Values Of V0 Research Articles

A bound for wilson's theorem (I)

AbstractIn 1975, Richard M. Wilson proved: Given any positive integers k ⩾ 3 and λ, there exists a constant v0 = v0(k, λ) such that v ϵ B(k,λ) for every integer v ⩾ v0 that satisfies λ(v − 1) ≡ 0(mod k − 1) and λv(v − 1) ≡ 0[mod k(k − 1)]. The proof given by Wilson does not provide an explicit value of v0. We try to find such a value v0(k, λ). In this article we consider the case λ = 1 and v ≡ 1[mod k(k − 1)]. We show that: if k ⩾ 3 and v = 1[mod k(k − 1)] where v > kkk5, then a B(v,k, 1) exists. © 1995 John Wiley & Sons, Inc.

Dendrite Growth from the Undercooled Melts of Alloys.

The dendrite growth rates for Ag-5mass%Cu and Cu-10mass%Ni alloys are measured as a function of the degree of bath undercooling. The growth rates for pure silver and copper in the literature are compared with the model and the characteristic value of interface kinetics is determined by fitting the prediction curves the the data. The determined values of the upper limit or interface advance, V0, are 500 ms-1 for silver and 600 ms-1 for copper, which correspond to the values of the linear kinetic coefficient of 0.5 ms-1K-1 for silver and 0.6 ms-1K-1 for copper, respectively. With the determined values of V0 the data of dendrite growth rates for alloys are analyzed using the LKT model. The data are in good agreement with the estimation by the model only when nonequilibrium effects are assumed. The estimated values of growth rate coefficient, β0 (=a0/DL) are about 1.0 m-1 s for both alloys. The result shows that the nonequilibrium effect proposed by Aziz and by Boettinger and Coriell are quite applicable.

On the bifurcation structure of axisymmetric vortex breakdown in a constricted pipe

The bifurcation structure is presented for an axisymmetric swirling flow in a constricted pipe, using the pipe geometry of Beran and Culick [J. Fluid Mech. 242, 491 (1992)]. The flow considered has been restricted to a two-dimensional parameter space comprising the Reynolds number Re and the relative swirl V0 of the incoming swirling flow. The bifurcation diagram is constructed by solving the time-dependent axisymmetric Navier–Stokes equations. The stability of the steady results presented by Beran and Culick, obtained from a steady axisymmetric Navier–Stokes code, has been confirmed. Further, the steady solution branch has also been extended to much larger V0 values. At larger V0, a stable unsteady solution branch has been identified. This unsteady branch coexists with the previously found stable steady solution branch and originates via a turning point bifurcation. The bifurcation diagram is of the type described by Benjamin [Proc. R. Soc. London Ser. A 359, 1 (1978)] as the canonical unfolding of a pitchfork bifurcation. This type of bifurcation structure in the two-dimensional parameter space (Re,V0), suggests the possibility of hysteresis behavior over some part of parameter space, and this is observed in the present study. The implications of this on the theoretical description of vortex breakdown and the search for a criterion for its onset are discussed.

Maximum shortening velocity and coexistence of myosin heavy chain isoforms in single skinned fast fibres of rat skeletal muscle

Myosin heavy chain composition of a large number (288) of single fibres from slow (soleus), and fast (superficial part of tibialis anterior, and plantaris) muscles of adult (3-5-month-old) Wistar rats was determined. A combination of SDS-PAGE and monoclonal antibodies against myosin heavy chains allowed to identify four myosin heavy chain isoforms (1, 2A, 2X, and 2B) and to detect myosin heavy chain coexistence. Four groups of fibres containing only one myosin heavy chain (1 myosin heavy chain, 2A myosin heavy chain, 2X myosin heavy chain, and 2B myosin heavy chain), and five groups containing more than one myosin heavy chain (1 and 2A myosin heavy chains, 2A and 2X myosin heavy chains, 2X and minor amounts of 2B (2X-2B fibres), 2B and minor amounts of 2X (2B-2X fibres), and 2A, 2X, and 2B myosin heavy chain were identified and their relative percentages were assessed. Coexistence of fast myosin heavy chain isoforms was found to be very frequent (50% of the fibres in plantaris, and 30% in tibialis anterior), whereas coexistence of slow and fast (2A) myosin heavy chain was very rare. Maximum shortening velocity (V0) was determined using the slack-test procedure in a subset of 109 fast fibres from the above population. The values of V0 formed a continuum extending from 2A to 2X to 2X-2B to 2B-2X to 2B fibres. 2A fibres had the lowest value of V0 and 2B fibres the highest. Only the differences between 2A and 2B and 2A and 2B-2X fibres were statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Kinetics of Divalent Cation-Induced and pH-Induced Aggregation of Dimyristoylphosphatidylserine Vesicles

