Phase-shifting Properties Research Articles

Role of the thalamic intergeniculate leaflet and its 5-HT afferences in the chronobiological properties of 8-OH-DPAT and triazolam in Syrian hamster

The 5-HT 1A/7 receptor agonist 8-hydroxy-2-[di- n-propylamino]-tetralin (8-OH-DPAT) has chronobiological effects on the circadian system and, in the Syrian hamster, it is known that serotonergic (5-HT) projections connecting the median raphe nucleus to the suprachiasmatic nuclei (SCN) of the hypothalamus are a prerequisite for the expression of 8-OH-DPAT-induced phase advance of locomotor activity rhythm. We examined the possible involvement of the thalamic intergeniculate leaflet (IGL) in the phase-shifting properties of 8-OH-DPAT injections at CT7. Bilateral electrolytic lesions of the IGL blocked phase-shift responses to 8-OH-DPAT of the activity rhythm. Phase changes induced by injections of 8-OH-DPAT at CT7 and triazolam (Tz), a short-acting benzodiazepine, at CT6 were also studied after bilateral chemical lesion of the 5-HT fibres connecting the dorsal raphe nucleus (DR) to IGL. Destruction of 5-HT fibres within the IGL blocked the phase-shift response to Tz, but not the phase-shift response to 8-OH-DPAT. In conclusion, (a) IGL is essential for the phase-shifting effect of peripheral 8-OH-DPAT injections; (b) 5-HT fibres connecting DR to IGL are necessary for the expression of the phase-shifting effect of Tz but not of 8-OH-DPAT.

Faraday quantum clock and nonlocal photon pair correlations

We study the use of the Faraday effect as a quantum clock for measuring traversal times of evanescent photons through magneto-refractive structures. The Faraday effect acts both as a phase-shifter and as a filter for circular polarizations. Only measurements based on the Faraday phase-shift properties are relevant to the traversal time measurements. The Faraday polarization filtering may cause the loss of non-local (Einstein-Podolsky-Rosen) two-photon correlations, but this loss can be avoided without sacrificing the clock accuracy. We show that a mechanism of destructive interference between consecutive paths is responsible for superluminal traversal times measured by the clock.

Fermionic one-loop corrections to soliton energies in 1+1 dimensions

We demonstrate an unambiguous and robust method for computing fermionic corrections to the energies of classical background field configurations. We consider the particular case of a sequence of background field configurations that interpolates continuously between the trivial vacuum and a widely separated soliton/antisoliton pair in 1+1 dimensions. Working in the continuum, we use phase shifts, the Born approximation, and Levinson's theorem to avoid ambiguities of renormalization procedure and boundary conditions. We carry out the calculation analytically at both ends of the interpolation and numerically in between, and show how the relevant physical quantities very continuously. In the process, we elucidate properties of the fermionic phase shifts and zero-modes.

Neuropeptide Y blocks serotonergic phase shifts of the suprachiasmatic circadian clock in vitro

The mammalian circadian pacemaker in the suprachiasmatic nuclei (SCN) can be reset in vitro by various neurochemical stimuli. This study investigated the phase-shifting properties of neuropeptide Y (NPY) and serotonin (5-HT) agonists when applied alone, as well as their combined effects on clock resetting. These neurotransmitters have both been shown to advance the SCN clock in vitro when applied during the daytime. By monitoring the SCN neuronal activity rhythm in vitro, I first confirm that the 5HT 1A/5HT 7 agonist (+)DPAT maximally advances the SCN clock when applied at zeitgeber time 6 (ZT6). Conversely, NPY only phase advances the neuronal activity rhythm when applied at ZT 10. This effect occurs through stimulation of Y 2 receptors. NPY, again acting through Y 2 receptors, blocks (+)DPAT-induced phase shifts at ZT 6, while neither (+)DPAT nor 5-HT affect NPY-induced phase shifts at ZT 10. NPY appears to block (+)DPAT-induced phase shifts by preventing increases in cyclic AMP. These data are the first to demonstrate in vitro interactions between daytime resetting stimuli in the rat, and provide critical insights into mechanisms controlling circadian clock phase.

