Values Of Kx Research Articles

Turbulent spectrum analysis in TFR tokamak plasmas

Low frequency turbulence in TFR has been studied over a wide range of parameters and under many experimental conditions and a modelling of the frequency spectrum is presented. The main results are as follows. In ohmic discharges the turbulent spectrum is peaked around Kx approximately 5 cm-1 (Kperpendicular to rho i approximately 0.6) and decreases monotonically for both larger and smaller values of Kx. The decrease for small Kx values is particularly severe. No single linear dispersion relation is possible but, rather, a large domain of phase velocities is covered by the most intense waves. During auxiliary ICRF heating experiments, there is an increase of the level of turbulence which is proportional to the square root of RF power. Finally a strong increase in the turbulence after minor and major disruptions is observed.

Horizontal diffusivity in a small, ice‐covered lake1

A horizontal eddy diffusivity (Kx) value of 0.47 cm2 · s‒1 was calculated from tracer cloud expansion data from a previous experiment in which a 24Na solution was introduced as a point source under ice cover in Tub Lake, Wisconsin. This Kx value, the first from a lake where surface wind stress was not a factor, is lower than any lake Kx previously reported. The constancy of Kx found for the 48‐h period of monitoring implied mixing eddy lengths <1.6 m, the diffusion cloud size found at first monitoring. Surface seiches or convective flows appeared to be probable sources of mixing energy.

Acidobasic properties of molten potassium tetrahalogenogallates (X=Cl, I)

Molten potassium tetrachlorogallate and potassium tetraiodogallate were studied in terms of halogenoacidity, based on X − ion-exchange. Titration of KX solution with GaX 3 were achieved and characterized by the shift of cathodic voltammetric curves. Autodissociation constants K i,X/mol 2 kg −1 were determined: −log K i,Cl=4.25±0.05 and −log K i,I=2.6±0.05, as well as the solubility values of KX: 0.41±0.02 and 0.80±0.02 mol kg −1 for KCl and KI respectively.

D-glucose and D-gluconate transport in vesicles from Pseudomonas putida.

Vesicles prepared from glucose-grown cells of Pseudomonas putida (ATCC, 12633) retain glucose oxidase (GOX) and gluconate dehydrogenase (GADH) activity and actively transport D-glucose, 2-deoxy-D-glucose (2DOG), 3-deoxy-3-fluoro-D-glucose (3FG), and D-gluconate by saturable processes. The transport of these substrates is stimulated by the addition of L-malate or reduced phenazine methosulphate (PMS). Vesicles prepared from succinate-grown cells of P. putida lose their capacity to transport D-glucose, 2DOG, and 3FG by a saturable process. The transport and accumulation of D-gluconate, however, is retained with a KX value of 65 microM and a Vmax of 1.0 nmol . mg protein-1 . min-1. The rate of D-gluconate transport is stimulated by the addition of reduced PMS of L-malate with a reduction in the KX value to 42.0 microM. Respirometric studies with these vesicles indicate the presence of an active GOX and L-malate dehydrogenase but a defective GADH. Thus a reductase activity is detected in the presence of D-gluconate and either 2,6-dichloroindophenol (DCIP) or ferricyanide, as measured by a decrease in absorbance at 500 and 420 nm, respectively. Measurements on these vesicles with the oxygen electrode, however, indicate that no electron transfer from GADH to oxygen occurs. This is in contrast to the results with glucose-grown vesicles or with L-malate or D-glucose as substrates in the succinate-grown vesicles. A comparison between glucose and gluconate oxidase activity in native and detergent-treated vesicles is made. The significance of these results in relation to the presence of a glucose carrier in P. putida and other pseudomonads is presented.

Mixed complexes, formed by rare-earth elements with im inodiacetic and citric acids

1. The stability constants KX of the mixed complexes of composition LnZCit2− were determined by the pH-metric titration method. The KX values decrease from Nd to Gd and from Ho to Lu. 2. The polydentate ligands of iminodiacetic acid and H3Cit are compatible in the coordination sphere of the ion of the REE.

