Reciprocal Time Research Articles

Effect of Aquo‐glycolic Media and Added Anions on the Anodization of Zircaloy‐4 in Sulphamic Acid

Anodization of zircaloy‐4 in 0.1 M sulphamic acid has been carried out. Kinetics of anodic oxidation of zircaloy‐4 has been studied at a constant current density of 8 mA/cm2 and at room temperature. Thickness estimates were made from capacitance data. The plots of formation voltage vs. time, reciprocal capacitance vs. time, reciprocal capacitance vs. formation voltage and thickness vs. formation voltage were drawn and rate of formation, current efficiency and differential field were calculated. The addition of solvent (ethylene glycol) showed better kinetic results. For 25%, 50% and 75% aquo‐glycolic media, the dielectric constant values are low leading to a marked improvement in the kinetics. In 80% ethylene glycol, though the dielectric constant value of solution is less, the kinetics was slow which may be attributed to the fact that the electrolyte becomes highly non‐polar. Improvement in the kinetics of oxide film formation was observed by the addition of millimolar concentration of anions (CO32-, SO42-, PO43-). The presence of phosphate ions improved the kinetics of anodization to better extent.

Communications over the Best Singular Mode of a Reciprocal MIMO Channel

We consider two nodes equipped with multiple antennas that intend to communicate i.e. both of which transmit and receive data. We model the responses of the communication channels between these nodes as linear and reciprocal (time invariant or with very slow time variations). In practice, we exploit the closed loop conversation between these nodes and present an efficient algorithm allowing to adaptively identify the Best Singular Mode (BSM) of the channel. We consider two scenarios. In the first scenario, the initial communication link is established over the BSM assuming that the exchanged data is partially known at both nodes. This scenario is suitable for channel training. In the second scenario, the BSM is adaptively updated while the real unknown data is exchanged between the nodes i.e. no capacity is wasted for channel identification. The proposed adaptive algorithm is robust to noise as the involved step-size allows a trade-off to reduce the impact of the additive noise at the expense of some estimation delay. Our computer simulations show that the proposed algorithm works efficiently in both modes of operations (training mode and simultaneous training/data transmission mode) for both static and slow fading MIMO channels and for both white and colored noises.

Reciprocal Sound Propagation Experiment in Very Shallow Water Area of Hashirimizu Port

A fundamental experiment for environmental monitoring using reciprocal sound propagation was conducted in a very shallow water area in Hashirimizu Port near the entrance to Tokyo Bay. Sound propagation systems with a 12.5 kHz transducer were placed at opposite piers with a distance of about 120 m. Sound travel time was monitored using M-sequence phase-modulated signals so that an accurate arrival time could be detected even in a noisy environment. Arrival time changed throughout the experiment period about 3 weeks almost in accordance with the changes in seawater temperature. However, under certain conditions, such as a low tide and a high negative gradient of the temperature profile in the depth direction, the arrival time was longer than expected. Ray tracing calculation using Bellhop revealed that all rays radiated by the transducer were refracted downward because of the sound speed profile changes. It turns out that the ray path changes depending on ocean environmental changes, especially changes in temperature and the tides. Current speed estimation from reciprocal travel time showed a trend similar to the measurement result of the acoustic doppler current profiler (ADCP). The low reliability of current can be improved by changing the peak tracking method. It also has a potential to get wide area of ocean environment using reflected waves.

Calculation of the growth kinetics and dispersity of K2SO4 crystals in drops of an evaporating solution

Experimental data on the evaporation kinetics of saturated K2SO4 solution drops and the nucleation kinetics of the first crystals are used to develop a simple procedure for the calculation of the solution concentration and the number, size, and dispersity of growing crystals. The calculation results agree well with the experimental data on the growth kinetics of K2SO4 crystals and their dispersity after complete evaporation of water. The dispersity of crystals is shown to linearly depend on the reciprocal time of evaporation of drops having different initial heights.

