Sharp Value Research Articles

Spontaneous inactivation of the Ca 2+-sensitive K + channels of human red cells at high intracellular Ca 2+ activity

Ionophore A23187-mediated Ca 2+-induced oscillations in the conductance of the Ca 2+-sensitive K + channels of human red cells were monitored with ion specific electrodes. The membrane potential was continuously reflected in CCCP-mediated pH changes in the buffer-free medium, changes in extracellular K + activity were followed with a K +-selective electrode, and changes in the intracellular concentration of ionized calcium were calculated on the basis of cellular 45Ca content. An increased cellular 45Ca content at the successive minima of the oscillations where the K + channels are closed indicates that the activation of the channels might be a ( dCa 2+/ dt)- sensitive process and that accommodation to enhanced levels of intracellular free calcium may occur. An incipient inactivation of the K + channels at intracellular ionized calcium levels of about 10 μM and a concurrent membrane potential of about −65 mV was observed. At a membrane potential of about −70 mV and an intracellular concentration of about 2·10 −4M no inactivation of K + channels took place. Inactivation of the K + channels is suggested to be a compound function of the intracellular level of free calcium and the membrane potential. The observed sharp peak values in cellular 45Ca content support the notion that a necessary component of the oscillatory system is a Ca 2+ pump operating with a significant delay in the activation/inactivation process in response to changes in cellular concentration of ionized calcium.

Probabilistic model for deep inelastic reactions

Due to transport phenomena in the interaction region, the dynamical variables in deep inelastic collision do not have sharp values at the end of the interaction. In the present model, they are considered as random variables with Gaussian probabilities centered on the classical results, while the Coulomb dynamics outside the interaction domain is treated exactly. Very simple formulas are obtained for multiple-differential cross-sections. Numerical results applied to the “quasi-fission” products of the reaction84Kr(525 MeV)+209Bi agree fairly well with experimental data.

Finite-Larmor-radius stabilization of the m = 2 instability in the Isar T1-B high-beta stellarator

The m = 2 mode stability is investigated in the ISAR T1-B toroidal high-beta stellarator (major diameter 2.7 m, capacitor bank energy 0.5 or 1.5 MJ) for a great variety of plasma parameters using deuterium filling gas (0.5 < ωL · τii < 200; 0.1 < rL/a < 0.35; ωL = ion Larmor frequency; rL = ion Larmor radius; a = plasma radius; τii = ion self-collision time). The ion mass dependence was checked by a small number of discharges with hydrogen. For rL/a < ηcrit, ηcrit = 0.14, fast-growing m = 2 modes were found, the limit ηcrit being essentially independent of the collision frequency within the accessible range (2 ≲ ωL · τii ≲ 20). For rL/a > 0.14 no fast-growing m = 2 modes were observed, the plasma lifetime being limited by a m = 1, k ≈ 0 mode. The normalized growth rate, γ̃ = γ/(Vi/a) = 0.15 ± 0.05, (Vi = ion thermal speed) was about half the sharp boundary value and slightly higher than that calculated for a diffuse pressure profile. The experimentally determined minimum value of rL/a, for which the m = 2 mode is stabilized, is by about a factor of three smaller than Freidberg's estimation using a sharp-boundary Vlasov model. Advanced calculations in a sharp boundary model by Lewis and Turner deviate in the critical limit only by a factor of about 1.5 and recent results using a diffuse pressure profile by Herrnegger and Schneider and by Freidberg and Hewett agree quite well with the experimental data.

Studies on artificial coal. 2. Thermogravimetry, plastometry and differential thermal analysis

The artificial coals (AC) or coal models were prepared from sawdust, lignite and cork by the method of hydrothermal carbonification. The specific techniques used to study their pyrolytic behaviour were thermogravimetry, Gieseler plastometry and differential thermal analysis (DTA). The principal conclusions drawn are: 1. (1) The initial stage of pyrolysis of AC can be considered to be governed by an overall reaction of first order, as in the case of natural coals. 2. (2) All caking types of AC showed quite low softening points (75–210 °C), the values for sawdust AC being lower than those for the cork AC. The latter showed fairly sharp peak values of the temperature of maximum fluidity, but the sawdust AC showed only a range of temperatures of maximum fluidity, the upper limit being less than the maximum fluidity temperature of the cork AC. However the temperatures of resolidification were consistently high, namely 425 °C and above, thus bringing in a significant point of similarity with natural caking coals. 3. (3) The value of maximum fluidity was very high for one AC sample, exceeding 27000 dial div./min. Such a high value is rare for natural caking coals. With the latter, no correlation could be observed between the caking properties and maximum fluidity. Hence the role played by the stability of the plastic mass may be the more dominant factor in the caking process. 4. (4) From the comparison of the softening temperatures and the temperatures of active decomposition of the AC, it is inferred that the process of initial softening of coal may be physical in nature. 5. (5) The AC indicated an overwhelming exothermicity in their primary pyrolysis, thus behaving like the natural coals studied under similar experimental conditions.

