Eikonal method for calculation of coherence functions

A method is presented for computing the cross-spectral density of a special class of partially coherent fields in which the coherent modes obey an eikonal equation. This method allows for statistical analysis of optical systems based on simple ray tracing.     

Near-field diffractive elements

A novel near-field imaging system is proposed and simulated. It is seen that a significant improvement in performance in the presence of noise is possible without loss of resolution.     

Factors influencing the ultrasonic separation of oil-in-water emulsions

Ultrasound may have inherent shortcomings that preclude its ability to coagulate grease from wastewater, yet these may be overcome by the simultaneous application of electrolysis. We studied the role of pH, conductivity, temperature, ultrasound intensity and duration, and electrolysis voltage, current, and duration, in the study treatment. Conductivity was found to be the most significant factor, however interactions among the eight study variables are likely more important than individual factors. The proposed process was capable of removing up to 100% of grease from the studied wastewater.     

New diffusion-edited NMR experiments to expedite the dereplication of known compounds from natural product mixtures

[reaction: see text] We present two new diffusion-edited NMR experiments, improved DECODES and HETDECODES, that sort the constituents in a mixture by their individual diffusion coefficients. These experiments should allow the partial NMR spectral assignment and cursory structure elucidation of compounds in a complex mixture as an aid in the dereplication of known or nuisance compounds.     

The missing mass squared dependence of the average charged particle multiplicity in the reaction K+p → KoX++ from 5–16 GeV/c

The average charged particle multiplicity, 〈n_ch(M_X²)〉, in the reaction K⁺p→K^oX⁺⁺ is studied as a function of the mass squared, M_X², of the recoil system X and also as a function of the K^o transverse momentum, p_T, at incident momenta of 5.0, 8.2 and 16.0 GeV/c. The complete data samples yield distributions which are not independent of c.m. energy squared, s, They exhibit a linear dependence on log (M_X²_X/M_o²)[M_o²=1 GeV²] with a change in slope occurring for M_X²≈s/2, and do not agree with the corresponding distributions of 〈n_ch〉 as a function of s for K⁺ p inelastic scattering. Sub-samples of the data for which K^o production via beam fragmentation, central production and target fragmentation are expected to be the dominant mechanisms show that, within error, the distribution of 〈n_ch(M_X²)〉 versus M_X² is independent of incident momentum for each sub-sample separately. In particular in the beam fragmentation region the 〈n_ch(M_X²)〉 versus M_X² distribution agrees rather well with that of 〈n_ch〉 versus s for inelastic K⁺p interactions. The latter result agrees with recent results on the reactions pp → pX and π^?p → pX in the NAL energy range. Evidence is presented for the presence of different production mechanisms in these separate regions.     

Strengths of ozone fundamentals in the infrared: Variational calculations

Strengths are calculated for the fundamental vibration-rotation bands of ozone in the infrared adopting a variational method of vibration-rotation analysis. These calculations make use of available ab initio electronic theory to assign algebraic signs for the coefficients in the dipole moment expansion to internal coordinates. Magnitudes of these coefficients are chosen so that they are consistent with available vibrational intensity data.     

Observation of a narrow hyperon state of mass 3.17 GeV

We present evidence for a narrow Y¹ with a mass of 3.17 GeV and a width ? 20 MeV decaying to ΣKK? + pions, ΛKK? + pions and ΞK + pions. The data come from two high statistics K^?p bubble chamber experiments with a sensitivity of ≈100 eV/μbat 8.25 GeV/c and ≈ 45 eV/μbat 6.5 GeV/c.     

Dynamic response of a two degree of freedom spherical system in a fluid

Summary The steady state and transient response of a two degree of freedom spherical system immersed in a viscous fluid medium, initially at rest, is investigated with the inclusion of the fluid reaction derived by Basset in the differential equations of motion. In the steady state study, phase angle and amplitude ratio curves are presented from which the mode shapes of the system, for wide ranges of density ratio, frequency ratio and Stokes number, can be obtained. In the investigation of transient response, the system is subjected to impulsive base displacements and the equations of motion are solved numerically. The response curves obtained illustrate the effect of each dimensionless parameter on the dynamic behavior of the system.

