Random Polarization Research Articles

Quantum fluctuations and transverse effects in superfluorescence

Superfluorescence[1] (SF) emission profiles are computed using one-way coupled Maxwell-Bloch equations. Transverse effects[2] are included in the full three-spatial-dimension case as well as in the cylindrical-symmetry case. Initiating quantum fluctuations[3–5] are approximated by a random polarization source with a completely random phase and root-mean-square tipping angle of 2/ N, where N is the number of atoms in each volume element. These fluctuations reduce the tail of the output obtained with transverse effects alone[6]. In fact, the fluctuations in output pulse shapes encompass the Cs data of Gibbs, Vrehen and Hikspoors[7]; see Fig. 1. The standard deviation for the delay time is found to be (12.5±4)% for Fresnel number of 0.8 compared with the value (10±2)% recently measured by Vrehen and der Weduwe[8], also for Cs. The Fresnel-number dependence of the standard deviation is shown in Fig. 2; Drummond and Eberly[9] have more extensive results for Fresnel numbers from 1 to 16. Excluded from Fig. 2 were phase-wave[10] fluctuations in which the second peak exceeded the first. Figure 3 shows that the transverse profiles retain little of the on-axis ringing found[2] without fluctuations. Ringing can also be removed by inhomogeneous broadening, but the 32-ns T2* of the Cs experiment has little effect; T2* < 1 ns is needed to eliminate plane-wave ringing[6].

Studying random static polarization of dilute-alloy spin glasses by muon spin relaxation

Zero-field μSR spectra in a spin glass AuFe are analyzed assuming co-existing static and dynamical local fields below Tg, and deduced static polarization of Fe is compared to neutron and susceptibility measurements. We also point out a random static spin polarization in dilute alloys induced by external fields well above Tg.

In vivo identification of Tetrahymena actin probed by DMSO induction of nuclear bundles

We report the first successful identification of actin, an ubiquitous contractile protein, in Tetrahymena pyriformis (strain W). We employed dimethyl sulfoxide (DMSO) as a probe to induce the formation of actin bundles in the cell nucleus [1, 2] through disruption of cytoplasmic microfilament organization [3, 4]. The cells were incubated for 30 min at 22 °C in the inorganic medium of Prescott & James [5] containing 10% DMSO, and observed under a transmission electron microscope (TEM). Microfilarment bundles were formed in interphase macronuclei, and these microfilaments, approx. 6 nm in diameter, could be decorated by rabbit skeletal muscle heavy meromyosin (HMM) in the glycerinated model. In many cases, the bundles formed closely parallel to natively existing bundles of microtubules. Interestingly, these microtubules had prominent striation with 15–16 nm periodicity. SDS-polyacrylamide gel electrophoresis was designed to show the low actin content of Tetrahymena cells in comparison with that of Dictyostelium. Actin was suggested to comprise less than 1.7% of the total protein in Tetrahymena, whereas as much as 6% was actin in Dictyostelium cells. In assessing the physiological significance of the bundle formation, we further performed HMM and myosin subfragment-1 (S1)-binding studies to clarify the organization process and the polarity of the DMSO-induced nuclear actin filaments by using the tannic acid staining technique [6]. Randomly oriented short filaments appeared in the nucleus treated with 10% DMSO for 10 min. These filaments became elongated and associated with each other to form loose bundles in the following 10 min. With 30-min treatment, the filaments were organized and large bundles with single axes developed. With these well-developed bundles, the Student's t-test was performed on 172 pairs of neighboring filaments and the probability ( p) of the deviation from random polarity was 0.08, suggesting that the filaments were organized in an anti-parallel manner. The results show that the DMSO induction of nuclear actin is a powerful tool to demonstrate the existence of cellular actin in vivo and to study the mechanism of microfilament organization in relation to cell physiological activities.

