Values Of ΔF Research Articles

The polarization effect in LiNbO3 crystals

The results of measurements of the magnitude of the polarization effect are given for longitudinally vibrating bars of LiNbO3 crystal. When a dc electric field was applied to the vibrating bars the maximum values of the relative frequency change Δf/(fΔE) observed exceeds 10-10 V-1m.

Ear dominance for pitch is not a result of binaural diplacusis or selective attention

It has been suggested that the phenomenon of ear dominance for pitch [E. W. Yund and R. Efron, J. Acoust. Soc. Am. 62, 607–617 (1977)] might be a manifestation of binaural diplacusis and/or selective attention. To test the first possibility, we first measured each subject's diplacusis and then measured his ear dominance with dichotic stimuli in which the frequencies of the tones were chosen to exactly compensate for his binaural diplacusis. Subjects showed essentially the same ear dominance for these diplacusis‐compensated dichotic tone pairs as they had for similar stimuli without any diplacusis correction. Thus, the ear dominance in these subjects was not due to their binaural diplacusis. To test the second possibility, that ear dominance is due to selective attention, we performed the ear dominance experiments with (diplacusis‐compensated) dichotic tone pairs having such a small frequency difference (Δf) that the subject could not discriminate these from binaural pure tones. Subjects showed the same ear dominance for dichotic tone pairs with these small values of Δf as they had for tone pairs with larger values of Δf. With larger Δf's, where two pitch components can be heard, it could be argued that the subject might selectively attend to one component. However, at small Δf's, where the dichotic stimuli are indiscriminable from binaural pure tones, selective attention cannot account for ear dominance.

Frequency discrimination with single and multiple observations

In a “same-different” psychophysical task three experienced listeners discriminated changes in frequency (Δf) that occurred in either of the following stimulus conditions: (1) a single 80- or 160-ms, 1.0-kHz tone burst; (2) in the first or in the second of two successive 80-ms, 1.0-kHz tones separated by intertone intervals of 5, 10, 20, 60, 100, or 150 ms; and (3) in both of the two successive tones described under (2). All stimulus conditions occurred randomly within each block of trials and training proceeded until performance reached asymptote. In the first condition, the value of Δf (d′ = 2.0) was ≈4.0 Hz regardless of tonal duration. For the second condition, the Δf in the first tone required for d′ = 2.0 ranged from 8 to 12 Hz, and that in the second tone ranged from 5 to 7 Hz, depending on the intertone interval. In the third condition the values of Δf (d′ = 2.0) were generally smaller than any of those of the second condition, but still larger than the √ d′ prediction for two independent observations. It appears that within the temporal intervals and experimental conditions of this study, the improvement in performance that is predicted with multiple observations is partly cancelled by temporal interferences that occur between the observations. [Supported by NRC Postdoctoral Fellowship to the author.]

INTERACTION OF <i>N</i>-METHYLPYRROLIDONE WITH AZOBENZENE: THE EFFECT OF INORGANIC SALTS

The interaction of N-methylpyrrolidone with azobenzene in aqueous solutions containing 1 mol/l NaCl, LiCl, NaClO4 and NaSCN has been investigated by means of the solubility measurement of azobenzene. The thermodynamic parameters for the process which consists of the transfer of 1 mole azobenzene from the salt solution to the salt solution containing 6 mol/l N-methylpyrrolidone have been calculated. In the presence of the inorganic salts, the values of ΔF°u-trans were negative. However, the contributions of enthalpy and entropy changes to the free energy change of the process varied with the salt species. It was shown that in the presence of a water structure-breaking salt such as NaClO4 or NaSCN, the value of ΔH°trans was negative and ΔS°u-trans was positive, whereas in the presence of a water structure-making salt such as NaCl or LiCl, the value of Δ°trans was nearly zero and ΔS°u-trans was positive. These facts were interpreted in terms of hydrophobic interactions between the non-polar parts of azobenzene and N-methylpyrrolidone.

