Use Of Fluctuations Research Articles

Assessing the mechanical properties of molecular materials from atomic simulation

<abstract> <p>We review approaches to deriving mechanical properties from atomic simulations with a special emphasis on temperature-dependent characterization of polymer materials. The complex molecular network of such materials implies only partial, rather local ordering stemming from the entanglement of molecular moieties or covalent bonding of network nodes, whereas the polymer strands between the nodes may undergo nm-scale reorganization during thermal fluctuations. This not only leads to a strong temperature-dependence of the elastic moduli, but also gives rise to visco-elastic behavior that complicates characterization from molecular dynamics simulations. Indeed, tensile-testing approaches need rigorous evaluation of strain-rate dependences, provoking significant computational demands. Likewise, the use of fluctuations observed from unbiased constant-temperature, constant-pressure molecular dynamics simulation is not straight-forward. However, we suggest pre-processing from Fourier-filtering prior to taking Boltzmann-statistics to discriminate elastic-type vibrations of the simulation models for suitable application of linear-response theory.</p> </abstract>

Use of fluctuation on warning sound for approaching electric vehicle

Use of fluctuation on warning sound for approaching electric vehicle

δ30Si and δ18O of multiple silica phases in chert: Implications for δ30Siseawater of Darriwilian seawater and sea surface temperatures

A promising quantitative method is the use of fluctuations of seawater silicon isotope compositions (δ30Siseawater) to estimate the silicon cycle and silicon isotopic budgets of both the marine and terrestrial systems in a pre-diatom ocean. However, a thorough global calibration of Phanerozoic δ30Siseawater, which is linked to continental tectonics and silicate weathering, has not been established. The silicon and oxygen isotope compositions of Darriwilian cherts (δ30Sichert and δ18Ochert, respectively) have considerable potential as proxies for δ30Siseawater and sea surface temperatures (SSTs), which can expand our understanding of the influence of continental tectonics and temperature changes on the Great Ordovician Biodiversification Event (GOBE). In this study, primary depositional and early diagenetic cherts were sampled from bedded chert, lump-shaped chert, nodular chert, and banded chert from five Darriwilian outcrops in the Kalpin and Yijianfang areas of the Tarim Basin in China. The preservation conditions of these cherts were assessed based on petrographic criteria such as the absence of calcite veins and fractures under macroscopic observation and the absence of aggregate chalcedony (CHA), microquartz (MQ), and cryptocrystalline quartz (MQC) using optical microscopy and scanning electronic microscopy (SEM). The SSTs and δ30Siseawater of Darriwilian seawater were reconstructed using the δ18Ochert and δ30Sichert of well-preserved cherts. Our results show that the SSTs were approximately 32 ± 5 °C in the early Darriwilian and approximately 30 ± 5 °C in the late Darriwilian. The δ30Siseawater was approximately +3.1‰ in the Kalpin and Yijianfang areas during the Darriwilian Stage. This is the first estimation of δ30Siseawater in the Darriwilian Stage, which provides a parameter for the global calibration of the δ30Siseawater of the pre-diatom ocean in the Phanerozoic Eon and validates the hypothesis that the pre-diatom ocean waters had higher δ30Si values than modern seawater.

Experimental measurement of binding energy, selectivity, and allostery using fluctuation theorems.

Thermodynamic bulk measurements of binding reactions rely on the validity of the law of mass action and the assumption of a dilute solution. Yet, important biological systems such as allosteric ligand-receptor binding, macromolecular crowding, or misfolded molecules may not follow these assumptions and may require a particular reaction model. Here we introduce a fluctuation theorem for ligand binding and an experimental approach using single-molecule force spectroscopy to determine binding energies, selectivity, and allostery of nucleic acids and peptides in a model-independent fashion. A similar approach could be used for proteins. This work extends the use of fluctuation theorems beyond unimolecular folding reactions, bridging the thermodynamics of small systems and the basic laws of chemical equilibrium.