Hydrogen Atoms in Boehmite: A Single Crystal X-Ray Diffraction and Molecular Orbital Study

AbstractThe crystal structure of natural boehmite, AlOOH, from Tveidalen, Langesundsfjorden, Norway, with a = 3.693(1), b = 12.221(2) and c = 2.865(1) Å, was refined from single crystal X-ray diffraction data (MoKα maximum 2θ = 120°) to an Rw value of 0.032 in space groups Amam and A21am. In both cases the proton was found to occupy positions of the type (x, 0.038, 0), where x = 0.104 and 0.396, about 0.75 Å from the donor oxygen atom. This arrangement corresponds to the presence of chains of asymmetric hydrogen bonds with random polarity parallel to the a axis, and indicates that the effective space group is Amam. No significant electron density was observed either at the center (0, 0, 0) or at the position (1/4, y, 0), corresponding to symmetric and bifurcated hydrogen bonds, respectively, between the layers of octahedra.Calculations of the total energy of a representative portion of the boehmite structure as a function of hydroxyl orientation, using semiempirical molecular orbitals of the Hückel type, are in agreement with the observed electron density distribution and suggest a preference for (1) sp3, rather than sp2, hybridization of the donor oxygen atom orbitals, and (2) asymmetric, rather than symmetric hydrogen bonds. Disorder of the hydrogen atom positions within individual hydrogen bond chains is shown to be much less likely than disorder between adjacent fully coherent chains.

The organization of actin filaments in the stereocilia of cochlear hair cells.

Within each tapering stereocilium of the cochlea of the alligator lizard is a bundle of actin filaments with > 3,000 filaments near the tip and only 18-29 filaments at the base where the bundle enters into the cuticular plate; there the filaments splay out as if on the surface of a cone, forming the rootlet. Decoration of the hair cells with subfragment 1 of myosin reveals that all the filaments in the stereocilia, including those that extend into the cuticular plate forming the rootlet, have unidirectional polarity, with the arrowheads pointing towards the cell center. The rest of the cuticular plate is composed of actin filaments that show random polarity, and numerous fine, 30 A filaments that connect the rootlet filaments to each other, to the cuticular plate, and to the membrane. A careful examination of the packing of the actin filaments in the stereocilia by thin sectin and by optical diffraction reveals that the filaments are packed in a paracrystalline array with the crossover points of all the actin helices in hear-perfect register. In transverse sections, the actin filaments are not hexagonally packed but, rather, are arranged in scalloped rows that present a festooned profile. We demonstrated that this profile is a product of the crossbridges by examining serial sections, sections of different thicknesses, and the same stereocilium at two different cutting angles. The filament packing is not altered by fixation in different media, removal of the limiting membrane by detergent extraction, or incubation of extracted hair cells in EGTA, EDTA, and Ca++ and ATP. From our results, we conclude that the stereocilia of the ear, unlike the brush border of intestinal epithelial cells, are not designed to shorten, nor do the filaments appear to slide past one another. In fact, the stereocilium is like a large, rigid structure designed to move as a lever.

Fluctuations in superfluorescence

We show that certain properties of superfluorescent pulses radiated spontaneously by a system of many initially excited two-level atoms can be described by means of the classical Maxwell-Bloch equations. The quantum fluctuations which initiate the pulse are random initial polarizations. The radiated fields which arise from different initial polarization distributions vary significantly from pulse to pulse. Such variations represent quantum uncertainties amplified to the macroscopic level. Probability distributions are calculated for various parameters characterizing the shape of the output pulse as well as the mean and the variance of the radiated intensity.

Discrimination between random signals

Random polarity pulse trains of two states (plus and minus polarity) and of three states (plus and minus polarity and no change at defined clock intervals) were constructed and presented to listeners within forced‐choice discrimination tests. The pulse trains were either of the same average pulse density or were amplitude‐compensated for different pulse densities. Since the long‐term spectrum of such signals is uniform, the most likely discriminable feature is the short‐term spectrum or the temporal patterning of the signals. Successful discrimination is obtained even for pulse trains of extremely high clock frequencies. [Work supported by NSF.]