Kinetic study was carried out on the aggregation of dimyristoylphosphatidylserine (DMPS) vesicles induced by the addition of divalent cations (Mg2+, Ca2+, Sr2+, and Ba2+) as well as by pH jump, using a stopped-flow method with turbidity detection. With the increase in cation concentration, the initial rate of aggregation, V0, increased rapidly above the threshold concentration of about 1 mM, and reached the maximum velocity, V0,max . The increase in V0 toward V0,max with the concentration was appreciably dependent on the cation species, whereas the value of V0,max was not affected significantly by the cation species. This behavior of aggregation kinetics of DMPS vesicles is well described in terms of the intervesicular interaction potential composed of van der Waals attraction and electrostatic repulsion, without introducing an extra force such as hydration force which is regarded as responsible for the stability of phosphatidylcholine vesicles. The aggregation of DMPS vesicles was also induced when the negative charge on the DMPS head group was eliminated by protonating the serine carboxyl group by mixing the vesicle preparation with acid solution. This observation is in accordance with the above interpretation that no hydration force acts between DMPS vesicles to such an extent that the aggregation kinetics are affected appreciably.

Distribution of Planetary Nebulae Perpendicular to the Disk

From an analytical solution to the Boltzmann-Poisson equations for a thin, vertically isothermal self-gravitating disk with the assumptions that the mass spectrum of stars is expressible as an inverse power-law and the velocity dispersion perpendicular to the plane follows a law of the form we have obtained a vertical height distribution of planetary nebulae: where being the potential at z. Figure 1 shows a normalised height distribution for various values of V0 where we have assumed a Salpeter slope, a ρ(o) = 0.10M⊙pc−3 and set m∗ = ml = 1.0m⊙. Figure 2 shows filled circles obtained from the observational sample of Daub (1982, ApJ 260, 612) superposed on the theoretical distributions. Although there is agreement for large values of z, closer to the plane the observational sample falls below the theoretical curves. Since the observational sample is size-limited, we may be missing a larger fraction of small nebulae closer to the plane. It is also possible a single value of Vo is not a correct representation of reality as these nebulae originate from stars of greatly differing ages and Vo may have changed over the lifetime of the Galactic disk.

Anaerobic and aerobic components during arm-crank exercise in sprint and middle-distance swimmers

The purpose of this investigation was to compare anaerobic and aerobic components measured during arm exercise in sprint and middle-distance swimmers and to investigate whether the peak anaerobic power:peak aerobic power ratio (W(an),peak:Waer,peak) was related to specialization for the event and to performance. The W(an0,peak, force at zero velocity (F0), and velocity at zero-force (v0), Waer,peak, peak oxygen uptake (VO2peak), and ventilatory threshold (Thv) were compared during arm exercise tests in sprint (group I, n = 8) and middle-distance (group II, n = 9) competitive male swimmers. Anaerobic indices were estimated by the force-velocity test, an anaerobic test using incremental braking forces; aerobic indices were measured during an incremental aerobic exercise test (30 W.min-1). The W(an),peak and Waer,peak were greater in group I [828 (SEM 70) W; 236 (SEM 12) W] than in group II [678 (SEM 28) W; 230 (SEM 5) W], but the differences were not significant. There were also no significant differences observed between the mean values of F0, v0, VO2peak, and Thv. The W(an0,peak:Waer,peak, however, was significantly higher in sprint swimmers (t = 3.08, P < 0.01). In seven of the swimmers, who had recently performed both the 100-m and 400-m front crawl, a relationship existed between their swim time and the W(an),peak:Waer,peak (100 m: r = -0.80, P < 0.05 and 400 m: r = +0.75, P < 0.05). In conclusion, during arm-crank exercise, we did not observe significant differences in anaerobic and aerobic components between sprint and middle-distance swimmers.(ABSTRACT TRUNCATED AT 250 WORDS)

Density dependence of excess electronic ground-state energies in simple atomic fluids