Reciprocal Powered Time model for Release Kinetic Analysis of Ibuprofen Solid Dispersions in Oleaster Powder, Microcrystalline Cellulose and Crospovidone

A physically sound derivation for reciprocal power time (RPT) model for kinetic of drug release is given. In order to enhance ibuprofen dissolution, its solid dispersions (SDs) prepared by cogrinding technique using crospovidone (CP), microcrystalline cellulose (MC) and oleaster powder (OP) as a novel carrier and the model applied to the drug release data. The drug cogrounds with the carriers were prepared and subjected to the dissolution studies. For elucidation of observed in vitro differences, FT-IR spectroscopy, X-ray diffraction patterns, DSC thermograms and laser particle size measurement were conducted. All drug release data fitted very well to newly derived RPT model. The efficiency of the carriers for dissolution enhancement was in the order of: CP>OP>MC. The corresponding release kinetic parameter derived from the model, t50% (time required for 50% dissolution) for the carrier to drug ratio 2:1 were 2.7, 10.2 and 12.6 min, respectively. The efficiency of novel carrier, OP, was between CP and MC. FT-IR showed no interaction between the carriers and drug. The DSC thermograms and X-ray diffraction patterns revealed a slight reduced crystallinty in the SDs. Also grinding reduced mean particle size of drug from 150.7 to 44.4 microm. An improved derivation for RPT model was provided which the parameter of the model, t50%, unlike to previous derivations was related to the most important property of the drug i.e. its solubility. The model described very well drug release kinetics from the solid dispersions. Cogrinding was an effective technique in enhancing dissolution rate of ibuprofen. Elaeagnus angostifolia fruit powder was suggested as a novel potential hydrophilic carrier in preparing solid dispersion of ibuprofen.

Constitutive Curve and Velocity Profile in Entangled Polymers during Start-Up of Steady Shear Flow

Time-dependent shear stress versus shear rate, constitutive curve, and velocity profile measurements are reported in entangled polymer solutions during start-up of steady shear flow. By combining confocal microscopy and particle image velocimetry (PIV), we determine the time-dependent velocity profile in polybutadiene and polystyrene solutions seeded with fluorescent 150 nm silica and 7.5 μm melamine particles. By comparing these profiles with time-dependent constitutive curves obtained from experiment and theory, we explore the connection between transient nonmonotonic regions in the constitutive curve for an entangled polymer and its susceptibility to unstable flow by shear banding (Adams et al. Phys. Rev. Lett. 2009, 102, 067801-4). Surprisingly, we find that even polymer systems which exhibit transient, nonmonotonic shear stress-shear rate relationships in bulk rheology experiments manifest time-dependent velocity profiles that are decidedly linear and show no evidence of unstable flow. We also report that interfacial slip plays an important role in the steady shear flow behavior of entangled polymers at shear rates above the reciprocal terminal relaxation time but has little, if any, effect on the shape of the velocity profile.

Solvent Effects on the Kinetics of the Interaction of 1-Pyrenecarboxaldehyde with Calf Thymus DNA

The kinetics of the interaction of a fluorescent probe, 1-pyrenecarboxaldehyde, with calf thymus DNA has been studied in different water/alcohol mixtures (ethanol, 2-propanol, and ter-butanol) at 25 degrees C, by using the stopped flow technique. The kinetic curves are biexponential and reveal the presence of two processes whose rates differ by about 1 order of magnitude on the time scale. The dependence of the reciprocal fast relaxation time on the DNA concentration is linear, whereas the concentration dependence of the reciprocal slow relaxation time tends to a plateau at high DNA concentrations. The simplest mechanism consistent with the kinetic results involves a simple two-step series mechanism reaction scheme. The first step corresponds to the formation of a precursor complex, (DNA/Py)(I), while the second one corresponds to full intercalation of the pyrene dye between the DNA base pairs. The values of the rate constants of both steps decrease as water activity decreases. The results have been discussed in terms of solvation of the species and changes in the viscosity of the solution.

Increase in specific heat and possible hindered rotation of interstitialC2molecules in neutron-irradiated graphite

