Step-like Increase Research Articles

The plane turbulent shear layer with periodic excitation

The influence of periodic excitation on a plane turbulent one-stream shear layer with turbulent separation was investigated. For the qualitative study flow visualization was employed. Quantitative data were obtained with hot-wire anemometry and spectrum analysis. It was found that sinusoidal perturbations with frequencies of order f0 [lsim ] u0/100θ0 (depending on excitation strength), introduced at the trailing edge are always amplified. Maximum amplification factors are observed for the lowest perturbation levels. The frequency and amplitude of excitation determine the downstream location of the amplification maximum in the flow. At sufficient amplitude two-dimensional vortices are formed which subsequently decay without pairing. The development of the periodic r.m.s. values along x follows a universal curve for all frequencies and amplitudes when properly normalized.At high excitation amplitudes the flow development depends strongly on the geometrical conditions of the excitation arrangement at the trailing edge. Thus regular vortex pairing as well as suppression of pairing can be achieved.The excited shear layer has considerably stronger, yet nonlinear, spread than the neutral. The region of vortex formation, irrespective of whether it includes pairing or not, is associated with a step-like increase in width, while after the position of maximum vortex energy, i.e. in the region of decay, the spread is reduced to values below the neutral. There the overall lateral fluctuation energy is increased, while the longitudinal may be decreased as compared with the neutral flow.

南半球モンスーン(1978-79)開始前後における熱,水蒸気,および渦度の収支

A step-like increase in the 850mb zonal mean westerlies over the equatorial Southern Hemisphere (3.75°-11.25°S, 90°E-180°) occurred between 22-30 December 1978. This event was used to subjectively define the onset for the 1978-79 Southern Hemisphere monsoon. During the onset period, widespread increases in 850mb cross-equatorial northerlies occurred over the western Pacific between 120°E and the dateline, reflecting the intensified low-level Hadley circulation after the onset. Over the maritime continent (Sumatra, Borneo, New Guinea), the large-scale apparent heating rate (Q1) decreased considerably from the preto post-onset phase. By contrast, drastic intensification in Q1 heat sources took place near Cape York Peninsula and the equatorial South Pacific east of Australia, with a maximum heating rate of about 4°C per day at 447mb. The spatial distribution of the large-scale apparent moisture sources (Q2) exhibits a parallel feature to that of the Q1 pattern for both the pre- and post-onset phases. An approximate inverse relationship exists between the large-scale apparent vorticity sources (Z) at 850 and 200mb over the Southern Hemisphere monsoon region. For example, near Cape, York Peninsula, large positive Z values at 850mb are contrasted with pronounced negative Z values at 200mb after the onset.

Dissociative hydrogen adsorption on nickel surfaces: Absence of a magnetocatalytic effect

The temperature dependence of the rate of dissociative hydrogen adsorption on Ni(111) and Ni(110) surfaces was determined by monitoring the rate of HD production from a mixed H 2 and D 2 molecular beam striking the sample surfaces. No anomaly was found in the vicinity of the Curie point T c if the surfaces were rigorously kept clean. A step-like increase of the rate was, however, observed near T c if the surfaces were slightly contaminated with carbon which dissolves in the bulk in this temperature range and segregates back upon cooling. The results are discussed in view of the present knowledge of the magnetic properties of nickel surfaces.

Crystal-field induced anomalies in the thermoelectric power and electrical resistivity of amorphous cerium alloys

The amorphous alloys Ce 72Cu 28, Ce 80Au 20 and Ce 89Al 11 exhibit a pronounced maximum in the thermoelectric power near 50 K, together with a step-like increase of the electrical resistivity. This is interpreted in terms of a model invoking Kondo scattering from the cerium 4 f states split by the local crystal fields of the amorphous matrix. The data for the alloys with Cu and Au indicate a narrow distribution of the overall crystalfield splittings. This hints at a rather uniform structural short-range order.

Role of procaine and washed red cells in the isolated dog heart perfused at 5° C

Isolated dog hearts were perfused for 24 hours at 5 degrees C with one of three solutions: plain Krebs solution, Krebs solution containing 167 mg/L of procaine hydrochloride, or Krebs-procaine solution with washed red cells (hematocrit 2%). Coronary vascular resistance (CVR) of hearts perfused with Krebs solution alone increased sharply between the eighth and the twelfth hours of perfusion and then stabilized. Increase of myocardial firmness paralleled the increase of CVR. The addition of procaine to Krebs perfusate kept the heart flaccid and suppressed the steplike increase in CVR but failed to improve significantly the preservation of the hearts. The addition of washed red cells to Krebs perfusate kept CVR near baseline level, improved coronary perfusion flow, doubled myocardial oxygen consumption, reduced edema formation, and improved left ventricular stroke work (LVSW) of the preserved heart. This improvement seems mostly related to a mechanical effect of red blood cells on capillary flow distribution of the heart.

