter group. The geostatistical analysis of ground- motion data from different regions reveals significant dependence of the LMC structure on regional site conditions, which can be characterized by the correlation range of VS30 in each region. In general, the spatial correlation and cross correlation of wavelet- packet parameters are stronger if the site condition is more homogeneous. The pro- posed region-specific correlation model improves stochastic simulation of spatially correlated ground motions, as is demonstrated in illustrative examples in this article. The developed method has great potential to be used in computationally based seismic analysis and loss estimation in a regional scale.

Detecting and understanding the accelerated sea level rise along the east coast of the United States during recent decades

AbstractA “hot spot” of accelerated sea level rise has recently been detected between Cape Hatteras and Cape Cod. The acceleration in the long‐term trend, however, is difficult to isolate from transient acceleration due to variability, particularly the ∼60 year cycle associated with the Atlantic Multidecadal Oscillation (AMO). The Empirical Mode Decomposition (EMD) and Ensemble EMD (EEMD) methods have been used to isolate oscillations and provide robust acceleration estimates for the trend. Yet the reliability of these methods in detecting accelerated sea level rise, particularly given the limited lengths of tide gauge records, has not been fully tested. Here, the EMD and EEMD methods are applied to both tide gauge observations and synthetic sea level time series constructed as a sum of oscillations extracted from tide gauge records and trends with prescribed acceleration rates. The successively truncated synthetic and observed data are analyzed with (E)EMD, and estimates of the acceleration error based on the record length are produced. Generally, EEMD provides more stable acceleration estimates than EMD, and the error decreases as the record length increases, although not monotonically. Records exceeding two multidecadal oscillation periods in length provide superior estimates over shorter records. In addition, the AMO may have contributed significantly to the rapid acceleration detected in the hot spot during recent decades. These findings have important implications for improved detection of regional sea level acceleration in a warming climate.

An intraplate slow earthquake observed by a dense GPS network in Hokkaido, northernmost Japan

AbstractAn intraplate slow earthquake was detected in northernmost Hokkaido, Japan, by a dense network of the global navigation satellite system. Transient abnormal acceleration of &amp;lt;12 mm was observed during the period 2012 July to 2013 January (∼5.5 months) at several sites. The spatial displacement distribution suggests that a localized tectonic event caused localized deformation. Estimated fault parameter indicates very shallow-dip reverse faulting in the uppermost crust, with a total seismic moment of 1.75E + 17 N m (Mw 5.4). This fault geometry is probably consistent with detachment structure indicated by geological studies. A simultaneous earthquake swarm with the maximum magnitude M4.1 suggests a possibility that the slow slip triggered the seismic activity for unknown reasons. This slow earthquake is slower than its moment would indicate, with a duration–magnitude scaling relationship unlike either regular earthquakes or subduction slow slip events. This result indicates that even if the area is under different physical property from subduction zones, slow earthquake can occur by some causes. Slow earthquakes exist in remote regions away from subduction zones and might play an important role in strain release and tectonic activity.

Analysis of transient amplification for a torsional system passing through resonance

The classical problem of vibration amplification of a linear torsional oscillator excited by an instantaneous sinusoidal torque is re-examined with focus on the development of new analytical solutions of the transient envelopes. First, a new analytical method in the instantaneous frequency (or speed) domain is proposed to directly find the closed-form solutions of transient displacement, velocity, and acceleration envelopes for passage through resonance during the run-up or run-down process. The proposed closed-form solutions are then successfully verified by comparing them with numerical predictions and limited analytical solutions as available in prior literature. Second, improved analytical approximations of maximum amplification and corresponding peak frequency are found, which are also verified by comparing them with prior analytical or empirical formulas. In addition, applicability of the proposed analytical solution is clarified, and their error bounds are identified. Finally, the utility of analytical solutions and approximations is demonstrated by application to the start-up process of a multi-degree-of-freedom vehicle driveline system.

In-Plane Mode Dynamics of Capillary Self-Alignment

We present an experimental study of the complete in-plane dynamics of capillary self-alignment. The two translational (shift) and single rotational (twist) in-plane modes of square millimetric transparent dies bridged to shape-matching receptor sites through a liquid meniscus were selectively excited by preset initial offsets. The entire self-alignment dynamics was simultaneously monitored over the three in-plane degrees of freedom by high-speed optical tracking of the alignment trajectories. The dynamics of the twist mode is shown to qualitatively follow the sequence of dynamic regimes also observed for the shift modes, consisting of initial transient wetting, acceleration toward, and underdamped harmonic oscillations around the equilibrium position. Systematic analysis of alignment trajectories for individually as well as simultaneously excited modes shows that, in the absence of twist offset, the dynamics of the degenerate shift modes are mutually independent. In the presence of twist offset, the three modes conversely evidence coupled dynamics, which is attributed to a synchronization mechanism affected by the wetting of the bounding surfaces. The experimental results, justified by energetic, wetting, and dynamic arguments, provide substantial benchmarks for understanding the full dynamics of the process.

