Phase-shifted Patterns Research Articles

Adaptive fringe-locked running hologram in photorefractive crystals: errata

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text Jaime Frejlich, Paulo Magno Garcia, and Lucila Cescato, "Adaptive fringe-locked running hologram in photorefractive crystals: errata," Opt. Lett. 15, 1247-1247 (1990) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

Adaptive fringe-locked running hologram in photorefractive crystals

We have recorded running holograms in a photorefractive crystal with an applied electric field, using a 90 degrees phase-shift fringe-locked interference pattern of light. This method provides a simple way to obtain optimal conditions for nonstationary holographic recording. The experiment that we describe allows us to calculate the crystal diffusion length L(D) and provides direct evidence of the occurrence of running holograms in photorefractive crystals. Experimental results for a Bi(12)SiO(20) sample are reported.

Comparison of Phase Shifts of the Circadian Rhythm of K+ Uptake in Lemna gibba G3 by Various Amino Acid Analogs

Phase shifts of the circadian rhythm of K(+) uptake by Lemna gibba G3, caused by pulse administration of various amino acids analogs, were examined and compared. The various phase shifts were not due to any disturbance in the biosynthesis of amino acids, since the effective time of day and direction of the phase shift caused by analogs were not correlated with the standard amino acid which was modified. Effective analogs could be classified into three groups. The first group was effective during the middle subjective day and caused both advances and delays in phase. The second group was effective early in the subjective night, causing large delays and small phase advance. Analogs in the third group shifted the phase as did cycloheximide and were effective at the subjective dawn. Since the analogs of the third group were known to inhibit protein synthesis, it is likely that they shift the phase by lowering the level of some protein(s) important for the clock. By contrast, since the analogs in groups 1 and 2 are known to generate abnormal proteins, the different phase-shifting patterns caused by analogs in groups 1 and 2 suggest that at least two other proteins are important for the circadian timing loop. The amino acid analogs shift the phase as a result of their incorporation into these proteins instead of the standard amino acid. This probably alters the structure and/or activities of these proteins.

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The circadian patterns of spontaneous seminal emission, sexual activity and penile reflexes in the rat

Spontaneous seminal emission (SSE) by sexually naive and experienced rats occurred almost exclusively in the light period of a 14:10 LD cycle. The circadian pattern of SSE slowly shifted following an LD reversal and was completely reversed by three weeks. The diurnal variation in parameters of sexual activity which are associated with sexual arousal shifted much more readily such that it was reversed within one week of the LD reversal. In contrast, parameters of sexual behavior which are associated with the ejaculatory mechanism were altered following the LD shift with a phase-shifting pattern more similar to that exhibited for SSE, such that the diurnal variation seen before the LD shift was not reestablished until the third week after the shift. The characteristic pattern of SSE in 14:10 LD lighting was disrupted with two weeks of a shift to constant illumination, but the number and weight of spontaneously produced plugs did not change. Finally, there were no differences in any component of the display of penile reflexes by 29 rats tested in the dark period compared to 19 rats tested in the light period, despite significant circadian variation in the copulatory activity of these animals.

Implications of a Spectral IP Survey at Elura

A spectral IP survey was conducted over the Elura orebody by Phoenix Geoph. Ltd. during August, 1979. The results of the survey were that (1) inductive EM coupling due to layering was strongly present from high frequencies down to 1 Hz; (2) a diagnostic phase-shift anomaly pattern due to mineralisation was not evident at low frequencies; and (3) a secondary dispersion due to mineralisation was not evident within the data. The Elura mineralisation is contained within quite barren siltstone, beneath conductive overburden and should, geometrically, constitute a good electrical (conductive and chargeable) target ? as was evidenced by recent time?domain IP surveys. The discrepancy between these two techniques was investigated to ascertain the cause of this ambiguity. 1. The Spectra of EM coupling in the uniform background were analysed to determine the resistivity and thickness of the conductive overburden. The results of this analysis agreed with resistivity sounding data, and was confirmed by forward modelling of the EM coupling spectra; 2. It was noticed that the EM coupling decreased over the mineralisation. Simple subtraction of observed phase responses from the background value, at frequencies from 243 Hz to 3 Hz, produces a positive phase shift anomaly pattern. This pattern is similar to the IP anomaly pattern obtained in the time?domain data; 3. The residual anomaly is believed to be a positive phase EM response due to conductive mineralisation in a less conductive host. Similar responses, but in greater magnitude, have been observed elsewhere in Australia but only recognised in areas of no overburden and generally higher back ground resistivities. A model study by Hohmann (1977), of a conductive target within a less conductive half space, produced similar results. It is concluded that care should be taken in the analysis of spectral IP data in the presence of EM coupling. Analysis using the half-space approximation is not adequate to quantify EM coupling. EM coupling due to a very conductive target can have opposite sign to that for which some theories of spectral interpretation have been developed ? especially analysis in log space. It is essential to record to as low a frequency as possible, and with as high a precision as possible, to obtain data of suitable accuracy for decoupling analysis. It may not be possible to extend the theory of discriminating massive sulphides, from their spectral response, to the field case if the mineralisation is sufficiently conductive and in such a geometry as to produce a positive phase EM coupling response.

Hippocampal theta in rats under urethane: Generators and phase relations

Recordings were made from the directly visualized dorsal hippocampus of urethane-anesthetized rats with silver ball and tungsten microelectrodes. Theta of about 5 c/sec was elicited by reticular stimulation and was located in two broad strata in and subjacent to CA1. A superficial generator yielded 200–250 μV theta from the alveus, stratum oriens and stratum pyramidale; a null-theta and phase-reversal point was located in stratum radiatum; a deep generator yielded 300–500 μV theta in stratum lacunosum-moleculare of the hippocampus and distal stratum moleculare of the dentate gyrus, with maximum amplitude near the fissure. No theta was found in CA3. Cross-correlation analyses between generators yielded coefficients on the order of —0.80 while within a generator — especially the deep one — coefficients could reach +0.95. Phase analyses showed the two generators were about 180° out of phase, with the deep generator leading. Septotemporal movement along the upper generator yielded no phase shifts; similar movement along the deep generator showed slight leading in septal portions. Subiculofimbrial movement in both generators showed a complex pattern of phase shifts: generally, subicular sites led fimbrial sites, but an inversion of 10°–20° occurred in the millimeter anterior to the center of the hippocampus. Anatomical, phase and other data led to consideration of a possible retrohippocampal role in supplementing the well-known pacemaker in the medial septum.

Nuclear magnetic resonance in liquid copper alloys

Abstract The 63Cu nuclear magnetic resonance has been observed in liquid copper alloys containing small proportions of Au, Ag, Zn, Ga, Ge, As, Se and Ni. In each case the line width appeared unaffected, while the line centre exhibited a displacement proportional to the solute concentration. For the positive valence solutes, the observed Knight shift change produced by unit solute concentration varied systematically with solute valence in a way markedly similar to the changes observed in solid silver based solutions. The experimental results may be explained as due to the redistribution of electronic charge necessary to screen the solute ion potential. It is shown that the pattern of phase shifts which offers the best explanation of the results is plausible on physical grounds. The viewpoint developed here for interpreting the results for monovalent solvents also appears to be useful when discussing the Knight shift in polyvalent systems.