Value Of Po Research Articles

Frozen‐flux upper limits to the magnitudes of geomagnetic Gauss coefficients, based on MAGSAT observations

If the earth's core is regarded as a perfect conductor and the surrounding mantle as an insulator, then the unsigned magnetic flux, Po, crossing the core‐mantle boundary remains constant in time. In practice this constancy is limited by the core's finite conductivity, but it is expected to hold for at least millenia. For such time spans an upper limit Gnm or Hnm may be derived for the magnitude of any geomagnetic Gauss coefficient gnm or hnm, by assuming that the entire value of Po is attributed to that coefficient alone. Such upper limits are evaluated here for n = 1 ‐ 4, using a value of Po derived from Magsat data.The ratio |gnm/Gnm|, |hnm/Hnm| between the observed magnitude of a coefficient and its upper limit defines a "relative multipole index" for the present value of that coefficient. Using the Magsat model MGST 6/80 it is found that for the dipole term this ratio is about 0.72, suggesting that |g10| is presently only about 28% lower than the maximum value during the past few millenia. Also, the largest of the other multipole indices calculated (|g3¹/G3¹| ≃ 0.23) is a factor of over 3 smaller, so presumably a dramatic change in field configuration outside the core is required before the next polarity reversal is completed.

The Effects of Preionization Level on a ?Stabilized? Z-pinch

The influence of the degree of preionization on the formation and properties of a conventional 'stabilized' Z-pinch has been studied experimentally for preionization levels ranging from 2 % to 35 %. It is concluded that there exists the possibility of using varying levels of preionization to tailor radial profiles of density and pressure, and hence to influence the value of Po.

The enhancement of the alkaline Bohr effect of some fish hemoglobins with adenosine triphosphate

The oxygen equilibria of the hemoglobins of one holostean fish, the spotted gar ( Lepisosteus osculatus), and of four teleost fish, the carpsucker ( Carpiodes carpio), the small mouth buffalo fish ( Ictiobus bubalus), the Rio Grande cichlid ( Cichlasoma cyanoguttatum), and the redear sunfish ( Lepomis microlophus), have been measured as a function of pH in the presence and absence of ATP. The oxygen equilibria of the teleost hemoglobins in the presence of 200 μ m ATP can be superimposed within experimental error upon the data obtained in the absence of ATP by a simple downward shift of the pH scale by 0.5 unit. Thus the effects of proton and ATP binding appear equivalent: Both can be interpreted in terms of a two-state allosteric model in which binding occurs preferentially to the low-affinity T-state. The oxygen affinities of each of the teleost hemoglobins approach asymptotically a maximal value at high pH. Although these high affinities are associated with decreased cooperativity of oxygen binding, as reflected by the Hill coefficient n, the asymptotic value of n never appears lower than 1.2 to 1.4. This indicates that the data cannot be completely described in terms of a single high-affinity R-state in alkaline solution: At least two different conformations are required. The oxygen affinity of the spotted gar hemoglobin, like that of each of the teleost hemoglobins, reaches a maximal value (minimal value of log PO 2 for half-saturation) above pH 8, but unlike teleost hemoglobins, the Hill coefficient reaches maximal values of 2.6 to 2.7 at high pH. The data in the absence of ATP are superimposable on the data in its presence by a downward shift of the pH scale by 0.25 unit. The measurement of the Bohr effect ( Δlog P 30 ΔpH ) in the presence and absence of ATP shows that the Bohr effect in each of the hemoglobins is substantially enhanced by organic phosphates, as it is in mammalian hemoglobins. The extent of the enhancement of the Bohr effect by 200 μ m ATP for each of the hemoglobins is approximately the same in the range pH 6.7 to 7.3 (increase in Δlog P 50 ΔpH ~ 0.3 ). This is a direct consequence of the equivalence of the linked-function relationship to the effects of ATP and proton binding on oxygenation.