Calcium-mediated pore expansion and cell death following nanoelectroporation

Opening of long-lived pores in the cell membrane is the principal primary effect of intense, nanosecond pulsed electric field (nsPEF). Here we demonstrate that the evolution of pores, cell survival, the time and the mode of cell death (necrotic or apoptotic) are determined by the level of external Ca2+ after nsPEF. We also introduce a novel, minimally disruptive technique for nsEP exposure of adherent cells on indium tin oxide (ITO)-coated glass coverslips, which does not require cell detachment and enables fast exchanges of bath media. Increasing the Ca2+ level from the nominal 2–5μM to 2mM for the first 60–90min after permeabilization by 300-nsPEF increased the early (necrotic) death in U937, CHO, and BPAE cells. With nominal Ca2+, the inhibition of osmotic swelling rescued cells from the early necrosis and increased caspase 3/7 activation later on. However, the inhibition of swelling had a modest or no protective effect with 2mM Ca2+ in the medium. With the nominal Ca2+, most cells displayed gradual increase in YO-PRO-1 and propidium (Pr) uptake. With 2mM Ca2+, the initially lower Pr uptake was eventually replaced by a massive and abrupt Pr entry (necrotic death). It was accompanied by a transient acceleration of the growth of membrane blebs due to the increase of the intracellular osmotic pressure. We conclude that the high-Ca2+-dependent necrotic death in nsPEF-treated cells is effected by a delayed, sudden, and osmotically-independent pore expansion (or de novo formation of larger pores), but not by the membrane rupture.

Analysis and Collision Simulation Research of the Latest Underrun Protective Device

For a truck rear guard device connections is weak, the height from the ground does not meet the national standard. Used CATIA to design the latest kind of swinging truck rear underrun protector. The size of the latest protective frame meet the requirements of Chinese standard GB1567.2-2001. Used the finite element simulation of analysis software LS-DYNA, make the simulation experiment of rear end collision between a car and the truck. Analysis of the curve about the transient dynamic response, displacement, velocity and acceleration of protective frame in the process of collision, Clearly show the deformation process in the rear-end collision process of the protection frame. it proved the effectiveness of the protective frame. Analysis and collision simulation research of the latest underrun protective device.

Steady-Periodic Acceleration Effects on the Performance of a Loop Heat Pipe

The objective of this research is to experimentally investigate the transient operating characteristics of a titanium-water loop heat pipe subjected to a combined steady-state evaporator input heat rate and a steady-periodic acceleration field. For this experimental investigation, a steady-periodic acceleration field, in the form of a sine wave, was generated using a centrifuge table. Radial acceleration peak-to-peak values and frequency of the sine wave were defined prior to conducting each experimental run and ranged from and , respectively. Evaporator input heat rate and condenser cold plate coolant temperature were varied, and , respectively. In some cases, acceleration driven forces complimented the thermodynamic forces, improving loop heat pipe dynamical performance. However, the converse was also true in that transient acceleration driven forces also appeared to counter thermodynamic forces or excite natural frequencies of the loop heat pipe. This resulted in immediate failure of the loop heat pipe to operate, delayed failure, or in some cases, the loop heat pipe operated in a stable manner but in a degraded condition.

A class of transient acceleration models consistent with Big Bang cosmology

Is it possible that the current cosmic accelerating expansion will turn into a decelerating one? Can this transition be realized by some viable theoretical model that is consistent with the standard Big Bang cosmology? We study a class of phenomenological models with a transient acceleration, based on a dynamical dark energy with a very general form of equation of state pde = βρde − βρdem. It mimics the cosmological constant ρde → const for a small scale factor a, and behaves as a barotropic gas with ρde → a−3(α+1) with α ≥ 0 for large a. The cosmic evolution of four models in the class has been examined in detail, and all yield a smooth transient acceleration. Depending on the specific model, the future universe may be dominated by either dark energy or by matter. In two models, the dynamical dark energy can be explicitly realized by a scalar field with an analytical potential V(φ). Moreover, a statistical analysis shows that the models can be as robust as ΛCDM in confronting the observational data of Type Ia supernovae, cosmic microwave background (CMB) and baryon acoustic oscillation. As improvements over previous studies, our models overcome the problem of over-abundance of dark energy during early eras, and satisfy the constraints on dark energy from WMAP observations of CMB.