Measurements of temporal and spatial sequences of events in periodic precipitation processes

A series of new experiments on Liesegang ring (or band) formation is presented which is concerned with the temporal and spatial evolution of the process of structure formation. We have chosen NH4OH and MgSO4 to form rings of Mg(OH)2 precipitate in a gelatin gel, as well as KI and Pb(NO3)2 for periodic precipitation of PbI2 in an agar gel. A temporal sequence of events during the entire period from the start of a Liesegang experiment in a test tube to the completion of the final ring pattern has been determined at many locations in the tube by visual observations and by measurements of transmitted light, of scattered light, of deflection of the transmitted light beam, and of gravity effects. After diffusion of one electrolyte into the gel medium containing the second electrolyte results in an ion product larger than three times the solubility product, at any and all points in space, we observe the onset of homogeneous nucleation of colloidal particles by a steplike increase of the index of refraction. The colloid concentration and the particle number density at the nucleation site are estimated to be 10−2 mol/l and 1015 to 1016 cm−3, respectively. Nucleation is followed by the growth of colloidal particles which gives rise to distinct light scattering (turbidity). Both nucleation and colloid formation take place in space continuously; the fronts of these phenomena move through the system and obey a simple diffusion law. A substantial time interval after their passage, there arises a localized gradient of the index of refraction at the prospective ring positions which indicates onset of structure formation by means of a focusing mechanism. While the localized gradient becomes more pronounced and narrower in space, the turbidity in the regions on either side of the ring location decreases, which indicates a depletion in colloidal material in the neighboring zones. Eventually, a sharp band of visible precipitate appears, which is clearly separated from the preceding ring. We conclude that the ring formation is a postnucleation phenomenon in that structure arises from a spatially continuous region of colloid a long time after nucleation has occurred, and propose that it is associated with the autocatalytic growth of colloidal particles. The location of rings is not determined by the spatial pattern of nucleation and colloid deposition as predicted by the Ostwald–Wagner–Prager theory. Our conclusions are supported by experiments on the influence of gravity on the ring locations, which provide evidence for the existence of colloidal particles of several hundred angstroms in size for a substantial fraction of the time required for the formation of a visible structure.

比抵抗変化計によつて記録した Preseismic な大地比抵抗変化

An observation system for routine recording of the ground's resistivity change was established on May 14, 1968 by the writer at the Aburatsubo Crustal Deformation Observatory, University of Tokyo, on a coast of the Miura Penninsula, Kanagawa Prefecture.During the observation period from May 14, 1968 to Feb. 28, 1975, 30 records of clear coseismic resistivity change were observed at remarkable earthquakes in and around Japan. Among 30 earthquakes, there are several cases accompanying some sort of preseismic resistivity changes of which the duration times are of the order of a few hours.The most typical records of preseismic resistivity change are those for two earthquakes of M=7.9 (Tokachi-Oki) at Δ=936km on May 16, 1968, and M=6.9 (Izu-Hanto-Oki) at Δ=144km on May 9, 1974. The duration times of preseismic resistivity change for two earthquakes are 2 and 4 hours, respectively. In both cases, resistivity decreased. Among 30 coseismic resistivity change records, 17 cases clearly indicate preceding resistivity changes about a few hours prior to each earthquake occurence.The patterns of these 17 preseismic resistivity changes are classified into three types, i. e., I, II and III. Type I is a gradual change of the ground's resistivity leading to a step-like coseismic change. The recorded pattern shows a half dome type or its upside down. Type II is characterized by more or less linear decrease in resistivity mostly followed by step-like coseismic resistivity increase. Type III is a step-like change preceding the coseismic change.A new type of precursory resistivity change was observed associated with the Izu-Hanto-Toho-Oki Earthquake of M=6.7, June 29, 1980. This type of change, possibly classified as type IV, is characterized by an intermittent pulse-like change toghther with a box-car type change.

Experimental study of dynamic effects in bubble boiling of liquids

Results of an experimental study of the principles of the transient processes in vapor bubbles for a steplike increase in thermal load are presented.