Placental blood flows and oxygen transfer during uterine contractions: A mathematical model

Theoretical calculations have been performed on the effects of changes in intrauterine pressure on maternal and fetal placental blood flows and pressures and transplacental O 2 exchange. Initial conditions and contraction profiles may be “assumed normal” or abnormal. The model predicts that the fetal O 2 deficit is most sensitive to the maximum intensity of the contraction and maternal mean arterial blood pressure, less sensitive to the duration of the contraction and far less sensitive to the value of maternal arterial PO 2. The umbilical venous PO 2 falls to a minimum at the peak of a contraction. Its level is most sensitive to contraction intensity and maternal blood pressure; while the value of maternal arterial PO 2 has less effect and the duration of contraction has essentially no effect. There is interaction between factors so that the effect of simultaneous changes is not necessarily in proportion to the effects of individual changes.

Study on Extrusion Process of Hard Shale Mud

A crushed hard shale mixed with flocculating or dispersing aqueous solutions and ram-extruded, obeyed the expression P=Poe-K(φ-φo), where P was the pressure which initiated extrusion, φ was the volume fraction of liquid, and Po and k were constants. For size fractions having five different particle sizes, plot of logP against φ converged on common points, coordinates logPo and φo, irrespective of the flocculation or dispersion of the system. The slopes -K were less for flocculated than for dispersed particles. At φ=φo each particles contact with one another directly and the effect of the liquid at the contact point can be ignored, because φo can be considered that the void fraction at most closely packed. Under the above consideration, the interaction force at the contact point of particles fp can be calculated using the value of Po. The values of fp obtained from the Po agreed with the adhesion force of venous inorganic particles.

Permeation of water through bilayer lipid membranes

This paper, the fourth of a series, is concerned with the movement of water across the bilayer lipid membrane (BLM). The water permeability coefficients, Po, were determined for BLM formed from oxidized cholesterol, cholesterol-DAP (dodecyl acid phosphate), and cholesterol-HDTAB (hexadecyltrimethylammonium bromide). When NaCl was used as the solute, the value of Po for oxidized cholesterol membranes was found to be 8.4 ± 0.5 × 10−4 cm/sec at 22.5°C. In either NaI or CsCl solution, however, the value of Po was found to be about three times larger. The temperature dependence of Po for BLM generated from oxidized cholesterol in n-octane was also measured in the range of 22.5–44.0°C. Experimental activation energy was calculated to be 6.8 ± 0.5 kcal/mole. From the temperature-permeability coefficient data, various derived quantities from absolute reaction rate theory have been evaluated. The nature of pathway for water permeation and the factors governing the rate of water transport across the BLM are discussed in terms of the transition state theory. The results of this study suggest that the bifacial region of the membrane plays an important role in water permeability. During the last few years, a new experimental structure of less than 90 A thick has been extensively investigated. This membranous structure in aqueous solution known variously as bimolecular, bilayer, or black lipid membrane (abbreviated as BLM), possesses some of the properties of the biological membrane. These properties include thickness, certain electrical characteristics, bifacial tension, ionic selectivity, and water permeability. A detailed summary of the studies on BLM together with the relevant literature references may be found in a recent publication (1). In this paper we report the results of measurements of the osmotic permeability coefficient of water across BLM formed from various lipid solutions. Previously, the permeability coefficients of BLM have been measured by several groups of investigators (2–7). The values reported vary from 4.9–104 μ/sec. It is not certain from these studies whether this large discrepancy is due to the difference in the experimental techniques or the composition of the lipid solutions used for BLM formation or both. Our measurements with the BLM generated from various lipid solutions should therefore be of some interest. Regarding the mechanism of water permeation through the BLM, it is generally recognized that only a very limited amount of information can be derived from measurements of water permeability coefficient at a single temperature. Hence there is an obvious need to carry out studies at various temperatures. Further, one would like to raise the question of the nature of the interfacial region (i.e., the zone near the solution/membrane interface) upon the water permeability. Therefore, we have measured the permeability coefficients of water through the BLM as a function of (a) the temperature and (b) the ionic composition of the bathing medium. The permeability-temperature data permit an evaluation of the various derived quantities from the absolute reaction rate theory, from which certain speculations concerning the mechanism of water permeation through the BLM are now possible. The permeability coefficient data determined as a function of solute used provide an opportunity to examine the effect of ions on water permeation and possibly on the structure of the BLM/solution interface.