Phase Shifting of Circadian Rhythms and Depression of Neuronal Activity in the Rat Suprachiasmatic Nucleus by Neuropeptide Y: Mediation by Different Receptor Subtypes

Neuropeptide Y (NPY) has been implicated in the phase shifting of circadian rhythms in the hypothalamic suprachiasmatic nucleus (SCN). Using long-term, multiple-neuron recordings, we examined the direct effects and phase-shifting properties of NPY application in rat SCN slices in vitro (n = 453). Application of NPY and peptide YY to SCN slices at circadian time (CT) 7.5-8.5 produced concentration-dependent, reversible inhibition of cell firing and a subsequent significant phase advance. Several lines of evidence indicated that these two effects of NPY were mediated by different receptors. NPY-induced inhibition and phase shifting had different concentration-response relationships and very different phase-response relationships. NPY-induced phase advances, but not inhibition, were blocked by the GABAA antagonist bicuculline, suggesting that NPY-mediated modulation of GABA may be an underlying mechanism whereby NPY phase shifts the circadian clock. Application of the Y2 receptor agonists NPY 13-36 and (Cys2,8-aminooctanoic acid5,24,D-Cys27)-NPY advanced the peak of the circadian rhythm but did not inhibit cell firing. The Y1 and Y5 agonist [Leu31,Pro34]-NPY evoked a substantial inhibition of discharge but did not generate a phase shift. NPY-induced inhibition was not blocked by the specific Y1 antagonist BIBP-3226; the antagonist also had no effect on the timing of the peak of the circadian rhythm. Application of the Y5 agonist [D-Trp32]-NPY produced only direct neuronal inhibition. These are the first data to indicate that at least two functional populations of NPY receptors exist in the SCN, distinguishable on the basis of pharmacology, each mediating a different physiological response to NPY application.

Circadian Phase Shifts to Neuropeptide YIn Vitro: Cellular Communication and Signal Transduction

Mammalian circadian rhythms originate in the hypothalamic suprachiasmatic nuclei (SCN), from which rhythmic neural activity can be recorded in vitro. Application of neurochemicals can reset this rhythm. Here we determine cellular correlates of the phase-shifting properties of neuropeptide Y (NPY) on the hamster circadian clock in vitro. Drug or control treatments were applied to hypothalamic slices containing the SCN on the first day in vitro. The firing rates of individual cells were sampled on the second day in vitro. Control slices exhibited a peak in firing rate in the middle of the day. Microdrop application of NPY to the SCN phase advanced the time of peak firing rate. This phase-shifting effect of NPY was not altered by block of sodium channels with tetrodotoxin or block of calcium channels with cadmium and nickel, consistent with a direct postsynaptic site of action. Pretreatment with the glutamate receptor antagonists (DL-2-amino-5-phosphonovaleric acid and 6-cyano-7-nitroquinoxaline-2,3-dione disodium) also did not alter phase shifts to NPY. Blocking GABAA receptors with bicuculline (Bic) had effects only at very high (millimolar) doses of Bic, whereas blocking GABAB receptors did not alter effects of NPY. Phase shifts to NPY were blocked by pretreatment with inhibitors of protein kinase C (PKC), suggesting that PKC activation may be necessary for these effects. Bathing the slice in low Ca2+/high Mg2+ can block phase shifts to NPY, possibly via a depolarizing action. A depolarizing high K+ bath can also block NPY phase shifts. The results are consistent with direct action of NPY on pacemaker neurons, mediated through a signal transduction pathway that depends on activation of PKC.

Scattering from stellar acoustic-gravity potentials: II. Phase shifts via the first Born approximation

Using the first Born approximation, properties of the scattering phase shift are investigated for waves that are scattered by a schematic representation of a large-scale “stellar potential,” i.e., one for which the star itself is viewed as the potential inducing a phase shift in an incoming wave. In particular, the phase shift properties are examined as functions of the relative wavenumber (α) and the azimuthal wavenumber ( l), high l-values being of interest in helioseismology.

Parametric correlations of phase shifts and statistics of time delays in quantum chaotic scattering: Crossover between unitary and orthogonal symmetries

We analyze universal statistical properties of phase shifts and time delays for open chaotic systems in the crossover regime of partly broken time-reversal invariance. In particular, we find that the distribution of the time delay shows ${\mathrm{\ensuremath{\tau}}}^{\mathrm{\ensuremath{-}}3\mathrm{/}2}$ behavior for weakly open systems of any symmetry.