Irradiation-induced increase in the low-temperature specific heat has been measured in the temperature range of 1.9--43 K in graphite neutron-irradiated to $1.4\ifmmode\times\else\texttimes\fi{}{10}^{20}\text{ }\text{n}/{\text{cm}}^{2}$ $(E>1\text{ }\text{MeV})$ around 333 K. The increase of the lattice specific heat is interpreted as due to the hindered rotation of interstitial ${\text{C}}_{2}$ molecules in the periodic potential of $V(\ensuremath{\varphi})=({V}_{0}/2)(1+\text{cos}\text{ }2\ensuremath{\varphi})$, where $\ensuremath{\varphi}$ is the angle of rotation and ${V}_{0}$ is 0.040 eV. The first-excited rotational level is 0.0058 eV above the ground state and the rotational frequency is $1.39\ifmmode\times\else\texttimes\fi{}{10}^{12}\text{ }{\text{s}}^{\ensuremath{-}1}$. This result shows that ${\text{C}}_{2}$ molecules do not form covalent bonds with atoms in the surrounding graphite layers. It is in marked contrast with the result of recent first-principles theoretical calculations that interstitial atoms form strong covalent bonds with atoms in the graphite layers. The concentration of ${\text{C}}_{2}$ molecules is estimated to be $f=1.16%$. The hole concentration, deduced from the electronic specific heat and the SWMcC band model, suggests that one single vacancy creates one hole and the single vacancy concentration is $2f$. Since the measurement of the lattice specific heat gave the concentration of the defects directly, we could evaluate some physical properties for a unit concentration of the defects. The volume changes by a single interstitial atom, an interstitial ${\text{C}}_{2}$ molecule, and a single vacancy are deduced to be $2.6\ifmmode\pm\else\textpm\fi{}0.3$, $9.3\ifmmode\pm\else\textpm\fi{}1.4$, and $\ensuremath{-}0.46\ifmmode\pm\else\textpm\fi{}0.07$ atomic volumes, respectively. The formation energy of a Frenkel pair is estimated to be $12.6\ifmmode\pm\else\textpm\fi{}2.5\text{ }\text{eV}$. The phonon scattering with a reciprocal relaxation time proportional to ${\ensuremath{\omega}}^{1.5}$, where $\ensuremath{\omega}$ is the angular frequency of phonons, is attributed to the scattering of phonons by the disklike strain around interstitial ${\text{C}}_{2}$ molecule clusters. A broad dip in the $a$-axis thermal conductivity observed below room temperature is attributed to the resonance scattering of phonons by the hindered rotation of interstitial ${\text{C}}_{2}$ molecules as well as by the vibration of these molecules as rigid units. The positron lifetime of 350 ps is suggested to be the lifetime of positrons trapped in an open space on the periphery of the interstitial clusters of ${\text{C}}_{2}$ molecules. The well-known Wigner energy is stored mainly as interstitial ${\text{C}}_{2}$ molecules and single vacancies.

Intracellular Proton Binding is Voltage-Dependent and Rate-Limiting for the Gastric H,K-ATPase Under in vivo Conditions

Compared to the extensively studied Na,K-ATPase reaction cycle, much less is known about the voltage-dependent steps in the pump cycle of gastric H,K-ATPase. Due to the overall electroneutral transport stoichiometry of the proton pump, its voltage-dependent ion transport properties cannot readily be determined by standard electrophysiological techniques.Therefore, we use a combination of two biophysical techniques to investigate H,K-ATPase activity: voltage-clamp-fluorometry on the tetramethylrhodamine-6-maleimide-labeled H,K-ATPase variant αS806C to monitor the voltage-dependent distribution between E1P/E2P-states (Ref. 1) and voltage-controlled Rb+ uptake measurements to assess the steady-state ion transport activity under various pH and ionic conditions in Xenopus oocytes.Both the steady-state E1P/E2P-distribution and Rb+ uptake of the gastric H,K-ATPase are highly sensitive towards changes in intracellular pH (which can be achieved by adding weak organic acids like butyric acid to the extracellular solution), whereas even larger changes in the extracellular pH do neither influence the conformational E1P/E2P-equilibrium nor transport activity. An intracellular acidification of approximately 0.5 pH units results in a large negative shift (∼100 mV) of the voltage-dependent fluorescence amplitudes and an approximately two-fold acceleration of the reciprocal time constants at positive membrane potentials.One possible interpretation of these results is that proton binding takes place in a shallow intracellular ion access channel (apparent well depth: 0.3-0.5).Since maximal rubidium uptake at saturating concentrations is strongly stimulated by intracellular acidification, the voltage-sensitive intracellular proton binding step is apparently rate-limiting for the overall transport activity under physiological conditions. These findings highlight the need for cellullar mechanisms which increase the availability of protons at the cytoplasmic face of the pump, such as CO2-producing mitochondria, sub-membrane carbonic anhydrase and the basolateral Cl-/HCO3- exchanger that are characteristic for parietal cells.