Mixing Character of Glass-melting Tank for Container Manufacturing

Mixing function of glass-melting tank is of most important for obtaining high homogeneity of glass. It was assumed that the mixing process developing in glass tank is a kind of diffusion process which is caused by mixing action mainly resulting from thermal and mechanical currents. A fundamental differential equation involving the “mixing diffusion coefficients”, kx, was proposed for discussing the mixing charater of a given tank.The numerical value of kx could be computed by applying a few practical values such as the dimension of tank, the axial mean velocity of glass flow and the time spent till the tracer concentration gets a maximum, Tmax, to an equation obtained one of the solutions of the differential equation mentioned above.Variation of any physical value of glass pulled out during operation is characteristically affected by the values of kx and pull rate imposed on the tank. Hence, the featuer of the physical value-time curve is characterized by kx and Tmax as the factors dominantly controlling the mixing effect of glass tank, which gives some fruitful suggestions concerning the mixing character of the tank.

Effects of salts of metals on vinyl polymerization. Part 4.—Polymerization of styrene in presence of cupric chloride

The AIBN-initiated polymerization of styrene in the presence of cupric chloride and 20% by volume DMF has been studied at 50, 60 and 70°C. The salt behaves as an ideal inhibitor, i.e., the post-inhibition rate is not significantly different from the rate obtained in the absence of inhibitor. The rate constants for the decomposition of AIBN into “accessible” free radicals, obtained from plots of inhibition period against cupric chloride concentration are 2.22 × 10–6, 1.04 × 10–5, 6.0 × 10–4 sec–1 at 50, 60 and 70°C respectively. The Arrhenius activation energy based on these data is 36.5±2 kcal mole–1. From a study of the acceleration period following inhibition the ratio kx/kp, where kx is the rate constant for the reaction between polystyryl radicals and the cupric salt, has been evaluated at each of the temperatures quoted. The value of kx thus obtained at 60°C is 1.81 × 106 1. mole–1 sec–1, which is an order of magnitude greater than that for the corresponding reaction with ferric chloride in DMF.

Effects of salts of metals on vinyl polymerization. Part 3.—Polymerization of acrylonitrile in presence of cupric chloride

The homogeneous polymerization of acrylonitrile initiated with 1,1′-azo-bis-isobutyronitrile and inhibited with cupric chloride in dimethylformamide solution has been studied at 60°C. The rate of polymerization following the inhibition period was invariably less than the rate obtained in the absence of cupric chloride, and varied inversely with the initial cupric chloride concentration for concentrations >3 × 10–3 M. The corrected value of the rate constant for the initiation reaction obtained from the inhibition against time plot was 1.51 × 10–5 sec–1. The plot of the final retarded rate of polymerization against the reciprocal of the initial cupric chloride concentration gave a corrected value of 5.7 for ky/kp where ky is the rate constant for the reaction between growing polymer radicals and the inhibition product (presumably cuprous chloride). The value of kx/kp, where kx is the rate constant for the reaction between polyacrylonitrile radicals and cupric chloride, was determined from the period of acceleration following complete inhibition, and had a mean value of 100 at 60°C. Using a value of 1930 l. mole–1 sec–1 for kp at 60°C we obtain values of 1.93 × 105 and 1.1 × 104 l. mole–1 sec–1 for kx and ky respectively. The value of kx is much greater than the corresponding value obtained with ferric chloride, and is approaching the order of magnitude of rate constants for radical-radical interactions as for methyl methacrylate polymerization.

On the General Theory of Surface States and Scattering of Electrons in Solids

In discussing the existence of surface states of electrons in solids or the scattering at a plane of discontinuity, it is necessary to match the wave function at the boundary plane, taken as the plane x = 0, using an infinite set of solutions of the Schr?dinger equation in the solid. The solutions must all have the same energy E and the same ky and kz, but will have different values of kx, which may be complex. The formal structure of the energy is therefore considered, when viewed as a complex function E of the complex variable kx, and in particular the form of the lines along which E becomes real. This leads to some discussion about setting up approximate wave functions for surface states, differences between one, two and three dimensions, the energy of surface states relative to that of the Bloch bands, and the correction of a conclusion drawn by Goodwin in 1939.