On a quantum mechanical model for a maser I

AbstractThe model is closely connected with a model by Lamb and Scully (10). Atoms described as two-level systems, initially in an incoherent superposition of the two levels, interact successively during a time T with an electromagnetic field of which only one mode is taken into consideration. In the limit as infinitely many atoms have interacted, it is shown that the field either approaches a thermal distribution or is excited to arbitrarily high Photon numbers according to whether or not the lower level of the atoms is initially more probable than the upper level. It is also shown that in any case the correlations between pure Photon number states converge to 0. If the atoms are initially in the upper level it is proved that the Photon number grows roughly as the square root of the number of atoms that have interacted. Throughout the discussion number-theoretical properties of T play a disturbing role. The last mentioned result in fact depends on a sharp (but arbitrary) value for T and is therefore disqualified for physical interpretation.

Projection of the uhf ground state wave function of the high-conductivity 1 ∶ 1 TCNQ salts

The unrestricted Hartree-Fock ground state wave function of a TCNQ salt with one electron per molecule and with the regular one-dimensional lattice of the TCNQ molecules is decomposed into states with sharp values of the total momentum of the electronic system. The properties of the components are discussed and the relation of the results to the double periodicity of the well known spin wave spectrum is emphasized.

Minimal-disturbance measurement as a specification in von Neumann's quantal theory of measurement

In von Neumann's theory an incomplete observableA is measured by measuring any complete observableB whose functionA is. This procedure is narrowed down in this paper by the additional requirement of preservation of the sharp value of any observable compatible withA. The requirement is shown to be equivalent to the unique change of state:ρ → (trρPn)−1PnρPn (Pn is the eigenprojector ofA corresponding to the obtained eigenvaluean, ρ is the statistical operator of the initial state, and by assumption trρPn > 0). This characterises the minimal-disturbance measurement. A necessary and sufficient condition is derived for the selection of the above observableB so that its measurement implies the minimal-disturbance measurement ofA. For arbitraryρ andA, there exists aB satisfying the condition. Hence, this constitutes a reasonable specification within von Neumann's theory, reducing the latter to the physically preferable minimal-disturbance measurement theory.

The Spin Spectrum of an Unstable Particle

A state vector (vector-valued distribution) of an unstable particle can be a 3-momentum eigenvector in at most one inertial frame as a consequence of the necessary width of the energy spectrum. We investigate this frame dependence of momentum eigenvectors of unstable particles and demonstrate that: (i) It is compatible with the principle of relativity. (ii) It leads to a distinction between two ways of defining the spin of the particle which are equivalent for stable particles. (iii) One definition, called kinematical spin, yields a precise value, and is determined by considerations of detailed balancing and other means of counting the degeneracy of the momentum eigenvectors. (iv) The second definition, called dynamical spin, need not yield a sharp value, is determined by the dynamics of the decay process, and is measured by observing angular distributions of decay products. It is shown that an unstable particle with vanishing kinematical spin (pion) may have a small admixture of non-isotropic angular distribution of unpolarized decay products in the rest frame of the decay products. The order of magnitude of the effect is estimated and the coupling between the mass and spin spectrum is studied in the case of local interactions without derivative coupling.

RESPONSES OF RECTANGULAR RESONATORS TO OCEAN WAVE SPECTRA.

The paper describes a method to tune a resonator accurately to eliminate those bandwidths in the incident wave spectra that cause range action and high mooring forces, unreasonable wave forces and wave overtopping, and the drift of littoral sediments into the harbor. Using maximum attainable values of reflectivity, minimum values of transmissivity and approximate sharpness of the resonance, an approximate method is devised for estimating the performance of resonators, assuming a linear system.