Wonder of the 2,500-km Migration of Chestnut Tiger Butterflies (Parantica sita niphonica) Synchronicity, Precognition, and Use of Fluctuations

Wonder of the 2,500-km Migration of Chestnut Tiger Butterflies (Parantica sita niphonica) Synchronicity, Precognition, and Use of Fluctuations

Fluctuation enhanced gas sensing using UV irradiated Au-nanoparticle-decorated WO3-nanowire films

Abstract WO3 nanowires (WO3-NWs) decorated with gold nanoparticles (AuNPs) were utilized in resistive gas sensor devices to detect ethanol by use of fluctuation enhanced sensing (FES). The experimental system records both DC resistance and fluctuations of the sensing film. Our data verify that the sensitivity and selectivity of the gas sensor are improved by applying FES when the sensor is stimulated with a combination of UV light and heating. We conclude that UV light can produce improved gas sensing at low operating temperatures for the investigated AuNP-decorated WO3-NWs films.

An expanded Adaptive Neuro-Fuzzy Inference System (ANFIS) model based on AR and causality of multi-nation stock market volatility for TAIEX forecasting

For common people, stock investing is one popular way to manage their property. As Information Technology (IT) has risen in recent years, every security company has analyzed computer systems for their customers by developing their own investing. Taiwan is an island nation, and the economy relies on international trade deeply. The fluctuations of international stock markets will impact Taiwan stock market to a certain degree. Therefore, the use of fluctuations of other stock markets as forecasting factors for forecasting the Taiwan stock market is a practical way. In this paper, the proposed model uses the fluctuations of other national stock markets as forecasting factors, employs different discretization methods (Fuzzy C-means clustering, Subtractive Clustering and Cumulative Probability Distribution Approach) to discretize stock data, utilizes a fuzzy inference system to produce understandable rules, and applies an adaptive neural network to optimize model parameters to reach the best forecasting accuracy. To evaluate the forecasting performances, the proposed model is compared with two different models, Chen’s model and Yu’s model. The experimental results indicate that the proposed model is superior to the listing methods in terms of RMSE (root mean squared error). Key words: Data mining, Adaptive Neuro-Fuzzy Inference System (ANFIS), stock forecasting, subtractive clustering, cumulative probability distribution approach.

Update: Magnetic Field Sensors Could Help Halt Runway Crashes

Air-traffic control is a complex and high-stress business. Mistakes are not allowed. And it's not limited to directing planes for takeoff and landing - a job that's been memorably described as three-dimensional chess. It also includes keeping track of where planes are on the ground. According to safety watchdog Eurocontrol, in 2005 alone there were 600 occasions when people, cars, or planes crossed Europe's airport taxiways when they shouldn't have. In fact, the most deadly airline accident ever happened on the ground: in 1977, two 747 jumbo jets collided in the Canary Islands, killing 583 people. Most big airports have expensive ground-radar systems to keep track of where the hundreds of moving planes are on the sprawling tarmacs. But ground radar sometimes reflects off buildings and terminals, leaving small gaps in coverage. Smaller airports like the one in Thessaloniki, Greece, can't afford ground radar. Such blind spots on the ground at airports large and small have prompted European researchers to explore the use of fluctuations in the Earth's magnetic field to better pinpoint where planes are on busy taxiways. The results, researchers say, show that using US $150 sensors can fill in the blind spots.

Einstein y la complejidad

We study Einstein’s contributions to thermodynamics and statistical physics and their influence on some fields of physics which have led to current studies on complexity. We focus our attention on the use of fluctuations and entropy as a common framework for light and matter, whcich leds him to some of his fundamental contributions (phtoelectric effect, Brownian motion, specific heat of solids, stimulated light emission, Bose-Einstein condensation). We underline some aspects of Einstein’s research style: extrapolations, analogies, simplifications. We underline the relationship between light and matter as a common link of his researches in statistical physics.