Polymerization inhibition by aromatic compounds

AbstractA quantiative study of chain transfer and inhibition reactions makes it possible to determine the ratios kx/Kp where Kp and kx are the rate coefficients for propagation and for chain tranfer, respectively. Since the absolute values of the constants Kp are known for a number of monomers it is possible to determine the absolute values of the constants kx. We have investigated the inhibiting action of some types of aromatic compounds in the polymerization of vinyl acetate, methyl acrylate, acrylonitrile, and methyl methacrylate. In the polymerization of vinyl acetate the inhibiting effect of the aromatic hydrocarbons increases in the order: toluene, diphenyl, naphthalene, phenanthrene, anthracene. The logarithm of kx is linearly related to the logarithm of the methyl affinity. The inhibiting effect increases on incorporating substituents, both electrondonating and electron‐accepting, in the benzene ring. There is no relation, however, between the value of kx and Hammet's σ‐constant. An outstanding position is assumed by nitrobenzene, for which kx is higher by 3–4 orders of magnitude than that of the other substituted benzenes. The incorporation of substitutents in the meta and para positions of the benzene ring follows the Hammet rule, the electron‐donating substituents causing a decrease in the kx values. Similar relations are observed in the polymerization of methyl acrylate, but the absolute values of kx are lower by 3–4 orders of magnitude than in the polymerization of vinyl acetate. Because of this, under the experimental conditions the interaction of the polymethyl acrylate radical with molecules of the transier agent was not revealed (kx < 0.21 1./mole‐sec. at 50°) in the case of many of the substances investigated, for instance of all mono‐substituted benzenes except nitrobenzene. A comparison of the kx values for polyvinyl acetate, polymethyl acrylate, polymethyl methacrylate, and acrylonitrile radicals permits a number of conclusions to be made concerning the influence of the polar factor on radical reactions. The data obtained lead to definite conclusions as to the inhibiting mechanism of aromatic compounds. The primary act is the addition of the polymer radical to the aromatic ring with the formation of a nonreactive radical. In the case of nitro compounds, the polymer radical reacts with the nitro group, probably by transferring to it a β‐hydrogen atom. It has been found that in the polymerization of vinyl acetate in the presence of the inhibitors in question each molecule of the latter terminates two kinetic chains; regeneration of the chains does not take place, and the polymer molecules form as the result of disproportionation between the polymer radical and the radical formed during interaction of the former with the inhibitor molecule.

On the Mechanism of Ball Mill Grinding

In the previous report4), we suggested that the grindability or the rate of grinding of particles was closely connected with the size distribution pattern of the ground material, which ranged from the bulk crushing to the surface grinding. We assumed, also, that the size distribution of the ground material was affected by the strength of grinding force.This paper is intended to verify the above-mentioned assumption by means of the ball-mill grinding, which is the most general operation pattern comprizing factors we can easily vary.Silica balls with four different diameters (and naturally of different weights) and sintercorund balls with one diameter were respectively employed at various rotational speeds of the mill. To investigate the results of the experiment, we assumed the characteristic number of β, which indicates a characteristic of the size distribution relative to the ratio of cumulative weight percent of the coarse part (Y(r)to that of the fine part (Y(f)). (Cf. Fig. 4).When the ball weight or the speed of rotation increased, (or the grinding force increased), β also increased as shown in Eq. 4-2 and Figs. 8 and 9. The values of kβ and kx were closely related to the particle diameters, viz., when the fed particles were small, the effect of grinding force was small.From this we may conclude that in fine grinding, the weight of a ball does not count much.It was observed that in general the grinding rate of particle (X) was determined by the grindability of particle (Γ) and the mechanical efficiency of grinding (ηm), which is the probability of ball impact or that of other grinding forces. Therefore, in fine grinding, Γ becomes negligible, and ηm essential.Upon this, we assumed that ηm (or impact number per one rotation of the mill) was constant irrespective of the speed of rotation of the mill, and obtained by experiment the relative values of ηm as shown in Fig. 10.Furthermore, according to H.E. Rose's suggestion9), from the supposed contact area of a couple of balls and probability of impact of balls in the mill., we derived relative efficiency of ball impact, as shown in Eq. 5-13, and ascertained the experimental results and Eq. 5-13, as shown in Fig. 17.