The ground-state energies of an excess electron E0 as a function of solvent density are computed using model electron–atom pseudopotentials in fluid helium, argon, and xenon. E0 is a lower bound to the experimentally measurable threshold to photoconductivity, V0. The nonuniqueness of the pseudopotential description of electron–molecule interactions is demonstrated. We find that when many-body polarization effects are included, our calculated E0 results are in close agreement with experimental V0 values indicating that the conduction-band energy lies close to the ground-state energy across a broad range of densities in these polarizable fluids. If the many-body nature of the polarization interaction is ignored the ground-state energies deviate significantly from the V0 results highlighting the importance of accurate treatment of many-body polarization interactions. It is shown that a mean-field theory of polarization gives substantial agreement with full many-body calculations. This allows us to introduce a mean-field, density-dependent pair potential which greatly simplifies such many-body calculations. In the more polarizable systems, it is found that the spatial extent of the ground-state wave function as a function of solvent density is correlated with the density dependence of both V0 and the electron mobility, and it becomes uniformly spread throughout our simulation cell as the electron mobility goes through its maximum value at intermediate solvent densities.

Path-integral molecular-dynamics calculation of the conduction-band energy minimum V of excess electrons in fluid argon

Using path-integral molecular-dynamics simulations, we calculate the conduction-band energy minimum V0 (relative to vacuum) of an excess electron injected in fluid argon over a range of densities (n) from the gas phase to the liquid near the triple point. An accurate pseudopotential is employed to represent the electron–argon interaction. Special attention is paid to the convergence on the number of beads of the isomorphic electron polymer chain, the simulation-box size, and the question of ergodicity. The calculated V0(n) values are in very good agreement with experimental data. As a result of the very extended character of the excess electron state at all fluid densities considered, the precise value of V0 is shown to be only weakly sensitive to the degree of disorder and the coordination number of the fluid. Relaxation effects are also found to be negligible. These results account for the success of the mean-field approximation afforded by the Wigner-Seitz V0(n) calculations for the heavy rare-gas fluids. Finally, we find that screening of the long-range polarization tail plays a crucial role in the delicate balance between the attractive and repulsive electron–fluid interactions, which is responsible for the appearance of the minimum of V0(n).

Crack-Bridging Effect on Mixed-Mode Propagation of Intralaminar Fatigue Cracks in Unidirectional CFRP.

The growth behavior of intralaminar fatigue cracks in a unidirectional carbon/epoxy laminate, Toray T300/#2500, was studied under mixed-mode loading with a ratio of mode II stress intensity factor (SIF) to mode I SIF equal to 2.50. Under a constant value of the applied SIF range, ΔKIap, the crack propagation rate decreased with the crack extension because of crack-tip shielding by crack bridging. For each value of ΔKIap, the relationship between the crack propagation rate, da/dN, and the crack extension, Δa, was expressed by the following equation: log(da/dN)=log V0-Δa log V1, where V0 and V1 are functions of the applied SIF value. The value of V0 which is the crack propagation rate without crack bridging was approximated by a power law function of the crack-tip value of the SIF range, ΔKItip. On the basis of the power law relationship, a method for evaluating the shielding SIF range, ΔKIbridge, was proposed. ΔKIbridge monotonically increased with the crack extension. Futhermore, ΔKIbridge for a small ΔKIap value was higher than that for a large ΔKIap value when compared to the same amount of crack extension.

Nuclear magnetic resonance survey of hydrogen motion and electronic structure in α-phase (NbMo)-H alloys

The results of a proton nuclear magnetic resonance (NMR) survey of hydrogen motion and electronic structure in the solid solution (α) phase of niobium rich Nb1−yMoyHx alloys are reported (y ⩽ 0.2, x ⩽ 0.2). Measurements of the temperature dependence of the proton spin-lattice relaxation time T1 over the range 20 ⩽ T ⩽ 800 K were analyzed to yield values of the activation energy Ea and jump attempt frequency v0 for hydrogen diffusive hopping and of the product T1eT = Ce indicative of the electronic density-of-states at the Fermi level, N(EF), where T1e is that contribution to T1. The T1vs. T behavior shows features characteristic of hydrogen in random alloys, reflecting a distribution of Ea and v0 values. At high temperatures (~ 500 K), T1 exhibits anomalous behavior, passing through a maximum and decreasing again at higher temperatures in the same manner found in the NbH and (NbV)-H systems.