走行実験による低速飛行時のヘリコプタロータの縦横連成効果に関する実験的研究

The cross coupling effects of a helicopter rotor in low advance ratio are experimentally studied using the Dynamic Running Test Facility which was built at National Defense Academy recently. Design features and basic performances of the facility are briefly described. Flapping motions of the model rotor blade are precisely measured together with its thrust and torque characteristics at various combinations of test parameters. It is clarified that nonlinear behavior of the cross coupling effects on the advance ratio are attributed to the phase shift properties of blade flapping motions due to nonuniformity of induced velocity distributions on the rotor disc. Usefulness of a dynamic running test is also ascertained for accurate measurements of aerodynamic and dynamic phenomena of a rotorcraft in low speed flight.

X-ray holographic microscopy by means of photoresist recording and atomic-force microscope readout

We have reconstructed in-line (or Gabor) x-ray holograms at 40–50-nm resolution from a complex biological specimen. The holograms were recorded as a relief pattern on photoresist with use of 1.89-nm, soft x rays from the X1A undulator beam line at the National Synchrotron Light Source at Brookhaven National Laboratory. We have improved the resolution and the fidelity and simplified the experiment compared with earlier work by employing a special atomic-force microscope to examine and digitize the holograms. Following digitization the holograms were reconstructed numerically, allowing both the absorptive and phase-shifting properties of the reconstructed object to be mapped. A comparison of the reconstructed images with images obtained from visible light and transmission electron microscopes has been made to confirm the validity of the x-ray holographic technique. The method offers promise as a technique for soft-x-ray microscopy and diffraction tomography of dry and frozen hydrated specimens and for microscopy with pulsed x-ray sources.

Two-photon bistable switching of an optically pumped atomic neon Raman laser.

Two cw Raman lines at 603.0 nm (2${\mathit{p}}_{2}$\ensuremath{\rightarrow}1${\mathit{s}}_{4}$) and 659.9 nm (2${\mathit{p}}_{2}$\ensuremath{\rightarrow}1${\mathit{s}}_{2}$), generated when cw dye-laser radiation is mode matched to the 588.2-nm (1${\mathit{s}}_{5}$\ensuremath{\rightarrow}2${\mathit{p}}_{2}$) transition of Ne I in a commercial He-Ne laser cavity, can both show optically bistable switching simultaneously with the pump beam. A theoretical treatment based on a semiclassical three-state Raman laser model is used to qualitatively reproduce the experimental observations and to identify the mechanisms that produce the experimental signature. Important features of the Raman gain are characterized. These, in combination with the phase-shift properties of the pump and Raman fields, are used to explain the switching behavior. \textcopyright{} 1996 The American Physical Society.

Light Treatment for Sleep Disorders: Consensus Report

In addition to the well-established phase-shifting properties of timed exposure to bright light, some investigators have reported an acute alerting, or activating, effect of bright light exposure. To the extent that bright light interventions for sleep disturbance may cause subjective and/or central nervous system activation, such a property may adversely affect the efficacy of treatment. Data obtained from patient samples and from healthy subjects generally support the notion that exposure to bright light may be associated with enhanced subjective alertness, and there is limited evidence of objective changes (EEG, skin conductance levels) that are consistent with true physiological arousal. Such activation appears to be quite transient, and there is little evidence to suggest that bright light-induced activation interferes with subsequent sleep onset. Some depressed patients, however, have experienced insomnia and hypomanic activation following bright-light exposure.

Single Electron Digital Phase Modulator

It is well known that the AC voltage gain of a symmetric single electron transistor amplifier has a 180° phase shift whenever the equilibrium charge in the Coulomb island changes by e/2. Using this interesting phase shift property, we propose a single electron digital phase modulation scheme. We show that there is a trade-off between the intrinsic operating speed and the voltage gain of the modulator. We show that even though the two tunnel junctions of the modulator are not matched, there is no distortion in the output signal.

Multilayer transmission polarizers in the soft X-ray region

The phaseshifting properties of multilayer transmission filters in the XUV region are examined. The possibility of changing the polarization state of electromagnetic radiation from linear to circular by means of such devices is carefully considered using a realistic model and proper optimization criteria. The performances of different transmission multilayers in some energy windows are presented.

UV Laser Deposition of Thin Films at 248 NM for Phase Shifting Mask Repair

AbstractLaser-induced deposition of controlled quality silicon dioxide and thin metallic films was investigated at 248 nm for phase shifting mask (PSM) repair. SiOx (x-1.5-2) films were deposited from single precursors, such as triethoxyvinylsilane (TEVS), tetraallyloxysilane (TAOS), di-t-butoxy-diacetooxysilane (TBSA) with no oxidizing coreactant. A deposition rate of 0.25 A/pulse was possible at room temperature, with excellent optical properties (n-1.47, k-0.05). Metallic films were deposited from tungsten, gold, molybdenum and chromium compounds. The results showed that the optical transmission and phase-shifting properties of the deposits can be matched well to the films commonly used in phase shifting masks.