Inflection point quintessence

We examine models in which the accelerated expansion of the Universe is driven by a scalar field rolling near an inflection point in the potential. For the simplest such models, in which the potential is of the form $V(\ensuremath{\phi})={V}_{0}+{V}_{3}(\ensuremath{\phi}\ensuremath{-}{\ensuremath{\phi}}_{0}{)}^{3}$, the scalar field can either evolve toward $\ensuremath{\phi}={\ensuremath{\phi}}_{0}$ at late times, yielding an asymptotic de Sitter expansion, or it can transition through the inflection point, producing a transient period of acceleration. We determine the parameter ranges which produce each of these two possibilities and also map out the region in parameter space for which the equation of state of the scalar field is close to $\ensuremath{-}1$ at all times up to the present, mimicking $\ensuremath{\Lambda}\mathrm{CDM}$. We show that the latter can be consistent with either eternal or transient acceleration. More complicated inflection point models are also investigated.

Super-Acceleration in the Flaring Crab Nebula

The Crab Nebula continues to surprise us. The Crab system (energized by a very powerful pulsar at the center of the Supernova Remnant SN1054) is known to be a very efficient particle “accelerator” which can reach PeV energies. Today, new surprising data concerning the gamma-ray flares produced by the Crab Nebula challenge models of particle acceleration. The total energy flux from the Crab has been considered for many decades substantially stable at X-ray and gamma-ray energies. However, this paradigm was shattered by the AGILE discovery and Fermi confirmation in September 2010 of transient gamma-ray emission from the Crab. Indeed, we can state that four major flaring gamma-ray episodes have been detected by AGILE and Fermi during the period mid-2007/2012. During these events, transient particle acceleration occurs in a regime which apparently violates the MHD conditions and synchrotron cooling constraints. This fact justifies calling “super-acceleration” the mechanism which produces the “flaring Crab phenomenon”. Radiation between 50 MeV and a few GeV is emitted with a quite hard spectrum within a short timescale (hours-days), with no obvious relation with simultaneous optical and X-ray emissions in the inner Nebula. “Super-acceleration” implies overcoming synchrotron cooling by strong (and “parallel”) electric fields most likely produced by magnetic field reconnection within the pulsar wind outflow. This acceleration appears to be very efficient and, remarkably, limited by radiation reaction. It is not clear at the moment where in the Nebula this phenomenon occurs. An intense observational program is now focused on the Crab Nebula to resolve its most challenging mystery.

The Transient Acceleration from Time-Dependent Interacting Dark Energy Models

The transient acceleration which the current cosmic acceleration is not eternal is possible by introducing the interaction between dark matter and dark energy. If the energy transfer is from dark energy to dark matter, then it is possible to realize the transient acceleration. We study the possibility of transient acceleration by considering two time-dependent phenomenological interaction forms so that the energy transfer increases as the universe evolves. Starting from a simple and extending to a more complicated ansatz, we obtain analytical expressions for the evolutions of the deceleration and the various energy density parameters. We find the ranges of the parameters in the models for a transient acceleration.

Early Enriched Environment Exposure Protects Spatial Memory and Accelerates Amyloid Plaque Formation in APPSwe/PS1L166P Mice

Enriched environment exposure improves several aspects of cognitive performance in Alzheimer’s disease patients and in animal models and, although the role of amyloid plaques is questionable, several studies also assessed their response to enriched environment, with contrasting results. Here we report that rearing APPSwe/PS1L166P mice in an enriched environment since birth rescued the spatial memory impairment otherwise present at 6 months of age. At the same time, the exposure to the enriched environment caused a transient acceleration of plaque formation, while there was no effect on intracellular staining with the 6E10 antibody, which recognizes β-amyloid, full length amyloid precursor protein and its C-terminal fragments. The anticipation of plaque formation required exposure during early development, suggesting an action within critical periods for circuits formation. On the other hand, chronic neuronal activity suppression by tetrodotoxin decreased the number of plaques without affecting intracellular amyloid. These results indicate that enriched environment exposure since early life has a protective effect on cognitive deterioration although transiently accelerates amyloid deposition. In addition, the effects of the enriched environment might be due to increased neuronal activity, because plaques were reduced by suppression of electrical signaling by tetrodotoxin.

Virus-induced CD8 + T cells accelerate the onset of experimental autoimmune encephalomyelitis: Implications for how viral infections might trigger multiple sclerosis exacerbations

Viral infections can exacerbate multiple sclerosis (MS) through poorly defined mechanisms. We developed an experimental system whereby infection with an asymptomatic neurotropic alphavirus caused a transient acceleration of experimental autoimmune encephalomyelitis (EAE) without altering the expansion or differentiation of autoreactive CD4+ T cells. Instead, this effect on the clinical course of EAE depended on CD8+ T cells that neither participate in viral clearance nor induce neuropathology in infected mice without EAE. Our system should be useful to further unravel how certain viral infections trigger MS exacerbations and to understand how CD8+ T cells can exert pathogenic effects within active demyelinating lesions.