Rotation of Water Molecules and Its Relation with the Chemistry and Physics of Liquid Water

The literature values of the limiting ionic conductivities of H(+), OH(-), K(+), Cl(-), Ag(+), and Na(+) in water between 0 and 156 degrees C are analyzed as for the two possible mechanisms of conduction, i.e., controlled by an activation process or by the rotation of the water molecules. Plots of the data versus T(1/2) give straight lines for H(+) and OH(-), which supports the rotation control mechanism for these ions. The other ions give curved plots and therefore are investigated in terms of the activation control mechanism. A remarkable phenomenon is discovered, namely, that except for H(+), the graphs for the other ions on extrapolation to lower temperatures have a common intersection point, T(0)(1/2), with the abscissa corresponding to T(0) = 243.4 K, i.e., -30 degrees C. This seems to indicate the presence of a virtual phase transition at about -30 degrees C, foreboding itself at higher temperatures. Below this temperature the supercooled water does not allow ions to migrate. Also, diffusion of solutes is found to cease, and dissociation constants drop to zero. The values of many physical properties of water appear also to approach zero at -30 degrees C, viz. the self-diffusion coefficient, reciprocal dielectric relaxation time, and solubilities of sparingly soluble salts. From data on the fluidity (reciprocal viscosity) and self-ionization constant it follows that the transition temperature of supercooled D(2)O is 9 degrees higher than of H(2)O. From the nearly quadratic shape of the several temperature dependencies it is inferred that the phase transition in question possibly is of some higher order. Implications for the transport number of protons to be expected in supercooled water are finally discussed.

On the use of a chaotic cavity transducer in nonlinear elastic imaging

We discuss the advantages of “chaotic cavity transducer focusing” to enhance the localization of microdamage in conjunction with nonlinear elastic wave spectroscopy methods. Chaotic cavity transducer focusing is defined as the hardware-software combination of a piezoelectric ceramic glued on a cavity of chaotic shape on the one hand with the reciprocal time reversal (or inverse filter) technique on the other hand. Additional optimization through the use of sweeps and inverse filtering techniques are discussed as well. The technique is applied to image a crack in a steel sample.

Temperature Dependence of Single Molecule Rotation of the Escherichia coli ATP Synthase F1 Sector Reveals the Importance of γ-β Subunit Interactions in the Catalytic Dwell

The temperature-dependent rotation of F1-ATPase gamma subunit was observed in V(max) conditions at low viscous drag using a 60-nm gold bead (Nakanishi-Matsui, M., Kashiwagi, S., Hosokawa, H., Cipriano, D. J., Dunn, S. D., Wada, Y., and Futai, M. (2006) J. Biol. Chem. 281, 4126-4131). The Arrhenius slopes of the speed of the individual 120 degrees steps and reciprocal of the pause length between rotation steps were very similar, indicating a flat energy pathway followed by the rotationally coupled catalytic cycle. In contrast, the Arrhenius slope of the reciprocal pause length of the gammaM23K mutant F1 was significantly increased, whereas that of the rotation rate was similar to wild type. The effects of the rotor gammaM23K substitution and the counteracting effects of betaE381D mutation in the interacting stator subunits demonstrate that the rotor-stator interactions play critical roles in the utilization of stored elastic energy. The gammaM23K enzyme must overcome an abrupt activation energy barrier, forcing it onto a less favored pathway that results in uncoupling catalysis from rotation.

Migration and interpretation of first arrival inflection points due to lateral variations