Integration of duration and frequency cues in discrimination between pure tones

The acoustic cues that underlie discrimination of complex sounds (e.g., speech) are often multidimensional and sequential (i.e., not all the dimensions vary at the same time). In this work we explored whether the information provided by the various dimensions can be integrated to improve discrimination, for the case of cues consisting of a change in duration followed by a change in frequency. The procedure was a same‐different discrimination between pairs of tones. Each pair consisted of two 80‐ms, 1500‐Hz tone bursts separated by a 60‐ms interval. For the “different” trials, the comparison pair contained increments in the duration (Δt) of the first tone and/or in the frequency (Δf) of the second tone. For various values of Δt, the value of Δf required to maintain a constant performance level was measured, and vice versa. A tradeoff between the values of Δt and Δf required for d′ = 2.0 was observed, suggesting that the effects of the two dimensions were integrated. The tradeoff was most prominent when the increments in duration and frequency were matched in terms of their discriminability. The results are compared with the prediction that d′Δt+Δf = [dΔt′2 + dΔf′2]1/2. [Work supported by NINCDS.]

Thermodynamics of binding of methyl orange and its homologs by poly(vinylpyrrolidone): The effect of inorganic electrolytes

AbstractThe extent of binding of methyl orange, ethyl orange, propyl orange, and butyl orange by poly(vinylpyrrolidone) has been measured in aqueous solutions of inorganic electrolytes such as NaCl, LiCl, NaSCN, and NaClO4 by an equilibrium dialysis method. The effect of the salts on the first binding constants and the thermodynamic functions which are accompanied by the dye—polymer association process was investigated relative to the corresponding values in the absence of such salts. It was found that in aqueous solutions of NaCl and LiCl the enthalpy change accompanying the binding is small and the largest contribution to the free energy of binding is from the positive entropy gain. For NaSCN and NaClO4, the values of ΔF° and ΔH° were both large and negative and the value of ΔS° was small and negative. Thus, the favorable free energy for the complex formation was due entirely to the negative enthalpy term. These characteristics of the thermodynamic quantities are discussed in terms of changes in structural properties of water in the vicinity of the binding entities and conformational changes of the polymer to which the dye is bound due to the added foreign electrolytes.

The determination of X‐ray dispersion corrections from measurements of X‐ray linear absorption coefficients

AbstractThe X‐ray linear absorption coefficients have been measured for the alkali halides LiF, NaF, and NaCl using characteristic radiations ranging from SnKα1 to CrKα1. From these measurements values of the imaginary part Δf″ and the real part Δf′ of the X‐ray dispersion correction have been deduced for each atomic species. A comparison is made with the values of μ/ϱ, Δf′, and Δf″, which have been calculated by Cromer and Liberman using relativistic quantum mechanics.

Temporal acuity as a function of frequency difference.

Several experiments are reported relating to the temporal resolving power of the auditory system. The experimental task was to discriminate between the two signals generated when a waveform was played either forward or backward in time (a condition in which the two signals have identical energy spectra). A two‐segment waveform of total duration T was generated. The first T/2 segment was a sinusoid of one frequency and the second T/2 segment was a sinusoid of a different frequency. Each trial contained two observation intervals. In one interval the frequency change was from high to low, in the other interval low to high. As the total duration decreases discrimination becomes more difficult. It is nearly perfect for durations as short as 2 msec when the frequency of one segment is 1000 Hz and the other frequency 2000 Hz (ΔF=1000 Hz). For smaller values of ΔF, even at very short durations (4 msec), discrimination is about like that obtained in a simple frequency discrimination experiment.

Factors in the discrimination of tonal patterns. I. Component frequency, temporal position, and silent intervals.

Factors which determine the discriminability of tonal sequences, or patterns, were investigated in five experiments. The patterns were generally sequences of ten 40-msec tonal components, which ranged in frequency from 256 to 900 Hz, or from 500 to 1500 Hz, in equi-log intervals. Highly trained (15 to 60 h of training prior to collecting experimental data) listeners’ abilities to detect changes in the frequency of single tonal components in these patterns were measured using a same–different psychophysical method. The just-detectable values of Δf (d′=1.0) were only slightly larger than for single 40-msec tones presented in isolation for tonal components at the end of the temporal sequences (a ’’recency’’ effect). Performance was systematically worse for earlier components, the just-detectable Δf increasing by four to five times from the end of the pattern to the beginning (no ’’primacy’’ effect). The ’’recency’’ effect was interpreted as a matter of later arriving components interfering with frequency resolution for earlier ones, since a brief silent period (80 to 120 msec) following an early component led to as precise discrimination for that early component as for the last one in the sequence. The higher-frequency components in a given pattern were resolved much more accurately than the lower-frequency components for patterns with overall bandwidths of 250 to 900 Hz and also when the bandwidths were raised from 500 to 1500 Hz. Subject Classification: 65.22, 65.75, 65.64.