Second-Order Homogenization Estimates Incorporating Field Fluctuations in Finite Elasticity

This paper presents the applicaition of a recently proposed "second-order"homogenization method (Ponte Castañeda 2002; J. Mech. Phys. Solids 50, 737) to the estimation of the effective behavior of hypetrelastic composites subjected to finite deformations. The key idea is to introduce an optimally chosen "linear comparison composite" which can then be used to convert available homogenization estimates bor linear composites directly into new estimates for the nonlinear hyperelastic composites. More precisely, the method makes use of "generalized" secant moduli that are intermediate between the standard "secant" and "tangent" moduli of the nonlinear phases, and that depend not only on the averages, or first moments of the fields in the phases, but also on the second moments of the field fluctuations, or phase covariance tensors. The use of the method is illustrated in the context of carbon-black-filled, and fiber-reinforced elastomers, and estimates analogous to the well-known Hashin=-Shtrikman and self-consistent estimates for linear-elastic composites are generated. The new estimates are compared with corresponding estimates using an earlier version of the method (Ponte Castañeda and Tiberio 2000; J Mech. Phys. Solids 48, 1389) neglecting the use of fluctuations, and the new results are found to be superior. In particular, the new estimates, unlike the earlier ones, are found to satisfy a rigorous bound, and to give more realistic predictions in the important limit of incompressible behavior.

Second-order estimates for the large-deformation response of particle-reinforced rubbers

This paper presents the application of a recently proposed ‘second-order’ homogenization method (J. Mech. Phys. Solids 50 (2002) 737–757) to the estimation of the effective behavior of hyperelastic composites subjected to finite deformations. The main feature of the method is the use of ‘generalized’ secant moduli that depend not only on the phases averages of the fields, but also on the phase covariance tensors. The use of the method is illustrated in the context of particle-, or fiber-reinforced elastomers and estimates analogous to the well-known Hashin–Shtrikman estimates for linear-elastic composites are generated. The new estimates improve on earlier estimates (J. Mech. Phys. Solids 48 (2000) 1389–1411) neglecting the use of fluctuations. In particular, the new estimates, unlike the earlier ones, are capable of recovering the exact incompressibility constraint when the matrix is also taken to be incompressible. To cite this article: O. Lopez-Pamies, P. Ponte Castañeda, C. R. Mecanique 331 (2003).

Deterministic and Stochastic Models Analyze the Robustness of Circadian Rhythms

The Drosophila circadian oscillator shows a robust property to environmental changes, internal variations, and fluctuations, where two interlocked negative feedback loops play a major role for oscillation [1, 2]. The PER-TIM loop is activated by dCLK-CYC and repressed by PER-TIM, whereas the dCLK loop is repressed by dCLK-CYC and activated by PER-TIM. Not only the molecular architecture, but also the parameters provide the robust property to the oscillator. However, the intrinsic mechanism of how the clock system acquires the robust oscillator remains to be elucidated. In this paper, we aim at understanding how critical the values of parameters is for producing the robust oscillator using a deterministic model, and how the probabilistic fluctuations involve the stable oscillation using a stochastic model [5]. In the deterministic model, we classified the various parameter combinations that produced the cycle of 24 hours. The robust properties depended on the values of the parameters. In the stochastic model, the proper use of fluctuation could make stable oscillations.

Effect of wind variability and variable air density on wave modeling

The impact of wind gustiness on the evolution of wave fields is analyzed by superimposing to the nominal wind speed a fluctuation whose amplitude is related to the local air‐sea temperature difference. The use of fluctuations represented by a Gaussian process, characterized by coherence in time, produces realistic time series whose characteristics are compatible with those obtained from previous studies and open sea measurements. For the sake of forcing a wave model two more representations of gustiness have been used, a simple alternate oscillation of fixed amplitude around the mean value and a Gaussian process without coherence in time. The introduction of gustiness leads to an evident average increase of the resulting wave heights, larger in the Atlantic Ocean than in the Mediterranean Sea. The randomness of the wind and, hence, to a more limited extent, of the wave fields implies the possible occurrence of wave heights much larger than expected in a nongusty field. Besides two 6 month hindcasts two ensemble exercises have been done by forcing two storms with 50 different random realizations of the input wind fields. On the basis of the statistics of the outputs the authors suggest for practical applications the use of two runs, without and with noncoherent gustiness. This will provide information on the statistics of the possible significant wave heights. The effect of a variable air density on wave generation has been explored by repeating the hindcasts using air density values estimated from the output of a meteorological model. It is found that in the North Atlantic Ocean this leads to an increase of the wave heights during the winter storms. The effects are more limited in the Mediterranean Sea.