Trajectories of the reflected and transmitted beams in the oblique tunnel effect

The trajectories of the reflected and transmitted beams in the oblique tunnel effect in optics are studied. It is shown that both beams are parallel displaced away from their commonly accepted geometrical trajectories. When the gap tends to infinite, one obtains the ordinary Goos and Hanchen effect. When the gap goes from infinite to zero, the maximum in the parallel displacements of the reflected and transmitted beams is transferred from critical incidence to grazing incidence. The effect is polarization dependent, so that in the general case of random polarization there will be a splitting of both the transmitted and reflected beams.

Observation of Turbulent Waves in a Helium Plasma by Optical Spectroscopy

Abstract From the combined Stark-Zeeman pattern of helium allowed and forbidden optical lines the frequency spectrum, the field strength and the dominant polarization of microfields were determined in a turbulent plasma. Two frequency domains of oscillations were found in a turbulent heating experiment: low-frequency oscillations with dominant polarization perpendicular to the current direction and high-frequency oscillations (f~fpe) with random polarization. The r.m.s. field strength of the oscillations is between 2 kV/cm and 10 kV/cm. The energy density of turbulent microfields amounts to 1‰ of the thermal energy density.

Binaural masking level differences for pulse train signals of differing interaural correlation.

Binaural masking level differences (BMLDs) were obtained for pulse train signals in a 2IFC task in which the noise (Nπ) level was controlled by a PEST program. The signal in one channel was a random polarity (+1, −1) pulse train composed of 60 100-μsec-duration pulses with an interpulse period of 2 msec. Signal correlation was varied by modifying the signal in the contralateral channel. The correlation was varied by (a) randomly inverting some of the pulses, (b) randomly deleting some of the pulses, (c) deleting or inverting some of the pulses contingent on their polarity, or (d) delaying the pulses by an integral number of pulse periods. The data were compared to predictions generated from Osman's correlation model. Performance was found to be accurately predicted by the model for conditions (a), (b), and (d). Differences between the model and the data for condition (c) were explained in terms of changes in the monaural detectability of the contralateral signal.

Binaural Masking-Level Differences for Pulse Train Signals of Differing Correlation

Three trained observers performed a two-interval forced-choice detection task; the noise level in the earphones was controlled by a PEST program. In all conditions, the noise was equal in amplitude but inverted in phase (Nπ) in the earphones. Signal conditions included Sm, S0, and partially correlated (ρ) or uncorrelated signal waveforms in the contralateral ear. The signal in the ipsilateral channel was always a random pulse train composed of 100-μsec pulses of random (+1 or −1) polarity, with an interpulse period of 2 msec. All signals were low-pass filtered at 5 kHz. The signal conditions included two ρ=0 conditions in which the contralateral signal waveform was identical to the ipsilateral except it (a) had (randomly) half of the pulses reversed in polarity, or (b) was a deterministic signal composed of pulses of all negative polarity; and two ρ=0.5 conditions in which the contralateral signal (c) had (randomly) half of the pulses deleted, or (d) was composed of only the negative polarity pulses in the signal. We also ran ρ=0.75 versions of (a) and (c), and reverse polarity versions of (b) and (d). All the partial and zero ρ conditions resulted in psychometric functions which fell in the 6-dB range between those of NπSm and NπS0. The worst performance was obtained for condition (d).

Influence of the vacuum magnetic moment on the induced radiation of an electron in a plane wave

Expressions are obtained for the probability and intensity of induced radiation from an electron with a vacuum magnetic moment moving in a plane electromagnetic wave of small amplitude. The wave is supposed to be monochromatic and to have random polarization. The results of previous publications on this subject [4–6] are included here as special cases.