The measurement of anomalous scattering near the GaKabsorption edge in GaP

By the use of an SSD diffractometer and continuous X-rays, the energy dependences of Δf' and Δf” values of Ga have been studied on GaP with energy resolution of about several eV around the Ga K edge; the values of Δf” were determined by the measurement of the absorption coefficient, and then the values of Δf' have been obtained from the precisely measured ratio of Friedel-pair reflexions from a (111) single-crystal plate of polar GaP. Fine structures have been found in Δf” and therefore in Δf' corresponding to those of the absorption coefficient. The present work has shown that the measured values of Δf' more or less reasonably agree with the curves calculated from the dispersion relation.

Auditory attention as a major factor in the discrimination of tonal sequences

In two recent experiments we described the discriminability of acoustic patterns consisting of ten 40-msec tonal components played in sequence, as measured with a same-different psychophysical method. Listeners can readily discriminate two such patterns when the only difference is in the frequency of one of the ten tonal components, although values of the just-detectible Δf increase by as much as an order of magnitude for early components as compared to later ones and for lower as compared to higher frequency components. In a new procedure listeners attempted to match the patterns by controlling the frequency of a single tonal component. They were able to routinely adjust that frequency within ± 10 Hz of its value in a standard pattern (which was presented in alternating sequence with the pattern in which they controlled the frequency of one component), although ± 60- to 100-Hz values of Δf had been required for the same patterns to be discriminated in the same-different procedure. Possible interpretations of this result are that the adjustment procedure enables extremely precise focusing of auditory attention, and that the site of intrapattern interference is more centrally located than previously suspected. [Supported by Grant No. 03856, National Institute of Neurological Diseases and Stroke, Department of Health, Education and Welfare.]

Consequences of parameter learning in experiments on immediate auditory memory

In a recent paper we described the decay of auditory memory for patterns consisting of ten 40-msec tones played in sequence. On each trial, one of 50 permutations of a ten-tone catalog was played, and then it was repeated either with or without a frequency increment (Δf) added to one of the ten tonal components. The interval between the two patterns was varied from 0.5 to 32 sec. The frequency increments became only slightly less detectible as the interstimulus interval was lengthened (just-detectible values of Δf increased by about 1/3). In a new experiment, the same highly trained listeners were able to make almost as precise discriminations without a standard present on each trial. When the patterns consisted of ten-tone sequences drawn from a 1000-tone catalog the listeners could no longer perform at better-than-chance levels in the remembered-standard conditions. The results begin to establish the limits of listeners' ability to learn the parameters of a catalog from which acoustic stimuli are sampled. [Supported by Grant No. NS03856, National Institute of Neurological Diseases and Stroke, Department of Health, Education and Welfare.]

Polarization of two-photon excited fluorescence

The problem of the polarization dependence of molecular fluorescence excited by simultaneous absorption of two different photons is solved exactly for the case of randomly oriented molecules which do not rotate between the absorption and emission acts. It is found that seven molecular parameters are available from such a study, including the relative values of the critical parameters δF, δG, and δH which characterize the symmetry of the two-photon excited state. The results are compared with another author's study of this problem, which concluded that only five parameters were measureable.

Electrochemical studies of copper lactate and glycollate complexes at the mercury cathode

Polarographic studies of the copper complexes formed with lactic and glycollic acids have been undertaken using water and mixtures of water and organic solvents. The stability constants have been determined. The effects of pH, concentration of ligand, non-aqueous solvents and surface-active substances have also been investigated. The values of ΔH, ΔF and ΔS have been calculated.