Anomalous subsidiary absorption in single-crystal YIG and evaluation of spin-wave linewidth

Measurements of the subsidiary absorption spin-wave instability threshold hcrit in high-quality single crystals of yttrium iron garnet reveal anomalous structure over a field interval extending several hundred Oe below the butterfly curve minimum at Hc. Such measurements have now been extended to cover the entire butterfly curve for sphere and plate samples. At the low-field end of the structure region, hcrit increases rapidly as the static field H is decreased to a ’’kink’’ field H′c. As H is reduced further, the increase in hcrit is much more gradual. The nature of the onset changes drastically at H′c, from a gradual increase to an abrupt jump in reflected power at threshold. Theoretical analysis of the data shows: (1) The instability at Hc is for spin waves with a polar angle ϑk of 22° rather than the 35° value often cited. (2) The field interval for the instability of zero wave number (k=0) modes is not confined to H≳Hc, but extends over a wide range down to H′c. (3) The kink at H′c corresponds to an abrupt transition to k≠0 spin waves at lower fields. These features are all due to the effect of the k dependence of ΔHk, the spin-wave linewidth, on hcrit. However, a steplike increase of ΔHk for k≠0 modes, rather than the linear dependence inferred from parallel pumping, is needed for a quantitative fit. This observation, while in partial agreement with the existing three-magnon confluence theory, shows the need for a refined calculation. The structure between Hc and H′c varies with sample shape and appears to be related to low-k magnetostatic mode excitations in the spin-wave spectrum.

High-temperature anelasticity and elasticity of mantle peridotite

An apparatus has been devised which allows precise creep and relaxation measurements to be made on minerals and rocks at temperatures up to 1600°C and at very low deviatoric stresses (1 < σ < 300 bar). This paper is concerned with measurements on mantle peridotite (lherzolite) from Balmuccia (Zone of Ivrea, Italy). The reaction of the sample to a step-like increase in stress is called its “creep function”. It is shown that the creep function contains all the necessary information to derive the spectra of the quality factor Q(ω) and of Young's modulus E(ω), within the seismic range of frequencies, provided the material behaves as a linear system. This has been proven up to a strain of 5 × 10−5. The Q−1-spectra at 1200 and 1300°C, obtained by Fourier inversion from the creep function, show no pronounced peak in the frequency band 0.01 < tf < 1 Hz and exhibit a general tendency to decrease slightly with frequency. The creep function: ϵ(t) = ϵu · [1 + 3.7 · q · {(1 + 50t)0.27 − }], where q is related to Q, satisfactorily describes the data at high temperatures and leads to Q−1(ω, T) = 3 × 103 · ω−0.27 · exp(−30RT) E(ω) is related to Q(ω) by the material dispersion equation. Above 1100°C the unrelaxed Young's modulus decreases rapidly with temperature according to an activation energy of about 20 kcal/mole. A lowering of short period S-wave velocity by 40% and P-wave velocity by 10% occurs below the solidus. Therefore, no partial melting is required in the asthenosphere. Steady-state creep at low axial stresses (20 < σ < 100 bar), obtained from the same rock, follows the relation ϵ̇ = 3 × 107 · δ1.4 · exp(−125RT) indicative of grain boundary diffusion or superplasticity. At higher stresses a power law ϵ̇ = 45 · δ4 · exp(−125RT) typical of dislocation creep, is found. The frequency dependence of Q and the ratio of the activation energies of Q and are indicative of so called “high-temperature background absorption”, as the dominant mechanism, and of a diffusion-controlled dislocation mobility common to both absorption and creep. From a, b, and c, relations between the effective viscosity ηf and Q of the form: logηe⨍⨍ = 1α · logQ − (n − 1) · log ω + log D are derived, where α ∼ 0.25, n is the power of σ, and D is a constant.