On Certain Discrete Inequalities involving Partial Sums

Our aim in this paper is to prove inequalities of the form1or2for all real values of the parameters α, β and all non-negative (in some cases all positive) xi. Obviously, an is finite in all cases, and we shall show that An is finite if α and α + β are both non-negative. In all cases, we obtain sharp values of the constants an, An (when finite), as well as bounds for these constants, and their behaviour as n → ∞. In case a &lt; 0, we naturally consider only positive xi, otherwise the xi may be non-negative. Although we always write xi ≧ 0 in the following, this should be read as xi &gt; 0 in case α &lt; 0; similar remarks apply to the parameter t introduced below.

REALIZATION OF SHARP CUT‐OFF FREQUENCY CHARACTERISTICS ON DIGITAL COMPUTERS*

AbstractIn Part I of this paper, we examined the properties of the best mean square approximation to the sharp cut‐off frequency characteristic by an impulse response of finite length. It was found that the sharpness of cut‐off for the resulting frequency characteristic depended on the length of the impulse response–but because of the discontinuous nature of the specified frequency characteristic, this best mean square approximation always had a maximum overshoot of ± 9%, independent of the length of the impulse response (Gibbs phenomenon).In Part II, we investigate ways of reducing this ± 9% overshoot at the expense of a reduced sharpness of cut‐off. The discontinuous frequency characteristic is first approximated by a continuous characteristic with linear or cosine frequency tapering. The impulse response for such tapered characteristics consists of the impulse response of the discontinuous frequency characteristic weighted by a certain function corresponding to the type of tapering employed. The best mean square approximation to the tapered characteristic by an impulse response of finite length M will produce a frequency characteristic whose properties are now dependent on the time‐band width product Mζ, where 2ζ is the tapering range.A trade‐off exists between the maximum overshoot and the sharpness of cut‐off for the resulting characteristic for both forms of frequency tapering. Instead of considering other forms of tapering in the frequency domain, we now investigate arbitrarily chosen weighting functions in the time domain to determine the minimum length of impulse response for a minimum value of maximum overshoot and a maximum value of sharpness of cut‐off.Part III will discuss the digital realization of the above finite length impulse responses together with the optimum partially specified digital filter approximation to the desired frequency characteristic.

Assessment of sharpness and over-all picture quality by different psychometric methods.

In recent years psychometric methods have been used to determine the quality of photographic reproduction. In this paper results are presented of a study undertaken to intercompare the merits of different psychometric methods. A few photographic reproductions were rated with respect to sharpness and over-all picture quality using three different methods. The results also show how closely the sharpness values correspond to over-all picture-quality values.

Sharpness Calculations for 8mm Systems

Crane's objective method for rating picture sharpness, SMT acutance (system modulation transfer acutance), has been applied to systems for producing small-format color prints. Although calculated sharpness values agreed well with experimental results, the way in which changes in format affected these values was unclear. A systematic investigation of the relationship between size of format and SMT acutance for original films and print films showed that changes in format were equivalent to changes in film-sharpness characteristics for the stages involved. Computational analyses of model systems are used to illustrate the usefulness of sharpness calculations in estimating the sharpness potential of a given color system. Such calculations can also aid in planning system improvements.

STUDIES ON A FEW FACTORS OF PRINTING PASTES FOR BLOTCH METHOD

On Blotch Method by machine printing specially among the printing methods using Vat dyestuffs, a few factors were measured in order to find the following: (1) Physical properties of printing pastes. (2) The influence of these properties on the result of printing, That is, on printing pastes for Blotch Method which uses all kinds of thickener, their viscosity, spinnability, sharpness, levelness and colour value, fixed value, fixed percentage etc. of the prints steamed in Flash Ager were measured.The results obtained are as follows:1) As printing pastes for Blotch Method, wheat starch, Sodium alginate and Schisa are suitable.2) Single thickener which excels from every point of view does not exist.3) As mixed printing pastes for Blotch method, mixture of Wheat starch and Sodium alginate are excellent.

Subjective Sharpness of Simulated Color Television Pictures

This paper describes a visual experiment in which the observed variable is the subjective sharpness of a color picture. The picture is produced by the superposition of primary color images from three projectors. The test picture corresponds, in general sharpness, to the grades of pictures that might be produced by existing or contemplated color television systems. The projectors are operated out of focus to achieve the moderate sharpness values required. The amount of defocus of each projector is expressed in equivalent television band width as part of the calibration. Many different ways of dividing up band width among the three primary colors are explored in determining the variation of picture sharpness.