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Übersicht Es wird das stationäre Verhalten und das Einschwingen eines kugelförmigen Systems von zwei Freiheitsgraden untersucht, das sich in einer viskosen Flüssigkeit befindet und anfänglich in Ruhe ist. In den Bewegungsgleichungen werden die von Basset abgeleiteten Reaktionskräfte der Flüssigkeit berücksichtigt. Für das stationäre Verhalten werden Amplituden- und Phasen-Kurven angegeben, aus denen die Schwingungsformen für einen weiten Bereich von Dichteverhältnis, Frequenzverhältnis und Stokes'scher Zahl erhalten werden können. Das Einschwingverhalten wird numerisch errechnet, wobei das System als durch Stöße an der Basis erregt angenommen wird. Die erhaltenen Einschwingkurven zeigen den Einfluß der dimensionslos gemachten Parameter auf das dynamische Verhalten des Systems.

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The research on which this paper is based was supported in part by The National Science Foundation under Grant Nos. GK 479 and GP 2094 to Northwestern University. Acknowledgment is also given to the Northwestern University Computing Center and the National Science Foundation whose funds aided in the establishment of the Center.     

Quantifying the implications of nonlinear cochlear tuning for auditory-filter estimates

The relation between auditory filters estimated from psychophysical methods and peripheral tuning was evaluated using a computational auditory-nerve (AN) model that included many of the response properties associated with nonlinear cochlear tuning. The phenomenological AN model included the effects of dynamic level-dependent tuning, compression, and suppression on the responses of high-, medium-, and low-spontaneous-rate AN fibers. Signal detection theory was used to evaluate psychophysical performance limits imposed by the random nature of AN discharges and by random-noise stimuli. The power-spectrum model of masking was used to estimate psychophysical auditory filters from predicted AN-model detection thresholds for a tone signal in fixed-level notched-noise maskers. Results demonstrate that the role of suppression in broadening peripheral tuning in response to the noise masker has implications for the interpretation of psychophysical auditory-filter estimates. Specifically, the estimated psychophysical auditory-filter equivalent-rectangular bandwidths (ERBs) that were derived from the nonlinear AN model with suppression always overestimated the ERBs of the low-level peripheral model filters. Further, this effect was larger for an 8-kHz signal than for a 2-kHz signal, suggesting a potential characteristic-frequency (CF) dependent bias in psychophysical estimates of auditory filters due to the increase in strength of cochlear nonlinearity with increases in CF.     

Rate and timing cues associated with the cochlear amplifier: level discrimination based on monaural cross-frequency coincidence detection.

The perceptual significance of the cochlear amplifier was evaluated by predicting level-discrimination performance based on stochastic auditory-nerve (AN) activity. Performance was calculated for three models of processing: the optimal all-information processor (based on discharge times), the optimal rate-place processor (based on discharge counts), and a monaural coincidence-based processor that uses a non-optimal combination of rate and temporal information. An analytical AN model included compressive magnitude and level-dependent-phase responses associated with the cochlear amplifier, and high-, medium-, and low-spontaneous-rate (SR) fibers with characteristic frequencies (CFs) spanning the AN population. The relative contributions of nonlinear magnitude and nonlinear phase responses to level encoding were compared by using four versions of the model, which included and excluded the nonlinear gain and phase responses in all possible combinations. Nonlinear basilar-membrane (BM) phase responses are robustly encoded in near-CF AN fibers at low frequencies. Strongly compressive BM responses at high frequencies near CF interact with the high thresholds of low-SR AN fibers to produce large dynamic ranges. Coincidence performance based on a narrow range of AN CFs was robust across a wide dynamic range at both low and high frequencies, and matched human performance levels. Coincidence performance based on all CFs demonstrated the "near-miss" to Weber's law at low frequencies and the high-frequency "mid-level bump." Monaural coincidence detection is a physiologically realistic mechanism that is extremely general in that it can utilize AN information (average-rate, synchrony, and nonlinear-phase cues) from all SR groups.