The oxygen mass in SN 1987A: Making use of fluctuations in the (O I) lambda lambda 6300, 6364 profile

view Abstract Citations (31) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Oxygen Mass in SN 1987A: Making Use of Fluctuations in the [O i] lambda lambda 6300, 6364 Profile Chugai, Nikolai N. Abstract The "sawtooth" structure in the profile of the forbidden oxygen doublet [O I] λλ6300,6364 of SN 1987A is identified with the statistical fluctuations of the oxygen cloud number. A model of spherical clouds homogeneously distributed in the spherical volume v < 1700 km s^-1^ is assumed to describe the fluctuations. The observed mean square fluctuation can be reproduced if the number of clouds with characteristic velocity radius 60 km s^-1^ is ~2 x 10^3^ and the corresponding filling factor of the oxygen material f is ~0.1. The combination of this filling factor with the ratio M_o_ f^-1^ determined by the self-absorption effect results in the distance-independent estimate of the mass of clumpy oxygen in SN 1987A, M_o_~ 1.2-1.5 M_sun_. Publication: The Astrophysical Journal Pub Date: June 1994 DOI: 10.1086/187382 Bibcode: 1994ApJ...428L..17C Keywords: Line Spectra; Nuclear Fusion; Oxygen; Statistical Analysis; Stellar Evolution; Stellar Mass; Supernova 1987a; Astronomical Models; Taylor Instability; Astrophysics full text sources ADS | data products NED (2) SIMBAD (1)

Plasma corticosterone concentrations sensitively reflect levels of stimulus intensity in the rat

In Experiment 1 plasma concentrations of both corticosterone and adrenocorticotrophic hormone (ACTH) in rats were found to be greater than resting levels following 10 min, but not 2.5 min of exposure to an unfamiliar environment. In Experiment 2, rats exposed to 3 increasingly unfamiliar environments for 15 min showed 3 corresponding elevations in mean plasma corticosterone level. Rats receiving handling similar to that of the experimental animals showed plasma concentrations of corticosterone which were greater than those seen in undisturbed controls, but less than those observed in rats exposed to the least unfamiliar environment. Plasma concentrations of ACTH, however, did not accurately reflect treatment differences, indicating that either the 15 min time point was not optimal for detecting differences in circulating ACTH or, that unlike corticosterone, ACTH levels did not vary systematically in response to variations in the degree of environmental change experienced by the animals. Overall these results extend previous findings and provide additional support for the use of fluctuations in corticoid levels to measure changes in emotional state.

On a chaotic potential field in vitreous As 2Se 3

Some experimental results of the vitreous As 2Se 3 investigation (the photoconductivity spectrum of volume examples, the temperature dependence of the thermoelectric E.M.F., the shift of the optical edge under the temperature and pressure) may be explained by the use of fluctuations of an internal potential field. A hypothesis about the nature of chaotic potential field is proposed, which is based on a negligible magnitude of the gap deformation potential D g = D c − D v, where D c and D v are deformation potentials of band edges. By this hypothesis the fluctuations of the substance density in glass generate the chaotic potential field of magnitude about a half of the gap E g, while the gap magnitude fluctuates only slightly within some per cent of E g. It is shown that the displacement of the optical edge at As 2Se 3 amorphization may be a demonstration of the deformation nature of the chaotic potential field in this material.