The Subjective Sharpness of Simulated Color Television Pictures

This paper describes a visual experiment in which the observed variable is the subjective sharpness of a color picture. The picture is produced by the superposition of primary color images from three projectors. The test picture corresponds, in general sharpness, to the grade of picture that might be produced by existing or contemplated color television systems. The projectors are operated out of focus to achieve the moderate sharpness values required. The amount of defocus of each projector is expressed in equivalent television bandwidth as part of the calibration. Many different ways of dividing up bandwidth among the three primary colors are explored in determining the variation of picture sharpness.

On the Development of the Compound Nucleus Model

The cross sections of certain nuclear reactions, as functions of energy, show sharp maxima and low values between the maxima, thus exhibiting a great similarity to line spectra. The compound nucleus theory was originally designed to explain this structure and to describe the corresponding nuclear reactions. After a brief description of the picture which the compound nucleus theory presents for these reactions, the story of the extension of the theory to describe a wide variety of reactions is presented. This includes an outline of the mathematical concepts which the extended theory uses. The last part of the article deals with the connection between the so-called principle of causality, which expresses the fact that the scattered particle wave cannot leave the nucleus before the incident particle wave has reached it, and the formulas of the generalized compound nucleus theory.

Psychometric Evaluation of the Sharpness of Photographic Reproductions

Psychometric methods were used to evaluate the relative sharpness of a number of photographic reproductions in which sharpness was the only significant variable. Since sharpness is an observer's subjective impression of an aspect of picture definition, the methods for deriving sharpness values involve introspective processes and methods of quantifying these subjective impressions. Although no physical measurements of any aspect of the stimulus are involved in deriving sharpness values by the psychometric method, repeated evaluations showed that the scale values obtained are a reliable indication of the sharpness attribute of a photographic reproduction. Three methods of quantifying the judgment data were used, and the sharpness ratings obtained from all three were in good agreement with one another. Projected transparencies gave substantially the same results as paper enlargements. Attempts to correlate the sharpness ratings with physical measurements of some aspect of the developed image were not entirely successful; neither resolving power nor simple density relationships across an abrupt boundary between light and dark areas resulted in satisfactory correlations with sharpness ratings.

Psychometric Evaluation of the Sharpness of Photographic Reproductions*

Psychometric methods were used to evaluate the relative sharpness of a number of photographic reproductions in which sharpness was the only significant variable. Since sharpness is an observer’s subjective impression of an aspect of picture definition, the methods for deriving sharpness values involve introspective processes and methods of quantifying these subjective impressions. Although no physical measurements of any aspect of the stimulus are involved in deriving sharpness values by the psychometric method, repeated evaluations showed that the scale values obtained are a reliable indication of the sharpness attribute of a photographic reproduction. Three methods of quantifying the judgment data were used, and the sharpness ratings obtained from all three were in good agreement with one another. Projected transparencies gave. substantially the same results as paper enlargements. Attempts to correlate the sharpness ratings with physical measurements of some aspect of the developed image were not entirely successful; neither resolving power nor simple density relationships across an abrupt boundary between light and dark areas resulted in satisfactory correlations with sharpness ratings.

Diffusion of Heat Through a Rectangular Bar and the Cooling and Insulating Effect of Fins. I. The Steady State

Exact solutions for temperature distribution and heat flow through a rectangular fin are rederived in more general and simple form than previously given. These are studied numerically and graphically and shown to yield new results not contained in the approximate formulas hitherto used. Except for the factor of thermal conductivity of the fin material, the cooling effect is a function only of the height-width ratio β of the fin, and of a dimensionless ``relative boundary resistivity'' μ governing the heat loss to the environment. It is shown that, for any value of this boundary resistivity, there is a fairly sharp optimum value of the height-width ratio beyond which further increase in height will not lead to much improvement in cooling effect. This optimum β decreases with decreasing μ until, at a certain critical value μ* in the neighborhood of 1, it becomes zero. At the critical μ*, the cooling effect is altogether independent of β, and the presence of the fin is a matter of indifference. Below μ*, the cooling effect decreases with increasing β, so that the presence of the fin serves merely to insulate the hot plate. This analysis of a single fin is the basis upon which a study of the conditions for optimal cooling by an array of fins will be carried out in a subsequent publication.