Phase verification of power test systems

One aspect of the problem of the measurement of the losses in low power factor devices such as power transformers or power reactors is the verification of the phase angle properties of both the complete system and its various component parts. The use of a digital phase standard as a solution to this and other phase measurement problems is proposed. When a phase standard is synchronized in both phase and frequency, then its precise digital phase shift properties, used in conjunction with passive phase bridges, allow the design of high-power, high-accuracy (better than 0.001), phase verification schemes. Methods using this approach are outlined that use commercially available, easily transportable equipment to provide rapid and accurate phase angle measurements for almost all possible combinations of current and voltage. >

Properties of the PHase-Alternating Phase-Shift (PHAPS) multiple spin-echo protocol in MRI: A study of the effects of imperfect RF pulses

The effects of imperfect radiofrequency (FR) pulses on the echo amplitudes from the Carr-Purcell (CP), Carr-Purcell-Meiboom-Gill (CPMG), and the PHase-Alternating Phase-Shift (PHAPS; combination of CP and CPMG) multiple spin-echo schemes were studied. Properties of the PHAPS scheme for transverse relaxation time measurements was emphasized. Numerical simulations on non-relaxing spin systems were performed to assess the properties of selective (damped sinc shaped) and nonselective refocusing pulses in terms of effective spatial selectivity and generation of secondary echo signal. Analytical solutions of the Bloch equations were applied to study the generation and propagation of stimulated echo signal caused by nonideal 180° phase reversals, and the results were used to analyse the numerical simulations in terms of primary and stimulated echo components. Finally, the simulated echo train patterns from the different MSE schemes were compared with MR imaging measurements. It was found that the underestimation of T 2 values by the PHAPS protocol with selective refocusing pulses is mainly an effect of an “artificial” echo amplitude decay in the CP scheme, while the CPMG scheme produces a typical even-odd echo pattern (different from corresponding echo patterns in conventional high resolution NMR). Both effects are related to the flip angle error and phase dispersion along the slice selection direction from selective RF pulses, and are not significantly influenced by stimulated echo interference for nonrelaxing spin systems. However, the presence of stimulated echoes at the time of the primary echoes implies a dependence on T 1 of the PHAPS echo amplitudes. In the CPMG protocol, different gradient schemes have been implemented to defocus stimulated echoes. However, the results indicate that there exists stimulated components that will not be affected by such gradients, and that the optimization of the RF refocusing pulses then remain the main objective.

The dim light melatonin onset as a marker for circadian phase position.

Masking is known to affect a variety of circadian rhythms, making it difficult to use them as reliable markers of circadian phase position. Melatonin may be unique in that it appears to be masked only by (bright) light. Sleep and activity do not appear to influence the melatonin rhythm. By measuring the onset of melatonin production, a clearly demarcated event, we can reliably assess circadian phase position, provided blood is sampled under dim light (the dim light melatonin onset, or DLMO). The DLMO has been useful in assessing the phase-shifting properties of bright light and in phase typing patients with chronobiologic disorders, such as winter depression.

Slow-wave microcoplanar variable phase shifter

The phase-shifting properties of a slow-wave microcoplanar structure are studied by means of a rigorous theoretical approach and the propagation losses are calculated. The Green function, which is used for the two-dimensional determination of the depletion layer profile, satisfies the real boundary conditions of the physical structure. The results obtained for the structure's electrical length are compared with the corresponding experimental data and a good agreement is obtained, in particular for zero-bias conditions.

Coplanar waveguide and slot line on magnetic substrates: analysis and experiment

A full-wave analysis is presented for coplanar waveguide (CPW) and slotline phase shifters on magnetic substrates. The analysis is based on a multilayer Green's function which is formulated using a transmission matrix approach. This approach is modified so that its computational efficiency is increased by deriving the transmission matrices for dielectric and ferrite slabs in a closed form. The Green's function is then applied to the full-wave analysis of a slotline and CPW on infinite-width substrates. Several different multilayered configurations are investigated with respect to their nonreciprocal phase-shift properties. Perfectly conducting sidewalls are then added to the analysis and the resulting configuration is used to study the effect of various CPW parameters on differential phase shift. An experimental structure built on the surface of rectangular ferrite toroid is described and its differential phase analysis compared to measurements. Calculated and measured results are in good agreement. >