Crustal structure near Explorer Ridge from a marine deep seismic sounding survey

In 1974, two reversed, 75‐km, deep seismic sounding profiles were recorded in the Explorer Ridge region of the northeast Pacific, one parallel and the other perpendicular to the ridge. Multichannel seismograms recorded at distances beyond 4 km were stacked, filtered, and statics‐ and amplitude‐corrected before compilation as record sections. The data have been interpreted using both travel time analysis and amplitude studies with the aid of synthetic seismograms. For the reversed profiles (74‐2 and 74‐2R) across the ridge, significantly different velocity‐depth curves were derived. The uppermost 2.5 km (subbottom) is similar with a rapid increase in velocity from about 2.5 to 5.6 km/s. However, the depth to and the form of the increase from about 5.6 to 6.8 km/s are different. Profile 74‐2 shows a small steplike increase followed by a substantial velocity gradient, while 74‐2R has a large steplike increase followed by a lesser gradient. The deeper crust as shown by 74‐2 consists of a monotonie velocity increase, but with changing velocity gradient, to the upper mantle. On 74‐2R, a deep crustal low‐velocity zone was required. It is suggested that this may be associated with a magma chamber beneath Explorer Ridge. For the two profiles (74‐1 and IR) parallel to the ridge, large velocity gradients in the uppermost crust also are derived. Our preferred interpretation to explain travel time delays and offsets involves crustal faulting with vertical offsets of approximately 5 km. An alternative interpretation in terms of a low‐velocity zone also is given. The total subbottom thickness of the oceanic crust varies between 8 and 10 km, except in the faulted regions, where it is thin. In the upper mantle, reversed velocities of 7.9 and 7.3 km/s are determined in directions perpendicular and parallel to the ridge; anisotropy is proposed to explain these different velocities. The interpreted velocity‐depth models are discussed in terms of petrologic models of the oceanic crust and recent determinations of the seismic velocity and lithologie structure of a New‐foundland ophiolite complex. In the uppermost crust, the large velocity gradients probably result from the closing of large cracks and pore spaces within the basalt. In the lower crust, our results are consistent with proposals involving gradual transitions between material of differing composition.

Detection of superconducting inhomogeneities by penetration depth measurements δλ (T, f, B&amp;lt;inf&amp;gt;ac&amp;lt;/inf&amp;gt;)

Small regions of differently strong superconducting interaction have been detected by measuring the penetration depth Δλ(T,f,B ac ) and the losses ΔR(T,f,B ac ) as deviation from the BCS theory of homogeneous materials. For Nb two deviations are most pronounced: a step-like increase in Δλ(T) and ΔR(T) at T* \simeq 7 K and an enhanced slope λ 0 = dλ/dy [y = 1/\sqrt{1-(T/T_{c})^{4}}] for T > T*. The step Δλ 0 around 7 K shows the transition of regions to the normal state, which then for T > T* yield an enhanced slope λ 0 , as explained by proximity effect theory. For Nb 3 Sn no such deviations from the BCS theory could be detected, showing together with λ 0 = 170 nm its homogeneity. For thinned Nb 3 Sn layers the underlaying Nb shows up as step at 9.2 K, which is used to evaluate the mean thickness of the Nb 3 Sn layer.

Metal ion content of Escherichia coli versus cell age

The potassium, calcium, magnesium, and zinc ion content of cells in exponential and synchronously growing cultures of Escherichia coli B/r was determined with an X-ray fluorescence spectrometer and an atomic absorption spectrophotometer. Cellular potassium, calcium, and magnesium content increased smoothly during the cell cycle, but cellular zinc showed a steplike increase about 10 to 15 min after cell division in a culture having a doubling time of 47 min. The possible role of cellular zinc in the control of cell division is discussed.

Flight-Associated Discharge Pattern in a Weakly Electric Fish, Gnathonemus Petersii (Mormyridae, Teleostei)

AbstractA GnathonEmus petersii which is put into the tank of a Mormyrus rume, or of an electrically silenced G. petersii, displays a discharge rate which is only one fourth (8 Hz) the rate exhibited by an attacking, territory-defending animal. In both instances, the variability of intervals is great. In contrast to the bimodal histogram of an attacking animal, the histogram of an inferior, fleeing fish displays only one mode. This mode is identical to the burst activity-mode of the resting histogram, and different from the swimming histogram mode. So the histogram displayed by an attacked and persecuted animal is significantly different from the histograms exhibited by i) isolated resting, ii) isolated swimming, and iii) attacking fish. During an attack-elicited escape reaction, G. petersii increases its discharge rate up to 55 Hz in a step-like fashion, while regularising the length of successive intervals ("fleeing signal"). The step-like discharge rate increase is also shown by the receiver of an Approach who does not move. This suggests that the step-like discharge rate increase, associated with the escape reaction, is not an incidental response to changed motor activity. The "fleeing signal" presumably is i) an incidental response to a vegetative reaction, or ii) it may have the significance of a signal communicating a socially relevant message (e.g. threat).