Models for the Density and Elasticity of the Earth's Lower Core

Summary The possibility of lowering the estimated central density po of the Earth below the value of order 15g/cm3 arrived at in a previous paper has been examined in some detail, with the continued use of Bolt’s seismic P velocity distribution for the core. It has been shown po can be as low as 12.6g/cm3 if suitable ad hoc assuinptions, compatible with the seismic data, are made on the variations of the incompressibility k and rigidity p in the lower core. The value of po could be further lowered to 12.3g/cm3 (in agreement with much earlier calculations) if the region E” were chemically homogeneous, but this is improbable. Seven model representations, all compatible with the recent seismic data and closely concerned with the value of po, are presented of the variation with depth of p (the density), k, p, and related properties, in the lower core. The models exhibit the consequences of particular assumptions on k and p, as well as on po, and provide a basis for important immediate inferences and for constructing whole Earth models. A number of interesting conclusions can be drawn if evidence presented by Birch that po < 13 be accepted. The first is that there must be rigidity, decreasing with increase of depth, in a substantial part of the volume occupied by the regions F and G. The formal calculations would require this to occur in both F and G, and so give rise to the suggestion that the Earth’s core contains a second solid layer F outside the inner core G. Although the margin of probability favouring this suggestion is as yet fairly slender because of various background certainties, the suggestion receives some support on other grounds. Strong new support is provided for the long-standing inference that the inner core is solid, and the requirement of decreasing rigidity with depth throughout much of the lower core is also strongly indicated. The calculations imply that complete absence of rigidity in the Earth’s core would require a central density of at least 14.7 g/cm3.

融解ビスマス-融解塩系における諸元素の挙動, (I)

Distribution of Mg, Sr, Sc, La, Gd, Cr, Mo, W, Mn, Tc, Fe, Co, Pt, Cu, Ag, Zn, Cd, In, Sn, Sb, Te and Po between fused bismuth and fused LiCl-KCl (eutectic) was investigated at 550°C in argon atmosphere.Twenty grams of pure bismuth were added to 20 g of the fused salt containing a trace amount of the element above mentioned. After the salt was contacted with bismuth for 4 hr, 1 day, 2 days and 4 days at 550°C, about 1 g of each layer was sampled and partition coefficients [K=concentration in salt (ppm)/concentration in bismuth (ppm)] were calculated. Then the similar experiment, in which the pure salt was added to the bismuth containing a trace amount of the element, was tried.In the former and the latter experiments, K values approached to the same value with the lapse of time. These values are as follows: Mn; 105, Fe;>20, Co;>300, Cu;7, Ag;0.05, Zn;>2, 000, Cd;>1, 500, which are considered to be distribution coefficients, i.e., partition coefficients in equivalent states.On the other elements except Po, distribution coefficients were estimated from K values obtained in the former or the latter experiment. These values are as follows: Mg;>400, Sr;>870, Sc;>190, La;>105, Gd;>2, 000, Cr;>2, 000, Mo;>12, 700, W;>18, 000, Tc;<0.08, Pt;<0.003, In;>9, Sn;<0.6, Sb;<0.003, Te;<0.05.K value of Po was 0.1 after 5 hr contacting.The relation between distribution coefficient of each element and free energy of formation of the chloride of the metal was discussed.

Synchronization of Telemetry Codes

A well-known means of efficiently transmitting information over the continuous white Gaussian channel involves the encoding of successive blocks of data into sequences of binary digits (called code words). Efficient decoding of these sequences in turn necessitates a knowledge of the instants in time at which one code word ends and the succeeding word begins. This paper presents a method for obtaining this synchronization which neither decreases the channel capacity nor increases the complexity of the encoding equipment. The method is to select, from the many encodings which are equally good for purposes of synchronous operation, that encoding for which the maximum absolute value of the correlation po between any code word and any sequence formed from the overlap of two code words is a minimum. Thus a large correlation is observed only in the synchronous phase position. This technique is applied to an important class of block codes, the binary orthogonal codes. An algorithm for constructing these codes with the desired self-synchronizing properties is presented, and upper bounds on the value of po are thereby established.