ABSTRACTThe majority of shallow refraction seismic algorithms work well only in cases of a horizontal plane or inclined refractors. In case of piecewise lateral variation either in dip angle and/or in velocity along the refracting interfaces, the applications of these conventional methods are usually problematic. This is because of the existence of two different inflection points along the first arrival travel‐time curve. The first inflection point corresponds to the crossover point while the later inflection points are due to these lateral variations. The terms true and apparent inflection points will be used in this study to refer to inflection points corresponding to crossover points and those due to lateral variations, respectively. The intersection of the backward extrapolation from inflection points with the time axes will give true intercept times from true inflection points and apparent intercept times from apparent inflection points.Migration of apparent inflection points aims to remove the distortion due to lateral variations of refracted rays from the first arrival traveltime curves by moving them to their proper locations. After the migration of the apparent inflection points, the intercept time technique can be applied in a conventional way to map shallow subsurface refracting interfaces with piecewise lateral variations. The common traveltime elements recorded from the same refracting interfaces and the layer reciprocal time are required for this migration process.This algorithm will be generalized after the removal of the effects due to the apparent inflection points and calculation of the corresponding migrated traveltime elements. Each pair of the common migrated traveltime elements from forward and reverse directions will represent a simple traveltime curve of two planes. Therefore, most shallow refraction algorithms can be applied to this simple traveltime curve using their own equations to map refracting interfaces recorded from media with piecewise lateral variations.

Anatomic variations of the lacunar–canalicular system influence solute transport in bone

Solute transport in the lacunar–canalicular system (LCS) is essential for bone metabolism and mechanotransduction. Using the technique of fluorescence recovery after photobleaching (FRAP) we have been quantifying solute transport in the LCS of murine long bone as a function of loading parameters and molecular size. However, the influence of LCS anatomy, which varies among animal species, bone type and location, age and health condition, is not well understood. In this study, we developed a mathematical model to simulate solute convection in the LCS during a FRAP experiment under a physiological cyclic flow. We found that the transport rate (the reciprocal time constant for refilling the photobleached lacuna) increased linearly with canalicular number and decreased with canalicular length for both diffusion and convection. As a result, the transport enhancement of convection over diffusion was much less sensitive to the variations associated with chick, mouse, rabbit, bovine, dog, horse, and human LCS anatomy, when compared with the rates of diffusion or convection alone. Canalicular density did not affect transport enhancement, while solute size and the lacunar density had more complicated, non-linear effects. This parametric study suggests that solute transport could be altered by varying LCS parameters, and that the anatomical details of the LCS need systemic examination to further understand the etiology of aged and osteoporotic bones.

Bremsstrahlung from collisions of low-energy electrons with positive ions in a magnetic field

Bremsstrahlung from electron-ion collisions in a magnetic field is studied for low energies at which the Larmor radius of an electron is smaller than the characteristic impact parameter of close collisions in zero magnetic field. It is shown that the magnetic field does not qualitatively change the bremsstrahlung power at low frequencies smaller than the reciprocal time of electron transit in the vicinity of an ion in close collision in zero magnetic field. At high frequencies, the radiation intensity decreases in accordance with a power law, attains its minimal value, and then increases in accordance with a power law up to frequencies on the order of the electron cyclotron frequency. At such frequencies, the spectral power attains typical power values in zero magnetic field. At frequencies lower than the cyclotron frequency considered here, bremsstrahlung is polarized predominantly linearly in the plane formed by the magnetic field and the direction of radiation.

Dispersity and growth kinetics of K2SO4 crystals in drops of an evaporating solution

Growth of K2SO4 crystals is studied in solution drops that have different initial heights and evaporate in different times. The dependences of the crystal size on the crystal growth time are obtained. The following three crystal growth modes are detected: rapid crystal growth in a supersaturated solution, a stop in the growth as a result of complete removal of supersaturation, and slow growth at a quasi-equilibrium solution concentration. The dispersities of the crystals that are retained at the bottom of the drop after complete evaporation of the solvent are calculated. A linear relation between the crystal dispersity and the reciprocal crystal growth time is revealed. The dispersity of K2SO4 crystals and the dispersity of the solid-solution dendrites in aluminum alloys are found to exhibit the same character of their dependences on the reciprocal crystal growth time.