Transition period following a nutritional shift-up in the bacterium Escherichia coli B/r : Stable RNA and protein synthesis

The previously observed patterns of stable RNA and protein synthesis during the transition period following a nutritional shift-up are analyzed and described by kinetic equations. (i) The kinetics of the stable RNA synthesis rate after a shift-up are diphasic; the first phase, a step-like increase occurring within minutes after the shift, reflects an induction of rRNA and tRNA transcription; the second phase, an exponential increase with a higher (post-shift) rate constant, reflects a change in the accumulation rate of functioning RNA polymerase. The ratio of the numbers of ribosomes and functioning RNA polymerase molecules is shown to be independent of growth rate or time after the shift. (ii) The protein synthesis rate increases exponentially throughout the transition period with a rate constant corresponding to that of post-shift steady-state growth, which reflects the exponentially increasing number of ribosomes. An initial step-like increase in the protein synthesis rate due to an increase in the ribosome efficiency occurs when the pre-shift growth is below 1·2 doublings/hr. (iii) The duration of the transition period is estimated from the time it takes for the stable RNA to protein ratio to reach its post-shift steady-state value. The period is approximately 3 hr but has no clearly defined end. (iv) When RNA or protein synthesis rates are measured in different units, for example as rate per unit of culture volume, rate per cell or per genome, these differently defined rates change in different patterns after a shift-up. The relationships between these units and the resulting kinetics are explained.

Behaviour of collective volume excitations in aluminum near the 'critical wavevector' (transition into single particle excitation)

From energy loss experiments with 51 keV electrons the dependence of the aluminum plasmon energy on the wavevector q has been derived. The measurements are extended to q>qc=1.3 AA-1 (qc=critical wavevector) and reach q approximately=2.2 AA-1. For q qc, however, the loss energy shows only a weak dependence on the wavevector. The results are compared with calculations of the loss function. Im(- epsilon ( omega ,q)-1), using a dielectric function epsilon ( omega , q) that takes into account finite electron lifetime and local field corrections. It is shown that for large q local field effects have a strong influence. The halfwidth of the loss peak has also been obtained as a function of q. It shows a nearly steplike increase near the critical wavevector.

Die entwicklung des körperschemas bei kindern im alter von 4–10 jahren

(1) Report on the examination of 140 normal, healthy children (70 girls, 70 boys) between 3;6 and 10;6 years of age (7 progressive age-groups) with regard to the development of the body schema. The test procedure included 22 different tasks, some of which had to be solved also with the eyes closed. (2) On vocal command, the most prominent parts of the head, face, trunk and limbs were correctly indicated already at the age of 4 years. Almost all other tested parts of the body were identified between 6 and 7 years. The inner fingers were not correctly localized until the age of 9–10 years. There were no differences in the results, when the identification of analogous parts on the front view of a puppet was required. (3) Right- left-discrimination on the children's own body was acquired at the age of 7. With respect to a puppet facing the children, the answers were given at random between 4 and 5 years, mostly in an egocentric way (P IAGET) between 6 and 7 and increasingly correct beyond the age of 9 years. The performance was not inferior for the execution of crossed commands. When the task demanded right or left turns on the spot, younger children tended to perform a particular “180°-reaction”, probably due to a projection of the right-left coordinates into the space. This reaction occured less frequently when the turns were made while walking. Systematic reversal was relatively rare. It did not correlate with ambidextrousness, lefthandedness or uncertainty as to right-left-discrimination. (4) In various tasks, there was no continuous development in the correctness of pointing to a given part of the body, but rather a step-like increase at 7 or 8 years of age. (5) In agreement with the literature, indication of different fingers (imitating single finger movements of the examiner's or according to a firm touch on the contralateral fingers) was acquired considerably earlier for the thumb and little finger than for the inner fingers. The “match box test” was passed at the age of 5, the “two point finger test” at 7 years, while even some 10 years old children failed to pass the “in between test”. (6) The results are discussed and compared with the data in the literature.

特殊作物の生化學的研究

The authors estimated the redoxpotential, menthol (both free and conjugated) and methone contents of the mint plant during its growth-term from June 10 to September 14, 1944. The curve of redoxpotential changed, drawing higher and lower waves. In the lower parts, of the curve, the mint plant showed the step-like increase of free menthol. In general, enzyme action is more active in the more reductive area of potential than in more oxidative. From this point of view, it is probable that a new esterase is present in the mint plant and menthone is formed-through the menthol-ester by the esterase and dehydrogenases.