Ballistic electron emission spectroscopy of metals on GaP(110)

Ballistic electron emission spectroscopy (BEES), a technique based on the scanning tunneling microscope (STM), was used to measure Schottky barrier heights of metals on cleaved n-type GaP(110). The threshold voltages V0 for current detection in the semiconductor were found to be uniform to within ±0.02 V over the sample surface for any given metal on GaP. A transport model for the current Ic crossing the barrier, that includes both nonclassical transmission across the metal–semiconductor interface and electron scattering in the metal, yields Ic∝(V−V0)5/2 near threshold. The value of V0 extracted from the data, which represents the Schottky barrier height, depends somewhat on the details of the transport model. Our best estimates of the Schottky barrier heights, within ±0.03 eV, are 1.07 (Mg), 1.11 (Ni), 1.14 (Bi), 1.25 (Cu), 1.31 (Ag), and 1.46 eV (Au).

Force‐velocity relations and myosin heavy chain isoform compositions of skinned fibres from rat skeletal muscle.

1. This study was performed to assess whether muscle contractile properties are related to the presence of specific myosin heavy chain (MHC) isoforms. 2. Force-velocity relations and MHC isoform composition were determined in seventy-four single skinned muscle fibres from rat soleus, extensor digitorum longus and plantaris muscles. 3. Four groups of fibres were identified according to their MHC isoform composition determined by monoclonal antibodies: type 1 (slow), and types 2A, 2B and 2X (fast). 4. With respect to maximum velocity of shortening (V0), the fibres formed a continuum between 0.35 and 2.84 L/s (muscle lengths per second) at 12 degrees C. V0 in type 1 fibres (slow fibres) was between 0.35 and 0.95 L/s (0.639 +/- 0.038 L/s; mean +/- S.E. of mean). V0 in type 2 fibres (fast fibres) was consistently higher than 0.91 L/s. Ranges of V0 in the three fast fibre types mostly overlapped. Type 2A and 2X fibres had similar mean V0 values (1.396 +/- 0.084 and 1.451 +/- 0.066 L/s respectively); type 2B fibres showed a higher mean V0 value (1.800 +/- 0.109 L/s) than type 2A and 2X fibres. 5. Mean values of a/P0, an index of the curvature of force-velocity relations, allowed us to identify two groups of fibres: a high curvature group comprised of type 1 (mean a/P0, 0.066 +/- 0.007) and 2A (0.066 +/- 0.024) fibres and a low curvature group comprised of type 2B (0.113 +/- 0.013) and 2X (0.132 +/- 0.008) fibres. 6. Maximal power output was lower in slow fibres than in fast fibres, and among fast fibres it was lower in type 2A fibres than in type 2X and 2B. 7. Force per unit cross-sectional area was less in slow fibres than in fast fibres. There was no relation between fibre type and cross-sectional area. 8. The results suggest that MHC composition is just one of the determinants of shortening velocity and of other muscle contractile properties.

Boundary-condition refinement of the Child–Langmuir law for collisionless dc plasma sheaths

An exact solution to the problem of collisionless, space-charge-limited flow of cold ions across a one-dimensional (planar) dc plasma sheath of negligible electron density is derived for general values of the presheath ion velocity v0 and electric field E0. For a given ion current density J and sheath thickness d, the exact solution reduces to the classical Child–Langmuir model in the case that v0=0 and E0=0. When either v0 or E0 is sufficiently large, however, the exact solution may differ appreciably from the Child–Langmuir law. The existence of a closed-form expression for the spatial variation of the sheath potential is shown to be contingent upon the satisfaction of a simple inequality relating v0 and E0 to J. When v0 obeys the Bohm criterion and the magnitude of E0 suggests that the Bohm energy is acquired over a distance not less than one Debye length, this inequality is indeed satisfied.

Density dependence of the ground-state energy of excess electrons in liquid methane

The ground-state energy (V0) of excess electrons in liquid methane is calculated as a function of liquid density. In the calculation, we use a high-precision molecular potential which satisfactorily describes the scattering of low-energy electrons in the gas phase. Our results are found to reproduce very well the experimental V0 values.