Thermal denaturation of Delphinus delphis ferrimyoglobin derivatives in alkaline pH region

A comparative investigation of the effective thermodynamic parameters of some ferri-derivatives of Black Sea dolphin Delphinus delphis myoglobin is presented. Studies on the absorbance changes with temperature in the Soret region of aqueous myoglobin solutions are carried out. The transitions fit the “two-state” theory when aggregation and irreversibility are removed. The pH dependence of the association of buffer protons is studied. The results show that thermally denatured protein undergoes a conformational transition at pH 10–11. The steepness of this transition depends on the nature of the ligand and is maximal in the case of the azide derivative. Most likely the “distal” histidine E-7 takes part in this process; its protonization depends directly on the protonization of the ligand. The pH dependence of the temperature of denaturation is investigated. The changes of ΔH′ and ΔS′ are proportional in all cases; this “effect of compensation” (Tc = 360–370°K) demonstrates the important role of the hydrate “jacket” in the stabilization of the native structure. The values of ΔFD°(T) (from thermal denaturation) and ΔFu(cM) (from unfolding in water-urea solutions) do not coincide. This fact is due either to the difference between the two end states (native and denatured) or to the dependence of the thermodynamic parameters on temperature. Nevertheless, ΔF changes proportionally in both cases.

Effect of temperature and salt concentration on the synergetic extraction of uranyl ion

Abstract The effect of temperature on the synergetic extraction of uranyl ion with thenoyl trifluoroacetone (HTTA) and neutral donors has been investigated by distribution measurements in the system UO 2 /HTTA/ S [ S = trioctyl phosphine oxide (TOPO), tributyl phosphate (TBP), dibenzyl sulphoxide (DBSO) and diphenyl sulphoxide (DPSO)] at various temperatures. Results indicate that the distribution coefficient falls by 20–30 per cent for a 10°C rise in temperature of the system whereas, it remains virtually the same for extraction by HTTA alone. Values of ΔF, ΔH and ΔS in the temperature range of 30°–70°C for the various systems seem to indicate that the greater stability of UO 2 (TTA) 2 TOPO is derived from the enthalpy and entropy factors. The effect of salt concentration in the aqueous phase on the extraction of the species UO 2 (TTA) 2 S has also been studied by distribution measurements in the above system in the presence of varying concentrations of the perchlorates of lithium, sodium and ammonium. As expected, the distribution coefficient increases with increase in salt concentration in the aqueous phase. The increased extraction in the presence of lithium perchlorate can be correlated with its larger hydrated ionic radius.

X-ray determination of polarity sense by anomalous scattering at an absorption edge

A technique is described for the determination of crystallographic polarity which is generally applicable to large polar crystals containing an element heavier than K. It is an extension and simplification of Cole & Stemple's method in which the intensities diffracted by (00 l) and (00\overline l) planes are compared at wavelengths close to an absorption edge of a constituent element. A definitive polarity determination may now be made without previously measuring or assuming values of Δf′ and Δf′′ at the edge.

Conformational isomerization in hexahydro-s-triazines and hexahydropyrimidines

Abstract The thermodynamic activation parameters have been determined for a series of hexahydro-s-triazines, 1,3-dimethylhexahydropyrimidine and its methyl iodide salt using NMR to determine the rate constants for chair-to-chair isomerization. Values of Ea, vo, ΔF‡, ΔH‡, and ΔS‡ are reported. Both steric and electronic effects are investigated and their influences on the activation parameters and reaction paths discussed.

Surface viscosity of monomolecular films of n-long chain alcohols at various temperatures and pressures

The surface viscosity of monomolecular films of n-long chain alcohols, viz., C16-OH, C18-OH, C20-OH, and C22-OH was studied as a function of surface pressure (2–40 dynes/era.), temperature (15–30°C.), and shear rate (0.12–1.8) using a rotational viscometer. The transition pressures observed for the two-dimensional phase changes, i.e., from the liquid condensed (Lc) to an intermediate (I) or to a liquid-solid (LS) state are in agreement with those found in the π-A isotherm studies. The LS phase has been shown to be stable for a compound at a particular temperature range. The supermobile character of the film may be attributed to association between film molecules themselves through hydrogen bonding, which causes weak adhesion to water molecules in the subphase. Activation energy for viscous flow and relaxation time have been determined at the Lc → I or Lc → LS transition pressures and at different temperatures. Values of ΔF obtained agree well with the literature values.

HEATS OF ASSOCIATION OF AQUEOUS COPPER, NICKEL, AND COBALT IONS WITH HALIDE IONS

Calorimetric measurements are reported for the heats of formation of CoCl+, NiCl+, CuCl+, CoBr+, NiBr+, and CuBr+ from simple aqueous ions. Values of ΔF, ΔH, and ΔS for these reactions at 25 and 40 °C, and an ionic strength of 2.0 were found. It was noted that ΔH and ΔS seem to be related by the equation: ΔH = 254ΔS + 201, for values at both temperatures.