Polarization Effects in Fourier Spectroscopy I: Coherency Matrix Representation

A general analytical method using the formalisms of polarization coherency and Jones's matrices is provided for the evaluation of all polarization effects in fourier spectroscopy. The method applies to any incident state of arbitrary (complete, random, or partial) polarization. Inversely, it may also be used for determining the intensity and state of polarization of the source of light. TE- and TM-mode reflectivity and transmissivity for beam splitters and the dependence of these quantities on the incident polarization are obtained. It is demonstrated that three different efficiencies for these optical components must be introduced. Interferometer efficiency expressions for the source beam and the detector beam are also derived and shown to be essentially different from the previous efficiencies. Polarization effects of beam splitters, reflectors, and their composite combinations (interferometers) are investigated in detail. General conditions for complete or restricted polarization compensation are derived. Theoretical SNR expressions for both the source beam and the detector beam are also obtained; these formulas specifically account for the incident state of polarization, the polarization effects of the interferometer, and make use of the exact expressions for the appropriate interferometer efficiency. In an Appendix, a brief comparison is made between some usual representations of the state of wave polarization.

Interaural correlation detection for auditory pulse trains.

Interaural correlation discrimination thresholds were obtained for auditory pulse trains. Pulse trains of random polarity or of random pulse occurrence were delivered to the two ears. The interaural correlation is defined by the pulse-by-pulse agreement between the ears. Coding by pulse occurrence and coding by pulse polarity are about equally effective, except for larger thresholds for polarity at low pulse frequencies. Thresholds for the discrimination of changes in positive interaural correlations are smaller than corresponding thresholds for negative correlations. Interaural correlation discrimination thresholds for pulse trains are comparable to those obtained with wide-band continuous noise.

A microstructure theory of photoelastic behavior in amorphous solids

Available theories to explain the phenomenon of photomechanical behavior in solid materials below the transition temperature are qualitative in nature, and several distinct mechanisms are capable of producing a deformation birefringence. A new mechanism is proposed on the atomic level to account quantitatively for deformation birefringence in an ideal amorphous elastic solid. The material is an isotropic, statistically homogeneous, elastic medium consisting of a random spatial arrangement of heavy mass points (atom nuclei) with positive electric charge in static equilibrium with a corresponding number of continuous, spherical, negatively charged regions (electron clouds). The medium has a nonzero random initial polarization; changes in the components of the dielectric tensor at optical frequencies are computed for infinitesimal uniaxial strain using the Lorentz field approximation for isotropic media. The stress-optical constant is then computed from the associated change in refractive index, and is shown to be in good agreement with experimental values for ordinary photoelastic materials.

Electromagnetic annihilation of a lepton-antilepton pair into a hyperon pair with an account of polarizations and form factors

The annihilation of a lepton-antilepton pair into a pair of $$\bar \Lambda ^0 \sum {^0 } - $$ or $$\Lambda ^0 \bar \sum ^0 - $$ -hyperons is examined. Expressions are found for the differential cross section in the CM system with an account of the strange-particle form factors, and with separate accounts of the random polarization of the initial and final particles.

Polarity, phase and geometry

Following the teaching of the early Bell Telephone Laboratories' experiments in auditory perspective, wide speaker spacing is needed to realize accuracy of geometry. This results in substantially random phase, so that polarity is relatively unimportant. This is supported by Lissajous figures of two-channel stereo signals. It is still good practice, however, to observe polarities, if for no other reason than to permit monophonic reproduction over a stereophonic array. Where the stereo signals contain a strong monophonic component, correct system polarity is better than random polarity. In some stereo situations, bass is improved by correct polarities.

Pitch of a Train of Pulses of Random Polarity

There has recently been considerable discussion of periodicity pitch as opposed to pitch due to spectral energy concentrations. The present investigation deals with a stimulus which appears to display both characteristics in clearly separable form. A train of short evenly spaced pulses was modulated by a noise generator so that the polarity of a given pulse was chosen in a random manner. Since the average power spectrum is approximately flat, it might be expected that the stimulus would have the character of random noise. It is found, however, that the stimulus has a steady pitch-like quality upon which is superimposed an intermittent “chirpiness“ which is definitely tonal. The latter effect is explained in terms of the statistical properties of the short-term power spectrum, but the former seems to be due to the periodicity of the stimulus.