A New Diagnostic Analysis Method for Waterflood Performance

Summary Despite the widespread application of reservoir simulation to study waterflood reservoirs, petroleum engineers still need simple predictive tools to forecast production decline, estimate ultimate oil recovery, and diagnose the production performance from the historical field data. On the basis of the Buckley-Leverett (BL) equation and the assumption of a semilog relationship between the oil/water relative permeability ratio and water saturation, a consistent analytical solution can be derived as fo(1−fo)=(EVB)1tD where fo is the oil fractional flow, tD is the fraction of cumulative liquid production to related formation volume, B is the relative permeability ratio parameter, and EV is the volumetric sweep efficiency. Two equivalent linear plots can be developed: a loglog plot and a reciprocal-of-time plot. The log-log plot has a slope of −1 and intercept of EV/B. The reciprocal time plot has a slope of EV/B and an intercept value of 0. Both plots can be applied for the diagnostic analysis of waterflood reservoirs. Model and field case studies show the benefits of this technique as a production-decline-analysis tool in forecasting the waterflood production decline and the ultimate oil recovery. This method also can be applied as a diagnostic tool to evaluate various aspects of waterflood performance. Examples include assessing waterflood maturity, calculating volumetric sweep efficiency, distinguishing the normal waterflood breakthrough from the premature water breakthrough through hydraulic fractures, and examining the consequences of operational changes. The appropriate use of this analytical method will help to optimize the field waterflood operation.

Passive striation based geo‐acoustic inversion using ships of opportunity.

The coherent interaction of acoustic multipaths leads to an interference pattern in range. As range changes, the locations of the peaks (and troughs) of this interference pattern shift (as the group velocities of the modes change) in a sometimes predictable fashion. The intensity pattern of a moving source, plotted as a function of range and frequency, is commonly referred to as striation patterns. These patterns are commonly observed in the passing of a loud surface vessel in the spectrogram of a single hydrophone. In this paper, a geoacoustic method is presented based upon the quantitative measure of striation slope (wave guide invariant parameter) and the striation spacing in frequency (reciprocal time spread). Both of these parameters are generally sensitive to the geo‐acoustic parameters of the sediment. In 2003 this technique was applied to a passing surface ship [K. Heaney, IEEE JOE 29(1), 43–50 (2003)] and to a range‐dependent benchmark case [K. Heaney, IEEE JOE 29(1), 88–99 (2003)]. The approach in these papers compared the measured acoustic observables with those from a table predicted by the forward computation using the broadband PE. Current implementation of the algorithm uses a Gaussian beam code to efficiently compute the acoustic observables.

Analysis of Tidal Effect on Reciprocal Sound Propagation in Central Pacific Ocean

Long-range-traveling sound in the ocean includes information on ocean phenomena such as changes in temperature, tide, internal wave, and vortex as travel time differences or sound pressure attenuations. In this study, time series of travel time differences between two moorings for an ocean acoustic tomography experiment in the equatorial central Pacific Ocean promoted by JAMSTEC in 2000 were compared with the calculated elevation of sea level predicted from eight major tidal constituents using the tidal model GOTIC2. While diurnal and semidiurnal tidal effects were confirmed from the water temperature changes located near the sound sources, differences in the reciprocal travel time also fluctuated in accordance with the tidal effects. Although the precision of the moorings position detection and travel time tracking from the received signals need to be improved, this analysis is the first step to reveal the dynamics of energy circulation in the sea.

Universal scaling characteristics of stress overshoot in startup shear of entangled polymer solutions

We have carried out conventional rheological measurements to explore the well-known stress overshoot behavior in startup shear of eight entangled polybutadiene solutions. In the elastic deformation regime with γ̇τR>1, we have identified universal scaling features associated with the stress maximum σmax for samples of different levels of entanglements per chain ranging from 27, 40 to 64. Specifically, at the moment tmax of the peak stress σmax where the applied strain is γmax=γ̇tmax: (a) σmax varies linearly with γmax, (b) σmax scales with tmax as σmax∼(tmax)−1∕2. The combination of (a) and (b) yields a striking “prediction” that γmax∼γ̇1∕3. Remarkably, these scaling laws form master curves when the peak stress, strain rate, and peak time are all normalized with the crossover modulus Gc, reciprocal Rouse time, and Rouse time τR, respectively. The dependence of σmax on tmax and γ on γ̇ is weaker in the crossover regime with γ̇τR<1. Equally noteworthy is the emergence of a super-master curve for the normalized stress σ(t)∕σmax as a function of the normalized strain γ̇t∕γmax at various applied rates in these solutions. The solution with only 13 entanglements per chain exhibits behavior deviating appreciably from the well entangled systems. Strain recovery experiments revealed irreversible deformation (i.e., flow) when the sample is sheared beyond the stress maximum (for γ̇τR>1) or when sheared with γ̇τR<1 for a period longer than the Rouse relaxation time τR.