Calculation of the thermodynamic and transport properties of aqueous species at high pressures and temperatures: Correlation algorithms for ionic species and equation of state predictions to 5 kb and 1000°C

Correlation algorithms permit prediction of species-dependent parameters in revised equations of state (tanger and Helgeson, 1988) for aqueous ions and electrolytes which can be used together with values at 25°C and 1 bar of the standard partial molal entropies (S0), volumes (V0), and heat capacities (C0p) of the ions to calculate their standard partial molal thermodynamic properties at pressures and temperatures to 5 kb and 1000°C. Values of V0 and C0p at 25°C and 1 bar have been calculated for 128 aqueous ions from analysis of published experimental data or from correlations of these properties with S0. Equation of state parameters have also been generated for these ions and examples are given of predicted standard partial molal thermodynamic properties of representative cations and anions at high pressures and temperatures. Close agreement between independently predicted and experimentally determined equilibrium constants for acid anion dissociation reactions at high temperatures supports the validity and generality of the predictive algorithms.

Measurement of Instability Initiation Current in Vacuum Ar

The arc current for initiating the appearance of noise on a current trace, the instability initiation current I0, and the arc voltage V0 corresponding to I0, have been measured using Cu-Ni alloy and Ag-Pd alloy electrode metals. The average values of I0 and V0 were plotted as a function of the thermal conductivity λ, showing a decrease with decreasing λ under a constant vapor pressure Ph.

Spin fluctuations of paramagnetic iron centers in proteins and model complexes: Mössbauer and EPR results

We have analyzed the Mössbauer spectra of several iron proteins in the regime of intermediate fluctuation rates of the magnetic hyperfine interaction using the dynamic line shape model of Clauser and Blume. All Mössbauer data were recorded in applied fields so that the electron Zeeman interaction is much larger than the hyperfine splittings. We modeled the transitions between the eigenstates of the electronic spin Hamiltonian by an effective spin–phonon coupling V(1)=V0∑′i,j=x,y,zSi Sj and described the phonons in the Debye approximation. With V0 as the only adjustable parameter the model reproduced the major temperature dependence of the spectral shapes for spins from S=1 to S=5/2. We found V0 to lie in the narrow range 3 K ≤V0/k≤19 K, which is of the order of the zero-field splittings, but does not correlate with it. The smallest values of V0 were observed in the four-coordinate iron–sulfur proteins. Refinements and implications of the model are discussed.

THE SPECTROSCOPIC ORBITS OF BV AND BW DRACONIS.

ABSTRACT Reticon spectra of high dispersion and time resolution have been obtained of BV an BW Draconis, which together form a visual binary and each of which is a W UMa system. The spectra were measured by cross-correlation. The orbital elements of BV Dra have been revised to the values T0 = 2446127.6888, K1 = 93.9 km s-1 and K2 = 233.6 km s-1, while those of BW Dra, determined for the first time, are T0 = 2446135.8067, K1 = 70.5 km s-1 and K2 = 251.5 km s-1. A circular orbit is adopted for each system. Different values of V0 are obtained from each component of each system, but V0 for each pair is close to -60 km s-1. Radial velocities confirm the proper motions in identifying the two systems as a genuine binary (ADS 9537) whose space velocity with respect to the Sun is over 90 km s-1. From spectrophotometry, the components of BV Dra are classified as F9 (more massive star) and F8, with a luminosity ratio (in blue light) of 1.78 (Δm = 0.63), while the components of BW Dra are G3 (more massive star) and G0, with a luminosity ratio (also in blue light) of 1.52 (Δm = 0.45). All four stars are of luminosity class V.

Effects of Monitoring Vocal Intensity on Oral Air Flow in Children and Adults

The purposes of the present investigation were (a) to determine whether child and adult oral air flow data were parallel across two monitoring methods, (b) to determine whether an instruction to speak at a "comfortable effort level" resulted in greater variability of peak oral air flow (Vo) than visual monitoring of vocal intensity level, and (c) to expose possible sources of variation introduced by visual monitoring. Peak Vo from children and adults was measured for stops and fricatives in connected speech during a "comfortable-effort-level" task and during a visually monitored vocal intensity task. The lack of an age-by-monitoring effect in the analysis of variance (ANOVA) showed that child and adult data were parallel. The nonsignificance of F-Max scores for testing across-subject variability showed that the natural maintenance of a comfortable intensity level did not produce greater Vo variance than visual monitoring. This result was extended by a within-subjects comparison: visual monitoring induced subjects to alter their Vo production for some phonemes. Although the Vo of voiced consonants increased only slightly from comfort-level to visual monitoring, the Vo of voiceless consonants increased more sharply. Thus, visual monitoring does not decrease Vo variability, and does introduce spurious Vo values for some consonants.